Atmospheric New Particle Formation Enhanced by Organic Acids

Electronic structure calculations have been used to investigate possible gasphase decomposition pathways of α-hydroxyalkyl hydroperoxides (HHPs), an important source of tropospheric hydrogen peroxide and carbonyl compounds. The uncatalyzed as well as waterand acid-catalyzed decomposition of multiple HHPs have been examined at the M06-2X/augcc-pVTZ level of theory. The calculations indicate that, compared to an uncatalyzed or watercatalyzed reaction, the free-energy barrier of an acid-catalyzed decomposition leading to an aldehyde or ketone and hydrogen peroxide is dramatically lowered. The calculations also find a direct correlation between the catalytic effect of an acid and the distance separating its hydrogen acceptor and donor sites. Interestingly, the catalytic effect of an acid on the HHP decomposition resulting in the formation of carboxylic acid and water is relatively much smaller. Moreover, since the free-energy barrier of the acid-catalyzed aldehyde-or ketoneforming decomposition is ∼25% lower than that required to break the O−OH linkage of the HHP leading to the formation of hydroxyl radical, these results suggest that HHP decomposition is likely not an important source of tropospheric hydroxyl radical. Finally, transition state theory estimates indicate that the effective rate constants for the acid-catalyzed aldehyde-or ketone-forming HHP decomposition pathways are 2− 3 orders of magnitude faster than those for the water-catalyzed reaction, indicating that an acid-catalyzed HHP decomposition is kinetically favored as well.

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“…The catalytic effect of incorporating organic acids into sulfuric acid aerosol models has been verified through laboratory experiments. 64 …”

Section: Resultsmentioning

confidence: 99%

Role of Tunable Acid Catalysis in Decomposition of α-Hydroxyalkyl Hydroperoxides and Mechanistic Implications for Tropospheric Chemistry

et al. 2014

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“…These species are products of photochemical oxidation of volatile organic precursors on these pre-existing nuclei (O'Dowd et al, 1999;Kulmala et al, 2004). In fact, recent studies by Zhang et al (2004) showed that nucleation rates of sulfuric acid are greatly increased in the presence of organic acids (including products of atmospheric photochemical reactions), by forming unusually stable organic-sulfuric acid complexes, thereby reducing the nucleation barrier of sulfuric acid. It is interesting to note in our field measurements that summertime levels of ultrafine particles at source sites, such as long Beach and USC peaked in midday (i.e., noon to 1300), whereas ultrafine PM numbers peak slightly later (i.e., between 1500 and 1600) in the inland receptor sites.…”

Section: Discussionmentioning

confidence: 99%

Seasonal and spatial trends in particle number concentrations and size distributions at the children's health study sites in Southern California

Singh

Phuleria

Bowers

et al. 2005

J Expo Sci Environ Epidemiol

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“…For example, theoretical calculations and observations [Barsanti et al, 2009;Kurten et al, 2008;Smith et al, 2008Smith et al, , 2010 have shown that amines may be involved in J is nucleation rate calculated from PARGAN (that is, J PARGAN ), C is preexponential factor, and P is power, for J = C[H aerosol nucleation in the atmosphere. Laboratory studies also showed that aromatic acids may increase nucleation rates similarly to NH 3 [Zhang et al, 2004] and biogenic organic compounds can enhance aerosol growth rates of H 2 SO 4 aerosols [Zhang et al, 2009].…”

Section: Indirect Chemical Information Of Newly Formed Particlesmentioning

confidence: 99%

Correlation of aerosol nucleation rate with sulfuric acid and ammonia in Kent, Ohio: An atmospheric observation

Erupe¹,

Benson²,

Li³

et al. 2010

J. Geophys. Res.

115

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[1] New particle formation (NPF) occurs in various atmospheric environments, and these newly formed particles have the potential to grow to cloud condensation nuclei. But at present it is unclear which chemical species are involved in aerosol nucleation and growth, in part because there are only a limited number of simultaneous measurements of aerosol precursors and aerosol size distributions. Observations of ambient aerosol size distributions, sulfuric acid, and ammonia were made for over a year in Kent, Ohio, a relatively less polluted continental environment. Particle sizes in the diameter range from 3 to 1000 nm were measured continuously through the whole year, while sulfuric acid and ammonia were measured seasonally with two chemical ionization mass spectrometers. Strong NPF events were more frequently found during the spring and fall and less frequently during the summer and winter. The median of measured sulfuric acid was higher in spring (5.2 × 10 6 cm −3 ) and summer (2.9 × 10 6 cm −3 ) than in winter (6 × 10 5 cm −3 ) and fall (5 × 10 5 cm −3 ). We have used the inverse model Particle Growth and Nucleation to derive aerosol nucleation and growth rates from the measured aerosol size distributions. Nucleation rates derived during the NPF events ranged from 1.4 to 12.9 cm −3 s −1 and were proportional to the measured sulfuric acid concentration with a power of 0.6-2.3. Our results show that sulfuric acid is an important aerosol nucleation precursor, but only a small fraction of the aerosol growth rates could be explained by the condensation of sulfuric acid alone. Ammonia mixing ratios did not have a diurnal trend but had some seasonal variations, higher in spring than in fall and winter, typically at sub-ppbv level; aerosol nucleation rates did not show a clear correlation with ammonia at least at this sub-ppbv level, mostly because the ammonia mixing ratios were nearly constant. Our observations also indicate that the role that ammonia plays in aerosol nucleation is more complicated than is currently understood by the aerosol nucleation theories.Citation: Erupe, M. E., et al. (2010), Correlation of aerosol nucleation rate with sulfuric acid and ammonia in Kent, Ohio: An atmospheric observation,

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Atmospheric New Particle Formation Enhanced by Organic Acids

Cited by 766 publications

References 31 publications

Role of Tunable Acid Catalysis in Decomposition of α-Hydroxyalkyl Hydroperoxides and Mechanistic Implications for Tropospheric Chemistry

Role of Tunable Acid Catalysis in Decomposition of α-Hydroxyalkyl Hydroperoxides and Mechanistic Implications for Tropospheric Chemistry

Seasonal and spatial trends in particle number concentrations and size distributions at the children's health study sites in Southern California

Correlation of aerosol nucleation rate with sulfuric acid and ammonia in Kent, Ohio: An atmospheric observation

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