Lead accumulation by free and immobilized cyanobacteria. Lyngbya majuscula and Spirulina subsalsa was studied. Exponentially growing biomass was exposed to 1-20 mg L(-1) of Pb(II) solution at pH 6,7 and 8 for time periods ranging from 10 min to 48 h. L majuscula accumulated 10 times more Pb (13.5 mg g(-1)) than S. subsalsa (1.32 mg g(-1)) at pH 6 within 3 h of exposure to 20 mg L(-1) Pb(II) solution and 76% of the Pb could be recovered using 0.1 M EDTA. This chelator (2 mu M) did not influence Pb accumulation whereas 100 AM citrate increased that of S. subsalsa 6- to 8-fold. L majuscula filaments enmeshed in a glass wool packed in a column removed 95.8% of the Pb from a 5 mg L(-1) Pb solution compared to free and dead biomass which removed 64 and 33.6% Pb respectively. A 92.5% recovery of accumulated Pb from the immobilized biomass suggests that repeated absorption-desorption is possible. (C) 2010 Elsevier Ltd. All rights reserved.