Occurrence, source, and partition of PAHs, PCBs, and OCPs in the multiphase system of an urban lake, Shanghai

Dianshan Lake (DSL)as an important water source protection area in Shanghai is facing serious water quality deterioration. A detailed investigation of persistent organic pollutants (POPs)including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs)in the multiphase system of DSL is very important for understanding their occurrence, sources, partition, and health risks. Total 11 sampling sites were selected including 3 inflowing rivers, 6 lake body sites, and 2 outflowing rivers. Total OCPs (Σ₂₀OCPs)showed the highest concentration in water dissolved phase with a range of 47.8–143 ng/L. Total PAHs (Σ₁₆PAHs)were the dominant compounds for suspended particle matter (SPM)and sediment phase, with a range of 2805–4130 and 206–4262 ng/g, respectively. The nonparametric test revealed the significantly higher concentrations of Σ₁₆PAHs in sediment, Σ₁₈PCBs in SPM, and Σ₂₀OCPs in dissolved water from inflowing rivers than lake body (p < 0.05), indicating the strong effect of riverine pollution input. The different seasonal distribution between Σ₁₆PAHs with Σ₁₈PCBs/Σ₂₀OCPs in SPM phase of lake body was closely attributed to their source disparities and the changes of rainfall and hydrodynamic conditions. Homologue compositions and isomer ratios analysis showed in DSL watershed PAHs were mainly derived from pyrogenic sources, PCBs from the leakage of capacitor equipment, sewage drainage of industries, and exfoliation of ship paints, and DDT from historical and recent application. The bioaccumulations of POPs in six fish species (n = 20)of DSL had high detection frequencies and a descending concentration order: Σ₁₆PAHs (353 ± 106 ng/g)> Σ₂₀OCPs (67.4 ± 27.0 ng/g)> Σ₁₈PCBs (32.0 ± 13.7 ng/g), with obvious species-specific characteristics. The partitioning behaviors of PAH congeners in the water-SPM-sediment-fish system of DSL were greatly influenced by logK_ow values. However, the feeding habits (e.g., sediment-feeding behavior)of fish species played a predominant role in the bioaccumulation of PCB and OCP congeners compared to two-phase partition. Health risk assessments of POPs in dissolved water and fish samples revealed that only Σ₁₆PAHs in dissolved phase have potential carcinogenic risk.