Herbicides in landfill environments: multi-source characterization and priority risk pollutants in leachate and adjacent waters.

This study investigated the occurrence, distribution, and ecological risks of 29 herbicides in water bodies surrounding a landfill in North China. Analysis revealed that 24 herbicides were ubiquitously detected, though at trace concentrations (ng L-1 level). The herbicide compositions varied significantly among the leachate, groundwater, and surface water samples. Spatial distribution, together with principal component analysis and Pearson's correlation analysis, indicated diverse sources of herbicide contamination in the surrounding waters. However, the landfill is effective in preventing herbicides from spreading into adjacent aquatic systems via leachate, which validates the reliability of its engineered anti-seepage design. Three primary components were identified within the dissolved organic matter (DOM) using parallel factor analysis. Notably, the percentage of tyrosine-like compounds (C1) in the DOM, combined with the humification index (HIX), has been proposed as a potential indicator for assessing the extent to which water bodies are affected by leachate. Generally, a low C1 proportion coupled with a high HIX suggests a significant influence from landfill or similar anthropogenic inputs. In terms of ecological risk, sulfonylurea herbicides (SHs) posed the highest concern, whereas amides (AHs) and triazine herbicides (THs) exhibited lower risks or require further evaluation. Eleven specific herbicides (5 SHs, 4 THs, and 2 AHs) were identified as high-priority toxic substances warranting special attention in future research. These findings highlight the need for continued monitoring and management of herbicide contamination in landfill environments to safeguard water resources.