Investigating the Remediation of Soils Polluted with Heavy Metals as a Case Study

Abstract Irrigation of the vegetables by polluted wastewater leads to accumulation of heavy metals in these plants. Heavy metals fixation in-situ using inorganic amendments is a method for reducing heavy metals absorption by plants. The goal of this study is to determine the efficiency of five types of amendments in heavy metals fixation in the waste-water-irrigated soils around Tabriz city. For this purpose, solutions containing Cd, Pb, Cu, Ni, and Zn were added to 0.5 g of five amendments including calcite, hematite, zeolite, illite, and bentonite and to 10 soil samples taken from the nortwest of Tabriz city. After shaking for 2 hours, concentration of these five elements in the solutions filtered by atomic absorption instrument was determined. The mean percentages of these elements were compared and the best amendments were determined by Dunkan method. There were significant differences among the amendments in terms of heavy metals retention. Calcite had the highest Cd, Ni, and Zn absorption capacities; hematite had the highest Cu and Pb absorption capacities; and illite had the least absorption capacity for the five elemnts. Calcite, zeolite, bentonite, and hematite showed a significantly higher Cd, Ni, and Zn absorbtion capacity (5%) as compared to the 10 soil samples. The highest Pb absorption capacity by calcite and hematite (without significant differences) were observed. Discussion and Calcite, hematite, and zeolite had the highest absorption of Cu. However, the highest absorption of Cu belonged to hematite with a significant difference of 5% as compared to the other two amendments. Among the five amendments, calcite and hematite showed a similar results and led to a significant increase in absorption capacity (by 5%) for the five pollutants when added to the 10 studied soil samples. These ammendments led to the reduced absorption and accumulation of the mentioned elements in the plants cultivated in the agricultural lands around Tabriz city.