• • Non-target HRMS screening identified 417 emerging contaminants across 8 categories in metro depot wastewater, with 48 at Level 1 confidence; pesticides dominated in detection frequency and concentration, constituting the primary contaminant load—underscoring the need for pesticide-focused monitoring in urban transport infrastructure.
• • Spatial distribution varied significantly: industrial materials concentrated in storeroom S1, pharmaceuticals peaked in office/residential S2, and pesticides were highest at S2 but still present at S3, indicating multi-source inputs and mixed dilution/attenuation—necessitating zone-specific management strategies.
• • Semi-quantitative analysis of 24 pesticides revealed distinct concentration gradients; e.g., bifenox concentrations were 515.68 ng/L at S2, 60.07 ng/L at S1, and 35.69 ng/L at S3, demonstrating dilution and attenuation along the drainage path—critical for predicting environmental transport and risk.
• • Detection of certain pesticides only at the final discharge outlet (S3) suggests potential transformation products or external inputs, highlighting that terminal effluent may pose unrecognized risks—emphasizing the need for comprehensive monitoring beyond source zones.