Instability of Water Chemistry in the Karst Region——An Example from Central Guizhou

The chemical data from different kinds of waters in the central Guizhou showed that the spring water from the carbonate rock cracks(crack-water)presented neutrality or meta-al kalinity andCCa-Ⅱ.The amount of all ions and the concentrations of HCO₃^- and Ca²⁺ were higher in the autumn than that in the spring.The crack-water was influenced by the infiltration of surface water in the process of erosion and/or transportation with decrease in HCO₃^- and increase in pH, SO₄^2-,Cl^-,K⁺ and Na⁺,when running in a certain distance on the land surface. The concentrations of SO₄^2-,Na⁺,Fe³⁺ and NO₃^- of the Water fall Huang guoshu river at the Tianxing qiao(upper-stream),Shuiliandong(mid-water fall)and Luoshuitan(down-pool)varied closely with seasons.The CaCO₃ deposits violently with CO₂ release in the spring.In Lake Hong feng,areser voir in the karst region,the equivalentratio between HCO₃^- and SO₄^2- was only 2.1～2.4,but for Ca²⁺ and Mg²⁺ was up to 2.4～4.2.The concentrations increased in one time for Cl^- and in one quantitative level for the Na⁺ compared to the spring water,which suggested that these increase with solution in surface soils and pollution by mankind.The soil pore-water belonged to strong mineralized water and the lake water presented transitional water.The obvious differences in the water quality resulted from the carbonate deposition,sulphate mineralization and nitrogen fixation as well as ammonification.