Quantifying the health and climate impacts of vehicle particulate emissions

Particulate matter (PM) is a key atmospheric pollutant regulated at the national and international levels. PM arises from solid and liquid particles directly blown into the air and from gases that condense into droplets. PM has been directly linked to increased mortality, especially the very small (<100 nm) particles which can inflame tissue deep in the lungs. One of the largest sources of PM in the UK is road traffic, which includes emissions from engine exhaust, as well as tyre and brake abrasion and lofted dust from the road surface. Over the past two decades, the amount of PM emitted from traffic has decreased substantially due to regulations pushing for cleaner internal combustion engines in vehicles. However, as the number and weight of vehicles on the road increases, more particles from non-exhaust sources (e.g. tyres and brakes) are emitted. Unlike fossil fuel combustion byproducts, these particles are not well characterised. It is unknown, for example, what driving conditions enhance the production of non-exhaust particles, whether the particles are small enough to affect human health, and how these particles interact with gases in the atmosphere.

PM produced by human activity is also an important contributor to changes in climate. Soot particles produced by fossil fuel combustion, including those found in the exhaust of diesel and petrol vehicles, absorb sunlight and enhance the net warming of the planet. Particles from other sources, such as condensed gases, can have a cooling effect on the climate by reflecting sunlight. Reflected sunlight is measured by satellites to map out the PM levels across the globe. In order to accurately determine PM concentration from satellite measurements it is important to understand how different types of particles interact with light. This information is also vital for predicting future changes in climate using computer simulations of the atmosphere. As the types of particles produced by road traffic changes over time, the interactions of these particles with incoming sunlight will be affected.

In this research project, I will build three instruments to better understand characteristics of particles produced by road traffic in a typical UK city centre. The first instrument will measure the sizes of the particles - information directly relevant to public health officials who can focus future pollution reduction efforts on areas where very small particles are detected. The other two will measure the light absorbed and reflected by the particles in air. These data are useful for checking the accuracy of calculations used to predict future changes in climate and information reported by satellites. Additionally, we can combine this information with existing measurements of gases to better understand the chemistry of the urban atmosphere since gases and particles are closely linked.

This research programme will benefit a broad range of stakeholders through different avenues. Monitoring urban aerosol, particularly the ultrafine particulate matter, is important for evidence-based policy decisions to reduce harmful PM pollution in city centres and for quantitatively assessing the effectiveness of legislation after implementation. Hopefully, this will lead to healthier UK cities in the future. The data will also improve chemical models for more accurate forward projections of future changes in climate based on current trends.

Deploying instrumentation to ground sites, particularly those located in population centres, provides an excellent opportunity to engage with the general public. Seeing these instruments in person can change the way people think about their actions and how they affect our shared environment.

Since the research is being undertaken at a large, highly-ranked Chemistry department, it will likely include several Masters and Doctoral studentship projects. This will provide opportunities to teach skills required for instrument development and data analytics, as well as critical thinking to independently develop creative solutions.

The research is highly multidisciplinary, tying together aspects of optics, electronics, and atmospheric chemistry. By combining instrument development with in situ measurements that can be analysed utilising pollution modelling tools, this project touches on the three general areas of atmospheric chemistry: laboratory work, field studies, and computer modelling. The project will also foster national and international collaborations, especially with scientists at the US National Oceanic and Atmospheric Administration (NOAA). These collaborations are vital for building large data sets and sharing technological advances