Search

The Arctic is warming at more than twice the rate of the global average. This warming is influenced by clouds, which modulate the solar and terrestrial radiative fluxes and, thus, determine the surface energy budget. However, the interactions among clouds, aerosols, and radiative fluxes in the Arctic are still poorly understood. To address these uncertainties, the Ny-Ålesund Aerosol Cloud Experiment (NASCENT) study was conducted from September 2019 to August 2020 in Ny-Ålesund, Svalbard. The campaign’s primary goal was to elucidate the life cycle of aerosols in the Arctic and to determine how they modulate cloud properties throughout the year. In situ and remote sensing observations were taken on the ground at sea level, at a mountaintop station, and with a tethered balloon system. An overview of the meteorological and the main aerosol seasonality encountered during the NASCENT year is introduced, followed by a presentation of first scientific highlights. In particular, we present new findings on aerosol physicochemical and molecular properties. Further, the role of cloud droplet activation and ice crystal nucleation in the formation and persistence of mixed-phase clouds, and the occurrence of secondary ice processes, are discussed and compared to the representation of cloud processes within the regional Weather Research and Forecasting Model. The paper concludes with research questions that are to be addressed in upcoming NASCENT publications.

Acidity profoundly affects almost every aspect that shapes the composition of ambient particles and their environmental impact. Thermodynamic analysis of gas-particle composition datasets offers robust estimates of acidity, but they are not available for long periods of time. Fog composition datasets, however, are available for many decades; we develop a thermodynamic analysis to estimate the ammonia in equilibrium with fog water and to infer the pre-fog aerosol pH starting from fog chemical composition and pH. The acidity values from the new method agree with the results of thermodynamic analysis of the available gas-particle composition data. Applying the new method to historical (25 years) fog water composition at the rural station of San Pietro Capofiume (SPC) in the Po Valley (Italy) suggests that the aerosol has been mildly acidic, with its pH decreasing by 0.5–1.5 pH units over the last decades. The observed pH of the fog water also increased 1 unit over the same period. Analysis of the simulated aerosol pH reveals that the aerosol acidity trend is driven by a decrease in aerosol precursor concentrations, and changes in temperature and relative humidity. Currently, NOx controls would be most effective for PM2.5 reduction in the Po valley both during summer and winter. In the future, however, seasonal transitions to the NH3-sensitive region may occur, meaning that the NH3 reduction policy may become increasingly necessary., Paglione, M., Decesari, S., Rinaldi, M., Tarozzi, L., Manarini, F., Gilardoni, S., Facchini, M. C., Fuzzi, S., Bacco, D., Trentini, A., Pandis S. N., and Nenes A. : Historical Changes in Seasonal Aerosol Acidity in the Po Valley (Italy) as Inferred from Fog Water and Aerosol Measurements, Environ. Sci. Technol., May 17, 2021, https://doi.org/10.1021/acs.est.1c00651

Society of Environmental Toxicology and Chemistry (SETAC) Europe 30th Annual Meeting, 3-7 May 2020, Blooms of the benthic dinoflagellate Ostreopsis cf. ovata have been related to mild but acute respiratory symptoms on people exposed to marine aerosols in some Mediterranean and Brazilian beaches. These disorders have been attributed -but not proven yet- to palytoxin (PLTX) analogues (ovatoxins -OVTX- and isobaric palytoxin -isoPLTX-) produced by Ostreopsis. However, these compounds have been seldom found in the aerosol and when detected it was not associated to human health impacts. To shed light on the mechanisms of toxin production and transfer to the atmosphere five laboratory experiments were run using an aerosol generation tank with microbial communities obtained during the peak of an Ostreopsis bloom. Seawater and aerosol samples were analyzed for i) toxin concentration (with an UHPLC system coupled to a Q-Exactive Orbitrap Fourier-Transform Mass Spectrometer (FTMS) equipped with a heated-electrospray ionization source (H-ESI) operating in positive ion mode using a Hypersil GOLDTM C18 column (100 mm x 2.1 mm id., 1.9 µm particle size) packed with totally-porous silica particles, under a gradient elution of acetonitrile:water (0.1% formic acid) mobile phase), and ii) offline spectroscopic analysis performed by nuclear magnetic resonance (NMR). Toxins were detected in seawater samples and in atmospheric aerosol generated in all experiments. Unexpectedly, higher toxin concentrations (49-69 pg·Lair¿1) were found in the aerosols generated by bubbling relatively low Ostreopsis cells abundances and toxins in the water (respectively, ca. 105 cells·L¿1, 4 x 106 pg·Lwater¿1), compared to the ones (3-4 pg·Lair¿1) obtained on higher biomass abundance experiments (1 x 106 cells·L¿1 and 2 x 108 pg·Lwater¿1, respectively). The toxin profile in the air contained OVTX-a and b only, while other forms (OVTX-c, d, e and isoPLTX) were also present in the water. Moreover, NMR analysis showed different composition of the particulate organic carbon in the water (Ostreopsis cells and accompanying microbiota) and bubble bursting aerosols, suggesting selectively transfers of organic compounds from seawater into the atmosphere. High foam content was also observed in the water surface of the tank. Overall, these experiments constitute a first step to understand the ecophysiogical microalgae responses to bubble bursting as well as the complex air-sea dynamics in the surface microlayer likely regulating aerosol production and diffusion of the marine toxins in the atmosphere

This report contains a guide and a European harmonised protocol prepared within the framework of the Working Group 3 on source apportionment of the Forum for Air Quality Modelling in Europe (FAIRMODE). It has been initiated as a JRC initiative for the harmonisation of source apportionment with receptor models, in collaboration with FAIRMODE as well as with the European networks in the field of air quality measurements (AQUILA), and then further with the European COLOSSAL (Chemical On-Line cOmpoSition and Source Apportionment of fine aerosol) COST action. The JRC initiative also included a review of the methodologies used in Europe for source identification and intercomparison exercises for the quantitative assessment of the performance of source apportionment models. The document, drafted and then revised by a group of international experts, is organised following the logical sequence of steps to be carried out in a source apportionment study. Sections with increasing levels of complexity make it accessible to readers with different degrees of familiarity with this topic, from air quality managers to air pollution experts and modellers. It has been conceived as a reference document that includes tutorials, technical recommendations and check lists.

This report contains a guide and a European harmonised protocol prepared within the framework of the Working Group 3 on source apportionment of the Forum for Air Quality Modelling in Europe (FAIRMODE). It has been initiated as a JRC initiative for the harmonisation of source apportionment with receptor models, in collaboration with FAIRMODE as well as with the European networks in the field of air quality measurements (AQUILA), and then further with the European COLOSSAL (Chemical On-Line cOmpoSition and Source Apportionment of fine aerosol) COST action. The JRC initiative also included a review of the methodologies used in Europe for source identification and intercomparison exercises for the quantitative assessment of the performance of source apportionment models. The document, drafted and then revised by a group of international experts, is organised following the logical sequence of steps to be carried out in a source apportionment study. Sections with increasing levels of complexity make it accessible to readers with different degrees of familiarity with this topic, from air quality managers to air pollution experts and modellers. It has been conceived as a reference document that includes tutorials, technical recommendations and check lists., JRC.C.5-Air and Climate

POLAR 2018 - XXXV SCAR Meetings and SCAR/IASC Open Science Conference, 19-23 June 2018, Davos, Switzerland, Climate warming affects the development and distribution of sea ice south of the Polar Front around Antarctica and its associated ecosystems, but at present the evidence of feedbacks on climate through ecosystem-derived changes in the atmosphere is sparse. The PEGASO cruise visited the Antarctic region of the South Orkney Islands at the northern edge of the Weddell Sea, and the Subantarctic region of the South Georgia Island, in summer 2015. Each region was studied intensively in lagrangian mode over a few days and diel cycles. Oceanic measurements of plankton abundance, diversity, activity and physiology, plus organic matter characteristics, organic volatile compounds (dimethylsulfide, isoprene, halomethanes) and nutrient concentrations, were compared with simultaneous atmospheric measurements of aerosol numbers, size and composition. Samples of surface seawater and melted sea ice were bubbled in an aerosol-generation tank and the characteristics of the sprayed aerosol were monitored. This integrated study allowed to link phytoplankton bloom stages and the emission of aerosol-forming particulate and gaseous substances. For instance, we observed that the microbiota of sea ice and sea ice-influenced ocean are a previously unknown significant source of atmospheric organic nitrogen, including low molecular weight alkyl-amines. Given the keystone role of nitrogen, sulfur, carbon and iodine compounds in aerosol formation, growth and neutralization, our findings call for greater chemical and source diversity in the modeling efforts linking the marine ecosystem to aerosol-mediated climate effects in the Southern Ocean

POLAR 2018 - XXXV SCAR Meetings and SCAR/IASC Open Science Conference, 19-23 June 2018, Davos, Switzerland.-- 1 page, Climate warming affects the development and distribution of sea ice around Antarctica and its associated ecosystems, but at present the evidence of feedbacks on climate through ecosystem-derived changes in the atmosphere is sparse. The PEGASO cruise visited the Antarctic region of the South Orkney Islands at the northern edge of the Weddell Sea, and the Subantarctic region of the South Georgia Island, in summer 2015. Each region was studied intensively in lagrangian mode over a few days and diel cycles. Oceanic measurements of plankton abundance, diversity, activity and physiology, plus organic matter characteristics, aerosol-forming organic volatile compounds (dimethylsulfide, methylamines, isoprene, halomethanes) and nutrient concentrations, were compared with simultaneous atmospheric measurements of aerosol numbers, size and composition. Samples of surface seawater and melted sea ice were bubbled in an aerosol-generation tank and the characteristics of the sprayed aerosol were monitored. This integrated study allowed to link phytoplankton bloom stages and the emission of aerosol-forming particulate and gaseous substances. Our findings call for greater chemical and source diversity in the modeling efforts linking the marine ecosystem to aerosol-mediated climate effects in the Southern Ocean

Not available

Atmospheric organic aerosols are generally classified as primary and secondary (POA and SOA) according to their formation processes. An actual separation, however, is challenging when the timescales of emission and gas-to-particle formation overlap. The presence of SOA formation in biomass burning plumes leads to scientific questions about whether the oxidized fraction of biomass burning aerosol is rather of secondary or primary origin, as some studies would suggest, and about the chemical compositions of oxidized biomass burning POA and SOA. In this study, we apply nuclear magnetic resonance (NMR) spectroscopy to investigate the functional group composition of fresh and aged biomass burning aerosols during an intensive field campaign in the Po Valley, Italy. The campaign was part of the EUCAARI project and was held at the rural station of San Pietro Capofiume in spring 2008. Factor analysis applied to the set of NMR spectra was used to apportion the wood burning contribution and other organic carbon (OC) source contributions, including aliphatic amines. Our NMR results, referred to the polar, water-soluble fraction of OC, show that fresh wood burning particles are composed of polyols and aromatic compounds, with a sharp resemblance to wood burning POA produced in wood stoves, while aged samples are clearly depleted of alcohols and are enriched in aliphatic acids with a smaller contribution of aromatic compounds. The comparison with biomass burning organic aerosols (BBOA) determined by high-resolution aerosol mass spectrometry (HR-TOF-AMS) at the site shows only a partial overlap between NMR BB-POA and AMS BBOA, which can be explained by either the inability of BBOA to capture all BB-POA composition, especially the alcohol fraction, or the fact that BBOA account for insoluble organic compounds unmeasured by the NMR. Therefore, an unambiguous composition for biomass burning POA could not be derived from this study, with NMR analysis indicating a higher O/C ratio compared to that measured for AMS BBOA. The comparison between the two techniques substantially improves when adding factors tracing possible contributions from biomass burning SOA, showing that the operational definitions of biomass burning organic aerosols are more consistent between techniques when including more factors tracing chemical classes over a range of oxidation levels. Overall, the non-fossil total carbon fraction was 50-57%, depending on the assumptions about the 14C content of non-fossil carbon, and the fraction of organic carbon estimated to be oxidized organic aerosol (OOA) from HR-TOF-AMS measurements was 73-100% modern

The light-absorbing properties of water-soluble brown carbon (WS-BrC) and methanol-soluble brown carbon (MeS-BrC) were studied in PM10 aerosols collected at the "Nepal Climate Observatory-Pyramid" (NCO-P) station (5079m above sea level) during the period 2013-2014. The light absorption coefficients of WS-BrC and MeS-BrC were the highest during the premonsoon season and the lowest during monsoon. MeS-BrC absorbs about 2 times higher at 365nm and about 3 times more at 550nm compared to WS-BrC. The mass absorption cross section (MAC) of WS-BrC measured at 365nm is similar to that observed previously at South Asian low-altitude sites. Fractional solar radiation absorption by BrC compared to BC considering the full solar spectrum showed that WS-BrC absorbs 4 +/- 1% and MeS-BrC absorbs 9 +/- 2% compared to BC at NCO-P. Such ratios become 8 +/- 1% (for WS-BrC respect to BC) and 17 +/- 5% (for MeS-BrC respect to BC) when accounting for correction factors proposed by previous studies to convert absorption coefficients in bulk solutions into light absorption by accumulation mode aerosol particles. These results confirm the importance of BrC in contributing to light-absorbing aerosols in this region of the world. However, the BrC absorption at 550nm appears small compared to that of BC (1-5%, or 3-9% with conversion factors), and it is lower compared to global model estimates constrained by Aerosol Robotic Network observations. Finally, our study provides no clear evidence of a change in the fractional contribution of BrC with respect to BC to light absorption in the middle troposphere respect to the Indo-Gangetic plain boundary layer.

The aerosol size-segregated chemical composition was analyzed at an urban (Bologna) and a rural (San Pietro Capofiume) site in the Po Valley, Italy, during June and July 2012, by ion-chromatography (major water-soluble ions and organic acids) and evolved gas analysis (total and water-soluble carbon), to investigate sources and mechanisms of secondary aerosol formation during the summer. A significant enhancement of secondary organic and inorganic aerosol mass was observed under anticyclonic conditions with recirculation of planetary boundary layer air but with substantial differences between the urban and the rural site. The data analysis, including a principal component analysis (PCA) on the size-resolved dataset of chemical concentrations, indicated that the photochemical oxidation of inorganic and organic gaseous precursors was an important mechanism of secondary aerosol formation at both sites. In addition, at the rural site a second formation process, explaining the largest fraction (22 %) of the total variance, was active at nighttime, especially under stagnant conditions. Nocturnal chemistry in the rural Po Valley was associated with the formation of ammonium nitrate in large accumulation-mode (0.42–1.2 µm) aerosols favored by local thermodynamic conditions (higher relative humidity and lower temperature compared to the urban site). Nocturnal concentrations of fine nitrate were, in fact, on average 5 times higher at the rural site than in Bologna. The water uptake by this highly hygroscopic compound under high RH conditions provided the medium for increased nocturnal aerosol uptake of water-soluble organic gases and possibly also for aqueous chemistry, as revealed by the shifting of peak concentrations of secondary compounds (water-soluble organic carbon (WSOC) and sulfate) toward the large accumulation mode (0.42–1.2 µm). Contrarily, the diurnal production of WSOC (proxy for secondary organic aerosol) by photochemistry was similar at the two sites but mostly affected the small accumulation mode of particles (0.14–0.42 µm) in Bologna, while a shift to larger accumulation mode was observed at the rural site. A significant increment in carbonaceous aerosol concentration (for both WSOC and water-insoluble carbon) at the urban site was recorded mainly in the quasi-ultrafine fraction (size range 0.05–0.14 µm), indicating a direct influence of traffic emissions on the mass concentrations of this range of particles.