Abstract
Cloud condensation nuclei (CCN) activation of black carbon (BC) particles coated with different amounts of inorganic (sulfuric acid) and organic (levoglucosan or succinic acid) compounds was investigated. An evaporation-condensation method was used to produce coated BC particles, and the volume fractions of coating species were measured using the tandem differential mobility analyzer method. Furthermore, the CCN activation of the coated BC particles was measured using a differential mobility analyzer-CCN counter method. Coating with both aforementioned compounds engendered the activation of the BC particles as CCN at a supersaturation of 0.5%. Sulfuric acid coating was associated with the highest CCN activation fraction (= CCN/condensation nuclei), followed by levoglucosan coating and then succinic acid coating; this indicates that the water solubility of the coating compounds played a crucial role in the CCN activation of the coated BC particles. In general, the CCN activation fraction of the coated BC particles increased with the volume fraction of the coating species, but the manner of increase differed with the coating compounds and generation method. A premixed solution method was also used to produce mixed BC particles, and among the coating compounds, sulfuric acid was associated with the highest CCN activation fraction. For a given volume fraction, sulfuric-acid-coated BC particles produced using the premixed solution method showed a higher CCN activation fraction compared with those obtained using the evaporation-condensation method, and this was due to the presence of residual water in the sulfuric-acid-coated BC particles produced using the premixed solution method.
Highlights
Atmospheric aerosols, depending on their size and chemical composition, can be activated into cloud condensation nuclei (CCN) that provide a surface for water vapor condensation and facilitate cloud droplet nucleation under atmospheric supersaturation conditions (Cruz and Pandis, 1997; Martin, 2000)
Cloud condensation nuclei (CCN) activation of black carbon (BC) particles coated with different amounts of inorganic and organic compounds was investigated
The number size distributions of the BC particles coated with levoglucosan and succinic acid at different oil bath temperatures are presented in Figs. 2(b) and 2(c), respectively; the size distributions of the uncoated BC particles are displayed for comparison
Summary
Atmospheric aerosols, depending on their size and chemical composition, can be activated into cloud condensation nuclei (CCN) that provide a surface for water vapor condensation and facilitate cloud droplet nucleation under atmospheric supersaturation conditions (Cruz and Pandis, 1997; Martin, 2000). Cloud condensation nuclei (CCN) activation of black carbon (BC) particles coated with different amounts of inorganic (sulfuric acid) and organic (levoglucosan or succinic acid) compounds was investigated. A premixed solution method was used to produce mixed BC particles, and among the coating compounds, sulfuric acid was associated with the highest CCN activation fraction.
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