10.2190/7W4W-1620-R781-PRA4 7W4W1620R781PRA4 1 Model Uncertainty and Parameter Sensitivity in Linear Retardance Formulations 101 120 20020509 20020509 20020509 20020509 7W4W1620R781PRA4.pdf http://baywood.metapress.com/link.asp?target=contribution&id=7W4W1620R781PRA4 2 Zhenquan Chen William F. McTernan School of Civil Engineering, Oklahoma State University Preliminary sensitivity and uncertainty analyses were performed to examine the effects of adsorption parameter and model selection on solute transport. It was found that while sensitivity increased with increasing retardation factor (R), local maximums existed for specific mass transfer coefficients. Comparisons between the concentrations predicted by equilibrium and non-equilibrium models showed that in the time period 0 < T ≤ R, the traditional equilibrium model always under-predicted the concentration simulated by non-equilibrium assumptions. A maximum possible error of -100 percent existed. For the time T > 2R, however, the equilibrium assumption always over-predicted the concentration with a maximum possible error of +25 percent. For the time R < T ≤ 2R, the equilibrium may either under- or over-predict the output concentration, with a possible error ranging from -50 to +25 percent. The discrepancies between equilibrium and non-equilibrium models increased rapidly as the mass transfer coefficient decreased. This indicated that significant errors may result from using equilibrium transport model to simulate solutes undergoing non-equilibrium adsorption, especially for hydrophilic compounds where mass transfer rate are slow. Y. Y. Haimes, Risk Assessment for the Prevention of Groundwater Contamination, in <i>Groundwater Contamination (Studies in Geophysics)</i>, National Academy Press, Washington, D. C., 1984. S. J. Burges and D. P. Lettenmaier, Probabilistic Methods in Stream Quality Management, <i>Water Resources Bulletin, 11</i>:1, pp. 115-130, 1975. J. P. Villeneuve, P. Lafrance, O. Banton, P. Frechette, and C. Robert, A Sensitivity Analysis of Adsorption and Degradation Parameters in the Modeling of Pesticide Transport in Soils, <i>Journal of Contaminant Hydrology, 3</i>, pp. 77-96, 1988. K. Loague, R. E. Green, T. W. Giambelluca, T. C. Liang, and R. Yost, Impact of Uncertainty in Soil, Climatic and Chemical Information in a Pesticide Leaching Assessment, <i>Journal of Contaminant Hydrology, 5</i>, pp. 171-194, 1990. M. A. Medina, Jr., J. B. Butcher, and C. M. Marin, Monte Carlo Analysis and Bayesian Decision Theory for Assessing the Effects of Waste Sites on Groundwater, II: Applications, <i>Journal of Contaminant Hydrology, 5</i>, pp. 15-31, 1989. Z. Chen and W. F. McTernan, Multi-Substrate, Multi-Option Groundwater Transport Model, paper accepted for publication in <i>Journal of Contaminant Hydrology</i>, 1992. J. C. Means, S. G. Wood, J. J. Hassett, and W. L. Banwart, Sorption of Polynuclear Aromatic Hydrocarbons by Sediments and Soils, <i>Environmental Science and Technology, 14</i>:12, pp. 1524-1528, 1980. J. J. Hasset, J. C. Means, W. L. Banwart, S. G. Wood, S. Ai, and A. Khan, Sorption of Dibenzothiophene by Soils and Sediments, <i>Journal of Environmental Quality, 9</i>, pp. 184-186, 1980. R. A. Freeze and J. A. Cherry, <i>Ground Water</i>, Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1979. Z. Chen, W. F. McTernan, and A. L. Hines, A Preliminary Investigation into the Mass Transfer Properties of a Pesticide onto Abiotic Media, <i>Journal of Environmental Systems, 20</i>:3, pp. 91-109, 1990-1991. A. L. Hines and R. N. Maddox, <i>Mass Transfer - Fundamentals and Applications</i>, Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1985. H. Siegrist and P. L. McCarty, Column Methodologies for Determining Sorption and Biotransformation Potential for Chlorinated Aliphatic Compounds in Aquifers, <i>Journal of Contaminant Hydrology, 2</i>, pp. 31-50, 1987. W. Z. Zhong, A. T. Lemley, and R. J. Wagenet, Quantifying Pesticide Adsorption and Degradation during Transport through Soil to Groundwater, in <i>Evaluation of Pesticides in Ground Water</i>, W. Y. Garner, R. C. Honeycutt, and H. N. Nigg (eds.), American Chemical Society, Symposium Series, 315, pp. 61-77, 1986. J. F. Sykes, J. L. Wilson, and R. W. Andrew, Sensitivity Analysis for Steady-State Groundwater Flow Using Adjoin Operators, <i>Water Resources Research, 21</i>:3, pp. 359-371, 1985.