Sources and oxidative potential of water-soluble humic-like substances (HULISsubWS/sub) in fine particulate matter (PMsub2.5/sub) in Beijing

摘要

Water-soluble humic-like substances (HULISsubWS/sub) are a major redox-active component of ambient fine particulate matter (PMsub2.5/sub); however, information on their sources and associated redox activity is limited. In this study, HULISsubWS/sub mass concentration, various HULISsubWS/sub species, and dithiothreitol (DTT) activity of HULISsubWS/sub were quantified in PMsub2.5/sub samples collected during a 1-year period in Beijing. Strong correlation was observed between HULISsubWS/sub and DTT activity; both exhibited higher levels during the heating season than during the nonheating season. Positive matrix factorization analysis of both HULISsubWS/sub 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 HULISsubWS/sub for the first time. Biomass burning and secondary aerosol formation were the major contributors (? 59?%) to both HULISsubWS/sub 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 HULISsubWS/sub and DTT activity, implying that future reduction in PMsub2.5/sub emissions from combustion activities can substantially reduce the HULISsubWS/sub burden and their potential health impact in Beijing.