温度及CO_2对方解石、白云石溶解度影响特征分析

Influences of temperature and P_(co_2) on the solubility of calcite and dolomite

借助水文地球化学模拟软件——PHREEQC对不同PCO2(0～100bar)和不同温度条件下(0～100℃)方解石、白云石在纯水中的溶解度进行模拟和分析。结果表明,PCO2和温度对方解石和白云石溶解度的影响均很大:无PCO2时其溶解度随着温度的升高而逐渐增大,这是因为对于方解石、白云石晶格破坏及溶解高温能提供的能量较大所致;当PCO2较大时(PCO2≥10-3.5bar)其溶解度随温度的升高而降低,原因主要是CO2在高温下形成碳酸的能力较差;当PCO2很小(0<PCO2<10-3.5bar)、温度较低时,方解石、白云石的溶解度随着温度的升高而逐渐降低,当温度升高到一定程度后其溶解度则随着温度的升高而逐渐升高,其原因是在低温时方解石和白云石的溶解主要是CO2发挥作用,而在高温时主要是温度起作用;在高PCO2条件下方解石、白云石的溶解度大于同温度、低PCO2条件下的溶解度;当含较多CO2的深部高温地下热水与浅部常态地下水混合时,其溶蚀能力将明显增强。

With the hydro geochemistry program PHREEQC, the solubility of calcite and dolomite in pure water are simulated and analyzed under different conditions（PCO2 0--100bar and temperature 0-100℃）. The result shows that PCO2 and temperature have great effect on their solubility. The solubility increases along with temperature when there is no Pcozdue to the more energy provided by the crystal lattice destruction and the high dissolution temperature. The solubility decreases along with the increases in temperature at higher PCO2（PCO2≥10^-3.5 bar）because it is difficult for CO2 to become carbonic acid at high temperature. At lower PCO2 （0〈PCO2〈10^-3. 5 bar）, the solubility also decreases along with the temperature increazing at low temperature, but increases at certain high temperature. The solubility of calcite and dolomite mainly depends on CO2 at low temperature, but depends on temperature at high temperature. The solubility under high PCO2 is greater than that under low PCO2 at the same temperature. When the deep hot water with more CO2 mixed with the shallow normal underground water, the corrosion will be enhanced remarkably.