Occurrence and distribution of five neonicotinoids (NEOs) in surface water and sediment were studied in the Pearl Rivers, including three trunk streams, Dongjiang, Beijiang, Xijiang River (DR, BR and XR), South China. At least one neonicotinoid was detected in surface water and sediment of the Pearl Rivers, with imidacloprid (IMI) and thiamethoxam (THM) being the frequently detected NEOs. Total amount of NEOs (∑5neonics) in surface water and sediment ranged from 24.0 to 322 ng/L, and from 0.11 to 11.6 ng/g dw, respectively. Moreover, the order of contamination level of NEOs in the Pearl Rivers was as follows: XR > DR > BR for surface water, and BR > DR > XR for sediment. Local agricultural activities and effluents of wastewater treatment plants (WWTPs) could be major sources of NEOs in the Pearl Rivers. Solubilization and dilution of NEOs between surface water and sediment during different seasons (spring and summer) could be attributed to rainfall intensities or climate of the Pearl River Delta. An ecological risk assessment of the exposure to current environmental concentration of imidacloprid and ∑5NEOs suggests a threat to sensitive non-target invertebrates, including aquatic invertebrates.
Source: Zhang C et al (2019). Chemosphere 217: 437-446