Seasonal variation of pesticides and associated risks in Guangdong's drinking water sources

Pesticides are essential for crop protection and agricultural yield enhancement. However, their entry into water bodies, particularly drinking water sources, poses threats to human health and aquatic ecosystems. The seasonal variation, and potential risks of pesticides in drinking water sources in Guangdong, China were investigated. The total pesticide concentrations were significantly elevated during the dry season compared to the wet season (p < 0.01; |r| = 0.77; 95 % CI for difference in medians: [92.6, 315] ng/L). Neonicotinoid pesticides predominated in more than half of the samples. Across both seasons, river water sources displayed significantly higher total pesticide concentrations than reservoir sources (dry season: p < 0.05, |r| =0.60, 95 % CI [106,359] ng/L; wet season: p < 0.01, |r| =0.66, 95 % CI [70.3, 412] ng/L). Health risk assessments indicated that pesticides in drinking water sources pose non-carcinogenic and carcinogenic risks associated with long-term direct consumption, particularly for children aged 3–4 years. Ecological risk assessments revealed high potential risks to aquatic organisms (summed risk quotient > 1), particularly from neonicotinoid pesticides. These findings highlight the necessity of seasonally adaptive controls for pesticides and water quality to reduce risks to public health and ecosystems.