岩溶碳汇效应研究中“碳”测定的不确定度分析--以溶解性无机碳为例

Uncertainty evaluation on the measurement of “carbon” in the research on karst carbon sink effect:A case for dissolved inorganic carbon

为建立非分散红外吸收法测定岩溶区流域水体中溶解性无机碳(DIC)分析结果不确定度的评定方法,采用不确定度连续传递模式,对两个岩溶地下水样的DIC测定结果的不确定度进行了评定。其主要做法是:先采用双误差回归方式对校准曲线进行拟合,对评定过程中各个不确定度分量进行量化,然后合成得到DIC测定结果的不确定度评定模型。通过实验结果计算表明:(1)测定结果的不确定度主要来源于标准溶液引入的不确定度、曲线拟合产生的不确定度和测定过程产生的不确定度。(2)样品的DIC含量越低,其相对不确定度越大,且校准曲线在拟合过程中所引入的不确定度对其测定结果的总不确定度具有较大的贡献率。

In order to set up an evaluation method for the uncertainty in determining dissolved inorganic carbon （DIC） in karst river basin by Non-dispersive Infrared （NDIR） absorption detection technique, the continuous propagation model of uncertainty is used to evaluate the uncertainties in determining DIC content of two typical karst groundwater samples. The main steps as follows： to fit the calibration curve by means of double-error regression firstly~ and then to quantify each uncertainty component in the evaluation process lastly to obtain the synthetic uncertainty model for DIC determination results. Calculations through experi- mental results show that. （1） the main sources of the measurement uncertainty derive from sub-uncertainties of calibration solutions and calibration curve fitting as well as measurements process; （2） the lower the DIC content in groundwater samples, the greater the relative uncertainty of measurement results, and the subuncertainty from the fitting of calibration curve makes the major contribution to the total uncertainty.