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Suspended sediment (SPS) plays an important role in the aquatic ecosystems. Selective serotonin uptake inhibitors (SSRIs) are commonly used antidepressants and are frequently detected in aquatic environments. However, the biological effects of SSRIs in the presence of SPS are not well understood. To fill this gap, an SPS-water system was constructed to investigate the effects of citalopram (CIT) on Daphnia magna in the presence of SPS with different concentrations (0.1, 0.5, 1 g l) and organic carbon contents (0.5, 1, 1.5, 2%). A dialysis bag was applied in the exposure system to control the same dissolved concentration of CIT and prevent SPS from entering into the bag. The dissolved CIT concentration obviously decreased in the SPS-water system during the exposure period. The presence of SPS significantly increased the immobilization of D. magna, and the immobilization rates were positively correlated with the SPS concentration and negatively correlated with the organic carbon content in SPS. For a single exposure, CIT significantly increased superoxide dismutase (SOD) activity and inhibited acetylcholinesterase (AChE) activity in D. magna, while SPS itself did not change the SOD and AChE activities. In the SPS-water system, SOD activity was significantly suppressed, indicating that the SPS-CIT combination could result in oxidative damage. However, SPS did not enhance the neurotoxicity of D. magna that was induced by CIT. These results suggest that SPS exerts a vital role on the biological effects of CIT and the contaminants sorbed on SPS should be taken into consideration.

Organic UV filters (OUV-Fs) are increasingly used for protection against UV irradiation. The widespread occurrence of OUV-Fs residues in aquatic systems has been reported, but little is known regarding their distribution and potential impact to the surface water in China. This study reports the occurrence, distribution and risk assessment of eight widely used OUV-Fs in the surface water of Nanjing. The results indicated butyl-methoxydibenzoylmethane, octyl-dimethyl-PABA and benzophenone-types (BP3, BP4 and BP1) were the most frequently detected compounds at concentrations of 3.63-104 ng/L. In general, the concentrations of OUV-Fs were decreased along the rivers; however, due to a substantial pollution load from the tributaries, higher concentrations of OUV-Fs were observed near the tributary inlet, compared to the other study areas. The risk assessment based on the calculated risk quotients (RQs) demonstrated that all OUV-Fs posed at least low risks to certain sensitive aquatic organisms, and BP3 posed high risk with RQ values of 1.64. It should be noted that the exclusion of adsorbed OUV-Fs might have contributed to an underestimation of the risk, therefore, it's necessary to assess both adsorbed and dissolved OUV-Fs in further studies.