Formation and growth of atmospheric nanoparticles in the eastern Mediterranean: Results from long-term measurements and process simulations

Abstract

<p><strong>Abstract.</strong> Atmospheric New Particle Formation (NPF) is a common phenomenon all over the world. In this study we present the longest time series of NPF records in the eastern Mediterranean region by analyzing seven years of aerosol number size distribution data obtained with a mobility particle sizer. The measurements were performed at the Finokalia environmental research station on Crete, Greece during the period June 2008–June 2015. We found that NPF took place 29 % of the available days, undefined days were 26 % and non-event days 45 %. NPF is more frequent in April and May probably due to the biogenic activity and is less frequent in August and November. The NPF frequency increased during the measurement period, while particle growth rates showed a decreasing trend, indicating possible changes in the ambient sulfur dioxide concentrations in the area. Throughout the period under study, we frequently observed production of particles in the nucleation mode during night-time, a feature rarely observed in the ambient atmosphere. Nucleation mode particles had the highest concentration in winter, mainly because of the minimum sinks, and their average contribution to the total particle number concentration was 9 %. Nucleation mode particle concentrations were low outside periods of active NPF and growth, so there are hardly any other local sources of sub-25 nm particles. Additional atmospheric ion size distribution data simultaneously collected for more than two years period were also analyzed. Classification of NPF events based on ion measurements differed from the corresponding classification based on mobility spectrometer measurements, possibly indicating a different representation of local and regional NPF events between these two measurement data sets. We used MALTE-box model for a simulation case study of NPF in the eastern Mediterranean region. Monoterpenes contributing to NPF can explain a large fraction of the observed NPF events according to our model simulations. However the parametrization that resulted after sensitivity tests was significantly different from the one applied for the boreal environment.</p>

Regional New Particle Formation as Modulators of Cloud Condensation Nuclei and Cloud Droplet Number in the Eastern Mediterranean

“…Afterwards, particles continued to grow in size for several hours, exceeding 100nm in diameter at 21:30 LT. Following the methodology of the mode-fitting (Hussein et al, 405 2004;Kulmala et al, 2012) the nucleation mode particles exhibited a growth rate of 3.7 nm h -1 , while the formation rate value of particles in the nucleation mode was 2.0 cm -3 s -1 (Kulmala et al, 2012), which are well in the range of the representative values reported by Kalivitis et al (2018) at Finokalia site.…”

“…162 NPF episodes were recognized (Kalivitis et al, 2018) and the chemical composition of submicron particulate matter during these episodes was primarily composed of sulfate, 345 contributing on average by 39±8% to the total estimated PM1 mass as derived from the respective bulk PM10 24-h quartz fiber filters, and by 51±12% as derived from the ACSM highresolution measurements, respectively. Moreover, regarding the organic material the contribution was found to be in the order of 38±10% and 44±12%, respectively indicating that…”