Avaliação de risco ambiental por contaminação metálica e material orgânico em sedimentos da bacia do Rio Aurá, Região Metropolitana de Belém - PA

Abstract

A bacia do Rio Aurá está situada na região metropolitana de Belém, entre os municípios de Belém e Ananindeua, onde a taxa populacional tem aumentado sem qualquer medida de controle social ou ambiental. A região é intensamente explorada, sendo que os principais problemas ambientais são o desmatamento, erosão, inundação, poluição e contaminação das águas, especialmente por metais pesados e compostos orgânicos. O comportamento geoquímico dos elementos Al, Fe, Mn, Cr, Ni e Cu e os teores de compostos orgânicos foram avaliados em 30 pontos de amostragem no período entre 2008 e 2010 nos sedimentos fluviais. O aterro sanitário não controlado localizado nas proximidades da bacia do Rio Aurá é responsável, em parte, pela contaminação dos sedimentos. O estresse ambiental é resultado das atividades antrópicas locais, que contribuem no transporte de material clástico contendo metais para o rio. As variáveis estudadas foram classificadas segundo mecanismos de transporte e fonte (autóctone ou alóctone). Os resultados demonstraram que a principal contribuição de íons Al e Fe foi o aterro sanitário; Mn e Ni vieram principalmente dos solos adjacentes; Cr foi modificado (III/VI) por processo alobioquímico e Cu por processo bioinduzido. PalavRas-chave : metais pesados; saneamento; vulnerabilidade; geoquímica; Amazônia Evaluation of environmental risk by metallic contamination and organic compounds in sediments of the Aurá River basin, Belém, Pará -Brazil abstRactThe Aurá River basin is situated in the Belém Metropolitan region, between the municipalities of Belém and Ananindeua, where the rate of population growth has increased without any social and environmental control. The region is intensely exploited and the more frequent environmental problems are deforestation, erosion, flooding, water pollution and contamination, especially by heavy metals and organic compounds (OC). Geochemistry behavior (Al, Fe, Mn, Cr, Ni and Cu) and OC levels were determined in the 30 sampling sites between 2008 and 2010 in the bottom sediments of the river. There is an uncontrolled sanitary landfill situated at the north of the Aurá River responsible, in part, by the metallic contamination of the sediments. The environmental stress is classic in the region, and it has resulted from anthropic activities, which has transported unconsolidated material associated to metals to the Aurá. The variables studied were classified on the transport mechanisms and sources (allochthonous and/or autochthonous). The results showed that the main contribution of ions Al and Fe was the sanitary landfill; Mn and Ni was the adjacent soils; Cr was modified (III/VI) by the allobiochemistry, and Cu by bio-induced processes.

Phytoextraction of heavy metals from a landfill in the metropolitan region of Belém-Pará-Brazil

“…This variation may be related to the irregular disposal of solid waste at the study site; however, it is also likely that this variation is the rock matrix because in that scenario would suggest EFs < 1 (Chen et al, 2007). Thus, there is evidence that the presence of the dump in the area contributes to soil contamination via the discharge of material containing heavy metals, which corroborates the results obtained by other authors (Siqueira;Aprile, 2013).…”

“…In another study in the Aurá River basin, the mean level of total Cu in the sediments was 19.57±4.52 mg kg -1 (Siqueira;Aprile, 2013). This result reinforces the idea that the dump is contributing to the contamination of the site by Cu, most likely because the metal is leaching from the soil to the water source.…”

“…From the levels of Al, Fe, Cu, Mn, Zn, Cr, Ni, Cd and Pb measured in the soil, the enrichment factor (EF) was determined for Cu, Mn, Zn, Cr, Ni, Cd and Pb in the analyzed soil using the formula EF = (X1/Y1)/(X2/Y2), where X1 is the level of the element in the soil, Y1 is the level of the standard element in the soil, X2 is the natural level (reference value) of the studied element and Y2 is the natural level (reference value) of the standard element (Siqueira;Aprile, 2013). The correlations of Fe and Al with the other metals were evaluated to define the standard element to be used in the normalization of the equation.…”

“…Furthermore, Al is related to the colloidal phase of the soil, its geochemistry resembles the geochemistry of numerous heavy metals and its natural concentration in the environment tends to be uniform (Siqueira;Aprile, 2013). The study area is located in a highly weathered soil; thus, this element plays a major role in influencing the form of binding of heavy metals in the soil.…”

“…The disposal of waste in open areas close to water sources can cause significant environmental impacts, such as contamination by organic and inorganic substances. The leachate derived from the disposed waste, which can infiltrate through soil or reach water resources through runoff, is a major concern (Siqueira;Aprile, 2013).…”