Experimental Study On Mixed Dissolution Of Carbonate Rocks In Maocun Watershed Of Guilin

Since the industrial revolution,human beings have emitted more and more greenhouse gases into the atmosphere,and the greenhouse effect has also increased.At present,countries all over the world are paying attention to greenhouse gas emission reduction,and research on carbon cycle has become one of the hot issues.China's karst is mainly distributed in the southwestern region,and the karst area in the southwestern region accounts for more than one-third of the area in the southwestern region.It is of great significance to carry out the study of“karst carbon cycle”in the southwestern region.Conducting carbonate rock mixing and erosion experiments indoors and outdoors is conducive to accurate calculation of karst carbon sinks.Experiments are carried out to continuously dissolve carbonate rocks in different lithologies and different hydrodynamic conditions.At the same time,the mixed acid of carbonic acid,sulfuric acid and nitric acid and the mixed acid of sulfuric acid and nitric acid were used to dissolve the carbonate rock under closed conditions.The carbonate rock specimens are suspended in the water bodies of the three research sites of Xiaolongbei,bianyan and Beidiping.The test specimens are taken back every three months,and the water bodies are observed every month.The experimental period is one year.Our results show that:Lithology is an intrinSIc factor affecting the dissolution of saturated mixed dissolution solution.The dissolution of the mudstone limestone in the carbonic acid solution with a pH of 4 and 4.5 respectively reached saturation and then continued to dissolve.The amount of dissolution is 12.94 mg.The dissolution of the limestone,dolomite and gray dolomite under the same conditions are respectively for 12.00mg,2.10mg,2.00mg,the dissolution of limestone is 5.7⁶.5 times of dolomite.The flow velocity of the water flow is an external factor that affects the mixed dissolution of the carbonate rock.The larger the flow velocity difference,the larger the amount of mixed corrosion.The ratio of the amount of dissolution of the muddy limestone in the saturated mixed solution at a flow rate of 100 cm/s and a flow rate of 0 cm/s is 2.67,which is 2.67 at the flow rate of 15 cm/s and the amount of dissolution in a saturated mixed solution of 0 cm/s.The ratio of the amount of dissolution of dolomite under the same conditions is 5.The dissolution rates of mudstone and dolomite are all on the order of 10^-11 and10^-10 mol/?cm²·s?,and the acid concentration boundary is 0.7 in the two acids and 0.3mmol/L in the three acids.The dissolution of carbonate on carbonate rock is exponentially related to the concentration of exogenous acid.When the concentration of SO₄^2-and NO₃^-is 0.1⁰.3mmol/L,the dissolution of dolomite by carbonic acid accounts for 75.89⁵8.64%,the dissolution of mudstone limestone accounts for80.21⁵9.06%,and the concentration of SO₄^2-and NO₃^-is greater than 0.44 mmol/L,the dissolution is less than 50%.The mixed dissolution formed by the addition of exogenous water promotes the dissolution of the carbonate rock.The amount of carbonate dissolution in mixed karst water is 13²3 times that of carbonate rock in karst water.The dissolution of carbonate rock in the rainy season is greater than that in the dry season,and the limestone in karst water and mixed karst water is deposited in the dry season.