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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.

The dominant fraction of anthropogenic volatile organic compound (VOC) emissions shifted from transportation fuels to volatile chemical products (VCP) in Los Angeles (LA) in 2010. This shift in VOC composition raises the question about the importance of VCP emissions for ozone (O3) formation. In this study, O3chemistry during the CalNex 2010 was modeled using the Master Chemical Mechanism (MCM) version 3.3.1 and a detailed representation of VCP emissions based on measurements combined with inventory estimates. The model calculations indicate that VCP emissions contributed to 23% of the mean daily maximum 8‐hr average O3(DMA8 O3) during the O3episodes. The simulated OH reactivity, including the contribution from VCP emissions, aligns with observations. Additionally, this framework was employed using four lumped mechanisms with simplified representations of emissions and chemistry. RACM2‐VCP showed the closest agreement with MCM, with a slight 4% increase in average DMA8 O3(65 ± 13 ppb), whereas RACM2 (58 ± 13 ppb) and SAPRC07B (59 ± 14 ppb) exhibited slightly lower levels. CB6r2, however, recorded reduced concentrations (37 ± 10 ppb). Although emissions of O3precursors have declined in LA since 2010, O3levels have not decreased significantly. Model results ascribed this trend to the rapid reduction in NOXemissions. Moreover, given the impact of COVID‐19, an analysis of 2020 reveals a shift to a NOX‐limited O3formation regime in LA, thereby diminishing the influence of VCPs. This study provides new insights into the impact of VCP emissions on O3pollution from an in‐depth photochemical perspective. In the 2010 CalNex study, researchers found that volatile organic compounds (VOCs) were predominantly emitted from volatile chemical products (VCPs) like solvents. In our subsequent research, using a detailed chemical model, we discovered that about a quarter of the mean daily maximum 8‐hr average ozone was contributed by these everyday products during ozone episodes. This insight is critical as it underscores how these emissions significantly speed up ozone formation through accelerated chemical reactions. We also evaluated various simplified chemical mechanisms for ozone prediction, finding that the one incorporating key reactions of VOC species was most accurate. Further, our analysis suggests that the slight increase in Los Angeles' ozone levels since 2010 can likely be attributed to faster reductions in NOXemissions relative to VOCs. Notably, the reduction in NOXemissions by 2020 considerably diminished the impact of VCPs on ozone levels. However, given the uncertain future of NOXemissions and the ongoing rise in emissions from everyday products, it remains essential to control these emissions. Volatile chemical product emissions accounted for 23% of mean daily max 8‐hr ozone in ozone episodes, as per the 2010 CalNex studyVCP emissions boost ozone formation by increasing primary production and efficient recycling of ROx radicals, thus enhancing pollution2020s reduction in NOx emissions in Los Angeles, potentially due to COVID‐19, led to a NOx‐limited state, lessening VCPs' impact on ozone Volatile chemical product emissions accounted for 23% of mean daily max 8‐hr ozone in ozone episodes, as per the 2010 CalNex study VCP emissions boost ozone formation by increasing primary production and efficient recycling of ROx radicals, thus enhancing pollution 2020s reduction in NOx emissions in Los Angeles, potentially due to COVID‐19, led to a NOx‐limited state, lessening VCPs' impact on ozone

Despite the central role of reactive organic carbon (ROC) in the formation of secondary species that impact global air quality and climate, our assessment of ROC abundance and impacts is challenged by the diversity of species that contribute to it. We revisit measurements of ROC species made during two field campaigns in the United States: the 2013 SOAS campaign in forested Centreville, AL, and the 2010 CalNex campaign in urban Pasadena, CA. We find that average measured ROC concentrations are about twice as high in Pasadena (73.8 μgCsm–3) than in Centreville (36.5 μgCsm–3). However, the OH reactivity (OHR) measured at these sites is similar (20.1 and 19.3 s–1). The shortfall in OHR when summing up measured contributions is 31%, at Pasadena and 14% at Centreville, suggesting that there may be a larger reservoir of unmeasured ROC at the former site. Estimated O3production and SOA potential (defined as concentration × yield) are both higher during CalNex than SOAS. This analysis suggests that the ROC in urban California is less reactive, but due to higher concentrations of oxides of nitrogen and hydroxyl radicals, is more efficient in terms of O3and SOA production, than in the forested southeastern U.S.

Heterogeneous chemical cycles of pyrogenic nitrogen and halides influence tropospheric ozone and affect the stratosphere during extreme Pyrocumulonimbus (PyroCB) events. We report field‐derived N2O5uptake coefficients, γ(N2O5), and ClNO2yields, φ(ClNO2), from two aircraft campaigns observing fresh smoke in the lower and mid troposphere and processed/aged smoke in the upper troposphere and lower stratosphere (UTLS). Derived φ(ClNO2) varied across the full 0–1 range but was typically <0.5 and smallest in a PyroCB (<0.05). Derived γ(N2O5) was low in agricultural smoke (0.2–3.6 × 10−3), extremely low in mid‐tropospheric wildfire smoke (0.1 × 10−3), but larger in PyroCB processed smoke (0.7–5.0 × 10−3). Aged biomass burning aerosol in the UTLS had a higher γ(N2O5) of 17 × 10−3that increased with sulfate and liquid water, but that was 1–2 orders of magnitude lower than values for aqueous sulfuric aerosol used in stratospheric models. The injection of reactive material into Earth's atmosphere from fires affects atmospheric composition at regional and hemispheric scales. Reported stratospheric ozone depletion during extreme events, such as the 2020 Australian wildfires, illustrates one example of fire impacts and the role of heterogeneous (gas‐particle) processes. We report field quantification of rates and product yields from airborne observations of smoke. Extremely slow heterogeneous reaction rates on young smoke increase with transport and aging, but upper atmospheric values are still a factor of 10 slower than parameterizations used in stratospheric models. Heterogeneous production of ClNO2, a major lower atmospheric chlorine activation pathway, may be active on biomass burning aerosol in the upper atmosphere. ClNO2formation is active on biomass burning (BB) particles but decreases with transport to the upper troposphere and lower stratosphere (UTLS)N2O5uptake coefficients are low on young BB smoke and increase with transport through a PyroCB and UTLS agingN2O5uptake coefficients on aged BB particles in the UTLS are significantly lower than those used in model parameterizations ClNO2formation is active on biomass burning (BB) particles but decreases with transport to the upper troposphere and lower stratosphere (UTLS) N2O5uptake coefficients are low on young BB smoke and increase with transport through a PyroCB and UTLS aging N2O5uptake coefficients on aged BB particles in the UTLS are significantly lower than those used in model parameterizations

We use a 0‐D photochemical box model and a 3‐D global chemistry‐climate model, combined with observations from the NOAA Southeast Nexus (SENEX) aircraft campaign, to understand the sources and sinks of glyoxal over the Southeast United States. Box model simulations suggest a large difference in glyoxal production among three isoprene oxidation mechanisms (AM3ST, AM3B, and Master Chemical Mechanism (MCM) v3.3.1). These mechanisms are then implemented into a 3‐D global chemistry‐climate model. Comparison with field observations shows that the average vertical profile of glyoxal is best reproduced by AM3ST with an effective reactive uptake coefficient γglyxof 2 × 10−3and AM3B without heterogeneous loss of glyoxal. The two mechanisms lead to 0–0.8 µg m−3secondary organic aerosol (SOA) from glyoxal in the boundary layer of the Southeast U.S. in summer. We consider this to be the lower limit for the contribution of glyoxal to SOA, as other sources of glyoxal other than isoprene are not included in our model. In addition, we find that AM3B shows better agreement on both formaldehyde and the correlation between glyoxal and formaldehyde (RGF= [GLYX]/[HCHO]), resulting from the suppression of δ‐isoprene peroxy radicals. We also find that MCM v3.3.1 may underestimate glyoxal production from isoprene oxidation, in part due to an underestimated yield from the reaction of isoprene epoxydiol (IEPOX) peroxy radicals with HO2. Our work highlights that the gas‐phase production of glyoxal represents a large uncertainty in quantifying its contribution to SOA. Box model‐simulated glyoxal production from three isoprene oxidation mechanisms differ greatlyAerosol uptake of glyoxal was constrained using airborne in situ measurements and a global modelModel results show that glyoxal contributes 0–14% of SOA in the Southeast U.S. during summer

The NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) experiment was a multi‐agency, inter‐disciplinary research effort to: (a) obtain detailed measurements of trace gas and aerosol emissions from wildfires and prescribed fires using aircraft, satellites and ground‐based instruments, (b) make extensive suborbital remote sensing measurements of fire dynamics, (c) assess local, regional, and global modeling of fires, and (d) strengthen connections to observables on the ground such as fuels and fuel consumption and satellite products such as burned area and fire radiative power. From Boise, ID western wildfires were studied with the NASA DC‐8 and two NOAA Twin Otter aircraft. The high‐altitude NASA ER‐2 was deployed from Palmdale, CA to observe some of these fires in conjunction with satellite overpasses and the other aircraft. Further research was conducted on three mobile laboratories and ground sites, and 17 different modeling forecast and analyses products for fire, fuels and air quality and climate implications. From Salina, KS the DC‐8 investigated 87 smaller fires in the Southeast with remote and in‐situ data collection. Sampling by all platforms was designed to measure emissions of trace gases and aerosols with multiple transects to capture the chemical transformation of these emissions and perform remote sensing observations of fire and smoke plumes under day and night conditions. The emissions were linked to fuels consumed and fire radiative power using orbital and suborbital remote sensing observations collected during overflights of the fires and smoke plumes and ground sampling of fuels. The NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) experiment was aimed at understanding how fuel and fire conditions at the point of emission influence the chemistry of smoke, what conditions and processes control the rise of smoke plumes, what happens to smoke as it is distributed in the atmosphere, and how chemical transformation of smoke impacts air quality, weather, and climate downwind. Lessons learned from FIREX‐AQ will also be used to assess and improve the effectiveness of satellites for estimating the emissions from wildfires and prescribed burns and to reduce uncertainties associated with modeling and forecasting of smoke. Here we present an overview of the FIREX‐AQ effort, its motivation and design, with detailed descriptions of the measurements and analyses carried out, their connections to FIREX‐AQ science goals, and the early findings of this exceptionally broad effort to understand fire and its many impacts on the atmosphere. This work is an overview of the NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) field experimentFIREX‐AQ investigated biomass burning emissions and chemistry and smoke transportFIREX‐AQ was a multi‐platform mission that also utilized fire modeling and satellite detections and validation This work is an overview of the NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) field experiment FIREX‐AQ investigated biomass burning emissions and chemistry and smoke transport FIREX‐AQ was a multi‐platform mission that also utilized fire modeling and satellite detections and validation

A new method for the cross-metathesis of terminal olefins is described. Treatment of terminal olefins with 1–2 equivalents of a symmetric disubstituted cisor transolefin and 5 mol% Cl 2(PCy 3) 2RuCHPh ( 1) in dichloromethane generates the desired cross-metathesis products in good yield.

New olefin metathesis methodology for the homologation of terminal olefins to protected α,β-unsaturated aldehydes is described. Acrolein acetals, including asymmetric derivatives, are robust cross-metathesis substrates as evidenced by reaction yields of 80–90% at catalyst loadings of 2–5 mol % (PCy 3) 2Cl 2RuCHPh ( 1).

Nitrous acid (HONO) is an important radical precursor that can impact secondary pollutant levels, especially in urban environments. Due to uncertainties in its heterogeneous formation mechanisms, models often under predict HONO concentrations. A number of heterogeneous sources at the ground have been proposed but there is no consensus about which play a significant role in the urban boundary layer. We present a new one‐dimensional chemistry and transport model which performs surface chemistry based on molecular collisions and chemical conversion, allowing us to add detailed HONO formation chemistry at the ground. We conducted model runs for the 2010 CalNex campaign, finding good agreement with observations for key species such as O3, NOx, and HOx. With the ground sources implemented, the model captures the diurnal and vertical profile of the HONO observations. Primary HOxproduction from HONO photolysis is 2–3 times more important than O3or HCHO photolysis at mid‐day, below 10 m. The HONO concentration, and its contribution to HOx, decreases quickly with altitude. Heterogeneous chemistry at the ground provided a HONO source of 2.5 × 1011molecules cm−2s−1during the day and 5 × 1010molecules cm−2s−1at night. The night time source was dominated by NO2hydrolysis. During the day, photolysis of surface HNO3/nitrate contributed 45%–60% and photo‐enhanced conversion of NO2contributed 20%–45%. Sensitivity studies addressing the uncertainties in both photolytic mechanisms show that, while the relative contribution of either source can vary, HNO3/nitrate is required to produce a surface HONO source that is strong enough to explain observations. Measured vertical profiles of HONO near Los Angeles in May 2010 suggest a heterogeneous HONO source at the groundA new 1D chemistry and transport model that includes HONO formation on the ground reproduces the HONO concentration profilesThe main daytime HONO source is adsorbed nitric acid/nitrate photolysis, followed by photo‐enhanced NO2conversion Measured vertical profiles of HONO near Los Angeles in May 2010 suggest a heterogeneous HONO source at the ground A new 1D chemistry and transport model that includes HONO formation on the ground reproduces the HONO concentration profiles The main daytime HONO source is adsorbed nitric acid/nitrate photolysis, followed by photo‐enhanced NO2conversion

We present a novel method, the Gaussian observational model for edge to center heterogeneity (GOMECH), to quantify the horizontal chemical structure of plumes. GOMECH fits observations of short-lived emissions or products against a long-lived tracer (e.g., CO) to provide relative metrics for the plume width (wi/wCO) and center (bi/wCO). To validate GOMECH, we investigate OH and NO3oxidation processes in smoke plumes sampled during FIREX-AQ (Fire Influence on Regional to Global Environments and Air Quality, a 2019 wildfire smoke study). An analysis of 430 crosswind transects demonstrates that nitrous acid (HONO), a primary source of OH, is narrower than CO (wHONO/wCO= 0.73–0.84 ± 0.01) and maleic anhydride (an OH oxidation product) is enhanced on plume edges (wmaleicanhydride/wCO= 1.06–1.12 ± 0.01). By contrast, NO3production [P(NO3)] occurs mainly at the plume center (wP(NO3)/wCO= 0.91–1.00 ± 0.01). Phenolic emissions, highly reactive to OH and NO3, are narrower than CO (wphenol/wCO= 0.96 ± 0.03, wcatechol/wCO= 0.91 ± 0.01, and wmethylcatechol/wCO= 0.84 ± 0.01), suggesting that plume edge phenolic losses are the greatest. Yet, nitrophenolic aerosol, their oxidation product, is the greatest at the plume center (wnitrophenolicaerosol/wCO= 0.95 ± 0.02). In a large plume case study, GOMECH suggests that nitrocatechol aerosol is most associated with P(NO3). Last, we corroborate GOMECH with a large eddy simulation model which suggests most (55%) of nitrocatechol is produced through NO3in our case study.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.