[Effect of chemical additives on the availability of heavy metals [Pb, Cd, Zn] in soil]

ABSTRACT

Hazards of heavy metals on human health and cleaning up contaminated soils with heavy metals by microorganisms and plants are very important subject. This study was performed to evaluate the effect of additives on the availability of Pb, Cd and Zn in the soil of Amol industrial areas. The soil after mixing by a concrete mixer was dried in the oven and then grounded and passed through polyethylene sieve with 2[mm] holes. The soil extraction was done by distilled water, Ca Cl[2], KNO[3], ammonium citrate and EDTA in 0.25, 0.5, 1,2 and 4 molar and mixed by a shaker in 75 rpm for 10 hours. Finally, concentration of Zn, Pb and Cd as [micro]g/gr were measured by atomic absorption spectrometry. In this study, concentration of Pb, Cd and Zn were 13510 +/- 1241 [micro]g/gr, 127 +/- 16.50[micro]g/gr and 3000 +/- 1180[micro]g/gr, respectively. It has been determined that the availability of Zn with different additives and with distilled water was more than the availability of Pb and Cd. Mean concentration of Pb by EDTA, ammonium citrate and potassium nitrate were 2110[micro]g/gr, 1025[micro]g/gr and 195[micro]g/gr, respectively. Mean concentrations of Cd by these additives were 83[micro]g/gr, 71 [micro]g/gr and 56[micro]g/gr respectively and mean concentrations of Zn were 7894[micro]g/gr, 4982[micro]g/gr and 2744[micro]g/gr. The best concentration of Zn and Cd was obtained by KNO[3] in two molarity and by EDTA and ammonium citrate in 1 molarity. Furthermore, the best concentration of Pb was obtained by EDTA and ammonium citrate in one molarity and by KNO[3] was obtained in more than one molarity. Using chemical additives such as EDTA and ammonium citrate are effective to increase availability of heavy metals