Chemical Fractionation of Iron and Manganese in Soil Adjacent to Khuzestan Steel Company

Presence of metals in soils in various chemical forms can affect their role in development of nutritional effects or contamination. Considering the proven effects of the Khuzestan Steel Company on contamination of surrounding soils, the purpose of this study was: (1) to investigate the chemical distribution of iron and manganese in soils taken from the vicinity of the Khuzestan Steel Company, and (2) to determine the correlation of the chemical forms of these elements with some soil characteristics and concentrations in the aerial parts of the garden cress plant. After preparation of the soil sample, physical and chemical properties were determined by standard methods. Sequential extraction was performed by modified BCR method. The data were used to calculate the risk assessment code in the soil, reduced partition index, the ratio and risk index in the plant and the bioavailability factor. Based on the results for iron, the soluble, exchangeable, and acid extractable fractions constituted 0.13% of the total iron concentration in the soil, including 44.1%, 0.9% and 54.8% as, respectively, reducible, oxidizable, and residual fractions. Therefore, the highest amount of iron in the soil was in the residual and reducible fractions, which are stable and relatively stable parts of solid phase in the soil. In case of manganese, soluble, exchangeable and carbonate fraction constituted 12.3 percent of total manganese concentration in the soil, including 51.5%, 0.7% and 45.4% as, respectively, reducible, oxidizable and residual fractions. Iron had lower amounts in soluble, exchangeable, and carbonated forms as compared to manganese, therefore, all calculated indices for iron showed no contaminated situation. In case of manganese, the conditions were different and the share of soluble, exchangeable, and carbonate was significant. Due to the positive and significant correlation of this part with concentration of element in the plant, hazard quotient was also increased in plant. Concerning both elements, the bio-concentration factor was lower than its permitted value, but due to the high concentrations of these elements in the soil and the normal vegetation of this region, it seems necessary to pay attention to the type of cultivated plant.