Project No: 16212017
Title: Quantifying Total Organic Sulfur and Characterizing Organosulfates in Atmospheric Aerosols in the Pearl River Delta Region, China
PI: Prof. Yu, Jianzhen CI: Prof. Li, Xiang-dong; Prof. Tong, Rongbiao
Organosulfates are ubiquitous components of particulate matter (PM) in the atmosphere, formed from organic compounds or their oxidation products interacting with acidic sulfate particles. The Pearl River Delta (PRD) is a fast-developing and heavily polluted region in South China, burdened with excessive emissions of sulfur dioxide (precursor of PM sulfate) and volatile organic compounds (VOCs). In addition, the PRD has an active biosphere contributing significant emissions of biogenic VOCs (BVOCs). As a result, organosulfates are likely an important contribution to PM pollution in the PRD. Quantitative field data such as total organic sulfur (OS) content and abundance of individual organosulfates are needed for assessing their environmental impact but these data are lacking. The bottlenecks are a lack of a proper method for determining total OS and a shortage of authentic standards for quantification of individual OS compounds. We propose to develop a suitable analytical scheme to directly measure OS by removing the inorganic sulfate first followed by separate quantification of water-insoluble OS and water-soluble OS. Once the method is developed and tested, it will be applied to analyze the total OS in archived filters that we have collected at four locations of different atmospheric pollution characteristics in the PRD. The results will allow us to assess the mass contributions of OS compounds to PM2.5 pollution and spatiotemporal variations in the region. The lack of authentic standards will be initially tackled through organic synthesis of a series of BVOC-derived organosulfates due to their importance in the PRD. Four monoterpene-derived organosulfates have already been synthesized and more will be made through this project. The secure and sufficient supply of these synthetic standards will enable us to provide standards for their absolute quantification using liquid chromatography-mass spectrometric analysis. Efforts to quantify individual OS compounds will focus on the BVOC-derived organosulfates with synthetic standards and the newly discovered alkyl sulfates for which commercial standards are available. The quantitative capability for individual organosulfates will be used to study their diurnal variation characteristics. Such studies could offer insights into major factors (such as aerosol liquid water content, type of atmospheric oxidants) influencing the sulfonation process. The atmospheric research community will benefit from the synthetic methods for the preparation of organosulfates and analytical methods to be developed through this research. This in turn will facilitate understanding of the environmental and health impact of PM pollution in city clusters of China.