-
有机物是化工、石油加工等行业的主要生产原料,渗入土壤中会造成严重地下水污染[1]. 目前,工业活动和意外泄漏导致我国约90%的城市地下水遭受不同程度有机污染,对水质和含水层生态系统造成严重威胁[2 − 3]. 欧洲环境署表示,矿物油等有机污染物是欧洲地下水污染的主要来源[4]. 甲苯和三氯乙烯作为苯系物和氯代烃中的典型污染物,广泛存在于地下水环境中. 地下水中有机污染物的最终归宿受对流弥散、传质作用以及吸附衰减控制[5],地下水环境因素的复杂性,影响其在含水层中分布. 为探究有机污染物迁移的关键影响参数,人们对不同条件下污染物迁移进行了大量实验和模拟研究,静态吸附实验探究了污染物吸附特征及影响因素[6],一维土柱实验侧重于探究污染物沿水流方向迁移规律[7],二维槽试验主要探究二维体系下污染物在对流弥散、吸附等作用下纵向和横向的迁移特征[8]. 但多依赖于室内小试试验,而实际场地污染物发生多维度迁移,导致其迁移规律与实际迁移过程存在较大差异. 为摆脱尺度效应的影响更贴近真实场地,构建多维度大规模试验装置对污染物迁移过程进行测试,三维槽试验比一维和二维实验更能反映污染场地的迁移特征,同时大型试验装置可有效降低边壁效应及数值模拟误差带来的影响,因此有必要创新性的构建大型地下水试验装置进行复合污染物迁移过程模拟,探究影响其迁移性能的关键因素.
数值模拟已成为模拟地下水流动和溶质运移的重要工具,早期地下水模拟多采用电类比法,20世纪60年代逐步过渡为数值法,20世纪70年代以来三维水流模型和有限元法的引入,使相继开发的GMS、Visual MODFLOW、FEFLOW、Visual Groundwater等地下水数值模拟软件飞速发展,并在20世纪90年代末陆续引入我国,后在21世纪初被广泛运用于我国污染物迁移模拟预测、地下水资源管理及风险评估等方面的研究[9]. GUO等[10]利用Visual MODFLOW和MT3DMS探究制革厂污染物的时空分布特征,结果表明受水文地质限制,水中Cr呈现上升后稳定或下降的趋势. Zhao等[11]利用GMS软件模拟垃圾渗滤液的迁移情况,综合评价发现研究区内40%以上的地下水处于高风险区域. 刘玲等[12]利用FEFLOW模型,定量描述污染场地Cr在土壤-地下水中的迁移规律. 在数值模拟过程中,地下水环境的复杂性和不可见性使模型参数具有不确定性,间接导致模拟结果不确定性[13]. 敏感性分析是建立和改进数学模型的重要工具,具有量化不确定性和度量敏感性的功能[14 − 15],反映参数变化对不确定性的影响程度[16 − 18]. 敏感度分析方法可分为局部和全局两类[19]. 局部灵敏性分析是在参数值范围内评价参数灵敏度[20],全局敏感性分析量化所有参数不确定性贡献率[21]. WANG等[22]基于沙箱建立的溶质运移模型,采用局部分析法得到影响迁移的敏感参数大小依次为:弥散度、孔隙度和导水率. SONG等[23]指出全局敏感性分析使模型模拟数据大量输入,具有运行周期长、准确性低等问题,需降低参数维度减少噪声,优化模型计算成本. 张冠儒等[24]将正交试验法用于宝鸡峡灌区,分析表明地表水灌溉量和蒸发量是影响灌区地下水的主要因素. 目前大多地下水数值模型参数间存在耦合关系,只改变单一参数的敏感度可能缺乏代表性和全面性. 模拟研究多参数污染物迁移情况可有效确定关键影响因素,由此提出的正交试验法可有效筛选出全面、均匀、具有代表性的试验组分,以少量模拟迭代得到最优参数,实现复杂模型的优化迭代求解. 正交试验法在实际应用中具有一定可行性,是对传统敏感性分析方法的补充和完善.
基于此为研究污染物迁移的影响因素,本文以甲苯和三氯乙烯为模拟因子,利用GMS软件,结合不同水文地质条件和水动力条件的情景设置,模拟不同情景下污染物迁移过程,分别利用局部分析法和正交试验法评价参数敏感性大小,定量分析各参数变化对污染形态、范围和位置的影响,确定关键影响因素,对分析管理受污染含水层,地下水风险评估及水资源合理利用等有借鉴意义.
基于大型地下水试验装置的复合有机污染物迁移性能关键影响参数研究
Study on the key factors affecting the migration of complex organic pollutants based on a large-scale groundwater test device
-
摘要: 含水层中的复合污染物迁移过程主要受水文地质条件和水动力条件影响,为探究复合污染物迁移的影响因素,基于建设的大型地下水试验模拟装置,以甲苯和三氯乙烯为特征污染物,利用GMS建立了地下水流模型和溶质迁移模型,并设置不同情景,模拟不同水文地质条件和水动力条件影响下复合污染物迁移过程;通过敏感性分析,探究关键因素的影响. 模拟结果表明三氯乙烯迁移能力大于甲苯,模型运行180 d后,甲苯最大迁移距离为3.5 m,而三氯乙烯最大迁移距离超过6.0 m,且甲苯和三氯乙烯迁移距离与渗透系数和弥散度呈线性正相关,与吸附系数呈线性负相关,即迁移距离随渗透系数和弥散度的增大而增大,随吸附系数的增大而减小. 敏感性分析结果表明复合污染物迁移程度的关键影响因素为:渗透系数>弥散度>吸附系数.Abstract: The migration process of complex pollutants in aquifers is mainly affected by hydrogeological and hydrodynamic conditions. In order to explore the factors affecting the migration of complex pollutants, toluene and trichloroethylene were used as characteristic pollutants. Groundwater modeling system (GMS) was adopted to establish the groundwater flow model and solute migration model based on large-scale groundwater test device under different scenarios. Then, the migration process of complex pollutants under the influence of different hydrogeological and hydrodynamic conditions was simulated. Meanwhile, the influence of key factors was explored through sensitivity analysis. The simulation results showed that the migration capacity of trichloroethylene was greater than that of toluene. The maximum migration distance of toluene was 3.5 m, while the maximum migration distance of trichloroethylene was more than 6.0 m after 180 days. The migration distances of toluene and trichloroethylene were linearly positively correlated with the permeability and dispersion coefficients, and linearly negatively correlated with the adsorption coefficient, indicating that the migration distances increase with the increase of permeability and dispersion coefficients, and decrease with the increase of adsorption coefficient. The results of sensitivity analysis showed that the most key factor affecting the migration degree of composite pollutants was permeability coefficient, followed by dispersion and adsorption coefficients.
-
表 1 参数水平值
Table 1. Level values of the parameters
参数
Parameter水平1
Level 1水平2
Level 2对照组
Control group水平3
Level 3水平4
Level 4−20% −10% 0 10% 20% 渗透系数/(m·d−1)
Permeability0.18 0.21 0.23 0.25 0.28 弥散度/m
Dispersity1.20 1.35 1.50 1.65 1.80 吸附系数甲苯/(L·kg−1)
Adsorption48.40 54.45 60.50 66.55 72.60 吸附系数三氯乙烯n /(L·kg−1)
Adsorptio39.68 44.64 49.60 54.56 59.52 表 2 正交试验方案下参数组合情况及指标值
Table 2. Parameter combination and index values under orthogonal test scheme
试验组分
Constituent test渗透系数/
(m·d−1)
Permeability弥散度/m
DispersityKd甲苯/
(L·kg−1)
AdsorptionKf三氯乙烯/
(L·kg−1)
Adsorption甲苯迁移距离/m
Migration
distance指标1
Indicator1三氯乙烯
迁移距离/m
Migration distance指标2
Indicator21 0.18 1.20 48.40 39.70 2.623 0.199 4.151 0.436 2 0.18 1.50 60.50 49.60 2.624 0.198 4.192 0.395 3 0.18 1.80 72.60 59.50 2.625 0.197 4.200 0.387 4 0.23 1.20 60.50 49.60 2.733 0.089 4.289 0.298 5 0.23 1.50 72.60 59.50 2.733 0.089 4.434 0.153 6 0.23 1.80 48.40 39.70 3.109 0.287 4.617 0.030 7 0.28 1.20 72.60 59.50 2.987 0.165 4.878 0.291 8 0.28 1.50 48.40 39.70 3.219 0.397 4.955 0.368 9 0.28 1.80 60.50 49.60 3.231 0.409 4.960 0.373 表 3 影响因素敏感度分析
Table 3. Sensitivity analysis of influencing factors
水平/因素
Level/Factor甲苯
Methylbenzene三氯乙烯
Trichloroethylene渗透系数/(m·d−1)Permeability 弥散度/m Dispersity 吸附系数/(L·kg−1)
Adsorption渗透系数/(m·d−1)Permeability 弥散度/m Dispersity 吸附系数/(L·kg−1)
Adsorption−20% 0.198 0.151 0.294 0.406 0.342 0.278 0% 0.155 0.228 0.232 0.163 0.354 0.355 20% 0.324 0.298 0.15 0.344 0.263 0.277 均方根误差
Root mean square error0.072 0.060 0.059 0.103 0.040 0.037 因素敏感性大小
Factor sensitivity渗透系数>弥散度>吸附系数 渗透系数>弥散度>吸附系数 -
[1] 周美春, 李加鹏, 周杜牧, 等. 复杂有机污染场地地下水风险管控工程效果评估研究——以常州市某污染场地为例[J]. 环境保护科学, 2023, 1(7): 1-10. ZHOU M C, LI J P, ZHOU D M, et al. Effect evaluation of groundwater risk control project in complex organic contaminated site: A case study of a contaminated site in Changzhou[J]. Science of Environmental Protection, 2023, 1(7): 1-10.
[2] LUEDERS T. The ecology of anaerobic degraders of BTEX hydrocarbons in aquifers[J]. FEMS Microbiology Ecology, 2017, 93(1): fiw220. doi: 10.1093/femsec/fiw220 [3] 李笑诺, 陈卫平, 吕斯丹. 国内外污染场地风险管控技术体系与模式研究进展[J]. 土壤学报, 2022, 59(1): 38-53. LI X N, CHEN W P, LÜ S D. Advancement in researches on technical systems and modes for risk management and control of contaminated sites at home and aborad[J]. Acta Pedologica Sinica, 2022, 59(1): 38-53 (in Chinese).
[4] VAN L M H, PROKOP G, RABL-BERGER S, et al. Progress in the management of contaminated sites in Europe[R]. Italy: Joint Research Center of the European Commission, 2014: 3-5. [5] POWERS S E, HUNT C S, HEERMANN S E, et al. The transport and fate of ethanol and BTEX in groundwater contaminated by gasohol[J]. Critical Reviews in Environmental Science and Technology, 2001, 31(1): 79-123. doi: 10.1080/20016491089181 [6] LI Y, WEI M L, LIU L, et al. Adsorption of toluene on various natural soils: Influences of soil properties, mechanisms, and model[J]. Science of the Total Environment, 2020, 740: 140104. doi: 10.1016/j.scitotenv.2020.140104 [7] AKYOL N H, YOLCUBAL I, YÜKSEL D I. Sorption and transport of trichloroethylene in caliche soil[J]. Chemosphere, 2011, 82(6): 809-816. doi: 10.1016/j.chemosphere.2010.11.029 [8] LEE S G, LEE S, CHOI J W. Nonlinear sorption of organic contaminant during two-dimensional transport in saturated sand[J]. Water, 2021, 13(11): 1557. doi: 10.3390/w13111557 [9] 郭晓东, 田辉, 张梅桂, 等. 我国地下水数值模拟软件应用进展[J]. 地下水, 2010, 32(4): 5-7. doi: 10.3969/j.issn.1004-1184.2010.04.002 GUO X D, TIAN H, ZHANG M G, et al. Visual MODFLOW; GMS; FEFLOW application development of groundwater value simulation software in our country[J]. Ground Water, 2010, 32(4): 5-7 (in Chinese). doi: 10.3969/j.issn.1004-1184.2010.04.002
[10] GUO S S, WU H, TIAN Y Q, et al. Migration and fate of characteristic pollutants migration from an abandoned tannery in soil and groundwater by experiment and numerical simulation[J]. Chemosphere, 2021, 271: 129552. doi: 10.1016/j.chemosphere.2021.129552 [11] ZHAO X N, WANG D Q, XU H L, et al. Simulation and prediction of groundwater pollution based on GMS: A case study in Beijing, China[J]. IOP Conference Series:Earth and Environmental Science, 2021, 826(1): 012014. doi: 10.1088/1755-1315/826/1/012014 [12] 刘玲, 陈坚, 牛浩博, 等. 基于FEFLOW的三维土壤-地下水耦合铬污染数值模拟研究[J]. 水文地质工程地质, 2022, 49(1): 164-174. LIU L, CHEN J, NIU H B, et al. Numerical simulation of three-dimensional soil-groundwater coupled chromium contamination based on FEFLOW[J]. Hydrogeology & Engineering Geology, 2022, 49(1): 164-174 (in Chinese).
[13] 束龙仓, 王茂枚, 刘瑞国, 等. 地下水数值模拟中的参数灵敏度分析[J]. 河海大学学报(自然科学版), 2007, 35(5): 491-495. SHU L C, WANG M M, LIU R G, et al. Sensitivity analysis of parameters in numerical simulation of groundwater[J]. Journal of Hohai University (Natural Sciences), 2007, 35(5): 491-495 (in Chinese).
[14] YASEMI M, JOLICOEUR M. Modelling cell metabolism: A review on constraint-based steady-state and kinetic approaches[J]. Processes, 2021, 9(2): 322. doi: 10.3390/pr9020322 [15] 吴吉春, 陆乐. 地下水模拟不确定性分析[J]. 南京大学学报(自然科学版), 2011, 47(3): 227-234. WU J C, LU L. Uncertainty analysis for groundwater modeling[J]. Journal of Nanjing University (Natural Sciences), 2011, 47(3): 227-234 (in Chinese).
[16] STEWART I T, LOAGUE K. A type transfer function approach for regional-scale pesticide leaching assessments[J]. Journal of Environmental Quality, 1999, 28(2): 378-387. [17] CHEN M, IZADY A, ABDALLA O A, et al. A surrogate-based sensitivity quantification and Bayesian inversion of a regional groundwater flow model[J]. Journal of Hydrology, 2018, 557: 826-837. doi: 10.1016/j.jhydrol.2017.12.071 [18] ANDERSON M P, WOESSNER W W, HUNT R J. Applied groundwater modeling: simulation of flow and advective transport[M]. London: Academic press, 2015. [19] DAI H, CHEN X Y, YE M, et al. A geostatistics-informed hierarchical sensitivity analysis method for complex groundwater flow and transport modeling[J]. Water Resources Research, 2017, 53(5): 4327-4343. doi: 10.1002/2016WR019756 [20] ABDELAZIZ R, MERKEL B J. Sensitivity analysis of transport modeling in a fractured gneiss aquifer[J]. Journal of African Earth Sciences, 2015, 103: 121-127. doi: 10.1016/j.jafrearsci.2014.12.003 [21] SHI X Q, YE M, CURTIS G P, et al. Assessment of parametric uncertainty for groundwater reactive transport modeling[J]. Water Resources Research, 2014, 50(5): 4416-4439. doi: 10.1002/2013WR013755 [22] WANG Y, WEI W X, HAN H L, et al. Groundwater migration modeling and parameter sensitivity analysis on contaminated site[J]. Advanced Materials Research, 2014, 878: 775-781. doi: 10.4028/www.scientific.net/AMR.878.775 [23] SONG X M, ZHANG J Y, ZHAN C S, et al. Global sensitivity analysis in hydrological modeling: Review of concepts, methods, theoretical framework, and applications[J]. Journal of Hydrology, 2015, 523: 739-757. doi: 10.1016/j.jhydrol.2015.02.013 [24] 张冠儒, 魏晓妹. 基于变化环境的地下水动态敏感性分析方法研究[J]. 西北农林科技大学学报(自然科学版), 2011, 39(2): 223-228. ZHANG G R, WEI X M. Methods study on sensitivity analysis of groundwater dynamics based on the changing environment[J]. Journal of Northwest A & F University (Natural Science Edition), 2011, 39(2): 223-228 (in Chinese).
[25] APPELO C A J, POSTMA D. Geochemistry, Groundwater and Pollution[M]. Rotterdam: CRC Press, 2004. [26] SCHAFFER M, LICHA T. A framework for assessing the retardation of organic molecules in groundwater: Implications of the species distribution for the sorption-influenced transport[J]. Science of the Total Environment, 2015, 524/525: 187-194. doi: 10.1016/j.scitotenv.2015.04.006 [27] DELLE SITE A. Factors affecting sorption of organic compounds in natural sorbent/water systems and sorption coefficients for selected pollutants. A review[J]. Journal of Physical and Chemical Reference Data, 2001, 30(1): 187-439. doi: 10.1063/1.1347984 [28] 苗胜军, 李长洪, 文俊, 等. 基于正交试验设计的滑带土参数敏感性分析[J]. 中国矿业, 2007, 16(9): 76-79. doi: 10.3969/j.issn.1004-4051.2007.09.024 MIAO S J, LI C H, WEN J, et al. Parameter sensitivity analysis of slip zone based on orthogonal experiment[J]. China Mining Magazine, 2007, 16(9): 76-79 (in Chinese). doi: 10.3969/j.issn.1004-4051.2007.09.024
[29] FAISAL A A H, KUBBA F A, MADHLOOM H M. Modeling of trichloroethylene migration in three-dimensional saturated sandy soil[J]. Arabian Journal for Science and Engineering, 2014, 39(11): 7763-7769. doi: 10.1007/s13369-014-1326-x [30] EL-FARHAN Y H, SCOW K M, DE JONGE L W, et al. Coupling transport and biodegradation of toluene and trichloroethylene in unsaturated soils[J]. Water Resources Research, 1998, 34(3): 437-445. doi: 10.1029/97WR03466 [31] GATEL L, LAUVERNET C, CARLUER N, et al. Global evaluation and sensitivity analysis of a physically based flow and reactive transport model on a laboratory experiment[J]. Environmental Modelling & Software, 2019, 113: 73-83.