Modern lake sedimentary record of PAHs and OCPs in a typical karst wetland, south China: Response to human activities and environmental changes.

The sedimentary history of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) over the past 140 years in a lake sediment core from Huixian karst wetland was reconstructed. The total PAHs and OCPs concentrations ranged from 40.0 to 210 ng g and 0.98 to 31.4 ng g, respectively. The vertical distribution of PAHs and OCPs in different stages was great consistent with the history of regional socio-economic development and the usage of OCPs. As the indicators of socio-economic development, gross domestic product (GDP), population, energy consumption, highway mileage, and private vehicles correlated with the PAHs concentrations, indicating the impact of human activities on PAHs levels. The PAHs and OCPs concentrations were also affected by environmental changes in the wetland, as reconstructed by total organic carbon (TOC), sand, silt, clay, quartz, and calcite in sediments. Redundancy analysis (RDA) results showed TOC was the dominant factor to explain the concentrations of PAHs and OCPs with the explanation of 86.7% and 43.5%, respectively. In addition, TOC content had significantly positive correlation with PAHs (0.96, p < 0.01) and OCPs (0.78, p < 0.01). In particular, the significantly positive correlation (p < 0.05) between calcite and PAHs and OCPs inferred that karstification might play an important role in the migration of PAHs and OCPs in the karst area. Therefore, the lake in Huixian wetland tended to be a sink more than a source of PAHs and OCPs influenced by the increasing TOC content and karstification under climate warming.