Spatial distribution and ecological risks of neonicotinoid insecticides for an urban tidal stream of Guangzhou City, South China

Neonicotinoid insecticides (NEOs) are widely used in many urban regions. Studies on NEOs residues in urban tidal streams and the associated ecological risks are limited. In this study, the occurrence, spatiotemporal distribution, and ecological risks of seven selected NEOs in the Wuchong Stream in Guangzhou, China were investigated. Moreover, the correlation between typical urban factors and the ecological risk of NEOs was discussed. In the Wuchong Stream, the concentrations of NEOs in the water samples ranged from 0.97 to 175.92 ng. L-1 in the dry season and 3.15 to 312.92 ng. L-1 in the wet season.The most commonly used neonicotionoids were acetamiprid and imidacloprid in the Wuchong Sream basin. The concentrations of NEOs in the midstream were higher than that in the downstream and upstream. The results of the ecological risk indicated that NEOs were likely to biologically impair the urban stream ecosystem, especially in the dry season. For three typical aquatic organisms, the current concentrations of NEOs posed a significant threat to aquatic insects. Compared to other urban factors, residentidal district and farmland area were the main socioeconomic factors affecting the ecological risk of NEOs in the Wuchong Stream basin. Therefore, the correct and reasonable application of NEOs and continuous improvement of the applicant methods can reduce the environmental risks of urban streams.