Aquaculture Exacerbates the Accumulation and Ecological Risk of Heavy Metal from Anthropogenic and Natural Sources, a Case Study in Hung-tse Lake, China

Heavy metal pollution in water environment has aroused wide concern, but the seasonal variation of heavy metal pollution in aquaculture environment has not been reported in detail, and the resulting environmental risk change has not received enough attention. This study investigated the seasonal variation of water quality parameters, heavy metal pollution in surface water and sediment, as well as the ecological risk change in crab ponds in Hung-tse Lake, China. The results indicated that nitrogen, phosphorus, etc. in surface water were obviously increased during the growing period of crab. The concentrations of Cr, Cu, Zn, As, Cd, and Pb in surface water ranged from 0.01 to 62.53 μg/L, without significant difference compared with that in watercourse. However, aquaculture significantly exacerbated the accumulation of Cr, Cu, Zn, Cd, and Pb in sediment with a concentration range of 0.16–130.66 mg/kg ( p < 0.05). Multivariate statistical analysis showed that aquaculture not only resulted in the excessive accumulation of Cu, Zn, Cd, and Pb from anthropogenic source but also Cr and As from natural or semi-natural source. Geoaccumulation index was in the range of − 1.80–1.78, indicating that heavy metal pollution by crab aquaculture reached moderate level. Risk index ranged from 116.01 to 159.79 showing a gradually increasing moderate ecological risk during the growth period of aquatic products.