heavy metal pollution in soils exposed to landfill leachate: a case study of astaneh ashrafiyeh, guilan, iran

Unsanitary landfills pose a significant threat to human and animal health, the functions of soil and water ecosystems through release of heavy metals. open and unsanitary landfills near cities and forests are a problem in northern iran. this research aimed to study the concentration of heavy metals in the dumpsites of kisom, kashal azadsara, nazoksara, and amirkiasar (astaneh ashrafiyeh county, guilan province, iran). for this purpose, 46 composite samples were collected from the downslope and upslope soils of various landfills (0-30 and 30-60 cm depths) in astaneh county. heavy metals were extracted using nitric and hydrochloric acids, and their concentration was measured by icp-oes. the investigation of metal concentrations in the soil of landfills revealed high levels of arsenic (23–30 mg/kg) and lead (138–357 mg/kg), exceeding the risk thresholds. based on the geo-accumulation (igeo) and contamination factor (cf) indexes, elements lead (pb) and arsenic (as) in kisom and amirkiasar landfills, were classified as moderate-moderate and very high-strong contamination respectively. outcomes of the pollution load (pli) and modified contamination degree (mcd) indexes showed that the kisom landfill and its downstream areas were in the moderate contamination classification. calculation of ecological risk (er) demonstrated that the kisom landfill and its downstream areas are at significant to moderate risk from lead. in addition, the kisom landfill has a 49% possibility of heavy metal pollution and the other sites have a 21% probability of contamination according to the mean erm index.