A5050098004- Atmospheric chemistry and aerosols
- Air Quality and Health Impacts
- Atmospheric and Environmental Gas Dynamics
- Air Quality Monitoring and Forecasting
- Atmospheric Ozone and Climate
- Vehicle emissions and performance
- Atmospheric aerosols and clouds
- Odor and Emission Control Technologies
- Isotope Analysis in Ecology
- Fire effects on ecosystems
- Water Quality Monitoring and Analysis
- Mercury impact and mitigation studies
- Ocean Acidification Effects and Responses
- Microbial Community Ecology and Physiology
- Energy, Environment, and Transportation Policies
- Climate variability and models
- Climate Change and Health Impacts
- Radioactivity and Radon Measurements
- Agriculture, Soil, Plant Science
- Plant responses to elevated CO2
- Meteorological Phenomena and Simulations
- Toxic Organic Pollutants Impact
- Noise Effects and Management
- Analytical chemistry methods development
- Marine and coastal ecosystems
Cooperative Institute for Research in Environmental Sciences
2023-2025
NOAA Chemical Sciences Laboratory
2023-2025
University of Colorado Boulder
2023-2025
University of Colorado System
2025
Planetary Science Institute
2018-2024
University of California, Berkeley
2018-2024
Massachusetts Institute of Technology
2023-2024
Moscow Institute of Thermal Technology
2023
NOAA Earth System Research Laboratory
2023
State Key Joint Laboratory of Environment Simulation and Pollution Control
2017-2018
The heterogeneous hydrolysis of dinitrogen pentoxide (N2O5) is important to understanding the formation particulate nitrate (pNO3–). Measurements N2O5 in surface layer taken at an urban site Beijing are presented here. was observed with large day-to-day variability. High concentrations were determined during pollution episodes co-presence aerosol loads. maximum value 1.3 ppbv (5 s average), associated air mass characterized by a high level O3. uptake coefficients estimated be range...
Despite declines in transportation emissions, urban North America and Europe still face unhealthy air pollution levels. This has challenged conventional understanding of the sources their volatile organic compound (VOC) precursors. Using airborne flux measurements to map emissions a wide range VOCs, we demonstrate that biogenic terpenoid contribute ~60% emitted VOC OH reactivity, ozone, secondary aerosol formation potential summertime Los Angeles this contribution strongly increases with...
Abstract. Particulate nitrate (pNO3-) is an important component of secondary aerosols in urban areas. Therefore, it critical to explore its formation mechanism assist with the planning haze abatement strategies. Here we report vertical measurements NOx and O3 by situ instruments on a movable carriage tower during winter heavy-haze episode (18 20 December 2016) Beijing, China. Based box model simulation at different heights, found that pNO3- via N2O5 heterogeneous uptake was negligible ground...
Abstract. Biomass burning emits an estimated 25 % of global annual nitrogen oxides (NOx), important constituent that participates in the oxidative chemistry atmosphere. Estimates NOx emission factors, representing amount per mass burned, are primarily based on field or laboratory case studies, but sporadic and transient nature wildfires makes it challenging to verify whether these studies represent behavior fires occur earth. Satellite remote sensing provides a unique view earth, allowing...
In China, emissions of ozone (O3)-producing pollutants have been targeted for mitigation to reduce O3 pollution. However, the observed decrease is slower than/opposite expectations affecting health millions people. For a better understanding this failure and its connection with anthropogenic emissions, we quantify summer trends that would occurred had weather stayed constant by applying numerical tool "de-weathers" observations across 31 urban regions (123 cities 392 sites) over 8 years. are...
Los Angeles is a major hotspot for ozone and particulate matter air pollution in the United States. Ozone PM2.5 this region have not improved substantially past decade, despite reduction vehicular emissions of their precursors, NOx volatile organic compounds (VOCs). This "traditional" sources has made current emission mixture pollutant precursors more uncertain. To map quantify wide range VOCs urban area, we performed airborne eddy covariance measurements with wavelet analysis. VOC fluxes...
Abstract. Cooking is a source of volatile organic compounds (VOCs), which degrade air quality. VOCs have been investigated in laboratory and indoor studies, but the contribution cooking to spatial temporal variability urban uncertain. In this study, proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) used identify quantify emission Las Vegas, NV, with supplemental data from Los Angeles, CA, Boulder, CO. Mobile show that long-chain aldehydes, such as octanal nonanal, are...
The declining trend in vehicle emissions has underscored the growing significance of Volatile Organic Compound (VOC) from Chemical Products (VCP). However, accurately representing VOC chemistry simplified chemical mechanisms remains challenging due to its complexity including speciation and reactivity. Previous studies have predominantly focused on VOCs fossil fuel sources, leading an underrepresentation VCP sources. We developed integrated mechanism, RACM2B-VCP, that is compatible with...
Abstract. Volatile chemical products (VCPs) and other non-traditional anthropogenic sources, such as cooking, contribute substantially to the volatile organic compound (VOC) budget in urban areas, but their impact on ozone formation is less certain. This study employs Lagrangian box modeling sensitivity analyses evaluate response sector-specific VOC nitrogen oxide (NOx) emissions two Los Angeles (LA) Basin cities during summer of 2021. The model simulated photochemical processing transport...
Facemasks are increasingly worn during air pollution episodes in China, but their protective effects poorly understood. We aimed to evaluate the filtration efficiencies of N95 facemasks and cardiopulmonary benefits associated with wearing pollution. measured particles ambient six types a manikin headform. The most effective one was used double-blind, randomized, controlled crossover study, involving 15 healthy young adults, conducted 2 days severe Beijing, China. Subjects were asked walk...
The hydroxyl radical (OH) is the primary cleansing agent in atmosphere. abundance of OH cities initiates removal local pollutants; therefore, it serves as key species describing urban chemical environment. We propose a machine learning (ML) approach an efficient alternative to simulation using computationally expensive transport model. ML model trained on parameters simulated from WRF-Chem model, and suggests that six predictive are capable explaining 76% variability. tropospheric NO2...
Despite decades of emission control measures aimed at improving air quality, Los Angeles (LA) continues to experience severe ozone pollution during the summertime. We incorporate cooking volatile organic compound (VOC) emissions in a chemical transport model and evaluate it against observations order improve representation present-day regime LA. Using this updated model, we investigate impact adopting zero-emission vehicles (ZEVs) on with increased confidence. show that mitigating on-road...
The hydroxyl radical (OH) is the most important oxidant on global and local scales in troposphere. Urban OH controls removal rate of primary pollutants triggers production ozone. Interannual trends urban areas are not well documented or understood due to short lifetime high spatial heterogeneity OH. We utilize machine learning with observational inputs emphasizing satellite remote sensing observations predict surface 49 North American cities from 2005 2014. observe changes summertime over...
Abstract According to the hypothesis of aerosol invigoration, higher concentration aerosols in polluted air intensifies storms. A leading theory for explaining such a relationship is warm‐phase which cloudy updrafts that are more readily condense water vapor onto liquid drops, thereby releasing latent heat faster, buoyancies and updraft speeds. For this mechanism work, water‐vapor supersaturations well excess 1% must be typical relatively unpolluted updrafts. Here, supersaturation calculated...
The hydroxyl radical (OH) largely controls the tropospheric self-cleansing capacity by reacting with gases harmful to environment and human health. OH concentrations are determined locally competing production loss processes. Lacking strong observational constraints, models differ in how they balance these processes, such that sign of past future changes is uncertain. In a warmer climate, will increase due its water vapor dependence, partially offset faster OH-methane loss. Weather-sensitive...
Abstract. We describe upgrades to the Berkeley High Resolution (BEHR) NO2 satellite retrieval product. BEHR v3.0B builds on NASA version 3 standard Ozone Monitoring Instrument (OMI) tropospheric product provide a high spatial resolution for domain covering continental United States and lower Canada that is consistent with daily variations in 12 km priori profiles. Other improvements v3.0 include surface reflectance elevation, factors affecting profiles such as lightning anthropogenic...
Abstract. Version 3.0B of the Berkeley High Resolution (BEHR) Ozone Monitoring Instrument (OMI) NO2 product is designed to accurately retrieve daily variation in high-spatial-resolution mapping tropospheric column over continental North America between 25 and 50∘ N. To assess product, we compare against situ aircraft profiles Pandora vertical densities (VCDs). We also WRF-Chem simulation used generate a priori observations. find that using improves VCDs retrieved urban areas relative...
Abstract. Nitrogen oxides (NOx) are principle components of air pollution and serve as important ozone precursors. As the San Joaquin Valley (SJV) experiences some worst quality in United States, reducing NOx emissions is a pressing need, yet quantifying current complicated due to mixture mobile agriculture sources. We performed airborne eddy covariance flux measurements during Re-Evaluating Chemistry Air Pollutants CAlifornia (RECAP-CA) field campaign June 2021. Combining footprint...
Abstract The hydroxyl radical (OH) lies at the nexus of climate and air quality as primary oxidant for both reactive greenhouse gases many hazardous pollutants. To better understand role variability on spatiotemporal patterns OH, we utilize a 13-member ensemble Community Earth System Model version 2-Whole Atmosphere Climate 6 (CESM2-WACCM6), fully coupled chemistry-climate model, spanning years 1950–2014. Ensemble members vary only in their initial conditions state 1950. We focus final...
Abstract. Lightning is an important NOx source representing ∼10 % of the global odd N and a much larger percentage in upper troposphere. The poor understanding spatial temporal patterns lightning contributes to large uncertainty tropospheric chemistry. We implement parameterization using product convective available potential energy (CAPE) precipitation rate (PR) coupled with Kain–Fritsch scheme (KF/CAPE-PR) into Weather Research Forecasting-Chemistry (WRF-Chem) model. Compared cloud-top...
The extent to which emission control technologies and policies have reduced anthropogenic NOx emissions from motor vehicles is large but uncertain. We evaluate a fuel-based inventory for southern California during the June 2021 period, coinciding with Re-Evaluating Chemistry of Air Pollutants in CAlifornia (RECAP-CA) field campaign. A modified version Fuel-based Inventory Vehicle Emissions (FIVE) presented, incorporating 1.3 km resolution gridding new light-/medium-duty diesel vehicle...
Abstract. The hydroxyl radical (OH) plays a central role in tropospheric chemistry, as well influencing the lifetimes of some greenhouse gases. Because limitations our ability to observe OH, we have historically relied on indirect methods constrain its concentrations, trends, and variations but only annual global or semi-hemispheric averages. Recent demonstrated feasibility indirectly constraining OH finer spatio-temporal scales using satellite observations proxies for photochemical drivers...
The hydroxyl radical (OH) sets the oxidative capacity of atmosphere and determines lifetime reactive greenhouse gases such as methane (CH4). response OH to climate warming is influenced by uncertain compensating processes involving weather-sensitive chemistry emissions. In this study, we extend idealized aquaplanet configuration Community Earth System Model (CESM) Atmosphere version 6 (CAM6) include atmospheric (“AquaChem”).  Beyond aquaplanet’s zonally...
The hydroxyl radical (OH) is the dominant tropospheric oxidant and therefore responsible for setting lifetime of several key atmospheric constituents, including methane. Despite its importance, however, there are no global in situ or remote sensing networks that directly observe this species. Methyl chloroform (MCF) inversions, often used to infer interannual variability trends OH, only provide information at hemispheric scales have become less reliable as MCF concentrations decline. This...
Abstract. Nitrogen oxides (NOx) are principle components of air pollution and serve as important ozone precursors. As the San Joaquin Valley (SJV) experiences some worst quality in United States, reducing NOx emissions is a pressing need, yet quantifying current complicated due to mixture mobile agriculture sources. We performed airborne eddy covariance flux measurements during Re-Evaluating Chemistry Air Pollutants California (RECAP-CA) field campaign June 2021. Combining footprint...