Ocorrência de metais pesados no curso inferior do rio ivaí, em decorrência do uso do solo em sua bacia hidrográfica

Abstract

During the last few decades, the Ivaí River basin, in the region of the Third Plateau of Paraná, has suffered the most varied types of aggressions. These impacts have provoked changes of physical, chemical and biological natural characteristics in the river environment. In order to observe some aspects of such modifications, five composed samples of water were collected at located stations, during six months, in the cities of Icaraíma, Herculândia and Tapira. In all samplings, at each collection, the following were measured: pH, temperature, transparency and dissolved oxygen. The collected water samples were submitted to nitric digestion with volume reduction in a water bath system. The concentrations of heavy metals were obtained through the method of flame atomic absorption. The results, intervals and median values, in μg L-1, were: Cd (not detected -nd); Pb (13.0-67.0, 20.0); Co (nd-2.0, nd); Cu (1.0-100.0, 8.0); Cr (nd-4.0, nd); Fe(90.0-4,400.0, 1,080.0); Mn (nd-130.0, 30.0); Ni (nd-6.0, nd) Zn (4.0-400.0, 10.0). It was possible to conclude that the heavy metals Pb, Zn, Cu and Fe presented a greater regularity in impacting the river environment, exceeding the concentration limit of the Conama (Brazilian Environment National Council) Resolution 357/2005, probably as a consequence of the agricultural activity in the hydrographic basin.