Research

Aerosol particles are ubiquitous in the atmosphere, affecting climate, air quality, and public health. Organic aerosols account for a major fraction of fine particulate matter in the atmosphere. Formation and growth of secondary organic aerosols (SOA) is triggered by reaction of ozone and OH radicals with volatile organic compounds emitted from various biogenic and anthropogenic sources followed by condensation of oxidation products. Multiphase chemistry deals with chemical reactions, transport processes, and transformations between gaseous, liquid, and solid matter. These processes are essential for Earth system science and climate research as well as for life and health sciences on molecular and global levels, bridging a wide range of spatial and temporal scales from below nanometers to thousands of kilometers and from less than nanoseconds to years. Knowledge of the mechanisms and kinetics of these processes is also required to address societally relevant questions of global environmental change and public health.

– Gas uptake, formation, evolution and partitioning of organic aerosols

(Shiraiwa et al., PNAS, 2011)

Organic aerosols can adopt liquid, semi-solid, or solid phase states, depending on chemical composition and environmental conditions. Using the kinetic multi-layer models of surface and bulk chemistry and gas-particle interactions (KM-SUB/KM-GAP), we study how the interplay of phase state, water content, and thermodynamic mixing affects formation, partitioning, and chemical transformation of secondary organic aerosols.

We also apply machine learning to predict properties of atmospheric compounds. Please see our project page AzothAI. We recently developed the tgBoost model that can predict glass transition temperature of organic compounds.

– Multiphase chemical processes at skin and indoor air quality

Heterogeneous reactions of ozone with human skin lipids and indoor surfaces can lead to generation of semi-volatile compounds and subsequent SOA formation, strongly affecting chemical composition and distribution in indoor environments. We developed the kinetic multi-layer model of multiphase chemistry at the skin to quantify skin ozonolysis products in indoor environments. PI is leading a new modeling consortium of chemistry in indoor environments (MOCCIE), which aims at developing comprehensive and integrated physicochemical models that include a realistic representation of gas, aerosol and surface chemistry and how occupants, indoor activities and buildings influence indoor chemical processes. We assess gaps in our fundamental understanding of indoor chemistry focusing on impacts of reactions of indoor oxidants with skin as well as oxidation of volatile organic compounds emitted by cleaning activities. Please see the MOCCIE project HP.

(Lakey et al., Indoor Air, 2017)

– Reactive Oxygen Species/Intermediates (ROS/ROI) and their health effects

Reactive oxygen species (ROS) play a central role in atmospheric and physiological processes. We detect and quantify ROS and free radicals associated with atmospheric aerosol particles by acellular assys, mass spectrometery, and electron paramagnetic resonance spectrometry. By kinetic modeling and laboratory experiments, we investigate multiphase chemical processes in lung lining fluid upon and deposition of atmospheric oxidants and particulate matter.

ROS
(Pöschl & Shiraiwa, Chem. Rev., 2015)