ZHU Jinshan1,2, GAO Runxia3, WANG Yongmin1, LIAO Dunxiu2, WANG Longchang1, YIN Deliang1,4, WANG Dingyong1,4
(1. College of Resources and Environment, Southwest University, Chongqing 400715, China;
2. Chongqing Academy of Agricultural Sciences, Chongqing 401329, China;
3.Chongqing Institute of Geology and Mineral Resources, Chongqing 400042, China;
4.Chongqing Key Laboratory of Agricultural Resources and Environment, Chongqing 400716, China )
Abstract: The diffusion flux of mercury and methylmercury at water/sediment interface of the Three Gorges Reservoir was studied by simulation experiments in laboratory. Results show that MeHg/THg ratio in shallow sediment and deep-water sediment are 0.41±0.29% and 0.74±0.52% during flooding periods, respectively. Shallow reservoir sediment has higher methylation potential than that of deep-water reservoir sediment. With increasing flooding time, the content of methylmercury in sediments increases exponentially. The diffusion of inorganic mercury in sediments is best fitted by model of Freundlich. The relatively aerobic environment is more favorable for the release of inorganic mercury in sediments. Accordingly, the diffusion of methylmercury in sediments is best fitted by model of Parabolic. Dark and anaerobic environment is more conducive for the release of methylmercury in sediments. The diffusion flux of dissolved mercury and methylmercury are 154.65±47.12-160.23±56.19 ng/(m2•d) and 7.61±3.39 - 7.79±4.56 ng/(m2•d) at water/sediment interface in water-level-fluctuating zone of the Three Gorges Reservoir, respectively. With the increase of flooding time, the pore water of inorganic mercury and methylmercury fluxes to the overlying water increases first and then decreases. The contribution rate of methylmercury in pore water and overlying water are 1.5%-14.3% and 0.28-0.85kg/a, respectively. At the same time, the contribution rate and amount of mercury in pore water and overlying water are 0.20%-1.70% and 5.64-17.55 kg/a, respectively.
Key words: sediment/water interface; methylmercury; water-level-fluctuating zone; the Three Gorges Reservoir
EARTH AND ENVIRONMENT Vol.46, No.2, Tot No.322, 2018, Page 164-172
