| Because of the special surface-subsurface double layer geological structure in karst regions which results in rich groundwater and poor surface water. Therefore, groundwater in karst area is the most important water resorce. With the process of urbanization, urban sewage, garbage and agricultural production had become a serious problem that the southwest region faced. Laolongdong underground river in Chongqing was a typical example that polluted by garbage contaminnations. There was no perfect treatment facilities, garbage disposal facilities for sewage. The waste disposal was basically difficult to deal with but the original ways that drained through the shade and culvert emissions, even the direct discharge, finally which all through the sinkholes into the underground river. Scholars tried their best to study the relevant physical and chemical processes for the underground water affected by the human activities:most of them focus on physical and chemical processes of karst groundwater environment but the reserach of microbial contamination of groundwater in karst area was relevant weak. However karst groundwater the amount of microorganisms in different space and the different seasons may reflect human activities and urban degree. To investigate the mechanism of the process of urbanization in the evolution of the groundwater environment, microorganisms temporal variation of karst water was particularly important to provide a scientific basis for the rational and efficient use of the karst groundwater. what was more, it was important to keep watershed health and disease prevention for karst groundwater resources. Therefore, the impact of urbanization and strategic research of karst groundwater system of urban water resources and sustainable use of living people is of great significance to improve the environment. This study selected Laolongdong basin groundwater in Chongqing as the sample resources for the study, We collected samples and laboratory analysis in 2014.1～2015.1.Sampling points were:Xiaoyuaner, Xiannvdong, Longjingbang, Gaodongsil, Gaodongsi2, Laolongdong underground water, Zhaojiayuanzi, Which was called for short 1#-8#. The samples were collected between one hydrological year. We detected physical and chemical properties of the groundwater. Four kinds of faecal indicator bacteria:Total coliform, Escherich coliform, Fecal coliform, Fecal streptococci were counted with method of filter method. With the help of the correlation analysis of faecal indicator bacterias to get the characteristics of groundwater temporal distribution. For the last we obtained the following conclusions:1. The chemical composition type of the groundwater basin was Ca-Mg-SO4. The 8 sampling points water has generally higher hardness, among them 1#,2,#,4#,8# groundwater were hard water; 3#,5#,6#,7# groundwater belonged to the moderately hard water. K+, Na+ content in each sample point are showing a high level, and K+ exceed natural levels below K+, Na+ content, which with its surface intensity of human activities have a greater relationship. Rapid urbanization upstream region 1#,2#,3# and mixed polluted 7#,8# of K+, Na+ content than agricultural production activities mainly 4#,5#,6#; however, K+, Na+ in the wet season and the dry season the difference is small; SO42-, Cl- concentrations rarely exceed the national standard number, SO42- detection rate was 3%, while Cl- is not detected. In this respect, the Laolongdong undergroundwater as a remediation project whose outcome is still effective. However, nitrate contamination in groundwater is high, the detection rate of 75%.2. Four fecal indicator bacteria karst groundwater environment had important indication significance. They showed different seasonal characters in the distribution of the number of seasons.The number of FIB showed high value in summer and fall, but they were low in winter and spring. But each sampling point microbial indicator bacteria seasonal changes had their own characters.They were different from the FIB in the river and ocean which had stable and similar seasonal changes. Karst groundwater temperature kept constant, there was no big change with the seasons moving, so the groundwater temperature was not the main reason of karst groundwater microbial seasonal variation. For this seasonal variation can be called artificial nature of seasonal changes,Laolongdong district,Chongqing, due to the unique terrain features, the sampling points were located in low-lying valley, while the surrounding clouds with residential and small handicraft workshops and factories, which produceed domestic sewage and industrial wastewater directly discharged into the environment, and the May to October rainy season, precipitation will push sewage into the bottom, finally passed sinkholes into the underground river. This removal process a large number of fecal contamination slack, making groundwater surge in the number of fecal contamination indicator bacteria.3. The groundwater in the study area of fecal indicator microorganism distribution was different, they were influenced by seasonal. Among them, all the sampling points of the fecal pollution degree was high, TC of 7# was the most serious polluted among them, the TC value of 7# more than the national groundwater standard 3.76×102～2.92×106 times. The 5# pollution level was the lowest among the sampling points, but it was still the 22.5～1.57×104 times than national groundwater standard. Microbial contamination level showed:7#>3#>1#>6#>2#>4#>5# The level of TC in 7# was the most serious whose level reached 1.5×107CFU/mL, was much high than the rules 1.0×107CFU/mL. The number of EC was 1.4×105 CFU/mL,7# belongs to severe pollution area. Four kinds of FIB in 5# were low,5# was surrounded by the farmland, mainly engaged in farming, irrigation and other production activities, there were few residents near the sewage,the groundwater quality was the best among the 8 points.1#,3# were located in the upstream of the watershed area.With the city development, which were affected by human activities. TC level was relatively high, second only to 7#. The surface environment of 4#, 6#,8# were agricultural production activities, near the land, the water was mainly used for thg: irrigation, washing clothes and other residents.4. Through the FC/FS we can concluded sources of pollution:At wet period,1#,2#,3# FC/FS ratio reached 103 or more, can be speculated that these three points of groundwater pollution comes mainly from waste of human life; 7# and 8# fecal contamination of groundwater hydrology in a year full display for human fecal contamination, may be due to these two groundwater from multiple branches within the underground river basin, flow with many regions had been part of residential, and industrial areas, where the overwhelming majority of human sewage. The FC/FS in 4# and 5# in the fall was greater than 4.0, the fecal contamination of water sources and human life, but the ratio was clearly less than the value of several other sampling points, that human life was significantly less than the amount of sewage each other sampling point, probably due to a 5# was located in east of agricultural production areas, feeding more livestock, animal produced more feces than that in 1#, 2#,3#.5. Because of the unique karst structure, the connectivity was in vertical direction was larger than the horizontal direction. The surface environment of sampling points had important implications for microbial contamination. Short-term precipitation and surface condition of human activity would led to microbial change of sampling points. There were significant difference in every sampling points and different seasons for chemical characteristics. This was mainly associated with the precipitation and human activity intensity.In summary, it was complex to answer the question that the reason of microbialcontamination: special surface-subsurface double layer geological structure; nutrient salts from agricultural activities contributed to the growth and prosperity of microorganisms in the groundwater; with the urbanization, the resident in the rural-urban continuum became more and more, at the same time the source of contamination of microorganisms in groundwater was increasing.Human sewage pollution was the main mass, the degree of microbial contamination of groundwater and the influence of urbanization was much higher than that of the agricultural production activities as the main source of pollution of groundwater. |
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