Project No: 16209022

Title: Highly oxygenated products from aromatic VOCs oxidation in the urban environment and their impacts on air quality

Principal Investigator: Prof. Zhe WANG

Co-Investigator: Prof. Kin-fai HO, Prof. Tao WANG, Prof. Jianzhen YU

Abstract:

Volatile organic compounds (VOCs) are the key precursors of photochemical ozone (O3) and secondary organic aerosols (SOA) in urban areas, and have profound impacts on air quality, human health, and climate change. Anthropogenic VOCs emitted from traffic-related and industrial activities often consist of many aromatic compounds, which have higher reactivities and O3 formation potential than other VOC species. High but variable yields of SOA from aromatic VOCs have been reported, and air quality models tend to underestimate the formation of SOA from aromatic precursors and face continued challenges in predicting the oxidation products to match the ambient measurements. Large knowledge gaps still exist in the oxidation pathways of different aromatic VOCs and the oxygenated products, especially under high NOx conditions in urban environments. Furthermore, much is uncertain about the subsequent impacts of those highly oxygenated products. Recent laboratory studies have reported the formation of highly oxygenated organic molecules (HOMs) via the photo-oxidation of aromatic VOCs, and the formation of nitrogen-containing products in the presence of NOx. These products and processes could significantly contribute to SOA and photochemistry in urbanized regions with abundant levels of aromatic VOCs and NOx, such as Hong Kong and the Pearl River Delta region. We propose to characterize the processes and key products of aromatic VOCs oxidation under high NOx conditions in Hong Kong by combining ambient observation, in-situ oxidation experiments, and laboratory simulations. We will first conduct ambient measurements to characterize and quantify the key oxidation products from aromatic precursors at the molecular level using state-of-the-art instruments. We will perform in-situ oxidation experiments using ambient air to characterize the formation potential and yields of different oxygenated products from ambient precursors. Controlled laboratory experiments will be performed to identify the crucial oxidation pathways and evaluate the impacts of highly oxygenated products on photochemistry and SOA formation. This proposed project will improve our understanding of the atmospheric oxidation and fates of aromatic VOCs, and the formation of HOMs and organic nitrates in polluted urban environments. The anticipated results will provide valuable information to policymakers for developing effective control measures on aromatic VOCs to mitigate photochemical O3 and haze pollution in urbanized subtropical regions.