Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China; Laboratory of Soil Physics and Soil Hydrology, Department of Biological and Environmental Engineering, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan.
Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China.
J Environ Sci (China). 2018 Feb;64:197-206. doi: 10.1016/j.jes.2017.06.006. Epub 2017 Jun 23.
Soil contamination by diesel has been often reported as a result of accidental spillage, leakage and inappropriate use. Surfactant-enhanced soil flushing is a common remediation technique for soils contaminated by hydrophobic organic chemicals. In this study, soil flushing with linear alkylbenzene sulfonates (LAS, an anionic surfactant) was conducted for intact columns (15cm in diameter and 12cm in length) of diesel-contaminated farmland purple soil aged for one year in the field. Dynamics of colloid concentration in column outflow during flushing, diesel removal rate and resulting soil macroporosity change by flushing were analyzed. Removal rate of n-alkanes (representing the diesel) varied with the depth of the topsoil in the range of 14%-96% while the n-alkanes present at low concentrations in the subsoil were completely removed by LAS-enhanced flushing. Much higher colloid concentrations and larger colloid sizes were observed during LAS flushing in column outflow compared to water flushing. The X-ray micro-computed tomography analysis of flushed and unflushed soil cores showed that the proportion of fine macropores (30-250μm in diameter) was reduced significantly by LAS flushing treatment. This phenomenon can be attributed to enhanced clogging of fine macropores by colloids which exhibited higher concentration due to better dispersion by LAS. It can be inferred from this study that the application of LAS-enhanced flushing technique in the purple soil region should be cautious regarding the possibility of rapid colloid-associated contaminant transport via preferential pathways in the subsurface and the clogging of water-conducting soil pores.
土壤受到柴油污染通常是由于意外溢出、泄漏和不当使用造成的。表面活性剂强化土壤冲洗是一种常见的修复技术，用于修复受疏水性有机化学品污染的土壤。本研究采用直链烷基苯磺酸盐（LAS，一种阴离子表面活性剂）对农田紫土进行了原位土柱（直径 15cm，长 12cm）冲洗实验，该紫土在田间老化一年后受到柴油污染。分析了冲洗过程中柱出流中胶体浓度、柴油去除率和冲洗引起的土壤大孔结构变化的动力学。正构烷烃（代表柴油）的去除率随表土深度的变化范围为 14%-96%，而亚表层中浓度较低的正构烷烃则被 LAS 强化冲洗完全去除。LAS 冲洗过程中，柱出流中的胶体浓度和胶体粒径明显高于水冲洗。冲洗和未冲洗土芯的 X 射线微计算机断层扫描分析表明，LAS 冲洗处理显著降低了细大孔（直径 30-250μm）的比例。这种现象可归因于胶体的增强堵塞，由于 LAS 更好的分散作用，胶体浓度增加。由此可以推断，在紫色土地区应用 LAS 强化冲洗技术时，应注意胶体相关污染物通过地下优先途径快速迁移和导水土壤孔隙堵塞的可能性。
