Occurrence, Source Appointment And Ecological Risk Evaluation In Chaohu Lake

Chaohu lake, which is located in central Anhui Province, is one of five fresh water lakes in China. The lake plays an important part not only in intensive commercial fishing, but also for water supply, irrigation navigation, tourism, and recreation as well as being of great conservation value in its wildlife and wetland system, as a result, the watershed was rich in rice and fish. However, the lake has suffered serious pollution from the urban areas since 1980’s, the aquatic environment was deteriorated gradually, and the blue green algae outbreaks have threatened to the local water quality. Consequently, the contamination of the lake are gaining wild public concerns.Increasing attention has been paid to polycyclic aromatic hydrocarbons (PAHs) in the water environmental on a watershed scale because they are recognized to be persistent in the environment, and to be carcinogenic, teratogenetic and mutagenic. In the present study, PAHs in sediment (both surface and core) and surface water samples collected around Chaohu lake were determined to understand their sources, input history and ecological effect to the local aquatic ecosystem. The concentration of PAHs in sediment ranged from 140-70500 ng/g, at the medium level in the sediment-bound PAHs concentration range around both China and world. The maximum concentration of PAHs was obtained in Nanfei River area, up to 804000 ng/g. The concentration of PAHs of surface sediment in the lake shows a significantly spatial distribution with high concentrations in western lake area and low values in eastern area. PAHs were considered to be originated from different sources depending on the spatial location. In total, the sediment-bound PAHs in Chaohu Lake were most from mixture sources, and they are considered from industrial pollution in Nanfei River area. The mean TU values was 1.7 in the surface sediment samples collected from Nanfei River, and the average value of 1.3 was obtained in the core sediments at estuary of Nanfei River. While the TU value was less than 1.0 for other sediment samples. These results imply high ecological risks by PAHs contamination to the Nanfei River and its estuary, the effect from PAHs residue in other areas on the benthic organisms would be ignored.The concentration of PAHs in water samples around Chaohu Lake did not show significant spatial distribution, with a range of 130-4940 ng/1. Low molecular weight PAHs were predominant, suggesting that PAHs were from mixture sources combing pyrogenic processing of organic matter and petroleum discharge. The ecological risk by PAHs in water was evaluated based on the species sensitivity distribution and results show PAHs in water presented potential risk to aquatic biotic community. The results of HCs and MOS10 confirm the conclusion.