An Investigation on Interactions between Plant Physiological-Hydrological-Biogeochemical processes and Acid Mine Drainage in Coal Refuse Piles using Optimality Principle Theory

Abstract

Human civilization has changed the global biogeochemical cycles since last century. Carbon and nitrogen cycles have been affected by industrialization and by disturbance of natural vegetation distribution (i.e. deforestation, fires, agriculture and mining). As one of the pollution processes, Acid Mine Drainage (AMD) has played a special role on disturbances on water, carbon and nitrogen cycles. The study of this role is the main part of analysis in the present dissertation. More specifically, this work investigates the reciprocal action between hydrological and biogeochemical processes after coal mines disturbances by applying a comprehensive mathematical formulation to assess the effects of vegetation as passive phytoremediation on AMD in two coal refuse mines using an optimal plant physiological approach. The development of this dissertation has resulted in the following findings: 1) The optimality formulation developed in this dissertation, based on minimum unit cost function, could be extended to integrate water-stress conditions in a more constrained manner than the majority of optimal formulations presented in literature. 2) The strategy of having as many as possible constraints to avoid parameter equifinality has been a point paramount significance in the formulation in this study. 3) The analysis and simulations show that the main interactions between the biogeochemical processes and pyrite oxidation as main AMD processes are driven primarily by the seasonally plant evapotranspiration through the soil moisture variation; the effect of mineral nitrogen processes and organic matter oxidation reducing the pH; and the solute plant uptake reducing the amount of concentrations. 4) The long-term simulation of passive bioremediation with grass vegetation has shown to be environmentally efficient only in the amended layer. On the other hand, using tree vegetation suggests better performance to reduce solute concentrations and increase the pH. 5) The solute transport simulations make possible to establish an estimation of the autonomous time of pollution recovery at watershed scales. 6) Finally, the use of vegetation as passive bio-remediation, such as grass or tree vegetation, is worth in terms of surface water quality