Spatiotemporal distributions of Cu, Zn, metribuzin, atrazine, and their transformation products in the surface water of a small plain stream in eastern China

The intensive use of fertilizers and pesticides in agriculture has led to widespread nonpoint source pollution in surface waterbodies. In this work, the occurrence and distribution of nonpoint source metals (Cu and Zn) and herbicides (metribuzin; atrazine; and its degradates, including desethyl atrazine (DEA), desisoproylatrazine (DIA), and deethyldeisopropylatrazine (DEDIA)) in the surface water of the Baima River, which is located in a region noted for its intense agricultural activities, were investigated during a high water period in August and a low water period in October. The results showed that the heavy metals and herbicides investigated were detected frequently in the surface water of the river during the two periods. The average concentrations of Cu during the high water period and low water period were 9.3 (0-20.7) and 8.7 (0-15.55)g/L, and the average concentrations of Zn during the two periods were 11.4 (6.65-22.15) and 10.6 (7.55-15.15)g/L, respectively. The concentrations of atrazine were higher than those of metribuzin, which ranged from 0.07 to 1.12g/L during the high water period and 0.01-0.74g/L during the low water period. The total concentrations of atrazine and its transformation products in 60.00% of the samples during the high water period exceeded the maximum contaminant level (MCL) of 3g/L for the drinking water criteria in the USA, and 33.33% of the samples exceeded the MCL during the low water period. The spatial and temporal distributions of nonpoint source pollutants along the Baima River were influenced by land use and hydrogeomorphic settings. The ecotoxicological risk assessment indicated that atrazine and DIA have moderate risks to aquatic environment in Baima River.