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Purpose: The distribution and speciation of mercury in surface water of East River, Guangdong province, China were investigated. Methods: All told 63 water samples were collected during a bi-weekly sampling campaign from July 15th to 26th, 2009. Results: Total mercury (THg) concentrations in water samples ranged from 11 to 49 ng/L. Maximum levels of THg were measured in the lower reaches of East River, where it passes through a major industrial area adjacent to Dongguang city. Higher ratios of dissolved mercury (THg (aq)) in proportion to THg were restricted to the downstream section of East River. Concentrations of the minor constituent methyl mercury varied in the range from 0.08 to 0.21 ng/L. On average, methyl mercury made up 0.8% and 0.56% of THg (aq) and THg, respectively. Dissolved species dominated the speciation of methyl mercury in proportions up to 81%, which may imply that methyl mercury is largely produced in situ within the river water. Environmental factors (such as water temperature, dissolved oxygen, etc.) are regarded to play an important role in Hg methylation processes were monitored and assessed. Conclusions: In an international perspective, East River must be classified as a polluted river with considerably sources within its industrial areas. The THg (aq) and particle mercury fluxes to the Pearl River Estuary by East River run-off were estimated to be 0.31 ± 0.11 and 0.17 ± 0.13 t/year, respectively. Hence, in total nearly 0.5 t Hg is annually released to the sea from the East River tributary. [ABSTRACT FROM AUTHOR]

Abstract: The Pearl River Delta (PRD) is one of the most industrialized and urbanized regions in China. In order to assess the pollution status of mercury (Hg) in PRD river system, the distribution of total mercury (HgT) and methylmercury (Me-Hg) in sediment from a large river named Dongjiang (DJ) was for the first time investigated. HgT concentrations in sediment increased from the upstream to downstream of Dongjiang area and at most sites of DJ were significantly higher than the background values, which suggested that the DJ was contaminated with Hg, especially in the downstream of DJ. Me-Hg concentrations in sediment of DJ ranged from 0.56 to10.62ng/g, and were significantly correlated with HgT and organic matter. In order to determine the potential Hg contamination sources, typical sediments from different parts of DJ were chosen for Hg isotope analysis. The results showed that the mass-dependent fraction (MDF) in the sediments varied significantly (δ202Hg: −2.35 to−0.60‰), and the mass-independent fraction (MIF) in the sediments also varied considerably (Δ199Hg: −0.02 to −0.27‰). The samples with the highest HgT located in the industrial area had the highest δ202Hg (−1.14‰ to −0.60‰) measured values and insignificant MIF (Δ199Hg: −0.04 to −0.01‰). Meanwhile, the samples with the lowest HgT located in the background area had the lowest δ202Hg (−2.16‰ to −1.55‰) and Δ199Hg (−0.20 to −0.27‰) measured values. Unlike the above two cases are the samples located in the urban area, which have relative lower MDF (δ202Hg: −2.35‰ to −1.96‰) and small but significant MIF (Δ199Hg: −0.10‰ to −0.08‰) with relative higher HgT. We demonstrated that the dominant Hg sources in DJ sediments could be categorized as the regional background, urban and industrial sources. In our study, we demonstrated that Hg stable isotope method could serve as an effective tool for tracing mercury contamination sources in the environment. [Copyright &y& Elsevier]