ABSTRACT
As an important water supply source in Beijingï¼ karst groundwater has played an irreplaceable role in the security of urban water supply and ecological environment protection in the past 70 years. The Xishan karst groundwater systemï¼ located in the upper reaches of western Beijingï¼ belongs to ecological conservation areas. There are several centralized water supply fields in this area. In this studyï¼ the Xishan karst groundwater system was taken as the research object. A total of 120 karst groundwater samples in this area were investigated by using statistical analysisï¼ ion ratioï¼ and principal component analysis ï¼PCAï¼ methods to explore the spatial distribution characteristics and formation mechanism of groundwater hydrochemistry. The research results showed thatï¼ â the groundwater quality of the Xishan system was generally goodï¼ with the characteristics of neutral pH and low salinity. A total of 84.17% of the water samples were classified as hard water. The chemical type of groundwater was mainly HCO3-Ca·Mg. â¡ The chemical composition of groundwater was mainly affected by the water-rock interactionï¼ and the weathering source of rock was mainly the dissolution of carbonate. ⢠The results of principal component analysis showed that 34.41% of the chemistry formation of groundwater could be explained by carbonate dissolutionï¼ 27.33% by rock salt and evaporate dissolutionï¼ 11.76% by aquifer sediment dissolutionï¼ and 10.30% by domestic sewage discharge. From the recharge area to the runoff area and then to the discharge areaï¼ the TH and TDS gradually increased. Coal mining drainage and human activities were the main factors that caused groundwater degradation and variable hydrochemical types in the piedmont. In the futureï¼ it is necessary to further strengthen environmental governanceï¼ control point and non-point source pollutionï¼ and continuously monitor key areas to provide scientific support for ecological and environmental protection.
ABSTRACT
In order to evaluate the groundwater quality of Tongzhou area in Beijing Plain and to discuss the characteristics of its distribution by the view of hydrochemistry, a total of 151 groundwater samples, collected within study area in the dry period of 2008 according to the geological and hydrogeololgical condition of Tongzhou area, were classified as shallow, middle and deep groundwater, respectively. Based on the data, the groundwater quality was evaluated by the method of F value. The mean and variance of main chemical constituents of groundwater samples were presented. Almost all the quaternary groundwater of Chaobai river pluvial fan belonged to the alkaline water type. The evaluation results based on the analysis results showed that from shallow to deep, the quality of groundwater in Beijing became better. The total areas of groundwater belonging to class IV and V area were 884 km2, 599 km2 and 94 km2 respectively for shallow, middle and deep groundwater. The evaluation results showed that the main exceeding chemical constituents were TDS, hardness, NH4(+), F(-) and total Fe. Most exceeding samples belonged to middle and deep aquifers. The main types of shallow groundwater were HCO2-Ca x Mg- and HCO3 x Cl-Ca x Na x Mg, while the chemical types of mid-deep groundwater were mostly HCO3-Na x Ca- and HCO3 x SO4(2-) -Na x Ca type due to the increased Na(+), SO4(2-) and Cl(-) concentration. Study results showed that the quality of shallow groundwater became worse mainly due to human activities. The deterioration of groundwater quality in mid-deep aquifers was due to both human activities and natural occurrence of poor-quality water.
Subject(s)
Environmental Monitoring , Groundwater/chemistry , Water Pollutants, Chemical/analysis , Water Quality , China , Water SupplyABSTRACT
Firstly, advances in investigation and evaluation of groundwater pollution in China in the last decade were presented, and several issues in the field which hinder the development of groundwater environment were pointed out. Then, four key concepts in risk assessment of groundwater pollution were briefly described with more emphasis on the difference between groundwater pollution assessment and groundwater quality assessment in this paper. After that, a method on risk assessment of groundwater pollution which included four indicators, the pollution assessment, the quality assessment, the vulnerability and the pollution load of groundwater, was presented based on the regional characteristics of Beijing Plain. Also, AHP and expert scoring method were applied to determine the weight of the four evaluation factors. Finally, the application of this method in Beijing Plain showed the area with high, relative high, medium, relative low and low risk of groundwater contamination was 1 232.1 km2, 699.3 km2, 1 951.4 km, 2 644 km2, and 133.2 km2, respectively. The study results showed that the higher risk in the western region was likely caused by the higher pollution load and its higher vulnerability, while the relatively high risk in the southeast of Beijing plain area, the Tongzhou District, is mainly caused by historical pollution sources.
