Route-based chemical significance and source origin of marine PM2.5 at three remote islands in East Asia: Spatiotemporal variation and long-range transport

Abstract

We explored the route-based chemical significance, spatial distribution, temporal variation, and source origin of fine particles (PM2.5) in East Asia. Marine PM2.5 was sampled at three remote islands in the Taiwan Strait (TS) and the South China Sea (SCS) to identify their chemical significance. High PM2.5 concentrations concurred with LRT of northerly polluted air. Moreover, daytime PM2.5 levels were mostly greater than nighttime. Secondary inorganic aerosols (SIAs) accounted for 42.4–79.9% of water-soluble ions (WSIs) in PM2.5, which were commonly higher in spring and winter. Although crustal elements suppressed the metallic contents of PM2.5, trace elements (V, Cr, Mn, Ni, Zn, and Cd) came dominantly from anthropogenic origins. Additionally, OC/EC ratios >2.0 were observed due to higher organic carbon (OC) than elemental carbon (EC) during the Asian Northeastern Monsoons (ANMs) commonly in spring and winter. Levoglucosan and oxalic acid were, respectively, the most abundant anhydrosugars (ASs) and organic acids (OAs) in PM2.5, and both descended from the north to the south. The mass ratios of malonic and succinic acids (M/S) were in the range of 0.95–1.41, suggesting a high correlation of marine PM2.5 with secondary organic aerosols (SOAs). Source resolution of PM2.5 showed that sea salts, fugitive dust, mobile sources, secondary sulfate and nitrate were the major sources of PM2.5. In particular, anthropogenic origins and biomass burning (BB) contributed notably to PM2.5 during the ANMs. Overall, compared to natural sources (21–48%), anthropogenic sources (25–57%) contributed more to marine PM2.5 in East Asia.