桂西北峰丛洼地泉水和溪流在降雨过程中的水化学动态变化特征

Variations in Chemical Composition of Spring and Stream Water during Rain Events in a Karst Peak Cluster-Depression Catchment,Northwest Guangxi,China

通过对中国科学院环江喀斯特农业生态系统观测研究站所在区域的泉水和溪流在降雨时的连续采集,发现二者的水化学特征对降雨的响应较快,但变化却不同。降雨时泉水的pH值在降雨时降低,电导率和主要离子浓度升高,SI降低,pCO2升高,而溪流的电导率和主要离子浓度降低,碳酸盐矿物饱和指数(SI)降低,水中二氧化碳分压(pCO2)降低。降雨时泉水和溪流的溶质输移速率明显增加,但没有表现出在连续降雨中因为降雨强度大输移速率就高的现象,从而推断,除了雨水的稀释作用和"土壤CO2效应"外,土壤包气带的"前水"以及土壤中可交换态离子也影响了降雨时峰丛洼地水体中溶质的运移。

A study was conducted on variations in chemical composition of surface and spring water in a typical karst peak cluster-depression catchment, Northwest Guangxi, during two rainfall events on Aug. 23 and Aug. 24, 2007. Both spring and surface waters displayed a quick response to the rainfall in terms of water chemistry. During the rainfall events, electronic conductivity （EC） and concentrations of both dominant cations and anions, carbonate saturation index （SI） and carbon dioxide pressure （pCO2） decreased in the surface water soon after rainfall, while those factors in the spring water generally showed op- posite variation trends. The solutes transportation rates of spring and stream flows increased during the rainfall period, but didn＇t ~how a positive relationship with rainfall intensity during continuous rainfall, revealing that besides the rain dilution effect and soil COz effect, the pre--event water stored in the soil vadose zone, as well as the amounts of exchangeable ions may affect the transportation of ions of both spring and stream flows in the karst peak cluster--depression catchment during rainfall.