Ecological risk assessment of chlorpyrifos and TCP in a tropical mountain reservoir: Insights from passive sampling and sediment analysis

• Acute and chronic toxicity evaluated in a tropical reservoir. • Integrated with sediment analysis for spatial risk assessment. • Addresses pesticide contamination in drinking water sources. • Highlights unique hydrolysis dynamics under tropical conditions. • Supports sustainable pesticide management and regulatory improvements. Pesticide contamination in freshwater ecosystems represents a growing concern in tropical regions, where environmental conditions can influence degradation dynamics and increase ecological vulnerability. This study evaluates the ecological risks associated with chlorpyrifos, a widely used organophosphate insecticide, and its persistent metabolite 3,5,6-trichloro-2-pyridinol (TCP), in a tropical mountain reservoir in Colombia. We employed a novel integrative approach, combining passive sampling, using Semipermeable Membrane Devices and Polar Organic Chemical Integrative Samplers, with sediment analysis to quantify both compounds across multiple sites and seasons. Ecological risk was assessed using Toxic Units for acute exposure and Risk Quotients for chronic toxicity. Our findings reveal that, while TCP posed minimal acute risks, it represents a significant chronic hazard due to its persistence and sediment accumulation. In contrast, Chlorpyrifos, exhibited both acute and chronic risks even at low concentrations. These results highlight the need for tropical-specific monitoring strategies and reinforce the ecological benefits of Colombia’s 2022 chlorpyrifos ban. This study provides critical evidence to support regulatory frameworks and improving water quality management in tropical freshwater systems.