Cs 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, 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 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 are close to the steady state.