Isotopic tracing of mercury sources in estuarine-inner shelf sediments of the East China Sea

Xiang Sun; Runsheng Yin; Limin Hu; Zhigang Guo; James P Hurley; Ryan F Lepak; Xiangdong Li

doi:10.1016/j.envpol.2020.114356

Isotopic tracing of mercury sources in estuarine-inner shelf sediments of the East China Sea

Environ Pollut. 2020 Jul:262:114356. doi: 10.1016/j.envpol.2020.114356. Epub 2020 Mar 12.

Authors

Xiang Sun¹, Runsheng Yin², Limin Hu³, Zhigang Guo⁴, James P Hurley⁵, Ryan F Lepak⁶, Xiangdong Li⁷

Affiliations

¹ Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China.
² State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
³ Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China; Key Laboratory of Marine Sedimentology and Environmental Geology, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China.
⁴ Department of Environmental Science and Engineering, Fudan University, Shanghai 200438, China; Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China. Electronic address: guozgg@fudan.edu.cn.
⁵ Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI, 53706, USA; Department of Civil and Environmental Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
⁶ Environmental Chemistry and Technology Program, University of Wisconsin-Madison, Madison, WI, 53706, USA.
⁷ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.

PMID: 32443195
DOI: 10.1016/j.envpol.2020.114356

Abstract

Large river estuarine-inner shelf systems play an important role in the coastal biogeochemical cycling of heavy metals; however, the source-to-sink of mercury (Hg) in these environments remain poorly understood. In this study, the Hg isotopic composition of surface sediments in the Yangtze River Estuary (YRE) and inner shelf of the East China Sea (ECS) were examined to quantitatively track Hg sources in this region. We detected large spatial variation in δ²⁰²Hg (-1.88 to -0.29‰) and Δ¹⁹⁹Hg (-0.22 to 0.13‰) in sediments of the YRE-ECS inner shelf. The impact of sediment resuspension and transport from the YRE to the inner shelf of the ECS could have little effect on Hg isotopic composition, and the two regions shared similar Hg isotopic composition. An isotope-based triple mixing model further revealed major contributors to sediment Hg from industrial Hg discharge into water (51.8 ± 24.5%), soil Hg from surface runoff (29.2 ± 17.0%), and precipitation-derived atmospheric deposition Hg (19.1 ± 17.5%). The Hg isotopic compositions of the YRE sediments and other local river estuaries were similar to those of direct industrial Hg discharge, indicating that contaminated riverine discharge was the dominant Hg source for estuarine and adjacent shelf areas. Soil Hg delivered through surface runoff was the primary source of Hg to the coastal areas not near large river estuaries, whereas precipitation-derived atmospheric deposition had a greater influence on offshore sediment Hg content. Industrial Hg discharged to rivers had the highest mean depositional flux (35.0 ± 27.3 ng cm^-2 yr^-1) and mass inventory (25.6 t yr^-1), accounting for 77.4% of the total Hg variance. The findings of this study demonstrate that large rivers such as the Yangtze River can supply substantial amounts of industrial Hg to the estuary and adjacent shelf.

Keywords: Burial flux; Estuarine-inner shelf system; Isotopic tracing; Mercury; Quantitative source apportionment.

MeSH terms

China
Environmental Monitoring
Estuaries
Geologic Sediments
Mercury*
Rivers
Water Pollutants, Chemical / analysis*

Substances

Water Pollutants, Chemical
Mercury