喀斯特区域的水化学不稳定性——以黔中地区为例

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

黔中地区是岩溶作用发育的喀斯特区域。１９９３年秋和１９９４年春末采自该地区不同类型水样的水化学分析表明：碳酸盐岩裂隙泉水呈中偏碱性，为［Ｃ］Ｃａ－Ｉ型；秋季离子总量、ＨＣＯ－３及Ｃａ２＋浓度大于春季。裂隙泉水流经地表一定距离后，ＨＣＯ－３降低，ｐＨ及ＳＯ２－４、Ｃｌ－、Ｋ＋、Ｎａ＋明显增高。黄果树的天星桥、水帘洞及落水潭三个部位河水的ＳＯ２－４、Ｎａ＋以及Ｆｅ３＋、ＮＯ－３等浓度的季节性变化也更加明显。春季因瀑布暴气，ＣＯ２的逸出，钙华生成更强烈一些。红枫湖作为喀斯特区域地表水的汇集地，ＨＣＯ－３与ＳＯ２－４的当量比值仅２．１～２．４；Ｃａ２＋与Ｍｇ２＋比值上升为２．４～４．２，Ｃｌ－浓度较碳酸盐岩裂隙泉水增高１倍；Ｎａ＋浓度增高一个数量级。说明流域内地表土层溶蚀及人为污染影响的增强。土层孔隙水属强矿化水，而湖水呈现过渡特征。碳酸盐沉淀作用、硫酸盐矿化作用及固氮氨化作用，导致水质组成的显著差异。

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 alkalinity and Ca II. The amount of all ions and the concentrations of HCO - 3 and Ca 2+ 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 HCO - 3 and increase in pH, SO 2- 4, Cl -, K + and Na +, when running in a certain distance on the land surface. The concentrations of SO 2- 4,Na +,Fe 3+ and NO - 3 of the Waterfall Huangguoshu river at the Tianxingqiao (upper stream), Shuiliandong (mid waterfall) and Luoshuitan (down pool) varied closely with seasons. The CaCO 3 deposits violently with CO 2 release in the spring. In Lake Hongfeng, a reservoir in the karst region, the equivalent ratio between HCO - 3 and SO 2- 4 was only 2 1～2 4, but for Ca 2+ and Mg 2+ 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.