| Abstract
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Iron oxidation in the presence of lake sediment collected from an acidic alpine lake was three orders of magnitude faster than in filtered lakewater without sediment. When kinetic rates in the presence of sediment were normalized on a surface area basis, they fell within a narrow range, and the assumption of a first order dependence of rate on surface area was supported. The relative influence on heterogeneous rate of ferrous iron oxidation of the five metal oxides studied can be ranked usd\rm SiO\sb2\approx Al\sb2O\sb3\ll Fe\sb2O\sb3\approx MnO\sb2\approx TiO\sb2,usd with a difference of three orders of magnitude separating the aluminum and iron oxides. The rate constants on a surface area basis were, respectively, usd1.8\times 10\sp,\ 4.6\times 10\sp,\ 1.4\times 10\sp,\ 2.3\times 10\spusd and usd5.3\times 10\spusdM atm sec m Studies at low oxygen concentrations suggested that at low pO2 oxygenation may not be first order with respect to oxygen concentration. Biological processes were found to enhance oxidation kinetics by two orders of magnitude on a surface area basis in comparison with a gamma irradiated control. Oxidation rate in the presence of irradiated sediment was in turn approximately 130 times greater than for oxidation in deionized water. The importance of biological activity in environments exhibiting photoreduction of iron was further studied by development of a polyclonal antibody test for the detection of the iron oxidizing autotroph Thiobacillus ferrooxidans. T. ferrooxidans was found in the Snake River and its tributaries in the Colorado Rocky mountains. Tests for T. ferrooxidans in samples collected at Lake Cristallina, Canton Ticino, Switzerland and McDonalds Branch, Lebanon State Forest, New Jersey were negative. Scanning electron micrographs of samples collected from McDonalds Branch indicated the presence of the iron oxidizing autotroph Gallionella ferruginea. In addition, adsorption isotherms for oxalate sorption on B-horizon and C-light soil fractions collected at the Watershed Manipulation field site, Lead Mountain, Hancock County, Maine are presented.
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