摘要
在温室气体本底浓度观测及其影响因素研究中,建立一套完整、可行的质量控制方法和流程至关重要。本论文从大气样品的flask瓶采样及存储方法、实验室前-后处理方法和过程、CO_2浓度及其碳氧稳定同位素分析、CO_2通量观测,以及全流程的质量控制措施及方法等方面进行综合分析与研究,初步形成了较为系统的质控流程和方法。
首先,调研并设计实验方案,对国产采样器和flask采样瓶、恒温烘箱脱附系统、真空检测-平衡系统进行综合测试,根据测试条件和相应结果进一步优化流程和方法,表明,用plourel O圈/玻璃阀芯的硬质玻璃flask采样瓶可显著降低材质对所存储的大气样品的影响;flask采样瓶首次使用前,经60℃、72h抽真空内表面热脱附,可基本去除新瓶内壁吸附的水汽和室温下不易挥发的杂质,使采集和存储的大气样品尽可能不失真。
其次,每次大气样品分析完毕,需将flask采样瓶抽真空后进行24h真空检测,并在系统真空条件下充填平衡气(其中CO_2浓度明显低于自然大气浓度),再发往采样站进行大气样品采集,以监控双瓶平行采样前是否用当地混合较均匀的大气冲洗完全。
再次,根据本底大气样品的分析精度要求,设计不同实验流程联合测试与调试,最终选择优化的条件及流程,实验室气体稳定同位素比分析系统(包括商业化MAT253主机及GasBench、自设计组装的16位自动进样系统、国外研发的Airtrap高效预浓缩气体捕集阱)对标气CO_2的碳氧稳定同位素比分析精度可分别达到0.02‰、0.05‰。
最后,在实验室对通量观测中常用的存储样品的气袋进行检测与处理,包括剖析气袋结构、气袋存储实验、分析过程中采取严格的工作标气穿插分析,对采样、运输及分析流程进行优化,形成了一套与温室气体本底浓度分析-质控-标校相一致的流程和方法,以保证通量观测数据与大气本底浓度观测数据的可比性,并为它们之间的互用建立了联系;在此基础上,获得了青海瓦里关地区CO_2、CH_4呼吸通量观测结果。
It is crucial to use a complete and feasible quality control method and procedure in researching observation of concentration variety of background greenhouse gases and its factors.From the method of flask sampling and atmospheric sample storage, flask treatment process in laboratory,concentration of and CO_2 carbon and oxygen isotope analysis,observation of fluxes of greenhouse gases three aspects as well as generally analysis and research of the full-flow quality control measures and methods,this study eventually basically formed a systemic quality control procedures and methods.
First of all,the experimental programs were designed and researched.Home-made auto-sampler and flasks,constant temperature oven and high vacuum flask cleaning system were tested.According to the test conditions and the corresponding results,further optimization of processes and methods was done.Through various laboratory tests,plourel O ring-glass spool rigid glass flasks can be made to significantly minimize the material quality of sampling bottle to the impact of gas storage.Before the fist storage of the new flask, vacuumizing and thermal desorption of inner surface of flasks in 60℃,72h can remove the water vapor adsorption not volatile at room temperature,as well as impurities as much as possible to ensure that storage gas is not contaminated;
Secondly,when the analysis of atmospheric samples was finished,sampling flask vacuumizing-storage for 24 hours-the vacuum check of the flasks was needed.On the vacuum conditions of the high vacuum flask cleaning system,filling the checked flasks with balance gas(CO_2 concentration was significantly lower than that of the concentration of natural atmosphere),then the flasks were sent to sampling stations.These measures were carried out to monitor whether the dual-parallel flasks were completely washed with well mixed local atmosphere before sampling;
Thirdly,according to the analysis accuracy of background greenhouse gases,a variety of experimental procedures were designed as well as joint testing and debugging were carried out,finaliy optimized conditions and procedures were selected.CO_2 stable isotope laboratory analysis system including commercial MAT253 host system and Gasbench injection system, home-made 16-bit auto-injection system,foreign R & D airtrap efficient pre-concentration trapping gases trap)was debugged to meet the analysis requirements.The final accuracy of carbon and oxygen isotope ratio analysis were 0.02‰,0.05‰;
Finally,the air bags storing samples frequently-used in flux observation were detected and deled,including the structural analysis of airbags,airbag storage experiments.Strict standard working gases were used to interspersing during analysis process of the sample.In accordance with the testing results,some adjustments were applied in the sampling and transportation to minimize pollution of the samples.Rigorous analysis-quality controlcalibration procedures and methods that were consistent with that of analyzing and correcting the concentration of atmospheric background greenhouse gases were formed to ensure the data obtained using the two different observing methods could be accuracy compared.Then the relationship of the values mutually used between two systems-observation system of background greenhouse gases and that of greenhouse gases was established.On this basis, high-quality observing data of fluxes of CO_2,CH_4 in Mt.Waliguan were obtained.
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