Phytoremediation of effluents from aluminum smelters: a study of Al retention in mesocosms containing aquatic plants

Four mesocosms were exposed to circumneutral and aluminum (Al)-rich wastewater during two successive summers (2000, 2001). The goals of the study were to measure the bioaccumulation of dissolved Al by the aquatic plants Typha latifolia, Lemna minor, Nuphar variegatum and Potamogeton epihydrus, and to evaluate their importance in the retention of Al by the mesocosms. In 2000, inlet concentrations of total monomeric Al were reduced by 56% and 29% at the Arvida and Laterrière mesocosms, respectively, whereas in 2001 inlet dissolved Al concentrations in the inlet decreased by 40% and 33%. L. minor had the highest Al uptake rate (0.8--17 mg Al g(-1)d(-1)). However, because T. latifolia (cattails) yielded the highest biomass, it was responsible for 99% of the Al uptake, largely in its root tissue. In 2001, Al uptake by macrophytes accounted for 2--4% and 15--54% of the total Al retained by the Laterrière and Arvida mesocosms, respectively. In the Laterrière mesocosms, Al uptake by cattails could account for 12% and 18% of the dissolved Al retained by both mesocosms. In contrast, dissolved Al was not significantly reduced in the Arvida enclosures, yet cattails did accumulate Al in their roots. Further research is needed to identify the species community composition that would optimize dissolved Al retention.