Xie Haijian, Chen Yunmin, Ke Han, Tang Xiaowu, Chen Renpeng
MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou 310027, China.
J Environ Sci (China). 2009;21(4):552-60. doi: 10.1016/s1001-0742(08)62307-4.
The equivalence between multilayered barriers regarding diffusion and adsorption was studied. The bottom boundary of the liner system is defined by assuming concentration continuous and flux continuous conditions of the contaminant between the bottom liner layer and the underlying soil. Five different liner systems were compared in terms of solute breakthrough time. The results of the analysis showed that breakthrough time of the hydrophobic organic compounds for a 2-meter-thick compacted clay liner (CCL) could be 3-4 orders of magnitude is greater than the breakthrough time for a geosynthetic clay liner (GCL) composite liner. The GM/GCL and GM/CCL composite liner systems provide a better diffusion barrier for the hydrophilic organic compounds than that for the hydrophobic compounds due to their different Henry's coefficient. The calculated breakthrough times of the organic contaminants for the Chinese standard liner systems were found to be generally greater than those for the GCL alternatives, for the specific conditions examined. If the distribution coefficient increases to 2.8 for the hydrophobic compounds or 1.0 for the hydrophilic compounds, the thickness of the attenuation layer needed to achieve the same breakthrough time as the standard liner systems can be reduced by a factor of about 1.9-2.4. As far as diffusive and adsorption contaminant transport are concerned, GM or GCL is less effective than CCL.
研究了多层屏障在扩散和吸附方面的等效性。通过假设底部衬垫层与下层土壤之间污染物的浓度连续和通量连续条件来定义衬垫系统的底部边界。从溶质穿透时间方面比较了五种不同的衬垫系统。分析结果表明，对于2米厚的压实粘土层（CCL），疏水性有机化合物的穿透时间可能比土工合成粘土衬垫（GCL）复合衬垫的穿透时间大3 - 4个数量级。由于亨利系数不同，GM/GCL和GM/CCL复合衬垫系统对亲水性有机化合物提供的扩散屏障比对疏水性化合物的更好。在所研究的特定条件下，发现中国标准衬垫系统中有机污染物的计算穿透时间通常大于GCL替代系统的穿透时间。如果疏水性化合物的分配系数增加到2.8或亲水性化合物的分配系数增加到1.0，要达到与标准衬垫系统相同的穿透时间所需的衰减层厚度可减少约1.9 - 2.4倍。就扩散和吸附性污染物传输而言，GM或GCL的效果不如CCL。
