Long-term variation of 14C concentration in atmospheric CO2 in Japan from 1991 to 2000

Prolonged production of 14C during the ~660 BCE solar proton event from Japanese tree rings

“…This feature is considered to reflect a seasonal variation of 14 C concentration in the atmosphere, i.e. 14 C concentrations during the period when latewoods ring formed (August-September) are higher than those of earlywoods (April-July), as stratosphere-troposphere exchange occurs strongly during spring/summer of the Northern Hemisphere 16,17 . Figure 2 shows a comparison of the annual Δ 14 C data sets for 670-646 BCE between the Choukai-Jindai cedar and the German oak rings previously published 11 .…”

Diverse Monitoring Approaches Reveal 14C Dispersion Pattern and Its Impact on the Environment around the Tokai Reprocessing Plant

“…It might, however, be reasonable to say that there was few, if any, 14 C dispersion separately detectable in observations in the >15 km area, when given that background CO 2 -14 C concentrations are themselves highly seasonally variable by more than 10 Bq kg-C À1 . 25) In contrast to this, the distributions of 14 C concentrations of Japanese mugwort samples collected in 1991 and 1992 clearly show the trace of the 14 C dispersion along southwestwards in the near-TRP area. The model calculations explain well the increased 14 C concentrations at the ST-3 site and its surroundings.…”

Relationship between Carbon-14 Concentrations in Tree-ring Cellulose and Atmospheric CO₂

“…The growing site of the tree was located about 1.6 km southeast of the sampling site of atmospheric CO 2 samples in the Ohkuwa area, in which temporal variation of 14 C concentrations in the atmospheric CO 2 samples collected every 10 days was measured during the period from April 1991 to December 2000. 17 The results of measurement for the tree expressed as the ∆ 14 C value are given in Table 1. The ∆ 14 C values in the table, after corrections for isotopic fluctuation using δ 13 C and radioactive decay of 14 C, were reproducible at ±10‰ or less, as described previously.…”

“…However, there has been little literature referring to the relationship between 14 C concentrations in tree-ring cellulose and atmospheric CO 2 in a narrow region up to date. [7][8][9] In our previous paper, 17 temporal variation of 14 C concentrations in atmospheric CO 2 samples collected every 10 days was measured in the Ohkuwa area of Kanazawa, Ishikawa prefecture, Japan (36.5°N, 136.7°E), where local contamination from fossil-fuel combustion can be disregarded, during the period from April 1991 to December 2000 to estimate the background level of environmental 14 C and to clarify the influence of air containing a large amount of 14 C-free fossil fuel CO 2 transported across the Sea of Japan from the Asian continent on the levels of environmental 14 C. The Ohkuwa area is located in the lowlands about 40 m above sea level in a rural region southeast out of the center of the city. There are no factories releasing a large amount of 14 C-free fossil fuel CO 2 in the surrounding area.…”

“…The growing site of the tree in the Tachi area was located about 1.6 km southeast of the sampling site of atmospheric CO 2 in the previous study, which was in a rice field of 1 km 2 in the Ohkuwa area. 17 There are no factories releasing large amounts of 14 C-free fossil fuel CO 2 in the surrounding area.…”