| 摘要: | 摘要： Thirty-four weekly rainwater samples were collected in 2009 at Pengjiayu, a remote islet in the subtropical Northwest (NW) Pacific Ocean, to study the distribution of rainwater mercury (Hg) concentrations and associated wet deposition fluxes. This is the first study concerning wet Hg deposition to the subtropical NW Pacific Ocean downwind of the East Asian continent, which is the major source region for Hg emissions worldwide. Sample Hg concentrations ranged from 2.25 to 22.33 ng L−1, with a volume-weighted mean (VWM) concentration of 8.85 ng L−1. The annual wet Hg deposition flux was 10.18 μg m−2, about 2.5 times the fluxes measured at sites on the Pacific coast of the USA, supporting the hypothesis that deposition is higher in the western than in the eastern Pacific. Seasonal VWM concentrations were 7.23, 11.58, 7.82, and 9.84 ng L−1, whereas seasonal wet deposition fluxes were 2.14, 3.45, 2.38, and 2.21 μg m−2, for spring, summer, fall and winter, respectively. Higher summer wet Hg deposition was a function of both higher rainwater Hg concentration and greater rainfall. The seasonal pattern of rainwater Hg concentrations was the opposite of the general seasonal pattern of the East Asian air pollutant export. Since there is no significant anthropogenic Hg emission source on the islet of Pengjiayu, the observed high summertime rainwater Hg concentration hints at the importance of Hg0 oxidation and/or scavenging of upper-altitude reactive gaseous Hg (RGM) by deep convection. Direct anthropogenic RGM emissions from the East Asian continent may not contribute significantly to the rainwater Hg concentrations, but anthropogenic Hg0 emissions could be transported to the upper troposphere or marine boundary layer (MBL) where they can be oxidized to produce RGM, which will then be effectively scavenged by cloud water and rainwater. •The first year-round data of wet Hg deposition to the subtropical NW Pacific Ocean downwind of East Asia.•Both concentrations and depositions of rainwater Hg are higher in summer.•Enhanced Hg0 oxidation and scavenging of upper-altitude RGM by deep convection in summer are the likely causes.•Our data indicate higher wet Hg deposition to the western than to the eastern Pacific.
出版者： Kidlington: Elsevier Ltd
出版日期： 2013-10-01
出處： Atmospheric environment (1994), 2013-10, Vol.77, p.474-481
資源來源： ScienceDirect
版權： 2013 Elsevier Ltd
版權： 2014 INIST-CNRS
識別號： ISSN: 1352-2310
識別號： EISSN: 1873-2844
識別號： DOI: 10.1016/j.atmosenv.2013.05.038 |
