Chemical composition and toxicity of waste dump leachates usingSelenastrum capricornutum Printz (Chlorococcales, Chlorophyta)

Chemical composition and toxicity of leachates from a municipal waste dump in Buenos Aires Province were analyzed. Three sets of samples, obtained in 1996 and 1997, were compared. Levels of nitrogen, phosphorus, and organics (expressed as GOD) were distinctly lower in 1997. Such differences were mainly attributed to higher rainfall in that year. The Selenastrum capricornutum assay showed a high sensitivity to heavy metals (Cd = 0.049 mg L-1; Cr hexavalent = 0.247 mg L-1 and Zn = 0.037 mg L-1). Cu, Zn, and Pb concentrations were toxic to algae in leachate samples of the first year, while the EC50 leachates were slightly toxic (86.6 and 99.31%). Most likely, high levels of organics (COD = 4640 and 3470 mg L-1) form complex mixtures with metals reducing their toxicity. The EC50 leachate = 48.5% in the last year may be explained by high concentrations of Pb and Cu. (C) 2000 by John Wiley & Sons. Inc.