Abstract
The impact of organic species which are present in the Earth’s atmosphere on the burst of new particles is critically important for the understanding of the molecular nature of atmospheric nucleation phenomena. Amines have recently been proposed as possible stabilizers of binary pre-nucleation clusters. In order to advance the understanding of atmospheric nucleation phenomena, a quantum-chemical study of hydrogen-bonded complexes of binary sulfuric acid-water clusters with methyl-, dimethyl- and trimethylamines representing common atmospheric organic species, vegetation products and laboratory impurities has been carried out. The thermochemical stability of the sulfuric acid-amines-water complexes was found to be higher than that of the sulfuric acid-ammonia-water complexes, in qualitative agreement with the previous studies. However, the enhancement in stability due to amines appears to not be large enough to overcome the difference in typical atmospheric concentrations of ammonia and amines. Further research is needed in order to address the existing uncertainties and to reach a final conclusion about the importance of amines for the atmospheric nucleation.
Highlights
Aerosol particles formed in the Earth’s atmosphere via nucleation [1,2] influence the Earth’s climate by affecting cloud properties and precipitation
The availability of data for ternary sulfuric acid-water-ammonia clusters computed at the same level of theory is a very important factor because the assessment of different nucleation pathways, which is based on the analysis of the reaction free energies computed using the same method, is clearly more legitimate than that based on the comparison of results obtained at different levels of theory [47]
The interaction of both amines with both the free and hydrated H2SO4 leads to the deprotonation of the sulfuric acid and transfer of the detached proton towards NH2 and NH groups of CH3NH2 and (CH3)2NH, respectively
Summary
Aerosol particles formed in the Earth’s atmosphere via nucleation [1,2] influence the Earth’s climate by affecting cloud properties and precipitation. They play an important role in global climate changes [3,4] and are responsible for the adverse public health impacts of airborne ultrafine particles, including various cardiovascular deceases, lung cancer and enhanced mortality rates [5,6,7]. The atmospheric nucleation process can be described schematically as nucleation of H2SO4-H2O-X. A perfectly logical question “What else is involved in the atmospheric nucleation?” has yet to be answered and a consensus on the dominant nucleation mechanism/. The somewhat excessive initial enthusiasm about the ternary homogeneous H2SO4-H2O-NH3 nucleation theory (THN) disappeared, when it was discovered that the widely used THN model [11]
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