Abstract: Under the influence of global climate changes and human activities, the Songnen Plain’s groundwater environment is deteriorating, which becomes an important factor restricting the social economic development and ecological balance. As a relatively independent water system in the Songnen Plain, the groundwater system of the Songhua River provides the main water sources for industry, agriculture, life and other aspects. According to the hydrogeological investigation, groundwater sample collection and testing in the eastern Songnen Plain, descriptive statistics analysis, piper diagram, Gibbs diagram and reverse hydrogeochemical simulation were used to analyze the hydrochemical characteristics and evolution laws of regional groundwater. The results of this study show that HCO3- and Ca2+ are the main anion and cation in the groundwater; the formation of groundwater chemical components are controlled by topographic and geomorphic factors and groundwater occurrence conditions; groundwater subarea of the Lalin-Ashi River is mainly controlled by weathering-dissolution process, and evaporation and ion-exchange reactions are more obvious in groundwater subarea of the Hulan-Tongken River, whose chemical composition also affects the valley plain groundwater subarea in the discharge area; in addition, local high intensity withdrawal causes abnormal hydrochemical evolution processes. The research results can offer scientific basis for rational utilization and protection of groundwater.
Abstract: Based on the basic geology, hydrogeology, engineering geology, geothermal geology and ground source heat pump (GSHP) engineering of the work space, the thesis studies the local shallow geothermal energy. Three conditions of the attribute index for the suitability zoning of the northwest of Shandong are determined, namely, hydrodynamic condition, geological and hydrogeological condition and geological environment condition. The assessment result is that the total area of the suitable zone is 205.88 km2, that of relative suitable zone, 1 407.76 km2, and that of unsuitable zone, 286.8 km2. The result conforms to the real development situation and provides experience for similar regions needed for selecting and assigning a value to suitability zoning of GSHP.
Abstract: The large karst geothermal field of Xiong County, which is located to the south of geothermal field in Niutuozhen, features huge geothermal resources and favorable condition for development and utilization. Because of the long-term extensive production, the pressure of geothermal reservoir continues to decline and some geothermal wells even face the danger of scrapping. To relieve the fall in pressure of geothermal reservoir and achieve the sustainable development and utilization of geothermal field in the long run, reinjection experiment is conducted in the geothermal field of Xiong County and a three-dimensional hydrothermal coupled numerical model was constructed. The reinjection experiment showed that the mode of one production well and one reinjection well can be achieved in this geothermal field. The numerical simulation is used to forecast and compare the change in pressure field and temperature field under different production and reinjection modes and concludes that the most opotimized production and utilization mode is the concentrated production-reinjection mode, and the most opotimized production-reinjection combination mode is the shallow production and shallow reinjection mode which can ensure the sustainable development and utilization of geothermal resources in the long run.
Abstract: BadainJaran Desert of Inner Mongolia is arid and rainless all the year around, with much more evaporation than rainfall. But the special groundwater recharge mechanism contributes to the generation of several lakes of different sizes that have never not dried up for years, among which there are many freshwater lakes. As the research object in this paper, East Badain Lake and West Badain Lake in the southeast of the desert, which are less than 50m away from each other, show the considerable difference in mineralization. In fact, one is a freshwater lake, but the other is a brackish-water lake. Considering the underground aquifer structure of BadainJaran Desert and the special formation structure the particularity of the stratigraphic structure around Badain Lake, the author uses AMT (audio magneto telluric) method and ultra-high density resistivity method to analyze the difference in mineralization of East Badain Lake and West Badain Lake from the perspective of geophysical prospecting methods.
Abstract: Micro-organisms are major components in the environment, which play a key role in groundwater environment. This study aims to investigate the bacterial diversity over time in a typical karst spring named S31 and its response to hydrogeochemical parameters. Quantitative PCR and 16S rRNA high-throughput sequencing was adopted to detect changes of the bacterial community structure. For the correlations between hydrogeochemical parameters and predominant phyla, redundancy analysis were adopted. According to the results, hydrochemical characteristics were controlled by carbonate equilibrium system and dynamic groundwater transformation which was influenced distinctly by precipitation. In addition, the redundancy analysis indicates that HCO3-, Ca2+, Eh, temperature and cumulative precipitation are the most important hydrogeochemical and environmental parameters to determine the bacterial community structures. That is to say, temperature can influence bacterial abundance by controlling dissolved oxygen content. Precipitation is another important factor which determines the community composition and bacterial structure directly or indirectly. Moreover, acidobacteria, proteobacteria, and bacteroidetes play key roles in response to the environmental factors in the groundwater of karst zones.
Abstract: The riverbank soil is a natural purifying agent for the polluted river water (Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and transformation rules of ammonia-nitrogen in three typical types of sand soil using the indoor leaching experiment of soil column, and then makes comparison with the indoor experiment results in combination with the numerical simulation method. The experiment process shows that the change in ammonia-nitrogen concentration goes through three stages including “removal-water saturation-saturation”. As the contents of clay particles in soil sample increase, the removal of ammonia-nitrogen from soil sample will take more time and gain higher ratio. During the removal period, the removal ratio of Column 1, Column 2 and Column 3 averages 68.8% (1-12 d), 74.6% (1-22 d) and 91.1% (1-26 d). The ammonia-nitrogen removal ratio shows no noticeable change as the depth of soil columns varies. But it is found that the ammonia-nitrogen removal ratio is the least of the whole experiment when the soil columns are at the depth of 15 cm. It can be preliminary inferred that the natural purifying performance of soil along the river for ammonia-nitrogen in river water mainly depends on the proportion of fine particles in soil. HYDRUS-1D model is used to simulate this experiment process, analyze the change of the bottom observation holes by time and depth in three columns (the tenth day), and make comparison with the experiment result. The coefficients of determination for fitting curves of Column 1, Column 2 and Column 3 are 0.953, 0.909, 0.882 and 0.955, 0.740, 0.980 separately. Besides, this paper examines the contribution of absorption, mineralization and nitrification in the simulation process. In the early removal stage, mineralization plays a dominant role and the maximum contribution rate of mineralization is 99%. As time goes by, absorption starts to function and gradually assumes a dominant position. In the middle and late removal stage, nitrification in Column 1 and Column 2 makes more contribution than mineralization. So the experiment result of the ammonia-nitrogen concentration is 0.6% and 2.4% lower than that in effluent and the maximum contribution ratio of nitrification is -4.53% and -5.10% respectively when only the function of absorption is considered. The mineralization in Column 1 and Column 2 in the middle and late removal stage still plays a more important role than nitrification. So the experiment result is 1.4% higher than that in effluent and the maximum contribution ratio of nitrification is -2.51% when only the function of absorption is considered. Therefore, absorption, mineralization and nitrification make different contributions during different part of the stage. This means that the natural purifying performance of soil along the river for ammonia-nitrogen in river water not only depends on the proportion of fine particles in soil, but depends on the mineralization and nitrification environment. This can offer some insights into the protection and recovery of groundwater along the riverbank.
Abstract: Water cycle and water quality in the Lake Baiyangdian watershed of the North China Plain have undergone great changes due to over-pumping of groundwater and wastewater discharge. In this paper, hydrogeochemical data was collected to analyze the hydrochemical characteristics and geochemistry evolution of groundwater. The study area was divided into two typical parts. One was in the upstream plain area, where over-pumping had resulted in significant decline of groundwater level; the other one was located in the downstream area near the Fu River and Lake Baiyangdian (Lake BYD region). In addition to the natural weathering of minerals, excessive fertilizer was also a main factor of higher ion concentration in groundwater. According to studies, due to good permeability, these regions were easy to be polluted even with deep groundwater depth. However, upstream shallow groundwater and surface water, including lake water, domestic along with industrial wastewater were all sources of present shallow groundwater in the Lake BYD region. Results indicated that anthropogenic activities rather than minerals much matter to the groundwater in these regions. Particularly, wastewater largely decided the groundwater quality, which suggested that the management and restoration of surface water quality was crucial to groundwater protection.
Abstract: The slope instability and uneven settlement caused by the foundation pit dewatering pose a great threat to the project and surrounding environment. Thus, it is necessary to carry out optimization design of the foundation pit dewatering project. To solve this problem, this paper introduces the simulation-optimization method and establishes the groundwater model based on MODFLOW-2005. The local grid refinement (LGR) technique is employed to achieve the refinement of dewatering area. Under the premise of construction safety, the minimum cost of the project is set as the objective function to solve the optimization problem of foundation pit engineering with GWM-2005. The results show that the optimization with GWM-2005 will be more accurate combined with the LGR model, but the improvement of the optimization is not obvious. It is necessary to choose a suitable local refinement model considering the engineering requirement.