Avaliação ambiental das vias de drenagem da região metropolitana de Belém (PA) quanto à distribuição dos elementos Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb e Zn

Abstract

The investigation of the concentrations of heavy metals in the seven main drainage routes of the city of Belém, with a view to the environmental issue, is the central content of this work. The introductory chapters focus on the geology, geomorphology, soils, climate, vegetation and hydrology of the city of Belém, characterizing the natural conditions of the environment in the studied drainages. From the methodological point of view, the work has two phases: the first consists of the recognition, location and determination of metals (Ca, Na, K, Mg, Fe, Cr, Zn, Cu, Cd, Pb, Ni and Mn) and their main sources, natural or anthropogenic, or both; the second, in detailing the distribution and chemical behavior of each metal in the Tucunduba stream, which has a higher concentration of these elements. The Tucunduba stream presents, in addition to the sources of metals common to all other drainages, such as domestic sewage, rainwater discharge and the influence of estuarine tides, the effluent from a leather treatment industry, thus showing anomalous values ​​for the chromium element. The investigation of the physical-chemical parameters of the waters of the drainage ways studied, aims to characterize and identify the behavior of the metallic compounds formed, emphasizing the seasonal variation - function of the rainfall intensity - and the action of the outgoing tides. The Tucunduba stream is the only one to be considered polluted by metals - due to the high concentration of chromium found in its waters and sediments - compared to polluted rivers and lakes in Brazil, Europe and the United States. Despite the small number of samples from each drainage and the great variation in the results, some linear correlations were observed between the concentrations of metals, among themselves and with the physicochemical parameters, which characterize the intense influence of the tides of the Guajará Bay and the Guamá River in the drainages. These correlations also show the existence of large amounts of surfactants derived from synthetic soaps and detergents.