Anion-Mediated Pathways in Organophosphate Degradation in the Oconee River Watershed in Georgia

Abstract

The degradation of organophosphate pesticides in aquatic ecosystems is influenced by various environmental factors. This study investigates the influence of nitrate, sulfate, and phosphate on the degradation of malathion, a commonly used organophosphate pesticide, in the North Oconee River watershed in Georgia. Microcosm experiments were conducted to simulate environmental conditions and assess both microbial (biochemical) and non-microbial (chemical) degradation pathways. Nitrate and sulfate were found to significantly enhance malathion degradation through microbial-mediated oxidative and hydrolytic pathways. In contrast, phosphate, particularly at higher concentrations, inhibited microbial degradation by providing alternative nutrient sources. The presence of mercury chloride, which suppressed microbial activity, resulted in slower degradation rates across all conditions, underscoring the pivotal role of microbial communities in pesticide transformation. Non-targeted analyses identified key degradation products, including malaoxon, succinic acid, and diethyl succinate, primarily under nitrate and sulfate conditions, supporting the involvement of these anions in the degradation process. These findings highlight the complex interactions between nutrient dynamics and pesticide persistence, offering valuable insights for sustainable water management and pollution control in agro-impacted freshwater systems.

Keywords: Anion-mediated degradation, Malathion, aquatic ecosystems, Water quality, Sustainable water management