A5028836020- Atmospheric chemistry and aerosols
- Air Quality and Health Impacts
- Air Quality Monitoring and Forecasting
- Atmospheric Ozone and Climate
- Atmospheric aerosols and clouds
- Atmospheric and Environmental Gas Dynamics
- Vehicle emissions and performance
- Plant responses to elevated CO2
- Advanced oxidation water treatment
- Advanced Photocatalysis Techniques
- Water Quality Monitoring and Analysis
- TiO2 Photocatalysis and Solar Cells
- Indoor Air Quality and Microbial Exposure
- Advanced Chemical Sensor Technologies
- Isotope Analysis in Ecology
- Plant and animal studies
- Ecology and Conservation Studies
- Environmental Impact and Sustainability
- Water Quality and Pollution Assessment
- Odor and Emission Control Technologies
- Environmental and biological studies
- Analytical Chemistry and Chromatography
- Ocean Acidification Effects and Responses
- Species Distribution and Climate Change
- Icing and De-icing Technologies
University of California, Irvine
2015-2024
Irvine University
2016-2024
ORCID
2020
University of California System
2016-2020
Irvine Valley College
2016-2020
University of Colorado Boulder
2017
NSF National Center for Atmospheric Research
2012-2015
Georgia Institute of Technology
2006-2010
Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part the Southern Oxidant Aerosol Study. A large fraction pONs is highly functionalized, possessing between six eight oxygen atoms within each carbon number group, not common first generation alkyl previously reported. Using calibrations for isoprene hydroxynitrates measured molecular compositions, we estimate that account 3% 8% total...
One of the least understood aspects in atmospheric chemistry is how urban emissions influence formation natural organic aerosols, which affect Earth's energy budget. The Amazon rainforest, during its wet season, one few remaining places on Earth where transitions between preindustrial and urban-influenced conditions. Here, we integrate insights from several laboratory measurements simulate secondary aerosols (SOA) using a high-resolution chemical transport model. Simulations show that...
The Korea-United States Air Quality (KORUS-AQ) field study was conducted during May-June 2016. effort jointly sponsored by the National Institute of Environmental Research South Korea and Aeronautics Space Administration United States. KORUS-AQ offered an unprecedented, multi-perspective view air quality conditions in employing observations from three aircraft, extensive ground-based network, ships along with array forecast models. Information gathered is contributing to improved...
Abstract We present OH observations from Nitrogen, Aerosol Composition, and Halogens on a Tall Tower 2011 (NACHTT‐11) held at the Boulder Atmospheric Observatory in Weld County, Colorado. Average levels noon were ~ 2.7 × 10 6 molecules cm −3 2 m above ground level. Nitrous acid (HONO) photolysis was dominant source (80.4%) during this campaign, while alkene ozonolysis (4.9%) ozone (14.7%) smaller contributions to production. To evaluate recycling sources of HO RO , an observationally...
Abstract. The Amazon Basin plays key role in atmospheric chemistry, biodiversity and climate change. In this study we applied nanoelectrospray (nanoESI) ultra-high-resolution mass spectrometry (UHRMS) for the analysis of organic fraction PM2.5 aerosol samples collected during dry wet seasons at a site central Amazonia receiving background air masses, biomass burning urban pollution. Comprehensive spectral data evaluation methods (e.g. Kendrick defect, Van Krevelen diagrams, carbon oxidation...
Significance For isolated regions of the planet, organic peroxy radicals produced as intermediates atmospheric photochemistry have been expected to follow HO 2 rather than NO pathways. Observational evidence, however, has lacking. An accurate understanding relative roles two pathways is needed for quantitative predictions concentrations particulate matter, oxidation capacity, and consequent environmental climate impacts. The results herein, based on measurements, find that ratio reaction...
Abstract. Isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA) can contribute substantially to (OA) concentrations in forested areas under low NO conditions, hence significantly influencing the regional and global OA budgets, accounting, for example, 16–36 % of submicron southeastern United States (SE US) summer. Particle evaporation measurements from a thermodenuder show that volatility ambient IEPOX-SOA is lower than bulk also much known monomer tracer species, indicating...
Abstract. The San Joaquin Valley (SJV) in California experiences persistent air-quality problems associated with elevated particulate matter (PM) concentrations due to anthropogenic emissions, topography, and meteorological conditions. Thus it is important unravel the various sources processes that affect physicochemical properties of PM order better inform pollution abatement strategies improve parameterizations models. During January February 2013, a ground supersite was installed at...
Considerable amounts and varieties of biogenic volatile organic compounds (BVOCs) are exchanged between vegetation the surrounding air. These BVOCs play key ecological atmospheric roles that must be adequately represented for accurately modeling coupled biosphere-atmosphere-climate earth system. One uncertainty in existing models is response BVOC fluxes to an important global change process: drought. We describe diurnal seasonal variation isoprene, monoterpene, methanol from a temperate...
Abstract The Nitrogen, Aerosol Composition, and Halogens on a Tall Tower (NACHTT) field experiment took place during late winter, 2011, at site 33 km north of Denver, Colorado. study included fixed‐height measurements aerosols, soluble trace gases, volatile organic compounds near surface level, as well vertically resolved nitrogen oxides, aerosol composition, gas‐phase acids, halogen species from 3 to 270 m above ground level. There were 1928 individual profiles the three‐week campaign...
Abstract Isoprene dominates global non-methane volatile organic compound emissions, and impacts tropospheric chemistry by influencing oxidants aerosols. emission rates vary over several orders of magnitude for different plants, characterizing this immense biological chemodiversity is a challenge estimating isoprene from tropical forests. Here we present the estimates aircraft eddy covariance measurements Amazonian forest. We report that are three times higher than satellite top-down 35%...
Abstract. Secondary organic aerosol (SOA) formation from ambient air was studied using an oxidation flow reactor (OFR) coupled to mass spectrometer (AMS) during both the wet and dry seasons at Observations Modeling of Green Ocean Amazon (GoAmazon2014/5) field campaign. Measurements were made two sites downwind city Manaus, Brazil. Ambient oxidized in OFR variable concentrations either OH or O3, over ranges hours days (O3) weeks (OH) equivalent atmospheric aging. The amount SOA formed ranged...
Abstract. High levels of fine particulate matter (PM2.5) pollution in East Asia often exceed local air quality standards. Observations from the Korea–United States Air Quality (KORUS-AQ) field campaign May and June 2016 showed that development extreme (haze) occurred through a combination long-range transport favorable meteorological conditions enhanced production PM2.5. Atmospheric models have difficulty simulating PM2.5 chemical composition during haze, which is concern for successful...
Four different plant species, sunflower (Helianthus annuus), western redcedar (Thuja plicata), American sweetgum (Liquidambar styraciflua), and red ironbark (Eucalyptus sideroxylon), were enclosed in glass or Teflon chambers, exposed to temperatures typically ranging from 30 °C 43 °C, their terpenoid emission rates quantified using gas chromatography techniques. The results show that sunflower, redcedar, not significant constitutive monoterpene emitters at °C. Monoterpene emissions remained...
We report measurements of the atmospheric plume emitted by Erebus volcano, Antarctica, renowned for its persistent lava lake. The observations were made in December 2005 both at source, with an infrared spectrometer sited on crater rim, and up to 56 km downwind, using a Twin Otter aircraft; two different measurement platforms, ages sampled ranging from <1 min as long 9 h. Three species (CO, carbonyl sulfide (OCS), SO 2 ) measured air ground. While CO OCS conserved plume, consistent their...
South Korea has recently achieved developed country status with the second largest megacity in world, Seoul Metropolitan Area (SMA). This study provides insights into future changes air quality for rapidly emerging megacities East Asian region. We present total OH reactivity observations SMA conducted at an urban site (May–June, 2015) and a suburban forest (Sep, 2015). The during daytime was observed similar levels (∼15 s<sup>−1</sup>) to those previously reported from other studies. Trace...
Observational evidence of isoprene oxidation shows that nitrogen oxides amplify the OH concentrations over Amazon forest.
Abstract. Biogenic volatile organic compounds (BVOCs) are important components of the atmosphere due to their contribution atmospheric chemistry and biogeochemical cycles. Tropical forests largest source dominant BVOC emissions (e.g. isoprene monoterpenes). In this study, we report total monoterpene flux measurements with a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) using eddy covariance (EC) method at Tapajós National Forest (2.857∘ S, 54.959∘ W), primary...
Abstract. Nitryl chloride (ClNO2) is a radical reservoir species that releases chlorine radicals upon photolysis. An integrated analysis of the impact ClNO2 on regional photochemistry in Seoul metropolitan area (SMA) during Korea–United States Air Quality Study (KORUS-AQ) 2016 field campaign presented. Comprehensive multiplatform observations were conducted aboard NASA DC-8 and at two ground sites (Olympic Park, OP; Taehwa Research Forest, TRF), representing an urbanized forested suburban...
We present a holistic examination of tropospheric OH reactivity (OHR) in South Korea using comprehensive NASA DC-8 airborne measurements collected during the Korea–United States Air Quality field study and chemical transport models. The observed total OHR (tOHR) averaged planetary boundary layer (PBL, &lt;2.0 km) free troposphere was 5.2 s−1 2.0 campaign, respectively. These values were higher than calculated (cOHR, 3.4 s−1, 1.0 s−1) derived from trace-gas observations, indicating...