Severe Multi-Contaminant River Pollution from an Unlined Municipal Landfill in Semi-Arid Northwest Iran

Unlined municipal landfills in semi-arid regions pose significant risks to adjacent rivers through leachate migration. This study quantifies downstream pollution from a >۲۰-year-old landfill in Northwest Iran, assessing impacts on a ۱۵-km perennial river segment. Water and sediment samples were analyzed across upstream, near-field, and far-field zones. Near-field water exhibited severe hypoxia (DO ۳.۲ mg/L), high organic loading (COD ۹۸.۶ mg/L), and elevated ammonium (NH₄⁺-N ۱۴.۷ mg/L), exceeding Iranian standards by up to ۷۳.۵× for ammonium. Heavy metals such as Pb (۶۸.۴ µg/L) and Cd (۵.۹ µg/L) surpassed WHO limits, while sediments showed moderate to heavy contamination (Igeo ۲.۴–۲.۸). Organic micropollutants, including DEHP and naphthalene, presented high ecological risks. Principal component analysis confirmed leachate as the dominant pollution source, and exponential decay models indicated ۸۰–۹۰% attenuation within ۵ km downstream, although sediments retained legacy contaminants. The results define a ۳-km high-risk buffer and underscore the need for urgent mitigation measures including liner installation, leachate collection, and riparian protection to safeguard water quality and aquatic ecosystems in semi-arid regions.

کلیدواژه ها:

Landfill Leachate ، river pollution ، Northwest Iran ، heavy metals ، Organic micropollutants