Abstract

The widespread application of pesticides in agricultural landscapes has raised increasing concern about their ecological impacts on aquatic environments. This study applies an ecological risk assessment (ERA) framework to evaluate six major classes of pesticides: neonicotinoid insecticides, pyrethroid insecticides, organophosphate insecticides, triazine herbicides, glyphosate (and its metabolite AMPA), and azole fungicides based on secondary datasets and published monitoring studies. The prime aim had been the identification of exposure patterns, sensitive taxa, and cumulative risk of pesticide mixtures in surface waters. The monitoring data showed distinct detection profiles for different chemical classes. Neonicotinoids and glyphosate were the almost constant percentage of detection, which were chronic, baseline, contaminants with detection frequencies of 68% and 75%, respectively. Pyrethroids and organophosphates had lower frequencies and ranged from 30 to 42%, with rainfall and runoff associated with episodic peaks. Triazines (55%) and azole fungicides (40%) had intermediate levels of detection,denoting seasonality of inputs and repeated applications to agriculture. Thresholds of toxicity demonstrated very strongly individual taxon sensitivity, with aquatic invertebrates being the most sensitive to neonicotinoids, benthic invertebrates and fish to pyrethroids, and algae to triazine herbicides. RQ analysis showed that neonicotinoids (RQ: 1.2–45) and pyrethroids (RQ: 5–20) had medium to high-risk levels, while organophosphates (RQ: 0.4–16) and azoles (RQ: 0.2–17) had episodic or mixture-induced risk levels. Triazines (RQ: 0.025–0.6) and glyphosate (RQ: 0.3–3.5) posed comparatively lower but still ecologically relevant risks. Summed risk quotients (ΣRQ) frequently exceeded 1.0, particularly for invertebrates, confirming that additive and synergistic effects amplify overall risks.