Impact of agricultural activities on the occurrence of N -nitrosamines in an aquatic environment.

N -Nitrosamines, nitroso compounds with strong carcinogenic effects on humans, have been frequently detected in natural waters. In agricultural areas, there is typically a lack of drinking water treatment processes and distribution systems. As a result, residents often consume groundwater as drinking water which may contain N -nitrosamines, necessitating the investigation of the occurrence, sources, and carcinogenic risk of N -nitrosamines within the groundwater of agricultural areas. This study identified eight N -nitrosamines in groundwater and river water in the Jianghan Plain, a famous agricultural region in central China. N -Nitrosodimethylamine (NDMA), N -nitrosodiethylamine (NDEA), N -nitrosomorpholine (NMOR), N -nitrosopyrrolidine (NPYR), and N -nitrosodi- n -butylamine (NDBA) were detected in groundwater, with NDMA being the main compound detected (up to 52 ng L -1 ). Comparable concentrations of these N -nitrosamines were also found in river water. From laboratory experiments, we found a tremendous potential for the formation of N -nitrosamines in groundwater. Principal component analysis and multiple linear regression analysis results showed that the primary sources of N -nitrosamines in groundwater were the uses of nitrogen fertilizers and pesticides carrying specific N -nitrosamines such as NPYR. The average total carcinogenic risk values of detected N -nitrosamines were higher than the acceptable risk level (10 -5 ), suggesting a potential carcinogenic risk of groundwater. Further research is urgently needed to minimize N -nitrosamine levels in the groundwater of agricultural areas, particularly in those where pesticides and fertilizers are heavily used.