Temporal and Spatial Variation of Water Chemistry and Environmental Indication of Drip Water in Karst Cave A Case Study of Zhijin Cave,Guizhou Province
The study of the geochemical process of the cave is of great significance to the development of the secondary deposits in the cave.From January 2015to December 2015,the water chemistry indexes of Zhijin Cave in Guizhou Province were monitored in a whole year.Results showed that:(1)the drip rate of dripwater and Ca~(2+),Mg~(2+),Sr~(2+)ion concentrations had the very good response to precipitation,but also reflected the certain lag,and Mg~(2+),Sr~(2+)ions carried by the climate signal is very persistent,Ca~(2+)ion concentration in the rainy season fluctuated;(2)drip water chemical properties in the chemical measurement were compliance with the erosion of limestone in Karst area on the overall,the ratio of Ca~(2+)/HCO_3~- was 1/2with up and down fluctuations;(3)significant positive correlation between the drop of SIc and SId was founed,drop of water in the liquid phase partial pressure of CO_2[lgPCO_(2(water))]and pH values showed a significant negative correlation,reflecting the important influence of the high concentration of CO_2in the overlying soil layer of cave drip water chemical processes;(4)the Mg/Ca and Sr/Ca ratios of drip water in rainy season after the arrival of the curve show obvious increase and reduction of feature,indicating that CaCO_3has in the soil layers before it did not reach the cave,and the bedrock layer occurred prior calcite precipitation(PCP), resulting in the increase of migrating to the inside of the Ca~(2+)ion concentration was less compared with the other ions;(5)The ratios of Mg/Ca and Sr/Ca in drip water presented the obvious seasonal variation,but seasonal ratios of Sr/Ca lagged significantly,and Mg/Ca ratios of interannual variation was more volatility,the change response is sensitive to the outside precipitation.