Phthalate esters in landfill leachate and soils of northeastern Iran: occurrence, spatial distribution, and environmental risk assessment

• Phthalate esters were widespread in landfill leachate and soils of Northeastern Iran. • Total PAE concentrations were higher in leachate than in surface and subsurface soils. • DEHP and DOP were the predominant compounds. • Physicochemical properties significantly affected PAE occurrence and mobility. • Health risk assessment revealed elevated hazard indices for children, with ingestion as the primary exposure route. Phthalate esters are widely used as plasticizers and persistent environmental contaminants with potential health risks. This study investigated the occurrence, spatial distribution, and characteristics of PAEs in landfill leachate and soil in Northeastern Iran using a systematic sampling approach. Surface and subsurface soils, along with landfill leachate, were collected and analyzed for PAE concentrations using standard chromatographic methods. GIS-based mapping was employed to evaluate spatial distribution and potential environmental fate. Physicochemical properties, including pH and EC, were also measured. Findings indicated that total PAE concentrations in surface soils ranged from 6.16 to 14.68 µg/g, while subsurface soils contained 3.46 to 9.73 µg/g. Leachate samples exhibited higher contamination levels, ranging from 1362.60 to 1974.09 µg/L. DEHP and DOP were the dominant compounds in all matrices, with DEHP contributing up to 61 percent of total PAEs in subsurface soil and 217.45 µg/L in leachate. Leachate had a pH of 6.6 and conductivity of 11.88 mS/cm, whereas soils were alkaline with lower conductivity. Health risk assessment revealed hazard indices for children of 6.0 in surface soils and 5.5 in subsurface soils, indicating ingestion as the main exposure pathway. These results highlight landfill leachate as a major transport medium for PAEs and underscore the need for monitoring and management strategies to mitigate environmental and health risks in the region.