Influence of global warming and human activity on mercury accumulation patterns in wetlands across the Qinghai-Tibet Plateau

Science China Press

 

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The typical wetland in the Qinghai-Tibet Plateau

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Credit: Courtesy of Xinbin Feng et al.

Known as the “roof of the world” and “water tower of Asia,” the Qinghai-Tibet Plateau is a key eco-safety barrier and a focus of China and the region to promote ecological sustainability. Wetlands in the Qinghai-Tibet Plateau are a unique and fragile ecosystem undergoing rapid changes (Figure 1). Global warming accelerates glacier melting and permafrost thawing, alters geomorphology and hydrology, and affects the transport and accumulation of contaminants in the wetlands. Mercury (Hg) is one of the most problematic pollutants of global concern. Wetlands are known to be a Hg-sensitive ecosystem in low altitude regions. However, the mercury cycle in wetlands of the Qinghai-Tibet Plateau remains poorly studied, specifically in a changing climate.

 “It was not easy to conduct a large scale of wetland sediment sampling in the Qinghai-Tibet Plateau due to the harsh environmental conditions”, says Dr. Xun Wang from Institute of Geochemistry, Chinese Academy of Sciences, one of group members of this study. The team collected 50 sediment cores across the Qinghai-Tibet Plateau from June to October in 2020, based on the river, lake and marsh distribution, and their sizes and traffic accessibility.

The team found two unique patterns of mercury accumulation in wetland sediments (Figure 2). One is the “Surface Peak” in monsoon-controlled regions, and the other is the “Subsurface Peak” in westerly-controlled regions. The former is attributed to the combined effects of increasing anthropogenic emissions and climate-induced changes in the cryosphere and wetland hydrology in the last 100−150 years. The climate changes in westerly-controlled regions in the last 50−70 years led to a mercury peak in the sediment subsurface.

“These results strongly show that human impacts and global changes have accelerated mercury accumulation in wetlands in the Qinghai-Tibet Plateau. There are lots of previously locked mercury in glacier and permafrost. The global warming accelerates the melting of glaciers and permafrost, and releases these “old” mercury sequestered in the ice and permafrost soil into wetlands. This poses a significant risk to the ecosystems in the Qinghai-Tibet Plateau” says, Dr. Xinbin Feng, from Institute of Geochemistry, Chinese Academy of Sciences, one of the leaders of this study.

Feng and Wang designed research, and Wang performed research. Dr. Wei Yuan and Meng Lu contributed sampling and measurements. There were three Ph.D. students (Longyu Jia, Nantao Liu and Fei Wu) and one master student (Xinyuan Cai) involving in measurements. Dr. Feiyue Wang and Che-Jen Lin helped to analyze the data and revised the manuscript.

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See the article:

Influence of global warming and human activity on mercury accumulation patterns in wetlands across the Qinghai-Tibet Plateau

https://doi.org/10.1093/nsr/nwae414

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Journal

National Science Review

DOI

10.1093/nsr/nwae414