FOREnSic Innovations to constrain GreenHouse Trace gas budgets

卤代烃是含有至少一个卤素原子，即氟、氯、溴或碘的有机分子。卤代烃几乎无处不在：冰箱、电视、灭火器、植物中，甚至空气中也有微量卤代烃。通常10亿个空气分子中只有不到一个卤代烃分子。但是，尽管这些低丰度的卤化碳都是强大的温室气体，是平流层臭氧的有力消耗者。目前，它们占人为温室效应的20%以上，这一比例在未来可能会增加。该项目的目的是探索一些高度创新的分析工具的能力，以提高目前对重要卤代烃及其过去、现在和未来在大气中的起源、分布和命运的了解水平。首先，卤碳气体中卤素的同位素比率将被用作一种全新的工具，以确定和量化持久性很强的化合物（如氟氯化碳）的源和汇。大多数国家都禁止使用氯氟烃。但由于它们分解得很慢，至少需要几十年才能从大气中消失。一个很重要的问题是，多长时间？答案的一部分可能在于平流层，这是氟利昂化合物分解的唯一地方。我正在研究氯氟烃中卤素的同位素，这些同位素包含了它们在平流层分解的确切方式和速度的信息。答案的第二部分取决于仍有多少氯氟烃被排放到大气中（例如，来自旧车、垃圾填埋场或非法使用）。为了区分多年前和现在大气中释放的氯氟化碳，我们可以再次从同位素信息中获益。这是因为不同的分子含有同位素“指纹”，这通常是制造过程的特征，也会随着大气中的时间而变化。因此，目标是检测尽可能多的“指纹”，并确定和量化剩余的排放量。其次，对大气中数量迅速增长的工业卤代烃化合物的检测的开创性工作将继续和扩大。卤代烃对全球变暖的威胁正在显现。大气中氟氯烃的替代化合物正在迅速增加，其中许多是强温室气体。工业过程中使用的化合物种类增加得如此之快，以至于科学家们都在努力跟上。在这个项目中，将研究扫描大气和追踪这些“新型”卤化碳的新技术。因此，这些化合物对气候和平流层臭氧所构成的威胁将得到估计。最后，将探索将二维气相色谱法和飞行时间质谱法用于大气痕量气体研究的有前途的方法，并将以前两项活动的结果为基础。该项目将有助于改进对臭氧层恢复的预测，并作为大气中卤代烃新出现的威胁的早期预警系统。社会将从所有这些活动中受益，因为它将有助于预测臭氧层——从而防止引起皮肤癌的紫外线辐射——何时将完全恢复。此外，该项目将有助于更好地了解卤代烃在气候变化方面产生的风险。它还将开发创新的新工具来研究大气的化学成分。

A halocarbon is an organic molecule containing at least one halogen atom, i.e. fluorine, chlorine, bromine or iodine. Halocarbons can be found almost everywhere: in refrigerators, in TVs, in fire extinguishers, in plants and - in small traces - in air. Usually there is less than one molecule of halocarbons in a billion air molecules. But despite these low abundances halocarbons both act as powerful greenhouse gases and are potent depleters of stratospheric ozone. They presently account for more than 20% of the anthropogenic greenhouse effect, and this fraction could potentially increase in the future. The aim of this project is to explore the capabilities of a number of highly innovative analytical tools to enhance the present level of understanding of important halocarbons and their origins, distributions and fate in the atmosphere in the past, present and future. Firstly, the isotope ratios of halogens in halocarbon gases will be used as a wholly novel tool to identify and quantify the sources and sinks of very persistent compounds such as the chlorofluorocarbons (CFCs). CFCs have been banned in most countries. But because they break down so slowly, it will take at least many decades before they disappear from the atmosphere. A very important question is, how long? One part of the answer could lie in the stratosphere, which is the only place where CFCs do break down. I am investigating the isotopes of halogens in CFCs and these contain information about the exact manner and speed of their stratospheric breakdown. The second part of the answer relies on how much CFC is still being released to the atmosphere (e.g. from old cars, landfills or illegal use). To distinguish in the atmosphere between CFC released years ago and CFC released now, one could again benefit from isotopic information. This is because the different molecules contain an isotopic 'fingerprint' which is often characteristic for the manufacturing process and also changes over time in the atmosphere. Consequently, the aim is to detect as many 'fingerprints' as possible and to identify and quantify the remaining emissions. Secondly, pioneering work on the detection of the rapidly growing number of industrial halocarbon compounds in the atmosphere will be continued and extended. There is an emerging threat from halocarbons with respect to global warming. The replacement compounds for CFCs are increasing rapidly in the atmosphere, and many of them are strong greenhouse gases. The variety of compounds used in industrial processes is increasing so fast, that scientists are struggling to keep up. Within this project new techniques to scan the atmosphere and track down these 'novel' halocarbons will be investigated. Consequently the threat posed by these compounds both to climate and to stratospheric ozone will be estimated. Finally, the promising methodologies of adapting two-dimensional gas chromatography and time-of-flight mass spectrometry for atmospheric trace gas studies will be explored and will build upon the outcomes of the first two activities. This project will contribute to improved predictions of the recovery of the ozone layer and serve as an early-warning system for emerging threats from halocarbons in the atmosphere. Society will benefit from all of these activities as it will help to predict, when the ozone layer - and thus the protection from skin-cancer-causing UV radiation - will fully recover. Moreover, this project will help to better understand the risks arising from halocarbons with regard to climate change. It will also develop innovative new tools with which to study the chemistry of the atmosphere.