A5029691962- Atmospheric chemistry and aerosols
- Air Quality and Health Impacts
- Air Quality Monitoring and Forecasting
- Vehicle emissions and performance
- Atmospheric and Environmental Gas Dynamics
- Atmospheric Ozone and Climate
- Atmospheric aerosols and clouds
- Fire effects on ecosystems
- Plant responses to elevated CO2
- Catalytic Processes in Materials Science
- Indoor Air Quality and Microbial Exposure
- Odor and Emission Control Technologies
- Advanced Chemical Sensor Technologies
- Analytical Chemistry and Chromatography
- Petroleum Processing and Analysis
- Hydrocarbon exploration and reservoir analysis
- Toxic Organic Pollutants Impact
- Spectroscopy and Laser Applications
- COVID-19 impact on air quality
- Mass Spectrometry Techniques and Applications
- Methane Hydrates and Related Phenomena
- Advanced Text Analysis Techniques
- Plant Water Relations and Carbon Dynamics
- Smart Materials for Construction
- Conservation Techniques and Studies
Yale University
2016-2025
Max Planck Institute for Chemistry
2019-2022
UConn Health
2022
University of California, Berkeley
2009-2015
University of New Haven
2015
Northwestern University
2009
Air pollution evolution Transport-derived emissions of volatile organic compounds (VOCs) have decreased owing to stricter controls on air pollution. This means that the relative importance chemicals in pesticides, coatings, printing inks, adhesives, cleaning agents, and personal care products has increased. McDonald et al. show these chemical now contribute fully one-half emitted VOCs 33 industrialized cities (see Perspective by Lewis). Thus, focus efforts mitigate ozone formation toxic...
Emissions from gasoline and diesel vehicles are predominant anthropogenic sources of reactive gas-phase organic carbon key precursors to secondary aerosol (SOA) in urban areas. Their relative importance for formation is a controversial issue with implications air quality control policy public health. We characterize the chemical composition, mass distribution, potential emissions vehicles, find exhaust seven times more efficient at forming than exhaust. However, both important quality;...
Laboratory studies have established a number of chemical pathways by which nitrogen oxides (NO(x)) affect atmospheric organic aerosol (OA) production. However, these effects not been directly observed in ambient OA. We report measurements particulate nitrates Bakersfield, California, the nighttime formation increases with NO(x) and is suppressed high concentrations molecules that rapidly react nitrate radical (NO(3))--evidence multigenerational chemistry responsible for This class represents...
Abstract. New pathways to form secondary organic aerosol (SOA) have been postulated recently. Glyoxal, the smallest dicarbonyl, is one of proposed precursors. It has both anthropogenic and biogenic sources, readily partitions into aqueous phase cloud droplets deliquesced particles where it undergoes reversible irreversible chemistry. In this work we extend regional scale chemistry transport model WRF-Chem include detailed gas-phase glyoxal formation as well a state-of-the-science module...
Abstract Methane (CH 4 ), carbon dioxide (CO 2 monoxide (CO), and C –C 5 alkanes were measured throughout the Los Angeles (L.A.) basin in May June 2010. We use these data to show that emission ratios of CH /CO L.A. are larger than expected from population‐apportioned bottom‐up state inventories, consistent with previously published work. experimentally determined combination annual State California CO inventories derive a yearly rate basin. further airborne measurements directly rates dairy...
Due to the rapid development of low-cost air-quality sensors, a rigorous scientific evaluation has not been conducted for many available sensors. We evaluated three Plantower PMS A003 sensors when exposed eight particulate matter (PM) sources (i.e., incense, oleic acid, NaCl, talcum powder, cooking emissions, and monodispersed polystyrene latex spheres under controlled laboratory conditions also residential air ambient outdoor in Baltimore, MD). The PM2.5 exhibited high degree precision R2...
Laboratory and field observations of organic compound emissions reveal a previously unknown source reactive pollution precursors.
Motor vehicles are major sources of gas-phase organic carbon, which includes volatile compounds (VOCs) and other with lower vapor pressures. These emissions react in the atmosphere, leading to formation ozone secondary aerosol (SOA). With more chemical detail than previous studies, we report emission factors for over 230 from gasoline diesel via two methods. First use speciated measurements exhaust on-road summer 2010. Second, a fuel composition-based approach quantify uncombusted components...
Motor vehicles are major sources of primary organic aerosol (POA), which is a mixture large number compounds that have not been comprehensively characterized. In this work, we apply recently developed gas chromatography mass spectrometry approach utilizing "soft" vacuum ultraviolet photoionization to achieve unprecedented chemical characterization motor vehicle POA emissions in roadway tunnel with closure >60%. The observed was characterized by carbon atoms (NC), double bond equivalents...
A fuel-based approach is used to estimate long-term trends (1990-2010) in carbon monoxide (CO) emissions from motor vehicles. Non-methane hydrocarbons (NMHC) are estimated using ambient NMHC/CO ratios after controlling for nonvehicular sources. Despite increases fuel use of ∼10-40%, CO running exhaust on-road vehicles decreased by ∼80-90% Los Angeles, Houston, and New York City, between 1990 2010. The ratio was found be 0.24 ± 0.04 mol C/mol over time indicating that both pollutants at a...
Abstract Despite the known biochemical production of a range aromatic compounds by plants and presence benzenoids in floral scents, emissions only few benzenoid have been reported from biosphere to atmosphere. Here, using evidence measurements at aircraft, ecosystem, tree, branch leaf scales, with complementary isotopic labeling experiments, we show that vegetation (leaves, flowers phytoplankton) emits wide variety atmosphere substantial rates. Controlled environment experiments are able...
On- and off-road mobile sources are the dominant contributors to urban anthropogenic volatile organic compound (AVOC) emissions. Analyses of gasoline samples from California for both summer winter indicate significant differences in liquid fuel vapor chemical composition due intentional seasonal adjustments. Ambient concentrations 55 VOCs were measured via situ gas chromatography 2005 Study Organic Aerosols at Riverside (SOAR) during fall. A mass balance analysis was used differentiate...
Aerosol phase state is critical for quantifying aerosol effects on climate and air quality. However, significant challenges remain in our ability to predict quantify during its evolution the atmosphere. Herein, we demonstrate that (liquid, semisolid, solid) exhibits a diel cycle mixed forest environment, oscillating between viscous, semisolid at night liquid with separation day. The viscous nighttime particles existed despite higher relative humidity were independently confirmed by bounce...
Abstract. Decades of policy in developed regions has successfully reduced total anthropogenic emissions gas-phase organic compounds, especially volatile compounds (VOCs), with an intentional, sustained focus on motor vehicles and other combustion-related sources. We examine potential secondary aerosol (SOA) ozone formation our case study megacity (Los Angeles) demonstrate that non-combustion-related sources now contribute a major fraction SOA precursors. Thus, they warrant greater attention...
Abstract. The San Joaquin Valley (SJV) experiences some of the worst ozone air quality in US, frequently exceeding California 8 h standard 70.4 ppb. To improve our understanding trends number violations SJV, we analyze observed relationships between organic reactivity, nitrogen oxides (NOx), and daily maximum temperature southern SJV using measurements made as part at Nexus Air Quality Climate Change 2010 (CalNex-SJV). We find daytime speciated reactivity with respect to OH during CalNex-SJV...
Ozone pollution affects human health, especially in urban areas on hot sunny days. Its basic photochemistry has been known for decades and yet it is still not possible to correctly predict the high ozone levels that are greatest threat. The CalNex_SJV study Bakersfield CA May/June 2010 provided an opportunity examine area surrounded by agriculture. measurement suite included hydroxyl (OH), hydroperoxyl (HO<sub>2</sub>), OH reactivity, which compared with output of a photochemical box model....
Tobacco smoke off-gassing from prior exposure releases contaminants that are equivalent to several cigarettes of secondhand smoke.
Organic aerosol (OA) is a complex mixture of compounds with diverse elemental and structural features, its composition affects health environmental impacts. A detailed speciation the functional group distribution in OA important for constraining atmospheric reaction pathways products, evaluating chemical mechanisms models, understanding We used high-resolution tandem mass spectrometry to perform nontargeted analysis groups from three ambient sites across times day seasons. observed range...
Abstract. Biomass burning is a large source of uncontrolled air pollutants, including particulate matter (i.e., PM2.5), black carbon (BC), volatile organic compounds (VOCs), and monoxide (CO), which have significant effects on quality, human health, climate. Measurements PM2.5, BC, CO made at the Yale Coastal Field Station in Guilford, CT, five other sites metropolitan New York City (NYC) area indicate long-distance transport pollutants from wildfires biomass to surface-level region. Here,...
Air quality policies have made substantial gains by reducing pollutant emissions from the transportation sector. In March 2020, New York City's activities were severely curtailed in response to COVID-19 pandemic, resulting 60–90% reductions human activity. We continuously measured major volatile organic compounds (VOCs) during January–April 2020 and 2021 Manhattan. Concentrations of many VOCs decreased significantly shutdown with variations daily patterns reflective activity perturbations, a...
Anthropogenic organic carbon emissions reporting has been largely limited to subsets of chemically speciated volatile compounds. However, new aircraft-based measurements revealed total gas-phase that exceed oil sands industry-reported values by 1900% over 6300%, the bulk which was due unaccounted-for intermediate-volatility and semivolatile Measured facility-wide represented approximately 1% extracted petroleum, resulting in equivalent from all other sources across Canada combined. These...
As part of the summer 2022 NYC-METS (New York City metropolitan Measurements Emissions and TransformationS) campaign ASCENT (Atmospheric Science Chemistry mEasurement NeTwork) observational network, speciated particulate matter was measured in real time Manhattan Queens, NY, with additional gas-phase measurements. Largely due to observed reductions inorganic sulfate aerosol components over 21st century, summertime composition NYC has become predominantly organic (80-83%). Organic source...
Abstract Furans are a major class of volatile organic compounds emitted from biomass burning. Their high reactivity with atmospheric oxidants leads to the formation secondary aerosol (SOA), including brown carbon (BrC) that can affect global climate via interactions solar radiation. Here, we investigate optical properties and chemical composition SOA generated photooxidation furfural, 2‐methylfuran, 3‐methylfuran under dry (RH < 5%) humid ∼ 50%) conditions in presence nitrogen oxides (NO...