Research Of Co₂,ch₄ Calibration Process And Method

In the research of global greenhouse gases background watch, the quality of standard gases is essential for the accuracy of observations. It is important to set up a systematic calibration and propagation process and method of standard gases to ensure the stability,traceability and international comparability of observation data. The new CRDS calibration and propagation system for CO2 and CH4 was set up. Based on the experiments and data analysis, a new process and method which meet the WMO-GAW's QA/QC target was optimized. Based on the latest research progress of high-pressure cylinder gases worldwide, a new mixed standard gases preparation system was set up. Through kinds of tests, a simple and efficient process of mixed standard gases preparation was established. The research lay the foundation for improving the mixed standard gases sequence; obtaining the higher quality, more stable background observation data and further improving the calibration and propagation system of stations-Beijing Center Lab. The articles include the following sections:Firstly, a new system for calibration and propagation of mixed CO2 and CH4 standards was set up based on a novel technique Cavity Ring-Down Spectroscopy (CRDS). With simple and high efficiency calibration procedures, the system was stable and easily operation, less consumption and linearity response. Ambient CO2 and CH4 measurement precision better than 0.06ppm and 0.3ppb, accuracy better than±0.05ppm and±0.4ppb, respectively. Performance of the system can meet the requirements of the WMO-GAW's QA/QC target on background greenhouse gases measurement. The system can ensure consistency, traceability and international comparability of the observational data and applied in the calibration and propagation of CO2 and CH4 mixed standard gases among central lab and stations.Secondly, water vapor corrections associated with dilution and pressure-broadening effects for CH4 was derived from laboratory experiments, the correction factors was derived through analysis of the experiments'data. The calibration process and method was further optimized. Meanwhile, the original Beijing lab and Waliguan station's calibration systems were compared and evaluated with the new CRDS system, in order to ensure data interface effectively, some typical cases of historical data was re-analysis, and some necessary experiments and round-robin data was analyzed. All these results of the new system and process would give a further assurance to obtain higher quality of observational data.Thirdly, the international advanced high-pressure gas distribution program was introduced and localization. Based on the original Waliguan station's cylinder distribution experience and the new requirements, the new multi-element standard gases high-pressure distribution system was assembled, with simple and efficient process was established based on series of optimization test and analysis.Finally, the results were introduced to the research of greenhouse gases background watch.