Surfactant-enhanced flushing enhances colloid transport and alters macroporosity in diesel-contaminated soil  

作　　者：Zhuo Guan Xiang-Yu Tang Taku Nishimura Hidetaka Katou Hui-Yun Liu Jing Qing 

机构地区：[1]Key Laboratory of Mountain Surface Processes and Ecological Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China [2]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 [3]Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, Tsukuba 305-8604, Japan [4]University of Chinese Academy of Sciences, Beijing 100049, China [5]Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu 611756, China

出　　处：《Journal of Environmental Sciences》2018年第2期197-206,共10页环境科学学报（英文版）

基　　金：supported by Japan Society for the Promotion of Science(RONPAKU Program,No.CAS-11313);the National Key Research and Development Plan of China(No.2016YFD0800203);the National Natural Science Foundation of China(Nos.21307152 and 41471268)

摘　　要：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（15 cm in diameter and 12 cm 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（30–250 μm 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.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（15 cm in diameter and 12 cm 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（30–250 μm 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.

关 键 词：Surfactant-enhanced flushing DIESEL Colloid transport MACROPORES Pore structure 

分 类 号：X53[环境科学与工程—环境工程]