Immobilization of arsenic in a calcareous soil using an iron-,manganese- and aluminum-modified zeoilite

Contamination of soil and water with arsenic, which is a toxic and carcinogenic metalloid, can increase the danger of its entrance into the food chain. In order to improve the efficacy of natural zeoilte for adsorption and stabilization of arsenic in soil, an Iranian zeoilte of clinoptilolite type was modified by iron, manganese and aluminum, and used in a series of chemical extraction tests by DTPA as well as greenhouse experiments using barley as a test crop. Moreover, the biological effects of amending these soil modifiers were evaluated through measuring soil dehydrogenase and phosphatase activity. The experiment carried out in a completely randomized design with Factorial arrangement including 5 types of zeolite (modified with iron, manganese, aluminum, iron+ manganese and iron+ aluminum) and two levels (2% and 5%) of each amendment. The results of this study revealed that the applied amendments could increase the produced biomass and decrease both arsenic concentration in barely and arsenic extracted by DTPA. Also, further incorporation of amendments increased the activity of dehydrogenase, as a soil health index. However, the iron- and aluminum-modified zeolite was the only amendment which meaningfully increased the phosphatase activity. The reslts indicated that the iron-, manganese- and aluminummodified zeolite can be considered as a good alternative, low cost and environmental friendly amendment for immobilization of arsenic in contaminated soils, and can mitigate the risk associated with arsenic entrance into the food chain.