Air pollution kills – worldwide more than 6 million people per year. Our research focuses on better understanding the formation, transformation and properties of gas and particle-phase pollutants, helping to develop effective policy actions aimed at mitigating pollutant concentrations and their adverse effects. Current specific research topics are summarized below.

Tropospheric chlorine chemistry
Hydroxyl (OH) and ozone (O3) are the most abundant atmospheric oxidants, but chlorine atoms (Cl) are much more reactive and can oxidize volatile organic compounds (VOC) extremely quickly. Cl can also initiate radical propagation pathways which generate OH as secondary radical. We conduct experiments on the formation of PM and ozone from Cl-initiated oxidation of several different hydrocarbon precursors, and to measure the production of reactive chlorine from heterogeneous chemistry on chloride containing particles. Current analysis focuses on the molecular composition of gas and particle-phase products, understanding reaction mechanisms, and quantifying the effects of Cl and OH.

Formation and fate of alkyl nitrates
Alkyl nitrates (RONO2) play an important role in tropospheric chemistry; for example, they can act as sinks and sources of nitrogen oxides (NO + NO2 = NOx) and thereby affect the formation of tropospheric ozone and organic particulate matter. Ongoing work focuses on the formation, gas-particle partitioning and fate of alkyl nitrates formed during the oxidation of different hydrocarbon precursors.

Air pollution in New Delhi, India
(Collaboration with Dr. Joshua Apte in the UT Austin Department of Civil, Environmental and Architectural Engineering.) Our research groups are taking measurements of particulate matter (PM) concentrations and composition at an ambient measurement station in New Delhi, India. New Delhi is the second most populated city in the world and is plagued by severe air pollution, with particulate matter concentrations routinely reaching several hundred micrograms per cubic meter. We are among the first to bring advanced mass spectrometric instrumentation to New Delhi, which allow for detailed source apportionment of the ambient PM at high time resolution. We have been collecting near continuous measurements since January 2017.

Effects of hydraulic fracturing activity on atmospheric chemistry
The use of horizontal drilling and hydraulic fracturing has greatly increased production and decreased the cost of natural gas in the United States, but the environmental impacts of this activity are poorly understood. We conducted a series of experiments in which we oxidized evaporated flow back wastewater and observed significant production of ozone and particulate matter.

Chemistry of indoor environments
Humans spend most of their time indoors; thus, the chemistry of indoor environments has important effects on human health. We have conducted measurements inside of a gymnasium at UT Austin and are scheduled to participate in a large collaborative measurement campaign at the UT Austin indoor air test house in June 2018.

Air pollution health effects on a cellular level
(Collaboration with Dr. Lydia Contreras in the UT Austin McKetta Department of Chemical Engineering.) We have conducted controlled experiments exposing human lung cells to airborne pollutants. Our collaborators are analyzing biomarkers to understand the cells’ response to these environmental stressors. This work will provide insights into the cellular mechanisms through which air pollutants affect human health.

We use several instruments to identify and quantify species in the gas and particle-phase, including a high-resolution time of flight chemical ionization mass spectrometer (HR-ToF-CIMS) coupled to a Filter Inlet for Gases and Aerosols (FIGAERO) an aerosol chemical speciation monitor (ACSM).