Tracking the multiple Hg sources in sediments in a typical river-lake basin by isotope compositions and mixing models

In this study, total mercury (THg) contents and Hg isotope compositions in sediments were investigated in the Lianxi River, Zijiang River and South Dongting Lake to identify and quantify multiple Hg sources and evaluate the Hg environmental processes. The THg contents, delta Hg-202 and Delta Hg-199 values in sediments were 48.22 similar to 4284.32 mu g/kg, 1.33 similar to 0.04 parts per thousand and 0.25 similar to 0.03 parts per thousand, respectively. Relatively distinct Hg isotope characteristics of sediments were presented in the Lianxi River, Zijiang River and South Dongting Lake, indicating the dominant Hg sources considerably varied in these regions. Source apportionment based on MixSIAR proved that Hg in sediments mainly originated from industrial activities, and the ternary mixing model concluded non-ferrous metal smelting was the dominant industrial Hg contributor in the Lianxi River. Compared with the Lianxi River, the relative contribution of Hg in sediments from industrial activities significantly decreased, while the relative contributions of Hg from background releases significantly increased in the Zijiang River and South

Automated summary

In this study, the total mercury (THg) content and mercury isotope composition in sediments in the Lianxi River, Zijiang River, and South Dongting Lake were investigated to identify and quantify multiple mercury sources and evaluate mercury environmental processes. The results showed that the THg content, delta Hg-202, and Delta Hg-199 values in the sediments varied from 48.22 to 4284.32 μg/kg, 1.33 to 0.04‰, and 0.25 to 0.03‰, respectively. The sediments from the Lianxi River, Zijiang River, and South Dongting Lake exhibited distinct mercury isotope characteristics, indicating significant variations in dominant mercury sources in these regions. Source apportionment based on MixSIAR revealed that mercury in sediments mainly originated from industrial activities, with non-ferrous metal smelting being the dominant industrial mercury contributor in the Lianxi River. Compared to the Lianxi River, the relative contribution of mercury from industrial activities significantly decreased, while the relative contributions of mercury from background releases significantly increased in the Zijiang River and South Dongting Lake.