Residue Characteristics and Ecological Risks of Glyphosate and Aminomethylphosphonic Acid in a Karst Watershed: A Case Study of the Yangmei River Sub-Basin

This study investigates the residue characteristics and potential ecological risks of glyphosate (GLY) and its primary metabolite, aminomethylphosphonic acid (AMPA), in the karst region, specifically focusing on the Yangmei River sub-basin. Water samples from the river were collected in April, June, August, and October of 2023, alongside 20 soil samples taken based on agricultural tillage practices. The residue characteristics of GLY and AMPA were analyzed, and their potential ecological risks were assessed using the Risk Quotient (RQ) method. The results indicated that the residues of GLY and AMPA in the soil of the Yangmei River basin exhibited spatial heterogeneity. The GLY content in the soil ranged from non-detectable (nd) to 888.85 μg/kg, with an average concentration of 262.53 μg/kg. The AMPA content varied from 47.90 to 2102.10 μg/kg, with an average of 465.52 μg/kg. Glyphosate pollution in the soil of the Yangmei River basin was determined to pose a moderate ecological risk. In the water of the Yangmei River basin, GLY concentrations ranged from 0 to 204.0 μg/L, with an average of 50.91 μg/L, while AMPA concentrations varied from 0 to 127.26 μg/L, averaging 26.51 μg/L. The highest GLY concentration was recorded in June, with detection rates for GLY being higher in April and June. The spatial distribution of GLY and AMPA was uneven. Glyphosate pollution in the water environment of the Yangmei River basin also presents a moderate ecological risk. Moreover, glyphosate has negatively impacted the aquatic environment, and its effects on water eutrophication should not be overlooked in efforts to prevent and control this phenomenon.