Potential of four aquatic plant species to remove Co from contaminated water under changing experimental conditions.

This study aimed to compare the potential of Lemna minor, Spirodela sp., Eichhornia crassipes and Pistia stratiotes to remove Co from a realistic aquatic environment. Although all four plant species performed similarly well after 3 days of exposure to 50 kBq LCo, Lemna minor and Spirodela sp. came forward as having higher Co removal potential. This conclusion is, in first instance, based on the high Co removal percentage obtained after a short contact time (e.g. more than 95% could be removed after 6 h by Spirodela sp.). Additionally, Lemna minor and Spirodela sp. accumulated a high amount of Co per gram of biomass. For example, Lemna minor accumulated over three times more Co per gram of biomass compared to Pistia stratiotes and Eichhornia crassipes. Both plants also performed well in the pH range 5-9. We used Lemna minor to test the influence of the initial Co concentration (10, 50, 100 and 200 kBq LCo) on its phytoremediation capacity but no differences could be observed in removal percentage. In addition, it was shown that by optimising the initial amount of biomass, radioactive waste production can be minimised whilst maintaining high Co removal rates. Our study shows that these aquatic plants can be used for phytoremediation of Co from contaminated water and can be considered as a "green" addition or alternative for conventional remediation techniques.