Cadmium and Chromium sorption mechasnisms in two aquatic macrophytes

SUÑÉ, N.L.; MAINE, M.A.; SÁNCHEZ, G.C.; CAFFARATTI, S.E.

Ghent, Belgica

Simposio; International Symposium on Wetland Pollutant Dynamics and Control.; 2005

Universiteit Gent, Faculty of Bioscience Engineering

The aim of this work was to determine chromium and cadmium bioaccumulation mechanisms of two free-floating macrophytes: Salvinia herzogii and Pistia stratiotes. Aquaria containing 100 g wet plant biomass and 7 l of lake water were used to determined Cr and Cd sorption kinetics. The concentrations studied were  1,  2,  4 and 6 mg l-1. Roots and leaves samples were used to study Cd and Cr  distribution in both macrophytes.  SEM X-ray microanalysis  were used.  In order to identify sorption mechanisms, Ca2+ was used as a competitive cation for the anionic bond sites and  EDTA  as a chelating agent for removing metal from plant tissues through chelation. Metal removal from the solution involves two stages: a fast one and a slow one. The fast stage, occurs during the first hours of contact  because of adsorption, chelation and ionic exchange. The fast stage of the Cd uptake is significantly different for each species, while it is not significantly different in Cr uptake. The slow stage is different for each species and each metal. Removal mechanisms differences between species and metal are discussed.