RESUMO

Since the Fundão Dam rupture in Southeastern Brazil caused an enormous amount of iron ore tailing (IOT) to be discharged into the Doce River Catchment, various works have been published on the soil, water, and biota contamination by potentially hazardous trace metals. However, the objective of this study is to investigate changes in the main chemical composition and the mineral phases, which has not been studied yet. We present an analysis of sediment samples collected in the Doce River alluvial plain, before and after the disaster, as well as the tailing deposited. Granulometry, main chemical composition by X-ray fluorescence spectrometry, mineralogy by X-ray diffractometry, quantification of mineral phases using the Rietveld method, and scanning electron microscope imaging are shown. We conclude that the Fundão Dam rupture introduced fine particles into the Doce River alluvial plain, increasing the Fe and Al content in the sediments. The high Fe, Al, and Mn contents in the finer iron ore tailing fractions represent environmental risks for soil, water, and biotic chains. The IOT mineralogical components, mainly the muscovite, kaolinite, and hematite present in the finer particles can increase the sorption and desorption capacity of harmful trace metals depending on the natural or induced redox conditions, which are not always predictable and avoidable in the environment.

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The collapse of the Fundão Dam, in Southeastern Brazil, caused about 50 million m³ of iron ore tailings to sluice down the mountain to Rio Doce, in what is considered the greatest environmental disaster in Brazilian history. The fluvial system received an intense and sudden mudflow that was transported for more than 650 km, before reaching the Atlantic Ocean. Because the area was already impacted by the mineral activities in the region, it becomes essential to evaluate the environmental conditions before the disaster to correctly assess the disaster real damage. This study compares the concentration of trace metals in the sediments of the Rio Doce alluvial plain, before and after the dam collapse, as well as the newly deposited iron ore tailings that became part of the sedimentary framework. The data indicate that the fine particles deposited have since been incorporated into the sandy river sediments. The cadmium and arsenic contents in the sediments increased to levels above the National Environment Council thresholds. The comparison between the levels of trace metals in the situations before and after disaster shows that the mining mud is the source of cadmium while the arsenic was present before the environmental disaster, and its concentration increased due to sediment remobilization. The iron ore tailings deposited on the alluvial sediments also affected the physical parameters since the formed ferruginous crusts waterproofed the ground surface and may, gradually, release toxic metals when exposed to weathering and river reworking.

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RESUMO Embora vários trabalhos proponham aplicações para os resíduos finos gerados no beneficiamento de rochas ornamentais, ainda não há evidências das vantagens financeiras para tal aproveitamento. Assim, a descrição dos depósitos existentes, muitos deles construídos sem triagem ou qualquer medida de proteção ambiental, torna-se imprescindível para seu melhor gerenciamento. Este trabalho estudou a caracterização física, química e mineralógica, além da resistência mecânica de um depósito de resíduos tradicionais e de seu substrato geológico. Cerca de 75% das partículas que compõem os resíduos são menores do que 0,0625 mm e o teor de umidade varia entre 26 e 60%. Os valores de pH variam entre 8,2 e 10,5. Os elementos químicos predominantes são Si, Al, Fe e, em menor proporção, Ca, Na e K. Esses elementos compõem quartzo, plagioclásio, microclina, calcita, muscovita, biotita e zircão. Ao comparar as características dos resíduos com as do substrato geológico, não foram encontrados indícios de migração das substâncias químicas analisadas. Os Stantard Penetration Tests mostram que as camadas não apresentam resistência suficiente para receber fundações rasas. É provável que as concentrações de Fe em alguns níveis contribuam com o aumento da resistência mecânica em áreas localizadas do depósito.

ABSTRACT Although several works propose applications for the fine wastes generated by the dimension stones processing, the financial advantages of recovering these materials are not yet evident. Then, the description of the deposits, much of them constructed without screening or any environmental protection measure, becomes indispensable for their best management. This work studies the physical, chemical and mineralogical characterization, as well as the mechanical resistance of a traditional waste deposit and its geological substrate. Around 76% of the particles that compound the wastes are smaller than 0,0625 mm and their humidity vary between 26 and 60%. The pH-values are between 8.2 and 10.5. The major chemical elements are Si, Al, Fe, and, at less proportions, Ca, Na, and K. These elements compound quartz, plagioclase, microcline, calcite, muscovite, biotite, and zircon. When comparing the characteristics of the wastes with the geological substrate, indicatives of the analyzed substances' migration was not found. The Standard Penetration Tests (SPT) show that the layer´s strength is not good enough to receive shallow foundations. It is probable that Fe concentrations at some levels contribute for incrementing the deposit´s mechanical resistance.

RESUMO

RESUMO A geração de resíduos finos provenientes do processo de beneficiamento de rochas ornamentais cresce na mesma proporção da produção de chapas para a construção civil. A adoção de medidas preventivas, remediadoras e punitivas está atrelada ao conhecimento do verdadeiro potencial que esses materiais têm para causar impactos negativos ao ambiente. O objetivo deste trabalho foi simular, em laboratório, possíveis alterações na qualidade da água de recarga de aquíferos provocadas pela disposição inadequada desses resíduos. Foram realizados testes de percolação de água em colunas de solo recoberto por resíduos com diferentes taxas de umidade: resíduos sem tratamento, saídos diretamente do tear (TE); resíduos que passaram por filtro prensa (FP) para redução de umidade e resíduos secos em leito de secagem (LS). A água de percolação foi analisada para avaliar alterações em comparação com um branco ou testemunha. Não foram detectadas alterações significativas no pH da água percolada em nenhum dos casos estudados. Porém, no tratamento TE houve alterações em vários parâmetros de qualidade. A água percolada através do resíduo FP se assemelhou àquela do TE em alguns parâmetros e à do LS em outros. ­Conclui-se que os resíduos saídos diretamente da boca do tear possuem alto potencial de degradação da qualidade da água, mas a redução de umidade é eficaz para reduzir os riscos ambientais. O uso de LS pode ser um método tão eficaz quanto o FP, se conduzido de forma adequada e respeitando as normas legais.

ABSTRACT The generation of fine wastes from cutting of ornamental stones grows at the same rate of plate production for civil construction. The adoption of safe, remediating and punitive measures are linked to the knowledge of the actual potentiality that these materials have for causing negative impacts to the environment. The aim of this work was to simulate, in laboratory, possible alterations in the recharging groundwater quality provoked by the improper disposal of these wastes. We conducted tests of percolating water through soil columns covered by wastes with different humidity rates: wastes without treatment, outgoing directly from the looms (TE); wastes that passed by filter press for humidity reducing (FP) and wastes dried in a drying pond (LS). Percolated water was analyzed to evaluate alterations of its quality in relation to a blank (B) or control. Significant changes did not occur in pH-values of percolated water in any of the cases studied. However, many water quality parameters were changed during TE treatment. The water percolated through FP residues was similar to that of the looms in relation to some parameters and with the LS wastes, in others. We concluded that the wastes that just left the loom have high potential for changing water quality, but the reduction of waste´s humidity is efficient for minimizing environmental risks. The use of drying bed could be as efficient as the filter press, if conducted in a proper form and according to legal regulations.

RESUMO

The industrial treatment of dimension stones, such as marbles and granites, includes a stage of plate polishing, in which resins and abrasives are used, producing a fine grained waste with high moisture content. These wastes pass through decantation tanks in order to separate the solid and liquid phases. Until now, there is no knowledge about the mutagenic effects that this effluent can cause to organisms exposed to it. Thus, this study evaluated the mutagenic potential of dimension stone polishing wastes in onion root cells and fish erythrocytes. The onion seeds were germinated in Petri dishes with filter paper moistened in the liquid phase of the effluent. After germination, the onion roots were prepared for analysis of chromosomal aberrations in meristematic cells. The fishes were exposed during 72h to the solid phase of the effluent diluted in pure groundwater. Blood samples were used for counting of micronucleus and nuclear abnormalities. The onion seeds had similar germination and mitotic index in all treatments. However, it was observed in the seeds exposed to the polishing waste, numbers significantly higher of micronucleus, nuclear buds and other chromosomal aberrations when compared with the negative control. The fishes exposed to the waste showed numbers significantly higher of micronucleus when compared with the negative control. The fishes from all treatments showed significant increase in nuclear abnormalities when compared to the negative control. We concluded that the analysed wastes have mutagenic potential at the studied conditions; this effect can be related to the high content of phenolic compounds identified in the samples.

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Este trabalho descreve a correlação entre parâmetros de uso da terra (área agricultada, área edificada, pastagem, solo exposto e vegetação intermediária) e de qualidade da água subterrânea (pH, sólidos totais dissolvidos - STD, K+, Na+, Fe+3, Ca+2, Mg+2, NO2 -, NO3 -, P total e coliformes), no sul do estado do Espírito Santo. A delimitação da área de influência de poços e a identificação das classes de uso da terra foram feitas utilizando-se Sistema de Informações Geográficas. Por meio da análise de correlação canônica, foi possível estimar dois índices: índice de uso da terra e índice de qualidade da água, ambos padronizados. A correlação canônica foi significativa entre o primeiro par de variáveis canônicas, indicando relação linear entre os grupos. Desta forma, é possível afirmar que o uso da terra influenciou a qualidade da água subterrânea, principalmente pelo incremento da concentração de alguns elementos químicos.

This work describes the correlation between the parameters of land use (cropped area, built area, pasture, exposed soil and intermediate vegetation) and groundwater quality (pH, total dissolved solids - TDS, K+, Na+, Fe+3, Ca+2, Mg+2, NO2 -, NO3 -, total-P and coliforms) in southern of the Espírito Santo state, Brazil. The delimitation of areas that influence wells and the identification of land use classes were made using Geographical Information System. Through canonical correlation analysis, it was possible to estimate two indexes: land use index and water quality index, both standardized. The canonical correlation was significant between the first pair of canonical variables, indicating linear relationship between the groups. Thus, it was possible to confirm that land use influenced groundwater quality, mainly by the increase in the concentration of some chemical elements.