Estimation of carbon isotope equilibria for calcite precipitation by on-site analysis

石笋的碳同位素比值很大程度上反映了土壤中有机碳来源的CO2，其碳同位素比值依赖于植被。当方解石沉淀过程中土壤中CO2的碳同位素比值记录到洞穴碳酸盐中时，其碳同位素比值可能受碳同位素分馏规律等因素的控制。利用石笋碳同位素比值建立了古植被信息的判别函数。现场测量是在一个山洞里进行的。在计算机模拟中，方解石沉淀的碳同位素比值平衡受滴水速率的影响。为评价碳同位素模拟结果，建立了洞穴内方解石自动沉积系统。通过实验室规模的实验对现场测量结果进行了检验。

The stalagmite carbon isotope ratio values largely reflect those of soil carbon dioxide derived from organic carbon associated with carbon isotope ratio values dependent on vegetation. When carbon isotope ratios of carbon dioxide in the soil are recorded into speleothem carbonate during calcite precipitation, the carbon isotope ratios may be controlled by the carbon isotope fractionation laws and other effects. We were clarified a discriminant function of paleo-vegetation information using carbon isotope ratio of stalagmite. The on-site measurement was done in a cave. As for a computer simulation, the carbon isotope ratio equilibrium of calcite precipitation was affected by a rate of drip water supply. For the evalation of simulation results of carbon isotope ratio, the automatically calcite deposition system was built in caves. These results of on-site measurement was examined by a experiments at the laboratoryscale.