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CHARACTERIZATION OF METAL ADSORPTION VARIABILITY IN A SAND & GRAVEL AQUIFER, CAPE COD, MASSACHUSETTS, U.S.A.
Citation:
Fuller, C. C., J. A. Davis, J. A. Coston, AND E. Dixon. CHARACTERIZATION OF METAL ADSORPTION VARIABILITY IN A SAND & GRAVEL AQUIFER, CAPE COD, MASSACHUSETTS, U.S.A. JOURNAL OF CONTAMINANT HYDROLOGY 22(3-4):165-187, (1996).
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Description:
Several geochemical properties of an aquifer sediment that control metal-ion adsorption were investigated to determine their potential use as indicators of the spatial variability of metal adsorption. Over the length of a 4.5-m-long core from a sand and gravel aquifer, lead (Pb2+) and zinc (Zn2+) adsorption at constant chemical conditions (pH 5.3) varied by a factor of 2 and 4, respectively. Pb2+ and Zn2+ were adsorbed primarily by Fe- and Al-oxide coatings on quartz-grain surfaces. Per unit surface area, both Pb2+ and Zn2+ adsorption were significantly correlated with the amount of Fe and Al that dissolved from the aquifer material in a partial chemical extraction. The variability in conditional binding constants for Pb2+ and Zn2+ adsorption (log KADS) derived from a simple non-electrostatic surface complexation model were also predicted by extracted Fe and Al normalized to surface area. Because the abundance of Fe- and Al-oxide coatings that dominate adsorption does not vary inversely with grain size by a simple linear relationship, only a weak, negative correlation was found between the spatial variability of Pb2+ adsorption and grain size in this aquifer. The correlation between Zn2+ adsorption and grain size was not significant. Partial chemical extractions combined with surface-area measurements have potential use for estimating metal adsorption variability in other sand and gravel aquifers of negligible carbonate and organic carbon content.
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CHARACTERIZATION OF METAL ADSORPTION VARIABILITY IN A SAND & GRAVEL AQUIFER, CAPE COD, MASSACHUSETTS, U.S.A.
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