Ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the water from a large Chinese lake based on multiple indicators

In the surface water of Lake Chaohu, China, the concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were measured by gas chromatograph–mass spectrometer (GC–MS). Based on the species sensitivity distribution (SSD) model and the probabilistic risk assessment (PRA) model, the indicators were calculated to assess the potential ecological risk of the individual and of multiple congeners of PAHs and their probabilities. The results revealed that the average residual level of the total PAHs (PAH₁₆) in the water ranged from 95.2 to 370.1 ng/L, with a mean value 181.5 ± 70.8 ng/L. The PAH content in the water was dominated by the low-molecular-weight congeners. The multi-substance potentially affected fractions (msPAFs) of the studied PAHs obtained by the SSD model varied from 0.29% (site B3) to 1.58% (site B6), with an average of 0.51 ± 0.34%. The average of the msPAFs (0.93%) for the inflow rivers was greater than that for the western (0.42%) and eastern (0.34%) parts of the lake. The greatest ecological risk probability calculated by the PRA model was found for Pyr (1.55%), followed by Ant (7.07 × 10⁻²%), Fla (2.21 × 10⁻²%), Phe (9.25 × 10⁻⁶%), Nap (1.01 × 10⁻⁵%), Flo (1.16 × 10⁻¹⁴%) and Ace (2.86 × 10⁻¹⁶%). The same order of ecological risks calculated by the two models was found for the studied PAH compounds. The toxicity data might be the primary source of the ecological risk uncertainties, as indicated by the greater values of coefficients of variation (CV) for the toxicity. This study concluded that the combinations of multiple indicators based on the SSD and PRA models for the ecological risk assessment are necessary to provide more general information on the spatial variations and the probabilities of potential ecological risks of the individual and multiple congeners of PAHs.