Differentiation between chemo- and radiotoxicity of 137Cs and 60Co on Lemna minor

Abstract

The uptake and effects of stable Cs and Co on L.minor were extensively studied, together with the effects of gamma radiation using a ¹³⁷Cs or ⁶⁰Co source. Innovative is that we combined external irradiation (from ¹³⁷Cs or ⁶⁰Co sources) with the direct uptake of certain amounts of stable Cs or Co to simulate the impact of the same mass of a radioisotope compared with that of the stable element. Such approach allows to differentiate between chemo- and radiotoxicity of ¹³⁷Cs or ⁶⁰Co, permitting to study the ¹³⁷Cs and ⁶⁰Co uptake by L. minor without using high concentrations of these elements in solution. Our results indicate that radiotoxicity of both ¹³⁷Cs and ⁶⁰Co has a greater importance compared to their chemotoxicity. This was also supported by the independent action and concentration addition concepts. Both concepts resulted in a good prediction of the dose-response curve of the combination exposure. The maximal removal of ¹³⁷Cs or ⁶⁰Co per gram dry matter of L. minor was lower compared with the removal of the corresponding stable isotope. The toxicity of ⁶⁰Co was higher compared to ¹³⁷Cs based on EC₅₀ values and uptake data. With respect to the effects on photosynthetic pigments, starch and soluble sugars contents, only starch increased in a concentration- and dose-dependent manner.