Retention of Metals by Several Soils of the Southeastern United States
1988
King, Larry D.
Metals in municipal and industrial wastes can cause toxicities in plants and Cd can accumulate to concentrations that pose a health hazard for livestock and humans. Therefore, soil properties important in reducing plant availability of metals must be identified. The capacity of a soil to remove metals from solution is one estimate of the effect of that soil on metal availability to plants. Thirty five milliliter volumes of separate solutions of Cd (0.18 mol m⁻³), Co (0.34 mol m⁻³), Cr (0.77 mol m⁻³), Cu (1.10 mol m⁻³), Ni (0.34 mol m⁻³), Pb (0.97 mol m⁻³), Sb (1.64 mol m⁻³), and Zn (0.61 mol m⁻³) were equilibrated for 6 d with 5-g samples of soil from the A horizons and some B horizons of 10 mineral and three organic soils (21 samples). Total removal from solution (sorption) was determined. The samples then were extracted with 1 M KCl so the quantity of nonexchangeable metal could be determined. The respective ranges of sorbed and nonexchangeable metal, expressed as a percentage of the total quantity of metal in the initial solution, were: Cd 0–90, 0–55; Co 15–93, 1–89; Cr 31–100, 22–100; Cu 36–100, 13–100; Ni 12–95, 5–82; Pb 31–100, 14–98; Sb 50–100, 42–99; Zn 13–98, 5–94. Stepwise multiple regression was performed (on mineral soils only) using sand; silt; clay; pH; cation exchange capacity (CEC); exchangeable cations; organic matter; dithonite-extractable Al and Fe; and ammonium oxalate-extractable Al, Fe, and Mn as independent variables and the quantity of sorbed or nonexchangeable metal as the dependent variable. Sorbed and nonexchangeable Cd, Co, Cu, Ni, and Zn were related mainly to soil pH or dithonite-extractable Fe (Fed). Sorbed and nonexchangeable Cr, Pb, and Sb were related mainly to Fed, ammonium oxalate-extractable Fe, Sand, or clay. Relative retention of metals by soil was in the order Pb > Sb > Cu > Cr > Zn > Ni > Co > Cd. Although CEC is widely used in regulations governing metal loading rates on agricultural land, the results of this study indicate that Fe oxides and clay content would be better parameters to use for soils of the southeastern USA. Paper no. 10853 of the Journal Series of the North Carolina Agric. Res. Service, Raleigh, NC. Research supported in part by funds from Fiber Industries, Inc., Charlotte, NC.
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