Pesticide and Transformation Product Occurrence and Ecological Risks in Irrigation Water of an Intensive Floriculture Region in Ecuador: Targeted and Non-Target Suspect Screening Analyses (2022-2025).

BACKGROUND

Irrigation water can transport pesticides into aquatic environments, threatening ecosystem and human health. Despite these risks, irrigation water quality remains poorly studied and non-regulated in Latin America, and in floricultural regions, revealing a critical monitoring and research gap.

METHODS

Between 2022 and 2025, irrigation water, post-harvest facility (PHF) water, river water, and groundwater samples were collected throughout Pedro Moncayo, Ecuador, a pesticide intensive floricultural region. Samples were taken along two irrigation channels from their source in Cayambe Volcano, through a floricultural region, and at the rivers where the channels flow. Targeted analysis (TA) of neonicotinoid insecticides (NNIs) and atrazine, and non-target suspect screening analysis (NTA) for a broad spectrum of pesticides (herbicides, insecticides, and fungicides) and related compounds was conducted, followed by screening-level ecological risk assessment for aquatic organisms.

FINDINGS: TA of 56 samples revealed widespread NNI contamination, with imidacloprid detected most frequently, reaching up to 612 ng/L, occurring in 40/56 (71%) of irrigation samples, increasing over time, and strongly associated with rainfall. PHF (n=2) were identified as potential point sources of pesticide pollution, while rivers (n=5) showed spatially variable contamination and groundwater exhibited repeated occurrence of imidacloprid in a residential groundwater well. NTA identified 65 pesticide-compounds, and fungicides were the most frequently detected. Ecotoxicological assessments indicated high risk to aquatic invertebrates, particularly from NNI imidacloprid and thiacloprid.

CONCLUSIONS

Intensive floriculture in Ecuador has resulted in widespread pesticide contamination of irrigation, surface water, and groundwater, underscoring the need for improved post-harvest management, targeted mitigation strategies, and region-specific regulations to protect tropical freshwater ecosystems and human health.