Improving our understanding of aerosol formation, transformation and lifetime in the atmosphere

Quantifying the partitioning of molecular constituents between the gas and vapour phases is important for understanding aerosols in a broad range of contexts including air quality and the unintentional, intrinsic, or intentional release of aerosolised material. These might include anthropogenic emissions of vapours and particles from cars, the biogenic emissions of organic components in a boreal forest, and the release of vapours and particles from explosive materials, respectively. Not only does phase partitioning govern aerosol particle mass concentrations and size distributions, but it governs the transport of material away from source, and the lifetime and rates of chemical processing and degradation of the source material. Most importantly, this partitioning is dependent on the temperature-dependent vapour pressures of the molecular constituents, their mixing with other aerosol constituents, and the dependence of the partitioning on environmental conditions such as relative humidity (RH). Although of central importance to the whole endeavour of aerosol science, versatile and accurate models of the gas-particle partitioning and component vapour pressures remain largely un-validated. New experiments are required capable of measuring the vapour pressures of components below 1 Pa, representing semi-volatile, low-volatility and extremely low-volatility components. In this project, measurements of the vapour pressures of semi-volatile and low volatility components (1E-6 to 1 Pa) will be made using an electrodynamic balance capable of measuring particle size changes of only a few nanometres on a timescale of hours over wide ranges in RH (<5% to 90%) and temperature (250 to 340 K). Measurements will be made for typical environmental aerosol constituents and surrogates of components, with the ultimate aim of providing an enhanced training set of properties to refine predictive tools for vapour pressures. Measurements will be made with varying conditions (RH and temperature) and with exposure to typical oxidants driving chemical transformation. These improved models will be used in models of gas-particle partitioning, including in transport and box models, to understand the dilution, dispersal and lifetime of aerosol constituents once released from source.

Aerosol science has a significant impact on a broad range of disciplines, extending from inhaled drug delivery, to combustion science and its health impacts, aerosol assisted routes to materials, climate change, and the delivery of agricultural and consumer products. Estimates of the global aerosol market size suggest it will reach $84 billion/year by 2024 with products in the personal care, household, automotive, food, paints and medical sectors. Air pollution leads to an estimated 30-40,000 premature deaths each year in the UK, and aerosols transmit human and animal infections. More than 12 million people in the UK live with lung disease such as asthma, and the NHS spends ~£5 billion/year on respiratory therapies. Many of the technological, societal and health challenges central to these areas rely on core skills and knowledge of aerosol science. Despite this, an Industrial Workshop and online survey (held in preparation for this bid) highlighted the current doctoral skills gap in aerosol science in the UK. Participating industries reported that only 15% of their employees working with aerosol science at doctoral-level having received any formal training. A CDT in aerosol science, CAS, will fill this skills gap, impacting on all areas of science where core training in aerosol science is crucial.

Impact on the UK aerosol community: Aerosol scientists work across governmental policy, industrial research and innovation, and in academia. Despite the considerable overlap in training needs for researchers working in these diverse sectors, current doctoral training in aerosol science is fragmentary and ad hoc (e.g. the annual Fundamentals of Aerosol Science course delivered by the Aerosol Society). In addition, training occurs within the context of individual disciplines, reinforcing artificial subject boundaries. CAS will bring coherence to training in the core physical and engineering science of aerosols, catalysing new synergies in research, and providing a focal point for training a multidisciplinary community of researchers. Working with the Aerosol Society, we will establish a legacy by providing training resources for future researchers through an online training portal.

Impact on industry and public-sector partners: 45 organisations have indicated they will act as CAS partners with interests in respiratory therapies, public health, materials manufacturing, consumer and agricultural products, instrumentation, emissions and environment. Establishing CAS will deliver researchers with the necessary skills to ensure the UK establishes and sustains a scientific and technical lead in their sectors. Further, it will provide an ideal mechanism for delivering Continuing Professional Development for the existing workforce practitioners. The activity of CAS is aligned to the Industrial Strategy Challenge Fund (e.g. through developing new healthcare technologies and new materials) and the EPSRC Prosperity Outcomes of a productive, healthy (e.g. novel treatments for respiratory disease) and resilient (e.g. adaptations to climate change, air quality) nation, with both the skilled researchers and their science naturally translating to long-lasting impact. Additionally, rigorous training in responsible innovation and ethical standards will lead to aerosol researchers able to contribute to developing: regulatory standards for medicines; policy on air quality and climate geoengineering; and regulations on manufactured nano-materials.

Public engagement: CAS will provide a focal point for engaging the public on topics in aerosol science that affect our daily lives (consumer products, materials) through to our health (inhalation therapeutics, disease transmission and impacts of pollution) and the future of our planet (geoengineering). Supported by a rigorous doctoral level training in aerosol science, this next generation of researchers will be ideally positioned to lead debates on all of these societal and technological challenges.