Mercury Sources and Processes Implied by Other Pollutants Distributions in Surface Water and Sediments of a Subtropical Estuary in Southern China

Concentrations and isotopic compositions of mercury in surface water and surface sediment of the Jiulong River Estuary (JRE) were measured. Differences in total mercury (THg) concentrations in surface water between dry and wet seasons were insignificant, which was also the case with surface sediment THg levels. Large variations in Hg isotopic compositions were observed both in surface water (delta Hg-202: - 1.53 to 0.61 parts per thousand; Delta Hg-199: - 0.22 to 0.20 parts per thousand) and surface sediment (delta Hg-202: - 2.64 to - 0.96 parts per thousand; Delta Hg-199: - 0.27 to 0.25 parts per thousand). Concentration correlations between mercury and dissolved inorganic nitrogen (DIN) implied that mercury in surface sediment may undergo resuspension and be re-emitted to the water surface. The negative Delta Hg-199 in most of the surface sediments and the correlation between mercury and DIN in the wet season indicate that soil erosion is the major source of mercury. The main sources of mercury in surface water are precipitation and natural soil. The correlation between mercury and dissolved inorganic carbon, perfluoroalkyl substances, polycyclic aromatic hydrocarbons, and dissolved Cd indicates that the contribution of underground water and industrial and urban waste cannot be ignored, which is supported by the positive signature of Delta Hg-199. The results of the isotopic analysis also indicate that atmospheric dry deposition is another source of mercury in surface water. The study suggests that the mercury distribution in the estuary is related to some other pollutants. Both using mercury isotope signatures and the distribution links between mercury and other pollutants can be used to better understand the processes and sources of mercury in the estuary.

Automated summary

The concentrations and isotopic compositions of mercury in the Jiulong River Estuary were investigated. The study found that there were no significant differences in mercury concentrations between dry and wet seasons in both surface water and sediment. However, large variations in Hg isotopic compositions were observed. Soil erosion was identified as the major source of mercury in surface sediment, while precipitation and natural soil were the main sources in surface water. Additionally, underground water and industrial and urban waste also contributed to mercury pollution in surface water, and atmospheric dry deposition was another source.