巴丹吉林沙漠包气带水分过程和盐分过程数值模拟
发布时间：2018-09-19 17:55
【摘要】：包气带的水分运移对地下水补给有直接影响,包气带的盐分运移特征可以用于深入研究计算历史时期的入渗补给量情况,这是氯离子质量平衡法(CMB)的基础。本文基于野外土壤水分监测数据,通过室内试验测定土壤物理性质和水力学参数,采用HYDRUS-1D开展数值模拟,从不同角度研究巴丹吉林沙漠包气带的水分运移情况和Cl离子运移特征。在巴丹吉林沙漠苏木吉林湖区附近不同位置开挖剖面,采用便携式TDR探头测定了不同深度处的含水率,并计算了土水势,结果表明:(1)含水率整体伴随着深度的增加而增大,其数据离散程度与深度呈反比;(2)包气带浅表水分运动方向向上,呈蒸发状态,代表了无降水时期的特征,而深部包气带水分向下运动,呈入渗状态。基于不同文献来源的监测数据,绘制了巴丹吉林沙漠内包气带含水率随深度的变化图,分析了数据的离散特征和总趋势。在不受地下水影响的情况下,包气带含水率主要在10%以内变化,概率密度的峰值含水率为5%,总体上随着深度增加含水率的离散程度减小,且在深度1 m以下基本呈入渗状态。土壤水的长期监测表明深度1 m处含水率呈现轻微的季节性波动,可用一个周期为1年的正弦函数进行拟合。根据这个特征,采用HYDRUS-1D建立深度1m以下、101 m以上的垂向一维非饱和水流模型,设置上边界含水率随时间正弦周期性变化,模拟不同时间的含水率分布。发现含水率的波动振幅随着深度增加而逐渐减小,模型底部的下渗通量很稳定,与饱和渗透系数呈正比。这说明巴丹吉林沙漠地下水的补给可能是非常稳定的,而且主要取决于砂层的渗透系数。根据前人在巴丹吉林沙漠应用CMB法的一些结果,采用Hydrus-1D模拟深度20 m以内包气带垂向一维Cl离子运移,模拟的最大时间长度接近800年。结果表明初始含水率和盐分剖面的不确定性主要影响400年以内的模拟结果,随着弥散度的增大,氯离子浓度随深度变化的曲线变得越来越平滑,氯离子浓度峰值向下迁移的速率主要受渗透系数的影响,相比之下分子扩散系数的影响基本可以忽略。这些因素可能是在使用CMB法时需要考虑的。
[Abstract]:The water migration of the aerated zone has a direct effect on groundwater recharge. The salt migration characteristics of the aerated zone can be used to further study and calculate the infiltration recharge in the historical period, which is the basis of the chlorine ion mass balance method (CMB). Based on the monitoring data of soil moisture in the field, the physical properties and hydraulic parameters of the soil were measured through laboratory experiments, and the numerical simulation was carried out by HYDRUS-1D. The water migration and Cl ion transport characteristics in the aeration zone of Badain Jilin Desert were studied from different angles. In the excavation section near Jiangsu Jilin Lake region in Badain Jilin Desert, the water content at different depths was measured by portable TDR probe, and the soil water potential was calculated. The results show that: (1) the water content increases with the increase of depth. The dispersion of the data is inversely proportional to the depth; (2) the superficial water movement in the aeration zone is upward, which represents the characteristics of the non-precipitation period, while the water in the deep aeration zone moves downward and in the infiltration state. Based on the monitoring data from different literature sources, the variation of water content in the aeration zone with depth in Badain Jilin desert was plotted, and the discrete characteristics and general trend of the data were analyzed. Without the influence of groundwater, the moisture content of the aeration zone mainly changes within 10%, and the peak water content of probability density is 5. The dispersion degree of water content decreases with the increase of depth, and the water content of the aerated zone is in the state of infiltration under the depth of 1 m. The long-term monitoring of soil water shows that the water content shows a slight seasonal fluctuation at depth of 1 m, which can be fitted by a sinusoidal function with a period of one year. According to this characteristic, a vertical one-dimensional unsaturated flow model with a depth of more than 101m below 1m is established by using HYDRUS-1D. The distribution of water content at different times is simulated by setting up the water content of the upper boundary changing periodically with time. It is found that the fluctuation amplitude of water content decreases gradually with the increase of depth, and the permeation flux at the bottom of the model is very stable, which is directly proportional to the saturation permeability coefficient. This indicates that groundwater recharge in Badain Jilin Desert may be very stable and mainly depends on the permeability coefficient of sand bed. According to the results of CMB method applied by predecessors in Badain Jilin Desert, the vertical one-dimensional Cl ion migration in the aeration zone within 20 m depth was simulated by Hydrus-1D, and the maximum time length of the simulation was nearly 800 years. The results show that the uncertainty of initial water content and salt profile mainly affects the simulation results within 400 years. With the increase of dispersion, the curve of chloride concentration changing with depth becomes more and more smooth. The downward migration rate of the peak concentration of chloride ion is mainly affected by the permeation coefficient, while the influence of the molecular diffusion coefficient can be neglected. These factors may need to be taken into account when using the CMB method.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P641
本文编号：2250891
[Abstract]:The water migration of the aerated zone has a direct effect on groundwater recharge. The salt migration characteristics of the aerated zone can be used to further study and calculate the infiltration recharge in the historical period, which is the basis of the chlorine ion mass balance method (CMB). Based on the monitoring data of soil moisture in the field, the physical properties and hydraulic parameters of the soil were measured through laboratory experiments, and the numerical simulation was carried out by HYDRUS-1D. The water migration and Cl ion transport characteristics in the aeration zone of Badain Jilin Desert were studied from different angles. In the excavation section near Jiangsu Jilin Lake region in Badain Jilin Desert, the water content at different depths was measured by portable TDR probe, and the soil water potential was calculated. The results show that: (1) the water content increases with the increase of depth. The dispersion of the data is inversely proportional to the depth; (2) the superficial water movement in the aeration zone is upward, which represents the characteristics of the non-precipitation period, while the water in the deep aeration zone moves downward and in the infiltration state. Based on the monitoring data from different literature sources, the variation of water content in the aeration zone with depth in Badain Jilin desert was plotted, and the discrete characteristics and general trend of the data were analyzed. Without the influence of groundwater, the moisture content of the aeration zone mainly changes within 10%, and the peak water content of probability density is 5. The dispersion degree of water content decreases with the increase of depth, and the water content of the aerated zone is in the state of infiltration under the depth of 1 m. The long-term monitoring of soil water shows that the water content shows a slight seasonal fluctuation at depth of 1 m, which can be fitted by a sinusoidal function with a period of one year. According to this characteristic, a vertical one-dimensional unsaturated flow model with a depth of more than 101m below 1m is established by using HYDRUS-1D. The distribution of water content at different times is simulated by setting up the water content of the upper boundary changing periodically with time. It is found that the fluctuation amplitude of water content decreases gradually with the increase of depth, and the permeation flux at the bottom of the model is very stable, which is directly proportional to the saturation permeability coefficient. This indicates that groundwater recharge in Badain Jilin Desert may be very stable and mainly depends on the permeability coefficient of sand bed. According to the results of CMB method applied by predecessors in Badain Jilin Desert, the vertical one-dimensional Cl ion migration in the aeration zone within 20 m depth was simulated by Hydrus-1D, and the maximum time length of the simulation was nearly 800 years. The results show that the uncertainty of initial water content and salt profile mainly affects the simulation results within 400 years. With the increase of dispersion, the curve of chloride concentration changing with depth becomes more and more smooth. The downward migration rate of the peak concentration of chloride ion is mainly affected by the permeation coefficient, while the influence of the molecular diffusion coefficient can be neglected. These factors may need to be taken into account when using the CMB method.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P641
【参考文献】
相关期刊论文 前3条
1 张虎才;明庆忠;;中国西北极端干旱区水文与湖泊演化及其巴丹吉林沙漠大型沙丘的形成[J];地球科学进展;2006年05期
2 杨艳;王全九;;微咸水入渗条件下碱土和盐土水盐运移特征分析[J];水土保持学报;2008年01期
3 马金珠,李丁,李相虎,Edmunds W M;巴丹吉林沙漠包气带Cl~-示踪与气候记录研究[J];中国沙漠;2004年06期
相关硕士学位论文 前2条
1 邓臣;垃圾填埋场邻苯二甲酸酯在包气带中迁移的模拟研究[D];广州大学;2011年
2 刘进庆;一维溶质运移中的反问题[D];山东理工大学;2007年
，本文编号：2250891
本文链接：https://www.wllwen.com/kejilunwen/diqiudizhi/2250891.html
