Assessing the effect of grain-scale sorption rate limitations on the fate of hydrophobic organic groundwater pollutants

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• 作者：David Werner^a ; Hrissi K. Karapanagioti^b ; ^{karapanagioti@upatras.gr} ; David A. Sabatini^c
• 关键词：Contaminant transport ; Sorption ; Modeling ; Column tests ; Diffusion limited sorption ; Hydrophobic organic compounds
• 刊名：Journal of Contaminant Hydrology
• 出版年：2012
• 期刊代码：43_01697722
• 类别：env
• 出版时间：15 March, 2012
• 卷：129-130
• 期：Complete
• 页码：70-79
• 文件大小：1139 K

摘要

Subsurface pollutant transport models accounting for sorption rate limitations are computationally more demanding than those assuming local sorption equilibrium. We combine batch and column tests with modeling for a comparative assessment of different sorption models. For the relatively hydrophobic compound naphthalene, a model assuming local sorption equilibrium was unable to reproduce breakthrough curves in column studies with Canadian River Alluvium sediment which contains carbonaceous particles. Fully calibrated independent forward predictions of a first-order kinetic and two diffusion kinetic sorption models were in much better agreement with the experimental data. Predictions using a diffusion-limited kinetic sorption model assuming concentration-independent sorption coefficients performed equally well as a model using the Freundlich isotherm. Both diffusion-based kinetic sorption models were superior to the first-order rate approach. In the present study, the validity of the local sorption equilibrium assumption is discussed based on a Damk枚hler number and thus, the compound's sorption properties, the aquifer properties, and the scale of the process. Relatively high groundwater velocities in combination with a low sorption coefficient K_d and slow diffusion limited sorption kinetic rates are necessary conditions to justify the implementation of grain-scale sorption rate limitations in groundwater contaminant fate models. Such conditions exist when a low amount of carbonaceous particles is present in aquifers with high permeability.