Peterson J W, DeBoer M J, Lake K L
Department of Geological and Environmental Sciences, Hope College, Holland, MI, USA.
J Hazard Mater. 2000 Feb 25;72(2-3):167-78. doi: 10.1016/s0304-3894(99)00139-9.
Laboratory air sparging experiments were performed in narrow acrylic tanks to evaluate the cleanup of toluene in water-saturated sands. Air flow channels in the sediment were identified by way of a colorimetric visualization technique, which allowed pore water samples to be collected at a known horizontal distance from an air channel. Pore water was sampled at periodic intervals during sparging experiments and analyzed by gas chromatography to yield toluene concentration vs. time data. Results indicate that channelized air flow is effective in reducing toluene concentrations in the range of 36-3 ppm, within 2 to 5 days, at least up to 185 mm from an active air channel. While relatively rapid, these toluene reduction times are longer than previously published data, from similar type experiments. The discrepancy is likely a function of air delivery flow rate and proximity of sampling sites to active air channels. Data from the current investigation were used to attempt an estimate of effective diffusion coefficients (D*) for toluene in clean, well-characterized sands in which the concentration gradient was imposed by sparge air. Calculated D* values range from 2. 98x10(-8) m(2)/s to 5.74x10(-9) m(2)/s, and are significantly faster than previously published values of toluene diffusion in clay soils. However, the values are also slightly greater than diffusion coefficients for toluene in aqueous solutions, indicating that the calculations more likely estimate coefficients of hydrodynamic dispersion (D(L)).
在狭窄的丙烯酸水箱中进行了实验室空气注入实验，以评估水饱和砂中甲苯的净化情况。通过比色可视化技术识别沉积物中的气流通道，该技术能够在距空气通道已知水平距离处采集孔隙水样。在注入实验期间定期采集孔隙水样，并通过气相色谱法进行分析，以得出甲苯浓度与时间的数据。结果表明，在2至5天内，通道化气流能有效将甲苯浓度从36 ppm降低至3 ppm，至少在距活跃空气通道185毫米范围内如此。虽然甲苯浓度降低时间相对较快，但比之前类似类型实验发表的数据要长。这种差异可能与空气输送流速以及采样点与活跃空气通道的距离有关。利用本次调查的数据尝试估算甲苯在清洁、特性良好的砂中的有效扩散系数（D*），其中浓度梯度由注入空气施加。计算得出的D*值范围为2.98×10⁻⁸ 平方米/秒至5.74×10⁻⁹ 平方米/秒，明显快于之前发表的甲苯在粘土中的扩散值。然而，这些值也略大于甲苯在水溶液中的扩散系数，这表明计算结果更可能估算的是水动力弥散系数（D(L)）。
