柠檬酸对黄龙碳酸钙矿化影响的模拟实验研究

Simulation Experiment of Citric Acid Impacts on Mineralization of Calcium Carbonate in Huanglong

为探索生物因素在黄龙钙华沉积过程中的作用及参与程度,本研究以黄龙水体中2株嗜冷细菌胞外特征有机酸组分——柠檬酸为研究对象,通过模拟黄龙常年水温和p H值,结合碳酸钙晶体晶型和形貌,探讨柠檬酸钙化体系中的钙化过程及柠檬酸对碳酸钙晶型和形貌的影响。结果表明:1柠檬酸浓度高、p H值低和温度低都会一定程度地抑制碳酸钙沉积;2柠檬酸浓度(20、40、80、160mg/L)对碳酸钙晶型影响不大,主要合成方解石型碳酸钙,但随着浓度的增加,伴随有花瓣状形貌的生成;3随着p H值的增大,棱柱体形貌转变为边缘较为圆滑的椭球体。综上可见,柠檬酸对碳酸钙的钙化速率、晶型和形貌具有一定的影响和调控作用,其结果可为黄龙钙华生物成因的探究提供理论基础。

To explore the impact and the participation degree of biotic factors in the sedimentation process of the Huanglong travertine, the typical extracellular organic acid, citric acid, isolated from two psycbrotrophic bacteria strains from Huanglong, were used as object in this study. The temperature and the pH value were simulated as those of Huanglong water environments. Scanning electron microscope （SEM） and X-ray diffraction （XRD） were used to characterize the crystal form and morphology of CaCO3 precipitation. Then calcification process and the effect of citric acid on the crystal form and morphology of CaCO3 were investigated. The results were as followed： （1） High concentration, low pH value and low temperature inhibited the calcification in a certain extent. （2） Calcite was obtained in the presence of citric acid, and the petaline shaped precipitation formed when the concentration of citric acid became high. （3） Thombic particles switched to ellipsoids with curved edges as the pH value increased. In summary, the typical extracellular organic acids of Huanglong psyehrotrophic bacteria affected calcification rate, morphology and polymorphism of CaCO3. The results provided evidences for the biogenic theory of the Huanglong travertine.