137Cs and K annual fluxes in a cropland and forest ecosystems twenty-four years after the Chernobyl accident

Biological cycles of the Chernobyl originated cesium-137 (Cs-137, radiocesium) and the natural potassium (K) in oak, birch, and pine forest, and wheat cropland in Russian Federation, approximately 500 km northeast of the Chernobyl Nuclear Power Plant, were subject to a multiyear monitoring. By 2010, the annual return of Cs-137 from forest vegetation to the soil in dead tree components still exceeds its annual accumulation in the tree phytomass by a factor of 4-6, apparently due to residual surface contamination in the external bark and the ongoing process of tree stand decontamination following the initial fallout. In the cropland, both ascending and descending fluxes of Cs-137 are close to the steady state. The annual accumulation of Cs-137 in the tree biomass was the highest in the oak forest and the lowest in the pine forest. The annual K accumulation was the highest in the cropland and the lowest in the pine forest.