Tropospheric halogen chemistry: Reaction mechanisms, processes and global impacts

对流层卤素化学：反应机制、过程和全球影响

• 批准号: NE/J02449X/1
• 负责人: Martyn Chipperfield
• 金额: $ 26.59万
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FJ02449X%2F1
• 关键词: Tropospheric; halogen; chemistry; Reaction; mechanisms

Around two decades ago reactive halogen compounds (iodine, chlorine and bromine) were found to cause sudden ozone loss in the lowest part of the troposphere in the Arctic. In the meantime reactive halogens were also found in many other parts of the troposphere, mainly in the marine boundary layer but also over salt lakes, in the plumes of volcanoes, in the free troposphere and even in the middle of the continents. The sources for reactive halogens in the troposphere appear to be mainly natural, mostly linked to halides contained in sea water or salt deposits.The scientific community has made great progress in the measurement of these compounds and also in the understanding of the underlying release and transformation processes. Very detailed process models have been successful in reproducing the intricate chemistry which involves reactions in the gas phase, in and on aerosol particles as well as cloud droplets, which is why we refer to this as multiphase chemistry. Comparisons with field data show that the contribution of reactive halogens to ozone destruction is often on the order of 30-50% (e.g. at the Cape Verde observatory). However very few global models include reactive halogens in the troposphere. The models that do usually have to make crude assumptions regarding the sources and have to employ a reduced reaction mechanism to make it computationally feasible to perform global model runs. Another recent discovery is that chlorine atoms can contribute up to 15% to the chemical loss of methane in the tropics; this loss is not included in any of the climate models. In many continental settings several hundred parts per trillion (ppt) of chlorine have been found indicating that chlorine chemistry can be relevant there as well. It is important to stress that methane and tropospheric ozone are strong greenhouse gases.In this project we aim to strengthen the theoretical foundation for global models by thoroughly revisiting the reaction mechanisms, providing reduced reaction mechanisms that have been tested in process models for a variety of scenarios encountered in the global troposphere and by developing parameterisations for the release of reactive halogens. The outcomes from this work will be included in a state-of-the-art global chemistry-aerosol model in order to quantify the global impacts of reactive halogen chemistry on ozone destruction and production, methane destruction as well as the formation and growth of aerosol particles. Furthermore, we will compare current day scenarios with preindustrial scenarios in order to establish the importance of anthropogenic pollutants for the release of reactive halogens. This is motivated by the fact that many halogen release mechanism involve acidity and some are linked to nitrogen oxides. Anthropogenic activity has increased both atmospheric acidity and nitrogen oxide concentrations.This project brings together the UEA group with a long-standing experience in tropospheric halogen chemistry in virtually all tropospherically relevant areas and the Leeds group with a very strong track record in global modelling including halogen chemistry. This project is very timely as in the last few years several data sets have become available and more are being collected that allow us to test our model predictions on a much larger scale than possible just a few years ago. Given the potentially large impacts on tropospheric chemistry and climate the relevance of this project is significant.

大约20年前，人们发现活泼的卤素化合物(碘、氯和溴)会导致北极对流层最低层的臭氧突然丧失。与此同时，在对流层的许多其他部分也发现了活性卤素，主要是在海洋边界层中，但也在盐湖上空、火山羽流中、自由对流层中，甚至在大陆的中部。对流层中活性卤素的来源似乎主要是自然的，主要与海水或盐沉积中所含的卤化物有关。科学界在测量这些化合物以及了解潜在的释放和转化过程方面取得了很大进展。非常详细的过程模型成功地再现了复杂的化学反应，涉及气相、气溶胶颗粒内和气溶胶颗粒上的反应，以及云滴，这就是为什么我们将其称为多相化学。与实地数据的比较表明，活性卤素对臭氧破坏的贡献通常在30-50%左右(例如在佛得角天文台)。然而，很少有全球模型包括对流层中的活性卤素。这样做的模型通常必须对来源做出粗略的假设，并必须采用简化的反应机制，以使执行全局模型运行在计算上是可行的。最近的另一项发现是，在热带地区甲烷的化学损失中，氯原子的贡献率高达15%；这一损失没有包括在任何气候模型中。在许多大陆环境中，发现了百万分之几百(Ppt)的氯，这表明氯化学也可能与此有关。必须强调的是，甲烷和对流层臭氧是强烈的温室气体。在这个项目中，我们的目标是通过彻底重新探讨反应机制，提供已经在全球对流层遇到的各种情景的过程模型中测试的简化的反应机制，并通过开发活性卤素释放的参数化，来加强全球模型的理论基础。这项工作的成果将纳入最先进的全球化学-气溶胶模型，以量化活性卤素化学对臭氧破坏和生产、甲烷破坏以及气溶胶颗粒的形成和增长的全球影响。此外，我们将比较目前的情景和工业化前的情景，以确定人为污染物对活性卤素释放的重要性。这是因为许多卤素释放机制涉及酸性，有些机制与氮氧化物有关。人类活动增加了大气酸度和氮氧化物浓度。该项目汇集了UEA小组和利兹小组，前者在对流层卤素化学方面拥有几乎所有对流层相关领域的长期经验，后者在包括卤素化学在内的全球模拟方面有着非常出色的记录。这个项目非常及时，因为在过去的几年里，已经有了几个数据集，并且正在收集更多的数据集，使我们能够在比几年前更大的规模上测试我们的模型预测。鉴于对对流层化学和气候的潜在重大影响，该项目具有重大意义。

项目成果

Global Stratospheric Fluorine Inventory for 2004-2009 From Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) Measurements and SLIMCAT Model Simulations

• DOI: 10.5194/acp-14-267-2014
• 发表时间: 2014-01
• 期刊: Atmospheric Chemistry and Physics
• 影响因子: 6.3
• 作者: Alexander Brown;M. Chipperfield;N. Richards;C. Boone;P. Bernath

On the Regional and Seasonal Ozone Depletion Potential of Chlorinated Very Short-Lived Substances

• DOI: 10.1029/2018gl081455
• 发表时间: 2019-05-28
• 期刊: GEOPHYSICAL RESEARCH LETTERS
• 影响因子: 5.2
• 作者: Claxton, Tom;Hossaini, Ryan;Wilson, Chris
• 通讯作者: Wilson, Chris

A refined method for calculating equivalent effective stratospheric chlorine

• DOI: 10.5194/acp-18-601-2018
• 发表时间: 2018-01-19
• 期刊: ATMOSPHERIC CHEMISTRY AND PHYSICS
• 影响因子: 6.3
• 作者: Engel, Andreas;Boenisch, Harald;Joeckel, Patrick
• 通讯作者: Joeckel, Patrick

Quantifying the ozone and ultraviolet benefits already achieved by the Montreal Protocol.

• DOI: 10.1038/ncomms8233
• 发表时间: 2015-05-26
• 期刊: NATURE COMMUNICATIONS
• 影响因子: 16.6
• 作者: Chipperfield, M. P.;Dhomse, S. S.;Feng, W.;McKenzie, R. L.;Velders, G. J. M.;Pyle, J. A.
• 通讯作者: Pyle, J. A.

On the Cause of Recent Variations in Lower Stratospheric Ozone

• DOI: 10.1029/2018gl078071
• 发表时间: 2018-06
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: M. Chipperfield;S. Dhomse;R. Hossaini;W. Feng;M. Santee;M. Weber;J. Burrows;J. Wild;D. Loyola-D.-Lo