Kinetics of cadmium uptake by green algae |
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| Authors: | Joyce E Sloof Aranka Viragh Bart Van Der Veer |
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| Institution: | 1. Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629, JB, Delft, The Netherlands
2. Faculty of Civil Engineering, Delft University of Technology, Mekelweg 15, 2629, JB, Delft, The Netherlands
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| Abstract: | The kinetics of cadmium uptake by Selenastrum capricornutum Printz was studied at 21 °C and 0 °C and at four different concentrations of free cadmium (10?9, 10?8, 10?7 and 10?3 M). The free cadmium concentrations in the medium were kept constant through buffering by a chelating agent (NTA). Initial uptake occurred within 10 min at both temperatures, indicating a fast process. At 21 °C, the cadmium uptake increased during the experimental sampling times from 0.12 to 50 h, whereas at 0 °C, the cadmium uptake remained constant after the first sampling time. Apparently, two different processes were involved in cadmium uptake, a first fast, probably passive process and a second slower, possibly physiological process. The cadmium uptake processes are described with a generalized metalligand complex formation model. The experimental dissociation constants for the fast (K R,F ) and the slow process (K R,S ) were reproducible for different experiments and they were both in the order of 5 10?6 mol L?1. For the slow process, the uptake- and release rate constants (k1 and k2) were quantified; for two experiments, the mean value for ki was 111±28 L mol?1 h?1 and the mean value for k 2 was (5.1±1.8) 10?4 h?1. These values were calculated using the fitted value of the cadmium uptake in the fast process. |
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