Estimation On Carbon Sink Of Carbonate Rocks Dissolution In Southwest Karst Area Of China Under The Impact Of Agricultural Activities And Urbanization Based On GIS

With the enhancement of the focus and attention on global warming, all social circles make different efforts to greenhouse gas’increasing carbon sink and emission reduction. Study on carbon sink is becoming a central issue of the response to global warming, especially more attention on the karst process and carbon sink in the vast karst area. In the form of dissolved inorganic carbon (DIC), the karst process depletes CO2in the atmosphere or soil. Studies have shown that DIC which is generated by the carbonate dissolved is not simply from the CO2in the atmosphere or soil. With the development of agriculture, industry and urbanization, the introduction of non-carbonated substances in the social production and life, like nitric acid and sulfuric acid, they also can dissolve carbonate rocks and increase the DIC content, but this form of dissolution doesn’t consume CO2in the atmosphere or soil. Therefore, the accurate calculation on the CO2sink which comes from the dissolution of carbonate rocks can provide help to further improve the global carbon cycle model theory.In this thesis, the representative points are Qingmuguan subterranean stream watershed where has been suffered strong interference from anthropogenic agricultural activities and Nanshan Laolongdong subterranean stream watershed where has been suffered strong interference from the process of urbanization, the surface of the study area is karst areas in southwest of China, and with the help of a combined method of standard limestone tests and hydrochemistry-discharge as well as stable isotopes, we reveal the characteristics of karst process and the influence of human activities on the karst carbon sink. We apply high-resolution HCO3-and flow data which are obtained by automated online monitoring technology to explore the factors that affect carbon sink, and quantitatively analyze the influence of human activities on the karst carbon sink using2010-2012water chemistry and δ13CDIC.Using ArcGIS as a platform, relying on the spatial analysis capabilities of GIS, we obtain the karst and land-use type data of southwest of China and estimate its’karst carbon sink. Finally, we reckon the karst Process net carbon sink strength from the study of typical representative point and build a model of regional-scale net carbon sink.For the above purpose, we can draw several major conclusions: Monthly field measured data in the point study area of Qingmuguan and Nanshan shows that there is a positive good linear correlation between HCO3-and EC. From high-resolution HCO3-and flow data, we calculated that in Qingmuguan subterranean stream the average annual was2214.37×104mol,194.24×104mol/km2·a.In Nanshan Laojundong subterranean stream, HCO3-concentrations was1503.1×l04mol per year, unit area was119.29×104mol/km2·a.The rates of dissolution under various land use types differences in time and space. There are seasonal changes in time, and on the whole the rates of dissolution of summer is the highest, autumn followed, spring lower, and winter is the lowest, there is no obvious regularity of the soil under the vertical space. Between different types of land, the rates of dissolution of woodland (64.15t/km2·a) is the highest, then paddy fields (58.22t/km2·a) is higher than dryland (56.09t/km2·a), grass (36.73t/km2a) is the lowest, the rates of dissolution of the remaining points of the southwest region also have a similar regular pattern.Relation between Ca2+、Mg2+、HCO3-and carbon isotopic of groundwater proved that originated from anthropogenic activities in Qingmuguan and Nanshan subterranean stream watershed did take part in dissolving,but not cunsune the CO2from the air or soil.The average DIC from dissolution of carbonate rocks by carbon acid was14.5×106mol/a,net CO2sinks319t/a or87tC/a,which was close to the result303.28tC/a caculated in the method of standard limestone tests in Qingmuguan.The total DIC concentrations from dissolution of carbonate rocks by carbon acid in Nanshan was8.57×l06mol/a and6.803×105mol/km2a.And the total DIC concentrations of carbonate rocks dissolution oregined nitric acid and sulfuric acid erosion was6.459×106mol/a, net CO2carbon sink was188.57t/a, unit area was0.5127×106mol/km2a.Hydrochemistry results of both Qingmuguan and Nanshan showed that the DIC concentrations from dissolution of carbonate rocks by carbon acid in groundwater taked an average ratios of63.07%in total DIC concentrations. And the ratios of DIC from dissolution of carbonate rocks by nitric acid and sulfic acid nitric acid and sufric acid were36.63%.Use the63.07%proportion as a parameter to set up a regional scale net carbon sink model under the influence of human activities in the southwest karst area is: Fco2=l/2×0.6307x[HCO3-]×M×S×M(CO2)/M(HCO3-)Through corrected model, we can calculate the net CO2sink based on karst process of the entire southwest region was1233.3×104t/a, which was equivalent to336.44×104t/a carbon.