Izabel Christina d'Almeida Duarte de Azevedo

Avaliação de contaminação por mercúrio em Descoberto, MG

Mercury is a chemical element considered unessential to any metabolic process; however, it is easily accumulated in most organisms. It is naturally found in both organic and inorganic forms in solid, liquid and vapor states. Its biogeochemical cycle involves processes occurring in the soil, water and the atmosphere. In 2002, elementary mercury was found in the city of Descoberto, Minas Gerais, Brazil, where 70 families live, and its origin may be related to gold exploration that happened in this region in the 19th century. In this work, three areas were chosen to identify a possible mercury contamination of water, soil, sediment and fish samples and to establish local reference values and counter-evidence of the data previously obtained. Based on the results, high mercury concentrations in soil (0.26 to 0.55 mg.kg-1), sediments (0.13 to 0.61 mg.kg-1) and water (< 0.2 to 2,10 µg.L-1) were verified.

Variation in Hydraulic Conductivity by the Mobility of Heavy Metals in a Compacted Residual Soil

There is a growing consciousness worldwide that progress must be linked to environmental preservation. However, in order to preserve the environment it is necessary to know it and only with an understanding of the mechanisms that regulate the integration of man with nature is it possible to use the environment resources without degrading or destroying it. Heavy metals are important environmental contaminants that are toxic above a given concentration. Causes of soil contamination by metals include domestic and industrial solid waste disposal, atmospheric deposition of vehicular and industrial emissions, agricultural use of fertilizers, soil additives and pesticides and disposal of crop wastes (Alloway, 1995). Underground waters may be contaminated when metals levels exceed the maximum soil retention capacity. Population growth and the consequent increase in waste generation has led to an increased demand for technologies that decrease the environmental impact of these wastes, especially with regard to barrier systems used to minimize the infiltration of waste leachates and contain migration of contaminants through soils and underground water in areas of waste disposal. Tropical soils are common in Brazil. Compacted soils of this type is either used alone or associated with geomembranes have been used as liners in industrial and urban solid waste disposal areas. However a great deal of uncertainty exists with regard to use of these soils since few studies have been undertaken to evaluate their applicability. More studies on the interactions that occur between tropical soils and contaminant solutions are therefore necessary because these interactions may modify properties, such as hydraulic conductivity, which are important in controlling contaminant transport through soils. The only legal requirements for liners are hydraulic conductivity limits. However, sensibility to contaminants of the soil used for impermeabilization may affect its structure and modify the liner layer by increasing its hydraulic conductivity, thus favoring contamination. Microscopic mechanisms responsible for thecha nges are of physicochemical and/or purely chemical nature. Redistribution of the pore space driven by