Assessment of Landfill Leachate Effects on Heavy Metals Contamination in Water and Sediments of Garan River, Marivan County, Iran

This study assessed heavy metal contamination in the Garan River's water and sediments to evaluate the impact of landfill leachate. Pollution levels and ecological risks were quantified using established indices: contamination factor (CF), pollution load index (PLI), geoaccumulation index (Igeo), enrichment factor (EF), and potential ecological risk index (PERI). Spatially, peak dissolved metal concentrations in water occurred at points S1 and S4, while maximum sediment concentrations were found at S3, directly downstream of the leachate outfall. Water quality analysis indicated that arsenic posed both acute and chronic human health risks at all stations, and chromium posed an acute risk at all stations. Sediment assessment revealed that barium, nickel, and mercury consistently exceeded the threshold effect concentration (TEC). Furthermore, nickel and mercury surpassed the probable effect concentration (PEC) at 100% and 85.71% of stations, respectively, signaling a significant potential for adverse effects on aquatic life. Index analysis showed higher CF values in sediments than in water. The PLI trend increased in sediments but decreased in water, whereas EF was higher in water and spatially stable. The average Igeo for all metals remained below zero, classifying the area as unpolluted. The PERI indicated medium ecological risk in sediments only at stations S3, S6, and S8. While the collective indices suggest that severe, widespread pollution is not present, the identified contamination hotspots and specific risks from metals like arsenic, nickel, and mercury warrant vigilant attention. Consequently, periodic monitoring of leachate-derived metals and proactive preventive measures are critically recommended to preserve aquatic ecosystem quality.