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Urban oxidising capacity measurements using inert and reactive tracers

使用惰性和反应性示踪剂测量城市氧化能力

基本信息

批准号：
NE/K01501X/1
负责人：
Dudley Shallcross
金额：
$ 56.66万
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：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FK01501X%2F1
关键词：
Urban oxidising capacity measurements using

项目摘要

By definition, the urban environment is one where many people either live or work. During the course of a day, people will be outdoors for varying lengths of time and be exposed to different levels of air pollutants. During daytime, sunlight can provide the energy needed to produce the hydroxyl radical (written as HO), which is an extremely reactive species that acts like a detergent in the atmosphere, reacting with air pollutants. Therefore, we want to know how much HO there is in the urban atmosphere and how its level changes over the course of a day and from day to day as a function of time of the year. It is possible to measure HO directly using an instrument called FAGE and this has been carried out for some cities in the UK (e.g. Birmingham and London). These data have helped us to understand how HO varies in one location but the instrument FAGE is too expensive to replicate to allow us to make measurements across a city. HO is made and destroyed very rapidly, so a measurement of HO also tells us the ratio of the rate of its production to the rate of its removal and indeed FAGE can also tell us about the rate of its removal. Therefore, we can calculate the rate of production from these measurements, but these other measurements from a number of cities suggest that the rate of production of HO is underestimated based on our current understanding. One possibility is that there are missing sources that we don't know about? Given the importance of HO and other oxidants to urban air quality it is vital to try to work out what these missing sources are.With this in mind we have developed a new technique to allow us to measure the amount of HO (and other detergents) pollutants encounter as they move through the urban environment. In this way we will be able to build up a picture of how removal rates for pollutants varies across a City as a function of time of day, season, pollution loading etc. We will also be able to estimate how rapidly particles are made in the urban environment and begin to understand what controls their production. Particles can be released into the atmosphere directly, e.g. from car exhausts, (called primary particles) but can also be made in the atmosphere, a so called secondary particles. We want to know more about the sources of secondary particles as we can make reasonable estimates of primary particle sources. Particles are known to be bad for air quality and a reduction in levels would be of great benefit. In order to make these measurements we will release small amounts of organic molecules that react with oxidants such as HO and some molecules that don't react with anything. We have tagged the reactive molecules so we can tell them apart from ones that are there already into the city and will measure the levels of both reactive and inert species downwind of the release point. As these molecules disperse their level will drop because of dilution and the inert species will tell us the dilution rate, the reactive ones will drop even more as they will not only disperse but also react. By using these two pieces of information we can estimate their chemical removal rates and hence the amount of HO present. Other measurements of pollutants and meteorology will be made at the same time and we will then be able to estimate how quickly these pollutants are removed. Computer models that contain our current knowledge of urban air quality will be compared with all the measurement data and we will then be able to test a number of hypotheses for the missing source of HO and other oxidants. We will also carry out studies at night where HO levels are very low and a different oxidant called the nitrate radical (NO3) takes over. We have an instrument that can make measurements of NO3 and so we can compare the measurement of NO3 in one location with the NO3 experienced by pollutants as they pass through the city. In this way a detailed comparison can be made.

根据定义，城市环境是许多人生活或工作的地方。在一天中，人们在户外的时间长短不一，暴露在不同程度的空气污染物中。在白天，阳光可以提供产生羟基自由基（写为HO）所需的能量，这是一种极具活性的物质，在大气中起着清洁剂的作用，与空气污染物发生反应。因此，我们想知道城市大气中有多少HO，以及它的水平在一天中以及每天作为一年中时间的函数是如何变化的。可以使用一种称为FAGE的仪器直接测量HO，这已经在英国的一些城市（例如伯明翰和伦敦）进行了。这些数据帮助我们了解了HO在一个地点的变化，但是FAGE仪器太贵了，无法复制，无法让我们在整个城市进行测量。HO的生成和破坏速度非常快，所以测量HO也能告诉我们HO的生成速率与去除率之比，事实上，FAGE也能告诉我们HO的去除率。因此，我们可以从这些测量值中计算出生产速率，但这些来自许多城市的其他测量值表明，根据我们目前的理解，HO的生产速率被低估了。一种可能性是有我们不知道的缺失的信息来源？鉴于HO和其他氧化剂对城市空气质量的重要性，试图找出这些缺失的来源是至关重要的。考虑到这一点，我们开发了一种新技术，使我们能够测量污染物在城市环境中移动时遇到的HO（和其他洗涤剂）的数量。通过这种方式，我们将能够建立一个图像，了解污染物的去除率如何随着一天中的时间、季节、污染负荷等的变化而在城市中变化。我们还将能够估计在城市环境中产生颗粒的速度，并开始了解是什么控制了它们的产生。颗粒可以直接释放到大气中，例如汽车尾气（称为初级颗粒），但也可以在大气中产生，称为次级颗粒。我们希望更多地了解二次粒子的来源，因为我们可以对一次粒子的来源做出合理的估计。众所周知，颗粒物对空气质量有害，减少颗粒物的含量将大有裨益。为了进行这些测量，我们将释放少量与氧化剂（如HO）反应的有机分子和一些不与任何物质反应的分子。我们已经标记了反应性分子，这样我们就能把它们与已经进入城市的分子区分开来，并将测量释放点顺风处的反应性和惰性物种的水平。当这些分子分散时，它们的水平会因为稀释而下降，惰性物质会告诉我们稀释率，活性物质会下降得更多，因为它们不仅会分散，还会反应。通过使用这两条信息，我们可以估计它们的化学去除率，从而估计存在的HO的量。污染物和气象学的其他测量将同时进行，然后我们将能够估计这些污染物被清除的速度。包含我们目前对城市空气质量知识的计算机模型将与所有测量数据进行比较，然后我们将能够测试一些关于HO和其他氧化剂缺失来源的假设。我们还将在夜间进行研究，因为夜间的一氧化氮水平非常低，一种叫做硝酸根（NO3）的不同氧化剂会起作用。我们有一个可以测量NO3的仪器，因此我们可以将一个地方的NO3测量值与污染物穿过城市时所经历的NO3进行比较。这样就可以进行详细的比较。

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）

The first UK measurements of nitryl chloride using a chemical ionization mass spectrometer in central London in the summer of 2012, and an investigation of the role of Cl atom oxidation

DOI：
10.1002/2014jd022629
发表时间：
2015-06
期刊：
Journal of Geophysical Research: Atmospheres
影响因子：
0
作者：
T. Bannan;A. M. Booth;A. Bacak;J. Muller;K. Leather;Michael Le Breton;B. Jones;D. Young;H. Coe;J. Allan;S. Visser;J. Slowik;M. Furger;A. Prevot;James D. Lee;R. Dunmore;J. Hopkins;J. Hamilton;A. Lewis;L. Whalley;T. Sharp;D. Stone;D. Heard;Z. Fleming;R. Leigh;D. Shallcross;C. Percival
通讯作者：
T. Bannan;A. M. Booth;A. Bacak;J. Muller;K. Leather;Michael Le Breton;B. Jones;D. Young;H. Coe;J. Allan;S. Visser;J. Slowik;M. Furger;A. Prevot;James D. Lee;R. Dunmore;J. Hopkins;J. Hamilton;A. Lewis;L. Whalley;T. Sharp;D. Stone;D. Heard;Z. Fleming;R. Leigh;D. Shallcross;C. Percival

A study of global atmospheric budget and distribution of acetone using global atmospheric model STOCHEM-CRI

使用全球大气模型 STOCHEM-CRI 研究全球大气收支和丙酮分布