Stable Manganese and Fallout Radiomanganese in Animals from Irrigated Ecosystems of the Po Valley

Abstract

Stable manganese and radioactive manganese (Mn54 from fallout) were determined in samples of snakes, fishes, frogs, tadpoles, insects, worms, and molluscs from five sites in flooded rice fields and/or irrigated meadows of the Po Valley, Italy for a period of 1 year. Animals in the second trophic level generally contained more nuclides than the other organisms. High amounts of both stable and radiomanganese were noted for tadpoles, insects, and molluscs, with large variations in the quantities of nuclides based on the site of collection. Stable and radiomanganese concentrations in frogs and fishes were less and varied little from site to site. Fishes showed a decrease in the amount of the nuclides with a change of season. Tadpoles had consistently higher amounts of both stable and radiomanganese than the frogs, and there was a sharp decrease in nuclide concentration with the onset of metamorphosis. There was a reduction in concentration of both nuclides going through the direct three—step food chain from insects to frogs to the water snake. The various factors involved in stable and radiomanganese accumulation by aquatic organisms are discussed.