Project No: 15265516

Title: Heterogeneous uptake of glyoxal and methylglyoxal by ambient wet aerosols and cloud droplets in a polluted subtropical environment: direct field measurement in Hong Kong

Principal Investigator: Prof. Zhe WANG

Co-Investigator: Prof. Guo, Jia; Prof. Tao Wang

Abstract:

Secondary organic aerosol (SOA) is a ubiquitous and important constituent of atmospheric aerosols in both urban and rural environment, and has adverse impacts on human health, visibility and climate change. Current atmospheric chemistry models face large challenge in predicting SOA formation to match the field observation because of uncertainties in sources, precursors, formation pathways, and products identification. In addition to the traditional mechanism of gas-phase oxidation followed by gas-particle conversion, recent studies have revealed that heterogeneous and aqueous-phase reactions could also contribute to substantial SOA production. Yet our understanding on this heterogeneous pathway is far from complete, significant knowledge gaps remain in the reactivity of different organic precursors on aerosols and cloud droplets, as well as in the subsequent aqueous production of low-volatile products. Due to their contribution to SOA formation, these heterogeneous processes may also play important roles in the severe particulate and haze pollution in many polluted areas, including Hong Kong and China, which has not been well addressed. Therefore, we propose to conduct field measurements of heterogeneous processes of representative precursors (i.e., glyoxal and methylglyoxal) by using in-situ aerosol flow tube and high resolution real-time mass spectrometer, followed by modeling analysis. The goal is to determine the heterogeneous reactive uptake of glyoxal and methylglyoxal on ambient wet aerosols and cloud droplets in the polluted subtropical environment, to investigate the evolution and partitioning of these carbonyls among gas, aerosols and cloud droplets, and to understand the aqueous-phase reactions and their impacts on SOA formation in Hong Kong. This study will help fill the knowledge gaps on heterogeneous formation of SOA in the costal environment with co-existence of high anthropogenic and natural precursors, and high humidity. It also can be used to improve the performance of current air quality models which are used in the formulation of pollution-control measures.