Environmental Toxicology and Pharmacology 28 (2009) 288–293
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Evaluation of the toxic and genotoxic potential of landfill leachates using bioassays Tiago Bortolotto a , Jean Borges Bertoldo a , Fernanda Zanette da Silveira a , Tamires Manganelli Defaveri a , Jacira Silvano b , Claus Tröger Pich a,∗ a b
GPIG—Grupo de Pesquisa em Imunologia e Genética, Universidade do Extremo Sul Catarinense, 88806-000 Criciúma, SC, Brazil IPAT—Instituto de Pesquisas Ambientais e Tecnológicas, Universidade do Extremo Sul Catarinense, 88806-000 Criciúma, SC, Brazil
a r t i c l e
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Article history: Received 9 October 2008 Received in revised form 30 April 2009 Accepted 7 May 2009 Available online 20 May 2009 Keywords: Landfill leachates Toxicity Genotoxicity Mutagenesis Comet assay
a b s t r a c t Landfill leachates are liquid effluents with elevated concentrations of chemical compounds that can cause serious environmental pollution. In the south of the state of Santa Catarina, Brazil, a sanitary landfill was installed that employs a system of anaerobic/facultative lagoons for the treatment of its leachate. The present work examined the toxic and genotoxic potential of untreated and treated landfill leachates using bioassays. The chemical, toxic, genotoxic and mutagenic properties of the untreated leachate and the treated leachate were determined. Examination of the chemical properties showed a marked decrease in parameters after treatment, as well as in toxicity towards all the organisms tested. The results of the comet assay demonstrated that both leachates showed genotoxicity in all of the organisms tested, indicating the persistence of genotoxic substances even after treatment. A significant decrease in micronucleated cells was detected in Geophagus brasiliensis exposed to the treated leachate compared to untreated. © 2009 Elsevier B.V. All rights reserved.
1. Introduction The exacerbated production of solid residues represents a major problem in the management and handling of urban wastes. Their accumulation leads to the generation of landfill leachates, which are liquid effluents characterised by raised concentrations of organic and inorganic compounds generated by the precipitation and penetration of water into the mass of residues undergoing biodegradation (Bernard et al., 1997; Renou et al., 2008). Since these leachates can migrate distances in excess of 100 m from the landfill, they can lead to the pollution of subterranean aquifers, as well as surface water in rivers, lakes and other water bodies (Christensen et al., 2001). The occurrence and concentration of organic and inorganic compounds, such as heavy metals, and other chemical substances in these landfill leachates, can have deleterious effects upon organisms (Schrab et al., 1993) as a result of their toxic and genotoxic potential (Leonard et al., 2004). Such properties of these and other compounds present in the leachates can be aggravated by bioaccumulation through the food chain (Sánchez-Chardi et al., 2007). The chemical composition of the leachates can vary enormously
∗ Corresponding author at: Universidade do Extremo Sul Catarinense – UNESC, Departamento de Ciências Biológicas, Av. Universitária S/N, CEP: 88806-000, Criciúma, Santa Catarina, Brazil. Tel.: +55 48 99215111. E-mail address:
[email protected] (C.T. Pich). 1382-6689/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.etap.2009.05.007
among landfills, making it difficult to assess their toxic potential and treatment (Burnley, 2007; Renou et al., 2008). However, the toxic potential of various leachates has been examined previously: tests of acute lethality or immobilisation using classical bioindicators such as Vibrio fischeri, Daphnia similis, Artemia salina and Brachydanio rerio were performed to determine the toxicity of leachates from an old landfill of solid urban residues in Rio de Janeiro, Brazil, and these tests demonstrated that the leachate receiving no treatment whatsoever presents an elevated toxic potential (Silva et al., 2004). Thamnocephalus platyurus and Brachionus calyciflorus were employed to determine the toxic potential of the leachates from two landfills in Southern Italy with results very similar to those obtained through the use of traditional bioindicators, once again indicating the high toxicity of leachates (Isidori et al., 2003). Srivastava et al. (2005) examined the toxicity of leachates through assays of subacute toxicity, reporting a decrease in the weight of bulbs of Allium cepa exposed. These results indicate that landfill leachates can have deleterious effects upon organisms of various trophic and ecological levels. Through the application of methods of cytogenetic analysis it was confirmed that these leachates can induce genetic damage in meristematic cells from the roots of A. cepa (Srivastava et al., 2005), Vicia faba (Sang and Li, 2004) and Hordeum vulgare (Sang et al., 2006) and induce chromosomal abnormalities in cells from rat bone marrow (Sang and Li, 2005). The same effect was observed using the comet and micronuclei tests in erythrocytes from peripheral blood and gill cells from goldfish (Carassius auratus) (Deguchi et al.,
T. Bortolotto et al. / Environmental Toxicology and Pharmacology 28 (2009) 288–293
2007). It is likely that these genotoxic effects are, to some extent, brought about by free radicals, since oxidative damage has also been described in cells from the heart, kidney, spleen, brain and liver (Li et al., 2006a,b) of mice. Based on the results of these studies, there is growing concern over the toxicity and genotoxicity of these leachates towards other organisms, making it necessary to create low-cost and efficacious strategies for leachate treatment (Renou et al., 2008). Various treatment processes can be employed for the leachates, among them biological processes, such as: aerobic/anaerobic biodegradation, or physico-chemical processes, including chemical oxidation (Steensen, 1997; Rivas et al., 2004), chemical precipitation (Li et al., 1999), coagulation/flocculation (Luna et al., 2007), ozonisation (Silva et al., 2004), electrochemical oxidation (Deng and Englehardt, 2007) and the Fenton process (Deng and Englehardt, 2006). Despite the large number of physico-chemical treatments available, all require a high degree of investment both for installation and maintenance. Since biological treatment presents efficiency at low cost for execution and maintenance, this has been the choice for many small municipal solid waste landfills. The biological treatment consists basically of the biodegradation of solid residues by microorganisms, which in aerobic conditions leads to the generation of carbon dioxide and sludge, or in anaerobic conditions to a complex mixture of CO2 and CH4 known as biogas (Renou et al., 2008). In June 2005, a municipal waste landfill was installed in a city in the south of the state of Santa Catarina, which receives all of the solid urban residues from the municipality. The leachates from this site are treated by means of a system of microbiological degradation, firstly in two anaerobic lagoons and subsequently in a facultative lagoon. Given the lack of studies evaluating the toxic and genotoxic potential of landfill leachates in southern Brazil, the present investigation analysed a leachate generated in a municipal solid waste landfill in the south of the state of Santa Catarina, Brazil, before and after its treatment, using the bioindicator organisms Artemia sp., Daphnia magna, Geophagus brasiliensis and A. cepa. 2. Material and methods 2.1. Collection and chemical analysis of the leachates Five-litre samples of the leachates were collected from a municipal solid waste landfill in a city in the south of Santa Catarina, Brazil, before and after treatment. These were stored in sealed polyethylene flasks and kept refrigerated until use. The chemical properties of both of the leachates were determined at the IPAT – Instituto de Pesquisas Ambientais e Tecnológicas of UNESC – Universidade do Extremo Sul Catarinense. The levels of aluminium, lead, iron, manganese and zinc were measured by means of atomic absorption spectrophotometry. Turbidimetry was used to analyse the levels of sulphate. The chemical oxygen demand (COD) was analysed by open reflux and the biochemical oxygen demand (BOD) was determined by the BOD test over five days. The pH was measured by potentiometry. After all of the analyses had been completed, the results for both of the leachates were compared to each other and to the maximum levels permitted under the Environmental Legislation of Santa Catarina – Decree no. 14.250 from 5 of June 1981, Art. 19 – Emission of liquid effluents.
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Table 1 Physico-chemical properties of the leachates before and after the treatment by anaerobic/facultative lagoons. Parameter
Untreated leachate
Treated leachate
Reduction (%)
pH COD (mg L−1 ) BOD5 (mg L−1 ) Al (mg L−1 ) Pb (mg L−1 ) Fe (mg L−1 ) Mn (mg L−1 ) Zn (mg L−1 ) SO4 2− (mg L−1 )
7.07 832.50 623.00a 0.20
