Effect of Calcium Magnesium Acetate on Heavy Metal Mobility in Soils1
- H. A. Elliott and
- J. H. Linn2
Calcium magnesium acetate (CMA) is a promising replacement for traditional roadway deicing salts. Prepared in a 3:7 Ca/Mg molar ratio, CMA was studied to assess its impact on the mobility of metals in contaminated soils. In batch soil suspensions (pH 3–7), 0.01 and 0.1 M CMA solutions substantially enhanced Zn and Cu desorption from a metal-enriched soil. In soil columns leached with acidified (pH 4) 0.01 M CaCl2, a thin layer of CMA initially increased metal efflux. Preferential adsorption of Ca2+ and Mg2+ at exchange sites (i) displaced bound metal ions into solution and (ii) desorbed H+, which promoted dissolution of metal-containing solid phases. This was counteracted by the pH neutralizing effect of acetate ions, so that within 10 pore volume displacements, the presence of CMA resulted in a net suppression of leachate metal levels. In pH-controlled batch experiments, metal solubilization was not significantly different between equimolar amounts of CMA and the Cl− or NO−3 salts. Thus, under the experimental conditions, acetate complexation played a minor role in metal mobilization. Highway deicing with CMA may temporarily increase translocation of metals in strongly buffered acid roadside soils. Input of acetate ions and an increase in exchangeable bases with sustained CMA use should render northeastern USA soils less vulnerable to acidification, thereby inhibiting conditions that promote metal solubilization.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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