Kinetics of cadmium uptake by green algae

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 k_i 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.     

Patterns in trace elements in lichens

Water, Air, & Soil Pollution - Epiphytic lichens were sampled in a Dutch national monitoring survey, which was carried out twice within 5 yr. The samples were analyzed by neutron activation...