1. Formation and growth of atmospheric nanoparticles in the eastern Mediterranean : results from long-term measurements and process simulationsNikos Kalivitis, Veli-Matti Kerminen, Giorgos Kouvarakis, Iasonas Stavroulas, Evaggelia Tzitzikalaki, Panayiotis Kalkavouras, Nikos Daskalakis, Stelios Myriokefalitakis, Aikaterini Bougiatioti, Hanna E. Manninen, 2019, original scientific article Abstract: 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 10 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 2018. We found that NPF took place
on 27 % of the available days, undefined days were 23 % and non-event
days 50 %. NPF is more frequent in April and May probably due to the
terrestrial biogenic activity and is less frequent in August. Throughout the
period under study, nucleation was observed also during the night. Nucleation
mode particles had the highest concentration in winter and early spring,
mainly because of the minimum sinks, and their average contribution to the
total particle number concentration was 8 %. 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
2 years were also analyzed. Classification of NPF events based on ion
spectrometer measurements differed from the corresponding classification
based on a mobility spectrometer, possibly indicating a different
representation of local and regional NPF events between these two measurement
data sets. We used the MALTE-Box model
for simulating a 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 adjusted
parameterization resulting from our sensitivity tests was significantly
different from the initial one that had been determined for the boreal
environment.
Keywords: particles, number size distributions, new particle formation, regional background, SMPS, Eastern Mediterannean
Published in RUNG: 10.05.2024; Views: 139; Downloads: 2
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2. Assessment of the COVID-19 lockdown effects on spectral aerosol scattering and absorption properties in Athens, GreeceDimitris G. Kaskaoutis, Georgios Grivas, Eleni Liakakou, Nikos Kalivitis, Giorgos Kouvarakis, Iasonas Stavroulas, Panayiotis Kalkavouras, Pavlos Zarmpas, Umesh Chandra Dumka, Evangelos Gerasopoulos, Nikolaos Mihalopoulos, 2021, original scientific article Abstract: COVID-19 is evolving into one of the worst pandemics in recent history, claiming a death toll of over 1.5 million as of December 2020. In an attempt to limit the expansion of the pandemic in its initial phase, nearly all countries imposed restriction measures, which resulted in an unprecedented reduction of air pollution. This study aims to assess the impact of the lockdown effects due to COVID-19 on in situ measured aerosol properties, namely spectral-scattering (bsca) and absorption (babs) coefficients, black carbon (BC) concentrations, single-scattering albedo (SSA), scattering and absorption Ångström exponents (SAE, AAE) in Athens, Greece. Moreover, a comparison is performed with the regional background site of Finokalia, Crete, for a better assessment of the urban impact on observed differences. The study examines pre-lockdown (1–22 March 2020), lockdown (23 March–3 May 2020) and post-lockdown (4–31 May 2020) periods, while the aerosol properties are also compared with a 3–4 year preceding period (2016/2017–2019). Comparison of meteorological parameters in Athens, between the lockdown period and respective days in previous years, showed only marginal variation, which is not deemed sufficient in order to justify the notable changes in aerosol concentrations and optical properties. The largest reduction during the lockdown period was observed for babs compared to the pre-lockdown (−39%) and to the same period in previous years (−36%). This was intensified during the morning traffic hours (−60%), reflecting the large decrease in vehicular emissions. Furthermore, AAE increased during the lockdown period due to reduced emissions from fossil-fuel combustion, while a smaller (−21%) decrease was observed for bsca along with slight increases (6%) in SAE and SSA values, indicating that scattering aerosol properties were less affected by the decrease in vehicular emissions, as they are more dependent on regional sources and atmospheric processing. Nighttime BC emissions related to residential wood-burning were slightly increased during the lockdown period, with respect to previous-year means. On the contrary, aerosol and pollution changes during the lockdown period at Finokalia were low and highly sensitive to natural sources and processes.
Keywords: COVID-19, traffic, aerosol scattering, absorption, SSA, Greece
Published in RUNG: 10.05.2024; Views: 124; Downloads: 3
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