The accumulation of cadmium from aqueous systems by various green microalgae was investigated with focus on Chlorella regularis as it is known to concentrate large amounts of heavy metals. The amount of cadmium absorbed by Chlorella cells was rapid during the first 30 min following addition of cadmium and then continued to be absorbed more slowly. The uptake of cadmium by Chlorella was not markedly affected by temperature or metabolic inhibitors. Most of the cadmium absorbed by Chlorella cells was easily released by EDTA. The amount of cadmium absorbed differed markedly with the pH value of the solution and was inhibited by the presence of other divalent cations.
Heat-killed Cblorella cells took up cadmium to a greater degree than living ones. From these results, it was considered that the uptake of cadmium into Cblorella cells was not directly mediated by metabolic processes, rather it appeared completely dependent upon physico-chemical adsorption on the cell surface.
The ability to accumulate cadmium was species specific and found to be (in decreasing order) i Cblamydomonas reinhardtii > Cblorella regularis > Scenedesmus bijuga > Scenedesmus obliquus > Chlamydomonas angulosa > Scenedesmus cblorelloides.