巴丹吉林沙漠包氣帶水分過程和鹽分過程數(shù)值模擬
發(fā)布時(shí)間：2018-09-19 17:55
【摘要】：包氣帶的水分運(yùn)移對(duì)地下水補(bǔ)給有直接影響,包氣帶的鹽分運(yùn)移特征可以用于深入研究計(jì)算歷史時(shí)期的入滲補(bǔ)給量情況,這是氯離子質(zhì)量平衡法(CMB)的基礎(chǔ)。本文基于野外土壤水分監(jiān)測(cè)數(shù)據(jù),通過室內(nèi)試驗(yàn)測(cè)定土壤物理性質(zhì)和水力學(xué)參數(shù),采用HYDRUS-1D開展數(shù)值模擬,從不同角度研究巴丹吉林沙漠包氣帶的水分運(yùn)移情況和Cl離子運(yùn)移特征。在巴丹吉林沙漠蘇木吉林湖區(qū)附近不同位置開挖剖面,采用便攜式TDR探頭測(cè)定了不同深度處的含水率,并計(jì)算了土水勢(shì),結(jié)果表明:(1)含水率整體伴隨著深度的增加而增大,其數(shù)據(jù)離散程度與深度呈反比;(2)包氣帶淺表水分運(yùn)動(dòng)方向向上,呈蒸發(fā)狀態(tài),代表了無降水時(shí)期的特征,而深部包氣帶水分向下運(yùn)動(dòng),呈入滲狀態(tài)�；诓煌墨I(xiàn)來源的監(jiān)測(cè)數(shù)據(jù),繪制了巴丹吉林沙漠內(nèi)包氣帶含水率隨深度的變化圖,分析了數(shù)據(jù)的離散特征和總趨勢(shì)。在不受地下水影響的情況下,包氣帶含水率主要在10%以內(nèi)變化,概率密度的峰值含水率為5%,總體上隨著深度增加含水率的離散程度減小,且在深度1 m以下基本呈入滲狀態(tài)。土壤水的長(zhǎng)期監(jiān)測(cè)表明深度1 m處含水率呈現(xiàn)輕微的季節(jié)性波動(dòng),可用一個(gè)周期為1年的正弦函數(shù)進(jìn)行擬合。根據(jù)這個(gè)特征,采用HYDRUS-1D建立深度1m以下、101 m以上的垂向一維非飽和水流模型,設(shè)置上邊界含水率隨時(shí)間正弦周期性變化,模擬不同時(shí)間的含水率分布。發(fā)現(xiàn)含水率的波動(dòng)振幅隨著深度增加而逐漸減小,模型底部的下滲通量很穩(wěn)定,與飽和滲透系數(shù)呈正比。這說明巴丹吉林沙漠地下水的補(bǔ)給可能是非常穩(wěn)定的,而且主要取決于砂層的滲透系數(shù)。根據(jù)前人在巴丹吉林沙漠應(yīng)用CMB法的一些結(jié)果,采用Hydrus-1D模擬深度20 m以內(nèi)包氣帶垂向一維Cl離子運(yùn)移,模擬的最大時(shí)間長(zhǎng)度接近800年。結(jié)果表明初始含水率和鹽分剖面的不確定性主要影響400年以內(nèi)的模擬結(jié)果,隨著彌散度的增大,氯離子濃度隨深度變化的曲線變得越來越平滑,氯離子濃度峰值向下遷移的速率主要受滲透系數(shù)的影響,相比之下分子擴(kuò)散系數(shù)的影響基本可以忽略。這些因素可能是在使用CMB法時(shí)需要考慮的。
[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.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P641
本文編號(hào)：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.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P641
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