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To strengthen scientific management and sharing of greenhouse gas data obtained from atmospheric background stations in China, it is important to ensure the standardization of quality assurance and quality control method for background CO2 sampling and analysis. Based on the greenhouse gas sampling and observation experience of CMA, using portable sampling observation and WS-CRDS analysis technique as an example, the quality assurance measures for atmospheric CO,sampling and observation in the Waliguan station (Qinghai), the glass bottle quality assurance measures and the systematic quality control method during sample analysis, the correction method during data processing, as well as the data grading quality markers and data fitting interpolation method were systematically introduced. Finally, using this research method, the CO2 sampling and observation data at the atmospheric background stations in 3 typical regions were processed and the concentration variation characteristics were analyzed, indicating that this research method could well catch the influences of the regional and local environmental factors on the observation results, and reflect the characteristics of natural and human activities in an objective and accurate way.

The real-time, automatic, highly accurate and efficient system for measuring the mixing ratios of CO2, CH4, CO and N2O has been developed by combining the commercial FTIR system (Wollongong University) with an auto-sampling system and a working standard module. Based on the tests conducted, the FTIR showed the high precision and a relatively low accuracy associated with its poor determination of correction factors. The absolute error of the mixing ratio of CO was above 38.8 x 10(-9), suggesting that FTIR alone could not meet the requirement for the real time measurement. Using the working standard gases to adjust results from the FTIR significantly improved the accuracy of measurements. For both static and dynamic conditions, the discrepancies between the measured results and the real values were below 0.11 x 10(-6), 1.8 x 10(-9), 0.15 x 10(-9) and 0.5 x 10(-9) for CO2, CH4, N2O and CO respectively, meeting the requirements for the atmospheric real-time measurements. During 6 days in-situ measurements of greenhouse gas outside the lab, the precision of target gas can reach 0.05 x 10(-6), 0.2 x 10(-9), 0.07 x 10(-9), 0.5 x 10(-9) for CO2, CH4, N2O, CO, and inaccuracy can be 0.09 x 10(-6), 0.4 x 10(-9), 0.14 x 10(-9), 0.5 x 10(-9), respectively.

In-situ GC-FID system for atmospheric CH4 and CO mixing ratio measurements at the Shangdianzi (SDZ) GAW regional station in Beijing was designed and optimized in 2009 based on a comparable system at the Waliguan GAW global station in Qinhai. Results from this study indicate that the system's precisions for CH4 and CO are higher than 0.03% and 0.45% respectively, which can meet the quality target on background greenhouse gas observations by the World Meteorology Organization's Global Atmosphere Watch (WMO/GAW) program. The selection method of working standards for this system was established: two working standards (WH for the high concentration and WL for the low concentration) were selected, the concentrations of CH4 and CO in these two standards can cover the ambient mixing ratios of CH4 (2 007.1 x 10(-9) and 1 809.5 x 10(-9)) and CO (405.6 x 10(-9) and 123.8 x 10(-9)), an injection sequence was programmed so that the two standards were analyzed alternatively for every three runs. The measurement accuracies are high, as shown by the standard deviations less than 1.7 x 10(-9) and 1 x 10(-9), for CH4 and CO, respectively. This method has been applied to in-situ measurement of atmospheric CH4 and CO in North China.

To strengthen scientific management and sharing of greenhouse gas data obtained from atmospheric background stations in China, it is important to ensure the standardization of observations and establish the data treatment and quality control procedure so as to maintain consistency in atmospheric carbon dioxide (CO2) and methane (CH4) measurements from different background stations. An automated gas chromatographic system (Hewlett Packard 5890GC employing flame ionization detection) for in situ measurements of atmospheric CO2 and CH4 has been developed since 1994 at the China Global Atmosphere Watch Baseline Observatory at Mt. Waliguan, in Qinhai. In this study, processing and quality control flow of CO2 and CH4 data acquired by HP ChemStation are discussed in detail, including raw data acquisition, data merge, time series inspection, operator flag, principal investigator flag, and the comparison of the GC measurement with the flask method. Atmosphere CO2 and CH4 mixing ratios were separated as background and non-background data using a robust local regression method, approximately 72% and 44% observed values had been filtered as background data for CO2 and CH4, respectively. Comparison of the CO1 and CH, in situ data to the flask sampling data were in good agreement, the relative deviations are within +/- 0.5% for CO2 and for CH4. The data has been assimilated into global database (Globalview-CO2, Globalview-CH4), submitted to the World Data Centre for Greenhouse Gases (WDCGG), and applied to World Meteorological Organization (WMO) Greenhouse Gas Bulletin and assessment reports of the United Nations Intergovernmental Panel on Climate Change (IPCC).

In order to determine the possibility of measuring the root respiration by using root exclusion method, we conducted field experiments to measured total soil respiration and net soil respiration in three temperate grassland communities including Leymus chinensis free-grazed steppe, stipa grandis free-grazed steppe and Leymus chinensis degenerated free-grazed steppe in the growing season, 2005. At the same time, the proportion of the root respiration to the total soil respiration was estimated in different steppes by this method separately. The results indicated that the root exclusion method was very operable in estimating the proportion of the root respiration to the total soil respiration in temperate grassland communities, and the proportion varied from 25% - 45% with the mean value of 35.66%. The precision of this proportion was markedly improved compared with the correlation studies of both here and abroad, and it was provided with superior applied cost in the field of carbon cycle of grassland ecosystem.

In order to determine the proportion of the root respiration to the total soil respiration, field experiments were condusted to measured soil respiration in three temperate grassland communities including Leymus chinensis free-grazed steppe, stipa grandis free-grazed steppe and Leymus chinensis degenerated free-grazed steppe using root biomass ratiocination method in the growing season, 2005. At the same time, seasonal variation including root respiration, total soil respiration and proportion of the root respiration to the total soil respiration in different grassland communities were compared, and the influence of root biomass, water and temperature to these processes were expounded. The results indicated that the rule of the root respiration and total soil respiration in the three steps was a one-peak pattern with the season dynamic, the maximum rate was in the late of July, but in Leymus chinensis degenerated free-grazed steppe, the rate was obviously larger than the other two types between July and August; The proportion of the root respiration to the total soil respiration obviously changed in the growing season, and the proportion was varied from 40% - 50 % with the mean value of 40.3 % , but it was very different among three steps because of the regional differentiations.