Airborne nanoplastics: surface chemistry and cloud-crystallisation properties

The amount of micro and sub-micro-sized plastic particles polluting the environment is, unfortunately, increasing due to human activity. It has been shown that microplastics have an adverse effect on the environment, but little is known about their influence on the formation of ice in clouds (which alters the radiative properties of the Earth). Moreover, our theoretical understanding of the phenomenon of ice formation is fairly poor. As a result, models cannot be used accurately to predict whether a substrate will promote the formation of an ice nucleus within a body of liquid water. Therefore, experimental investigations are needed to assess whether a plastic species will promote the formation of ice crystals in clouds. For this purpose, microplastics are synthesized using cryogenic ball milling and separated in size by sieving. Their sizes and surface functionalities were investigated using characterization techniques such as XPS, optical microscopy, and IR spectroscopy.

The ice nucleating properties of the laboratory-made microplastics are investigated by performing droplet freezing experiments with suspensions of the plastic samples in ultrapure water. For this, the IceBox, a novel open droplet system, was used to cool suspension droplets at a constant rate in an atmosphere with controlled humidity. Depending on the plastic's chemical and physical characteristics, the micro and nano plastics could have a notable effect on the temperature of freezing of the droplets. This research will be of importance to both the field of atmospheric science and ice physics.

The production and processing of materials accounts for 15% of UK GDP and generates exports valued at £50bn annually, with UK materials related industries having a turnover of £197bn/year. It is, therefore, clear that the success of the UK economy is linked to the success of high value materials manufacturing, spanning a broad range of industrial sectors. In order to remain competitive and innovate in these sectors it is necessary to understand fundamental properties and critical processes at a range of length scales and dynamically and link these to the materials' performance. It is in this underpinning space that the CDT-ACM fits.

The impact of the CDT will be wide reaching, encompassing all organisations who research, manufacture or use advanced materials in sectors ranging from energy and transport to healthcare and the environment. Industry will benefit from the supply of highly skilled research scientists and engineers with the training necessary to advance materials development in all of these crucial areas. UK and international research facilities (Diamond, ISIS, ILL etc.) will benefit greatly from the supply of trained researchers who have both in-depth knowledge of advanced characterisation techniques and a broad understanding of materials and their properties. UK academia will benefit from a pipeline of researchers trained in state-of the art techniques in world leading research groups, who will be in prime positions to win prestigious fellowships and lectureships. From a broader perspective, society in general will benefit from the range of planned outreach activities, such as the Mary Rose Trust, the Royal Society Summer Exhibition and visits to schools. These activities will both inform the general public and inspire the next generation of scientists.

The cohort based training offered by the CDT-ACM will provide the next generation of research scientists and engineers who will pioneer new research techniques, design new multi-instrument workflows and advance our knowledge in diverse fields. We will produce 70 highly qualified and skilled researchers who will support the development of new technologies, in for instance the field of electric vehicles, an area of direct relevance to the UK industrial impact strategy.
In summary, the CDT will address a skills gap that has arisen through the rapid development of new characterisation techniques; therefore, it will have a positive impact on industry, research facilities and academia and, consequently, wider society by consolidating and strengthening UK leadership in this field.