Avaliação da viabilidade do lodo de esgosto como recondicionante de solos agrícolas, após processo de atenuação natural, por meio de diferentes bioensaios

O mau gerenciamento das atividades humanas tem provocado graves impactos aos ecossistemas, comprometendo seriamente a qualidade e a manutenção das condições ambientais. Devido a intensa e crescente produção mundial de lodo de esgoto (LE), a disposição final deste resíduo vem sendo considerada um dos principais problemas ambientais. Uma alternativa mais sustentável para a destinação do LE é a sua aplicação na agricultura como recondicionante de solo, uma vez que este contém altas concentrações de matéria orgânica, além de outros nutrientes. Porém, a presença de substâncias tóxicas no LE (metais pesados, hidrocarbonetos e outros compostos orgânicos) pode inviabilizar este uso, pois existe a possibilidade destes contaminantes serem incorporados aos solos receptores, prejudicando a biota associada, bem como a saúde humana. Além disso, a possível lixiviação de substâncias tóxicas pode comprometer as águas subterrâneas e superficiais próximas da área de disposição do LE. O uso de uma bateria de bioensaios, realizados com organismos que ocupem diferentes níveis tróficos e capazes de avaliar diferentes parâmetros, é indicado para predizer os perigos da introdução de novas substâncias no ambiente. O processo de atenuação natural parece constituir uma metodologia promissora para a diminuição da toxicidade de LE. O presente trabalho teve como objetivo avaliar a efetividade do processo de atenuação natural monitorada de um LE de origem doméstica, por meio de ensaios ecotoxicológicos, realizados com diferentes sistemas-teste. Foi avaliado neste estudo o potencial tóxico, citotóxico, genotóxico, mutagênico e estrogênico do LE puro e de associações de solo/LE (proporções de 10, 25 e 50% de LE), bem como de seus extratos aquoso e orgânico, após 0, 2, 6 e 12 meses de biorremediação. A avaliação do...Inappropriate management of human activities has been inducing serious damages to the ecosystems, significantly affecting the quality and maintenance of environmental conditions. Due to the intense and increasing world production of sewage sludge (SS), the final disposal of this waste has been considered one of the main environmental problems. A more sustainable alternative to the destination of SS is its application in agriculture as soil reconditioner, since it contains high concentration of organic matter, besides other nutrients. However, the presence of toxic substances in SS (heavy metals, hydrocarbons and other organic compounds) can derail this use because such contaminants can be incorporated into soils receptors, damaging the associated biota, as well as, the human health. Moreover, the possible leaching of toxic substances can contaminate groundwater and surface waters close to the area where SS is disposal. The use of a battery of bioassays, carried out with organisms from different trophic levels and capable of evaluating several endpoints is indicated to predict the hazard of introducing new substances into the environment. The natural attenuation process seems to be a promising tool to decrease the SS toxicity. The present work aimed at evaluate the effectiveness of monitored natural attenuation process of a domestic SS by means of ecotoxicological assays, performed with different test systems. In this study, the toxic, cytotoxic, genotoxic, mutagenic and estrogenic potential of the crude SS and soil/SS associations (proportions of 10, 25 and 50% SS) was assessed, as well as their aqueous and organic extracts, after different periods of bioremediation. Evaluation of the mutagenic potential using Salmonella typhimurium, showed a positive response only for strain TA 100 in the presence of metabolic fraction, for aqueous... (Complete abstract click electronic access below)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Avaliação dos efeitos citotóxicos, genotóxicos e mutagênicos do BTEX, antes e após o processo de biorremediação por microrganismos, utilizando os sistemas teste de Allium cepa e cultura de células de mamífero

Derivados de petróleo como benzeno, tolueno, etilbenzeno e xileno (BTEX) são hidrocarbonetos monoaromáticos muito utilizados como solventes e matéria-prima em diversos processos industriais, além de estarem presentes, em grandes quantidades, nos combustíveis fósseis. Pelo seu amplo uso e alta solubilidade em água, o BTEX vem caracterizando um poluente freqüente das águas, em especial, as subterrâneas. A aplicação do processo de biorremediação parece constituir uma metodologia promissora para o tratamento de águas contaminadas por essa mistura. Testes citogenéticos são adequados e eficientes para identificar e avaliar efeitos danosos de substâncias sobre os organismos, em suas diversas concentrações e tempos de exposição. Neste trabalho foi avaliado o efeito de cinco concentrações do BTEX, antes e após o processo de biodegradação por microrganismos selecionados de efluente bruto de refinaria de petróleo, sobre os sistemas testes de Allium cepa e cultura de células HTC. A comparação do total de aberrações cromossômicas e nucleares (alterações genotóxicas) realizada entre as concentrações de BTEX não biodegradadas e biodegradadas revelou uma diminuição significativa destas anormalidades para as concentrações BTEX 1, 2 e 4. As alterações mutagênicas, avaliadas pelo teste do micronúcleo (MN) em células meristemáticas, foram significativas para as concentrações BTEX 1, 2, 4 e 5 não biodegradadas. Ao se comparar as freqüências de MN entre a concentração preparada de BTEX com a sua respectiva concentração biodegradada, observouse uma redução significativa para as biodegradadas 1 e 4. Não houve indução significativa de MN para as células F1 para nenhuma das concentrações testadas. O BTEX não provocou nenhum efeito citotóxico significativo para este organismo. O teste do MN realizado com células HTC revelou que o BTEX foi mutagênico...Oil products as benzene, toluene, ethylbenzene and xylene (BTEX) are monoaromatics hydrocarbons widely used as solvents and raw materials in several industrial processes, and are present in large quantities in fossil fuels. By its widespread use and high solubility in water, the BTEX is featuring a common pollutant of water, particularly groundwater. Implementation of the bioremediation seems to be a promising method for treatment of contaminated water with this mixture. Cytogenetic tests are appropriate and efficient to identify and assess the harmful effects of substances on the organisms in their several concentrations and time of exposure. This study evaluated the effect of five BTEX concentrations, before and after the biodegradation process by microorganisms selected from raw sewage from oil refinery using the test systems of Allium cepa and HTC cells. The comparison of total chromosomal and nuclear aberrations (genotoxic alterations) performed between BTEX concentrations bioremedied and not bioremedied showed a significant decrease of these abnormalities for BTEX concentrations 1, 2 and 4. Mutagenic alterations, evaluated by the micronucleus test (MN) in meristematic cells, were significant to the BTEX concentrations 1, 2, 4 and 5 not bioremedied. When comparing the frequencies of MN between the prepared concentration of BTEX with its concentration bioremedied, there was a significant reduction for the bioremedied 1 and 4. There was no significant induction of MN to cells F1 to any of the concentrations tested. The BTEX did not cause any significant cytotoxic effect to those organisms. The test performed with micronucleus of the HTC cells revealed that the BTEX was mutagenic, but only to the highest concentration, both before and after the biodegradation. Genotoxic damage as measured by the comet assay showed that BTEX was genotoxic for all concentrations not bioremedied, tested... (Complete abstract click electronic access below

Cellular damages in the Allium cepa test system, caused by BTEX mixture prior and after biodegradation process

Petroleum and derivatives have been considered one of the main environmental contaminants. Among petroleum derivatives, the volatile organic compounds benzene, toluene, ethylbenzene and xylene (BTEX) represent a major concern due to their toxicity and easy accumulation in groundwater. Biodegradation methods seem to be suitable tools for the clean-up of BTEX contaminants from groundwater. Genotoxic and mutagenic potential of BTEX prior and after biodegradation process was evaluated through analyses of chromosomal aberrations and MN test in meristematic and F 1 root cells using the Allium cepa test system. Seeds of A. cepa were germinated into five concentrations of BTEX, non-biodegraded and biodegraded, in ultra-pure water (negative control), in MMS 4×10 -4M (positive control) and in culture medium used in the biodegradation (blank biodegradation control). Results showed a significant frequency of both chromosomal and nuclear aberrations. The micronucleus (MN) frequency in meristematic cells was significant for most of tested samples. However, MN was not present in significant levels in the F 1 cells, suggesting that there was no permanent damage for the meristematic cell. The BTEX effects were significantly reduced in the biodegraded samples when compared to the respective non-biodegraded concentrations. Therefore, in this study, the biodegradation process showed to be a reliable and effective alternative to treat BTEX-contaminated waters. Based on our results and available data, the BTEX toxicity could also be related to a synergistic effect of its compounds. © 2011 Elsevier Ltd

Application of micronucleus test and comet assay to evaluate BTEX biodegradation

The BTEX (benzene, toluene, ethylbenzene and xylene) mixture is an environmental pollutant that has a high potential to contaminate water resources, especially groundwater. The bioremediation process by microorganisms has often been used as a tool for removing BTEX from contaminated sites. The application of biological assays is useful in evaluating the efficiency of bioremediation processes, besides identifying the toxicity of the original contaminants. It also allows identifying the effects of possible metabolites formed during the biodegradation process on test organisms. In this study, we evaluated the genotoxic and mutagenic potential of five different BTEX concentrations in rat hepatoma tissue culture (HTC) cells, using comet and micronucleus assays, before and after biodegradation. A mutagenic effect was observed for the highest concentration tested and for its respective non-biodegraded concentration. Genotoxicity was significant for all non-biodegraded concentrations and not significant for the biodegraded ones. According to our results, we can state that BTEX is mutagenic at concentrations close to its water solubility, and genotoxic even at lower concentrations, differing from some described results reported for the mixture components, when tested individually. Our results suggest a synergistic effect for the mixture and that the biodegradation process is a safe and efficient methodology to be applied at BTEX-contaminated sites. © 2012 Elsevier Ltd