A ~150-year record of human impact in the Lake Wuliangsu (China) watershed: evidence from polycyclic aromatic hydrocarbon and organochlorine pesticide distributions in sediments

Human activities in and around Lake Wuliangsu, in the upper reaches of the Yellow River, triggered environmental changes for which evidence is preserved in the lake sediments. We investigated the past ~150 years of human impacts on Lake Wuliangsu using high-resolution records of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in the sediments. Prior to the 1950s, there were very low concentrations of contaminants in the lake deposits. In the 1950s, relatively higher OCP concentrations and proportions of low molecular weight (LMW) PAHs were related to the intensification of agricultural activity. Since the 1990s, increases in high molecular weight (HMW) PAH concentrations and their proportions, and decreases in OCP concentrations and proportions of LMW PAHs, indicated human impacts on the lake were dominated by industry and urban development. Thus, there have been three periods of human-mediated environmental change in the Lake Wuliangsu basin, inferred from the PAH and OCP records (pre-1950s, 1950s-1990s, and 1990s to present). The inferred changes are consistent with the local socioeconomic data. The agreement between paleolimnologic records from Lake Wuliangsu and socioeconomic data suggests that the lake sediments provide a reliable archive for investigating the environmental history of human impacts on the lake.