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Synthesizing soft polymers with uncommon architectural elements is critical for enhancing our understanding of fundamental structure–property relationships in macromolecules. Terpenoid materials are interesting candidates for addressing this grand challenge, as their constituent monomers can exhibit a diverse array of structural and functional groups. Moreover, these biologically‐derived materials can potentially expand the sphere of knowledge surrounding trends in related petrochemically‐derived polymers. For example, vinyl‐addition copolymers of norbornene and acyclic olefins can exhibit predictable properties (e.g., linear changes in Tgas a function of composition). Due to synthetic limitations, however, it is not well understood if other rigid carbocycles engender similar behavior in a range of copolymers. As numerous terpene scaffolds display rigid motifs (such as pinane systems), terpenoid polymers are uniquely positioned to address this deficiency. Here, we report the synthesis and characterization of terpenoid copolymers (both statistical and block) with systematically tailored compositions of pinene‐based comonomers. We found that the pinane core (which is a constitutional isomer of norbornene) appears to promote ideal behavior with regard to bulk thermal properties of statistical copolymers, which mirrors the behavior of norbornene‐based systems. We also found that block copolymers exhibited thermomechanical properties that were highly tunable (and apparently correlated to carbocycle composition).

Carbonaceous emissions from wildfires are a dynamic mixture of gases and particles that have important impacts on air quality and climate. Emissions that feed atmospheric models are estimated using burned area and fire radiative power (FRP) methods that rely on satellite products. These approaches show wide variability and have large uncertainties, and their accuracy is challenging to evaluate due to limited aircraft and ground measurements. Here, we present a novel method to estimate fire plume-integrated total carbon and speciated emission rates using a unique combination of lidar remote sensing aerosol extinction profiles and in situ measured carbon constituents. We show strong agreement between these aircraft-derived emission rates of total carbon and a detailed burned area-based inventory that distributes carbon emissions in time using Geostationary Operational Environmental Satellite FRP observations (Fuel2Fire inventory, slope = 1.33 ± 0.04, r2= 0.93, and RMSE = 0.27). Other more commonly used inventories strongly correlate with aircraft-derived emissions but have wide-ranging over- and under-predictions. A strong correlation is found between carbon monoxide emissions estimated in situ with those derived from the TROPOspheric Monitoring Instrument (TROPOMI) for five wildfires with coincident sampling windows (slope = 0.99 ± 0.18; bias = 28.5%). Smoke emission coefficients (g MJ–1) enable direct estimations of primary gas and aerosol emissions from satellite FRP observations, and we derive these values for many compounds emitted by temperate forest fuels, including several previously unreported species.

Synthetic methods that edit soft polymer backbones are critical technologies for tailoring the structures and properties of macromolecules. Developing strategies that leverage underexplored reaction manifolds are vital for accessing new chemical (and functional) space in soft materials. Here, we report a mild electrochemical approach that enables both degradation and functionalization of synthetic polymers. We found that bulk electrolysis (under either homogeneous or heterogeneous conditions) promoted facile, chemoselective chain scission in a variety of olefin-containing materials. Polymer degradation could also be coupled with functionalization (e.g., azidation) to afford new species that could serve as macromonomers.

Agricultural and prescribed burning activities emit large amounts of trace gases and aerosols on regional to global scales. We present a compilation of emission factors (EFs) and emission ratios from the eastern portion of the Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) campaign in 2019 in the United States, which sampled burning of crop residues and other prescribed fire fuels. FIREX‐AQ provided comprehensive chemical characterization of 53 crop residue and 22 prescribed fires. Crop residues burned at different modified combustion efficiencies (MCE), with corn residue burning at higher MCE than other fuel types. Prescribed fires burned at lower MCE (<0.90) which is typical, while grasslands burned at lower MCE (0.90) than normally observed due to moist, green, growing season fuels. Most non‐methane volatile organic compounds (NMVOCs) were significantly anticorrelated with MCE except for ethanol and NMVOCs that were measured with less certainty. We identified 23 species where crop residue fires differed by more than 50% from prescribed fires at the same MCE. Crop residue EFs were greater for species related to agricultural chemical use and fuel composition as well as oxygenated NMVOCs possibly due to the presence of metals such as potassium. Prescribed EFs were greater for monoterpenes (5×). FIREX‐AQ crop residue average EFs generally agreed with the previous agricultural fire study in the US but had large disagreements with global compilations. FIREX‐AQ observations show the importance of regionally‐specific and fuel‐specific EFs as first steps to reduce uncertainty in modeling the air quality impacts of fire emissions. Crop residue and prescribed fires emit pollution that impacts air quality. FIREX‐AQ provided observations of these emissions to better characterize their variability with a detailed set of chemical observations. These observations showed significant differences in the emissions from burning different crops (corn, rice, soybean, wheat) compared to other prescribed fires or grasslands that may be due to differences in the fuel composition, the use of agricultural chemicals, and moisture levels. Overall, FIREX‐AQ observations for crop residue fires compared better with previous results in the region than with globally averaged information. The campaign observed even greater variability across EFs than previous studies, suggesting that new methods must be developed to take this into account to improve predictions of the air quality impacts of burning these fuels. Corn residue burned at higher modified combustion efficiency than rice or soybean residueImpacts of fire emissions >6 hr downwind on OH reactivity will be more influenced by species that are less important at the sourceEmission factors from crop residue fires agreed better with previous results from the same region than with global compilations Corn residue burned at higher modified combustion efficiency than rice or soybean residue Impacts of fire emissions >6 hr downwind on OH reactivity will be more influenced by species that are less important at the source Emission factors from crop residue fires agreed better with previous results from the same region than with global compilations

Deep convective transport of gaseous precursors to ozone (O3) and aerosols to the upper troposphere is affected by liquid phase and mixed‐phase scavenging, entrainment of free tropospheric air and aqueous chemistry. The contributions of these processes are examined using aircraft measurements obtained in storm inflow and outflow during the 2012 Deep Convective Clouds and Chemistry (DC3) experiment combined with high‐resolution (dx≤3 km) WRF‐Chem simulations of a severe storm, an air mass storm, and a mesoscale convective system (MCS). The simulation results for the MCS suggest that formaldehyde (CH2O) is not retained in ice when cloud water freezes, in agreement with previous studies of the severe storm. By analyzing WRF‐Chem trajectories, the effects of scavenging, entrainment, and aqueous chemistry on outflow mixing ratios of CH2O, methyl hydroperoxide (CH3OOH), and hydrogen peroxide (H2O2) are quantified. Liquid phase microphysical scavenging was the dominant process reducing CH2O and H2O2outflow mixing ratios in all three storms. Aqueous chemistry did not significantly affect outflow mixing ratios of all three species. In the severe storm and MCS, the higher than expected reductions in CH3OOH mixing ratios in the storm cores were primarily due to entrainment of low‐background CH3OOH. In the air mass storm, lower CH3OOH and H2O2scavenging efficiencies (SEs) than in the MCS were partly due to entrainment of higher background CH3OOH and H2O2. Overestimated rain and hail production in WRF‐Chem reduces the confidence in ice retention fraction values determined for the peroxides and CH2O. Methyl hydroperoxide mixing ratios are decreased mainly by entrainment and liquid phase and mixed‐phase scavengingHydrogen peroxide and formaldehyde mixing ratios affected more by liquid phase scavenging than by entrainment or aqueous chemistryOverestimated rain/hail production in WRF‐Chem reduces confidence in ice retention fraction values determined for peroxides and formaldehyde

Strong correlations of O3‐CH2O, O3‐CO and CO‐CH2O were observed during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER‐AQ) aircraft experiment in July 2011 over the Washington‐Baltimore area. The linear regression slopes of observed O3‐CH2O, O3‐CO, and CO‐CH2O do not vary significantly with time (11 a.m. to 4 p.m.) or altitude in the boundary layer. These observed relationships are simulated well by a regional chemical transport model. Using tagged‐tracer simulations, we find that biogenic isoprene oxidation makes the largest contribution to the regression slope of O3‐CH2O across much of the eastern United States, providing a good indicator for O3enhanced by biogenic isoprene oxidation. In contrast, the regression slope of O3‐CO is controlled by both anthropogenic and biogenic emissions. Therefore, we use the CO‐CH2O relationship to separate biogenic from anthropogenic contributions to CO. By combining these regressions, we can track the contributions to surface O3by anthropogenic and biogenic factors and build a fast‐response ozone estimator using near‐surface CH2O and CO concentrations as inputs. We examine the quality of O3estimator by increasing or decreasing anthropogenic emissions by up to 50%. The estimated O3distribution is in reasonably good agreement with the full‐model simulations (R2> 0.77 in the range of −30% to +50% of anthropogenic emissions). The analysis provides the basis for using high‐quality geostationary satellites with UV, thermal infrared, or near‐infrared instruments for observing CH2O and CO to improve surface O3distribution monitoring. The estimation model can also be applied to derive observation‐derived regional metrics to evaluate and improve full‐fledged 3‐D air quality models. Observations show robust correlations and consistent linear regression slopes of O3‐CH2O, O3‐CO and CO‐CH2OBiogenic isoprene oxidation makes the largest contribution to the regression slope of O3‐CH2O across much of the eastern United StatesWe build a fast‐response O3estimator using input near‐surface CH2O and CO concentrations to improve surface O3distribution monitoring

The San Joaquin Valley (SJV) of California experiences high concentrations of particulate matter NH4NO3during episodes of meteorological stagnation in winter. A rich data set of observations related to NH4NO3formation was acquired during multiple periods of elevated NH4NO3during the Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER‐AQ) field campaign in SJV in January and February 2013. Here NH4NO3is simulated during the SJV DISCOVER‐AQ study period with the Community Multiscale Air Quality (CMAQ) model, diagnostic model evaluation is performed using the DISCOVER‐AQ data set, and integrated reaction rate analysis is used to quantify HNO3production rates. Simulated NO3−generally agrees well with routine monitoring of 24‐hr average NO3−, but comparisons with hourly average NO3−measurements in Fresno revealed differences at higher time resolution. Predictions of gas‐particle partitioning of total nitrate (HNO3+ NO3−) and NHx (NH3+ NH4+) generally agree well with measurements in Fresno, although partitioning of total nitrate to HNO3is sometimes overestimated at low relative humidity in afternoon. Gas‐particle partitioning results indicate that NH4NO3formation is limited by HNO3availability in both the model and ambient. NH3mixing ratios are underestimated, particularly in areas with large agricultural activity, and additional work on the spatial allocation of NH3emissions is warranted. During a period of elevated NH4NO3, the model predicted that the OH + NO2pathway contributed 46% to total HNO3production in SJV and the N2O5heterogeneous hydrolysis pathway contributed 54%. The relative importance of the OH + NO2pathway for HNO3production is predicted to increase as NOx emissions decrease. NH4NO3formation is limited by HNO3availability in both the model and ambient based on gas‐particle partitioning resultsThe OH + NO2pathway contributed 46% to modeled HNO3production in SJV, and the N2O5heterogeneous hydrolysis pathway contributed 54%The relative importance of the OH + NO2pathway for HNO3production is predicted to increase as NOx emissions decrease

Modeled source attribution information from the Community Multiscale Air Quality model was coupled with ambient data from the 2011 Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality Baltimore field study. We assess source contributions and evaluate the utility of using aircraft measured CO and NOyrelationships to constrain emission inventories. We derive ambient and modeled ΔCO:ΔNOyratios that have previously been interpreted to represent CO:NOyratios in emissions from local sources. Modeled and measured ΔCO:ΔNOyare similar; however, measured ΔCO:ΔNOyhas much more daily variability than modeled values. Sector‐based tagging shows that regional transport, on‐road gasoline vehicles, and nonroad equipment are the major contributors to modeled CO mixing ratios in the Baltimore area. In addition to those sources, on‐road diesel vehicles, soil emissions, and power plants also contribute substantially to modeled NOyin the area. The sector mix is important because emitted CO:NOxratios vary by several orders of magnitude among the emission sources. The model‐predicted gasoline/diesel split remains constant across all measurement locations in this study. Comparison of ΔCO:ΔNOyto emitted CO:NOyis challenged by ambient and modeled evidence that free tropospheric entrainment, and atmospheric processing elevates ambient ΔCO:ΔNOyabove emitted ratios. Specifically, modeled ΔCO:ΔNOyfrom tagged mobile source emissions is enhanced 5–50% above the emitted ratios at times and locations of aircraft measurements. We also find a correlation between ambient formaldehyde concentrations and measured ΔCO:ΔNOysuggesting that secondary CO formation plays a role in these elevated ratios. This analysis suggests that ambient urban daytime ΔCO:ΔNOyvalues are not reflective of emitted ratios from individual sources. Modeling and ambient analysis suggest that atmospheric processing can impact the ΔCO:ΔNOymeasured by aircraft over the Baltimore regionFor about one third of measurements, NOyvalues derived from different instruments lead to observed ΔCO:ΔNOythat are statistically inconsistentWe urge caution in using ΔCO:ΔNOyderived from aircraft measurement to quantify emissions errors from specific sources

Satellite‐based measurements of the column CH2O/NO2ratio have previously been used to estimate near‐surface ozone (O3) sensitivity (i.e., NOxor VOC limited), and the forthcoming launch of air quality‐focused geostationary satellites provides a catalyst for reevaluating the ability of satellite‐measured CH2O/NO2to be used in this manner. In this study, we use a 0‐D photochemical box model to evaluate O3sensitivity and find that the relative rate of radical termination from radical‐radical interactions to radical‐NOxinteractions (referred to as LROx/LNOx) provides a good indicator of maximum O3production along NOxridgelines. Using airborne measurements from NASA's Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relative to Air Quality (DISCOVER‐AQ) deployments in Colorado, Maryland, and Houston, we show that in situ measurements of CH2O/NO2can be used to indicate O3sensitivity, but there is an important “transition/ambiguous” range whereby CH2O/NO2fails to categorize O3sensitivity, and the range and span of this transition/ambiguous range varies regionally. Then, we apply these findings to aircraft‐derived column density measurements from DISCOVER‐AQ and find that inhomogeneities in vertical mixing in the lower troposphere further degrades the ability of column CH2O/NO2to indicate near‐surface O3sensitivity (i.e., the transition/ambiguous range is much larger than indicated by in situ data alone), and we hypothesize that the global transition/ambiguous range is sufficiently large to make the column CH2O/NO2ratio unuseful for classifying near‐surface O3sensitivity. Lastly, we present a case study from DISCOVER‐AQ‐Houston that suggests that O3sensitivity on exceedance days may be substantially different than on nonexceedance days (which may be observable from space) and explore the diurnal evolution of O3sensitivity, O3production, and the column CH2O/NO2ratio. The results of these studies suggest that although satellite measurements of CH2O/NO2alone may not be sufficient for accurately classifying near‐surface O3sensitivity, new techniques offered by geostationary platforms may nonetheless provide methods for using space‐based measurements to develop O3mitigation strategies. In situ measurements of the CH2O/NO2ratio are a good indicator of ozone sensitivity but are spatially limited in their coverageColumn measurements of CH2O/NO2are a poor indicator of near‐surface ozone sensitivity due to uneven vertical mixing in the lower troposphereLong‐ and short‐term observations of changes in column CH2O/NO2ratios may still provide useful information about the relative importance of O3precursors

We examine wet scavenging of soluble trace gases in storms observed during the Deep Convective Clouds and Chemistry (DC3) field campaign. We conduct high‐resolution simulations with the Weather Research and Forecasting model with Chemistry (WRF‐Chem) of a severe storm in Oklahoma. The model represents well the storm location, size, and structure as compared with Next Generation Weather Radar reflectivity, and simulated CO transport is consistent with aircraft observations. Scavenging efficiencies (SEs) between inflow and outflow of soluble species are calculated from aircraft measurements and model simulations. Using a simple wet scavenging scheme, we simulate the SE of each soluble species within the error bars of the observations. The simulated SEs of all species except nitric acid (HNO3) are highly sensitive to the values specified for the fractions retained in ice when cloud water freezes. To reproduce the observations, we must assume zero ice retention for formaldehyde (CH2O) and hydrogen peroxide (H2O2) and complete retention for methyl hydrogen peroxide (CH3OOH) and sulfur dioxide (SO2), likely to compensate for the lack of aqueous chemistry in the model. We then compare scavenging efficiencies among storms that formed in Alabama and northeast Colorado and the Oklahoma storm. Significant differences in SEs are seen among storms and species. More scavenging of HNO3and less removal of CH3OOH are seen in storms with higher maximum flash rates, an indication of more graupel mass. Graupel is associated with mixed‐phase scavenging and lightning production of nitrogen oxides (NOx), processes that may explain the observed differences in HNO3and CH3OOH scavenging. Observed deep convective scavenging efficiencies simulated by simple schemeSimulated scavenging efficiencies highly sensitive to ice retention fractionScavenging efficiencies vary among storms with different microphysics

Formaldehyde column density (ΩHCHO) showed a potentially useful correlation with surface ozone during the LISTOS campaign on Long Island Sound and the KORUS‐AQ campaign in Seoul, South Korea. This builds on previous work that identified this relationship from in situ aircraft observations with similar findings for ground‐based and airborne remote sensing of ΩHCHO. In the Long Island Sound region, ΩHCHO and surface ozone exhibited strong temporal (r2= 0.66) and spatial (r2= 0.73) correlation. The temporal variability in ΩHCHO (∼1 Dobson units [DU]) was larger than the range in the spatial average (∼0.1 DU). The spatial average is most useful for informing ozone monitoring strategies, demonstrating the challenge in using ΩHCHO satellite data sets for this purpose. In Seoul, high levels of NO2resulted in Oxbetter correlating with ΩHCHO than surface ozone due to titration effects. The ΩHCHO–Oxrelationship may therefore reflect the sum of surface ozone and related photochemical oxidants, relevant to air quality standards set to regulate this quantity such as the U.S. EPA National Ambient Air Quality Standard (NAAQS). The relationship of ΩHCHO to Oxshifted in Seoul during the campaign demonstrating the need to evaluate this relationship over longer time periods. With sufficient precision in future satellite retrievals, ΩHCHO observations could be useful for evaluating the adequacy of surface air quality monitoring strategies. Surface ozone is hazardous to human health and the environment. Space‐based monitoring techniques provide the opportunity to improve our knowledge of regional surface ozone pollution. Ozone measurements from space have limited ability to detect surface concentrations. Observations of column formaldehyde, a trace gas produced during production of surface ozone, are correlated with surface ozone and related pollutants. This relationship points to a potential use of satellite observations for identifying regions of harmful ozone concentrations to complement sparse surface monitoring networks. Column formaldehyde (ΩHCHO) is related spatially and temporally with surface ozone during the LISTOS and KORUS‐AQ field campaignsΩHCHO better correlates with Ox(≡ozone + NO2) which more broadly represents ozone and related photochemical oxidantsSatellite ΩHCHO could be an indicator of ozone and related photochemical oxidants and inform air quality monitoring strategies Column formaldehyde (ΩHCHO) is related spatially and temporally with surface ozone during the LISTOS and KORUS‐AQ field campaigns ΩHCHO better correlates with Ox(≡ozone + NO2) which more broadly represents ozone and related photochemical oxidants Satellite ΩHCHO could be an indicator of ozone and related photochemical oxidants and inform air quality monitoring strategies

Chlorine radicals can function as a strong atmospheric oxidant, particularly in polar regions, where levels of hydroxyl radicals are low. In the atmosphere, chlorine radicals expedite the degradation of methane and tropospheric ozone, and the oxidation of mercury to more toxic forms. Here we present direct measurements of molecular chlorine levels in the Arctic marine boundary layer in Barrow, Alaska, collected in the spring of 2009 over a six-week period using chemical ionization mass spectrometry. We report high levels of molecular chlorine, of up to 400 pptv. Concentrations peaked in the early morning and late afternoon, and fell to near-zero levels at night. Average daytime molecular chlorine levels were correlated with ozone concentrations, suggesting that sunlight and ozone are required for molecular chlorine formation. Using a time-dependent box model, we estimate that the chlorine radicals produced from the photolysis of molecular chlorine oxidized more methane than hydroxyl radicals, on average, and enhanced the abundance of short-lived peroxy radicals. Elevated hydroperoxyl radical levels, in turn, promoted the formation of hypobromous acid, which catalyses mercury oxidation and the breakdown of tropospheric ozone. We therefore suggest that molecular chlorine exerts a significant effect on the atmospheric chemistry of the Arctic.

Reactive chlorine and bromine species emitted from snow and aerosols can significantly alter the oxidative capacity of the polar boundary layer. However, halogen production mechanisms from snow remain highly uncertain, making it difficult for most models to include descriptions of halogen snow emissions and to understand the impact on atmospheric chemistry. We investigate the influence of Arctic halogen emissions from snow on boundary layer oxidation processes using a one‐dimensional atmospheric chemistry and transport model (PACT‐1D). To understand the combined impact of snow emissions and boundary layer dynamics on atmospheric chemistry, we model Cl2and Br2primary emissions from snow and include heterogeneous recycling of halogens on both snow and aerosols. We focus on a 2‐day case study from the 2009 Ocean‐Atmosphere‐Sea Ice‐Snowpack campaign at Utqiaġvik, Alaska. The model reproduces both the diurnal cycle and high quantity of Cl2observed, along with the measured concentrations of Br2, BrO, and HOBr. Due to the combined effects of emissions, recycling, vertical mixing, and atmospheric chemistry, reactive chlorine is typically confined to the lowest 15 m of the atmosphere, while bromine can impact chemistry up to and above the surface inversion height. Upon including halogen emissions and recycling, the concentration of HOx(HOx= OH + HO2) at the surface increases by as much as a factor of 30 at mid‐day. The change in HOxdue to halogen chemistry, as well as chlorine atoms derived from snow emissions, significantly reduce volatile organic compound lifetimes within a shallow layer near the surface. A combination of factors including snow emissions, vertical mixing, and atmospheric chemistry explain surface Arctic halogen observationsSnow emissions of halogens impact atmospheric chemistry within a shallow layer near the surfaceSurface HOxconcentrations are increased by up to a factor of 30 due to halogen chemistry A combination of factors including snow emissions, vertical mixing, and atmospheric chemistry explain surface Arctic halogen observations Snow emissions of halogens impact atmospheric chemistry within a shallow layer near the surface Surface HOxconcentrations are increased by up to a factor of 30 due to halogen chemistry

High-sensitivity detection of formaldehyde (CH_2O) at 3.5315 µm (2831.64 cm^-1) is reported with a diode-laser-pumped, fiber-coupled, periodically poled LiNbO_3 spectroscopic source. This source replaced the Pb–salt diode laser Dewar assembly of an existing tunable diode-laser absorption spectrometer designed for ultrasensitive detection of CH_2O. Spectra are recorded with 2f-modulation spectroscopy and zero-air rapid background subtraction. Initial measurements reported here, determined from multiple measurements of a flowing 7.7 parts per billion by volume (ppbv, parts in 10^9) CH_2O in air mixture, indicate replicate precisions as low as 0.24 ppbv.

In this paper we report the results of a laboratory study for detecting the important atmospheric molecule HCl using a tunable diode laser coupled to a multipass White cell. In contrast to many such prototype studies, the calibration in this work was carried out near the concentration range of interest and verified using three different techniques. Employing a 40-m path length, we have demonstrated a detection limit (SNR = 1) in the 150–230 parts-per-trillion range at pressures around 9 Torr.

There are various potential sources of systematic error in tunable-diode-laser absorption measurements. In this paper, we discuss two such sources that are associated with multimode lasing. The first is caused by secondary modes which are passed by a monochromator and are absorbed by lines not intentionally being studied. In the second source of error, different spatial modes may appear in different arms of a double-beam system. Both types of errors can give rise to rather dramatic systematic errors in frequency and concentration calibrations.

Optoacoustic measurements of NO2excited by an Ar+laser were performed in the presence of NO, N2, H2O, and O2matrix gases. Identical sensitivities were measured in all matrix gases except O2where energy transfer from NO2to the metastable O2(1Δg) state resulted in a dramatic decrease in sensitivity.

An electronic timing circuit using a microphone triggering device has been developed for elimination of mechanically induced frequency-jitter in diode laser spectrometers employing closed-cycle refrigerators. Mechanical compressor piston shocks are detected by the microphone and actuate an electronic circuit which ultimately interrupts data acquisition until the mechanical vibrations are completely quenched. In this way, laser sweeps contaminated by compressor frequency-jitter are not co-averaged. Employing this circuit, measured linewidths were in better agreement with that calculated. The importance of eliminating this mechanically induced frequency-jitter when carrying out quantitative diode laser measurements is further discussed.

A versatile and integrated tunable diode laser system for high precision measurements of the important sulfur gas carbonyl sulfide is described. We explicitly address some of the major factors affecting tunable diode laser measurement precision as well as accuracy and have implemented a number of new features for increased system control and versatility. The system described herein provides the capability for measuring ambient concentrations of this gas with a precision in the range from ±0.3 to ±1% over time periods of many hours. Such a precision provides us with an important new capability for measuring true spatial and temporal variations of carbonyl sulfide in the atmosphere.

Global Learning and Observations to Benefit the Environment (GLOBE) is an international environmental education and science partnership which coordinates the work of students (aged 5 to 18), teachers and scientists from 48 countries on five continents to study and better understand the global environment. Accurate ground reference data is fundamental to the use of remotely sensed data for land cover classification and mapping. Because very little ground reference data has been collected, the accuracy of many land cover maps may be questioned, thus accurate land cover ground reference data is an important need that could be addressed through GLOBE scientist-student collaboration. If earth systems scientists are to use student data, it is important that those data be as accurate as possible to ensure reliability of research results. Thus a key question for this research is whether student collected data are accurate enough to support rigorous scientific investigations. This paper describes results of the GLOBE Science-Education Team on Data Validation and Accuracy Assessment's collaboration with teachers and students to: (1) design and test the pre-protocol learning activities; (2) test the protocols intended to guide the collection and analysis of data; and (3) implement the learning activities and protocols to determine the relative accuracy of student collected versus professionally collected land cover data. To ensure the most accurate classification of land cover possible, a new international hierarchical land cover classification system, the Modified Unesco Classification (MUC) system was developed. GLOBE Data Collection Protocols and methods were designed and implemented to test the accuracy of student collected reference data were designed and implemented. Students who collected land cover reference data using GLOBE protocols, obtained data which are at least as accurate as that collected by professionals.

The famous SiSatchanalai ceramics industry of north central Thailand operated from the tenth or eleventh century AD until the sixteenth century. The reasons for the decline of the industry have not yet been fully clarified and have focused on social and economic factors. Evidence is presented from Ban Ko Noi, based on stratigraphy, radiocarbon dating, pollen, and the character of the kilns and associated ceramics. This evidence demonstrates that a possible reason for the decline—riverine erosion of the land on which the industry was sited-clearly postdated the decline, which cannot therefore be attributed to these physical factors.

We present two new approaches in tunable diode laser absorption spectroscopy (TDLAS) for measuring the ratio of two components with high precision. These techniques, dual line fitting analysis and jump scanning, greatly extend the versatility and applicability of TDLAS. Three important applications for these approaches are discussed. In addition, we demonstrate the capability to quantify features that are different in amplitude by a factor of 22.4 with a precision of 0.3%. Such a precision is also achieved for features that are different in amplitude by a factor of 12.9 and separated by 0.2363 cm^−1. Both jump scanning and dual line fitting analysis are being used on a routine basis in a laboratory kinetics study to measure simultaneously the concentrations of H_2O and NO, whose features are separated by 0.4866 cm^−1.

A precision laser spectrometer for the detection of CO_2 isotopes is reported. The spectrometer measures the fundamental absorption signatures of ^13C and ^12C isotopes in CO_2 at 4.32 μm using a tunable mid-IR laser source based on difference-frequency generation. The spectrometer attains a precision of up to 0.02‰ for 150 s of averaging. An overall accuracy of 0.05‰ was obtained when sampling various calibrated reference gases.

Diagnosing carbon dioxide ( CO2) and methane ( CH4) fluxes at subcontinental scales is complicated by sparse observations, limited knowledge of prior fluxes and their uncertainties, and background and transport errors. Multispecies measurements in flasks sampled during the wintertime ACT‐America campaign were used for background characterization and source apportionment of regional anthropogenic CO2and CH4fluxes when ecosystem CO2exchange is likely to be least active. Continental background trace gas mole fractions for regional enhancements are defined using samples from the upper troposphere and assessed using model products. Trace gas enhancements taken from flask samples in the lower troposphere with background levels subtracted out are then interpreted to inform CO2and CH4enhancement variability in the eastern United States. Strong correlations between CO2and CH4enhancements in the Midwestern and Mid‐Atlantic United States indicated colocated anthropogenic sources. Oil and natural gas influence was also broadly observed throughout the entire observational domain. In the Midwestern United States, agricultural influence on CO2and CH4enhancement variability was evident during above‐average wintertime temperatures. Weaker correlations between CO2and anthropogenic tracer enhancements in the Southeastern United States indicated potentially nonnegligible wintertime ecosystem CO2exchange, with biogenic tracers indicating more active surface processing than other regions. These whole‐air flask samples illuminated significant regional CO2and CH4sources or sinks during Atmospheric Carbon and Transport‐America (ACT‐America) and can provide additional information for informing regional inverse modeling efforts. Multispecies flask samples are used to characterize regional wintertime eastern U.S. CO2 and CH4 enhancement variabilityMid‐Atlantic and Midwestern U.S. CO2 and CH4 enhancements are primarily anthropogenicWinter Southeastern U.S. CO2 and CH4 enhancements indicate influence from biogenic exchange and surface processing

A sensitive photoacoustic detection system for trace atmospheric measurements of HCl is described. The results reported here suggest the capability of measuring HCl at the 50-parts-in-10^9 level with a prototype laboratory system. Further system improvements and atmospheric-measurement considerations are discussed.

A technique employing pressure modulation is described which minimizes all interference fringing produced in small base length multipass absorption cells in diode laser studies.

In support of future satellite missions that aim to address the current shortcomings in measuring air quality from space, NASA's Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field campaign was designed to enable exploration of relationships between column measurements of trace species relevant to air quality at high spatial and temporal resolution. In the DISCOVER-AQ data set, a modest correlation (r2?=?0.45) between ozone (O3) and formaldehyde (CH2O) column densities was observed. Further analysis revealed regional variability in the O3-CH2O relationship, with Maryland having a strong relationship when data were viewed temporally and Houston having a strong relationship when data were viewed spatially. These differences in regional behavior are attributed to differences in volatile organic compound (VOC) emissions. In Maryland, biogenic VOCs were responsible for ~28% of CH2O formation within the boundary layer column, causing CH2O to, in general, increase monotonically throughout the day. In Houston, persistent anthropogenic emissions dominated the local hydrocarbon environment, and no discernable diurnal trend in CH2O was observed. Box model simulations suggested that ambient CH2O mixing ratios have a weak diurnal trend (±20% throughout the day) due to photochemical effects, and that larger diurnal trends are associated with changes in hydrocarbon precursors. Finally, mathematical relationships were developed from first principles and were able to replicate the different behaviors seen in Maryland and Houston. While studies would be necessary to validate these results and determine the regional applicability of the O3-CH2O relationship, the results presented here provide compelling insight into the ability of future satellite missions to aid in monitoring near-surface air quality. A correlation between column CH2O and near-surface O3measurements was observed and could be useful for monitoring air quality from spaceThe strength of the correlation between column CH2O and near-surface O3is highest when there is temporal variability in CH2OThe O3-CH2O relationship appears to be strongest in regions where emissions of biogenic VOCs dominate the local hydrocarbon mix

This Applied Optics feature issue on Laser Applications to Chemical, Security, and Environmental Analysis (LACSEA) highlights papers presented at the LACSEA 2006 Tenth Topical Meeting sponsored by the Optical Society of America.