Heavy metal concentrations in sediments from Xingyun lake, southwestern China: implications for environmental changes and human activities

Environmental changes influenced by human activities were recorded in the sediment cores from Xingyun lake. Based on the Cs-137 and Pb-210 dating, multi-proxy records, enrichment factor (EF), and geoaccumulation index (I-geo) methods, the history of human-environment interactions in Xingyun lake catchment during the past 140years was studied. The results showed that the total heavy metal pollution in Xingyun lake followed the decreasing order: the northwestern>the middle>the southwestern>the southern>the north easterly. These distributions were controlled by regional geochemical background values, pollution load, and the lake current driven by prevailing southwesterly winds. The total EF value of heavy metals followed the decreasing order: EF (Zn)>EF (Cr)>EF (Pb)>EF (Cd)>EF (Cu). The total I-geo value of heavy metals also followed the decreasing order: I-geo (Zn)>I-geo (Cr)>I-geo (Pb)>I-geo (Cd)>I-geo (Cu). Consequently, the total pollution level of heavy metals followed the decreasing order: Zn>Cr>Pb>Cd>Cu. Before 1910AD, the natural erosion caused by climate changes was the key factor for the heavy metals accumulated. After 1910AD, the heavy metal concentrations were mainly controlled by anthropogenic impacts, the dominant sources were from industrial pollution, agricultural pollution, mining, and organic degradation. Finally, the sedimentary evolution history of Xingyun lake can be divided into four stages, i.e., (1) natural evolution stage during 1862-1910AD, (2) anthropogenic disturbance stage during 1910-1953AD, (3) anthropogenic reconstruction stage during 1953-1984AD, and (4) eutrophication stage after 1984AD.