Dimethylmercury in Floodwaters of Mercury Contaminated Rice Paddies

Zhangwei Wang, Ting Sun, Charles T Driscoll, Huan Zhang, Xiaoshan Zhang

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

Dimethyl mercury (CH3HgCH3, DMeHg) has been observed in upwelling marine environments and the deep ocean. However, little is known about the occurrence and mechanisms of DMeHg formation in freshwater environments. In this study, concentrations of dissolved gaseous DMeHg were investigated in floodwaters of rice paddies in China that have been contaminated by mercury from mining. Values of DMeHg in rice paddies were compared with measurements from nearshore surface seawater in the Bohai Gulf. High concentrations of dissolved gaseous DMeHg occurred in rice paddies. Average DMeHg concentration was 12 ± 22 pg L-1 with range of 0.39 to 91 pg L-1 in rice paddies at Shuijing, China, a site impacted by an abandoned mercury mine. These concentrations are comparable to those previously observed in the deep seawater and coastal upwelling environments (2.3-115pg L-1). An alkaline environment was found to be necessary for DMeHg formation in rice paddies. Associated incubation experiments showed that production of DMeHg in paddy soil was limited by Hg availability. Although iron amendments accelerated the production of gaseous methylmercury (MeHg) species to floodwaters, available Hg2+ is crucial for this production in flooded rice paddies. These observations are the first to demonstrate the occurrence of DMeHg and reveal factors affecting DMeHg production in rice paddies. Given the high volatility of DMeHg, these measurements also suggest a source for observations of MeHg in atmospheric deposition and advance understanding of a potentially important aspect of the biogeochemical cycling of Hg.

Original languageEnglish (US)
Pages (from-to)9453-9461
Number of pages9
JournalEnvironmental Science and Technology
Volume53
Issue number16
DOIs
StatePublished - Aug 20 2019

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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