The spatiotemporal distribution, partitioning, and prioritization of current use pesticides (CUPs) in aquatic environment of Pearl River Delta.

Current use pesticides (CUPs) are widely applied in Pearl River Delta (PRD), one of the most developed agricultural regions in China. The characteristic of CUPs contamination in aquatic environment in PRD remains fragmentary, in particular to the prioritization of CUPs. This study investigated the spatiotemporal distribution, partitioning, and prioritization of four CUPs categories, including 15 neonicotinoids and metabolites, 12 insecticides, 11 herbicides, and 3 fungicides, in aquatic environment of PRD. The results showed that 19 and 8 out of 41 target CUPs were detected in more than 50 % water samples and sediment samples, respectively. Herbicides was the predominant category in both water and sediment, with the mean percentages being 64.7 % and 67.2 % in wet season and 55.2 % and 66.6 % in dry season. The total CUP concentrations were in the range of 2.5-286 ng/L and 2.0-1272 ng/L in water and 0.37-61 ng/g and 0.069-128 ng/g in sediment in wet and dry seasons, respectively. The total CUP concentration in water displayed spatial difference, with highest concentration observing in west river (WR) while the corresponding concentration in sediment were indistinguishable among east river (ER), pearl river (PR), north river (NR), and WR. The sediment-water partitioning coefficients (Kd or Koc) of 12 selected CUPs were significantly and positively correlated with their octanol-water coefficient (Kow). A risk-based prioritization approach was developed to rank the identified CUPs. Metolachlor, atrazine, ametryn, diuron, thiamethoxam, and dicamba were firstly identified with high-risk priority in water samples of PRD in this study, indicating that the potential ecological risks of herbicides were higher than other CUPs. This study provides newly insights into the prioritization of CUPs for remediation and management in PRD.