Occurrence, sources, bioaccumulation, and air–water exchange fluxes of polycyclic aromatic hydrocarbons in Lake Hongze, China

Compared with deep oligotrophic waters, the distribution and geochemical processes of polycyclic aromatic hydrocarbons (PAHs) in shallow eutrophic waters are more complicated. The fourth largest freshwater lake in China (Lake Hongze) was taken as an example to study distribution, sources, bioaccumulation, and air–water exchange of PAHs in shallow eutrophic waters. Eighty samples of surface sediments, air, water, and plankton were collected simultaneously from 15 sampling sites in November 2018. PAHs were extracted, concentrated, and analyzed using GC–MS. Average concentrations of ∑PAH16 in the surface sediments, atmosphere, water, phytoplankton, zooplankton, and suspended particle matter were 511 ± 212 ng g−1, 119 ng m−3, 232 ± 91.2 ng L−1, 12,500 ± 70,000 ng g−1, 102,000 ± 83,600 ng g−1, and 35,100 ± 24,700 ng g−1. Log BCF of PAHs in phytoplankton ranged from 6.7 ± 7.8 to 16.0 ± 4.4. Log BAF of PAHs in zooplankton ranged from 8.2 ± 8.1 to 16.8 ± 3.9. Log BMF of PAHs from phytoplankton to zooplankton varied from − 0.25 ± 0.39 to 0.25 ± 0.55. Combustion of petroleum and coal was the main source for the PAHs in the surface sediments of Lake Hongze. Concentrations of PAHs in phytoplankton and zooplankton were negatively correlated to the trophic level index. Bioaccumulation of PAHs by plankton was observed. No biomagnification occurred from phytoplankton to zooplankton for most PAHs during this sampling period. The net air–water flux of low molecular weight PAHs was from water to air. The net air–water flux of high molecular weight PAHs was from air to water.