Rare Earth Elements in Atmospheric Aerosol Particles and their Sources
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概要
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Atmospheric concentrations of rare earth elements and their size distributions were measured at various sites in the Osaka area by applying the Andersen sampler and instrumental neutron activation analysis. Except La, rare earth elements measured were mostly in coarse particles above 1.5 μm in diameter. La was found to exist considerably in fine particles below 1.5 μm in diameter, and its recent size distribution shows rather the bimodal pattern at many sites. The ratio of La to Sm is almost always greater than 20 in fine particles. This ratio had been about 10 at least until 1987, and it seemed to change between 1979 and 1983. <BR> Various source samples such as soil and road dust, particles from coal-fired plants, oil-fired plants and oil refineries were analyzed elementally by instrumental neutron activation analysis, and concentration ratios of La to other rare earth elements and to V were derived from obtained analytical results. Concentration ratios of rare earth elements in soil and road dust and in particles from coal-fired plants were quite similar to their abundance ratios in crust. As for particles from oil-fired plants, concentrations of rare earth elements were generally lower than those in crustal particles, and the concentration pattern was also different from the crustal abundance pattern. The concentration ratio of La to V in particles from oil-fired plants was below 0.003. This is below one tenth at least when compared to the reported values in the United States. Particles from oil refineres such as the catalyst reclaiming tower and CO-boilers contained concentrated rare earth elements originating from the zeolite catalyst, and it is suggested that only about 100 ng/m<SUP>3</SUP> emissions from these plans may distort the concentration pattern of rare earth elemets to the similar degree observed in the Osaka area. <BR> Almost all rare earth elements in coarse particles seem to originate from crustal particles, because the concentration pattern of rare earth elements was quite similar to these from soil and read dust samples. On the other hand, contributions of crustal particles and emissions from oil-fired plans were small for fine particles, and the concentration pattern of rare earth elements suggested a probability of oil refinery emissios. Recently, Ce and La are consumed in large quantities in catalyst for automobiles. Judging from the present consequences, the distortion of concentration pattern of rare earth elements in fine particles is inferred to be mainly due to emissions from catalyst automobiles rather than those from oil refineris.
- 日本エアロゾル学会の論文
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- Rare Earth Elements in Atmospheric Aerosol Particles and their Sources