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Geochemical Journal
Geochemical Journal An open access journal for geochemistry
Published for geochemistry community from Geochemical Society of Japan.
Article

Characterization of hydrocarbons in aerosols and investigation of biogenic sources as a carrier of radiocesium isotopes

Mayuko Nakagawa, Keita Yamada, Sakae Toyoda, Kazuyuki Kita, Yasuhito Igarashi, Shingo Komatsu, Kentaro Yamada, Naohiro Yoshida
Geochemical Journal, Vol. 52, No. 2, P. 163-172, 2018

ABSTRACT

In this study, the potential natural sources of secondary radiocesium isotope (134Cs and 137Cs) emissions were investigated, with a focus on n-alkanes, a characteristic bioaerosol compound. Monitoring was performed to obtain a time series of aerosol, samples, from winter 2013 to summer 2014, and size-resolved aerosol samples in 2012 and 2014. Samples were collected from the area heavily contaminated after the Fukushima Daiichi Nuclear Power Plant accident in March 2011. A correlation analysis of radiocesium, n-alkanes, and black carbon concentrations was performed to identify the contributions of aerosols from biogenic and anthropogenic sources. Biogenic n-alkanes exhibited similar concentration ranges except for spring 2014. The continuous input of biogenic n-alkanes is characteristic of a sampling site surrounded by forest, where pollen dispersion increased the concentration of biogenic n-alkanes in spring 2014. On the other hand, anthropogenic n-alkane concentrations were significantly increased in spring and summer 2014 (>50 ng/m3), compared with those prior to winter 2014 (<20 ng/m3). This anthropogenic n-alkane increase represents the beginning of reconstruction near the area. The carbon preference index (CPI) clearly showed biogenic n-alkanes with coarse-sized particles (CPI > 3), and more anthropogenic n-alkanes were contained in fine particle aerosols. Our results showed that radiocesium and biogenic n-alkane concentrations in seasonal and size-resolved aerosol samples have a partially positive correlation, which supports the hypothesis that the secondary emissions of radionuclides occurred in the forested areas.

KEYWORDS

secondary radioactive emission, radiocesium, n-alkane, biogenic sources, aerosols

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