Developing new laser-based instruments to characterise optical properties of aerosol particles from road traffic

道路交通仍然是英国颗粒物（PM）污染的最重要来源之一。随着尾气排放的减少，非尾气来源——包括悬浮的道路灰尘、轮胎和刹车摩擦——的PM变得越来越重要。非尾气颗粒物现在被认为在尾气源中占主导地位人们对影响非废气排放的因素了解甚少，因此很难制定减少PM的解决方案，也很难预测电动和混合动力汽车越来越受欢迎的未来变化。此外，这些决定气候和公共健康影响的粒子的物理特性有很大的不确定性。光学仪器已成为大气气溶胶的高（~ 1hz）时间分辨率的原位测量的流行。为了获得颗粒大小和折射率的定量信息，通常需要建立数学模型来反演原始数据。这些模型依赖于假设粒子是球形（或椭球），具有均匀或简单的核壳组成。该项目将专注于开发创新的激光仪器，以更准确地表征气溶胶颗粒的特性，特别是专注于提高非球形颗粒测量的准确性。博士候选人将开发基于散射光的角分布（通常称为散射相函数）来测量现场颗粒形态的技术。在现场直接测量气溶胶相位函数直到最近才得到证实（见图1），该项目将重点利用这些新能力来产生与交通相关的PM排放的重要新数据集这些数据集将减少交通排放对心肺健康、对流层化学和辐射强迫影响的不确定性。除了改进地面测量能力外，该研究项目还将改进遥感测量的验证。来自地面和卫星辐射计的气溶胶数据产品依赖于将仪器的视角相对于太阳联系起来的算法，以确定颗粒的大小分布和辐射效应。对散射相函数的不准确假设可能导致气候模式、卫星和地面辐射计之间的不一致，特别是在以非球形粒子为特征的地区（例如沙漠和城市地区）这个项目的目标包括：1。开发基于激光的新型仪器，以原位表征气溶胶颗粒的大小和形状；2. 在路边空气质素监测站安装仪器，测量车辆排放的废气；3. 将测量光散射与模型和遥感检索中实现的算法进行比较；4. 研究车辆类型和大气过程对交通颗粒物特征的影响。

Road traffic remains among the most significant sources of particulate matter (PM) pollution in the UK. With the decline in tailpipe emissions, non-exhaust sources - including resuspended road dust and tyre and brake friction - of PM are becoming increasingly important. Non-exhaust PM are now thought to dominate over exhaust sources.1 Factors that influence non-exhaust emissions are poorly understood, making it difficult to develop solutions for PM reductions and predict future changes as electric and hybrid vehicles become more popular. In addition, there is a great deal of uncertainty in the physical characteristics of these particles that determine climate and public health effects. Optical instruments have become popular for in situ measurements of atmospheric aerosol with high (~1 Hz) time resolution. In order to retrieve quantitative information on the particle size and refractive index, mathematical models are often required to invert raw data. These models rely on assumptions that the particles are spherical (or ellipsoids) with a homogeneous or simple core-shell composition. This project will focus on developing innovative laser-based instruments to more accurately characterise aerosol particle properties, specifically focusing on improving accuracy in measurements of non-spherical particles. The PhD candidate will develop techniques to measure particle morphology in the field based on the angular distribution of scattered light (commonly referred to as the scattering phase function). Direct measurements of aerosol phase function in the field have only recently been demonstrated (see Figure 1), and this project will focus on leveraging these new capabilities to produce vital new data sets on traffic related PM emissions.2,3 These data sets will reduce uncertainty in the effects of traffic emissions on cardiopulmonary health, tropospheric chemistry, and radiative forcing. In addition to improving ground-based measurement capabilities, this research project will also enable improved validation of remote sensing measurements. Aerosol data products from ground- and satellite-based radiometers rely on algorithms that relate the viewing angle of the instrument relative to the sun to determine the size distribution and radiative effects of the particles. Inaccurate assumptions of the scattering phase function may contribute to poor agreement between climate models, satellites, and ground-based radiometers, particularly in areas characterised by non-spherical particles (e.g. deserts and urban areas).4,5 Objectives The objectives of this project include: 1. Develop novel laser-based instrumentation to characterise aerosol particle size and shape in situ; 2. Deploy instrument to roadside air quality monitoring site to measure traffic emissions; 3. Compare measured light scattering with algorithms implemented in models and remote sensing retrievals; 4. Investigate the role of vehicle type and atmospheric processes on traffic particle characteristics.