Long-term transfer of global fallout ¹³⁷Cs to cow's milk in Iceland

The aim of this study was to provide improved information on the long-term transfer of global nuclear weapons (137)Cs fallout to cow's milk in Iceland many years after deposition. The spatial variation in deposition was confirmed to be explained by precipitation. Soil samples showed a significant difference in (137)Cs deposition density between the main agricultural areas, with the South having the highest values, then the West and North and the lowest in the Northeast. There was no significant difference between the effective half-lives in (137)Cs activity concentrations in milk and milk powder from the main dairies in Iceland based on data for milk from 1990 to 2007 and for milk powder from 1986 to 2007. There was, however, a significant difference between the effective half-lives obtained for these two regions, 13.5 years for the Northern and 10.5 years for the Southern regions. These half-lives for global fallout are longer than those previously reported for similar time periods in other Arctic areas. The transfer of (137)Cs to cow's milk was quantified for different agricultural regions using aggregated transfer coefficients (T (ag)) for the period of peak global fallout soil inventory in 1965-1967. The values ranged from 2.8 × 10(-3) to 10.6 × 10(-3) m(2) kg(-1). By 2001-2004, the T (ag) values had only declined, in the main agricultural areas, to 0.6 × 10(-3)-1.0 × 10(-3) m(2) kg(-1). Long-term transfer rates to milk many years after deposition were high in Iceland compared with most other reported data. The transfer is potentially relevant for some of the contaminated areas around the Fukushima Nuclear Power Plant after the accident in March 2011 since limited information is available on uptake from Andosols and associated effective half-lives.