مرکز منطقه ای اطلاع رساني علوم و فناوري -

چكيده لاتين :

Various extraction procedures were employed for measuring extractable concentrations of potential toxic elements in soil. The extractability of Cd, Cu, Pb and Zn in four contaminated and four non-contaminated soils of Japan, was compared by single extraction (CaClz, DTPA, NH4CI, 0.1 M HCI and I M HCI ) and sequential extraction procedures [(six operationally defmed chemical phases, viz. water soluble (FI), exchangeable (F2), carbonate (F3), oxide (F4), organic (F5) and residual (F6) fractions)]. Extractability of metals from soils samples varied depending on metals and/or extractants used. Among the extractants, I M HCI extracted the largest proportion of Cd (79 to 96% of total), Cu (61 to 83%), Pb (51 to 99%) and Zn (23 to 52%) from soils followed by 0.1 M HCI, NH4CI, DTPAand CaClz. In all the extractants, the proportion of extractability of metals was higher in the contaminated soils than the non-contaminated soils. Regardless of soils and extractants, relative extractability was higher for Cd as compared to other three metals. The use of I M HCI may be recommended for first-level screening of soil contamination with heavy metals. The other four weak extractants are believed to provide a better assessment ofbioavailable/mobile metals content in soils than I M HCI extractant. However, 0.1 M HCI mobilized all four metals irrespective of soil types, therefore, might be the best choice if only one extractant is to be used. The sequential extraction procedures showed 22 to 64% of total Cd was in the mobile fraction (sum ofFI to F3), while the corresponding values for Cu, Pb and Zn in this fractions were 2 to 23% suggesting higher mobility of Cd than other three metals. The single extraction procedures are simple and easy to perform and obtained results are comparable with sequential extraction procedure.