Risk Assessment of Heavy Metals in Soils around Khuzestan Steel Company

  Heavy metals are the pollutants that became a global problem because of their stability in environment. Each year on a global scale thousands of tons of heavy metals are release into the soil system. The most important pathway of exposure to human is daily intake of food. Accumulation of heavy metals in soil and cross the critical limit, make unsafe food which is menacing human health. The human body is adopted with essential elements such as iron, copper, manganese and zinc in special dose but high concentration of iron and manganese cause Parkinson's disease. High concentration of copper causes damage to the liver and high concentration of zinc causes malfunctioning of copper which has effect on immune system. Other metals such as lead and cadmium at any concentrations induced renal tumors, reduced growth and increased blood pressure, therefore, the risk of cardiovascular diseases for adults can be increased.This experiment was conducted to evaluate the non-carcinogenic risk assessment of heavy metals in spinach and coriander grown on metal contaminated soils which were collected from vicinity of Khuzestan Steel Company. For this purpose, topsoil samples (0-15 cm) were collected from around of Khuzestan Steel Company according to prevailing wind direction (east-west). Exact sampling location was determined using GPS. Total metal content was determined using aqua-regia solution digestion method. EDTA and DTPA extractable metal also measured with standard methods. The experiment was laid out in factorial completely randomize designs with three treatments consist of distance (100, 1000 and 10000 meters), vermicompost (0, 3% w/w) and peat in (0, 3% w/w) with three replications. Seeds of spinach and coriander were sown in pots and harvested after 8 weeks. Total metal content in plants analyzed after digestion with di-acid mixture. According to toxic level of Zn, Cu, Cd, Pb and Ni hazard quotient was calculated. The results showed that organic manures stabilize metals and reduce the risk of their release into the environment. The effect of Peat on adsorption and reducing heavy metals transfer to plant was higher than vermicompost, whiles vermicompost was more effective in increasing fresh and dry weight of both of plants. By and large, heavy metals were reduced in soils as distance from factory increased. This is indicating the role of the factory to contaminate the surrounding land. Hazard quotient value in case of lead and cadmium were more than permissible limit but about others were acceptable which may be related to soil properties which are preventing heavy metals solution. According to nutrition aspects of vegetables and importance of providing high quality food, application of organic manure in soil can be effective not only in increasing quantity of production but also in quality of them especially in case of polluted area.