NAPL source zone depletion model and its application to railroad-tank-car spills.

We developed a new semi-analytical source zone depletion model (SZDM) for multicomponent light nonaqueous phase liquids (LNAPLs) and incorporated this into an existing screening model for estimating cleanup times for chemical spills from railroad tank cars that previously considered only single-component LNAPLs. Results from the SZDM compare favorably to those from a three-dimensional numerical model, and from another semi-analytical model that does not consider source zone depletion. The model was used to evaluate groundwater contamination and cleanup times for four complex mixtures of concern in the railroad industry. Among the petroleum hydrocarbon mixtures considered, the cleanup time of diesel fuel was much longer than E95, gasoline, and crude oil. This is mainly due to the high fraction of low solubility components in diesel fuel. The results demonstrate that the updated screening model with the newly developed SZDM is computationally efficient, and provides valuable comparisons of cleanup times that can be used in assessing the health and financial risk associated with chemical mixture spills from railroad-tank-car accidents.

[1]  Pedro J. J. Alvarez,et al.  A Comparison of Benzene and Toluene Plume Lengths for Sites Contaminated with Regular vs. Ethanol‐Amended Gasoline , 2003 .

[2]  Eungyu Park,et al.  Modeling field‐scale dense nonaqueous phase liquid dissolution kinetics in heterogeneous aquifers , 2004 .

[3]  J. Quirk,et al.  Permeability of porous solids , 1961 .

[4]  Peter Grathwohl,et al.  Diffusion in Natural Porous Media: Contaminant Transport, Sorption/Desorption and Dissolution Kinetics , 1998 .

[5]  Christopher P L Barkan,et al.  An environmental screening model to assess the consequences to soil and groundwater from railroad-tank-car spills of light non-aqueous phase liquids. , 2009, Journal of hazardous materials.

[6]  Georg Teutsch,et al.  Estimation of emission from an LNAPL contaminated zone considering groundwater recharge , 2008 .

[7]  Mario Schirmer,et al.  Dissolution and mass transfer of multiple organics under field conditions: The Borden emplaced source , 1999 .

[8]  Susan E. Powers,et al.  Modeling the partitioning of BTEX in water-reformulated gasoline systems containing ethanol , 1998 .

[9]  Kent S. Udell,et al.  Nonaqueous phase liquid transport and cleanup: 1. Analysis of mechanisms , 1988 .

[10]  Ronald W. Falta,et al.  Modeling sub‐grid‐block‐scale dense nonaqueous phase liquid (DNAPL) pool dissolution using a dual‐domain approach , 2003 .

[11]  M. Fernandes,et al.  Cosolvency effect in subsurface systems contaminated with petroleum hydrocarbons and ethanol. , 2004, Water research.

[12]  James W Jawitz,et al.  Evaluation of simplified mass transfer models to simulate the impacts of source zone architecture on nonaqueous phase liquid dissolution in heterogeneous porous media. , 2008, Journal of contaminant hydrology.

[13]  Bernard H. Kueper,et al.  An analytical solution to multi-component NAPL dissolution equations , 2007 .

[14]  Peter Grathwohl,et al.  Time scales of organic contaminant dissolution from complex source zones: coal tar pools vs. blobs. , 2002, Journal of contaminant hydrology.

[15]  Ralph C. Heath,et al.  WHAT ABOUT GROUND WATER , 1973 .

[16]  Thomas F Parkerton,et al.  Five-stage environmental exposure assessment strategy for mixtures: gasoline as a case study. , 2005, Environmental science & technology.

[17]  D. Huntley,et al.  Persistence of LNAPL sources: relationship between risk reduction and LNAPL recovery. , 2002, Journal of contaminant hydrology.

[18]  Francis A. DiGiano,et al.  Process Dynamics in Environmental Systems , 1996 .

[19]  Susan E. Powers,et al.  An experimental investigation of nonaqueous phase liquid dissolution in saturated subsurface systems: Transient mass transfer rates , 1992 .

[20]  I. Klenk,et al.  Transverse vertical dispersion in groundwater and the capillary fringe. , 2002, Journal of contaminant hydrology.

[21]  Albert J. Valocchi,et al.  A critical evaluation of the local-equilibrium assumption in modeling NAPL-pool dissolution , 1999 .

[22]  Kurt D. Pennell,et al.  Estimating mass discharge from dense nonaqueous phase liquid source zones using upscaled mass transfer coefficients: An evaluation using multiphase numerical simulations , 2006 .

[23]  Peter Grathwohl,et al.  Determination of Transverse Dispersion Coefficients from Reactive Plume Lengths , 2006, Ground water.