194 results on '"J. R. Pierce"'
Search Results
2. Improved Limit on Tensor Currents in the Weak Interaction from Li8 β Decay
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M. T. Burkey, G. Savard, A. T. Gallant, N. D. Scielzo, J. A. Clark, T. Y. Hirsh, L. Varriano, G. H. Sargsyan, K. D. Launey, M. Brodeur, D. P. Burdette, E. Heckmaier, K. Joerres, J. W. Klimes, K. Kolos, A. Laminack, K. G. Leach, A. F. Levand, B. Longfellow, B. Maaß, S. T. Marley, G. E. Morgan, P. Mueller, R. Orford, S. W. Padgett, A. Pérez Galván, J. R. Pierce, D. Ray, R. Segel, K. Siegl, K. S. Sharma, and B. S. Wang
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General Physics and Astronomy - Published
- 2022
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3. The potential role of organics in new particle formation and initial growth in the remote tropical upper troposphere
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A. Kupc, C. J. Williamson, A. L. Hodshire, J. Kazil, E. Ray, T. P. Bui, M. Dollner, K. D. Froyd, K. McKain, A. Rollins, G. P. Schill, A. Thames, B. B. Weinzierl, J. R. Pierce, and C. A. Brock
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lcsh:Chemistry ,lcsh:QD1-999 ,lcsh:Physics ,lcsh:QC1-999 - Abstract
Global observations and model studies indicate that new particle formation (NPF) in the upper troposphere (UT) and subsequent particles supply 40 %–60 % of cloud condensation nuclei (CCN) in the lower troposphere, thus affecting the Earth's radiative budget. There are several plausible nucleation mechanisms and precursor species in this atmospheric region, which, in the absence of observational constraints, lead to uncertainties in modeled aerosols. In particular, the type of nucleation mechanism and concentrations of nucleation precursors, in part, determine the spatial distribution of new particles and resulting spatial distribution of CCN from this source. Although substantial advances in understanding NPF have been made in recent years, NPF processes in the UT in pristine marine regions are still poorly understood and are inadequately represented in global models. Here, we evaluate commonly used and state-of-the-art NPF schemes in a Lagrangian box model to assess which schemes and precursor concentrations best reproduce detailed in situ observations. Using measurements of aerosol size distributions (0.003 < Dp < 4.8 µm) in the remote marine troposphere between ∼0.18 and 13 km altitude obtained during the NASA Atmospheric Tomography (ATom) mission, we show that high concentrations of newly formed particles in the tropical UT over both the Atlantic and Pacific oceans are associated with outflow regions of deep convective clouds. We focus analysis on observations over the remote Pacific Ocean, which is a region less perturbed by continental emissions than the Atlantic. Comparing aerosol size distribution measurements over the remote Pacific with box model simulations for 32 cases shows that none of the NPF schemes most commonly used in global models, including binary nucleation of sulfuric acid and water (neutral and ion-assisted) and ternary involving sulfuric acid, water, and ammonia, are consistent with observations, regardless of precursor concentrations. Through sensitivity studies, we find that the nucleation scheme among those tested that is able to explain most consistently (21 of 32 cases) the observed size distributions is that of Riccobono et al. (2014), which involves both organic species and sulfuric acid. The method of Dunne et al. (2016), involving charged sulfuric acid–water–ammonia nucleation, when coupled with organic growth of the nucleated particles, was most consistent with the observations for 5 of 32 cases. Similarly, the neutral sulfuric acid–water–ammonia method of Napari (2002), when scaled with a tuning factor and with organic growth added, was most consistent for 6 of 32 cases. We find that to best reproduce both nucleation and growth rates, the mixing ratios of gas-phase organic precursors generally need to be at least twice that of SO2, a proxy for dimethyl sulfide (DMS). Unfortunately, we have no information on the nature of oxidized organic species that participated in NPF in this region. Global models rarely include organic-driven nucleation and growth pathways in UT conditions where globally significant NPF takes place, which may result in poor estimates of NPF and CCN abundance and contribute to uncertainties in aerosol–cloud–radiation effects. Furthermore, our results indicate that the organic aerosol precursor vapors may be important in the tropical UT above marine regions, a finding that should guide future observational efforts.
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- 2020
4. Vertical profiles of light absorption and scattering associated with black carbon particle fractions in the springtime Arctic above 79° N
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W. R. Leaitch, J. K. Kodros, M. D. Willis, S. Hanna, H. Schulz, E. Andrews, H. Bozem, J. Burkart, P. Hoor, F. Kolonjari, J. A. Ogren, S. Sharma, M. Si, K. von Salzen, A. K. Bertram, A. Herber, J. P. D. Abbatt, and J. R. Pierce
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Microphysics ,Single-scattering albedo ,010501 environmental sciences ,Radiative forcing ,Atmospheric sciences ,01 natural sciences ,lcsh:QC1-999 ,Light scattering ,Aerosol ,lcsh:Chemistry ,Troposphere ,Atmosphere ,lcsh:QD1-999 ,Arctic ,13. Climate action ,lcsh:Physics ,0105 earth and related environmental sciences - Abstract
Despite the potential importance of black carbon (BC) for radiative forcing of the Arctic atmosphere, vertically resolved measurements of the particle light scattering coefficient (σsp) and light absorption coefficient (σap) in the springtime Arctic atmosphere are infrequent, especially measurements at latitudes at or above 80∘ N. Here, relationships among vertically distributed aerosol optical properties (σap, σsp and single scattering albedo or SSA), particle microphysics and particle chemistry are examined for a region of the Canadian archipelago between 79.9 and 83.4∘ N from near the surface to 500 hPa. Airborne data collected during April 2015 are combined with ground-based observations from the observatory at Alert, Nunavut and simulations from the Goddard Earth Observing System (GEOS) model, GEOS-Chem, coupled with the TwO-Moment Aerosol Sectional (TOMAS) model (collectively GEOS-Chem–TOMAS; Kodros et al., 2018) to further our knowledge of the effects of BC on light absorption in the Arctic troposphere. The results are constrained for σsp less than 15 Mm−1, which represent 98 % of the observed σsp, because the single scattering albedo (SSA) has a tendency to be lower at lower σsp, resulting in a larger relative contribution to Arctic warming. At 18.4 m2 g−1, the average BC mass absorption coefficient (MAC) from the combined airborne and Alert observations is substantially higher than the two averaged modelled MAC values (13.6 and 9.1 m2 g−1) for two different internal mixing assumptions, the latter of which is based on previous observations. The higher observed MAC value may be explained by an underestimation of BC, the presence of small amounts of dust and/or possible differences in BC microphysics and morphologies between the observations and model. In comparing the observations and simulations, we present σap and SSA, as measured, and σap∕2 and the corresponding SSA to encompass the lower modelled MAC that is more consistent with accepted MAC values. Median values of the measured σap, rBC and the organic component of particles all increase by a factor of 1.8±0.1, going from near-surface to 750 hPa, and values higher than the surface persist to 600 hPa. Modelled BC, organics and σap agree with the near-surface measurements but do not reproduce the higher values observed between 900 and 600 hPa. The differences between modelled and observed optical properties follow the same trend as the differences between the modelled and observed concentrations of the carbonaceous components (black and organic). Model-observation discrepancies may be mostly due to the modelled ejection of biomass burning particles only into the boundary layer at the sources. For the assumption of the observed MAC value, the SSA range between 0.88 and 0.94, which is significantly lower than other recent estimates for the Arctic, in part reflecting the constraint of σsp Mm−1. The large uncertainties in measuring optical properties and BC, and the large differences between measured and modelled values here and in the literature, argue for improved measurements of BC and light absorption by BC and more vertical profiles of aerosol chemistry, microphysics and other optical properties in the Arctic.
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- 2020
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5. Exact solutions for the electromagnetic fields of a flying focus
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D. Ramsey, A. Di Piazza, M. Formanek, P. Franke, D. H. Froula, B. Malaca, W. B. Mori, J. R. Pierce, T. T. Simpson, J. Vieira, M. Vranic, K. Weichman, and J. P. Palastro
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Research group A. Di Piazza – Division C. H. Keitel ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Physics - Optics ,Optics (physics.optics) - Abstract
The intensity peak of a "flying focus" travels at a programmable velocityover many Rayleigh ranges while maintaining a near-constant profile. Assessingthe extent to which these features can enhance laser-based applicationsrequires an accurate description of the electromagnetic fields. Here we presentexact analytical solutions to Maxwell's equations for the electromagneticfields of a constant-velocity flying focus, generalized for arbitrarypolarization and orbital angular momentum. The approach combines the complexsource-point method, which transforms multipole solutions into beam-likesolutions, with the Lorentz invariance of Maxwell's equations. Propagating thefields backward in space reveals the space-time profile that an opticalassembly must produce to realize these fields in the laboratory. Comparisonswith simpler paraxial solutions provide conditions for their reliable use whenmodeling a flying focus.
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- 2022
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6. A low-cost monitor for simultaneous measurement of fine particulate matter and aerosol optical depth – Part 1: Specifications and testing
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E. A. Wendt, C. W. Quinn, D. D. Miller-Lionberg, J. Tryner, C. L'Orange, B. Ford, A. P. Yalin, J. R. Pierce, S. Jathar, and J. Volckens
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,lcsh:TA715-787 ,Fine particulate ,lcsh:Earthwork. Foundations ,Air pollution ,Photometer ,010501 environmental sciences ,medicine.disease_cause ,01 natural sciences ,lcsh:Environmental engineering ,Photodiode ,law.invention ,Aerosol ,AERONET ,law ,medicine ,Environmental science ,Satellite ,lcsh:TA170-171 ,Optical depth ,0105 earth and related environmental sciences ,Remote sensing - Abstract
Globally, fine particulate matter (PM2.5) air pollution is a leading contributor to death, disease, and environmental degradation. Satellite-based measurements of aerosol optical depth (AOD) are used to estimate PM2.5 concentrations across the world, but the relationship between satellite-estimated AOD and ground-level PM2.5 is uncertain. Sun photometers measure AOD from the Earth's surface and are often used to improve satellite data; however, reference-grade photometers and PM2.5 monitors are expensive and rarely co-located. This work presents the development and validation of the aerosol mass and optical depth (AMOD) sampler, an inexpensive and compact device that simultaneously measures PM2.5 mass and AOD. The AMOD utilizes a low-cost light-scattering sensor in combination with a gravimetric filter measurement to quantify ground-level PM2.5. Aerosol optical depth is measured using optically filtered photodiodes at four discrete wavelengths. Field validation studies revealed agreement within 10 % for AOD values measured between co-located AMOD and AErosol RObotics NETwork (AERONET) monitors and for PM2.5 mass measured between co-located AMOD and EPA Federal Equivalent Method (FEM) monitors. These results demonstrate that the AMOD can quantify AOD and PM2.5 accurately at a fraction of the cost of existing reference monitors.
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- 2019
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7. Overview paper: New insights into aerosol and climate in the Arctic
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J. P. D. Abbatt, W. R. Leaitch, A. A. Aliabadi, A. K. Bertram, J.-P. Blanchet, A. Boivin-Rioux, H. Bozem, J. Burkart, R. Y. W. Chang, J. Charette, J. P. Chaubey, R. J. Christensen, A. Cirisan, D. B. Collins, B. Croft, J. Dionne, G. J. Evans, C. G. Fletcher, M. Galí, R. Ghahremaninezhad, E. Girard, W. Gong, M. Gosselin, M. Gourdal, S. J. Hanna, H. Hayashida, A. B. Herber, S. Hesaraki, P. Hoor, L. Huang, R. Hussherr, V. E. Irish, S. A. Keita, J. K. Kodros, F. Köllner, F. Kolonjari, D. Kunkel, L. A. Ladino, K. Law, M. Levasseur, Q. Libois, J. Liggio, M. Lizotte, K. M. Macdonald, R. Mahmood, R. V. Martin, R. H. Mason, L. A. Miller, A. Moravek, E. Mortenson, E. L. Mungall, J. G. Murphy, M. Namazi, A.-L. Norman, N. T. O'Neill, J. R. Pierce, L. M. Russell, J. Schneider, H. Schulz, S. Sharma, M. Si, R. M. Staebler, N. S. Steiner, J. L. Thomas, K. von Salzen, J. J. B. Wentzell, M. D. Willis, G. R. Wentworth, J.-W. Xu, J. D. Yakobi-Hancock, Department of Chemistry [University of Toronto], University of Toronto, Environment and Climate Change Canada, School of Engineering [Guelph], University of Guelph, Department of Chemistry [Vancouver] (UBC Chemistry), University of British Columbia (UBC), Département des sciences de la terre et de l'atmosphère [Montréal] (SCTA), Université du Québec à Montréal = University of Québec in Montréal (UQAM), Institut des Sciences de la MER de Rimouski (ISMER), Université du Québec à Rimouski (UQAR), Institute for Atmospheric Physics [Mainz] (IPA), Johannes Gutenberg - Universität Mainz (JGU), Aerosol Physics and Environmental Physics [Vienna], University of Vienna [Vienna], Department of Physics and Atmospheric Science [Halifax], Dalhousie University [Halifax], Department of Chemistry [Lewisburg], Bucknell University, Department of Chemical Engineering and Applied Chemistry (CHEM ENG), Department of Geography and Environmental Management [Waterloo], University of Waterloo [Waterloo], Department of Biology [Québec], Université Laval [Québec] (ULaval), Departement de Biologie [Québec], School of Earth and Ocean Sciences [Victoria] (SEOS), University of Victoria [Canada] (UVIC), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Centre d'Applications et de Recherches en TELédétection [Sherbrooke] (CARTEL), Département de géomatique appliquée [Sherbrooke] (UdeS), Université de Sherbrooke (UdeS)-Université de Sherbrooke (UdeS), Department of Atmospheric Science [Fort Collins], Colorado State University [Fort Collins] (CSU), Particle Chemistry Department [Mainz], Max Planck Institute for Chemistry (MPIC), Max-Planck-Gesellschaft-Max-Planck-Gesellschaft, Centro de Ciencias de la Atmosfera [Mexico], Universidad Nacional Autónoma de México (UNAM), TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Air Quality Processes Research Section, Canadian Centre for Climate Modelling and Analysis (CCCma), Institute of Ocean Sciences [Sidney] (IOS), Fisheries and Oceans Canada (DFO), Department of Mathematics [Isfahan], University of Isfahan, Department of Physics and Astronomy [Calgary], University of Calgary, Scripps Institution of Oceanography (SIO), University of California [San Diego] (UC San Diego), University of California-University of California, Institut des Géosciences de l’Environnement (IGE), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut de Recherche pour le Développement (IRD)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Lawrence Berkeley National Laboratory [Berkeley] (LBNL), Alberta Environment and Parks (AEP), National Research Council of Canada (NRC), Johannes Gutenberg - Universität Mainz = Johannes Gutenberg University (JGU), Universidad Nacional Autónoma de México = National Autonomous University of Mexico (UNAM), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Scripps Institution of Oceanography (SIO - UC San Diego), University of California (UC)-University of California (UC), and Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])
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[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] ,Arctic haze ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Global warming ,Climate change ,010501 environmental sciences ,Mineral dust ,Atmospheric sciences ,01 natural sciences ,Sea surface microlayer ,lcsh:QC1-999 ,Atmospheric Sciences ,Aerosol ,lcsh:Chemistry ,Climate Action ,Deposition (aerosol physics) ,lcsh:QD1-999 ,Arctic ,[SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology ,13. Climate action ,Meteorology & Atmospheric Sciences ,lcsh:Physics ,Astronomical and Space Sciences ,0105 earth and related environmental sciences - Abstract
Motivated by the need to predict how the Arctic atmosphere will change in a warming world, this article summarizes recent advances made by the research consortium NETCARE (Network on Climate and Aerosols: Addressing Key Uncertainties in Remote Canadian Environments) that contribute to our fundamental understanding of Arctic aerosol particles as they relate to climate forcing. The overall goal of NETCARE research has been to use an interdisciplinary approach encompassing extensive field observations and a range of chemical transport, earth system, and biogeochemical models. Several major findings and advances have emerged from NETCARE since its formation in 2013. (1) Unexpectedly high summertime dimethyl sulfide (DMS) levels were identified in ocean water (up to 75 nM) and the overlying atmosphere (up to 1 ppbv) in the Canadian Arctic Archipelago (CAA). Furthermore, melt ponds, which are widely prevalent, were identified as an important DMS source (with DMS concentrations of up to 6 nM and a potential contribution to atmospheric DMS of 20 % in the study area). (2) Evidence of widespread particle nucleation and growth in the marine boundary layer was found in the CAA in the summertime, with these events observed on 41 % of days in a 2016 cruise. As well, at Alert, Nunavut, particles that are newly formed and grown under conditions of minimal anthropogenic influence during the months of July and August are estimated to contribute 20 % to 80 % of the 30–50 nm particle number density. DMS-oxidation-driven nucleation is facilitated by the presence of atmospheric ammonia arising from seabird-colony emissions, and potentially also from coastal regions, tundra, and biomass burning. Via accumulation of secondary organic aerosol (SOA), a significant fraction of the new particles grow to sizes that are active in cloud droplet formation. Although the gaseous precursors to Arctic marine SOA remain poorly defined, the measured levels of common continental SOA precursors (isoprene and monoterpenes) were low, whereas elevated mixing ratios of oxygenated volatile organic compounds (OVOCs) were inferred to arise via processes involving the sea surface microlayer. (3) The variability in the vertical distribution of black carbon (BC) under both springtime Arctic haze and more pristine summertime aerosol conditions was observed. Measured particle size distributions and mixing states were used to constrain, for the first time, calculations of aerosol–climate interactions under Arctic conditions. Aircraft- and ground-based measurements were used to better establish the BC source regions that supply the Arctic via long-range transport mechanisms, with evidence for a dominant springtime contribution from eastern and southern Asia to the middle troposphere, and a major contribution from northern Asia to the surface. (4) Measurements of ice nucleating particles (INPs) in the Arctic indicate that a major source of these particles is mineral dust, likely derived from local sources in the summer and long-range transport in the spring. In addition, INPs are abundant in the sea surface microlayer in the Arctic, and possibly play a role in ice nucleation in the atmosphere when mineral dust concentrations are low. (5) Amongst multiple aerosol components, BC was observed to have the smallest effective deposition velocities to high Arctic snow (0.03 cm s−1).
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- 2019
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8. A low-cost monitor for simultaneous measurement of fine particulate matter and aerosol optical depth – Part 3: Automation and design improvements
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E. A. Wendt, C. Quinn, C. L'Orange, D. D. Miller-Lionberg, B. Ford, J. R. Pierce, J. Mehaffy, M. Cheeseman, S. H. Jathar, D. H. Hagan, Z. Rosen, M. Long, and J. Volckens
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Atmospheric Science ,TA715-787 ,Sampling (statistics) ,Environmental engineering ,Ranging ,TA170-171 ,Stability (probability) ,Aerosol ,AERONET ,Earthwork. Foundations ,Robustness (computer science) ,Calibration ,Environmental science ,Optical depth ,Remote sensing - Abstract
Atmospheric particulate matter smaller than 2.5 µm in diameter (PM2.5) has a negative impact on public health, the environment, and Earth's climate. Consequently, a need exists for accurate, distributed measurements of surface-level PM2.5 concentrations at a global scale. Existing PM2.5 measurement infrastructure provides broad PM2.5 sampling coverage but does not adequately characterize community-level air pollution at high temporal resolution. This motivates the development of low-cost sensors which can be more practically deployed in spatial and temporal configurations currently lacking proper characterization. Wendt et al. (2019) described the development and validation of a first-generation device for low-cost measurement of AOD and PM2.5: the Aerosol Mass and Optical Depth (AMODv1) sampler. Ford et al. (2019) describe a citizen-science field deployment of the AMODv1 device. In this paper, we present an updated version of the AMOD, known as AMODv2, featuring design improvements and extended validation to address the limitations of the AMODv1 work. The AMODv2 measures AOD and PM2.5 at 20 min time intervals. The sampler includes a motorized Sun tracking system alongside a set of four optically filtered photodiodes for semicontinuous, multiwavelength (current version at 440, 500, 675, and 870 nm) AOD sampling. Also included are a Plantower PMS5003 sensor for time-resolved optical PM2.5 measurements and a pump/cyclone system for time-integrated gravimetric filter measurements of particle mass and composition. AMODv2 samples are configured using a smartphone application, and sample data are made available via data streaming to a companion website (https://csu-ceams.com/, last access: 16 July 2021). We present the results of a 9 d AOD validation campaign where AMODv2 units were co-located with an AERONET (Aerosol Robotics Network) instrument as the reference method at AOD levels ranging from 0.02 ± 0.01 to 1.59 ± 0.01. We observed close agreement between AMODv2s and the reference instrument with mean absolute errors of 0.04, 0.06, 0.03, and 0.03 AOD units at 440, 500, 675, and 870 nm, respectively. We derived empirical relationships relating the reference AOD level to AMODv2 instrument error and found that the mean absolute error in the AMODv2 deviated by less than 0.01 AOD units between clear days and elevated-AOD days and across all wavelengths. We identified bias from individual units, particularly due to calibration drift, as the primary source of error between AMODv2s and reference units. In a test of 15-month calibration stability performed on 16 AMOD units, we observed median changes to calibration constant values of −7.14 %, −9.64 %, −0.75 %, and −2.80 % at 440, 500, 675, and 870 nm, respectively. We propose annual recalibration to mitigate potential errors from calibration drift. We conducted a trial deployment to assess the reliability and mechanical robustness of AMODv2 units. We found that 75 % of attempted samples were successfully completed in rooftop laboratory testing. We identify several failure modes in the laboratory testing and describe design changes that we have since implemented to reduce failures. We demonstrate that the AMODv2 is an accurate, stable, and low-cost platform for air pollution measurement. We describe how the AMODv2 can be implemented in spatial citizen-science networks where reference-grade sensors are economically impractical and low-cost sensors lack accuracy and stability.
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- 2021
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9. Factors controlling marine aerosol size distributions and their climate effects over the northwest Atlantic Ocean region
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B. Croft, R. V. Martin, R. H. Moore, L. D. Ziemba, E. C. Crosbie, H. Liu, L. M. Russell, G. Saliba, A. Wisthaler, M. Müller, A. Schiller, M. Galí, R. Y.-W. Chang, E. E. McDuffie, K. R. Bilsback, J. R. Pierce, and Barcelona Supercomputing Center
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Marine aerosol ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,Atmospheric physics ,Climate ,GEOS-Chem model ,Particle (ecology) ,010501 environmental sciences ,Atmospheric sciences ,01 natural sciences ,lcsh:Chemistry ,Troposphere ,Earth's climate system ,chemistry.chemical_compound ,Radiative transfer ,Marine ecosystem ,0105 earth and related environmental sciences ,Aerosols -- Aspectes ambientals ,Enginyeria agroalimentària::Ciències de la terra i de la vida::Climatologia i meteorologia [Àrees temàtiques de la UPC] ,TwO-Moment Aerosol Sectional (TOMAS) ,Albedo ,Sea surface microlayer ,lcsh:QC1-999 ,Aerosol ,Boundary layer ,lcsh:QD1-999 ,chemistry ,Environmental science ,Dimethyl sulfide ,lcsh:Physics - Abstract
Aerosols over Earth's remote and spatially extensive ocean surfaces have important influences on planetary climate. However, these aerosols and their effects remain poorly understood, in part due to the remoteness and limited observations over these regions. In this study, we seek to understand factors that shape marine aerosol size distributions and composition in the northwest Atlantic Ocean region. We use the GEOS-Chem model with the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm model to interpret measurements collected from ship and aircraft during the four seasonal campaigns of the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES) conducted between 2015 and 2018. Observations from the NAAMES campaigns show enhancements in the campaign-median number of aerosols with diameters larger than 3 nm in the lower troposphere (below 6 km), most pronounced during the phytoplankton bloom maxima (May/June) below 2 km in the free troposphere. Our simulations, combined with NAAMES ship and aircraft measurements, suggest several key factors that contribute to aerosol number and size in the northwest Atlantic lower troposphere, with significant regional-mean (40–60∘ N and 20–50∘ W) cloud-albedo aerosol indirect effect (AIE) and direct radiative effect (DRE) processes during the phytoplankton bloom. These key factors and their associated simulated radiative effects in the region include the following: (1) particle formation near and above the marine boundary layer (MBL) top (AIE: −3.37 W m−2, DRE: −0.62 W m−2); (2) particle growth due to marine secondary organic aerosol (MSOA) as the nascent particles subside into the MBL, enabling them to become cloud-condensation-nuclei-sized particles (AIE: −2.27 W m−2, DRE: −0.10 W m−2); (3) particle formation and growth due to the products of dimethyl sulfide, above and within the MBL (−1.29 W m−2, DRE: −0.06 W m−2); (4) ship emissions (AIE: −0.62 W m−2, DRE: −0.05 W m−2); and (5) primary sea spray emissions (AIE: +0.04 W m−2, DRE: −0.79 W m−2). Our results suggest that a synergy of particle formation in the lower troposphere (particularly near and above the MBL top) and growth by MSOA contributes strongly to cloud-condensation-nuclei-sized particles with significant regional radiative effects in the northwest Atlantic. To gain confidence in radiative effect magnitudes, future work is needed to understand (1) the sources and temperature dependence of condensable marine vapors forming MSOA, (2) primary sea spray emissions, and (3) the species that can form new particles in the lower troposphere and grow these particles as they descend into the marine boundary layer.
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- 2021
10. Ultra-Bright Electron Bunch Injection in a Plasma Wakefield Driven by a Superluminal Flying Focus Electron Beam
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F. Li, T. N. Dalichaouch, J. R. Pierce, X. Xu, F. S. Tsung, W. Lu, C. Joshi, and W. B. Mori
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Plasma Physics (physics.plasm-ph) ,Accelerator Physics (physics.acc-ph) ,General Physics and Astronomy ,Physics::Accelerator Physics ,FOS: Physical sciences ,Physics - Accelerator Physics ,Physics - Plasma Physics - Abstract
We propose a new method for self-injection of high-quality electron bunches in the plasma wakefield structure in the blowout regime utilizing a "flying focus" produced by a drive beam with an energy chirp. In a flying focus the speed of the density centroid of the drive bunch can be superluminal or subluminal by utilizing the chromatic dependence of the focusing optics. We first derive the focal velocity and the characteristic length of the focal spot in terms of the focal length and an energy chirp. We then demonstrate using multidimensional particle-in-cell simulations that a wake driven by a superluminally propagating flying focus of an electron beam can generate GeV-level electron bunches with ultralow normalized slice emittance ($\sim$30 nm rad), high current ($\sim$ 17 kA), low slice energy-spread ($\sim$0.1%) and therefore high normalized brightness ($>10^{19}$ A/rad$^2$/m$^2$) in a plasma of density $\sim10^{19}$ cm$^{-3}$. The injection process is highly controllable and tunable by changing the focal velocity and shaping the drive beam current. Near-term experiments at FACET II where the capabilities to generate tens of kA
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- 2021
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11. An evaluation of global organic aerosol schemes using airborne observations
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S. J. Pai, C. L. Heald, J. R. Pierce, S. C. Farina, E. A. Marais, J. L. Jimenez, P. Campuzano-Jost, B. A. Nault, A. M. Middlebrook, H. Coe, J. E. Shilling, R. Bahreini, J. H. Dingle, and K. Vu
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Chemical transport model ,0207 environmental engineering ,Magnitude (mathematics) ,02 engineering and technology ,010501 environmental sciences ,Atmospheric sciences ,01 natural sciences ,lcsh:QC1-999 ,Aerosol ,lcsh:Chemistry ,Troposphere ,chemistry.chemical_compound ,Deposition (aerosol physics) ,lcsh:QD1-999 ,chemistry ,13. Climate action ,Environmental science ,Sulfate aerosol ,Volatility (finance) ,020701 environmental engineering ,Scale (map) ,lcsh:Physics ,0105 earth and related environmental sciences - Abstract
Chemical transport models have historically struggled to accurately simulate the magnitude and variability of observed organic aerosol (OA), with previous studies demonstrating that models significantly underestimate observed concentrations in the troposphere. In this study, we explore two different model OA schemes within the standard GEOS-Chem chemical transport model and evaluate the simulations against a suite of 15 globally distributed airborne campaigns from 2008 to 2017, primarily in the spring and summer seasons. These include the ATom, KORUS-AQ, GoAmazon, FRAPPE, SEAC4RS, SENEX, DC3, CalNex, OP3, EUCAARI, ARCTAS and ARCPAC campaigns and provide broad coverage over a diverse set of atmospheric composition regimes – anthropogenic, biogenic, pyrogenic and remote. The schemes include significant differences in their treatment of the primary and secondary components of OA – a “simple scheme” that models primary OA (POA) as non-volatile and takes a fixed-yield approach to secondary OA (SOA) formation and a “complex scheme” that simulates POA as semi-volatile and uses a more sophisticated volatility basis set approach for non-isoprene SOA, with an explicit aqueous uptake mechanism to model isoprene SOA. Despite these substantial differences, both the simple and complex schemes perform comparably across the aggregate dataset in their ability to capture the observed variability (with an R2 of 0.41 and 0.44, respectively). The simple scheme displays greater skill in minimizing the overall model bias (with a normalized mean bias of 0.04 compared to 0.30 for the complex scheme). Across both schemes, the model skill in reproducing observed OA is superior to previous model evaluations and approaches the fidelity of the sulfate simulation within the GEOS-Chem model. However, there are significant differences in model performance across different chemical source regimes, classified here into seven categories. Higher-resolution nested regional simulations indicate that model resolution is an important factor in capturing variability in highly localized campaigns, while also demonstrating the importance of well-constrained emissions inventories and local meteorology, particularly over Asia. Our analysis suggests that a semi-volatile treatment of POA is superior to a non-volatile treatment. It is also likely that the complex scheme parameterization overestimates biogenic SOA at the global scale. While this study identifies factors within the SOA schemes that likely contribute to OA model bias (such as a strong dependency of the bias in the complex scheme on relative humidity and sulfate concentrations), comparisons with the skill of the sulfate aerosol scheme in GEOS-Chem indicate the importance of other drivers of bias, such as emissions, transport and deposition, that are exogenous to the OA chemical scheme.
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- 2020
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12. Constraining nucleation, condensation, and chemistry in oxidation flow reactors using size-distribution measurements and aerosol microphysical modeling
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A. L. Hodshire, B. B. Palm, M. L. Alexander, Q. Bian, P. Campuzano-Jost, E. S. Cross, D. A. Day, S. S. de Sá, A. B. Guenther, A. Hansel, J. F. Hunter, W. Jud, T. Karl, S. Kim, J. H. Kroll, J.-H. Park, Z. Peng, R. Seco, J. N. Smith, J. L. Jimenez, J. R. Pierce, Massachusetts Institute of Technology. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology. Department of Materials Science and Engineering, Massachusetts Institute of Technology. Department of Mechanical Engineering, Cross, Eben, Hunter, James Freeman, Kroll, Jesse, and Jimenez, Jose L.
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Aging ,Atmospheric Science ,genetic structures ,010504 meteorology & atmospheric sciences ,Nucleation ,Thermodynamics ,010501 environmental sciences ,7. Clean energy ,01 natural sciences ,Atmospheric Sciences ,lcsh:Chemistry ,chemistry.chemical_compound ,Reaction rate constant ,Meteorology & Atmospheric Sciences ,Diffusion (business) ,Isoprene ,0105 earth and related environmental sciences ,Microphysics ,Chemistry ,Condensation ,lcsh:QC1-999 ,Aerosol ,Climate Action ,lcsh:QD1-999 ,13. Climate action ,Particle ,lcsh:Physics ,Astronomical and Space Sciences - Abstract
Oxidation flow reactors (OFRs) allow the concentration of a given atmospheric oxidant to be increased beyond ambient levels in order to study secondary organic aerosol (SOA) formation and aging over varying periods of equivalent aging by that oxidant. Previous studies have used these reactors to determine the bulk OA mass and chemical evolution. To our knowledge, no OFR study has focused on the interpretation of the evolving aerosol size distributions. In this study, we use size-distribution measurements of the OFR and an aerosol microphysics model to learn about size-dependent processes in the OFR. Specifically, we use OFR exposures between 0.09 and 0.9 equivalent days of OH aging from the 2011 BEACHON-RoMBAS and GoAmazon2014/5 field campaigns. We use simulations in the TOMAS (TwO-Moment Aerosol Sectional) microphysics box model to constrain the following parameters in the OFR: (1) the rate constant of gas-phase functionalization reactions of organic compounds with OH, (2) the rate constant of gas-phase fragmentation reactions of organic compounds with OH, (3) the reactive uptake coefficient for heterogeneous fragmentation reactions with OH, (4) the nucleation rate constants for three different nucleation schemes, and (5) an effective accommodation coefficient that accounts for possible particle diffusion limitations of particles larger than 60nm in diameter. We find the best model-to-measurement agreement when the accommodation coefficient of the larger particles (Dp>60nm) was 0.1 or lower (with an accommodation coefficient of 1 for smaller particles), which suggests a diffusion limitation in the larger particles. When using these low accommodation-coefficient values, the model agrees with measurements when using a published H2SO4-organics nucleation mechanism and previously published values of rate constants for gas-phase oxidation reactions. Further, gas-phase fragmentation was found to have a significant impact upon the size distribution, and including fragmentation was necessary for accurately simulating the distributions in the OFR. The model was insensitive to the value of the reactive uptake coefficient on these aging timescales. Monoterpenes and isoprene could explain 24%-95% of the observed change in total volume of aerosol in the OFR, with ambient semivolatile and intermediate-volatility organic compounds (S/IVOCs) appearing to explain the remainder of the change in total volume. These results provide support to the mass-based findings of previous OFR studies, give insight to important size-distribution dynamics in the OFR, and enable the design of future OFR studies focused on new particle formation and/or microphysical processes., United States. Department of Energy. Office of Biological and Environmental Research (grant no. DE-SC0011780), United States. National Oceanic and Atmospheric Administration. Office of Atmospheric Chemistry, Carbon Cycle, and Climate Program (cooperative agreement award no. NA17OAR430001), United States. National Oceanic and Atmospheric Administration. Office of Atmospheric Chemistry, Carbon Cycle, and Climate Program (cooperative agreement award no. NA17OAR4310002), National Science Foundation (U.S.). Atmospheric Chemistry program (grant no. AGS-1559607), National Science Foundation (U.S.). Atmospheric Chemistry program (grant no. AGS-1558966), Fundação de Amparo à Pesquisa do Estado do Amazonas, Fundação de Amparo à Pesquisa do Estado de São Paulo, Brazil Scientific Mobility Program, United States. National Oceanic and Atmospheric Administration (grant NA10OAR4310106 (MIT)), National Science Foundation (U.S.), Austrian Science Fund (project no. L518-N20)
- Published
- 2018
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13. Arctic marine secondary organic aerosol contributes significantly to summertime particle size distributions in the Canadian Arctic Archipelago
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B. Croft, R. V. Martin, W. R. Leaitch, J. Burkart, R. Y.-W. Chang, D. B. Collins, P. L. Hayes, A. L. Hodshire, L. Huang, J. K. Kodros, A. Moravek, E. L. Mungall, J. G. Murphy, S. Sharma, S. Tremblay, G. R. Wentworth, M. D. Willis, J. P. D. Abbatt, and J. R. Pierce
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Atmospheric Science ,Particle number ,Chemical transport model ,010504 meteorology & atmospheric sciences ,Flux ,Context (language use) ,010501 environmental sciences ,Atmospheric sciences ,01 natural sciences ,lcsh:QC1-999 ,Aerosol ,Atmospheric Sciences ,Climate Action ,lcsh:Chemistry ,lcsh:QD1-999 ,Arctic ,13. Climate action ,Environmental science ,Particle ,Meteorology & Atmospheric Sciences ,Particle size ,14. Life underwater ,lcsh:Physics ,Astronomical and Space Sciences ,0105 earth and related environmental sciences - Abstract
Summertime Arctic aerosol size distributions are strongly controlled by natural regional emissions. Within this context, we use a chemical transport model with size-resolved aerosol microphysics (GEOS-Chem-TOMAS) to interpret measurements of aerosol size distributions from the Canadian Arctic Archipelago during the summer of 2016, as part of the “NETwork on Climate and Aerosols: Addressing key uncertainties in Remote Canadian Environments” (NETCARE) project. Our simulations suggest that condensation of secondary organic aerosol (SOA) from precursor vapors emitted in the Arctic and near Arctic marine (ice-free seawater) regions plays a key role in particle growth events that shape the aerosol size distributions observed at Alert (82.5∘ N, 62.3∘ W), Eureka (80.1∘ N, 86.4∘ W), and along a NETCARE ship track within the Archipelago. We refer to this SOA as Arctic marine SOA (AMSOA) to reflect the Arctic marine-based and likely biogenic sources for the precursors of the condensing organic vapors. AMSOA from a simulated flux (500 µgm-2day-1, north of 50∘ N) of precursor vapors (with an assumed yield of unity) reduces the summertime particle size distribution model–observation mean fractional error 2- to 4-fold, relative to a simulation without this AMSOA. Particle growth due to the condensable organic vapor flux contributes strongly (30 %–50 %) to the simulated summertime-mean number of particles with diameters larger than 20 nm in the study region. This growth couples with ternary particle nucleation (sulfuric acid, ammonia, and water vapor) and biogenic sulfate condensation to account for more than 90 % of this simulated particle number, which represents a strong biogenic influence. The simulated fit to summertime size-distribution observations is further improved at Eureka and for the ship track by scaling up the nucleation rate by a factor of 100 to account for other particle precursors such as gas-phase iodine and/or amines and/or fragmenting primary particles that could be missing from our simulations. Additionally, the fits to the observed size distributions and total aerosol number concentrations for particles larger than 4 nm improve with the assumption that the AMSOA contains semi-volatile species: the model–observation mean fractional error is reduced 2- to 3-fold for the Alert and ship track size distributions. AMSOA accounts for about half of the simulated particle surface area and volume distributions in the summertime Canadian Arctic Archipelago, with climate-relevant simulated summertime pan-Arctic-mean top-of-the-atmosphere aerosol direct (−0.04 W m−2) and cloud-albedo indirect (−0.4 W m−2) radiative effects, which due to uncertainties are viewed as an order of magnitude estimate. Future work should focus on further understanding summertime Arctic sources of AMSOA.
- Published
- 2019
14. Multiple new-particle growth pathways observed at the US DOE Southern Great Plains field site
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A. L. Hodshire, M. J. Lawler, J. Zhao, J. Ortega, C. Jen, T. Yli-Juuti, J. F. Brewer, J. K. Kodros, K. C. Barsanti, D. R. Hanson, P. H. McMurry, J. N. Smith, and J. R. Pierce
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Accretion (meteorology) ,Chemistry ,Condensation ,Sulfuric acid ,010501 environmental sciences ,01 natural sciences ,lcsh:QC1-999 ,Aerosol ,lcsh:Chemistry ,chemistry.chemical_compound ,Ammonia ,lcsh:QD1-999 ,Environmental chemistry ,Atmospheric chemistry ,Particle ,Acid–base reaction ,lcsh:Physics ,0105 earth and related environmental sciences - Abstract
New-particle formation (NPF) is a significant source of aerosol particles into the atmosphere. However, these particles are initially too small to have climatic importance and must grow, primarily through net uptake of low-volatility species, from diameters ∼ 1 to 30–100 nm in order to potentially impact climate. There are currently uncertainties in the physical and chemical processes associated with the growth of these freshly formed particles that lead to uncertainties in aerosol-climate modeling. Four main pathways for new-particle growth have been identified: condensation of sulfuric-acid vapor (and associated bases when available), condensation of organic vapors, uptake of organic acids through acid–base chemistry in the particle phase, and accretion of organic molecules in the particle phase to create a lower-volatility compound that then contributes to the aerosol mass. The relative importance of each pathway is uncertain and is the focus of this work. The 2013 New Particle Formation Study (NPFS) measurement campaign took place at the DOE Southern Great Plains (SGP) facility in Lamont, Oklahoma, during spring 2013. Measured gas- and particle-phase compositions during these new-particle growth events suggest three distinct growth pathways: (1) growth by primarily organics, (2) growth by primarily sulfuric acid and ammonia, and (3) growth by primarily sulfuric acid and associated bases and organics. To supplement the measurements, we used the particle growth model MABNAG (Model for Acid–Base chemistry in NAnoparticle Growth) to gain further insight into the growth processes on these 3 days at SGP. MABNAG simulates growth from (1) sulfuric-acid condensation (and subsequent salt formation with ammonia or amines), (2) near-irreversible condensation from nonreactive extremely low-volatility organic compounds (ELVOCs), and (3) organic-acid condensation and subsequent salt formation with ammonia or amines. MABNAG is able to corroborate the observed differing growth pathways, while also predicting that ELVOCs contribute more to growth than organic salt formation. However, most MABNAG model simulations tend to underpredict the observed growth rates between 10 and 20 nm in diameter; this underprediction may come from neglecting the contributions to growth from semi-to-low-volatility species or accretion reactions. Our results suggest that in addition to sulfuric acid, ELVOCs are also very important for growth in this rural setting. We discuss the limitations of our study that arise from not accounting for semi- and low-volatility organics, as well as nitrogen-containing species beyond ammonia and amines in the model. Quantitatively understanding the overall budget, evolution, and thermodynamic properties of lower-volatility organics in the atmosphere will be essential for improving global aerosol models.
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- 2016
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15. The evolution of biomass-burning aerosol size distributions due to coagulation: dependence on fire and meteorological details and parameterization
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K. M. Sakamoto, J. R. Laing, R. G. Stevens, D. A. Jaffe, and J. R. Pierce
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Meteorology ,Gaussian ,Evaporation ,Flux ,Magnitude (mathematics) ,010501 environmental sciences ,01 natural sciences ,lcsh:QC1-999 ,Wind speed ,Plume ,Aerosol ,lcsh:Chemistry ,symbols.namesake ,lcsh:QD1-999 ,Particle-size distribution ,symbols ,Environmental science ,lcsh:Physics ,Physics::Atmospheric and Oceanic Physics ,0105 earth and related environmental sciences - Abstract
Biomass-burning aerosols have a significant effect on global and regional aerosol climate forcings. To model the magnitude of these effects accurately requires knowledge of the size distribution of the emitted and evolving aerosol particles. Current biomass-burning inventories do not include size distributions, and global and regional models generally assume a fixed size distribution from all biomass-burning emissions. However, biomass-burning size distributions evolve in the plume due to coagulation and net organic aerosol (OA) evaporation or formation, and the plume processes occur on spacial scales smaller than global/regional-model grid boxes. The extent of this size-distribution evolution is dependent on a variety of factors relating to the emission source and atmospheric conditions. Therefore, accurately accounting for biomass-burning aerosol size in global models requires an effective aerosol size distribution that accounts for this sub-grid evolution and can be derived from available emission-inventory and meteorological parameters. In this paper, we perform a detailed investigation of the effects of coagulation on the aerosol size distribution in biomass-burning plumes. We compare the effect of coagulation to that of OA evaporation and formation. We develop coagulation-only parameterizations for effective biomass-burning size distributions using the SAM-TOMAS large-eddy simulation plume model. For the most-sophisticated parameterization, we use the Gaussian Emulation Machine for Sensitivity Analysis (GEM-SA) to build a parameterization of the aged size distribution based on the SAM-TOMAS output and seven inputs: emission median dry diameter, emission distribution modal width, mass emissions flux, fire area, mean boundary-layer wind speed, plume mixing depth, and time/distance since emission. This parameterization was tested against an independent set of SAM-TOMAS simulations and yields R2 values of 0.83 and 0.89 for Dpm and modal width, respectively. The size distribution is particularly sensitive to the mass emissions flux, fire area, wind speed, and time, and we provide simplified fits of the aged size distribution to just these input variables. The simplified fits were tested against 11 aged biomass-burning size distributions observed at the Mt. Bachelor Observatory in August 2015. The simple fits captured over half of the variability in observed Dpm and modal width even though the freshly emitted Dpm and modal widths were unknown. These fits may be used in global and regional aerosol models. Finally, we show that coagulation generally leads to greater changes in the particle size distribution than OA evaporation/formation does, using estimates of OA production/loss from the literature.
- Published
- 2016
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16. Evaluation of observed and modelled aerosol lifetimes using radioactive tracers of opportunity and an ensemble of 19 global models
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N. I. Kristiansen, A. Stohl, D. J. L. Olivié, B. Croft, O. A. Søvde, H. Klein, T. Christoudias, D. Kunkel, S. J. Leadbetter, Y. H. Lee, K. Zhang, K. Tsigaridis, T. Bergman, N. Evangeliou, H. Wang, P.-L. Ma, R. C. Easter, P. J. Rasch, X. Liu, G. Pitari, G. Di Genova, S. Y. Zhao, Y. Balkanski, S. E. Bauer, G. S. Faluvegi, H. Kokkola, R. V. Martin, J. R. Pierce, M. Schulz, D. Shindell, H. Tost, and H. Zhang
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lcsh:Chemistry ,lcsh:QD1-999 ,lcsh:Physics ,lcsh:QC1-999 - Abstract
Aerosols have important impacts on air quality and climate, but the processes affecting their removal from the atmosphere are not fully understood and are poorly constrained by observations. This makes modelled aerosol lifetimes uncertain. In this study, we make use of an observational constraint on aerosol lifetimes provided by radionuclide measurements and investigate the causes of differences within a set of global models. During the Fukushima Dai-Ichi nuclear power plant accident of March 2011, the radioactive isotopes cesium-137 (137Cs) and xenon-133 (133Xe) were released in large quantities. Cesium attached to particles in the ambient air, approximately according to their available aerosol surface area. 137Cs size distribution measurements taken close to the power plant suggested that accumulation-mode (AM) sulfate aerosols were the main carriers of cesium. Hence, 137Cs can be used as a proxy tracer for the AM sulfate aerosol's fate in the atmosphere. In contrast, the noble gas 133Xe behaves almost like a passive transport tracer. Global surface measurements of the two radioactive isotopes taken over several months after the release allow the derivation of a lifetime of the carrier aerosol. We compare this to the lifetimes simulated by 19 different atmospheric transport models initialized with identical emissions of 137Cs that were assigned to an aerosol tracer with each model's default properties of AM sulfate, and 133Xe emissions that were assigned to a passive tracer. We investigate to what extent the modelled sulfate tracer can reproduce the measurements, especially with respect to the observed loss of aerosol mass with time. Modelled 137Cs and 133Xe concentrations sampled at the same location and times as station measurements allow a direct comparison between measured and modelled aerosol lifetime. The e-folding lifetime τe, calculated from station measurement data taken between 2 and 9 weeks after the start of the emissions, is 14.3 days (95 % confidence interval 13.1–15.7 days). The equivalent modelled τe lifetimes have a large spread, varying between 4.8 and 26.7 days with a model median of 9.4 ± 2.3 days, indicating too fast a removal in most models. Because sufficient measurement data were only available from about 2 weeks after the release, the estimated lifetimes apply to aerosols that have undergone long-range transport, i.e. not for freshly emitted aerosol. However, modelled instantaneous lifetimes show that the initial removal in the first 2 weeks was quicker (lifetimes between 1 and 5 days) due to the emissions occurring at low altitudes and co-location of the fresh plume with strong precipitation. Deviations between measured and modelled aerosol lifetimes are largest for the northernmost stations and at later time periods, suggesting that models do not transport enough of the aerosol towards the Arctic. The models underestimate passive tracer (133Xe) concentrations in the Arctic as well but to a smaller extent than for the aerosol (137Cs) tracer. This indicates that in addition to too fast an aerosol removal in the models, errors in simulated atmospheric transport towards the Arctic in most models also contribute to the underestimation of the Arctic aerosol concentrations.
- Published
- 2016
17. Particle wall-loss correction methods in smog chamber experiments
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N. Wang, S. D. Jorga, J. R. Pierce, N. M. Donahue, and S. N. Pandis
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Atmospheric Science ,Materials science ,Correction method ,010504 meteorology & atmospheric sciences ,lcsh:TA715-787 ,lcsh:Earthwork. Foundations ,Mechanics ,010501 environmental sciences ,Smog chamber ,01 natural sciences ,Chemical reaction ,lcsh:Environmental engineering ,Aerosol ,TRACER ,Particle-size distribution ,Particle ,lcsh:TA170-171 ,Constant (mathematics) ,0105 earth and related environmental sciences - Abstract
The interaction of particles with the chamber walls has been a significant source of uncertainty when analyzing results of secondary organic aerosol (SOA) formation experiments performed in Teflon chambers. A number of particle wall-loss correction methods have been proposed including the use of a size-independent loss rate constant, the ratio of suspended organic mass to that of a conserved tracer (e.g., sulfate seeds), and a size-dependent loss rate constant, etc. For complex experiments such as the chemical aging of SOA, the results of the SOA quantification analysis can be quite sensitive to the adopted correction method due to the evolution of the particle size distribution and the duration of these experiments. We evaluated the performance of several particle wall-loss correction methods for aging experiments of α-pinene ozonolysis products. Determining the loss rates from seed loss periods is necessary for this system because it is not clear when chemical reactions have been completed. Results from the OA ∕ sulfate ratio and the size-independent correction methods can be influenced significantly by the size dependence of the particle wall-loss process. Coagulation can also affect the particle size distribution, especially for particles with diameter less than 100 nm, thus introducing errors in the results of the wall-loss correction. The corresponding loss rate constants may vary from experiment to experiment, and even during a specific experiment. Friction between the Teflon chamber walls and non-conductive surfaces can significantly increase particle wall-loss rates and the chamber may require weeks to recover to its original condition. Experimental procedures are proposed for the characterization of particle losses during different stages of these experiments and the evaluation of corresponding particle wall-loss correction.
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- 2018
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18. A comparison of four receptor models used to quantify the boreal wildfire smoke contribution to surface PM2.5 in Halifax, Nova Scotia during the BORTAS-B experiment
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M. D. Gibson, J. Haelssig, J. R. Pierce, M. Parrington, J. E. Franklin, J. T. Hopper, Z. Li, and T. J. Ward
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lcsh:Chemistry ,lcsh:QD1-999 ,lcsh:Physics ,lcsh:QC1-999 - Abstract
This paper presents a quantitative comparison of the four most commonly used receptor models, namely absolute principal component scores (APCS), pragmatic mass closure (PMC), chemical mass balance (CMB) and positive matrix factorization (PMF). The models were used to predict the contributions of a wide variety of sources to PM2.5 mass in Halifax, Nova Scotia during the experiment to quantify the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS). However, particular emphasis was placed on the capacity of the models to predict the boreal wildfire smoke contributions during the BORTAS experiment. The performance of the four receptor models was assessed on their ability to predict the observed PM2.5 with an R2 close to 1, an intercept close to zero, a low bias and low RSME. Using PMF, a new woodsmoke enrichment factor of 52 was estimated for use in the PMC receptor model. The results indicate that the APCS and PMC receptor models were not able to accurately resolve total PM2.5 mass concentrations below 2 μg m−3. CMB was better able to resolve these low PM2.5 concentrations, but it could not be run on 9 of the 45 days of PM2.5 samples. PMF was found to be the most robust of the four models since it was able to resolve PM2.5 mass below 2 μg m−3, predict PM2.5 mass on all 45 days and utilise an unambiguous woodsmoke chemical tracer. The median woodsmoke relative contributions to PM2.5 estimated using PMC, APCS, CMB and PMF were found to be 0.08, 0.09, 3.59 and 0.14 μg m−3 respectively. The contribution predicted by the CMB model seemed to be clearly too high based on other observations. The use of levoglucosan as a tracer for woodsmoke was found to be vital for identifying this source.
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- 2015
19. Characterizing Impacts of Wildfire Smoke Exposure on Medication Fills and Outpatient Visits for Asthma during the 2015 Wildfire Season in the Western United States
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Gasparrini A, Katelyn O'Dell, Saha S, Bonne Ford, Sheryl Magzamen, A. Vaidyanathan, Vicedo-Cabrera A, R. Gan, and J. R. Pierce
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Global and Planetary Change ,Outpatient visits ,Epidemiology ,business.industry ,Health, Toxicology and Mutagenesis ,Environmental health ,Public Health, Environmental and Occupational Health ,medicine ,medicine.disease ,business ,Pollution ,Smoke exposure ,Asthma - Published
- 2019
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20. Weak global sensitivity of cloud condensation nuclei and the aerosol indirect effect to Criegee + SO2 chemistry
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J. R. Pierce, M. J. Evans, C. E. Scott, S. D. D'Andrea, D. K. Farmer, E. Swietlicki, and D. V. Spracklen
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lcsh:Chemistry ,lcsh:QD1-999 ,lcsh:Physics ,lcsh:QC1-999 - Abstract
H2SO4 vapor is important for the nucleation of atmospheric aerosols and the growth of ultrafine particles to cloud condensation nuclei (CCN) sizes with important roles in the global aerosol budget and hence planetary radiative forcing. Recent studies have found that reactions of stabilized Criegee intermediates (CIs, formed from the ozonolysis of alkenes) with SO2 may be an important source of H2SO4 that has been missing from atmospheric aerosol models. For the first time in a global model, we investigate the impact of this new source of H2SO4 in the atmosphere. We use the chemical transport model, GEOS-Chem, with the online aerosol microphysics module, TOMAS, to estimate the possible impact of CIs on present-day H2SO4, CCN, and the cloud-albedo aerosol indirect effect (AIE). We extend the standard GEOS-Chem chemistry with CI-forming reactions (ozonolysis of isoprene, methyl vinyl ketone, methacrolein, propene, and monoterpenes) from the Master Chemical Mechanism. Using a fast rate constant for CI+SO2, we find that the addition of this chemistry increases the global production of H2SO4 by 4%. H2SO4 concentrations increase by over 100% in forested tropical boundary layers and by over 10–25% in forested NH boundary layers (up to 100% in July) due to CI+SO2 chemistry, but the change is generally negligible elsewhere. The predicted changes in CCN were strongly dampened to the CI+SO2 changes in H2SO4 in some regions: less than 15% in tropical forests and less than 2% in most mid-latitude locations. The global-mean CCN change was less than 1% both in the boundary layer and the free troposphere. The associated cloud-albedo AIE change was less than 0.03 W m−2. The model global sensitivity of CCN and the AIE to CI+SO2 chemistry is significantly (approximately one order-of-magnitude) smaller than the sensitivity of CCN and AIE to other uncertain model inputs, such as nucleation mechanisms, primary emissions, SOA (secondary organic aerosol) and deposition. Similarly, comparisons to size-distribution measurements show that uncertainties in other model parameters dominate model biases in the model-predicted size distributions. We conclude that improvement in the modeled CI+SO2 chemistry would not likely lead to significant improvements in present-day CCN and AIE predictions.
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- 2013
21. Supplementary material to 'Constraining uncertainties in particle wall-deposition correction during SOA formation in chamber experiments'
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T. Nah, R. C. McVay, J. R. Pierce, J. H. Seinfeld, and N. L. Ng
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- 2016
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22. Supplementary material to 'The evolution of biomass-burning aerosol size distributions due to coagulation: dependence on fire and meteorological details and parameterization'
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K. M. Sakamoto, R. G. Stevens, and J. R. Pierce
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- 2016
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23. The effect of coal-fired power-plant SO2 and NOx control technologies on aerosol nucleation in the source plumes
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E. M. Knipping, P. A. Makar, C. A. Brock, R. G. Stevens, C. R. Lonsdale, and J. R. Pierce
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lcsh:Chemistry ,lcsh:QD1-999 ,lcsh:Physics ,lcsh:QC1-999 - Abstract
Nucleation in coal-fired power-plant plumes can greatly contribute to particle number concentrations near source regions. The changing emissions rates of SO2 and NOx due to pollution-control technologies over recent decades may have had a significant effect on aerosol formation and growth in the plumes with ultimate implications for climate and human health. We use the System for Atmospheric Modeling (SAM) large-eddy simulation model with the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm to model the nucleation in plumes of coal-fired plants. We test a range of cases with varying emissions to simulate the implementation of emissions-control technologies between 1997 and 2010. We start by simulating the W. A. Parish power plant (near Houston, TX) during this time period, when NOx emissions were reduced by ~90% and SO2 emissions decreased by ~30%. Increases in plume OH (due to the reduced NOx) produced enhanced SO2 oxidation and an order-of-magnitude increase in particle nucleation in the plume despite the reduction in SO2 emissions. These results suggest that NOx emissions could strongly regulate particle nucleation and growth in power-plant plumes. Next, we test a range of cases with varying emissions to simulate the implementation of SO2 and NOx emissions-control technologies. Particle formation generally increases with SO2 emission, while NOx shows two different regimes: increasing particle formation with increasing NOx under low-NOx emissions and decreasing particle formation with increasing NOx under high-NOx emissions. Next, we compare model results with airborne measurements made in the W. A. Parish power-plant plume in 2000 and 2006, confirming the importance of NOx emissions on new particle formation and highlighting the substantial effect of background aerosol loadings on this process (the more polluted background of the 2006 case caused more than an order-of-magnitude reduction in particle formation in the plume compared to the cleaner test day in 2000). Finally, we calculate particle-formation statistics of 330 coal-fired power plants in the US in 1997 and 2010, and the model results show a median decrease of 19% in particle formation rates from 1997 to 2010 (whereas the W. A. Parish case study showed an increase). Thus, the US power plants, on average, show a different result than was found for the W. A. Parish plant specifically, and it shows that the strong NOx controls (90% reduction) implemented at the W. A. Parish plant (with relatively weak SO2 emissions reductions, 30%) are not representative of most power plants in the US during the past 15 yr. These results suggest that there may be important climate implications of power-plant controls due to changes in plume chemistry and microphysics, but the magnitude and sign of the aerosol changes depend greatly on the relative reductions in NOx and SO2 emissions in each plant. More extensive plume measurements for a range of emissions of SO2 and NOx and in varying background aerosol conditions are needed, however, to better quantify these effects.
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- 2012
24. Uncertainty in global CCN concentrations from uncertain aerosol nucleation and primary emission rates
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J. R. Pierce and P. J. Adams
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lcsh:Chemistry ,lcsh:QD1-999 ,lcsh:Physics ,lcsh:QC1-999 - Abstract
The indirect effect of aerosols on climate is highly uncertain and limits our ability to assess anthropogenic climate change. The foundation of this uncertainty is uncertainty in the number of cloud condensation nuclei (CCN), which itself stems from uncertainty in aerosol nucleation, primary emission and growth rates. In this paper, we use a global general circulation model with aerosol microphysics to assess how the uncertainties in aerosol nucleation, emission and growth rates affect our prediction of CCN(0.2%) concentrations. Using two nucleation rate parameterizations that differ in globally averaged nucleation rate by 106, the tropospheric average CCN(0.2%) concentrations vary by 17% and the boundary layer average vary by 12%. This sensitivity of tropospheric average CCN(0.2%) to the nucleation parameterizations increases to 33% and 20% when the total primary emissions are reduced by a factor of 3 and the SOA condensation rates are increased by a factor of 3.5, respectively. These results show that it is necessary to understand better global nucleation rates when determining CCN concentrations. When primary emissions rates are varied by a factor of 3 while using the slower nucleation rate parameterization, tropospheric average CCN(0.2%) concentrations also vary by 17%, but boundary layer average vary by 40%. Using the faster nucleation rate parameterization, these changes drop to 3% and 22%, respectively. These results show the importance of reducing uncertainties in primary emissions, which appear from these results to be somewhat more important for CCN than the much larger uncertainties in nucleation. These results also show that uncertainties in nucleation and primary emissions are more important when sufficient condensable material is available to grow them to CCN sizes. The percent change in CCN(0.2%) concentration between pre-industrial times and present day does not depend greatly on the nucleation rate parameterization used for our base case scenarios; however, because other factors, such as primary emissions and SOA, are uncertain in both time periods, this may be a coincidence.
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- 2009
25. Evaluation of observed and modelled aerosol lifetimes using radioactive tracers of opportunity and an ensemble of 19 global models
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N. I. Kristiansen, A. Stohl, D. J. L. Olivié, B. Croft, O. A. Søvde, H. Klein, T. Christoudias, D. Kunkel, S. J. Leadbetter, Y. H. Lee, K. Zhang, K. Tsigaridis, T. Bergman, N. Evangeliou, H. Wang, P.-L. Ma, R. C. Easter, P. J. Rasch, X. Liu, G. Pitari, G. Di Genova, S. Y. Zhao, Y. Balkanski, S. E. Bauer, G. S. Faluvegi, H. Kokkola, R. V. Martin, J. R. Pierce, M. Schulz, D. Shindell, H. Tost, H. Zhang, Norwegian Institute for Air Research (NILU), Murdoch Children's Research Institute (MCRI), Max-Planck-Institut für Chemie (MPIC), Max-Planck-Gesellschaft, Center for Climate Systems Research [New York] (CCSR), Columbia University [New York], Finnish Meteorological Institute (FMI), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), China Jiliang University (CJLU), Centre Interdisciplinaire de Nanoscience de Marseille (CINaM), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Dipartimento di Fisica [L'Aquila], Università degli Studi dell'Aquila = University of L'Aquila (UNIVAQ), McGill University = Université McGill [Montréal, Canada], Modelling the Earth Response to Multiple Anthropogenic Interactions and Dynamics (MERMAID), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Università degli Studi dell'Aquila (UNIVAQ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), and Centre National de la Recherche Scientifique (CNRS)-Aix Marseille Université (AMU)
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[PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph] ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,010504 meteorology & atmospheric sciences ,13. Climate action ,010501 environmental sciences ,01 natural sciences ,7. Clean energy ,0105 earth and related environmental sciences - Abstract
Aerosols have important impacts on air quality and climate, but the processes affecting their removal from the atmosphere are not fully understood and are poorly constrained by observations. This makes modelled aerosol lifetimes uncertain. In this study, we make use of an observational constraint on aerosol lifetimes provided by radionuclide measurements and investigate the causes of differences within a set of global models. During the Fukushima Dai-Ichi nuclear power plant accident of March 2011, the radioactive isotopes cesium-137 (137Cs) and xenon-133 (133Xe) were released in large quantities. Cesium attached to particles in the ambient air, approximately according to their available aerosol surface area. 137Cs size distribution measurements taken close to the power plant suggested that accumulation-mode (AM) sulphate aerosols were the main carriers for the cesium. Hence, 137Cs can be used as a proxy tracer for the AM sulphate aerosol's fate in the atmosphere. In contrast, the noble gas 133Xe behaves almost like a passive transport tracer. Global surface measurements of the two radioactive isotopes taken over several months after the release allow the derivation of a lifetime of the carrier aerosol. We compare this to the lifetimes simulated by 19 different atmospheric transport models initialized with identical emissions of 137Cs that were assigned to an aerosol tracer with each model's default properties of AM sulphate, and 133Xe emissions that were assigned to a passive tracer. We investigate to what extent the modelled sulphate tracer can reproduce the measurements, especially with respect to the observed loss of aerosol mass with time. Modelled 37Cs and 133Xe concentrations sampled at the same location and times as station measurements allow a direct comparison between measured and modelled aerosol lifetime. The e-folding lifetime τe, calculated from station measurement data taken between two and nine weeks after the start of the emissions, is 14.3 days (95 % confidence interval 13.1–15.7 days). The equivalent modelled τe lifetimes have a large spread, varying between 4.8 and 26.7 days with a model median of 9.4 ± 2.3 days, indicating too fast removal in most models. Because sufficient measurement data were only available from about two weeks after the release, the estimated lifetimes apply to aerosols that have undergone long-range transport, i.e. not for freshly emitted aerosol. However, modelled instantaneous lifetimes show that the initial removal in the first two weeks was quicker (lifetimes between 1–5 days) due to the emissions occurring at low altitudes and co-location of the fresh plume with strong precipitation. Deviations between measured and modelled aerosol lifetimes are largest for the northernmost stations and at later time periods, suggesting that models do not transport enough of the aerosol towards the Arctic. The models underestimate passive tracer (133Xe) concentrations in the Arctic as well but to a smaller extent than for the aerosol (137Cs) tracer. This indicates that in addition to too fast aerosol removal in the models, errors in simulated atmospheric transport towards the Arctic in most models also contribute to the Arctic aerosol underestimates.
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- 2016
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26. Efficiency of cloud condensation nuclei formation from ultrafine particles
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J. R. Pierce and P. J. Adams
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lcsh:Chemistry ,lcsh:QD1-999 ,lcsh:Physics ,lcsh:QC1-999 - Abstract
Atmospheric cloud condensation nuclei (CCN) concentrations are a key uncertainty in the assessment of the effect of anthropogenic aerosol on clouds and climate. The ability of new ultrafine particles to grow to become CCN varies throughout the atmosphere and must be understood in order to understand CCN formation. We have developed the Probability of Ultrafine particle Growth (PUG) model to answer questions regarding which growth and sink mechanisms control this growth, how the growth varies between different parts of the atmosphere and how uncertainties with respect to the magnitude and size distribution of ultrafine emissions translates into uncertainty in CCN generation. The inputs to the PUG model are the concentrations of condensable gases, the size distribution of ambient aerosol, particle deposition timescales and physical properties of the particles and condensable gases. It was found in most cases that condensation is the dominant growth mechanism and coagulation with larger particles is the dominant sink mechanism for ultrafine particles. In this work we found that the probability of a new ultrafine particle generating a CCN varies from
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- 2007
27. Supplementary material to 'Ammonia in the summertime Arctic marine boundary layer: sources, sinks and implications'
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G. R. Wentworth, J. G. Murphy, B. Croft, R. V. Martin, J. R. Pierce, J.-S. Côté, I. Courchesne, J.-É. Tremblay, J. Gagnon, J. L. Thomas, S. Sharma, D. Toom-Sauntry, A. Chivulescu, M. Levasseur, and J. P. D. Abbatt
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- 2015
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28. Processes controlling the seasonal cycle of Arctic aerosol number and size distributions
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B. Croft, R. V. Martin, W. R. Leaitch, P. Tunved, T. J. Breider, S. D. D'Andrea, and J. R. Pierce
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respiratory system ,complex mixtures - Abstract
Measurements at high-Arctic sites show a strong seasonal cycle in aerosol number and size. The number of aerosols with diameters larger than 20 nm exhibits a maximum in late spring associated with a dominant accumulation mode (0.1 to 1 μm in diameter), and a second maximum in the summer associated with a dominant Aitken mode (10 to 100 nm in diameter). Seasonal-mean aerosol effective diameter ranges from about 180 nm in summer to 260 nm in winter. This study interprets these seasonal cycles with the GEOS-Chem-TOMAS global aerosol microphysics model. We find improved agreement with in-situ measurements of aerosol size at both Alert, Nunavut, and Mt. Zeppelin, Svalbard following model developments that: (1) increase the efficiency of wet scavenging in the Arctic summer and (2) represent coagulation between interstitial aerosols and aerosols activated to form cloud droplets. Our simulations indicate that the dominant summertime Aitken mode is associated with increased efficiency of wet removal, which limits the number of larger aerosols and promotes local new-particle formation. We also find an important role of interstitial coagulation in clouds in the Arctic, which limits the number of Aitken-mode aerosols in the non-summer seasons when direct wet removal of these aerosols is inefficient. Total aerosol number reaches a minimum in October at both Alert and Mt. Zeppelin. Our simulations indicate that this October minimum can be explained by diminishing local new-particle formation, limited transport of pollution from lower latitudes, and efficient wet removal. We recommend that the key processes of aerosol wet removal, interstitial coagulation and new-particle formation be carefully considered in size-resolved aerosol simulations of the Arctic. Uncertainties about these processes, which strongly control the seasonal cycle of aerosol number and size, limit confidence in estimates of aerosol radiative effects on the Arctic climate.
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- 2015
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29. Source attribution of aerosol size distributions and model evaluation using Whistler Mountain measurements and GEOS-Chem-TOMAS simulations
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S. D. D'Andrea, J. Y. Ng, J. K. Kodros, S. A. Atwood, M. J. Wheeler, A. M. Macdonald, W. R. Leaitch, and J. R. Pierce
- Abstract
Remote and free tropospheric aerosols represent a large fraction of the climatic influence of aerosols; however, aerosol in these regions is less characterized than those polluted boundary layers. We evaluate aerosol size distributions predicted by the GEOS-Chem-TOMAS global chemical transport model with online aerosol microphysics using measurements from the peak of Whistler Mountain, BC, Canada (2182 m a.s.l.). We evaluate the model for predictions of aerosol number, size and composition during periods of free tropospheric (FT) and boundary-layer (BL) influence at "coarse" 4° × 5° and "nested" 0.5° × 0.667° resolutions by developing simple FT/BL filtering techniques. We find that using temperature as a proxy for upslope flow (BL influence) improved the model measurement comparisons. The best threshold temperature was around 2 °C for the coarse simulations and around 6 °C for the nested simulations, with temperatures warmer than the threshold indicating boundary-layer air. Additionally, the site was increasingly likely to be in-cloud when the measured RH was above 90 %, so we do not compare the modeled and measured size distributions during these periods. With the inclusion of these temperature and RH filtering techniques, the model-measurement comparisons improved significantly. The slope of the regression for N80 (the total number of particles with particle diameter, Dp > 80 nm) in the nested simulations increased from 0.09 to 0.65, R2 increased from 0.04 to 0.46, and log-mean bias improved from 0.95 to 0.07. We also perform simulations at the nested resolution without Asian anthropogenic (AA) emissions and without biomass-burning (BB) emissions to quantify the contribution of these sources to aerosols at Whistler Peak (through comparison with simulations with these emissions on). The long-range transport of AA aerosol was found to be significant throughout all particle number concentrations, and increased the number of particles larger than 80 nm (N80) by more than 50 %, while decreasing the number of smaller particles because of suppression of new-particle formation and enhanced coagulation sink. Similarly, BB influenced Whistler Peak during summer months, with an increase in N80 exceeding 5000 cm−3. Occasionally, Whistler Peak experienced N80 > 1000 cm−3 without significant influence from AA or BB aerosol. Air masses were advected at low elevations through forested valleys during times when temperature and downwelling insolation were high, ideal conditions for formation of large sources of low-volatility biogenic secondary organic aerosol (SOA). This condensable material increased particle growth and hence N80. The low-cost filtering techniques and source apportionment used in this study can be used in other global models to give insight into the sources and processes that shape the aerosol at mountain sites, leading to a better understanding of mountain meteorology and chemistry.
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- 2015
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30. Impact of gas-to-particle partitioning approaches on the simulated radiative effects of biogenic secondary organic aerosol
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C. E. Scott, D. V. Spracklen, J. R. Pierce, I. Riipinen, S. D. D'Andrea, A. Rap, K. S. Carslaw, P. M. Forster, M. Kulmala, G. W. Mann, and K. J. Pringle
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The oxidation of biogenic volatile organic compounds (BVOCs) gives a range of products, from semi-volatile to extremely low-volatility compounds. To treat the interaction of these secondary organic vapours with the particle phase, global aerosol microphysics models generally use either a thermodynamic partitioning approach (assuming instant equilibrium between semi-volatile oxidation products and the particle phase) or a kinetic approach (accounting for the size-dependence of condensation). We show that model treatment of the partitioning of biogenic organic vapours into the particle phase, and consequent distribution of material across the size distribution, controls the magnitude of the first aerosol indirect effect (AIE) due to biogenic secondary organic aerosol (SOA). With a kinetic partitioning approach, SOA is distributed according to the existing condensation sink, enhancing the growth of the smallest particles, i.e., those in the nucleation mode. This process tends to increase cloud droplet number concentrations in the presence of biogenic SOA. By contrast, a thermodynamic approach distributes SOA according to pre-existing organic mass, restricting the growth of the smallest particles, limiting the number that are able to form cloud droplets. With an organically medicated new particle formation mechanism, applying a thermodynamic rather than a kinetic approach reduces our calculated global mean AIE due to biogenic SOA by 24%. Our results suggest that the mechanisms driving organic partitioning need to be fully understood in order to accurately describe the climatic effects of SOA.
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- 2015
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31. Aged boreal biomass burning aerosol size distributions from BORTAS 2011
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K. M. Sakamoto, J. D. Allan, H. Coe, J. W. Taylor, T. J. Duck, and J. R. Pierce
- Abstract
Biomass-burning aerosols contribute to aerosol radiative forcing on the climate system. The magnitude of this effect is partially determined by aerosol size distributions, which are functions of source fire characteristics (e.g. fuel type, MCE) and in-plume microphysical processing. The uncertainties in biomass-burning emission number size-distributions in climate model inventories lead to uncertainties in the CCN concentrations and forcing estimates derived from these models. The BORTAS-B measurement campaign was designed to sample boreal biomass-burning outflow over Eastern Canada in the summer of 2011. Using these BORTAS-B data, we implement plume criteria to isolate the characteristic size-distribution of aged biomass-burning emissions (aged ∼1–2 days) from boreal wildfires in Northwestern Ontario. The composite median size-distribution yields a single dominant accumulation mode with Dpm = 230 nm (number-median diameter), σ = 1.7, which are comparable to literature values of other aged plumes of a similar type. The organic aerosol enhancement ratios (ΔOA / ΔCO) along the path of Flight b622 show values of 0.05–0.18 μg m−3 ppbv−1 with no significant trend with distance from the source. This lack of enhancement ratio increase/decrease with distance suggests no detectable net OA production/evaporation within the aged plume over the sampling period. A Lagrangian microphysical model was used to determine an estimate of the freshly emitted size distribution corresponding to the BORTAS-B aged size-distributions. The model was restricted to coagulation and dilution processes based on the insignificant net OA production/evaporation derived from the ΔOA / ΔCO enhancement ratios. We estimate that the fresh-plume median diameter was in the range of 59–94 nm with modal widths in the range of 1.7–2.8 (the ranges are due to uncertainty in the entrainment rate). Thus, the size of the freshly emitted particles is relatively unconstrained due to the uncertainties in the plume dilution rates.
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- 2014
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32. A case study of aerosol depletion in a biomass burning plume over Eastern Canada during the 2011 BORTAS field experiment
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J. E. Franklin, J. R. Drummond, D. Griffin, J. R. Pierce, D. L. Waugh, P. I. Palmer, M. Parrington, J. D. Lee, A. C. Lewis, A. R. Rickard, J. W. Taylor, J. D. Allan, H. Coe, K. A. Walker, L. Chisholm, T. J. Duck, J. T. Hopper, Y. Blanchard, M. D. Gibson, K. R. Curry, K. M. Sakamoto, G. Lesins, L. Dan, J. Kliever, and A. Saha
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We present measurements of a long range smoke transport event recorded on 20–21 July 2011 over Halifax, Nova Scotia, Canada, during the Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS-B) campaign. Ground-based Fourier transform spectrometers and photometers detected air masses associated with large wildland fires burning in eastern Manitoba and western Ontario. We investigate a plume with high trace gas amounts but low amounts of particles that preceded and overlapped at the Halifax site with a second plume with high trace gas loadings and significant amounts of particulate material. We show that the first plume experienced a meteorological scavenging event but the second plume had not been similarly scavenged. This points to the necessity to account carefully for the plume history when considering long range transport since simultaneous or near-simultaneous times of arrival are not necessarily indicative of either similar trajectories or meteorological history. We investigate the origin of the scavenged plume, and the possibility of an aerosol wet deposition event occurring in the plume ~24 h prior to the measurements over Halifax. The region of lofting and scavenging is only monitored on an intermittent basis by the present observing network, and thus we must consider many different pieces of evidence in an effort to understand the early dynamics of the plume. Through this discussion we also demonstrate the value of having many simultaneous remote-sensing measurements in order to understand the physical and chemical behaviour of biomass burning plumes.
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- 2014
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33. Utilization Management Affects Health Care Practices at Walter Reed Army Medical Center: Analytical Methods Applied to Decrease Length of Stay and Assign Appropriate Level of Care
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J S Phillips, M J Kussman, J R Pierce, and C K Hamm
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Gerontology ,medicine.medical_specialty ,Inpatient care ,business.industry ,Public health ,media_common.quotation_subject ,Control (management) ,Public Health, Environmental and Occupational Health ,General Medicine ,medicine.disease ,Resource (project management) ,Health care ,medicine ,Medical emergency ,Duration (project management) ,business ,Empowerment ,Utilization management ,media_common - Abstract
The Department of Defense has embraced utilization management (UM) as an important tool to control and possibly decrease medical costs. Budgetary withholds have been taken by the Office of the Assistant Secretary of Defense (Health Affairs) to encourage the military services to implement UM programs. In response, Walter Reed Army Medical Center implemented a UM program along with other initiatives to effect changes in the delivery of inpatient care. This paper describes this UM program and other organizational initiatives, such as the introduction of new levels of care in an attempt to effect reductions in length of stay and unnecessary admissions. We demonstrate the use of a diversity of databases and analytical methods to quantify improved utilization and management of resources. The initiatives described significantly reduced hospital length of stay and inappropriate inpatient days. Without solid command and clinical leadership support and empowerment of the professional staffs, these significant changes and improvements could not have occurred.
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- 1999
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34. Responses of Non-Target Aquatic Organisms to Aqueous Propanil Exposure
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C. D. Milam, Matthew T. Moore, J. R. Pierce, E. L. Winchester, and Jerry L. Farris
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Amphipoda ,Health, Toxicology and Mutagenesis ,Cyprinidae ,Propanil ,Toxicology ,Risk Assessment ,Chironomidae ,Lethal Dose 50 ,Xenopus laevis ,chemistry.chemical_compound ,Crustacea ,Animals ,Ecotoxicology ,biology ,Herbicides ,Ecology ,Hyalella azteca ,Ceriodaphnia dubia ,General Medicine ,Pesticide ,biology.organism_classification ,Pollution ,chemistry ,Midge ,Pimephales promelas ,Water Pollutants, Chemical - Abstract
Propanil (3',4'-dichloropropionanilide) is one of the world’s most widely used rice herbicides, and it is extensively used in Arkansas, the leading rice producer in the United States (Webster and Gunnel1 1992). On average, the United States has applied approximately five kg/ha/year to about 70-100% of rice hectareacreage for the past two decades (US EPA 1987; Schlenk and Moore 1993). Arkansas, in 1992 alone, applied over 2.7 million kg of propanil (Jackman 1994). It is important to understand the toxicity of such herbicides to non-target aquatic organisms because of the amounts of pesticide field application and the risk of mixture with water exiting fields. During agricultural applications, aerial drift or accidental spills may expose nearby non-target areas such as ponds, rivers, lakes, wetlands, etc. to herbicides. Predictions of possible impacts upon the diverse range of species found in these ecosystems are usually drawn from a somewhat limited number of toxicity tests with standardized organisms. Comparative toxicity tests should use species of different feeding preferences, habitats, physiology, and size to determine a toxicant’s effects (Rodgers et al. 1997). The relative sensitivities of five freshwater aquatic test species to propanil were determined in aqueous laboratory exposures to provide a wider range of response data inclusive of amphibians, insects, and crustacea. Test species utilized in this study were a cladoceran (Ceriodaphnia dubia), an epibenthic amphipod (Hyalella azteca), a larval midge (Chironomus tentans), the fathead minnow (Pimephnles promelas), and an amphibian (Xenopus laevis). Data generated from such comparative toxicity experiments may be used for future assessments of potential effects on non-target organisms following accidental (or intentional) exposures. Comparative slopes that are specific for each test organism can also offer resolution of risks associated with the recent movement toward using more concentrated pesticide products.
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- 1998
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35. AAAR 32nd Annual Conference Abstract book, http://aaarabstracts.com/2013/AbstractBook.pdf
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S. A. K. Hxe4kkinen, H. E. Manninen, T. Yli-Juuti, J. Merikanto, M. Kajos, T. Nieminen, S. D. D'Andrea, A. Asmi, J. R. Pierce, M. Kulmala, and I. Riipinen
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- 2013
36. A parameterization of sub-grid particle formation in sulphur-rich plumes for global and regional-scale models
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R. G. Stevens and J. R. Pierce
- Abstract
New-particle formation in the plumes of coal-fired power plants and other anthropogenic sulphur sources may be an important source of particles in the atmosphere. It remains unclear, however, how best to reproduce this formation in global and regional aerosol models with grid-box lengths that are tens of kilometres and larger. Based on the results of the System for Atmospheric Modelling (SAM), a Large-Eddy Simulation/Cloud-Resolving Model (LES/CRM) with online TwO Moment Aerosol Sectional (TOMAS) microphysics, we have developed a computationally efficient, but physically based, parameterization that predicts the characteristics of aerosol formed within sulphur-rich plumes based on parameters commonly available in global- and regional-scale models. Given large-scale mean meteorological parameters ((1) wind speed, (2) boundary-layer height and (3) downward shortwave radiative flux), (4) emissions of SO2 and (5) NOx from the source, (6) mean background condensation sink, (7) background SO2 and (8) NOx concentrations, and (9) the desired distance from the source; the parameterization will predict: (1) the fraction of the emitted SO2 that is oxidized to H2SO4, (2) the fraction of that H2SO4 that forms new particles instead of condensing onto preexisting particles, (3) the mean mass per particle of the newly formed particles, and (4) the number of newly formed particles per kilogram SO2 emitted. The parameterization we describe here should allow for more accurate predictions of aerosol size distributions and a greater confidence in the effects of aerosols in climate and health studies.
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- 2013
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37. Supplementary material to 'A parameterization of sub-grid particle formation in sulphur-rich plumes for global and regional-scale models'
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R. G. Stevens and J. R. Pierce
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- 2013
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38. Identifying the sources driving observed PM2.5 variability over Halifax, Nova Scotia, during BORTAS-B
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M. D. Gibson, J. R. Pierce, D. Waugh, J. S. Kuchta, L. Chisholm, T. J. Duck, J. T. Hopper, S. Beauchamp, G. H. King, J. E. Franklin, W. R. Leaitch, A. J. Wheeler, Z. Li, G. A. Gagnon, and P. I. Palmer
- Abstract
The source attribution of observed variability of total PM2.5 concentrations over Halifax, Nova Scotia was investigated between 11 July–26 August 2011 using measurements of PM2.5 mass and PM2.5 chemical composition (black carbon, organic matter, anions, cations and 33 elements). This was part of the BORTAS-B (quantifying the impact of BOReal forest fires on Tropospheric oxidants using aircraft and satellites) experiment, which investigated the atmospheric chemistry and transport of seasonal boreal wild fire emissions over eastern Canada in 2011. The US EPA Positive Matrix Factorization (PMF) receptor model was used to determine the average mass (percentage) source contribution over the 45 days, which was estimated to be: Long-Range Transport (LRT) Pollution 1.75 μg m−3 (47%), LRT Pollution Marine Mixture 1.0 μg m−3 (27.9%), Vehicles 0.49 μg m−3 (13.2%), Fugitive Dust 0.23 μg m−3 (6.3%), Ship Emissions 0.13 μg m−3 (3.4%) and Refinery 0.081 μg m−3 (2.2%). The PMF model describes 87% of the observed variability in total PM2.5 mass (bias = 0.17 and RSME = 1.5 μg m−3). The factor identifications are based on chemical markers, and they are supported by air mass back trajectory analysis and local wind direction. Biomass burning plumes, found by other surface and aircraft measurements, were not significant enough to be identified in this analysis. This paper presents the results of the PMF receptor modelling, providing valuable insight into the local and upwind sources impacting surface PM2.5 in Halifax during the BORTAS-B mission.
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- 2013
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39. Representation of nucleation mode microphysics in global aerosol microphysics models
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Y. H. Lee, J. R. Pierce, and P. J. Adams
- Abstract
In models, nucleation mode (1 nm < Dp < 10 nm) particle microphysics can be represented explicitly with aerosol microphysical processes or can be parameterized to obtain the growth and survival of nuclei to the model's lower size boundary. This study investigates how the representation of nucleation mode microphysics impacts aerosol number predictions in the TwO-Moment Aerosol Sectional (TOMAS) aerosol microphysics model running with the GISS GCM II-prime by varying its lowest diameter boundary: 1 nm, 3 nm, and 10 nm. The model with the 1 nm boundary simulates the nucleation mode particles with fully resolved microphysical processes, while the model with the 10 nm and 3 nm boundaries uses a nucleation mode dynamics parameterization to account for the growth of nucleated particles to 10 nm and 3 nm, respectively. We also investigate the impact of the time step for aerosol microphysical processes (a 10-min versus a 1-h time step) to aerosol number predictions in the TOMAS models with explicit dynamics for the nucleation mode particles (i.e. 3 nm and 1 nm boundary). The model with the explicit microphysics (i.e. 1 nm boundary) with the 10-min time step is used as a numerical benchmark simulation to estimate biases caused by varying the lower size cutoff and the time step. Different representations of the nucleation mode have a significant effect on the formation rate of particles larger than 10 nm from nucleated particles (J10) and the burdens and lifetimes of ultrafine mode (10 nm < Dp < 70 nm) particles but have less impact on the burdens and lifetimes of CCN-sized particles. The models using parameterized microphysics (i.e. 10 nm and 3 nm boundaries) result in higher J10 and shorter coagulation lifetimes of ultrafine mode particles than the model with explicit dynamics (i.e. 1 nm boundary). The spatial distributions of CN10 (Dp > 10 nm) and CCN(0.2%) (i.e. CCN concentrations at 0.2% supersaturation) are moderately affected, especially CN10 predictions above ~ 700 hPa where nucleation contributes most strongly to CN10 concentrations. The lowermost layer CN10 is substantially improved with the 3 nm boundary (compared to 10 nm) in most areas. The overprediction in CN10 with the 3 nm and 10 nm boundaries can be explained by the overprediction of J10 or J3 with the parameterized microphysics possibly due to the instantaneous growth rate assumption in the survival and growth parameterization. The errors in CN10 predictions are sensitive to the choice of the lower size boundary but not to the choice of the time step applied to the microphysical processes. The spatial distribution of CCN(0.2%) with the 3 nm boundary is almost identical to that with the 1 nm boundary, but that with the 10 nm boundary can differ more than 10–40% in some areas. We found that the deviation in the 10 nm simulations is partly due to the longer time step (i.e. 1-h time step used in the 10 nm simulations compared to 10-min time step used in the benchmark simulations) but, even with the same time step, the 10 nm cutoff showed noticeably higher errors than the 3 nm cutoff. In conclusion, we generally recommend using a lower diameter boundary of 3 nm for studies focused on aerosol indirect effects but down to 1 nm boundary for studies focused on CN10 predictions or nucleation.
- Published
- 2013
- Full Text
- View/download PDF
40. Weak sensitivity of cloud condensation nuclei and the aerosol indirect effect to Criegee + SO2 chemistry
- Author
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J. R. Pierce, M. J. Evans, C. E. Scott, S. D. D'Andrea, D. K. Farmer, E. Swietlicki, and D. V. Spracklen
- Abstract
H2SO4 vapor is important for the nucleation of atmospheric aerosols and the growth of ultrafine particles to cloud condensation nuclei (CCN) sizes. Recent studies have found that reactions of stabilized Criegee intermediates (CIs, formed from the ozonolysis of alkenes) with SO2 may be an important source of H2SO4 that has been missing from atmospheric aerosol models. In this paper, we use the chemical transport model, GEOS-Chem, with the online aerosol microphysics module, TOMAS, to estimate the possible impact of CIs on present-day H2SO4, CCN, and the cloud-albedo aerosol indirect effect (AIE). We extend the standard GEOS-Chem chemistry with CI-forming reactions (ozonolysis of isoprene, methyl vinyl ketone, methacrolein, propene, and monoterpenes) from the Master Chemical Mechanism. Using a fast rate constant for CI+SO2, we find that the addition of this chemistry increases the global production of H2SO4 by 4%. H2SO4 concentrations increase by over 100% in forested tropical boundary layers and by over 10–25% in forested NH boundary layers (up to 100% in July) due to CI + SO2 chemistry, but the change is generally negligible elsewhere. The predicted changed in CCN were strongly dampened to the CI + SO2 changes in H2SO4 in these regions: less than 15% in tropical forests and less than 2% in most mid-latitude locations. The global-mean CCN change was less than 1% both in the boundary layer and the free troposphere. The associated cloud-albedo AIE change was less than 0.03 W m−2. The model global sensitivity of CCN and the AIE to CI + SO2 chemistry is significantly (approximately one order-of-magnitude) smaller than the sensitivity of CCN and AIE to other uncertain model inputs, such as nucleation mechanisms, primary emissions, SOA and deposition. Similarly, comparisons to size-distribution measurements show that uncertainties in other model parameters dominate model biases in the model-predicted size distributions. We conclude that improvement in the modeled CI + SO2 chemistry would not likely to lead to significant improvements in present-day CCN and AIE predictions.
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- 2012
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41. The effect of coal-fired power-plant SO2 and NOx control technologies on aerosol nucleation in the source plumes
- Author
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C. R. Lonsdale, R. G. Stevens, C. A. Brock, P. A. Makar, E. M. Knipping, and J. R. Pierce
- Abstract
Nucleation in coal-fired power-plant plumes can greatly contribute to particle number concentrations near source regions. The changing emissions rates of SO2 and NOx due to pollution-control technologies over recent decades may have had a significant effect on aerosol formation and growth in the plumes, with ultimate implications for climate and human health. We use the System for Atmospheric Modeling (SAM) large-eddy simulation model with the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithm to model the nucleation in plumes of coal-fired plants. We test a range of cases with varying emissions to simulate the implementation of emissions-control technologies between 1997 and 2010. For the W.A. Parish power plant (near Houston, TX) during this time period, NOx emissions were reduced by ~90%, while SO2 emissions decreased by ~30%. Increases in plume OH (due to the reduced NOx) produced enhanced SO2 oxidation and particle nucleation despite the reduction in SO2 emissions. These results suggest that NOx emissions may strongly regulate particle nucleation and growth in power-plant plumes. Comparison of model results with airborne measurements made in the W.A. Parish power-plant plume in 2000 and 2006 confirm the importance of NOx emissions on new particle formation, yet also highlight the substantial effect of background aerosol loadings on this process. A wide range of NOx and SO2 emissions were modeled to understand how they affect particle formation in the plume. Particle formation generally increases with SO2 emission, while NOx shows two different regimes: increasing particle formation with increasing NOx under low-NOx emissions and decreasing particle formation with increasing NOx under high-NOx emissions. Finally, we calculate emissions statistics of 330 coal-fired power plants in the US in 1997 and 2010, and the model results show a median decrease of 19% in particle formation ratesfrom 1997 to 2010 (whereas the W.A. Parish case study showed an increase). These results suggest that there may be important climate implications of power-plant controls due to changes in plume chemistry and microphysics. More extensive plume measurements for a range of emissions of SO2 and NOx and in varying background aerosol conditions are needed to better quantify these effects.
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- 2012
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42. Supplementary material to 'Formation and growth of nucleated particles: observational constraints on cloud condensation nuclei budgets'
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D. M. Westervelt, I. Riipinen, J. R. Pierce, W. Trivitayanurak, and P. J. Adams
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- 2012
- Full Text
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43. Geophysical Research Abstracts, Vol. 14
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I. Riipinen, J. R. Pierce, T. Yli-Juuti, D. R. Worsnop, T. Petxe4jxe4, M. Kulmala, and N. M. Donahue
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- 2012
44. Relationship Between Growth Hormone in vivo Bioactivity, the Insulin-Like Growth Factor-I System and Bone Mineral Density in Young, Physically Fit Men and Women
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W. C> Hymer, J. A. Alemany, F. Cosman, J. W. Nieves, M. J. Kennett, A. P. Tuckow, M. J. Durkot, J. R. Pierce, and B. C. Nindl
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- 2008
- Full Text
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45. Increased Dermal Sensitivity Over Paralyzed Muscle after Peak Exercise
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Jack Chisum, Lee N. Burkett, Kent Pomeroy, and J. R. Pierce
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medicine.medical_specialty ,business.industry ,Physical Therapy, Sports Therapy and Rehabilitation ,Mean age ,Thigh ,Wheelchair bound ,medicine.anatomical_structure ,Wheelchair ,Physical medicine and rehabilitation ,Statistical significance ,Anesthesia ,Chi-square test ,Medicine ,business ,Foot (unit) ,Peak exercise - Abstract
Twenty spinal injured wheelchair bound individuals were tested to peak VO2 on a wheelchair ergometer. Sixteen subjects were paraplegics (5 females, 11 males) and four were quadriplegic (2 females, 2 males). The level of injury ranged from C4-5 to L2-3. The mean age of the subjects was 29.9 years, with a mean weight of 63.66 kg. Prior to the peak VO2 and during the rest immediately after peak VO2, each subject was tested for the ability to discriminate touch over the skin of the thigh, leg, and foot. A chi square statistical technique was used to test for differences between pre- and postexercise sensitivity. The chi square was significant at the .003 level of significance. Because the increase in sensitivity was short, it was theorized that under peak exercise stress the body may recruit pathways that have been dormant, but not injured, explaining the increase in sensitivity.
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- 1990
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46. Contribution of carbonaceous aerosol to cloud condensation nuclei: processes and uncertainties evaluated with a global aerosol microphysics model
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J. R. Pierce, K. Chen, P. J. Adams, Department of Chemical Engineering, Carnegie Mellon University [Pittsburgh] (CMU), Department of Civil and Environmental Engineering [Pittsburgh], and Department of Engineering and Public Policy
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[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,010504 meteorology & atmospheric sciences ,13. Climate action ,010501 environmental sciences ,respiratory system ,01 natural sciences ,complex mixtures ,0105 earth and related environmental sciences - Abstract
This paper explores the impacts of carbonaceous aerosol on cloud condensation nuclei (CCN) concentrations in a global climate model with size-resolved aerosol microphysics. Organic matter (OM) and elemental carbon (EC) from two emissions inventories were incorporated into a preexisting model with sulfate and sea-salt aerosol. The addition of carbonaceous aerosol increased CCN(0.2%) concentrations by 65–90% in the globally averaged surface layer depending on the carbonaceous emissions inventory used. Sensitivity studies were performed to determine the relative importance of the organic "solute effect", in which CCN concentrations increase because of the added soluble carbonaceous material, versus the "seeding effect", in which CCN concentrations increase because of increased particle number concentrations. In a sensitivity study where carbonaceous aerosol was assumed to be completely insoluble, concentrations of CCN(0.2%) still increased by 40–50% globally over the no carbonaceous simulation because primary carbonaceous emissions were able to become CCN via condensation of sulfuric acid. This shows that approximately half of the contribution of carbonaceous particles to CCN comes from the "seeding effect" and half from the "solute effect". The solute effect tends to dominate more in areas where there is less inorganic aerosol than organic aerosol and the seeding effect tends to dominate in areas where is more inorganic aerosol than organic aerosol. It was found that an accurate simulation of the number size distribution is necessary to predict the CCN concentration but assuming an average chemical composition will generally give a CCN concentration within a factor of 2. If a "typical" size distribution is assumed for each species when calculating CCN, such as is done in bulk aerosol models, the mean error relative to a simulation with size resolved microphysics is on the order of 35%. Predicted values of carbonaceous aerosol mass and aerosol number were compared to observations and the model showed average errors of a factor of 3 for carbonaceous mass and a factor of 4 for total aerosol number. These errors may be reduced by improving the emission size distributions of both primary sulfate and primary carbonaceous aerosol.
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- 2007
47. Utilization management affects health care practices at Walter Reed Army Medical Center: analytical methods applied to decrease length of stay and assign appropriate level of care
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J S, Phillips, C K, Hamm, J R, Pierce, and M J, Kussman
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Databases, Factual ,District of Columbia ,Utilization Review ,Humans ,Length of Stay ,Hospitals, Military ,Delivery of Health Care ,United States - Abstract
The Department of Defense has embraced utilization management (UM) as an important tool to control and possibly decrease medical costs. Budgetary withholds have been taken by the Office of the Assistant Secretary of Defense (Health Affairs) to encourage the military services to implement UM programs. In response, Walter Reed Army Medical Center implemented a UM program along with other initiatives to effect changes in the delivery of inpatient care. This paper describes this UM program and other organizational initiatives, such as the introduction of new levels of care in an attempt to effect reductions in length of stay and unnecessary admissions. We demonstrate the use of a diversity of databases and analytical methods to quantify improved utilization and management of resources. The initiatives described significantly reduced hospital length of stay and inappropriate inpatient days. Without solid command and clinical leadership support and empowerment of the professional staffs, these significant changes and improvements could not have occurred.
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- 2000
48. Enrollment in English-as-a-second-language class as a predictor of tuberculosis infection in schoolchildren
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A V, Denison and J R, Pierce
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Schools ,Adolescent ,Tuberculin Test ,Incidence ,education ,Communication Barriers ,Hispanic or Latino ,Texas ,Humans ,Mass Screening ,Tuberculosis ,Child ,Language ,Research Article - Abstract
OBJECTIVE: To assess the rate of tuberculosis infection among Hispanic students enrolled in English-as-a-Second-Language classes compared with Hispanic and non-Hispanic students not enrolled in such classes. METHODS: Using Mantoux tuberculin skin tests, the authors screened 720 students--out of 844 eligible--in two schools with predominantly Hispanic populations. Ethnicity and enrollment in the English-as-a-Second Language classes were recorded for each student. The rate of skin test positivity was compared for students enrolled and not enrolled in these classes. RESULTS: The incidence of positive tests among Hispanic students enrolled in an English-as-a-Second-Language class was 10.6%, compared with 1.3% for Hispanic students not enrolled (relative risk 8.3, 95% confidence interval 2.92, 23.8). There was no statistically significant difference in incidence rates for non-Hispanic students (0.5%) and Hispanic students (1.3%) who were not enrolled in English-as-a-Second-Language class (relative risk 2.4, 95% confidence interval 0.27, 20.9). CONCLUSION: School-based tuberculin screening programs targeted at students enrolled in English-as-a-Second-Language classes can be effective and are not racially discriminatory.
- Published
- 1996
49. The role of the United States Army active component pediatricians in Operations Desert Shield, Desert Storm, and provide comfort
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J R, Pierce
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Male ,Refugees ,Warfare ,Surveys and Questionnaires ,Iraq ,Saudi Arabia ,Humans ,Female ,Military Medicine ,Pediatrics ,United States - Abstract
The professional activities and experiences of Army active component pediatricians deployed to Southwest Asia in support of Operations Desert Shield, Desert Storm, and Provide Comfort are reported. The 37 pediatricians who served in Southwest Asia were surveyed by a voluntary questionnaire. The survey revealed that Army pediatricians played an important role in these operations and in supporting the combat forces in Southwest Asia. They also played a critical role in caring for children displaced by the war and its aftermath in southern and northern Iraq. Pediatricians played an equally important role in continuing to provide care and support for the family members left behind in the United States and Europe.
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- 1993
50. Health care for the children of Army service members: cost of alternatives
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C W, Callahan and J R, Pierce
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Adult ,Male ,Contract Services ,Health Services ,Pediatrics ,Texas ,Health Benefit Plans, Employee ,Fees, Medical ,Military Personnel ,Costs and Cost Analysis ,Humans ,Female ,Child ,Military Medicine - Abstract
The United States Army is committed to providing quality health care for active-duty service members, their dependents, and retired service members. Historically, the Army has never had enough active-duty physicians to provide care for all its beneficiaries. Alternatives utilizing civilian health care providers have been established to provide the balance of the medical services. In this review, the cost of each of the civilian health care providers in the Ft. Hood, Texas area is compared to that of the Army pediatrician. The Army pediatrician proves to be the least expensive of the health care providers.
- Published
- 1991
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