Mercury and methylmercury in China's lake sediments and first estimation of mercury burial fluxes

Chenghao Yu; Yunping Xu; Yunyun Yan; Wenjie Xiao; Maodian Liu; Menghan Cheng; Wei He; Fuliu Xu; Xuejun Wang

doi:10.1016/j.scitotenv.2021.145338

Mercury and methylmercury in China's lake sediments and first estimation of mercury burial fluxes

Sci Total Environ. 2021 May 20:770:145338. doi: 10.1016/j.scitotenv.2021.145338. Epub 2021 Jan 23.

Authors

Chenghao Yu¹, Yunping Xu², Yunyun Yan¹, Wenjie Xiao³, Maodian Liu⁴, Menghan Cheng¹, Wei He¹, Fuliu Xu¹, Xuejun Wang⁵

Affiliations

¹ Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China.
² College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China.
³ College of Marine Sciences, Shanghai Ocean University, Shanghai 201306, China; Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China; Shenzhen Key Laboratory of Marine Archaea Geo-Omics, Shenzhen 518055, China.
⁴ Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China; School of the Environment, Yale University, New Haven, CT 06511, USA.
⁵ Ministry of Education Key Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China. Electronic address: xjwang@urban.pku.edu.cn.

PMID: 33517014
DOI: 10.1016/j.scitotenv.2021.145338

Abstract

Lake sediments are key materials for mercury deposition and methylation. To understand the mercury concentrations in China's lakes, 100 lake surface sediment samples were collected from 35 lakes in 2014. Total mercury (THg), methylmercury (MeHg) concentrations and the annual Hg burial rates in lake sediments were measured. THg and MeHg concentrations in the sediment ranged from 13.6 to 1488 ng‧g^-1 and 0.05 to 1.70 ng‧g^-1, respectively, and urban lakes reported most high values, indicating direct anthropogenic inputs. The Inner Mongolia-Xinjiang Region (MX) and Qinghai-Tibet Plateau Region (QT) reported relatively lower mercury burial rates, while the Eastern Plain Region (EP), Northeast Mountain and Plain Region (NE), and Yunnan-Guizhou Plateau Region (YG) reported higher mercury burial rates. Regional variances of THg burial fluxes were dominated by atmospheric deposition, terrestrial input, and sediment accumulation rates in different lakes. In 2014, the estimated average THg burial rate in China's lakes was 139 μg‧m^-2‧yr^-1, comparable to the average in mid-latitude North America in recent years; however, due to China's much smaller lake area relative to NA, the annual THg burial flux in China was much lower than that in North America. EP and NE, where most freshwater aquatic products in China are harvested, accounted for 58.2% and 22.9%, respectively, of the THg burial flux. High sedimentary MeHg concentrations and MeHg:THg ratios were reported in most of the NE but low MeHg concentrations and MeHg:THg ratios were reported in EP. MeHg concentrations and MeHg:THg ratios were positively correlated with water COD levels and negatively correlated with average temperature. The results of this study indicate that in addition to the adjacent seas, lake sediments are an important mercury sink in China's aquatic environment, which could cause health risks due to MeHg intake, especially in NE.

Keywords: Aquatic environment; Deposition; Inventory; Net methylation potential; Sedimentation.