Itakura T, Airey D W, Leo C J
Australian Nuclear Science and Technology Organisation, PMB1 Menai, New South Wales 2234, Australia.
J Contam Hydrol. 2003 Sep;65(3-4):219-43. doi: 10.1016/S0169-7722(03)00002-0.
Laboratory experiments to estimate the effective molecular diffusion coefficient (D(e)) and sorption coefficient (K(d)) for volatile organic compounds through natural clayey soils were conducted using diffusion testing apparatus. The compounds tested were methyl ethyl ketone (MEK), toluene and trichloroethylene (TCE). The D(e) and K(d) values were determined by a curve fitting procedure. The compound losses, and the effects of porous disks used in the apparatus were significant. The transport of MEK was faster than that of TCE and toluene because of the lower sorption to the soils. The D(e) values of all the compounds were of the order of 10(-10) m(2)/s and smaller than the diffusion coefficient in pure aqueous solution at infinite dilution (D(0)), due to the tortuosity of the samples. The effects of the sample thickness on the parameter determination were not significant. Comparison to the K(d) values estimated from batch sorption tests and from organic carbon content (f(oc))-based predictions showed that the diffusion test results were intermediate between those from the other two methods. The diffusion tests use compacted soil samples and should be more relevant to in situ conditions, but the reliability of the tests is affected by large compound losses that cause uncertainties in their interpretation. It is recommended that more than one method be used to assess K(d) values.
使用扩散测试装置进行了实验室实验，以估算挥发性有机化合物通过天然黏土的有效分子扩散系数（D(e)）和吸附系数（K(d)）。所测试的化合物为甲乙酮（MEK）、甲苯和三氯乙烯（TCE）。D(e)和K(d)值通过曲线拟合程序确定。化合物的损失以及装置中使用的多孔盘的影响显著。由于对土壤的吸附较低，MEK的传输速度比TCE和甲苯快。由于样品的曲折度，所有化合物的D(e)值约为10^(-10) m²/s，且小于无限稀释时纯水溶液中的扩散系数（D(0)）。样品厚度对参数测定的影响不显著。与通过批量吸附试验和基于有机碳含量（f(oc)）预测估算的K(d)值进行比较表明，扩散试验结果介于其他两种方法的结果之间。扩散试验使用压实的土壤样品，应该与原位条件更相关，但试验的可靠性受到大量化合物损失的影响，这会导致其解释存在不确定性。建议使用不止一种方法来评估K(d)值。
