stabilization of heavy metals in tehran agricultural land

in order to prevent contamination of heavy metals accumlation in soil, plant, and ground water, several methods of prevention are studied, and tested worldwide. one of the method which has not been studied and applied in iran is stabilization of heavy metals in soil by using clay minerals. clay minerals due to hydration properties can adsorb organic and inorganic substances. two clay minerals were used in this research: bentonite with chemical structure of 2 to i (two layers of silica and one layer of aluminum) with cec equal to 85 meq/l 00 grams and kaoline with chemical structure of one to one (one layer silica and one layer aluminum) and cec=3 meq/ l 00 grams of soil. the physical and chemical properties of these two kinds of clays were different. stabilization of heavy metals with different percentages of these two clays (7%, 15%, 22%) with different ph (4,7,8,11.5) were studied. the results indicate that with increasing of stabilizing agent at ph = 7.8 and greater, stabilization of heavy metals increased significantly. the results 'also indicate the stabilization of heavy metals decreased rapidly at ph 4 and lower. the results of this study agree with the work of pervious reseachers