New particle formation and sub-10 nm size distribution measurements during the A-LIFE field experiment in Paphos, Cyprus

• Main Authors: S. Brilke, N. Fölker, T. Müller, K. Kandler, X. Gong, J. Peischl, B. Weinzierl, P. M. Winkler
• Format: Article
• Language: English
• Published: Copernicus Publications 2020-05-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://www.atmos-chem-phys.net/20/5645/2020/acp-20-5645-2020.pdf

<p>Atmospheric particle size distributions were measured in Paphos, Cyprus, during the A-LIFE (<i>a</i>bsorbing aerosol layers in a changing climate: ageing, <i>life</i>time and dynamics) field experiment from 3 to 30 April 2017. The newly developed differential mobility analyser train (DMA-train) was deployed for the first time in an atmospheric environment for the direct measurement of the nucleation mode size range between 1.8 and 10&thinsp;nm diameter. The DMA-train set-up consists of seven size channels, of which five are set to fixed particle mobility diameters and two additional diameters are obtained by alternating voltage settings in one DMA every 10&thinsp;s. In combination with a conventional mobility particle size spectrometer (MPSS) and an aerodynamic particle sizer (APS) the complete atmospheric aerosol size distribution from 1.8&thinsp;nm to 10&thinsp;<span class="inline-formula">µ</span>m was covered. The focus of the A-LIFE study was to characterize new particle formation (NPF) in the eastern Mediterranean region at a measurement site with strong local pollution sources. The nearby Paphos airport was found to be a large emission source for nucleation mode particles, and we analysed the size distribution of the airport emission plumes at approximately 500&thinsp;m from the main runway. The analysis yielded nine NPF events in 27 measurement days from the combined analysis of the DMA-train, MPSS and trace gas monitors. Growth rate calculations were performed, and a size dependency of the initial growth rate (<span class="inline-formula">&lt;10</span>&thinsp;nm) was observed for one event case. Fast changes of the sub-10&thinsp;nm size distribution on a timescale of a few minutes were captured by the DMA-train measurement during early particle growth and are discussed in a second event case. In two cases, particle formation and growth were detected in the nucleation mode size range which did not exceed the 10&thinsp;nm threshold. This finding implies that NPF likely occurs more frequently than estimated from studies where the lower nanometre size regime is not covered by the size distribution measurements.</p>