Mercury distribution, exposure and risk in Poyang Lake and vicinity, China

Mercury (Hg), especially methylmercury (MeHg), which is highly neurotoxic, is a global pollutant that can affect human health because of its accumulation in aquatic products. Poyang Lake, an inland lake in China, has been significantly affected by human activity, yet there is limited understanding of local mercury contamination and potential exposure pathways to humans. In this study, we explored the risks of mercury exposure by sampling sediments, plants, and aquatic organisms in the lake and surrounding areas and analyzing total Hg (THg) and MeHg levels. Sediment sampling was conducted at the main lake, rivers, rice paddies, and fishponds. Two dominant species of plants and 15 species of aquatic organisms were sampled and analyzed. We assessed the characteristics of mercury in sediments using the geo-accumulation index (I_geo), mercury exposure using the biomagnification factor (BMF) and biota sediment accumulation factor (BSAF), and risks using thresholds for adverse effects. The highest THg concentrations (137.04 ± 44.3 ng g^-1 dw) were detected in the main lake sediments, whereas the highest MeHg concentrations (0.47 ± 0.6 ng g^-1 dw) were detected in fishpond sediments. Mercury accumulation in the main lake sediments could be assessed as contaminated (I_geo > 0: 81.6%). Yellow catfish had the highest mercury concentration (THg 770.69 ± 199.7 ng g^-1 dw; MeHg 741.93 ± 168.8 ng g^-1 dw). Piscivores were adversely affected by carnivorous fish (50.8%), but all fish concentrations did not exceed the food safety standards recommend by China and the WHO. The mercury exposure results revealed significant Hg biomagnification and enrichment (BMF >1: 94.55%; BSAF_max = 1218). Long-term monitoring of aquatic organisms is warranted.