### Abstract

The purpose of this work is to examine the effect of nonuniform distributions of immiscible organic liquid on dissolution behavior, with a specific focus on the condition dependency of dissolution (i.e., mass transfer) rate coefficients associated with applying mathematical models of differing complexities to measured data. Dissolution experiments were conducted using intermediate-scale flow cells packed with sand in which well-characterized zones of residual trichloroethene (TCE) and 1,2-dichloroethane (DCA) saturation were emplaced. A dual-energy gamma radiation system was used for in-situ measurement of NAPL saturation. Aqueous concentrations of TCE and DCA measured in the flow-cell effluent were significantly less than solubility, due primarily to dilution associated with the nonuniform immiscible-liquid distribution and bypass flow effects associated with physical heterogeneity. A quantitative analysis of flow and transport was conducted using a three-dimensional mathematical model wherein immiscible-liquid distribution, permeability variability, and sampling effects were explicitly considered. Independent values for the initial dissolution rate coefficients were obtained from dissolution experiments conducted using homogeneously packed columns. The independent predictions obtained from the model provided good representations of NAPL dissolution behavior and of total TCE/DCA mass removed, signifying model robustness. This indicates that for the complex three-dimensional model, explicit consideration of the larger scale factors that influenced immiscible-liquid dissolution in the flow cells allowed the use of a dissolution rate coefficient that represents only local-scale mass transfer processes. Conversely, the use of simpler models that did not explicitly consider the nonuniform immiscible-liquid distribution required the use of dissolution rate coefficients that are ∼3 orders of magnitude smaller than the values obtained from the columnexperiments. The rate coefficients associate with the simpler models represent composite or lumped coefficients that incorporate the effects of the larger scale dissolution precesses associated with the nonuniform immiscible-liquid distribution, which are not explicitly represented in the simpler models, as well as local-scale mass transfer. These results demonstrate that the local-scale dissolution rate coefficients, such as those obtained from column experiments, can be used in models to successfully predict dissolution and transport of immiscible-liquid constituents at larger scales when the larger scale factors influencing dissolution behavior are explicitly accounted for in the model.

Original language | English (US) |
---|---|

Pages (from-to) | 1033-1041 |

Number of pages | 9 |

Journal | Environmental Science and Technology |

Volume | 36 |

Issue number | 5 |

DOIs | |

State | Published - Mar 1 2002 |

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### ASJC Scopus subject areas

- Environmental Engineering
- Environmental Science(all)
- Environmental Chemistry

### Cite this

*Environmental Science and Technology*,

*36*(5), 1033-1041. https://doi.org/10.1021/es010609f

**Dissolution of nonuniformly distributed immiscible liquid : Intermediate-scale experiments and mathematical modeling.** / Brusseau, Mark L; Zhang, Zhihui; Nelson, Nicole T.; Cain, R. Brent; Tick, Geoffrey R.; Oostrom, Mart.

Research output: Contribution to journal › Article

*Environmental Science and Technology*, vol. 36, no. 5, pp. 1033-1041. https://doi.org/10.1021/es010609f

}

TY - JOUR

T1 - Dissolution of nonuniformly distributed immiscible liquid

T2 - Intermediate-scale experiments and mathematical modeling

AU - Brusseau, Mark L

AU - Zhang, Zhihui

AU - Nelson, Nicole T.

AU - Cain, R. Brent

AU - Tick, Geoffrey R.

AU - Oostrom, Mart

PY - 2002/3/1

Y1 - 2002/3/1

N2 - The purpose of this work is to examine the effect of nonuniform distributions of immiscible organic liquid on dissolution behavior, with a specific focus on the condition dependency of dissolution (i.e., mass transfer) rate coefficients associated with applying mathematical models of differing complexities to measured data. Dissolution experiments were conducted using intermediate-scale flow cells packed with sand in which well-characterized zones of residual trichloroethene (TCE) and 1,2-dichloroethane (DCA) saturation were emplaced. A dual-energy gamma radiation system was used for in-situ measurement of NAPL saturation. Aqueous concentrations of TCE and DCA measured in the flow-cell effluent were significantly less than solubility, due primarily to dilution associated with the nonuniform immiscible-liquid distribution and bypass flow effects associated with physical heterogeneity. A quantitative analysis of flow and transport was conducted using a three-dimensional mathematical model wherein immiscible-liquid distribution, permeability variability, and sampling effects were explicitly considered. Independent values for the initial dissolution rate coefficients were obtained from dissolution experiments conducted using homogeneously packed columns. The independent predictions obtained from the model provided good representations of NAPL dissolution behavior and of total TCE/DCA mass removed, signifying model robustness. This indicates that for the complex three-dimensional model, explicit consideration of the larger scale factors that influenced immiscible-liquid dissolution in the flow cells allowed the use of a dissolution rate coefficient that represents only local-scale mass transfer processes. Conversely, the use of simpler models that did not explicitly consider the nonuniform immiscible-liquid distribution required the use of dissolution rate coefficients that are ∼3 orders of magnitude smaller than the values obtained from the columnexperiments. The rate coefficients associate with the simpler models represent composite or lumped coefficients that incorporate the effects of the larger scale dissolution precesses associated with the nonuniform immiscible-liquid distribution, which are not explicitly represented in the simpler models, as well as local-scale mass transfer. These results demonstrate that the local-scale dissolution rate coefficients, such as those obtained from column experiments, can be used in models to successfully predict dissolution and transport of immiscible-liquid constituents at larger scales when the larger scale factors influencing dissolution behavior are explicitly accounted for in the model.

AB - The purpose of this work is to examine the effect of nonuniform distributions of immiscible organic liquid on dissolution behavior, with a specific focus on the condition dependency of dissolution (i.e., mass transfer) rate coefficients associated with applying mathematical models of differing complexities to measured data. Dissolution experiments were conducted using intermediate-scale flow cells packed with sand in which well-characterized zones of residual trichloroethene (TCE) and 1,2-dichloroethane (DCA) saturation were emplaced. A dual-energy gamma radiation system was used for in-situ measurement of NAPL saturation. Aqueous concentrations of TCE and DCA measured in the flow-cell effluent were significantly less than solubility, due primarily to dilution associated with the nonuniform immiscible-liquid distribution and bypass flow effects associated with physical heterogeneity. A quantitative analysis of flow and transport was conducted using a three-dimensional mathematical model wherein immiscible-liquid distribution, permeability variability, and sampling effects were explicitly considered. Independent values for the initial dissolution rate coefficients were obtained from dissolution experiments conducted using homogeneously packed columns. The independent predictions obtained from the model provided good representations of NAPL dissolution behavior and of total TCE/DCA mass removed, signifying model robustness. This indicates that for the complex three-dimensional model, explicit consideration of the larger scale factors that influenced immiscible-liquid dissolution in the flow cells allowed the use of a dissolution rate coefficient that represents only local-scale mass transfer processes. Conversely, the use of simpler models that did not explicitly consider the nonuniform immiscible-liquid distribution required the use of dissolution rate coefficients that are ∼3 orders of magnitude smaller than the values obtained from the columnexperiments. The rate coefficients associate with the simpler models represent composite or lumped coefficients that incorporate the effects of the larger scale dissolution precesses associated with the nonuniform immiscible-liquid distribution, which are not explicitly represented in the simpler models, as well as local-scale mass transfer. These results demonstrate that the local-scale dissolution rate coefficients, such as those obtained from column experiments, can be used in models to successfully predict dissolution and transport of immiscible-liquid constituents at larger scales when the larger scale factors influencing dissolution behavior are explicitly accounted for in the model.

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UR - http://www.scopus.com/inward/citedby.url?scp=0036489110&partnerID=8YFLogxK

U2 - 10.1021/es010609f

DO - 10.1021/es010609f

M3 - Article

C2 - 11917988

AN - SCOPUS:0036489110

VL - 36

SP - 1033

EP - 1041

JO - Environmental Science & Technology

JF - Environmental Science & Technology

SN - 0013-936X

IS - 5

ER -