Assessment of heavy metals contamination in water and soil resources of Malayer plain (Marvil catchment)

Heavy metals environmental pollutions are more notable nowadays. One of the main sources of heavy metals in environment is mining and related industries. So in recent years, application of environmental geochemistry increased dramatically, particularly in contamination survey compare with the other environmental subject. Marvel basin is part of Malayer catchment and in hydrogeological division is part of Karkheh catchment basin. Study area covers 28000 m2 and is located between 48º 52 to 49º 10 east latitude and 34º 13 to 34º 00 north longitude in western Iran, southeast of Hamedan province and east of Malayer city. Ahangaran Pb-Zn mine covers about 29.25 km2 and is located in southern hillside of low elevation of Ahgangaran in north of Marvil catchment basin. Environmental contamination assessment was carried out by water and soil sampling. Water (wet and dry season) and soil samples were analyzed using an inductively coupled plasma-mass spectrometry (ICP- MS) using a Perkin Elmer model Nekson instrument for heavy metals determinations at Lab West Analytical Laboratory, Australia. Water samples were also analyzed using wet chemistry for determining major cations and anions. Physical and chemical tests were conducted in all soil samples. Obtained results were compared with local and international environmental standards for soil and water resources. Type and amount of contaminations were studied in detail considering their environmental effects. Type of water is bicarbonate with neutral to alkaline pH and its electrical conductivity (EC) is low to medium. Water resources of Marvil catchment basin in both season is suitable for drinking and agriculture use. Comparison of heavy metals in water resources with standard, indicate that it is contaminated with arsenic in dry season which in rural area is more than standard level. Other heavy elements are in safe level without any pollution. Concentration of As increases in dry season due to decline of water table level and decrease in aquifer recharge. Decline of water table in dry season affecs the As solubility around redox boundary. So dropped aquifer boundary in dry season exposed to oxidation with increase in dissolving As causing its more concentration in groundwater. Enrichment factor show low enrichment of Co, Cr, Al, V, Cu, Ni, Be, low to medium for Ba, Zn, Mn and high to extremely high for As, Ag Sb and Pb. Contamination intensity, based on geoaccumulation index, indicate a high contamination for Pb, Ag and Sb and safe level for other elements. Considering contamination factor and pollution load index, high contamination of Pb, As, Sb and Ag recorded in soil samples. Comparing with soil standards, Marvil soils are contaminated with Pb, Sb, As, Cr, Ag, Ba, Cu, Co, Be, Zn, V, Mn and Ni and it is non-contaminate with Al. It may be concluded that source of soil contamination is both geogenic and anthropogenic. Anthropogenic contamination is related to mining activity.