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Peroxy acyl nitrates (PANs) are photochemical pollutants with implications for health and atmospheric oxidation capacity. PANs are formed via the oxidation of non-methane volatile organic compounds (NMVOCs) in the presence of nitrogen oxide radicals (NOx = NO + NO2). While urban environments are large sources of PANs, in situ observations in urban areas are limited. Here we use satellite measurements of PANs from the Tropospheric Emission Spectrometer (TES) and the Suomi National Polar-orbiting Partnership (S-NPP) Cross-track Infrared Sounder (CrIS) to evaluate the spatiotemporal variability of PANs over and around Mexico City. Monthly mean maxima in PANs over the Mexico City Metropolitan Area (MCMA) occur during spring months (March–May). This time of year coincides with a peak in local photochemistry and more frequent air stagnation. Local fire activity also typically peaks between February and May, which leads to strong interannual variability of PANs over the MCMA. We use S-NPP CrIS data to probe the spatial outflow pattern of PANs produced within urban Mexico City during the month with the largest mixing ratios of PANs (April). Peak outflow in April occurs to the northeast of the city and over the mountains south of the city. Outflow to the northwest appears infrequently. Using observations during 2018 versus 2019, we also show that PANs were not significantly reduced during a year, with a significant decrease in NOx over Mexico City. Our analysis demonstrates that the space-based observations provided by CrIS and TES can increase understanding of the spatiotemporal variability of PANs over and surrounding Mexico City.

Carlsbad Caverns National Park in southeastern New Mexico is adjacent to the Permian Basin, one of the most productive oil and gas regions in the country. The 2019 Carlsbad Caverns Air Quality Study (CarCavAQS) was designed to examine the influence of regional sources, including urban emissions, oil and gas development, wildfires, and soil dust on air quality in the park. Field measurements of aerosols, trace gases, and deposition were conducted from 25 July through 5 September 2019. Here, we focus on observations of fine particles and key trace gas precursors to understand the important contributing species and their sources and associated impacts on haze. Key gases measured included aerosol precursors, nitric acid and ammonia, and oil and gas tracer, methane. High-time resolution (6-min) PM2.5 mass ranged up to 31.8 µg m−3, with an average of 7.67 µg m−3. The main inorganic ion contributors were sulfate (avg 1.3 µg m−3), ammonium (0.30 µg m−3), calcium (Ca2+) (0.22 µg m−3), nitrate (0.16 µg m−3), and sodium (0.057 µg m−3). The WSOC concentration averaged 1.2 µg C m−3. Sharp spikes were observed in Ca2+, consistent with local dust generation and transport. Ion balance analysis and abundant nitric acid suggest PM2.5 nitrate often reflected reaction between nitric acid and sea salt, forming sodium nitrate, and between nitric acid and soil dust containing calcium carbonate, forming calcium nitrate. Sulfate and soil dust are the major contributors to modeled light extinction in the 24-hr average daily IMPROVE observations. Higher time resolution data revealed a maximum 1-hr extinction value of 90 Mm−1 (excluding coarse aerosol) and included periods of significant light extinction from BC as well as sulfate and soil dust. Residence time analysis indicated enrichment of sulfate, BC, and methane during periods of transport from the southeast, the direction of greatest abundance of oil and gas development. Implications: Rapid development of U.S. oil and gas resources raises concerns about potential impacts on air quality in National Parks. Measurements in Carlsbad Caverns National Park provide new insight into impacts of unconventional oil and gas development and other sources on visual air quality in the park. Major contributors to visibility impairment include sulfate, soil dust (often reacted with nitric acid), and black carbon. The worst periods of visibility and highest concentrations of many aerosol components were observed during transport from the southeast, a region of dense Permian Basin oil and gas development.

Light absorbing organic carbon, or brown carbon (BrC), can be a significant contributor to the visible light absorption budget. However, the sources of BrC and the contributions of BrC to light absorption are not well understood. Biomass burning is thought to be a major source of BrC. Therefore, as part of the WE-CAN (Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption and Nitrogen) study, BrC absorption data were collected on board the National Science Foundation/National Center for Atmospheric Research (NSF/NCAR) C-130 aircraft as it intercepted smoke from wildfires in the western US in July–August 2018. BrC absorption measurements were obtained in near real-time using two techniques. The first coupled a particle-into-liquid sampler (PILS) with a liquid waveguide capillary cell and a total organic carbon analyzer for measurements of water-soluble BrC absorption and WSOC (water-soluble organic carbon). The second employed a custom-built photoacoustic aerosol absorption spectrometer (PAS) to measure total absorption at 405 and 660 nm. The PAS BrC absorption at 405 nm (PAS total Abs 405 BrC) was calculated by assuming the absorption determined by the PAS at 660 nm was equivalent to the black carbon (BC) absorption and the BC aerosol absorption Ångström exponent was 1. Data from the PILS and PAS were combined to investigate the water-soluble vs. total BrC absorption at 405 nm in the various wildfire plumes sampled during WE-CAN. WSOC, PILS water-soluble Abs 405, and PAS total Abs 405 tracked each other in and out of the smoke plumes. BrC absorption was correlated with WSOC (R2 value for PAS =0.42 and PILS =0.60) and CO (carbon monoxide) (R2 value for PAS =0.76 and PILS =0.55) for all wildfires sampled. The PILS water-soluble Abs 405 was corrected for the non-water-soluble fraction of the aerosol using the calculated UHSAS (ultra-high-sensitivity aerosol spectrometer) aerosol mass. The corrected PILS water-soluble Abs 405 showed good closure with the PAS total Abs 405 BrC with a factor of ∼1.5 to 2 difference. This difference was explained by particle vs. bulk solution absorption measured by the PAS vs. PILS, respectively, and confirmed by Mie theory calculations. During WE-CAN, ∼ 45 % (ranging from 31 % to 65 %) of the BrC absorption was observed to be due to water-soluble species. The ratio of BrC absorption to WSOC or ΔCO showed no clear dependence on fire dynamics or the time since emission over 9 h.

Agricultural emissions, including those from concentrated animal feeding operations (CAFOs) for beef and dairy cattle, make up a large portion of the United States' total greenhouse gas (GHG) emissions. However, many CAFOs reside in areas where methane (CH4) from oil and natural gas (ONG) complicates the quantification of CAFO emissions. Traditional approaches to quantify emissions in such regions often relied on inventory subtraction of other known sources. We compare the results of two approaches to attribute the CAFO CH4 emission rate from the total CH4 emission rate derived from an aircraft mass balance technique. These methods make use of the mixing ratio data of CH4, ethane (C2H6), and ammonia (NH3) that were collected simultaneously in-flight downwind of CAFOs in northeastern Colorado. The first approach, the subtraction method (SM), is similar to inventory subtraction, except the amount to be removed is derived from the observed C2H6 to CH4 ratio rather than an inventory estimate. The results from this approach showed high uncertainty, primarily due to how error propagates through subtraction. Alternatively, multivariate regression (MVR) can be used to estimate CAFO CH4 emissions using the NH3 emission rate and an NH3 to CH4 ratio. These results showed significantly less uncertainty. We identified criteria to determine the best attribution method; these criteria can support attribution in other regions. The final emission estimates for the CAFOs presented here were 13 ± 3 g of CH4 per head per hour and 13 ± 2 g of NH3 per head per hour. These estimates are higher than the inventory of the US Environmental Protection Agency (EPA) and previous studies highlighting the need for more measurements of CH4 and NH3 emission rates.

The impact of biomass burning (BB) on the atmospheric burden of volatile organic compounds (VOCs) is highly uncertain. Here we apply the GEOS-Chem chemical transport model (CTM) to constrain BB emissions in the western USA at ∼ 25 km resolution. Across three BB emission inventories widely used in CTMs, the inventory–inventory comparison suggests that the totals of 14 modeled BB VOC emissions in the western USA agree with each other within 30 %–40 %. However, emissions for individual VOCs can differ by a factor of 1–5, driven by the regionally averaged emission ratios (ERs, reflecting both assigned ERs for specific biome and vegetation classifications) across the three inventories. We further evaluate GEOS-Chem simulations with aircraft observations made during WE-CAN (Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption and Nitrogen) and FIREX-AQ (Fire Influence on Regional to Global Environments and Air Quality) field campaigns. Despite being driven by different global BB inventories or applying various injection height assumptions, the model–observation comparison suggests that GEOS-Chem simulations underpredict observed vertical profiles by a factor of 3–7. The model shows small to no bias for most species in low-/no-smoke conditions. We thus attribute the negative model biases mostly to underestimated BB emissions in these inventories. Tripling BB emissions in the model reproduces observed vertical profiles for primary compounds, i.e., CO, propane, benzene, and toluene. However, it shows no to less significant improvements for oxygenated VOCs, particularly for formaldehyde, formic acid, acetic acid, and lumped ≥ C3 aldehydes, suggesting the model is missing secondary sources of these compounds in BB-impacted environments. The underestimation of primary BB emissions in inventories is likely attributable to underpredicted amounts of effective dry matter burned, rather than errors in fire detection, injection height, or ERs, as constrained by aircraft and ground measurements. We cannot rule out potential sub-grid uncertainties (i.e., not being able to fully resolve fire plumes) in the nested GEOS-Chem which could explain the negative model bias partially, though back-of-the-envelope calculation and evaluation using longer-term ground measurements help support the argument of the dry matter burned underestimation. The total ERs of the 14 BB VOCs implemented in GEOS-Chem only account for half of the total 161 measured VOCs (∼ 75 versus 150 ppb ppm−1). This reveals a significant amount of missing reactive organic carbon in widely used BB emission inventories. Considering both uncertainties in effective dry matter burned (× 3) and unmodeled VOCs (× 2), we infer that BB contributed to 10 % in 2019 and 45 % in 2018 (240 and 2040 Gg C) of the total VOC primary emission flux in the western USA during these two fire seasons, compared to only 1 %–10 % in the standard GEOS-Chem.

An abundance of literature has examined barriers to women’s equitable representation in science, technology, engineering, and math (STEM) fields, with many studies demonstrating that STEM fields are not perceived to afford communal goals, a key component of women’s interest in future careers. Using Goal Congruity Theory as a framework, we tested the longitudinal impact of perceptions of STEM career goal affordances, personal communal and agentic goal endorsements, and their congruity on persistence in science from the second through fourth years of college among women in STEM majors in the United States. We found that women’s intent to persist in science were highest in the fall of their second year, that persistence intentions exhibited a sharp decline, and eventually leveled off by their fourth year of college. This pattern was moderated by perceptions of agentic affordances in STEM, such that women who believe that STEM careers afford the opportunity for achievement and individualism experienced smaller declines. We found that higher perceptions of communal goal affordances in STEM consistently predicted higher persistence intentions indicating women may benefit from perceptions that STEM affords communal goals. Finally, we found women with higher agentic affordances in STEM also had greater intentions to persist, and this relationship was stronger for women with higher agentic goals. We conclude that because STEM fields are stereotyped as affording agentic goals, women who identify interest in a STEM major during their first years of college may be drawn to these fields for this reason and may benefit from perceptions that STEM affords agentic goals.

Quantifying ammonia (NH

Wildfires are a source of primary aerosols and precursors for secondary aerosols to the atmosphere. In this work, we discover that the evolution of these aerosols depends strongly on the coupled effects of dilution, photooxidation, and partitioning.

Mentorship can be part of the solution to developing a more diverse global scientific workforce, but robust longitudinal evidence is limited. Developmental mentor network theory can advance our understanding of the impact of a wide range of mentors across social contexts by distinguishing between the content of mentorship support (eg career support) and the structural characteristics of an individual’s mentor network (eg density of connections among mentors). We tested the influence of mentor network characteristics on longitudinal social integration into earth and environmental sciences, as indicated by science identity development (a key indicator of social integration) and STEM graduate school applications, in a sample of 233 undergraduate women at 9 universities in the U.S. Findings indicate that belonging to close-knit, larger, and skill-focused mentorship networks creates a “sticky web” of social connections, providing information and resources that increase retention of college women in the earth and environmental sciences.

Sexual harassment in field settings brings unique challenges for prevention and response, as field research occurs outside “typical” workplaces, often in remote locations that create additional safety concerns and new team dynamics. We report on a project that has 1) trained field project participants to recognize, report, and confront sexual harassment, and 2) investigated the perceptions, attitudes, and experiences of field researchers regarding sexual harassment. Precampaign surveys from four major, multi-institutional, domestic, and international field projects indicate that the majority of sexual harassment reported prior to the field campaigns was hostile work environment harassment, and women were more likely to be the recipients, on average reporting two to three incidents each. The majority of those disclosing harassment indicated that they coped with past experiences by avoiding their harasser or downplaying incidents. Of the incidences reported (47) in postcampaign surveys of the four field teams, all fell under the category of hostile work environment and included incidents of verbal, visual, and physical harassment. Women’s harassment experiences were perpetrated by men 100% of the time, and the majority of the perpetrators were in more senior positions than the victims. Men’s harassment experiences were perpetrated by a mix of women and men, and the majority came from those at the same position of seniority. Postproject surveys indicate that the training programs (taking place before the field projects) helped participants come away with more positive than negative emotions and perceptions of the training, the leadership, and their overall experiences on the field campaign.

The evolution of organic aerosol (OA) and brown carbon (BrC) in wildfire plumes, including the relative contributions of primary versus secondary sources, has been uncertain in part because of limited knowledge of the precursor emissions and the chemical environment of smoke plumes. We made airborne measurements of a suite of reactive trace gases, particle composition, and optical properties in fresh western US wildfire smoke in July through August 2018. We use these observations to quantify primary versus secondary sources of biomass-burning OA (BBPOA versus BBSOA) and BrC in wildfire plumes. When a daytime wildfire plume dilutes by a factor of 5 to 10, we estimate that up to one-third of the primary OA has evaporated and subsequently reacted to form BBSOA with near unit yield. The reactions of measured BBSOA precursors contribute only 13 ± 3% of the total BBSOA source, with evaporated BBPOA comprising the rest. We find that oxidation of phenolic compounds contributes the majority of BBSOA from emitted vapors. The corresponding particulate nitrophenolic compounds are estimated to explain 29 ± 15% of average BrC light absorption at 405 nm (BrC Abs(405)) measured in the first few hours of plume evolution, despite accounting for just 4 ± 2% of average OA mass. These measurements provide quantitative constraints on the role of dilution-driven evaporation of OA and subsequent radical-driven oxidation on the fate of biomass-burning OA and BrC in daytime wildfire plumes and point to the need to understand how processing of nighttime emissions differs.

Diversity in the geosciences is low despite efforts to improve the representation of different groups in society, for example in terms of gender. Specifically, women are underrepresented in recruitment and retention at every stage of the academic to professional pipeline. Mentoring programs can improve women’s motivation and persistence in science, technology, engineering and mathematics (STEM) career pathways. However, mentorship programs consist of multiple components that vary in complexity and cost, which can limit scalability. Here we present results from a randomized experiment with 158 undergraduate women majoring in a geoscience field to identify the critical elements of a successful mentorship program. The combination of three factors was necessary to increase mentoring, motivation, and persistence: inspiration through exposure to geoscience careers via female role models, inoculation through training on how to grow their mentor network and overcome obstacles, and an introduction to a local female geoscientist mentor. To retain women in geoscience careers, exposure to role models, training on network growth and introduction to mentors in combination improve outcomes for undergraduates, according to a randomized intervention experiment.

Wildfires are an important source of nitrous acid (HONO), a photolabile radical precursor, yet in situ measurements and quantification of primary HONO emissions from open wildfires have been scarce. We present airborne observations of HONO within wildfire plumes sampled during the Western Wildfire Experiment for Cloud chemistry, Aerosol absorption and Nitrogen (WE-CAN) campaign. ΔHONO/ΔCO close to the fire locations ranged from 0.7 to 17 pptv ppbv

Introduction: Wildfire smoke (WFS) increases the risk of respiratory hospitalizations. We evaluated the association between WFS and asthma health care utilization (AHCU) during the 2013 wildfire season in Oregon. Methods: WFS particulate matter ≤2.5 microns in diameter (PM2.5) was estimated using a blended model of in-situ monitoring, chemical transport models, and satellite-based data. Asthma claims and place of service were identified from Oregon All Payer All Claims data from 2013-05-01 to 2013-09-30. The association with WFS PM2.5 was evaluated using time-stratified case-crossover designs. Results: The maximum WFS PM2.5 concentration during the study period was 172 μg/m3. A 10 μg/m3 increase in WFS increased risk in asthma diagnosis at emergency departments (odds ratio [OR]: 1.089, 95% Confidence Interval [CI]: 1.043–1.136), office visit (OR: 1.050, 95%CI: 1.038–1.063), and outpatient visits (OR: 1.065, 95%CI: 1.029–1.103); an association was observed with asthma rescue inhaler medication fills (OR: 1.077, 95%CI: 1.065–1.088). Discussion: WFS increased the risk for asthma morbidity during the 2013 wildfire season in Oregon. Communities impacted by WFS could see increases in AHCU for tertiary, secondary, and primary care.

We present an overview of an optimal estimation algorithm to retrieve peroxyacetyl nitrate (PAN) from single-field-of-view Level 1B radiances measured by the Cross-Track Infrared Sounder (CrIS). CrIS PAN retrievals show peak sensitivity in the mid-troposphere, with degrees of freedom for signal less than or equal to 1.0. We show comparisons with two sets of aircraft measurements from the Atmospheric Tomography Mission (ATom), the PAN and Trace Hydrohalocarbon ExpeRiment (PANTHER) and the Georgia Tech chemical ionization mass spectrometer (GT-CIMS). We find a systematic difference between the two aircraft datasets, with vertically averaged mid-tropospheric values from the GT-CIMS around 14 % lower than equivalent values from PANTHER. However, the two sets of aircraft measurements are strongly correlated (R2 value of 0.92) and do provide a consistent view of the large-scale variation of PAN. We demonstrate that the retrievals of PAN from CrIS show skill in measurement of these large-scale PAN distributions in the remote mid-troposphere compared to the retrieval prior. The standard deviation of individual CrIS–aircraft differences is 0.08 ppbv, which we take as an estimate of the uncertainty of the CrIS mid-tropospheric PAN for a single satellite field of view. The standard deviation of the CrIS–aircraft comparisons for averaged CrIS retrievals (median of 20 satellite coincidences with each aircraft profile) is lower at 0.05 ppbv. This would suggest that the retrieval error is reduced with averaging, although not with the square root of the number of observations. We find a negative bias of the order of 0.1 ppbv in the CrIS PAN results with respect to the aircraft measurements. This bias shows a dependence on column water vapor. We provide a water-vapor-dependent bias correction for use with the CrIS PAN data.

Wildland firefighters are exposed to smoke containing particulate matter (PM) and volatile organic compounds (VOCs) while suppressing wildfires. From 2015–2017, the US Forest Service conducted a field study collecting breathing zone measurements of PM(4) (particulate matter with aerodynamic diameter ≤4 μm) on wildland firefighters from different crew types and while performing various fire suppression tasks on wildfires. Emission ratios of VOC (parts per billion; ppb): PM(1) (particulate matter with aerodynamic diameter ≤1 μm; mg/m(3)) were calculated using data from a separate field study conducted in summer 2018, the Western Wildfire Experiment for Cloud Chemistry, Aerosol Absorption, and Nitrogen (WE-CAN) Campaign. These emission ratios were used to estimate wildland firefighter exposure to acrolein, benzene and formaldehyde. Results of this field sampling campaign reported exposure to PM(4) and VOC varied across wildland firefighter crew type and job task. Type 1 crews had greater exposures to both PM(4) and VOCs than Type 2 or Type 2 Initial Attack crews, and wildland firefighters performing direct suppression had statistically higher exposures than those performing staging and other tasks (mean differences=0.82 and 0.75 mg/m(3); 95% confidence intervals=0.38–1.26 mg/m(3) and 0.41–1.08 mg/m(3), respectively). Of the 81 personal exposure samples collected, 19% of measured PM(4) exposures exceeded the recommended National Wildland Fire Coordinating Group occupational exposure limit (0.7 mg/m(3)). Wildland fire management should continue to find strategies to reduce smoke exposures for wildland firefighters.

Wildfire emissions affect downwind air quality and human health. Predictions of these impacts using models are limited by uncertainties in emissions and chemical evolution of smoke plumes. Using hi...