Friday, 14 July 2006
89-6

Heavy Metal Contamination after Solid Waste Disposal on a Tropical Reclaimed Soil in Engenheiro Caldas (MG), Brazil.

Meubles Borges Júnior1, Virginia H. B. Lima2, Miriam A. Albuquerque2, and Guilherme K. Donagemma3. (1) UNEC, Av Moacir de Mattos 49, Caratinga, 35300-047, Brazil, (2) Centro Universitário Caratinga, Av Moacir de Mattos 49, Caratinga, 35300-047, Brazil, (3) EMBRAPA, Rua Jardim Botânico 1024, Rio de Janeiro, 20000, Brazil

One of the main sources of contamination of the environment is the accumulation of solid wastes, that can be defined as the result of any natural, human or animal activity, generally considered undesirable for the environment. Waste disposal, without any form of handling or treatment, can contaminate soil through physical, chemical and biological changes. Contamination by heavy metals is considered one of the most harmful ways of enviroment pollution of the environment, since these elements do not degrade and tend to accumulate in living organisms, causing intoxication. The concentration of heavy metals in the soil varies according to the geology and also due to man-made impacts. The mobility of metals in soil is highly influenced by pH and cation exchange capacity. In the town of Engenheiro Caldas, Minas Gerais state, Brazil, a former lake now drained, became an unplanned site of solid waste disposal. This work aimed to determine the concentration of Cd, Cr, Cu, Ni, and Zn in the soil samples from that site, comparing with another area nearby, where no contamination, ocurred, as values determined were compared with Quality Reference Values (QRV) and Alert Values (AV)based on Companhia de Tecnologia e Saneamento Ambiental-CETESB. The contaminated area was subdivided into three areas (A1 – within the direct waste disposal area; A2 – near the water course and A3 – an area 400 m apast from the A1 site, as well as the reference site (A4). The concentrations of metals were obtained through a triacid attack(HNO3, HCl e HF). The A2 and A3 areas presented higher concentration of clay (64 e 49%, respectively), pH (5,6 e 6,0, respectively) and cation exchange capacity (24,3 and 31,5 cmolc/dm3 respectively) compared with A1 and A4 areas, which may promote a greater adsorption of metals in soil in these areas. The A3 area presented higher concentration of Cd (8,45 mg Kg-1, respectively) indicating higher mobility of this metal in relation to the other metals. Cr and Ni amounts (100,5 and 38,17 mg Kg-1, respectively) presented similar behavior, with higher accumulation, in the area close to the water course (A2). Cu and Zn presented higher concentrations (51,8 and 306,7 mg Kg-1, respectively) in the area directly affcted by waste disposal, this showing less mobility than the others. Statistical contrast analysis showed significant differences (at 1% level) between the concentrations of all studied metals in A1, A2 and A3 compared with the concentration of the local reference (A4 area). Concerning VRQ, all metal elements, except Cu and Zn, presented a positive significant difference (at the 1% level of significance, Test T student) for all areas. In relation to AV only Cd presented a positive significant difference for all areas; Cr presented a difference only in A1 and A2 areas while Ni only in A2 areas.


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