Yoshiki Miyata

Difference in radiocarbon ages of carbonized material from the inner and outer surfaces of pottery from a wetland archaeological site.

AMS (Accelerator Mass Spectrometry) radiocarbon dates for eight potsherds from a single piece of pottery from a wetland archaeological site indicated that charred material from the inner pottery surfaces (5052 ± 12 BP; N = 5) is about 90 14C years older than that from the outer surfaces (4961 ± 22 BP; N = 7). We considered three possible causes of this difference: the old wood effect, reservoir effects, and diagenesis. We concluded that differences in the radiocarbon ages between materials from the inner and outer surfaces of the same pot were caused either by the freshwater reservoir effect or by diagenesis. Moreover, we found that the radiocarbon ages of carbonized material on outer surfaces (soot) of pottery from other wetland archaeological sites were the same as the ages of material on inner surfaces (charred food) of the same pot within error, suggesting absence of freshwater reservoir effect or diagenesis.

Marine Reservoir Effects Deduced from 14C Dates on Pottery Residues, Bones, and Molluskan Shells from the Hamanaka 2 Archaeological Site, Rebun Island, Hokkaido, Japan

This article investigates the marine reservoir effects from apparent age differences among molluskan shells, birds, and sea mammals from the Hamanaka 2 archaeological site, Rebun Island, Japan, which was occupied during the latter half of the Late Jomon period (1300−1200 cal BC). The radiocarbon ages were younger in the order of charred wood 14 C yr. ΔR values of bone collagen for Alcidae (a family of seabirds) and Japanese sea lion were 289 and 389 14 C yr, respectively. A ΔR value of 447±55 14 C yr was obtained on charred material from the inner surfaces of potsherds at Hamanaka 2. The different reservoir effects relate to the differences in the diets or habitats of the shellfish, sea lion, and seabird remains at the site.

Accumulation of accident-derived radiocesium in lake and coastal sediments at 300–700 km distance from Fukushima area

The accumulation of accident-derived radiocesium was investigated in nine water bodies located 300-700 km from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP). (134)Cs from the accident was detected in surface sediment of five water bodies. The (134)Cs concentration, corrected to the time of the accident in 2011, was generally lower than that of (137)Cs, and its spatial pattern does not fully correspond to that of (137)Cs. These results suggest that radiocesium derived from both FDNPP and past global fallout can be separately observed and that the contributions of both sources are non-uniform within these sites. The (134)Cs inventory in surface sediments is smaller than its deposition, suggesting that almost all deposited (134)Cs remains within the catchment and/or a part has been discharged from the saline and brackish water bodies.

Radiocesium in seawater, sediments, and marine megabenthic species in coastal waters off Fukushima in 2012–2016, after the 2011 nuclear disaster

In bottom-sediment samples collected in 2012 from a coastal strip (∼30 km × 120 km) off the Fukushima Daiichi Nuclear Power Plant (FDNPP), radiocesium activity concentrations were generally higher south of the FDNPP, with high activity concentration patches in the north. In periodic surveys conducted at nearshore sites during 2012-2016, no clear temporal trends were observed in radiocesium activity concentrations in seawater or bottom sediment, and activity concentrations were higher in fish than in invertebrates. During 2012-2014, radiocesium activity concentrations tended to decrease in fish, but during 2012-2013 in the south, some increases were observed. Radiocesium activity concentrations were significantly higher in some fish (e.g., Okamejei kenojei) directly offshore and south of the FDNPP than in the north. Activity concentrations in fish stomach contents were significantly correlated with those in muscle tissue, suggesting that the consumption of contaminated prey contributed greatly to radiocesium contamination in demersal fish.