Air pollution kills – worldwide more than 8 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, UC Berkeley)
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 allows for detailed source apportionment of the ambient PM at high time resolution. We have been collecting near-continuous measurements since January 2017.
Indoor air quality impacts of widespread disinfection
(Collaboration with Drs. Atila Novoselac and Pawel Misztal, UT Austin)
The current COVID-19 pandemic has necessitated the wide-spread use of disinfectants without thorough studies on personal protection during disinfection, the longer-term indoor air quality effects, or human health impacts. Public buildings including schools and daycares are fogged periodically with hospital-grade disinfectants, especially as some school districts are pressured to open schools for in-person instruction in spite of the ongoing pandemic. There is no guidance on mask use during disinfection or indoor air quality remediation post disinfection, and there is little knowledge on health impacts due to disinfectant exposure.
We have been conducting experiments to measure air quality changes during disinfection and to observe the interaction between disinfectants and masks. We expect that some masks decrease inhalation exposure to disinfection byproducts, while others may increase exposure via adsorption of cleaning product vapors to the mask and by addition of moisture due to exhalation. One objective of this study is to identify risks for different types of masks and cleaning products and make recommendations on how often to change the masks or mask components during disinfection.