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

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(N DIR)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 experimental 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 sub uncertainty from the fitting of calibration curve makes the major contribution to the total uncertainty.