JMSSJ On-line, Vol. 52 (2004) No. 6, pp. 339-346
Preparation Method and Its Application for Determination of 14C of the Elemental Carbon in the Atmosphere
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    Yoshikuni NAKAJIMA, *a), d) Hideki WADA, b) Hiroyuki MATUZAKI, c) and Yoshimi SUZUKI b)

    *a) Graduate School of Science and Technology, Shizuoka University (836 Oya, Shizuoka 422-8529, Japan) b) Institute of Geosciences, Shizuoka University (836 Oya, Shizuoka 422-8529, Japan) c) Research Center of Nuclear Study and Technology, The University of Tokyo (2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan) d) Joetsu Environmental Science Center (1666 Shimo-monzen, Joetsu 942-0063, Japan)
We examined an analytical procedure for accurate determination of 14C concentrations in elemental carbon (EC) of an aerosol in the atmosphere. When carbon dioxide released by a combustion of EC is converted to graphite for 14C measurement with accelerator mass spectrometry (AMS), sulfur, nitrogen and halogens co-released impede the conversion to graphite. We examined an appropriate condition for effective formation of graphite on metallic Fe powder. We used Ag wire and Sulfix® for removing halogens and sulfur oxides and also used a reduced copper metal for reduction of nitrogen oxides to nitrogen gas. The following condition was used: 0.1 mm in diameter Ag wire of 100 cm and reduced copper metal of about 30 mg were added in a vycol tube with about 64 mg of CuO during the EC combustion at 900°C for 1 hour. In addition, CO2 evolved was heated at 350°C with Sulfix® of about 20 mg in a pyrex tube. We obtained a yield up to 70% during the process to convert EC to graphite. Δ14C values of EC in aerosol were measured for 3 sets of samples: two from mountainous areas of Ikawa and one from Mt. Norikura and an urban area, Shizuoka University. The Δ14C values of EC at Mt. Norikura, (ave. -636‰) were similar to those at Shizuoka University (ave. -717‰), while the Δ14C values in Ikawa (ave. -282‰ to ave. -349‰) were higher than those of the other sites.
Key words: Aerosol, Preparation methods for 14C measurement, Δ14C value, Atmospheric elemental carbon, Accelerator mass spectrometry
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