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TERMINAL ELECTRON ACCEPTOR MASS BALANCE: LIGHT NONAQUEOUS PHASE LIQUIDS AND NATURAL ATTENUATION
Citation:
Huling*, S G., B. Pivetz, AND R. Stransky. TERMINAL ELECTRON ACCEPTOR MASS BALANCE: LIGHT NONAQUEOUS PHASE LIQUIDS AND NATURAL ATTENUATION. JOURNAL OF ENVIRONMENTAL ENGINEERING March 2002:246-252, (2002).
Description:
Nonaqueous phase liquids (NAPLs) in subsurface systems contain a relatively large amount of biodegradable organic material. During the biochemical oxidation of the organic compounds in the NAPL, electrons are transferred to terminal electron acceptors (TEA) (i.e., O2, NO3-, Mn(IV), Fe(III), SO4-2, CO2) via coupled redox reactions. A mass balance between the TEA required for mineralization of benzene, toluene, ethyl benzene, and xylene (BTEX) compounds contained in the subsurface (ground water, soil, light nonaqueous phase liquid (LNAPL)) and the total TEA available from the ground water and aquifer sediments is proposed and evaluated. Representative parameter values for aqueous and solid phase TEA, volumetric NAPL saturation, aquifer characteristics, and BTEX fractions were used. Results from a site specific example suggests that the total TEA available in the subsurface is predominantly attributed to the solid phase fraction, the aqueous phase constitutes a minor fraction, and the TEA required for BTEX mineralization is predominantly from the LNAPL. Consequently, a TEA deficit may develop in the LNAPL source area. Under these conditions, it may be invalid to assume an infinite supply of TEA and sustained bioattenuation rates. NAPL removal is one remedial option to reduce the TEA deficit in the source area.