ACCUMULATION OF LEAD IN 2 FRESH-WATER ALGAE

The uptake of lead from aqueous solution by Chlorella vulgaris and Chlamydomonas sp. was studied after 20 min or 5-7 days exposure to Pb(II). Quantitative measurement of Pb(II) accumulated by the organisms was accomplished using ICP (Inductively Coupled Plasma) analysis after acid digestion. The location of accumulated Pb in algal cells was determined by electron microscopy. C.vulgaris was able to abstract considerably more Pb(II) from solution than was Chlamydomonas sp. The Pb accumulation process also depended on the nutrient medium in which the algae were cultured and on the concentration of Pb(II) in the aqueous solution. Algae were able to accumulate higher concentrations of Pb(II) during cultivation in media which contained Pb(II) than could be achieved by immersing algae in solutions of Pb(II) subsequent to growth in Pb free media. Electron micrographs indicate that both algae accumulated Pb within the cells as well as in the surface structures after 5 or 7 days exposure to Pb(II). However, with 20 min exposure to Pb(II) after prior culturing in the absence of Pb the Pb accumulation was almost exclusively in cell walls.