Experimental study reveals precipitation of stable ferric hydroxide gel in irrigated greensand, suggesting surface energy considerations govern long-term mineral attenuation of heavy metals.
Fe57 Mössbauer spectroscopy has been used to determine the nature of iron-containing minerals in Lower Greensand samples from an experimental lysimeter at Uffington, Oxfordshire, both before and after a three-year irrigation with a synthetic heavy metal leachate. Analysis of the spectra measured at 300°, 77°, and 4.2°K and at 4.2°K in an applied field of 45 kOe shows that iron is present in the uncontaminated sandstone in fine-grained goethite (α-FeOOH) and glauconite. In the irrigated samples iron is precipitated as a fine-grained ferric hydroxide gel having values for the hyperfine field at 4.2°K of 435 and 470 kOe. The stability of the gel over the three-year period of irrigation may be explained by surface energy considerations.
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Ross et al. (1980) studied this question.
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