AVALIAÇÃO DOS NÍVEIS BASAIS DE MERCÚRIO NA ÁREA DE INFLUÊNCIA DA UHE JIRAU RIO MADEIRA / AMAZÔNIA

Abstract

The hydrobiogeochemical cycle of mercury contemplates the natural and artificial sources of the metal, as well as the biotic and abiotic processes that occur in the distinct reservoirs and that they determine the transport and setting of the metallic forms in some final receiver. The process of methylation of mercury has deserved special attention in natural and artificial reservoirs in the Amazon region which had the raised toxic of the methylmercury for the human beings and animal, had the bioaccumulates in the aquatic alimentary chain. The present study it deals with the evaluation of total mercury and methylmercury natural levels in biotic and abiotic compartments of the basin of the river Mutum Paraná in the area of influence of the UHE - Jirau in the hidrography basin of the Madeira river. The values of total mercury in the water samples had been slow the 6,5 ng L-1, being approximately 150 lesser times that the values praised for the Ministry the Health for the human consumption, and the levels of the 0,3 methylmercury had been inferior ng L-1. The total mercury texts in the sediment of deep had presented values in the bands of 170+47 - 294+88 μg kg-1 whereas the texts of methylmercury the band of 0,84+0,25 - 1,40+0,35 μg kg-1, being the organic mercury fraction in the sediment in approximately 0.45% of the total mercury supply. The texts of total mercury in plankton and invertebrates had respectively presented values in the bands of 143+24 - 277+25 μg kg-1 and 191+25 - 323+45 μg kg-1, whereas the texts of methylmercury in the band of 4,41+1,22 - 9,76+0,67 μg kg-1 and 16,74+2,57 - 23,99+2,34 μg kg-1 respectively, evidencing the trend of the process of accumulation in the inferior levels of the eutrophic chain. The samples of ichthyofauna of consumption relevant in the traditional population of the study region had presented values of total mercury in the band of 0,06+0,19 - 0,12+0,04 mg kg-1 for the herbivores and omnivorous specimens and 0,28+0,5 0,40+0,1 mg kg-1 for the carnivorous specimens having evidenced the process of bioaccumulation and biomagnification in ichthyofauna. The values of the levels of the species of total methylmercury and methylmercury in the abiotics samples and bioptics had not evidenced points of diffuse contamination.