Browsing by Subject "particle formation"

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  • Myllys, Nanna; Ponkkonen, Tuomo; Chee, Sabrina; Smith, James (2020)
    The role of an oxidation product of trimethylamine, trimethylamine oxide, in atmospheric particle formation is studied using quantum chemical methods and cluster formation simulations. Molecular-level cluster formation mechanisms are resolved, and theoretical results on particle formation are confirmed with mass spectrometer measurements. Trimethylamine oxide is capable of forming only one hydrogen bond with sulfuric acid, but unlike amines, trimethylamine oxide can form stable clusters via ion-dipole interactions. That is because of its zwitterionic structure, which causes a high dipole moment. Cluster growth occurs close to the acid:base ratio of 1:1, which is the same as for other monoprotic bases. Enhancement potential of trimethylamine oxide in particle formation is much higher than that of dimethylamine, but lower compared to guanidine. Therefore, at relatively low concentrations and high temperatures, guanidine and trimethylamine oxide may dominate particle formation events over amines.
  • Määttänen, Anni; Merikanto, Joonas; Henschel, Henning; Duplissy, Jonathan; Makkonen, Risto; Ortega, Ismael K.; Vehkamäki, Hanna (2018)
    We have developed new parameterizations of electrically neutral homogeneous and ion-induced sulfuric acid-water particle formation for large ranges of environmental conditions, based on an improved model that has been validated against a particle formation rate data set produced by Cosmics Leaving OUtdoor Droplets (CLOUD) experiments at European Organization for Nuclear Research (CERN). The model uses a thermodynamically consistent version of the Classical Nucleation Theory normalized using quantum chemical data. Unlike the earlier parameterizations for H2SO4-H2O nucleation, the model is applicable to extreme dry conditions where the one-component sulfuric acid limit is approached. Parameterizations are presented for the critical cluster sulfuric acid mole fraction, the critical cluster radius, the total number of molecules in the critical cluster, and the particle formation rate. If the critical cluster contains only one sulfuric acid molecule, a simple formula for kinetic particle formation can be used: this threshold has also been parameterized. The parameterization for electrically neutral particle formation is valid for the following ranges: temperatures 165-400K, sulfuric acid concentrations 10(4)-10(13)cm(-3), and relative humidities 0.001-100%. The ion-induced particle formation parameterization is valid for temperatures 195-400K, sulfuric acid concentrations 10(4)-10(16)cm(-3), and relative humidities 10(-5)-100%. The new parameterizations are thus applicable for the full range of conditions in the Earth's atmosphere relevant for binary sulfuric acid-water particle formation, including both tropospheric and stratospheric conditions. They are also suitable for describing particle formation in the atmosphere of Venus.
  • Sebastian, Mathew; Kompalli, Sobhan Kumar; Kumar, Vasudevan Anil; Jose, Sandhya; Babu, S. Suresh; Pandithurai, Govindan; Singh, Sachchidanand; Hooda, Rakesh K.; Soni, Vijay K.; Pierce, Jeffrey R.; Vakkari, Ville; Asmi, Eija; Westervelt, Daniel M.; Hyvärinen, Antti-Pekka; Kanawade, Vijay P. (Copernicus Publ., 2022)
    Atmospheric chemistry and physics
    Atmospheric new particle formation (NPF) is a crucial process driving aerosol number concentrations in the atmosphere; it can significantly impact the evolution of atmospheric aerosol and cloud processes. This study analyses at least 1 year of asynchronous particle number size distributions from six different locations in India. We also analyze the frequency of NPF and its contribution to cloud condensation nuclei (CCN) concentrations. We found that the NPF frequency has a considerable seasonal variability. At the measurement sites analyzed in this study, NPF frequently occurs in March–May (pre-monsoon, about 21 % of the days) and is the least common in October–November (post-monsoon, about 7 % of the days). Considering the NPF events in all locations, the particle formation rate (JSDS) varied by more than 2 orders of magnitude (0.001–0.6 cm−3s−1) and the growth rate between the smallest detectable size and 25 nm (GRSDS-25 nm) by about 3 orders of magnitude (0.2–17.2 nm h−1). We found that JSDS was higher by nearly 1 order of magnitude during NPF events in urban areas than mountain sites. GRSDS did not show a systematic difference. Our results showed that NPF events could significantly modulate the shape of particle number size distributions and CCN concentrations in India. The contribution of a given NPF event to CCN concentrations was the highest in urban locations (4.3 × 103cm−3 per event and 1.2 × 103cm−3 per event for 50 and 100 nm, respectively) as compared to mountain background sites (2.7 × 103cm−3 per event and 1.0 × 103cm−3 per event, respectively). We emphasize that the physical and chemical pathways responsible for NPF and factors that control its contribution to CCN production require in situ field observations using recent advances in aerosol and its precursor gaseous measurement techniques.