Mapping and risk assessment of heavy metals in agricultural soils of the Siakh Darengoun Region, Shiraz, ‎Iran

Document Type: Research Paper

Authors

1 Associate professor, Department of Environment, Faculty of Natural Resources and Environment, Malayer University, Malayer, Hamedan, Iran

2 PhD candidate, Department of Environment, Faculty of Natural Resources and Environment, Malayer University, Malayer, Hamedan, Iran

3 Assistant professor, Department of Environment, Faculty of Natural Resources and Environment, Malayer University, Malayer, Hamedan, Iran

Abstract

Four heavy metals were measured in forty-nine topsoil samples collected from
agricultural areas in Siakh-Darengoun, Iran. The goals were to investigate soil spatial
distribution patterns of metals; their potential ecological risk; and sources. The Hakanson
potential ecological risk index and index of geo-accumulation (Igeo) were used for
evaluating the condition of soil heavy metal enrichment and the extent of potential
ecological risk. Results demonstrated that the mean concentrations in the agricultural soils
were 2.23 mg/kg for Cd, 5.3 mg/kg for Cu, 38.002 mg/kg for Pb, and 13.84 mg/kg for Zn.
The average concentrations of Cd and Pb in the agricultural soils were higher than average
worldwide soils and for Cu and Zn, values were lower than average worldwide soils. The
spatial mapping of the distribution of heavy metals produced by kriging interpolation
showed similar patterns for all heavy metals, and higher concentrations of all heavy metals
were observed in the western and southern parts of the study area. Our findings
demonstrated that in the Siakh-Darengoun plain, natural sources affect the levels of Cu and
Zn, however, anthropogenic sources such as chemical fertilizers, especially phosphate
fertilizers could be the major sources of Cd and Pb. Hossain Abad agro industry in the west
of the study area can be considered as one of the most important heavy metal sources. The
geo-accumulation index classified Cu and Zn into no pollution levels, Cd and Pb into
unpolluted to moderately polluted level. Cd produced serious ecological risk in agricultural
soils and was the main pollutant, while the Cu, Pb and Zn had low ecological risk.
Comprehensive potential ecological risk indexes of all metals showed that the soils in Siakh
Darengoun were suffering from high level of ecological risk.