A GIS Technique for Estimating Natural Attenuation Rates and Mass Balances
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Durant, N.D., P. Srinivasan, C.R. Faust, D.K. Burnell, K.L. Klein, and D.S. Burden. (2001). "A GIS Technique for Estimating Natural Attenuation Rates and Mass Balances, " In: A. Leeson, M.E. Kelley, H. Rifai, and V. Magar (Eds), Natural Attenuation.Battelle Press, Columbus, Ohio. pp. 163-171.

Battelle's Sixth International Symposium on In Situ and On Site Bioremediation, San Diego, CA, 06/04/2001. 6, 2, 2001, 163-171. EPA/600/A-02/011 (NTIS PB2002-102931). Regulatory approval of monitored natural attenuation (MNA) as a component for site remediation often requires a demonstration that contaminant mass has decreased significantly over time. Successful approval of MNA also typically requires an estimate of past and future natural attenuation rates. Calculation of electron acceptor and/or donor mass budgets is also useful in establishing the potential effectiveness of MNA. In this paper we present the application of the GIS program (TINMASS) for quantifying and visualizing contaminant and electron acceptor/donor mass-in-place. TINMASS uses a triangulated irregular network (TIN) to interpolate dissolved contaminant mass between monitoring points. The technique is best suited to sites where the plume has reached a steady-state, and the existing network of monitoring wells includes points located at or outside the perimeter of the plume, both horizontally and vertically. Natural attenuation rates can be estimated from the slope of the line formed by a log-linear plot of contaminant mass versus time. We present an example application illustrating use of the method for mass-balance analysis of sequential decay of trichloroethene. A second example is presented illustrating use of the method for evaluating fuel hydrocarbon degradation by quantifying masses of biodegradation end products.

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