Methyl and Total Mercury in Different Media and Associated Fluxes in a Watershed Forest, Southwest China

Hongxia Du, Ming Ma, Tao Sun, Siwei An, Yasuo Igarashi and Dingyong Wang
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Hongxia Du: College of Resources and Environment, Southwest University, Chongqing 400715, China
Ming Ma: College of Resources and Environment, Southwest University, Chongqing 400715, China
Tao Sun: College of Resources and Environment, Southwest University, Chongqing 400715, China
Siwei An: College of Resources and Environment, Southwest University, Chongqing 400715, China
Yasuo Igarashi: College of Resources and Environment, Southwest University, Chongqing 400715, China
Dingyong Wang: College of Resources and Environment, Southwest University, Chongqing 400715, China

IJERPH, 2018, vol. 15, issue 12, 1-14

Abstract: Mercury (Hg) deposition in the forest ecosystem is a significant source of input for methyl Hg (MeHg) and total Hg (THg) to the subtropical forest field and downstream aquatic systems. Wet deposition, litterfall, runoff, and fluxes with forest soil percolate of MeHg and THg were sampled for two years in a watershed forest of southwest China. Results showed that the depositions of THg and MeHg through litterfall and throughfall were 86 µg m −2 yr −1 and 0.8 µg m −2 yr −1 respectively, with litterfall acting as a predominant route for the input of both THg and MeHg. The estimated fluxes of THg and MeHg in the throughfall and litterfall were 3 and 4 times greater than those in the precipitation. Methylmercury in the decomposed litter migrates during its erosion by surface runoff and the concentrations of MeHg were quite consistent with that in the surface runoff. Methylmercury mainly accumulated in the lower layer of the litter and upper layer of the soil ( O i ), and its transfer through the soil cross-section was delayed. THg retention was not consistent with MeHg, probably with lower soil layers ( O e and O a ) storing and enriching THg in the forest ecosystem. The forest floor of the lower soil is an effective sink for THg but not for MeHg. Methylmercury accumulated in decomposing litter and upper soil layer might transfer with soil percolate, possessing potential ecological risks for residents living around the downstream aquatic systems.

Keywords: THg; MeHg; watershed forest; deposition; transport (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2018
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