The link between atmospheric radicals and newly formed particles at a spruce forest site in Germany
It has been claimed for more than a century that atmospheric new particle formation is primarily influenced by the presence of sulfuric acid. However, the activation process of sulfuric acid related clusters into detectable particles is still an unresolved topic. In this study we focus on the PARADE...
| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/14/10823/2014/acp-14-10823-2014.pdf |
| Summary: | It has been claimed for more than a century that atmospheric
new particle formation is primarily influenced by the presence of sulfuric
acid. However, the activation process of sulfuric acid related clusters into
detectable particles is still an unresolved topic. In this study we focus on
the PARADE campaign measurements conducted during August/September 2011 at
Mt Kleiner Feldberg in central Germany. During this campaign a set of
radicals, organic and inorganic compounds and oxidants and aerosol properties
were measured or calculated. We compared a range of organic and inorganic
nucleation theories, evaluating their ability to simulate measured particle
formation rates at 3 nm in diameter (<i>J</i><sub>3</sub>) for a variety of different
conditions. Nucleation mechanisms involving only sulfuric acid tentatively
captured the observed noon-time daily maximum in <i>J</i><sub>3</sub>, but displayed an
increasing difference to <i>J</i><sub>3</sub> measurements during the rest of the diurnal
cycle. Including large organic radicals, i.e. organic peroxy radicals
(RO<sub>2</sub>) deriving from monoterpenes and their oxidation products, in the
nucleation mechanism improved the correlation between observed and simulated
<i>J</i><sub>3</sub>. This supports a recently proposed empirical relationship for new
particle formation that has been used in global models. However, the best
match between theory and measurements for the site of interest was found for
an activation process based on large organic peroxy radicals and stabilised
Criegee intermediates (sCI). This novel laboratory-derived algorithm
simulated the daily pattern and intensity of <i>J</i><sub>3</sub> observed in the ambient
data. In this algorithm organic derived radicals are involved in activation
and growth and link the formation rate of smallest aerosol particles with OH
during daytime and NO<sub>3</sub> during night-time. Because the RO<sub>2</sub>
lifetime is controlled by HO<sub>2</sub> and NO we conclude that peroxy radicals and
NO seem to play an important role for ambient radical chemistry not
only with respect to oxidation capacity but also for the activation process
of new particle formation. This is supposed to have significant impact of
atmospheric radical species on aerosol chemistry and should be taken into
account when studying the impact of new particles in climate feedback cycles. |
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| ISSN: | 1680-7316 1680-7324 |