EA-IRMS法测定不同类型土壤有机碳稳定性同位素组成

利用元素分析仪-稳定同位素比例质谱仪（EA-IRMS）分析系统，以国际标准物质Urea为基准，标定了高纯钢瓶CO2参考气，其δ13CvsPDB值为（-29.523±0.181）‰。通过试验对比检验了EA-IRMS分析系统的稳定性、线性和测定δ13C值的样品分析精度，建立了测定土壤中有机碳稳定性同位素的分析方法。其离子强度在1.0～7.0V之间具有良好的线性，在1.5～5.0V内的线性优于总体线性；样品分析精度优于0.15‰；样品含碳量大于5μg即可满足测定δ13C的分析要求。应用此方法实测了18份不同类型土壤的有机碳稳定同位素组成，获得其13C天然丰度平均值为1.082%；不同类型的土壤有机碳稳定同位素组成存在较大的差异。

Measurement of Organic Carbon Stable Isotope Composition of Different Soil Types by EA-IRMS System

Element analyzer-isotope ratio mass spectrometers (EA-IRMS) is a rapid and precise method for measuring stable carbon isotope. Pure CO2 reference gas was calibrated via international standard-Urea, and the δ13Cvs PDB value of pure CO2 is (-29.523±0.181)‰. Stability and linearity of EA-IRMS system, precision of δ13C measurement for samples were tested through experimentation comparison. Moreover, determination method of stable organic carbon isotope in soil was based on the system. The EA-IRMS system had well linearity when ion intensity ranged from 1.0 to 7.0V, and it excelled the total linearity when the ion intensity was from 1.5 to 5.0V, and the accurate result of δ13C for sample analysis could be obtained with precision of 0.15‰. If carbon content in sample is more than 5μg, the requirement for analyzing accurate result of δ13C could be achieved. The organic carbon stable isotope was measured in 18 different types soil samples, the average natural abundance of 13C was 1.082%, and the organic carbon stable isotope composition was significantly different among different type soil.