Comportamento de metais pesados e nutrientes nos sedimentos de fundo da Baía do Guajará e Baía do Marajó

Abstract

Human activities influence the physical and chemical characteristics of water, sediments and organisms in aquatic environments located in industrialized areas and high population density. With the increasing use of estuaries as a reservoir for a large amount of waste, coastal and estuarine ecosystems are gradually being subject to significant impacts. The bottom sediments play an important role in the investigation of these impacts since it has the ability to retain chemical species and inorganic. The objective of this research is to study the geochemical behavior of metals in the bottom sediment of the Bay of Guajará, Guama River and the Bay of Marajo. The two regions were chosen for their opposite characteristics: a Guajará Bay Area (1) under strong anthropogenic influence and Marajó Bay Area (2) considered the reference. We collected 83 points in Area 1 and 60 points in Area 2. Determined chemical concentrations of the following metals: Ba, Cr, Cu, Fe, Pb, Ni, V and Zn, and also the levels of nitrogen, carbon, organic matter, total phosphorus and phosphorus bound to organic compounds. Area 1 shows the average content of nitrogen of 0,08 %, mean levels of carbon and organic matter from 1,51 % and 2,60 %, respectively. The concentration of phosphorus and phosphorus bound to organic compounds 307 mg / kg and 126 mg / kg, respectively. The concentration of metals showed the following values: Ba (529 mg / kg), Cr (91 mg / kg), Cu (17 mg / kg) , Fe (6,82 %), Ni (32 mg / kg), Pb (27mg / kg), V (120 mg / kg) and Zn (69 mg / kg). Area 2 shows the average content of organic matter 1.70 % of carbon and nitrogen 0,98 % and 0,08 % respectively. The concentration of phosphorus and phosphorus bound to organic compounds 193 mg / kg and 7 mg / kg, respectively. The concentration of metals showed the following values: Ba (596 mg / kg), Cr (102 mg / kg), Cu (21 mg / kg) , Fe (8,31 %), Ni (40 mg / kg), Pb (28 mg / kg), V (141 mg / kg) and Zn (85 mg / kg). The carbon and phosphorus (0,98 %, 193 mg / kg), respectively found in area 2 were lower than those found in area 1 (0,51 %, 307 mg / kg) and demonstrate the influence of effluents that are released in the estuary Guajarino. In both areas there is the same downward trend in levels: Fe2O3> Ba> V> Cr> Zn> Ni> Pb> Cu. In area 1 were found higher metal alone while in area 2, with the major averages, the distribution is homogeneous, two areas in the metals has a slight tendency to concentrate where there is a higher content of organic matter.