ecological risk assessment of toxic elements in the soil for some animal groups (case study: golestan province)

numerous ecological risk assessment methodologies have been developed over the last twenty years around the world for evaluating effects of pollutant on receptors such as different wildlife species. but so far such methods have only rarely been used to determine potential ecological risks in iran. therefore in this study we used one of these methodologies (eco-ssls) to determine ecological risk for some different wildlife groups. to this end, considering soil maps, geology, land use, and distribution of pollutant sources, including the location of mines, industry, main roads, hazardous waste sites, agricultural lands, 216 surface soil samples (0-30 cm) were collected from golestan province, north of iran were subjected to a total digestion technique and analyzed for as, cd, cu, mn and zn. ordinary kriging was used to predict soil concentrations. metal concentrations maps were then used to map ecological risk of hms based on the usepa’s eco-ssls to assess their ecological risks posed by these heavy metals for plants, invertebrates and vertebrates groups. the results showed that the average concentrations of as, cd, cu, mn and zn in soil of golestan were up to 9.10, 0.12, 24.42, 700.31and 82.08 mg/kg, respectively, which are much higher than their natural background values. results showed that the mean concentrations of these heavy metals were lower than potential effect levels. among the metals, mn and zn showed a higher ecological risk than the others. ecological risk further indicated that golestan was not suffering from serious metal contamination based on eco-ssls methodology. generally maps of risk based on the usepa’s eco-ssls (for plants, invertebrates and vertebrates) showing that wildlife may be partly at risk but that the relevance of eco-ssl values is questionable and the present study found that, although this methodology was of a high scientific standard, but it seems it would need modification before its using in iran.