Abstract
Abstract. The spatial and temporal distribution patterns of mercury (Hg) in precipitation were investigated in the core urban areas of Chongqing, China. During the period from July 2010 to June 2011, total mercury (THg) and methyl mercury (MeHg) concentrations in precipitation were analysed from three sampling sites. Our results suggested that the volume-weight mean THg and MeHg concentrations in precipitation were 30.67 ng l−1 and 0.31 ng l−1, respectively. The proportion of MeHg in THg ranged from 0.1% to 7.6% with a mean value of 1.3%. THg and MeHg concentrations showed seasonal variations, while the highest THg value was measured in winter. Contrarily, the highest MeHg concentration was observed in autumn. Additionally, a geographically gradual decline of THg concentration in precipitation was observed from the downtown to the suburb, then to the controlled site in the city. 5 mm rainfall might be a threshold for the full wash-out capability. Rainfall above 5 mm may have a diluting effect for the concentrations of THg. Moreover, the current research implies that the coal combustion and motor vehicles could be the dominant sources for Hg in the precipitation.
Highlights
Mercury (Hg) pollution, a global issue, poses potential threats to human health and wildlife (National Research Council, 2000)
The mean concentration of THg in core urban area, Chongqing was close to that reported in Wujiang River Basin, Guizhou, China (Guo et al, 2008), but significantly higher than those reported in some remote areas such as Mt
From July 2010 to June 2011, THg and MeHg concentrations in precipitation were investigated in the core urban areas of Chongqing, a traditional industrial city consuming large amount of coal as the major fuel source (70 % of energy consumption)
Summary
Mercury (Hg) pollution, a global issue, poses potential threats to human health and wildlife (National Research Council, 2000). Hg species, including gaseous element mercury (Hg0), reactive gaseous mercury (RGM), and particulate mercury (PHg), are commonly represented in the atmosphere (Lindberg et al, 2007). The primary mechanisms for wet deposition are: (1) in-cloud oxidation of Hg0 by O3, (2) gas-phase oxidation of Hg0 by ·OH and O3 followed by cloud-droplet uptake. Dissolved mercury (DHg) and PHg are the major forms of Hg in precipitation, where the later one can be deposited through cloud-droplet/precipitation scavenging activity (Lindberg et al, 2007). The understanding on the sources of MeHg in atmosphere or precipitation is very limited (Hammerschmidt et al, 2007). Hammerschmidt et al (2007) found that MeHg in precipitation could be derived from the aqueous phase methylation through a reaction between labile Hg(II) complexes and (an) unknown methylating agent(s)
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