Este trabalho teve como objetivo avaliar o efeito da irradiação solar na especiação do cobre em amostras de água coletadas em um reservatório eutrofizado e contaminado por metais. Voltametria de redissolução anódica e eletrodo de íon seletivo foram utilizados para determinação de cobre nas amostras irradiadas e não irradiadas. Os resultados demonstraram que após 7 h de irradiação solar, a matéria orgânica dissolvida (DOM) foi degradada promovendo aumento de cobre iônico livre, lábil e de carbono inorgânico dissolvido (DIC), e diminuição da concentração de ligantes disponíveis (C L) e de carbono orgânico dissolvido (DOC). Os valores da constante de estabilidade condicional (logK') variaram em duas amostras, permanecendo constantes nas demais. Os resultados demonstraram que as reações fotoquímicas afetaram a especiação do cobre e as interações Cu-DOM, ressaltando implicações ecológicas da fotoxidação, como o aumento do cobre biodisponível e, desta forma, contribuindo para o entendimento do ciclo biogeoquímico desse metal.

The aims of this research were to evaluate the effects of solar irradiation on copper speciation in water samples obtained in eutrophic and metal contaminated reservoir. Anodic stripping voltammetry and ion selective electrode were used for metal determinations of solar irradiated and non-irradiated samples. The results showed that after 7 h of solar irradiation, dissolved organic matter (DOM) was degraded promoting the increase of labile, free Cu2+ ions and dissolved inorganic carbon (DIC). Decreases of ligand concentration (C L) and dissolved organic carbon (DOC) were also observed. Conditional stability constant (logK') values varied for two sampling sites, but remained unchanged for the others. The present results demonstrated that photochemical reactions affected copper speciation and Cu-DOM interactions. This research is a contribution to the understanding of biogeochemical cycle of copper and highlights some ecological implications of photooxidation in freshwater ecosystems, such as the increase of copper bioavailability.

The existence of a mucilaginous envelope, sheath or capsule is usual in many desmids, but few data concerning its function are available. Previous studies of the transport function and permeation of molecules through the algae capsules were done using the algae Spondylosium panduriforme and Nephrocytium lunatum, the Electron Paramagnetic Resonance (EPR) technique, and different spin labels. The results suggested that the capsule functions as a selective diffusion medium. In the present work charged and uncharged molecules (spin labels group A) and Staurastrum iversenii var. americanum (Desmids),whose alga presents a great mucilaginous capsule, were used. Charged nitroxide molecules similar to amino acids (spin labels group B) were also used allowing a better understanding of the electrostatic effect in the permeation process across the capsule. The role of the cell capsule in the solute diffusion was evaluated by determining the capsulated and decapsulated cell permeation times. The permeation times for all spin labels tested in the cells lacking capsules were always shorter than those containing this physical barrier. The decay times of spin labels group A observed for S. iversenii were compared to other studied algae. The results regarding the diffusion of charged spin labels group B suggested that the interaction of cell capsule occurs more strongly with negatively charged molecules than with positively charged ones. The results obtained in this work with spin labels group A confirm that the capsule is an essential structure for the cell, and that due to the polar interactions with the spin labels, it plays an important role in the selection of small molecules. Several parameters, mainly those of electrostatic nature, seem to control the permeation across the algal capsules of spin labels group B, showing that structures which are similar to amino acids could diffuse across the interior of the algal cell.

Some aspects of the procedures to measure dissolved organic matter (DOM) released by phytoplankton account for important sources of errors. These aspects include: cell damage upon filtration of samples, residual inorganic 14C in the filtrates, NaH14CO3 ampoule contaminations and the low radiation activity proper to the released samples. Some experiments on these procedural problems were carried out and their effects on the released DOM were evaluated. A procedure to use control samples to avoid errors in the technique of DOM analysis by the liquid cintillation counter is described. Experiments on the validity of stocking preserved filtrates of natural plankton populations and algal cultures were also carried out for long periods prior to the radioactivity measurements.

The study of algae culture collected in Brazilian waters was proposed due to the lack of literature on the subject: an attempt was made to develop a methodology to obtain algae culture and its purification. Several species were isolated from samples collected a Ubatuba and Cananéia (São Paulo) (Lat. 23º30'S - Long. 45º06'W and Lat. 25º01'S - Long. 47º54'W) by means of phytoplankton net and Van Dorn bottle. The following isolation techniques were employed after washing and concentration: glass capillary, inoculation of mixed cultures on Petri dishes with solid medium and positive phototropism. The isolated algae were kept in five different mediuns. Washing techniques were tested (centrifugation, "filter tubes" and re-isolation) , antibiotics and ultra violet radiation to obtain unialgal bacteria-free cultures were employed to obtain pure cultures. Five différents antibiotics, mixed in différents concentrations, were employed during several periods of expositions. The re-isolation proved to be the best method to obtain the purification of the cultures.