Seasonal variation and source identification of atmospheric speciated mercury in an industrial harbor area in East Asia

Abstract

In this study, the pollution characteristics, spatiotemporal variation, and potential sources of atmospheric speciated mercury (ASM) in an industrial harbor area were explored. Gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (PBM) were sampled by a self-designed manual system at three harbor sites in four seasons. The yearly average concentrations of GEM, GOM, and PBM were 6.7 ± 2.0 ng/m3, 244 ± 70 pg/m3, and 410 ± 105 pg/m3, respectively. The seasonal average ASM concentration was in the order of: winter > fall > spring > summer. In terms of species, GEM dominated ASM, while reactive mercury (RM = GOM + PBM) accounted for 6.0–15.7%of ASM, implying that ASM was governed by anthropogenic sources in the harbor area. The highest ASM concentrations were observed at Site Zhonghe (ZH), which is mainly influenced by both ship exhausts and industrial emissions, and positively correlated with CO, NOx, and SO2. In particular, GOM was positively correlated with O3, and negatively correlated with air temperature and relative humidity, showing high impact from atmospheric photochemical reactions. Air masses transporting westerly in spring were mainly from ship exhausts. In summer, air masses transporting from the south were from utility power plants and machinery exhausts. In fall and winter, air masses were transported mainly from the north, blowing by the long-range transport of polluted air masses originated from the north. Both principal component analysis and positive matrix factorization results indicate that coal burning, industrial emissions, and vehicular exhausts are the main contributors to ASM. Site Zhongdao (ZD) was close to the bulk carrier loading and unloading zones and was highly influenced by mobile sources, while Site ZH was mainly influenced by the neighboring industrial complex.