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- Phytoremediation of cadmium at different salinities by Scirpus maritimus from the Óbidos Lagoon (Portugal)Publication . Santos, MárciaA greenhouse experiment was performed, to verify if phytoremediation of cadmium can be done by using the macrophyte Scirpus maritimus from the Obidos Lagoon (Portugal), plus if water salinity can influence its phytoremediation effectiveness. Two concentrations of cadmium were tested (50 and 100 ƒÊg l-1) to evaluate the plant capability to accumulate cadmium, plus possible toxicity effects of this pollutant. The contamination levels were tested at different water salinity conditions (values equal to 0.0, 5.0, 10.0 and 20.0), in which the plants are usually submerged in, at their natural environment. S. maritimus mortality was mostly determined by the water salinity and not for the cadmium contamination, in which more plants died at higher water salinities. The surge of new shoots, plant length and biomass increments were not proved to be affected by either of those factors, however, plant length and reduction and biomass loss can be induced by increasing water salinities. There was a biofilm development in all trial vessels, independently of the type of treatment involved. These suspended microorganisms and senescent organic matter presented more cadmium, according to initial water level of cadmium. The amount of water dissolved cadmium was positively related to the initial contamination levels of the experiment, but it increased also at higher water salinities. This may have resulted from tissue degradation and disruption from dead plants, possibly potentiated as well by symbiotic organisms and those from the biofilm, some of which may have promoted tissue decomposition and bioavailability of dissolved cadmium. The plants presented more cadmium in the rhizomes, followed by the stems, and less in the leaves. More cadmium accumulated in the plant fs rhizomes, according to higher water contamination levels and lower water salinities. According to the results, salinity could influence the transport of cadmium in the plant, between roots and leaves. However, the phytoremediation of the Obidos Lagoon by S. maritimus, or other similar systems, may be not be possible, due to the salt stress of the plants, the salt interference with the cadmium accumulation, and the normal functions of a plant. But the optimization of phytoremediation processes by S. maritimus could turn possible the use of this plant in freshwater ecosystems.
- How do salinity and heavy metal contamination affect Salicornia ramosissima and the Cadmium accumulation capacity?Publication . Pedro, CarmenThe major aim of this study was to evaluate the capacity of Salicornia ramosissima, a halophyte present in Obidos lagoon (Portugal), on Cadmium (Cd) phytoremediation, when submitted to different salinities and Cd concentrations, for a month. Two Cd concentrations were used to evaluate this capacity and, consequently, the toxic effect of Cd on the plant development. The contamination levels were tested in different salinities (0, 5 and 10), taking into consideration the natural conditions that S. ramosissima is subject in its natural environment. The mortality registered in the end of the experiment, as the growth parameters measured (length and weight), did not showed significantly differences between the treatments, which means were not affected for the salinity or Cd concentrations, neither for the interaction of those two stress factors. However, length elongation and the variation of weight, observed in the end of the experiment, may have been induced by the increase of salinity and Cd concentration. A highest Cd accumulation was detected in the roots of S. ramosissima, compared with the aerial portion. The Cd accumulation in roots decreased with the increase of salinity and Cd concentration, even though statistically there were no significant differences between treatments. In all treatments, a biofilm was form, highlighting treatment salinity 0 x 50 μg Cd.l-1, where microorganisms and, eventually, organic matter (from the plant), suspended revealed a higher Cd amount relatively to the water initial Cd concentrations. The dissolved Cd concentration, detected in the final of the experiment, was in accordance with the initial contamination levels used in this study; however an increase was observed for some treatments, possible as a result of decomposition of organic matter and consequent release of Cd to the water. Salicornia ramosissima is a potential candidate for Cd phytoremediation at salinities close to 0, where development is maximum and, consequently, is Cd accumulation capacity. The optimization of phytoremediation processes by S. ramosissima could turn possible the use of this plant in freshwater ecosystems.