Aerosol science, the study of airborne particles from the nanometre to the millimetre scale, has been increasingly in the public consciousness in recent years, particularly due to the role played by aerosols in the transmission of COVID-19. Vaccines and medications for treating lung and systemic diseases can be delivered by aerosol inhalation, and aerosols are widely used in agricultural and consumer products. Aerosols are a key mediator of poor air quality and respiratory and cardiac health outcomes. Improving human health depends on insights from aerosol science on emission sources and transport, supported by standardised metrology. Similar challenges exist for understanding climate, with aerosol radiative forcing remaining uncertain. Furthermore, aerosol routes to the engineering and manufacture of new materials can provide greener, more sustainable alternatives to conventional approaches and offer routes to new high-performance materials that can sequester carbon dioxide. The physical science underpinning the diverse areas in which aerosols play a role is rarely taught at undergraduate level and the training of postgraduate research students (PGRs) has been fragmentary. This is a consequence of the challenges of fostering the intellectual agility demanded of a multidisciplinary subject in the context of any single academic discipline. To begin to address these challenges, we established the EPSRC Centre for Doctoral Training in Aerosol Science in 2019 (CDT2019). CDT2019 has trained 92 PGRs with 40% undertaking industry co-funded research projects, leveraged £7.9M from partners and universities based on an EPSRC investment of £6.9M, and broadened access to our unique training environment to over 400 partner employees and aligned students. CDT2019 revealed strong industrial and governmental demand for researchers in aerosol science. Our vision for CDT2024 is to deliver a CDT that 'meets user needs' and expands the reach and impact of our training and research in the cross-cutting EPSRC theme of Physical and Mathematical Sciences, specifically in areas where aerosol science is key. The Centre brings together an academic team from the Universities of Bristol (the hub), Bath, Birmingham, Cambridge, Hertfordshire, Manchester, Surrey and Imperial College London spanning science, engineering, medical, and health faculties. We will assemble a multidisciplinary team of supervisors with expertise in chemistry, physics, chemical and mechanical engineering, life and medical sciences, and environmental sciences, providing the broad perspective necessary to equip PGRs to address the challenges in aerosol science that fall at the boundaries between these disciplines. To meet user needs, we will devise and adopt an innovative Open CDT model. We will build on our collaboration of institutions and 80 industrial, public and third sector partners, working with affiliated academics and learned societies to widen global access to our training and catalyse transformative research, establishing the CDT as the leading global centre for excellence in aerosol science. Broadly, we will: (1) Train over 90 PGRs in the physical science of aerosols equipping 5 cohorts of graduates with the professional agility to tackle the technical challenges our partners are addressing; (2) Provide opportunities for Continuing Professional Development for partner employees, including a PhD by work-based, part-time study; (3) Deliver research for end-users through partner-funded PhDs with collaborating academics, accelerating knowledge exchange through PGR placements in partner workplaces; (4) Support the growth of an international network of partners working in aerosol science through focus meetings, conferences and training. Partners and academics will work together to deliver training to our cohorts, including in the areas of responsible innovation, entrepreneurship, policy, regulation, environmental sustainability and equality, diversity and inclusion.

Current world agriculture is heavily dependent on chemical inputs to deliver both nutrients for growth and pesticides and fungicides for plant health. To ensure sustainability of agriculture in the future, alternative ways have to be found to secure and increase crop yields whilst reducing the reliance on chemical resources to deliver healthy and productive crops. In Europe the range of products available to combat pest and pathogen attack has already been significantly reduced as a result of changes to EU pesticide and fungicide regulations. In addition there is increasing pressure by consumers on food suppliers and supermarkets alike, to deliver products that are pesticide-free. These drivers are now beginning to influence fundamental plant research which aims to better understand how plants respond to biotic (and abiotic) stresses, with the ultimate aim of identifying novel methods for detecting, monitoring and diagnosing biotic (and abiotic) stresses, and hence allowing more targeted approaches to chemical and other interventions. Plants produce a wide range of volatile organic chemicals (VOCs). The VOC profile for a particular plant species is unique; however that profile can change when a plant is subjected to biotic or abiotic stress. These compounds have a number of functions in plants, as signalling agents, as direct and indirect protectants against biotic stress (herbivores, pathogens) and as protectants against abiotic stresses (high temperature, oxidants). The aim of this project is to determine if it is possible to detect, diagnose and differentiate biotic and abiotic stresses in selected plant species. We have already shown this is possible at the leaf-level in preliminary work using tomato (Laothawornkitkul et al, Environ. Sci. Technol., 22, 8433 - 8438, 2008) but not at the whole plant, glass house or field scales. We will use wheat and oilseed rape as examples of field grown crops, and strawberry, often grown in the field but increasingly grown as a protected crop in the UK. Aphids will be used as the model pest, together with Botrytis as a necrotrophic pathogen and powdery mildew as a biotroph. To facilitate this work we will use the state of the art technologies of proton transfer reaction mass spectrometry (PTR-MS) and proton transfer reaction - time of flight - mass spectrometry (PTR-ToF-MS) with gas chromatography - mass spectrometry (GC-MS) for compound verification where necessary. Initially experiments will be conducted at Lancaster University using PTR-MS and GC-MS. The student will then work at Ionicon in Austria for 12 months, using their latest PTR-ToF-MS instrument, to generate more detailed mass-specific data. Whilst the student is on placement at Ionicon, opportunities will be sought for him/her to have knowledge exchange with experts in eddy covariance flux measurements at the University of Innsbruck, with a view to the possible extension of the work to the field scale. A comparison of profiles under controlled and field conditions will enable an assessment of how changing abiotic parameters impact upon the volatile profile of healthy, control plants compared to those challenged by biotic factors. In the project the student will therefore investigate and measure: the VOC profile of healthy plants; signature chemicals/profiles that designate a particular disease or pest; the level of infestation or infection required in order to detect a change in VOC profile; the impact of changing water status on VOC profiles in the presence or absence of pest or pathogens; how such profiles are modified in a 'real-world' situation where abiotic changes are uncontrolled. This will give the student training in a range of whole plant and chemical detection techniques. The project and industrial collaboration are designed not only to give first-class research training but also to produce first-class scientific output suitable for a PhD thesis.