一种特殊的碳酸盐沉积及其环境意义——“贵州乌江渡水电站灌浆帷幕老化问题的研究”中的发现

A SPECIAL KIND OF CARBONATE DEPOSIT AND ITS ENVIRONMENTAL SIGNIFICANCE——FINDINGS FROM THE STUDY “ON THE AGING OF CEMENT-GROUTING CURTAINS AT WUJIANGDU HYDROPOWER STATION OF GUIZHOU”

通过水化学、碳稳定同位素和碳酸盐沉积物沉积速率的对比分析 ,发现在贵州乌江渡坝址灌浆廊道中存在两种不同类型的碳酸盐沉积物 ,即 :放CO2 型和吸CO2 型。前者如通常岩溶洞穴中所见 ,是天然条件下岩溶作用的产物 ;而后者则很特殊 ,它是灌浆帷幕和混凝土发生碳酸盐化的结果。由于碳酸盐化时自大气迅速吸入CO2 ,使得廊道中CO2 浓度降低 ,并每年可产生高达 10cm的碳酸盐沉积物。考虑到世界范围内水泥的大量使用 ,水泥或混凝土碳酸盐化的环境意义 ,即在全球碳循环的研究中对大气CO2 沉降的贡献是不容忽视的。据初步估算 ,该碳贡献量每年约 1亿t左右。

Based on the analyses and comparisons of water chemistry, stable carbon isotopes and deposition rates of carbonate deposits, the author found that there are two kinds of carbonate deposits in the tunnels at Wujiangdu dam site, Guizhou, China, i.e., the CO 2 outgassing type and the CO 2 absorbing type. The former is natural, as observed in normal karst caves, and the product of karst processes under natural conditions. The latter, however, is special, resulting from the carbonation of a cement grouting curtain and concrete. Due to the quick absorption of CO 2 from the surrounding atmosphere, which is evidenced by the low CO 2 content in the air and the high deposition rate of carbonate deposits(as high as 10 cm/a) in the tunnels, the contribution of the carbonation process to the sink of CO 2 in the atmosphere is important, being in the order of magnitude of 10 8 tons carbon per year,and should be taken into account in the study of the global carbon cycle because of the use of cement in large quantity in the world.