Dense non-aqueous phase liquid source zone architecture and dissolution in saturated porous media
WANG Hui-ting, XU Hong-xia, GUO Qiong-ze, SHI Xiao-qing, SUN Yuan-yuan, WU Ji-chun
State Key Laboratory of Pollution Control and Resource Reuse, Department of Hydrosciences, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China
Abstract：To investigate the migration and dissolution of dense non-aqueous phase liquid (DNAPL) in groundwater, tetrachloroethylene (PCE) was selected as the representative in this study. The migration and distribution process of PCE in a two-dimensional (2-D) sandbox were dynamically monitored by light transmission method, while the PCE dissolution was determined using headspace gas chromatograph. Ethanol flushing was then performed to alter the PCE distribution in the sandbox, and the corresponding changes in source zone architecture and dissolution concentration were analysed. Results showed that the migration of PCE was mainly downwards vertical infiltration, accompanied by lateral spreading caused by capillary force. During the migration process, the changes of the PCE source area and the dissolved concentration were obviously consistent, both of which increased rapidly and then stabilized. Due to the small amount of leakage, 70.7% of the PCE was trapped in the migration path and existent as discontinuous ganglia. Ethanol flushing changed the source zone architecture mainly via solubilization, while it exhibited a weak influence on the spatial distribution of PCE. After being flushed with ethanol, the percentage of ganglia PCE increased to 99.6%, and the GTP value increased from 2.4 to 257. With the increase of ethanol flushing volumes, the PCE source zone area decreased from 100cm2 to 50cm2 and the dissolved concentration decreased from 114mg/L to 12mg/L, and the two showed a good relationship (R2=0.76). In addition, continuous monitoring results showed that in the current study, the source zone architecture and dissolution of PCE could remain stable for a certain period of time (at least 16PVs), regardless of whether it was flushed with ethanol or not.
高存荣,王俊桃.我国69个城市地下水有机污染特征研究[J]. 地球学报, 2011,32(5):581-591. Gao C R, Wang J T. Research on groundwater organic contamination characteristics in 69 cities of China[J]. Aacta Ggeoscientia Sinica, 2011,32(5):581-591.
[2]
刘菲,王苏明,陈鸿汉.欧美地下水有机污染调查评价进展[J]. 地质通报, 2010,29(6):907-917. Liu F, Wang S M, Chen H H. Progress of investigation and evaluation on groundwater organic contaminants in western countries[J]. Geological Bulletin of China, 2010,29(6):907-917.
[3]
张卫,李丽,林匡飞,等.采用筛板塔吹脱模拟处理四氯乙烯污染地下水[J]. 中国环境科学, 2012,32(6):1001-1006. Zhang W, Li L, Lin K F, et al. Air stripping in sieve plate tower for the simulated treatment of the groundwater polluted by perchloroethylene[J]. China Environmental Science, 2012,32(6):1001-1006.
[4]
程洲,吴吉春,徐红霞,等.DNAPL在透镜体及表面活性剂作用下的运移研究[J]. 中国环境科学, 2014,34(11):2888-2896. Chen Z, Wu J C, Xu H X, et al. Investigation of the migration characteristic of DNAPL in aquifer with lenses and under the action of surfactant flushing[J]. China Environmental Science, 2014,34(11):2888-2896.
[5]
Essaid H I, Bekins B A, Cozzarelli I M. Organic contaminant transport and fate in the subsurface:Evolution of knowledge and understanding[J]. Water Resources Research, 2015,51(7):4861-4902.
[6]
Agaoglu B, Copty N K, Scheytt T, et al. Interphase mass transfer between fluids in subsurface formations:A review[J]. Advances in Water Resources, 2015,79:162-194.
[7]
Bob M M, Brooks M C, Mravik S C, et al. A modified light transmission visualization method for DNAPL saturation measurements in 2-D models[J]. Advances in Water Resources, 2008, 31(5):727-742.
[8]
Erning K, Dahmke A, Schäfer D. Simulation of DNAPL infiltration and spreading behaviour in the saturated zone at varying flow velocities and alternating subsurface geometries[J]. Environmental Earth Sciences, 2012,65(4):1119-1131.
[9]
程洲,徐红霞,吴吉春,等.地下水中Tween80对DNAPL运移和分布的影响[J]. 中国环境科学, 2019,39(3):1068-1077. Chen Z, Xu H X, Wu J C, et al. Effects of Tween 80 in groundwater on DNAPL migration and distribution[J]. China Environmental Science, 2019,39(3):1068-1077.
[10]
高燕维,郑菲,施小清,等.基于透射光法探讨水流流速对DNAPL运移分布的影响[J]. 环境科学, 2015,36(7):2532-2539. Gao Y W, Zheng F, SHI X Q, et al. Laboratory investigation of DNAPL migration behavior and distribution at varying flow velocities based on light transmission method[J]. Environmental Science, 2015,36(7):2532-2539.
[11]
郑菲,高燕维,施小清,等.地下水流速及介质非均质性对重非水相流体运移的影响[J]. 水利学报, 2015,46(8):925-933. Zheng F, Gao Y W, SHI X Q, et al. Influence of groundwater flow velocity and geological heterogeneity on DNAPL migration in saturated porous media[J]. Journal of Hydraulic Engineering, 2015, 46(8):925-933.
[12]
Taylor T P, Pennell K D, Abriola L M, et al. Surfactant enhanced recovery of tetrachloroethylene from a porous medium containing low permeability lenses:1. Experimental studies[J]. Journal of Contaminant Hydrology, 2001,48(3/4):325-350.
[13]
O'Carroll D M, Sleep B E. Hot water flushing for immiscible displacement of a viscous NAPL[J]. Journal of Contaminant Hydrology, 2007,91(3):247-266.
[14]
Molnar I L, O'Carroll D M, Gerhard J I. Impact of surfactant-induced wettability alterations on DNAPL invasion in quartz and iron oxide-coated sand systems[J]. Journal of Contaminant Hydrology, 2011, 119(1-4):1-12.
[15]
Wu B, Li H, Du X, et al. Correlation between DNAPL distribution area and dissolved concentration in surfactant enhanced aquifer remediation effluent:A two-dimensional flow cell study[J]. Chemosphere, 2016,144:2142-2149.
[16]
伍斌,杨宾,李慧颖,等.表面活性剂强化抽出处理含水层中DNAPL污染物的去除特征[J]. 环境工程学报, 2014,8(5):1956-1964. Wu B, Yang B, Li H Y, et al. Removal characteristic of DNAPL contaminants in surfactant enhanced aquifer remediation[J]. Chinese Journal of Environmental Engineering, 2014,8(5):1956-1964.
[17]
郑菲,高燕维,孙媛媛,等.污染源区结构特征对Tween 80去除DNAPL效果的影响[J]. 中国环境科学, 2016,36(7):2035-2042. Zheng F, Gao Y W, Sun Y Y, et al. The influence of source-zone architecture on DNAPL removal by Tween 80 flushing[J]. China Environmental Science, 2016,36(7):2035-2042.
[18]
Nambi I M, Powers S E. NAPL dissolution in heterogeneous systems:an experimental investigation in a simple heterogeneous system[J]. Journal of Contaminant Hydrology, 2000,44(2):161-184.
[19]
Difilippo E L, Brusseau M L. Relationship between mass-flux reduction and source-zone mass removal:analysis of field data[J]. Journal of Contaminant Hydrology, 2008,98(1):22-35.
[20]
Page J W, Soga K, Illangasekare T. The significance of heterogeneity on mass flux from DNAPL source zones:an experimental investigation[J]. Journal of Contaminant Hydrology, 2007,94(3):215-234.
[21]
Difilippo E L, Carroll K C, Brusseau M L. Impact of organic-liquid distribution and flow-field heterogeneity on reductions in mass flux[J]. Journal of Contaminant Hydrology, 2010,115(1):14-25.
[22]
李洪,李鑫钢,徐世民,等.饱和区中非水相有机物溶解的实验研究[J]. 化学工程, 2008,36(4):49-52. Li H, Li X G, Xu S M, et al. Experimental study of non-aqueous phase liquids dissolution in saturated zone[J]. Chemical Engineering, 2008,36(4):49-52.
[23]
郭琼泽,张烨,姜蓓蕾,等.表面活性剂增强修复地下水中PCE的砂箱实验及模拟[J]. 中国环境科学, 2018,38(9):200-207. Guo Q Z, Zhang Y, Jiang B L, et al. Experiment and numerical simulation of surfactant-enhanced aquifer remediation in PCE contaminated laboratory sandbox[J]. China Environmental Science, 2018,38(9):200-207.
[24]
Ye S, Sleep B E, Chien C. The impact of methanogenesis on flow and transport in coarse sand[J]. Journal of Contaminant Hydrology, 2009,103(1):48-57.
[25]
Seyedabbasi M A, Farthing M W, Imhoff P T, et al. WITHDRAWN:Influence of porous media heterogeneity on NAPL dissolution fingering and upscaled mass transfer[J]. Water Resources Research, 2013,47(12):W08507.
[26]
Luciano A, Viotti P, Papini M P. Laboratory investigation of DNAPL migration in porous media.[J]. Journal of Hazardous Materials, 2010, 176(1):1006-1017.
[27]
Altiok E, Koos R, Schröder J, et al. Comparison of two-dimensional and three-dimensional imaging techniques for measurement of aortic annulus diameters before transcatheter aortic valve implantation[J]. Heart, 2011,97(19):1578.
[28]
Fagerlund F, Illangasekare T H, Niemi A. Nonaqueous-phase liquid infiltration and immobilization in heterogeneous media:1. Experimental methods and two-layered reference case[J]. Vadose Zone Journal, 2007,6(3):471-482.
[29]
Schroth M H, Istok J D, Ahearn S J, et al. Characterization of miller-similar silica sands for laboratory hydrologic studies[J]. Soil Science Society of America Journal, 1996,60(5):1331-1339.
[30]
Totten C, Annable M, Jawitz J, et al. Fluid and porous media property effects on dense nonaqueous phase liquid migration and contaminant mass flux[J]. Environmental Science & Technology, 2007,41(5):1622.
[31]
Suchomel E J, Pennell K D. Reductions in contaminant mass discharge following partial mass removal from DNAPL source zones[J]. Environmental Science & Technology, 2006,40(19):6110-6116.
[32]
Tick G R, Harvell J R, Murgulet D. Intermediate-scale investigation of enhanced-solubilization agents on the dissolution and removal of a multicomponent dense nonaqueous phase liquid (DNAPL) Source[J]. Water Air & Soil Pollution, 2015,226(11):371.
[33]
Falta R W. Using phase diagrams to predict the performance of cosolvent floods for NAPL remediation[J]. Groundwater Monitoring & Remediation, 1998,18(3):94-102
