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A phenomenology of new particle formation (NPF) at 13 European sites
2021, Bousiotis, Dimitrios, Pope, Francis D., Beddows, David C. S., Dall'Osto, Manuel, Massling, Andreas, Nøjgaard, Jakob Klenø, Nordstrøm, Claus, Niemi, Jarkko V., Portin, Harri, Petäjä, Tuukka, Perez, Noemi, Alastuey, Andrés, Querol, Xavier, Kouvarakis, Giorgos, Mihalopoulos, Nikos, Vratolis, Stergios, Eleftheriadis, Konstantinos, Wiedensohler, Alfred, Weinhold, Kay, Merkel, Maik, Tuch, Thomas, Harrison, Roy M.
New particle formation (NPF) events occur almost everywhere in the world and can play an important role as a particle source. The frequency and characteristics of NPF events vary spatially, and this variability is yet to be fully understood. In the present study, long-term particle size distribution datasets (minimum of 3 years) from 13 sites of various land uses and climates from across Europe were studied, and NPF events, deriving from secondary formation and not traffic-related nucleation, were extracted and analysed. The frequency of NPF events was consistently found to be higher at rural background sites, while the growth and formation rates of newly formed particles were higher at roadsides (though in many cases differences between the sites were small), underlining the importance of the abundance of condensable compounds of anthropogenic origin found there. The growth rate was higher in summer at all rural background sites studied. The urban background sites presented the highest uncertainty due to greater variability compared to the other two types of site. The origin of incoming air masses and the specific conditions associated with them greatly affect the characteristics of NPF events. In general, cleaner air masses present higher probability for NPF events, while the more polluted ones show higher growth rates. However, different patterns of NPF events were found, even at sites in close proximity (<ĝ€¯200ĝ€¯km), due to the different local conditions at each site. Region-wide events were also studied and were found to be associated with the same conditions as local events, although some variability was found which was associated with the different seasonality of the events at two neighbouring sites. NPF events were responsible for an increase in the number concentration of ultrafine particles of more than 400ĝ€¯% at rural background sites on the day of their occurrence. The degree of enhancement was less at urban sites due to the increased contribution of other sources within the urban environment. It is evident that, while some variables (such as solar radiation intensity, relative humidity, or the concentrations of specific pollutants) appear to have a similar influence on NPF events across all sites, it is impossible to predict the characteristics of NPF events at a site using just these variables, due to the crucial role of local conditions. © Author(s) 2021.
Changes in black carbon emissions over Europe due to COVID-19 lockdowns
2021, Evangeliou, Nikolaos, Platt, Stephen M., Eckhardt, Sabine, Lund Myhre, Cathrine, Laj, Paolo, Alados-Arboledas, Lucas, Backman, John, Brem, Benjamin T., Fiebig, Markus, Flentje, Harald, Marinoni, Angela, Pandolfi, Marco, Yus-Dìez, Jesus, Prats, Natalia, Putaud, Jean P., Sellegri, Karine, Sorribas, Mar, Eleftheriadis, Konstantinos, Vratolis, Stergios, Wiedensohler, Alfred, Stohl, Andreas
Following the emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) responsible for COVID-19 in December 2019 in Wuhan (China) and its spread to the rest of the world, the World Health Organization declared a global pandemic in March 2020. Without effective treatment in the initial pandemic phase, social distancing and mandatory quarantines were introduced as the only available preventative measure. In contrast to the detrimental societal impacts, air quality improved in all countries in which strict lockdowns were applied, due to lower pollutant emissions. Here we investigate the effects of the COVID-19 lockdowns in Europe on ambient black carbon (BC), which affects climate and damages health, using in situ observations from 17 European stations in a Bayesian inversion framework. BC emissions declined by 23 kt in Europe (20 % in Italy, 40 % in Germany, 34 % in Spain, 22 % in France) during lockdowns compared to the same period in the previous 5 years, which is partially attributed to COVID-19 measures. BC temporal variation in the countries enduring the most drastic restrictions showed the most distinct lockdown impacts. Increased particle light absorption in the beginning of the lockdown, confirmed by assimilated satellite and remote sensing data, suggests residential combustion was the dominant BC source. Accordingly, in central and Eastern Europe, which experienced lower than average temperatures, BC was elevated compared to the previous 5 years. Nevertheless, an average decrease of 11 % was seen for the whole of Europe compared to the start of the lockdown period, with the highest peaks in France (42 %), Germany (21 %), UK (13 %), Spain (11 %) and Italy (8 %). Such a decrease was not seen in the previous years, which also confirms the impact of COVID-19 on the European emissions of BC.