Objective To analyze the spatial distribution characteristics and water quality risks of chlorite and chlorate in drinking water disinfected by chlorine dioxide in Chongqing, China, from 2019 to 2021, and to investigate the influencing factors for the distribution of chlorite and chlorate.

Methods The method of water quality risk index and spatial correlation analysis were performed for chlorine dioxide disinfection by-products to evaluate the spatial distribution characteristics and water quality risk of chlorite and chlorate in 12 135 drinking water samples in Chongqing.

Results Chlorite had a detection rate of 75.48% (9 159/12 135), an excess rate of 5.70%, a median of 0.14 mg/L, and a detection range of ND-13.9 mg/L, and chlorate had a detection rate of 75.07% (9 110/12 135), an excess rate of 6.39%, a median of 0.15 mg/L, and a detection range of ND-14.71 mg/L. High water quality risks of chlorite and chlorate were mainly observed in northern and western Chongqing, where water quality in 2021 was improved compare with that in 2019, while deterioration was observed in several districts and counties in the northeast and southeast of Chongqing. There was regional aggregation in the water quality risk index of chlorite and chlorate, and high-high accumulation areas were mainly distributed in western Chongqing.

Conclusion From 2019 to 2021, there is a generally good condition of chlorite and chlorate pollution in drinking water in Chongqing, but with a relatively high water quality risk index in some areas of northern and western Chongqing.