Sources and oxidative potential of water-soluble humic-like substances (HULIS_WS) in fine particulate matter (PM_2.5) in Beijing

• Main Authors: Y. Ma, Y. Cheng, X. Qiu, G. Cao, Y. Fang, J. Wang, T. Zhu, J. Yu, D. Hu
• Format: Article
• Language: English
• Published: Copernicus Publications 2018-04-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://www.atmos-chem-phys.net/18/5607/2018/acp-18-5607-2018.pdf
• ISSN: 1680-7316; 1680-7324

Water-soluble humic-like substances (HULIS_WS) are a major redox-active component of ambient fine particulate matter (PM_2.5); however, information on their sources and associated redox activity is limited. In this study, HULIS_WS mass concentration, various HULIS_WS species, and dithiothreitol (DTT) activity of HULIS_WS were quantified in PM_2.5 samples collected during a 1-year period in Beijing. Strong correlation was observed between HULIS_WS and DTT activity; both exhibited higher levels during the heating season than during the nonheating season. Positive matrix factorization analysis of both HULIS_WS and DTT activity was performed. Four combustion-related sources, namely coal combustion, biomass burning, waste incineration, and vehicle exhausts, and one secondary factor were resolved. In particular, waste incineration was identified as a source of HULIS_WS for the first time. Biomass burning and secondary aerosol formation were the major contributors ( >  59 %) to both HULIS_WS and associated DTT activity throughout the year. During the nonheating season, secondary aerosol formation was the most important source, whereas during the heating season, the predominant contributor was biomass burning. The four combustion-related sources accounted for  >  70 % of HULIS_WS and DTT activity, implying that future reduction in PM_2.5 emissions from combustion activities can substantially reduce the HULIS_WS burden and their potential health impact in Beijing.