Morphological and light-absorption characteristics of individual BC particles collected in an urban seaside area at Tokaimura, eastern central Japan

To observe surface morphology and light-absorption property of different black carbon (BC) particles, different-sized aerosols were collected in Tokaimura (36.27°N, 140.36°E), an urban seaside area of eastern central Japan, using a high-volume Andersen type sampler during a whole year (Jan. to Dec. in 2004). The morphology of individual BC particle separated from different-sized aerosols was observed with Scanning Electron Microscope with Energy Dispersive X-ray Spectrometer (SEM-EDX) and four types of morphology were observed: 50 nm spherical particles, micrometer-sized plates with homogeneous surfaces, micrometer-sized spherical particles with homogeneous surfaces and micrometer-sized spherical particles with small holes on surfaces. The light-absorption property of BC particles with different morphology has been determined by infrared spectrometry (IRS) with a photoacoustic technique in a region of 400-4000 wavenumbers (cm^{- 1}). All morphology BC particles showed a strong light-absorption during 500-3000 wavenumbers (cm^{- 1}) with two strong broad peaks in 750-1100 and 1200-2200 wavenumbers (cm^{- 1}), implying that all morphology BC particles can absorb a significant part of thermal infrared emitted from the earth (wavelength 4000-50,000 nm). The seasonal variation and the size-distribution of aerosols and its chemical components (e.g. C, Na, Cl, NH₄⁺, NO₃^-, SO₄^2-, Al, Ca, Mg and Fe) were also measured in this study. More than 55% of non-inorganic carbon (OC + BC) in the atmosphere was detected in the aerosols with a size smaller than 1.1 μm and the concentration of non-inorganic carbon in the atmosphere showed only a faint variation during a whole year, although the concentrations of total aerosols and its chemical components exhibited a distinct variation.