Phytoremediation of ¹³⁷Cs, ⁶⁰Co, ²⁴¹Am, and ²³⁹Pu from aquatic solutions using Chlamydomonas reinhardtii, Scenedesmus obliquus, and Chlorella vulgaris

Abstract

This work is focused on the phytoremediation of radionuclides using eukaryotic green microalgae Chlamydomonas reinhardtii, Scenedesmus obliquus, and Chlorella vulgaris. This study highlights the potential use of microalgae in the process of phytoremediation in polluted aquatic solutions due to the unique cellular mechanism of uptake of different radionuclides. The kinetics of radionuclide removal from the samples was described according to the first-order kinetics and expressed by the rate constant k and calculated for each microalga at the most suitable pH. The activity of ¹³⁷Cs and ⁶⁰Co was measured in the presence of S. obliquus or C. reinhardtii and the activity of ²⁴¹Am and ²³⁹Pu was measured in the presence of C. vulgaris. A significant decrease of activity of ¹³⁷Cs was observed using C. reinhardtii with a rate constant of 2.4 Bq min⁻¹ and S. obliquus after 3 h of incubation at pH 7 with rate constant of 2.5 Bq min⁻¹. Chlorella vulgaris was able after 3 h of incubation to remove ²⁴¹Am and ²³⁹Pu up to 90 and 70% in aquatic solutions at pH 1.7 and pH 1.5, with rate constants of 4.4 mBq min⁻¹ and 2.8 × 10⁻² mBq min⁻¹, respectively.

Novelty statement

Ecologically suitable methods for the decontamination of liquid radioactive waste or radioactively contaminated areas are becoming more and more important due to the pollution of the planet. We believe that phytoremediation of radionuclides using microalgae is one of the optimal ecological methods to decontamination of radioactive waste. Microalgae as unicellular organisms have a number of advantages over the other organisms used in bioremediation—high level of tolerance to the environment, fast growth rates, high tolerance to various pH levels, etc. In this study, we used 3 different strains of microalgae for phytoremediation of various radionuclides (¹³⁷Cs, ⁶⁰Co, ²⁴¹Am, and ²³⁹Pu). This research was focused on ex situ phytoremediation of radionuclides using microalgae at various pH levels of radioactively contaminated solutions. Due to the ability of microalgae to adapt to sometimes even extreme pH values, this research may be interesting for many institutions and researchers dealing with more environmentally friendly methods of decontamination of radioactive waste.

Keywords:

• Microalgae
• phytoremediation
• Cs-137
• Co-60
• Am-241
• Pu-239