Particle Size Magnifier for Fundamental Nucleation Studies

This proposal is concerned with an atmospheric process referred to as nucleation. The term nucleation refers to the process where molecules of vapour in the air attach together and begin to grow into liquid droplets or solid particles which ultimately become tiny specs of dust in the air. Nucleation processes are important because in some regions of the atmosphere they determine the overall number of particles in the air which itself influences global climate and has implications for human health as breathing airborne particles has been shown to be detrimental to health. In order to study nucleation processes, it is necessary to be able to investigate extremely tiny particles that are associated with the start of the process. Current particle measurement instruments cannot see particles that are this small and consequently a device known as a "particle size magnifier" is needed, and in this project it is planned to purchase a recently developed particle size magnifier instrument and to test its suitability for studying the early stages of nucleation. If it proves successful, then the instrument would be used to study nucleation in an underground laboratory where the influence of cosmic rays on nucleation processes is minimal.

Atmospheric nucleation processes have a major influence upon the number concentration and ultimately the size distribution of airborne particulate matter. Although newly nucleated particles are extremely small, they grow by condensation and may ultimately enter the size range where they are active as cloud condensation nuclei. Consequently, after growth they can play a role in cloud formation and thereby influence global climate. They also contribute to the aerosol direct effect through light absorption and scattering. Such processes are included in global climate models but research is always striving to provide better descriptions of such processes with a base in fundamental knowledge. Airborne particulate matter also has well-recognised adverse effects upon human health. It is widely believed that nanoparticles are of higher toxicity per unit mass than large particles of the same material and consequently the nucleation process which leads to nanoparticle formation in the atmosphere is of interest as a contributor to the atmospheric nanoparticle fraction. Nucleation processes can lead to massively high particle number concentrations whose impact for human health is currently unknown. By enhancing the understanding of atmospheric nucleation processes at a fundamental level, this research will contribute to a more reliable predictions of future climate change and an enhanced understanding of the impact of particulate matter exposure on human health. The direct beneficiaries are therefore government departments (Defra, Department of Health, DECC) and international organisations (IPCC, WMO, WHO).