Radioecological evaluation (spatial and temporal variation) of the planktonic microorganisms in the Antas reservoir, Caldas - MG

The Antas Reservoir (AR) receives the treated effluents from the UTM-INB (Ore Treatment Unit - Brazilian Nuclear Industries), located in Caldas, MG, which come from acid drainage of uranium ore. This study is being conducted in order to determine the possible environmental impact caused by discharges of the treated liquid effluent from the UTM into the AR. Biological (protozooplankton, phytoflagellate Peridinium sp. and chlorophyll) and physicochemical variables (zinc, sulfate, manganese, fluoride, phosphate, uranium, thorium, temperature, pH, and dissolved oxygen) are being evaluated in the present study. Sampling in the AR (Cab, P41, P14S, and P14F points) took place during the dry season - winter (July 2006) and rainy seasons summer (February 2007). Two seasonal sampling campaigns were conducted (winter - 07/19/06 and summer - 02/28/07). Each day, samples were collected four times (6:00 am, 12:00 pm, 6:00 pm, and 12:00 am). The average Trophic State Index values obtained for samples from points Cab, P41 and P14F, in the dry and rainy periods, allowed the areas to be classified as: mesotrophic, mesotrophic, and eutrophic, respectively. Chemical parameters indicated failures in the nuclear facility effluent treatment system, showing that effluents discharged on point 41 do not agree with the standards that have been established by current legislation for Class II water. These results agreed with biological analyses, since point 41 has the lowest diversity and biomass values for protozooplankton organisms, indicating possible environmental impacts on the ecosystem due to the release of effluents by this mining company. (author)