Predicting dense nonaqueous phase liquid dissolution using a simplified source depletion model parameterized with partitioning tracers

Abstract

[1] Simulations of nonpartitioning and partitioning tracer tests were used to parameterize the equilibrium stream tube model (ESM) that predicts the dissolution dynamics of dense nonaqueous phase liquids (DNAPLs) as a function of the Lagrangian properties of DNAPL source zones. Lagrangian, or stream-tube-based, approaches characterize source zones with as few as two trajectory-integrated parameters, in contrast to the potentially thousands of parameters required to describe the point-by-point variability in permeability and DNAPL in traditional Eulerian modeling approaches. The spill and subsequent dissolution of DNAPLs were simulated in two-dimensional domains having different hydrologic characteristics (variance of the log conductivity field = 0.2, 1, and 3) using the multiphase flow and transport simulator UTCHEM. Nonpartitioning and partitioning tracers were used to characterize the Lagrangian properties (travel time and trajectoryintegrated DNAPL content statistics) of DNAPL source zones, which were in turn shown to be sufficient for accurate prediction of source dissolution behavior using the ESM throughout the relatively broad range of hydraulic conductivity variances tested here. The results were found to be relatively insensitive to travel time variability, suggesting that dissolution could be accurately predicted even if the travel time variance was only coarsely estimated. Estimation of the ESM parameters was also demonstrated using an approximate technique based on Eulerian data in the absence of tracer data; however, determining the minimum amount of such data required remains for future work. Finally, the stream tube model was shown to be a more unique predictor of dissolution behavior than approaches based on the ganglia-to-pool model for source zone characterization.

Assessment of a simple function to evaluate the relationship between mass flux reduction and mass removal for organic-liquid contaminated source zones

“…These results illustrate that the initial GTP ratio alone is not sufficient for characterizing the complete mass-flux-reduction/mass-removal relationship. This conclusion is consistent with results presented in previous studies (Christ et al, 2006; Basu et al, 2008b; Brusseau et al, 2008; DiFilippo and Brusseau, 2008). …”

“…For the specific case of the simple function used herein (equation 1), singular mass-flux-reduction/mass-removal curves are produced when n is a constant (a function only of initial conditions). However, non-singular or multi-step mass-flux-reduction/mass-removal behavior has been observed in prior flow-cell experiments (e.g., Brusseau et al, 2008; Kaye et al, 2008; DiFilippo et al, 2010; Marble et al, 2010), mathematical-modeling studies (e.g., Lemke et al, 2004; Phelan et al, 2004; Soga et al, 2004; Lemke and Abriola, 2006; Basu et al, 2008b; Maji and Sudicky, 2008; Christ et al, 2009), and for measured field data (Brusseau et al, 2007; DiFilippo and Brusseau, 2008). This non-singular behavior is a result of changes in organic-liquid distribution and relative permeability during the course of mass removal.…”

“…This approach has been applied in several studies during the past decade (e.g., Rao et al, 2002; Brooks et al, 2004; Zhu and Sykes, 2004; Falta et al, 2005; Basu et al, 2008a, 2008b; Brusseau et al, 2008; DiFilippo and Brusseau, 2008; Kaye et al, 2008, Maji and Sudicky, 2008; Parker et al, 2008, Chen and Jawitz, 2009, DiFilippo et al, 2010, Marble et al, 2010). The parameter n defines the specific mass-flux-reduction/mass-removal relationship, and is a lumped-process term that incorporates the impact of organic-liquid distribution, flow-field dynamics (e.g., changes in relative permeability), and mass-transfer processes.…”

“…Thus, other potential system-indicator parameters include global organic-liquid saturation, source-length/system-length ratio, and source-area/system-area ratio (cross-sectional areas). Statistical measures of organic-liquid saturation and permeability distributions have also been employed as system-indicator parameters (e.g., Mayer and Miller, 1996; Jawitz et al, 2005, Saenton and Illangasekare, 2007, Basu et al, 2008a, 2008b, DiFilippo et al, 2010). …”

Interphase mass transfer between fluids in subsurface formations: A review

“…Basu et al [280] used the UTCHEM code to simulate DNAPL leakage and to conduct tracer tests to be used in their stream tube model. The DNAPL was flushed with water to compare the interphase mass transfer pattern with the stream tube model predictions.…”