A5037559860- Atmospheric chemistry and aerosols
- Atmospheric and Environmental Gas Dynamics
- Atmospheric Ozone and Climate
- Air Quality and Health Impacts
- Air Quality Monitoring and Forecasting
- Atmospheric aerosols and clouds
- Energy and Environment Impacts
- Climate Change and Health Impacts
- COVID-19 impact on air quality
- Impact of Light on Environment and Health
- Space exploration and regulation
- Oil, Gas, and Environmental Issues
- Maritime Transport Emissions and Efficiency
- Marine and coastal ecosystems
- Energy, Environment, and Transportation Policies
- Porphyrin and Phthalocyanine Chemistry
- Gas Dynamics and Kinetic Theory
- Groundwater and Isotope Geochemistry
- Geochemistry and Geologic Mapping
- Analytical Chemistry and Chromatography
- Mercury impact and mitigation studies
- Vehicle emissions and performance
- Chemical Thermodynamics and Molecular Structure
- demographic modeling and climate adaptation
- Advanced Photocatalysis Techniques
University College London
2018-2025
University of Leicester
2018-2022
Harvard University
2012-2020
Indian Institute of Technology Bombay
2020
Institute for Health Metrics and Evaluation
2020
University of Washington
2020
Pacific Northwest National Laboratory
2020
Dalhousie University
2020
Washington University in St. Louis
2020
Joint Global Change Research Institute
2020
Abstract. Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx ≡ NO + NO2) and biogenic isoprene. Model estimates surface ozone concentrations tend to be biased high region this is concern for designing effective emission control strategies meet air quality standards. We use detailed chemical observations from SEAC4RS aircraft campaign August September 2013, interpreted with GEOS-Chem transport model at 0.25° ×...
Abstract. Global anthropogenic emission inventories remain vital for understanding the sources of atmospheric pollution and associated impacts on environment, human health, society. Rapid changes in today's society require that these provide contemporary estimates multiple pollutants with both source sector fuel type information to understand effectively mitigate future impacts. To fill this need, we have updated open-source Community Emissions Data System (CEDS) (Hoesly et al., 2019)...
Abstract. Mercury (Hg) is emitted to the atmosphere mainly as volatile elemental Hg0. Oxidation water-soluble HgII plays a major role in Hg deposition ecosystems. Here, we implement new mechanism for atmospheric Hg0 ∕ redox chemistry GEOS-Chem global model and examine implications budget patterns. Our simulation includes coupling of an ocean general circulation (MITgcm), enabling 3-D representation atmosphere–ocean cycling. We find that atomic bromine (Br) marine organobromine origin main...
Abstract. Isoprene emitted by vegetation is an important precursor of secondary organic aerosol (SOA), but the mechanism and yields are uncertain. Aerosol prevailingly aqueous under humid conditions typical isoprene-emitting regions. Here we develop aqueous-phase for isoprene SOA formation coupled to a detailed gas-phase oxidation scheme. The based on reactive uptake coefficients (γ) water-soluble products, including sensitivity acidity nucleophile concentrations. We apply this simulation...
Abstract We use a global chemical transport model (GEOS‐Chem) to interpret aircraft curtain observations of black carbon (BC) aerosol over the Pacific from 85°N 67°S during 2009–2011 HIAPER (High‐Performance Instrumented Airborne Platform for Environmental Research) Pole‐to‐Pole Observations (HIPPO) campaigns. Observed concentrations are very low, implying much more efficient scavenging than is usually implemented in models. Our simulation with source 6.5 Tg −1 and mean tropospheric lifetime...
Abstract. Formation of organic nitrates (RONO2) during oxidation biogenic volatile compounds (BVOCs: isoprene, monoterpenes) is a significant loss pathway for atmospheric nitrogen oxide radicals (NOx), but the chemistry RONO2 formation and degradation remains uncertain. Here we implement new BVOC mechanism (including updated isoprene chemistry, monoterpene particle uptake RONO2) in GEOS-Chem global chemical transport model with ∼ 25 × km2 resolution over North America. We evaluate using...
Anthropogenic pollution in Africa is dominated by diffuse and inefficient combustion sources, as electricity access low motorcycles outdated cars proliferate. These sources are missing, out-of-date, or misrepresented state-of-the-science emission inventories. We address these deficiencies with a detailed inventory of Diffuse Inefficient Combustion Emissions (DICE-Africa) for 2006 2013. Fuelwood energy the largest source DICE-Africa, but grows from to 2013 at slower rate than charcoal...
Abstract. Chemical transport models have historically struggled to accurately simulate the magnitude and variability of observed organic aerosol (OA), with previous studies demonstrating that significantly underestimate concentrations in troposphere. In this study, we explore two different model OA schemes within standard GEOS-Chem chemical evaluate simulations against a suite 15 globally distributed airborne campaigns from 2008 2017, primarily spring summer seasons. These include ATom,...
Abstract. The National Emission Inventory (NEI) of the US Environmental Protection Agency (EPA) reports a steady decrease in NOx emissions over 2005–2017 period at rate 0.1 Tg N a−1 (53 % period), reflecting sustained efforts to improve air quality. Tropospheric NO2 columns observed by satellite-based Ozone Monitoring Instrument (OMI) show until 2009 but flattening afterward, which has been attributed emissions, contradicting NEI. We here that reported NEI is fact largely consistent with...
Tropical cities are experiencing rapid growth but lack routine air pollution monitoring to develop prescient quality policies. Here, we conduct targeted sampling of recent (2000s 2010s) observations pollutants from space-based instruments over 46 fast-growing tropical cities. We quantify significant annual increases in nitrogen dioxide (NO 2 ) (1 14%), ammonia (2 12%), and reactive volatile organic compounds 11%) most cities, driven almost exclusively by emerging anthropogenic sources rather...
Abstract. We use 2005–2009 satellite observations of formaldehyde (HCHO) columns from the OMI instrument to infer biogenic isoprene emissions at monthly 1 × 1° resolution over African continent. Our work includes new approaches remove biomass burning influences using absorbing aerosol optical depth data (to account for transport fire plumes) and anthropogenic AATSR persistent small-flame fires (gas flaring). The resulting HCHO (ΩHCHO) follow closely distribution vegetation patterns in...
Satellite observations of formaldehyde (HCHO) columns provide top-down constraints on emissions highly reactive volatile organic compounds (HRVOCs). This approach has been used previously in the US to estimate isoprene from vegetation, but application anthropogenic stymied by lack a discernable HCHO signal. Here we show that temporal oversampling data Ozone Monitoring Instrument (OMI) for 2005–2008 enables detection urban and industrial plumes eastern Texas including Houston, Port Arthur,...
Exposure to ambient fine particulate matter (PM2.5) is a leading risk factor for the global burden of disease. However, uncertainty remains about PM2.5 sources. We use chemical transport model (GEOS-Chem) simulation 2014, constrained by satellite-based estimates interpret globally dispersed mass and composition measurements from ground-based surface network (SPARTAN). Measured site mean varies substantially secondary inorganic aerosols (2.4–19.7 μg/m3), mineral dust (1.9–14.7...
We interpret in situ and satellite observations with a chemical transport model (GEOS-Chem, downscaled to 0.1° × 0.1°) understand global trends population-weighted mean composition of fine particulate matter (PM2.5). Trends observed simulated PM2.5 over 1989-2013 are highly consistent for (-2.4 vs -2.4%/yr), secondary inorganic aerosols (-4.3 -4.1%/yr), organic (OA, -3.6 -3.0%/yr) black carbon -3.9%/yr) North America, as well sulfate (-4.7 -5.8%/yr) Europe. Simulated 1998-2013 also have...
Abstract Satellite observations of formaldehyde (HCHO) columns provide top‐down information on emissions highly reactive volatile organic compounds (VOCs). We examine the long‐term trends in HCHO observed by Ozone Monitoring Instrument from 2005 to 2014 across North America. Biogenic isoprene is dominant source HCHO, and its emission has a large temperature dependence. After correcting for this dependence, we find general pattern increases much America but decreases southeastern U.S. Over...
We use formaldehyde (HCHO) vertical column measurements from the Scanning Imaging Absorption spectrometer for Atmospheric Chartography (SCIAMACHY) and Ozone Monitoring Instrument (OMI), a nested‐grid version of GEOS‐Chem chemistry transport model, to infer an ensemble top‐down isoprene emission estimates tropical South America during 2006, using different model configurations assumptions in HCHO air‐mass factor (AMF) calculation. Scenes affected by biomass burning are removed on daily basis...
Abstract. Glyoxal (CHOCHO) is produced in the atmosphere by oxidation of volatile organic compounds (VOCs). Like formaldehyde (HCHO), another VOC product, it measurable from space solar backscatter. Isoprene emitted vegetation dominant source CHOCHO and HCHO most world. We use aircraft observations SENEX campaign over southeast US summer 2013 to better understand time-dependent yield isoprene oxidation, its dependence on nitrogen oxides (NOx ≡ NO + NO2), behavior CHOCHO–HCHO relationship,...
Abstract The inorganic fraction of fine particles affects numerous physicochemical processes in the atmosphere. However, there is large uncertainty its burden and composition due to limited global measurements. Here, we present observations from eleven different aircraft campaigns around globe investigate how aerosol pH ammonium balance change polluted remote regions, such as over oceans. Both parameters show increasing acidity with remoteness, at all altitudes, decreasing about 3 −1 almost...
Detailed examination of the impact modern space launches on Earth's atmosphere is crucial, given booming investment in industry and an anticipated tourism era. We develop air pollutant emissions inventories for rocket re-entry reusable components debris 2019 a speculative scenario based recent billionaire race. This we include global GEOS-Chem model coupled to radiative transfer determine influence stratospheric ozone (O3) climate. Due surge re-entering components, nitrogen oxides from...
Abstract The dramatic and sudden reduction in anthropogenic activity due to lockdown measures the UK response COVID-19 outbreak has resulted a concerted effort estimate local regional changes air quality, though underlying emissions remain uncertain. Here we combine satellite observations of tropospheric NO 2 from TROPOspheric Monitoring Instrument Goddard Earth Observing System (GEOS)-Chem 3D chemical transport model that x declined nationwide by ∼20% during (23 March 31 May 2020)....
A method is developed to estimate global NO2 and SO2 dry deposition fluxes at high spatial resolution (0.1°×0.1°) using satellite measurements from the Ozone Monitoring Instrument (OMI) on Aura satellite, in combination with simulations Goddard Earth Observing System chemical transport model (GEOS-Chem). These maps for 2005–2007 provide a data set use examining regional budgets of deposition. In order properly assess scale, account geospatial character background offsets retrieved columns....
Nigeria has a high population density and large fossil fuel resources but very poorly managed energy infrastructure. Satellite observations of formaldehyde (HCHO) glyoxal (CHOCHO) reveal sources anthropogenic nonmethane volatile organic compounds (NMVOCs) from the Lagos megacity oil/gas operations in Niger Delta. This is supported by aircraft over satellite methane carbon monoxide (CO) nitrogen dioxide (NO2) show seasonal emissions open fires December–February (DJF). Ventilation central...
Abstract. Formation of ozone and organic aerosol in continental atmospheres depends on whether isoprene emitted by vegetation is oxidized the high-NOx pathway (where peroxy radicals react with NO) or low-NOx pathways alternate channels, mostly HO2). We used mixed layer observations from SEAC4RS aircraft campaign over Southeast US to test ability GEOS-Chem chemical transport model at different grid resolutions (0.25° × 0.3125°, 2° 2.5°, 4° 5°) simulate this chemistry under high-isoprene,...