Geochemical baseline establishment and pollution source determination of heavy metals in lake sediments: A case study in Lihu Lake, China

Abstract

Geochemical baseline, as the boundary between background and anomalous values of pollutants in sediments, is typically used to evaluate whether sediments are disturbed by human activities. However, this tool is rarely used in identifying the pollution source types of heavy metals. This study aims to determine the pollution source of heavy metals in sediments based on the geochemical baseline by using statistical methods. The geochemical baseline values of surface and core sediments in Lihu Lake, a typical urban lake in Taihu Lake Basin, were calculated by relative cumulative frequency and iterative methods. The enrichment degree and pollution source of heavy metals in surface sediments were also determined. The metal baselines in the core or surface sediments calculated by the two methods did not show significant difference (P > 0.05). The geochemical baseline of core sediments could represent the background level of sediments in the study area. The enrichment extent of the tested metals in surface sediments followed the order of: Pb > Zn > Hg > As > Cu > Cd > Ni > Cr. The average contents of Pb and Zn were 3.0 and 2.1 times of the background values, and their pollution were mainly derived from local and non-point sources, respectively. The contributions of the background concentrations to the contents of Cu, As, and Hg were slightly higher than that of human interference, and accounted for 59.4%, 58.4%, and 54.0% of the total contents, respectively. The pollutions of Cu and As mainly originated from non-point source, and that of Hg was mainly derived from local source. The contents of Cr, Ni, and Cd were within the background level. Geochemical baseline can be used not only to determine the enrichment degree but also as a potentially useful tool for identifying the pollution source (local and non-point source) of heavy metals in sediments.

Keywords: Background concentration; Local source; Non-point source; Pollution evaluation; Source identification; Taihu Lake.