HR: 1340h
AN: H33F-0517    [Abstracts]
TI: Coupled Geochemical and Reactive Transport Modeling of Organic Contaminants in a Pyrite-Rich Aquifer
AU: * Sarioglu, S M
EM: savas.sarioglu@boun.edu.tr
AF: Institute of Environmental Sciences, Bogazici University, Istanbul, 34342 Turkey
AU: Copty, N K
EM: ncopty@boun.edu.tr
AF: Institute of Environmental Sciences, Bogazici University, Istanbul, 34342 Turkey
AB: Although pH is recognized as a key factor influencing bacterial activity, existing groundwater transport models generally do not directly account for the effect of pH on the biodegradation of organic compounds. The purpose of this study is to develop a coupled reactive transport and geochemical model that explicitly incorporates the effect of spatial and temporal variations of the pH on the biodegradation of organic contaminants. The model consists of two modules: a transport module and a geochemical module. The transport module uses a Crank-Nicholson finite-difference formulation to solve the groundwater flow and transport equations for the hydrocarbon, dissolved oxygen, microbial mass and all reactive groundwater species influencing the hydrocarbon biodegradation and pH distribution. The geochemical module allows for the simulation of both kinetically defined as well as geochemical equilibrium reactions. The governing non-linear system of equations is solved using an iterative multi-step operator-splitting algorithm. Both modules account for heterogeneity in the definition of the hydrogeological and biochemical parameters. For demonstration, the model is applied to a hypothetical pyrite-rich aquifer contaminated with petroleum hydrocarbons. A commonly used practice for the remediation of aquifers contaminated with petroleum hydrocarbons is the delivery of oxygen for the enhanced aerobic biodegradation of the organic contaminant. However, the presence of pyrite may interfere with the intended purpose of the supplied oxygen, leading to undesirable side effects. Specifically, oxygen readily reacts with the sulfide minerals leading to depletion of oxygen and acidification of the subsurface environment and, subsequently, the inadvertent inhibition of the microbial activity. The developed coupled geochemical and reactive transport model is used to quantify these processes and assess the dominance of the various chemical reactions. Both abiotic and biotic pyrite oxidation kinetics are incorporated in the model. The impact of heterogeneity as well as key parameters on the fate and transport of the organic contaminant is also evaluated. The example is used to demonstrate how additional measures such as the injection of alkaline solution with the oxygen may optimize the remediation process.
DE: 3210 Modeling
DE: 1829 Groundwater hydrology
DE: 1832 Groundwater transport
DE: 1045 Low-temperature geochemistry
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting