Chemical significance of atmospheric mercury at fishing port compared to urban and suburb in an offshore island

Abstract

This study explored the chemical significance, spatiotemporal variation, and source origins of atmospheric speciated mercury (ASM) at three contexts (urban, suburb, and fishing port) at the Penghu Islands in the Taiwan Strait. Continuous monitoring of 5-min total gaseous mercury (TGM) was used to determine its hourly, daily, and seasonal concentrations. Manual sampling of 12-h gaseous oxidixed mercury (GOM) and particulate bound mercury (PBM) was used to resolve their diurnal and seasonal variation. ASM further correlated with meteorological parameters and criteria air pollutants. Backward trajectories coped with regional fire maps to identify the potential sources of atmospheric mercury. The yearly mean TGM concentration was about 2.9 times higher than the background level (1.4 ng/m3) of Northern Hemisphere. The highest and lowest seasonal TGM concentration appeared in spring and summer, respectively. Asian continental outflows (ACOs) containing mercury-laden contaminants (MLCs) in spring, while polluted air masses were blown from southern Taiwan where heavily industrial complex had in summer, causing the second highest ASM level. In fall, MLCs emitted from the coastal industrial and urban areas were blown from the Korea Peninsula by Asian Northeastern Monsoons (ANMs). In terms of gas-particle partition, TGM was superior to PBM. Moreover, the highest TGM concentration was observed at the fishing port site, and followed by the suburb and urban sites. High TGM concentration peaks were regularly observed at the fishing port site due to the exhausts of fishing boats.