| The karstification is a special geological processes that occurred on the earth surface environment process,which has the characteristics such as open sensitivity, fragile features, biological participation and diversity.The dynamic process of epikarst area is very active,which is susceptible to the change of environment and human activities.The epikarst spring plays an important part in the epi-karst hydrogeological system,which is significant to research the susceptivity of the change of environment and carbon cycle.The study area of this thesis aimed at Shuifang Spring Area in Jinfo Mountain,which is located at Nanchuan in Chongqing, China.We analysed climatic features,rainfall,water chemistry characteristics, soil physical and chemical characteristics and the standard limestone tablets in a whole hydrological year of this area. we hace the several conclusions of the sensitivity of the epikarst water chemical characteristics for environment and carbon sink effection:Firstly,the human activities, rainfall and the temperature have an obviously effect on the changing of pH and EC. During the National Day periods (1-7th October) and the May Holidays(1-7th May), the water ions variations mainly were influenced by rainfall and human activities, while in the Snow Festival period (December, January and February), with the less rainfall and low temperature,the ions changes mainly were influenced by human activities. During the summer of2010, the concentrations of ions are considerably higher than those in the other periods due to the effect of concentration Ca2+, HCO3--, SIc and Pco2are mainly influenced by the temperature, rainfall and human activities in different periods. Most of the CO2in spring water originate from soil CO2from the deep soil profile and participated in the Karst process.Secondly, there is obvious correlation between Ca2+, HCO3-and water temperature in short time scale, but the concentration in night is less than those in the day.,which is mainly csused by aquatic organisms. The flux impacted the changeof the spring EC obviously. The moer flux, the less dilution concentration of ions in the spring,and lead to he EC lower.Thirdly,the karst processes erosion rate is quite different in different land use types,seasons and depth of soil. The maximum dissolution quantities(378.0853mg/m2·d) appeared under10cm of forestland in summer,and the minimum(68.8064mg/m2·d)was found under10cm of shrub land in winter.The soil organic matter and pH affect the dissolution rate of arbonate together.,which there is higher corrosional rate under the conditions of higher soil organism contention and lower pH values.With the increasing of the soil depth,the soil organic content is decline, which the maximum of the soil organic content is15.11g/kg under10cm of shrub land, and the minimum is2.64g/kg under50cm of forestland. The soil pH varied with the increase of soil depth.That is, soil acidity became stronger when it approach to surface.In the same land use type and the different depth of the soil, the CO2concentration and soil temperature shows:20cm<35cm<50cm.The soil CO2emission from soil are affected mainly by the soil temperature. The soil CO2changes and the temperature are similar under different soil depths. The soil CO2concentration is quite susceptivity with temperature and rainfall. No matter it is spring or winter, the water temperature, HCO3, Ca2+, pH, SIc and PCO2showed the lowest content and the maximum dissolution rate under90cm from water surface.In the end CO2consumption of the spring outlet and the watershed have a close relation. The soil CO2concentration is maximum in summer and is minimum in winter. Correspondingly, the CO2consumption of the spring outlet showed the same regular. Finally,the carbon sequestration in spring field is about37.15t·a-1by using the standard limestone tablets. By using the water chemistry data, water level and monitoring data, we calculate the CO2consumption of the watershed,that is4.937t/a. |
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