Trends and emissions of six perfluorocarbons in the Northern Hemisphere and Southern Hemisphere
Trends and emissions of six perfluorocarbons in the Northern Hemisphere and Southern Hemisphere
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DOI：
10.5194/acp-20-4787-2020
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发表时间：
2020-04-24
影响因子：
6.3
通讯作者：
Laube, Johannes C.
中科院分区：
文献类型：
--
作者：
Droste, Elise S.;Adcock, Karina E.;Laube, Johannes C.
全氟化碳（PFC）是一种强效温室气体，在100年的时间范围内，其全球变暖潜力高达二氧化碳的数千倍。全氟化学品没有任何重要的汇，这意味着它们在大气中的寿命长达数千年。人类生产被认为是大多数全氟化学品的唯一来源。在此，我们报告了以下PFC的全球大气丰度的最新情况，其中大多数首次根据其异构体进行了分析分离：八氟丁烷（c-C4 F8），正癸氟丁烷（n-C4 F10），正十二氟戊烷（n-C5 F12），正十四氟己烷（nC（6）F（14））和正十六氟庚烷（n-C7 F16）。此外，我们报告的第一个数据集的全氟-2-甲基戊烷（i-C6 F14）的大气混合比。由于分离全氟化学品异构体的分析挑战性，此前从未报道过全氟化学品异构体的存在及其重要性。时间序列从1978年到现在。几个数据集被用来调查这些PFC的时空趋势：从1978年到2018年初在澳大利亚格里姆角收集的空气样本的时间序列; 2015年7月至2017年4月在英国塔科尔内斯顿收集的空气样本的时间序列;以及来自台湾的密集的基于温室气体的采样收集。虽然南半球格里姆角的远程“背景”时间序列表明，这些PFC中的大多数最近的增长率低于20世纪90年代，但我们继续看到混合比显着增加，到2017年底，与2010年测量的丰度相比，混合比高出6%至27%。塔科尔内斯顿的空气样本显示，与南半球基线相比，全氟化碳混合比率出现正偏移。台湾的空气样本中的混合比率和变异性最高，因此，台湾可能更接近全氟化学品的排放源，这证实了大多数全氟化学品主要来自北方半球。尽管这些全氟化碳在大气中的含量为万亿分之一摩尔或更低，但到2017年底，其全球累计排放总量转化为8.33亿公吨二氧化碳当量，其中23%是自2010年以来排放的。在过去十年中，近三分之二的二氧化碳当量排放量可归因于c-C4 F8，其目前的排放率也最高，而且还在继续增长。本工作所涵盖的所有全氟化学品的来源仍然没有得到严格的限制，全球数据库中报告的排放量并没有说明大气中的丰度。
Perfluorocarbons (PFCs) are potent greenhouse gases with global warming potentials up to several thousand times greater than CO2 on a 100-year time horizon. The lack of any significant sinks for PFCs means that they have long atmospheric lifetimes of the order of thousands of years. Anthropogenic production is thought to be the only source for most PFCs. Here we report an update on the global atmospheric abundances of the following PFCs, most of which have for the first time been analytically separated according to their isomers: coctafluorobutane (c-C4F8), n-decafluorobutane (n-C4F10), ndodecafluoropentane (n-C5F12), n-tetradecafluorohexane (nC(6)F(14)), and n-hexadecafluoroheptane (n-C7F16). Additionally, we report the first data set on the atmospheric mixing ratios of perfluoro-2-methylpentane (i-C6F14). The existence and significance of PFC isomers have not been reported before, due to the analytical challenges of separating them. The time series spans a period from 1978 to the present. Several data sets are used to investigate temporal and spatial trends of these PFCs: time series of air samples collected at Cape Grim, Australia, from 1978 to the start of 2018; a time series of air samples collected between July 2015 and April 2017 at Tacolneston, UK; and intensive campaign-based sampling collections from Taiwan. Although the remote "background" Southern Hemispheric Cape Grim time series indicates that recent growth rates of most of these PFCs are lower than in the 1990s, we continue to see significantly increasing mixing ratios that are between 6% and 27% higher by the end of 2017 compared to abundances measured in 2010. Air samples from Tacolneston show a positive offset in PFC mixing ratios compared to the Southern Hemisphere baseline. The highest mixing ratios and variability are seen in air samples from Taiwan, which is therefore likely situated much closer to PFC sources, confirming predominantly Northern Hemispheric emissions for most PFCs. Even though these PFCs occur in the atmosphere at levels of parts per trillion molar or less, their total cumulative global emissions translate into 833 million metric tonnes of CO2 equivalent by the end of 2017, 23% of which has been emitted since 2010. Almost two-thirds of the CO2 equivalent emissions within the last decade are attributable to c-C4F8, which currently also has the highest emission rates that continue to grow. Sources of all PFCs covered in this work remain poorly constrained and reported emissions in global databases do not account for the abundances found in the atmosphere.