A Cylindrical Model of Pyrite Oxidation in Coastal Acidic Soils with Michaelis-Menten Uptake Kinetics

Abstract

Oxidation of pyrites in coastal Australian soils has been a concern for researchers in recent times. Acid pollution of creeks and rivers close to estuaries has been attributed to pyrite oxidation (Indraratna, 1997). The leaching of acid through the waterways to the estuarine system has led to a number of environmental problems such as destruction of fish, oysters, and other important marine life, including their habitats. Loss of infrastructure and lower levels of agricultural production have also been documented in the acid sulfate soils literature (Blunden and Indraratna, 1997; Blunden et al., 1997). A few remedial strategies, such as manipulation of the water table, have been considered by the University of Wollongong's acid sulfate soils group to deal with the problems in the South Coast of Illawarra (New South Wales, Australia). Artificially raising water tables tends to submerge the pyritic layer, thus preventing oxygen from reaching the layer and oxidizing the pyrites. Blunden (2000) monitored the effect of groundwater manipulation at Berry and developed a three-dimensional model to predict the amount of acid produced during droughts (see also Blunden and Indraratna, 1999). More recently, a novel tidal buffering strategy in floodgated drains has been implemented. The drainwater retains a high level of acidity that may be neutralized by the action of bicarbonates and carbonates transported upstream via the tidal Broughton creek (New South Wales). Otherwise, the leached acid flows into the waterways, severely degrading the creek water quality. However, before remediation strategies can be undertaken, an accurate estimate of the total acid production in the pyritic layer is usually required. A few models for this purpose exist in the literature that have been utilized in the past, but a novel cylindrical model is developed in this article. The predictions of the new approach are compared with those of other …