Distribution, fate and risk assessment of PAHs in water and sediments from an aquaculture- and shipping-impacted subtropical lake, China.

The spatial-temporal distribution of polycyclic aromatic hydrocarbons (PAHs), their source, and potential health risks were determined in overlying water and surface sediments from Chinese Lake Guchenghu, adjacent commercial mitten crab ponds and the connected Wushen Canal to assess the contamination profile of the area. The total PAHs concentrations in sediment and water were 86.7-1790 ng g dry weight (dw) and 184-365 ng L in summer and 184-3140 ng g dw and 410-1160 ng L in winter. Two- and 3-ring PAHs were the predominant compounds in water, while PAHs with 4-6 rings dominated in the sediment at both upstream and downstream sites. PAHs concentrations in water and sediment correlated significantly. Diagnostic ratios and positive matrix factorization (PMF) analyses indicated a strong influence of pyrogenic sources, principally biomass combustion and vehicle emission, on the concentrations of PAHs. The distribution, source identification, and mean effects range median quotients (mERMQ) analyses suggested that the most contaminated area was located downstream and upstream of the Wushen Canal, followed by Lake Guchenghu and a commercial crab pond area. From an ecological point of view, PAHs posed a potential risk to drinking water sources as the concentrations exceeded the guideline value of 0.05 μg L. The risk posed by sediment PAHs appeared to be low except for the downstream sites, which showed a low to medium ecotoxicological risk. The total incremental lifetime cancer risks ranged between 10 and 10, indicating a potential health risk for the local population when exposed to sediment from the area.