A 1900‐year record of mercury (Hg) from the east continental shelf of Hainan Island, South China Sea

Abstract

Natural archives are ideal tools for studying sedimentation history of mercury (Hg). However, record of Hg in marine sediments on millennial scales is less documented. This study analyzes a sedimentary core collected from the East Continental Shelf of Hainan Island, South China Sea. From 210Pb and radiocarbon (14C) chronological and geochemical analyses, a sequential record of Hg over the past 1900 years was reconstructed. Integrated analyses of Loss on Ignition (LOI), mean grain size, terrestrial elements aluminium (Al), rare earth element (∑REE) and Hg, allowed us to infer that Hg in the sediments received impacts from atmospheric deposition. Both concentrations and anthropogenic fluxes of Hg exhibit evident changes over the past 1900 years. Specifically, anthropogenic Hg flux in the last ~150 years is substantially high (mean 23.7 μg/m2/yr), which is approximately 11 times greater (in terms of enrichment factor) relative to background. Generally, Hg concentrations in the bulk sediments before 1850 AD can be explained by natural processes, whereas, by contrast, the rapid increase in flux of Hg since the mid‐19th century is related to deposition associated with anthropogenic release. The anthropogenic Hg flux shows a decrease by ~30 μg/m2/yr since 1980s, consistent with the decline in global Hg production. Nevertheless, the anthropogenic Hg flux in the present day remains 6.5 times higher than the baseline (pre‐1850 era).