New particle formation at a rural site in the UK

P I Williams, H Coe, Martin Gallagher, K N Bower, K M Beswick, Thomas Choularton, Gordon Mcfiggans

    Research output: Chapter in Book/Report/Conference proceedingChapter


    Particle size distribution measurements were made at a coastal site in the UK. These are presented and the behaviour of recently formed ultra-fine particles is discussed. No ultrafine particles were observed in maritime air masses, however 3 to 7 nm particles were frequently observed at enhanced concentrations when the wind direction was from the land. Their formation was favoured at lower temperatures, when 1 ppbv or more of SO2 was present and in air masses that had not been aged extensively. On days when enhanced ultra-fine particle concentrations were observed, 3 nm particles increased sharply in the morning, approximately 30 to 90 minutes after the UV solar flux first increased. By early afternoon the ultra-fine particle concentration had returned to background levels. Rapid measurements of 5 nm particles showed no correlation with turbulence parameters, although the boundary layer mixing scales were similar to growth times of freshly nucleated particles to 5 nm diameter. However, ultra-fine particle concentrations do correlate with the availability of sulphuric acid vapour. A delay of approximately an hour between the increase of H2SO4 in the morning and a large increase in ultra-fine particle concentrations is due to the growth of particles to observable sizes, not the nucleation process itself. An analysis of the timescales for growth showed that coagulation may be important immediately the particles have nucleated but its effectiveness reduces as number concentration falls. Conversely, growth by condensation is initially slow due to the Kelvin effect but increases in importance as the particles reach observable sizes.
    Original languageEnglish
    Title of host publicationNucleation and Atmospheric Aerosols 2000
    Number of pages4
    Publication statusPublished - 2000

    Publication series

    NameAip Conference Proceedings


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