Improved technique for measuring the size distribution of black carbon particles in liquid water

Tatsuhiro Mori, Nobuhiro Moteki, Sho Ohata, Makoto Koike, Kumiko Goto-Azuma, Yuzo Miyazaki, Yutaka Kondo

Research output: Contribution to journalArticlepeer-review

26 Citations (Scopus)

Abstract

We developed an improved technique for measuring the size distribution of black carbon (BC) particles suspended in liquid water to facilitate quantitative studies of the wet deposition of BC. The measurement system, which consists of a nebulizer and a single-particle soot photometer, incorporates two improvements into the system that we developed earlier. First, we extended the upper limit of the detectable BC size from 0.9 μm to about 4.0 μm by modifying the photo-detector for measuring the laser-induced incandescence signal. Second, we introduced a pneumatic nebulizer (Marin-5) with a high extraction efficiency (∼50.0%) that was independent of particle diameter up to 2.0 μm. For BC mass concentrations less than 70 μg L-1, we experimentally showed that the diameters of BC particles did not appreciably change during the Marin-5 extraction process, consistent with theoretical calculations. Finally, we demonstrated by laboratory experiments that the size distributions of ambient BC particles changed little during their growth into cloud droplets under supersaturation of water vapor. Using our improved system, we measured the size distributions of BC particles simultaneously in air and rainwater in Tokyo during summer 2014. We observed that the size distributions of BC particles in rainwater shifted to larger sizes compared with those observed in ambient air, indicating that larger BC particles in air were removed more efficiently by precipitation.

Original languageEnglish
Pages (from-to)242-254
Number of pages13
JournalAerosol Science and Technology
Volume50
Issue number3
DOIs
Publication statusPublished - 2016 Mar 3
Externally publishedYes

ASJC Scopus subject areas

  • Environmental Chemistry
  • Materials Science(all)
  • Pollution

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