Mobility and Retention of Heavy Metals in Sandy Soils
1983
Miller, W. P. | Mc Fee, W. W. | Kelly, J. M.
The sandy soils of industrialized northwestern Indiana are contaminated with aerially deposited Cd, Zn, Cu, and Pb, which are retained largely in the upper 5 cm of soil. To evaluate the leaching of these metals, intact soil cores of the Oakville (Typic Udipsamment) series sampled from forested sites in this area were leached in the laboratory with acidified or metal-containing solutions corresponding to 1 or 10 y of simulated rainfall. Metals in the leachate were below detection limits, and analyses of core sections showed that the applied Cd, Zn, Cu, and Pb were concentrated in the litter layer and top 2.5 cm of soil. Adsorption experiments performed on 0- to 2.5-cm samples of Oakville soil containing initial levels of 5 µg Cd, 1000 µg Zn, 100 µg Cu, and 200 µg Pb/g soil demonstrated that these soils could retain up to twice the amounts of metals initially present. A similar soil with lower pH and less organic matter adsorbed less of all the metals, while showing higher retention of Cu and Pb compared with Cd and Zn. Sequential extraction of the sorbed metals showed that chelation by organic matter (Na₄P₂O₂-extractable) and surface reaction with carbonates and/or Fe oxides (EDTA-extractable) were the most likely retention mechanisms in the Oakville soil, although adsorption on cation exchange sites was observed for Cd and Zn at high loading rates.
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