UPTAKE AND RELEASE KINETICS OF COPPER BY THE AQUATIC MOSS Fontinalis antipyretica

Copper uptake and release rates by Fontinalis antipyretica were investigated. A contamination stage in which the plants were exposed to Cu concentrations in the range 0.09–0.75 mg l−1 was followed by a decontamination period, exposing the plants to metal-free water. Tanks were operated in perfectly mixed conditions and the illumination at water surface was 740 lux. Short and long duration experiments (217 and 1008 h, respectively) were carried out with plants collected in May and August, respectively. A simple mass transfer model was fitted to the experimental results in order to determine the uptake and release rate constants, k1 and k2, the Cu concentration at the end of the uptake phase, Cmu, and the equilibrium concentrations, Cme and Cmr, for the contamination and decontamination stages, respectively. In the short duration experiment, k1 decreased from 846 to 628 h−1 as Cu concentration increased from 0.14 to 0.60 mg l−1. In the long duration one, with plants in different physiological conditions, k1 decreased from 448 to 293 h−1 as Cu concentration increased from 0.09 to 0.75 mg l−1. The release rate constant, k2, appears not to depend on the Cu concentration and averaged 0.020 and 0.011 h−1 in the first and second experiments, respectively. The ratio k1/k2 represents a bioconcentration factor, BCF (Cu concentration in the plant, dry wt/Cu concentration in the water). BCF values ranged between 40,000 and 30,000. A biological elimination factor was also calculated. BEF values slightly increased with Cmu, varying from 0.58 to 0.62 (5203