A finite-difference algorithm used to simulate radial diffusion, adsorption, and reactions of chlorinated ethenes in porous media

Simulations of radial diffusion, adsorption, and reactions of volatile organic compounds (VOCs) - trichloroethene (TCE), cis-1,2-dichloroethene (cDCE), vinyl chloride (VC), trichlorofluoroethene (TCFE) - and bromide (Br) in a porous media are conducted using rock properties identified from a mudstone aquifer in the Newark Basin, near West Trenton, New Jersey. The simulations are conducted using a finite-difference algorithm that was prepared for this investigation to solve the equation for radial diffusion, linear equilibrium adsorption, and zero- and first-order biodegradation. The simulations are conducted for a section of a rock matrix and the georeferencing is based on the locations of the well from which concentration data were collected and analyzed as part of this investigation. The model simulates concentrations in the porous media and in a borehole, which provides the boundary condition for the porous media domain. Rock properties controlling the diffusion, adsorption, and reaction of VOCs in the rock matrix are assumed to be spatially uniform. This program simulates radial diffusion, adsorption, and reaction of TCE, cDCE, VC, and TCFE in a borehole diffusion test. Adsorption is modeled by a linear sorption isotherm. Two version of the software are provided that differ only in the assumed model for biodegradation:

RDAR_0 - Biodegradation of TCE and TCFE in the borehole is assumed to be zero-order. Biodegradation of cDCE and VC in the borehole is assumed to be first-order. Abiotic degradation of TCE, cDCE, VC, and TCFE in the rock matrix (for both dissolved and sorbed phases) is assumbed to be first-order.

RDAR_1 - All degradation is assumed to be first-order. As described in the body of the paper, two sets of TCFE data were used for parameter estimation: (1) Adjusted TCFE, and (2) Original (Unadjusted) TCFE.

Simulations are conducted for five cases, with cases I-IV using entire history of VOCs in the borehole for the pre-test simulation phase. These cases are: (I) Adjusted TCFE, simultaneous fit to Br and VOC; (II) Adjusted TCFE, separate fits to Br and VOC; (III) Unadjusted TCFE, simultaneous fit to Br and VOC; (IV) Unadjusted TCFE, separate fits to Br and VOC; (V) Unadjusted TCFE, simultaneous fits to Br and VOC, borehole history simulation limited to only 2015-2017.

This USGS data release contains all of the software, input, and output files for the simulations described in the associated journal article (https://doi.org/10.5066/P99I50JE).