我国大气中新氢氟碳化物观测方法研究

HFC-227ea, HFC-236fa, HFC-245fa, HFC-365mfc and HFC-43-10mee, as so-called the New Hydrofluorocarbons (HFCs), are the alternative replacements of Chlorofluorocarbons (CFCs) and Hydrochlorofluorocarbon (HCFCs). They are produced and emitted to atmosphere as early as the beginning of this century and be detected in recent years. Their concentrations in the air are expected to be further increasing with the growing of production and usage. Because of their very high global-warming potential (GWP), the rapid accumulation of the new HFCs will has a new potential influence on the global and regional climate. Due to their extreme trace level in the air, the background observation of new HFCs has great challenge on the measurement techniques which requires high precision and very low detection limit. Untill now, there is no related report in China. Based on the original and expert work on the measurements of CFCs and HCFCs, this study will focus on the buildup of a suitable measurement and calibration method on the analysis of the New HFCs. The modification and optimization of the canister sampler, custom-made pre-concentration system, and gas chromatography-mass spectrometry (GC-MS), as well as the international comparison and calibration linking to the global reference scales, will be done together to ensure the measurement of the new HFCs in the background atmosphere in China. Finally, we plan to collect samples in 4 World Meteorological Organization/Global AtmosphereWatch (WMO/GAW) stations in China to study the background levels and variations of the New HFCs and to discover their possible influencing factors.

新HFCs（HFC-227ea、HFC-236fa、HFC-245fa、HFC-365mfc、HFC-43-10mee等）是CFCs和HCFCs的替代物种，本世纪初开始生产和排放，近几年在大气中被检出。随着排放量增大，预计其在大气中的浓度将迅速增加。由于这些新HFCs的全球增温潜能（GWP）极高，在大气中的积聚将对气候变化等全球和区域环境问题产生潜在影响。由于大气中各种新HFCs浓度极低，高精度观测其微小变化难度较大，国内尚未开展相关研究。本研究拟依托现有对CFCs和HCFCs等观测工作基础和国际先进技术经验，通过对大气采样器、自组装预浓缩进样系统、气相色谱质谱联用仪进行参数优化、改装，辅以国际比对、标定措施，建立适用于我国本底大气的新HFCs浓度观测流程和标定方法，分析并比对我国4个国家级本底站空气样品中新HFCs浓度，尝试探讨我国不同典型区域几种新HFCs浓度范围、变化特征和影响因素。

以大气中极低浓度的新HFCs为研究对象，借鉴国际先进经验技术，并对现有的气相色谱质谱联用系统进行改装和参数优化，实现了新HFCs的高精度分析。分析大气浓度范围（0.182~2.44ppt）的样品，精度达到0.0044~0.027ppt，相对精度0.67%~4.8%。自主研发了分别适用于本底站和城区站的新型采样器并获得使用新型专利。研究建立了采样流程、不锈钢采样罐预处理方法、标气配制-标校溯源体系，开展了气密性和潜在污染测试以及全流程的回收率和存储实验。在112天内，新HFCs的回收率95%~108%，浓度没有显著变化，表明本研究建立的采样-存储-运输-分析流程能够满足本底大气新HFCs的观测要求。. 选择我国4个本底站开展了1个完整年度每周1次的采样实验，采样点分别代表了青藏高原、京津冀、长江三角洲和东北平原的大气本底状态。2013年不同本底站新HFCs本底浓度水平接近，其中HFC-245fa本底浓度水平最高，达到1.7~1.9ppt，其他新HFCs本底浓度均低于1ppt。HFC-236fa各站只观测到个别污染事件，而临安和上甸子站均观测到较大比例的HFC-227ea污染事件，临安站本底数据率仅为28.2%。HFC-365mfc则是临安站非本底抬升浓度及相对比例最大的新HFCs。选择北京城区2个采样点于2013年5~10月开展了半年每周1次的采样观测，宝联和顺义站HFC-227ea和HFC-365mfc浓度均高于本底浓度。应用优化后的分析参数于2015年12月至2016年1月在北京上甸子站开展了1个月的在线观测实验，实验期间HFC-236fa、HFC-365mfc和HFC-43-10mee均未观测到污染事件，而HFC-245fa和HFC-227ea的抬升浓度可达1.5ppt和11ppt，揭示了HFC-227ea可能是华北区域抬升浓度最高、排放量最大的新HFCs。. 本项目发表论文6篇，其中SCI收录论文3篇, EI收录论文1篇。依托项目成果，获得实用新型专利1项，颁布行业标准1项，获得省级和司局级奖励各1项。项目执行期间，项目负责人4次参加国际学术会议并作口头报告。培养毕业博、硕士研究生各1名。本项目研究建立的我国大气新HFCs的观测分析方法总结成专著，并已应用于气象部门本底大气观测业务试运行。