Radiocarbon and radiocesium in litter fall at Kawamata, ~ 45 km NW from the Fukushima Dai-ichi nuclear power plant (Japan)

Radiocarbon and radiocesium were measured on litter fractions (LF) collected on November 19th, 2011 at 40 km NW of the FDNPP. The 137Cs concentration is much higher in the lower fraction LFb at 226,650 ± 170 Bq kg−1 than in the upper fraction LFa at 7290 ± 40 Bq kg−1. From leaf-air 14C comparison, no excess 14C due to the FDNPP accident is detected in LFa deposited in 2010–2011. A significant 14C difference of 1.4% exists between pine needles and deciduous leaves in LFb, which may be due either to post-depositional processes or to a turnover time of 0.5–1 year of stored carbon for deciduous leaves growth.