基于FEFLOW的三维土壤-地下水耦合铬污染数值模拟研究

刘玲; 陈坚; 牛浩博; 李璐; 殷乐宜; 魏亚强

doi:10.16030/j.cnki.issn.1000-3665.202102008

基于FEFLOW的三维土壤-地下水耦合铬污染数值模拟研究

1.
生态环境部环境规划院/长江经济带生态环境联合研究中心，北京　100012

2.
中国地质大学(北京)水资源与环境学院，北京　100083

3.
上海交通大学环境科学与工程学院，上海　200240

基金项目: 国家自然科学青年基金项目（42107015），国家重点研发计划（2018YFC1800204）

详细信息

作者简介: 刘玲(1991-)，女，硕士，主要从事水文地质与工程地质研究。E-mail：569442022@qq.com

通讯作者: 魏亚强（1990-），男，博士，助理研究员，主要从事地下水数值模拟研究。E-mail：weiyaqiang0000@126.com

中图分类号: X532

收稿日期: 2021-02-05

修回日期: 2021-04-02

刊出日期: 2022-01-15

Numerical simulation of three-dimensional soil-groundwater coupled chromium contamination based on FEFLOW

1.
Center for Ecological Environment in Yangtze River Economic Belt/Chinese Academy of Environmental Planning, Beijing　100012, China

2.
School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing　100083, China

3.
School of Environmental Science and Engineering, Shanghai Jiaotong University, Shanghai　200240, China

More Information

Corresponding author: WEI Yaqiang, weiyaqiang0000@126.com

Received Date: 05 February 2021

Revised Date: 02 April 2021

Publish Date: 15 January 2022

摘要

摘要:
`土壤-地下水耦合数值模拟是定量刻画水流和溶质运移的主要手段。现有大范围场地尺度的研究受到数据采集难度及模拟计算量的限制，多是将土壤和地下水分成两个系统，这种方式不利于模型之间的计算反馈，易出现计算误差，因此将土壤和地下水作为整体系统研究具有重要意义。为精确刻画实际场地土壤-地下水系统中污染物迁移规律，揭示变饱和反应溶质迁移模型的参数敏感性，以某铬污染场地为研究对象，基于现场试验及前人研究所获数据，采用Galerkin有限元法建立三维土壤-地下水模型，定量描述六价铬在土壤-地下水中的迁移规律。在此基础上，通过改变补给条件，研究潜水面在土壤-地下水系统中的波动。并讨论阻滞系数和反应常数对溶质运移的影响。结果表明：在土壤中，污染物最大水平迁移距离为场地东南侧300 m；地下水中污染晕最大分布面积约为1.632 km²；垂向上土壤中的六价铬仅需15.6 h即可下渗至潜水面，第6天贯穿含水层。当潜水面随着补给量变化而波动时，地下水中六价铬会随水流进入土壤，影响土壤中污染分布。对溶质运移参数的讨论显示，当反应常数由0增大至10⁻⁶ s^-1时，迁移出场区边界时地下水中污染物浓度约减少2000 mg/L，较难迁移至涟水河。基于FEFLOW的数值模型，能够解决各系统之间交互性差的问题，提供较为精确的模拟结果。
- 土壤 /
- 地下水 /
- 耦合模拟 /
- 污染物运移 /
- FEFLOW
Abstract:
Soil-groundwater coupled numerical simulation is the main method to quantitatively describe the flow and solute transport in a groundwater system. The existing researches on a large-scale site are limited by the difficulty of data acquisition and the amount of simulation calculation. Most of them divide the soil and groundwater into two systems, and it is of great significance to study the soil and groundwater as a whole system. In order to accurately depict the migration of contaminants in the soil-groundwater system of the actual site and reveal the parameter sensitivity of the variable saturation reaction solute transport model, in this paper, a 3D soil-groundwater model is established by using the Galerkin finite element method to quantitatively describe the migration of hexavalent chromium in soil-groundwater based on the data obtained from field tests and previous studies. The fluctuation of phreatic surface in the soil-groundwater system is studied by changing the recharge conditions. The effects of retardation coefficient and reaction constant on solute transport are discussed. The results show that in the soil, the maximum horizontal migration distance of contaminants is 300 m to the southeast of the site; the maximum distribution area of contamination halo in groundwater is about 1.632 km²; the vertical hexavalent chromium in soil only needs 15.6 h to infiltrate into the phreatic surface, and penetrates through the aquifer in the sixth day. When the groundwater level fluctuates with the change of recharge, hexavalent chromium in groundwater will enter the soil with the water flow, affecting the distribution of contamination in the soil. The discussion of solute transport parameters shows that when the reaction constant increases from 0 to 10^-6s^-1, the concentration of the contaminants in groundwater decreases by about 2000 mg/L at the boundary of the migration site, which makes it difficult to migrate to the Lianshui River. The numerical model based on FEFLOW can solve the problem of poor interaction between systems and provide more accurate simulation results.
- soil /
- groundwater /
- coupling simulation /
- contaminants transport /
- FEFLOW

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图 1 研究区位置图

Figure 1.

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图 2 研究区水文地质平面图（本图来源为全国地质资料馆1∶20万水文地质图G4902幅）

Figure 2.

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图 3 场地水文地质剖面图

Figure 3.

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图 4 研究区模拟流场图与实际流场图

Figure 4.

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图 5 模拟值与实际值拟合图

Figure 5.

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图 6 初始污染羽分布图

Figure 6.

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图 7 土壤中（第三层）六价铬的运移模拟预测结果

Figure 7.

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图 8 地下水六价铬运移模拟预测结果

Figure 8.

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图 9 污染物迁移至涟水河时污染羽三维分布图

Figure 9.

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图 10 场地六价铬垂向浓度模拟结果

Figure 10.

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图 11 雨季后土壤中污染物浓度变化

Figure 11.

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图 12 不同阻滞系数下场区至河流浓度随距离的变化

Figure 12.

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图 13 不同阻滞系数河岸处观测点浓度随时间的变化

Figure 13.

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图 14 不同反应常数下场区至河流浓度随距离的变化

Figure 14.

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图 15 不同反应常数河岸处观测点浓度随时间的变化

Figure 15.

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表 1 六价铬检测结果

Table 1. Statistics of soil test results

层位	标准限值/(mg·L⁻¹)	分析总数/个	超标个数/个	超标率/%	最大值/(mg·L⁻¹)	最小值/(mg·L⁻¹)	平均值/(mg·L⁻¹)	相对偏差/%
上层土壤	30	203	29	14.3	3410	<1.0	283	733
下层土壤	30	94	17	18.1	3430	<1.0	414	876
地下水	0.1	45	23	51.1	109	<0.01	21.2	30.6

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表 2 研究区水文地质参数取值表

Table 2. Values of hydrogeological parameters in the study area

参数	非饱和区			饱和区
参数	第一亚层	第二亚层	第二层	第三层	第四层	第五层
K_xx/（m·d⁻¹）	0.0864	0.0864	0.1	1	33	4
K_yy/（m·d⁻¹）	0.0864	0.0864	0.1	1	33	4
K_zz/（m·d⁻¹）	0.0864	0.0864	0.01	0.1	3.3	0.4
孔隙度	0.5	0.1	0.05	0.1	0.3	0.1
最大饱和度	1	1	1	/	/	/
剩余饱和度	0.12	0.12	0.12	/	/	/
/m⁻¹	1.2	1.2	1.2	/	/	/
n	3	3	3	/	/	/

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表 3 溶质运移模型参数取值表

Table 3. Parameter values of the solute transport model

参数	非饱和区			饱和区
参数	第一亚层	第二亚层	第二层	第三层	第四层	第五层
弥散系数/ （10⁻⁹m²·s⁻¹）	200	200	200	2300	2300	2300
纵向弥散度/m	1	1	1	100	100	100
横向弥散度/m	0.2	0.2	0.2	20	20	20
阻滞系数	0.1	0.1	0.1	0.01	0.01	0.01
反应系数/ （10⁻⁴·s⁻¹）	0.0016	0.0016	0.0016	0.0016	0.0016	0.0016

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表 4 污染晕面积表

Table 4. Contaminant halo area

时间/d	面积/km²	时间/d	面积/km²
100	0.831	1100	1.416
200	1.030	1200	1.350
300	1.246	1300	1.255
400	1.321	1400	1.055
500	1.413	1500	0.876
600	1.478	1600	0.601
700	1.569	1700	0.376
800	1.596	1800	0.241
917	1.632	1900	0.0018
1000	1.465	2000	0.0014

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