Sedimentary regularity and ecological risk of heavy metals in Chaohu Lake sediments

One of the most commonly used methods to assess the ecological risk of heavy metals in lake sediments is referring to the background values of soil. However, the background values currently used are the statistical average of the elemental contents in a given region with a large range of areas, which are not relevant for lake sediments with spatially differentiated characteristics. So far, there are few studies focusing on the diagnosis and analysis of background values of heavy metals considering lake sedimentary history. To fill the gap, this study investigated the variation in heavy metals in undisturbed core sediments across the western, central and eastern regions of Chaohu Lake. The background values of heavy metals were then deduced based on the distribution of heavy metals in sediments. The background values were used to inform the ecological evaluation methods based on weight, including the geological accumulation index (I _geo ), and the improved potential ecological risk index (RI) based on chemical accumulation and toxicity unit (∑TU). A probabilistic risk assessment was conducted based on the improved RI using a large number of monitoring data. The results indicated that the improved RI based on chemical sorting identified a lower risk of 67.0% and a moderate risk of 33.0%, with Hg, As and Ni being the major contributors. The comparative analysis indicated that the probabilistic statistical method based on the improved RI can provide a more objective and scientific basis for the management of lake heavy metals pollution.