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Kinetic Studies of Reactive Intermediates from the Oxidation of Atmospheric Alkenes

大气烯烃氧化反应中间体的动力学研究

基本信息

批准号：
NE/P013104/1
负责人：
Andrew Orr-Ewing
金额：
$ 53.32万
依托单位：
University of Bristol
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2017
资助国家：
英国
起止时间：
2017 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FP013104%2F1
关键词：
Kinetic Studies Reactive Intermediates Oxidation

项目摘要

Volatile organic compounds (VOCs) are emitted into the atmosphere by both natural (biogenic) and human sources. Alkenes such as isoprene, which constitute one class of these VOCs, are emitted by plants and form a major fraction of the biogenic emission. The main mechanisms for removal of alkenes from the troposphere, the lowest layer of the atmosphere, are oxidation reactions with ozone (O3) and hydroxyl (OH) radicals. Short-lived intermediate species called Criegee intermediates and hydroxyalkyl peroxy radicals are created during the oxidation of alkenes. Reactions of these intermediate species with gas molecules in the atmosphere like sulphur dioxide (a precursor to acid rain), carboxylic acids, nitric oxide (the simplest NOx gas) and other chemicals present at low concentrations result in products which lead to the formation of OH radicals, ozone and organic aerosol particles. The OH radical is considered the "cleanser of the atmosphere" because it is responsible for initiating the chemical removal of most of the VOCs emitted into the troposphere. Ozone in the troposphere is a pollutant and is detrimental to living organisms.Atmospheric aerosols affect Earth's climate by changing the amount of incoming solar radiation and outgoing terrestrial radiation. The aerosol particles can condense water from the surrounding air to produce cloud droplets, and greater cloud cover affects the amount of solar radiation penetrating to ground level. Understanding the reactivity of the intermediate species that lead to growth of organic aerosol particles can help us to better quantify the impact of alkenes on both the composition and future warming of the atmosphere. The reactive intermediates upon which this research focuses are short lived and their concentrations in the atmosphere are too small for direct measurement. Efficient methods have instead recently been developed for preparation of high enough concentrations of Criegee intermediates and hydroxyalkyl peroxy radicals to study their reactions under controlled laboratory conditions. This research will examine how quickly these intermediates react with a variety of trace atmospheric gases, and for the first time will study how the rates of these reactions change with temperature. Most chemical reactions become slower as the temperature decreases, but the Criegee intermediates are suspected to show faster reactions at lower temperature. This unusual behaviour is important to characterize because the temperature of the troposphere decreases with altitude.The lab-based measurements of reaction rates will be interpreted with the aid of quantum chemistry calculations of the structures and energies of intermediate species along reaction pathways. The resulting insights into the chemical reaction mechanisms will help us to make reliable predictions for the rates of many reactions taking place in the atmosphere. These different reactions are too numerous for exhaustive laboratory study. Instead, we will formulate relationships between the structures of the reacting species and their reaction rates from which reliable predictions can be made for unstudied reactions.We also need to understand what products are formed by these chemical reactions, because atmospheric chemistry generally involves a sequence of reactive steps. Product identification will require a collaboration with colleagues who operate a unique instrument at the Advanced Light Source (ALS) synchrotron facility at Lawrence Berkeley National Laboratory in California. The structures of the products will then be used to estimate their propensity to condense into organic aerosol particles.The global atmospheric model STOCHEM-CRI will be used to study the consequences of our new measurements for predictions of global concentrations of ozone, NOx, OH and aerosol particles in the atmosphere, with outcomes that will be of interest to the scientific community, policy makers and the general public.

挥发性有机化合物（VOC）通过自然（生物）和人为来源排放到大气中。烯烃，如异戊二烯，构成这些挥发性有机化合物的一类，由植物排放，并形成生物排放的主要部分。从对流层（大气的最低层）去除烯烃的主要机制是与臭氧（O3）和羟基（OH）自由基的氧化反应。在烯烃的氧化过程中会产生称为Criegee中间体和羟烷基过氧自由基的短寿命中间体。这些中间物质与大气中的气体分子如二氧化硫（酸雨的前体）、羧酸、一氧化氮（最简单的氮氧化物气体）和其他低浓度化学物质反应，产生的产物导致形成OH自由基、臭氧和有机气溶胶颗粒。OH自由基被认为是“大气的清洁剂”，因为它负责启动化学去除大部分排放到对流层的VOC。对流层中的臭氧是一种污染物，对生物体有害。大气气溶胶通过改变入射太阳辐射和出射地面辐射的量来影响地球的气候。气溶胶粒子可以凝结周围空气中的水分，产生云滴，更大的云层覆盖会影响穿透到地面的太阳辐射量。了解导致有机气溶胶颗粒增长的中间物种的反应性可以帮助我们更好地量化烯烃对大气成分和未来变暖的影响。本研究所关注的活性中间体寿命短，它们在大气中的浓度太小，无法直接测量。相反，最近开发了有效的方法来制备足够高浓度的Criegee中间体和羟烷基过氧自由基，以在受控的实验室条件下研究它们的反应。这项研究将研究这些中间体与各种痕量大气气体反应的速度，并首次研究这些反应的速率如何随温度变化。大多数化学反应随着温度的降低而变慢，但Criegee中间体被怀疑在较低温度下显示出更快的反应。这种不寻常的行为是很重要的特征，因为对流层的温度随高度降低。实验室为基础的测量反应速率将解释与援助的结构和能量的中间物种的量子化学计算沿着反应途径。由此产生的对化学反应机制的见解将有助于我们对大气中发生的许多反应的速率做出可靠的预测。这些不同的反应太多，无法进行详尽的实验室研究。相反，我们将阐述反应物种的结构和它们的反应速率之间的关系，根据这些关系可以对未研究的反应进行可靠的预测。我们还需要了解这些化学反应形成的产物，因为大气化学通常涉及一系列反应步骤。产品鉴定将需要与在加州劳伦斯伯克利国家实验室先进光源（ALS）同步加速器设施操作独特仪器的同事合作。这些产物的结构将被用来估计它们凝结成有机气溶胶粒子的倾向，全球大气模型STOCHEM-CRI将被用来研究我们新的测量结果，以预测大气中臭氧、NOx、OH和气溶胶粒子的全球浓度，其结果将引起科学界、政策制定者和公众的兴趣。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Investigation of the Production of Trifluoroacetic Acid from Two Halocarbons, HFC-134a and HFO-1234yf and Its Fates Using a Global Three-Dimensional Chemical Transport Model

DOI：
10.1021/acsearthspacechem.0c00355
发表时间：
2021-03
期刊：
影响因子：
0
作者：
Rayne Holland;M. Khan;I. Driscoll;R. Chhantyal-Pun;R. Derwent;C. Taatjes;A. Orr-Ewing;C. Percival-C
通讯作者：
Rayne Holland;M. Khan;I. Driscoll;R. Chhantyal-Pun;R. Derwent;C. Taatjes;A. Orr-Ewing;C. Percival-C

Investigating the Atmospheric Sources and Sinks of Perfluorooctanoic Acid Using a Global Chemistry Transport Model

DOI：
10.3390/atmos11040407
发表时间：
2020-04
期刊：
Atmosphere
影响因子：
2.9
作者：
Rayne Holland;M. Khan;R. Chhantyal-Pun;A. Orr-Ewing;C. Percival;C. Taatjes;D. Shallcross
通讯作者：
Rayne Holland;M. Khan;R. Chhantyal-Pun;A. Orr-Ewing;C. Percival;C. Taatjes;D. Shallcross

Temperature-Dependence of the Rates of Reaction of Trifluoroacetic Acid with Criegee Intermediates

三氟乙酸与 Criegee 中间体的反应速率的温度依赖性