北京石花洞洞穴滴水中硫酸根浓度的时空变化及其意义

硫是环境地球化学循环中重要的元素之一，是区域及全球性环境变化的重要驱动因子。本文通过对石花洞洞穴4个滴水点（JG，SH，PL1和PL2）硫酸根浓度近3个水文年的分析测定（BL点观测近两年），结果表明:响应降雨快的滴水点（SH和JG点）滴水SO42-浓度升高幅度最明显，且滴水SO42-浓度与滴率成指数关系；滞后响应降雨的观测点滴水SO42-浓度雨季升高幅度不明显，但在长期观测期间有明显增加的趋势；对降雨没有响应的滴水点，其SO42-浓度低且雨季没有明显变化。通过分析表明，在快速响应降水的滴水点，滴水硫酸根浓度大幅升高可能在一定程度上影响滴水pH值，这也可能是导致雨季时，快速下渗进入洞穴的滴水碳酸钙饱和度降低，从而抑制滴水沉积的一个不可忽略的因素。 

Temporal-spatial variation of SO42- concentration of the drip water and its significance in the Shihua cave, Beijing

As a crucial element in environmental geochemistry cycle, sulfur reflects the environmental change on both regional and global scales. In this study, sulfate radical concentration form 4 drip water points (PL1, PL2, SH, JG) in the Shihua cave have been monitored for three years, and those form the drip water point(BL) was monitored for two years. Drip discharges show three types of response to surface precipitation variations: rapid response, response with associated time-lag and stable (no response). The results show that: (1) SO42- concentration in rapid response drip water increases sharply during rain period, and has a exponential relationship with drip rate.; (2) in the drip water of lag response, SO42- concentration has no significant increase during rainfall, but they show a increasing trend during a long-term monitoring; (3) SO42- concentration at the stable drip site is low and has no obvious change during wet season. This means that the sharp increase of SO42- concentration may influence to some extent the pH value at the rapid response sites, which results in the declined calcium saturation index (SIc) of the drip water in rainy season. So it may be a indispensable factor to restrain the deposition rate of the drip waters in the Shihua cave.