抄録
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 coreleased 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° for 1 hour. In addition, CO2 evolved was heated at 350° 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.
