ABSTRACT
The burial of bodies is a potentially polluting activity. Taking this into consideration, the aim of the present study was to verify the compliance of two cemeteries with environmental legislation and to quantify the concentrations of heavy metals in soils affected by burial activities. Physicochemical characterization of the soil was performed by analyzing control samples from areas near the cemeteries. Concentrations of cadmium, lead, chromium, nickel, zinc and copper were determined using high-resolution continuum source atomic absorption spectrometry. The two cemeteries had unsatisfactory properties for the retention of metal cations, with clay percentages ranging from 15.40 to 41.40% and sand percentages ranging from 28.75 to 66.85%. The control samples presented low cation exchange capacity (12.27 to 22.73 cmolc/dm³) and high aluminum (Al3+) saturation (66.74 to 90.16%). Although neither of the two cemeteries had concentrations above the limits established for the metals analyzed by Resolution No. 420/2009 of the National Environment Council, the contaminants may be leaching to groundwater due to inadequate soil characteristics.
Keywords:
HR-CS AAS; cation exchange capacity; contaminants; necro-leachate; heavy metals
RESUMO
O sepultamento de corpos é uma atividade potencialmente poluidora. Este trabalho teve como objetivo verificar a adequação das áreas de dois cemitérios públicos à legislação ambiental e à atividade cemiterial e quantificar a concentração de metais pesados nos solos que estão sob influência desses empreendimentos. Realizou-se a caracterização físico-química do solo, com a análise de amostras testemunha de solo de cada cemitério. Também foram determinadas as concentrações dos metais pesados: cádmio, chumbo, cromo, níquel, zinco e cobre, por meio de espectrometria de absorção atômica de alta resolução com fonte contínua. As áreas dos cemitérios apresentam condições insatisfatórias para a retenção de íons catiônicos metálicos, com percentuais de argila variando entre 15,40 e 41,40% e de areia entre 28,75 e 66,85%. Os solos testemunha apresentaram reduzida capacidade de troca de cátions entre 12,27 e 22,73 cmolc/dm³) e elevada saturação por alumínio entre 66,74 e 90,16%. Apesar de nenhum dos cemitérios apresentar concentrações dos metais analisados acima dos limites de prevenção estabelecidos pela Resolução nº 420/2009 do Conselho Nacional do Meio Ambiente, em função das características dos solos, os contaminantes podem estar sendo lixiviados para os recursos hídricos subjacentes.
Palavras-chave:
HR-CS AAS; capacidade de troca catiônica; contaminantes; necro-lixiviado; metais tóxicos
INTRODUCTION
The environment depends on the integrated functioning of many components, including soil, which performs important ecological functions. In urban areas, humans have drastically modified soil characteristics, in addition to using this resource for storing undesirable materials. Many of these materials have contaminants that, when not assimilated by the soil, percolate through the unsaturated zone and reach the water table, becoming potential environmental pollutants (AHARONI et al., 2020AHARONI, I., SIEBNER, H., YOGEV, U., DAHAN, O. Holistic approach for evaluation of landfill leachate pollution potential-From the waste to the aquifer. Science of The Total Environment, v. 741, 40367, 2000. https://doi.org/10.1016/j.scitotenv.2020.140367
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).
Traditional burial is a practice in urban areas that generates byproducts, such as necro-leachate, which is a potential liquid pollutant that changes the physicochemical and biological characteristics of the bedrock (MAJGIER & RAHMONOV, 2012MAJGIER, L.; RAHMONOV, O. Selected chemical properties of Necrosols from the abandoned cemeteries Słabowo and Szymonka. Bulletin of Geography, Physical Geography Series, v. 5, n. 1, p. 43-55, 2012. http://doi.org/10.2478/v10250-012-0003-8
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; CRUZ et al., 2017CRUZ, N. J. T.; LEZANA, Á. G. R.; SANTOS, P. D. C. F.; PINTO, I. M. B. S.; ZANCAN, C. SOUZA, G. H. S. Environmental impacts caused by cemeteries and crematoria, new funeral technologies, and preferences of the Northeastern and Southern Brazilian population as for the funeral process. Environmental Science and Pollution Research, v. 24, n. 31, 24121-24134, 2017. https://doi.org/10.1007/s11356-017-0005-3
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). Necro-leachate has many components originating from the decomposition of bodies, coffins, adornments, and fabrics used to dress the bodies as well as products and substances introduced into the body throughout the individual’s life (WILLIAMS et al., 2009WILLIAMS, A.; TEMPLE, T.; POLLARD, S. J.; JONES, R. J.; RITZ, K. Environmental considerations for common burial site selection after pandemic events. In: Criminal and environmental soil forensics. Dordrecht: Springer, 2009.; FIEDLER et al., 2012FIEDLER, S.; BREUER, J.; PUSCH, C. M.; HOLLEY, S.; WAHL, J.; INGWERSEN, J.; GRAW, M. Graveyards - special landfills. Science of the Total Environment, v. 419, p. 90-97, 2012. https://doi.org/10.1016/j.scitotenv.2011.12.007
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; JONKER & OLIVIER, 2012JONKER, C.; OLIVIER, J. Mineral contamination from cemetery soils: case study of Zandfontein Cemetery, South Africa. International Journal of Environmental Research and Public Health, v. 9, n. 2, p. 511-520, 2012. https://doi.org/10.3390%2Fijerph9020511
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).
The first registered study on the environmental impact of cemeteries was developed in Europe in 1951 by Van Haaren (UÇISIK & RUSHBROOK, 1998UCISIK, A. S.; RUSHBROOK, P.; WORLD HEALTH ORGANIZATION. The impact of cemeteries on the environment and public health: an introductory briefing. Copenhagen: WHO Regional Office for Europe, 1998. 15 p.). In Brazil, bacteriological contamination of the water table by microorganisms from decomposing bodies was detected in a study conducted in the state of São Paulo in 1991. Henceforth, several studies have addressed the impact of burial activities on the environment and public health (PACHECO, 2000Pacheco, A. Cemitério e meio ambiente. [Tema de livre docência]. São Paulo: University of São Paulo, 2000.).
According to Barros et al. (2008BARROS Y. J.; FREITAS MELO, V. D.; ZANELLO, S.; LIMA ROMANÓ, E. N. D.; LUCIANO, P. R. Teores de metais pesados e caracterização mineralógica de solos do Cemitério Municipal de Santa Cândida, Curitiba (PR). Revista Brasileira de Ciência do Solo, v. 32, n. 4, p. 1763-1773, 2008. https://doi.org/10.1590/S0100-06832008000400041
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), most studies investigating the contamination of natural resources by inappropriate burial activities have emphasized nonmetallic pollutants, especially those of a microbiological origin in groundwater. However, more recent studies, such as those developed by Barros et al. (2008BARROS Y. J.; FREITAS MELO, V. D.; ZANELLO, S.; LIMA ROMANÓ, E. N. D.; LUCIANO, P. R. Teores de metais pesados e caracterização mineralógica de solos do Cemitério Municipal de Santa Cândida, Curitiba (PR). Revista Brasileira de Ciência do Solo, v. 32, n. 4, p. 1763-1773, 2008. https://doi.org/10.1590/S0100-06832008000400041
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), Jonker and Olivier (2012JONKER, C.; OLIVIER, J. Mineral contamination from cemetery soils: case study of Zandfontein Cemetery, South Africa. International Journal of Environmental Research and Public Health, v. 9, n. 2, p. 511-520, 2012. https://doi.org/10.3390%2Fijerph9020511
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), Fiedler et al. (2012FIEDLER, S.; BREUER, J.; PUSCH, C. M.; HOLLEY, S.; WAHL, J.; INGWERSEN, J.; GRAW, M. Graveyards - special landfills. Science of the Total Environment, v. 419, p. 90-97, 2012. https://doi.org/10.1016/j.scitotenv.2011.12.007
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), Amuno (2013AMUNO, S. A. Potential ecological risk of heavy metal distribution in cemetery soils. Water Air Soil Poll, v. 224, n. 2, p. 224-1435, 2013. http://doi.org/10.1007/s11270-013-1435-2
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), Floriani (2013), Silva (2016SILVA, R. B. P. D.; CAMPOS, M. C. C.; SILVA, L. S.; FILHO, E. G. D. B.; LIMA, A. F. L. D.; PINHEIRO, E. N.; CUNHA, J. M. Concentration of Heavy Metals in Soils under Cemetery Occupation in Amazonas, Brazil. Soil and Sediment Contamination: An International Journal, v. 29, n. 2, p. 192-208, 2020. https://doi.org/10.1080/15320383.2019.1696280
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), and Rocha (2016ROCHA, L. A. G. Estudo do potencial contaminante do Cemitério Jardim, Botucatu-SP. [Master’s thesis]. Botucatu: São Paulo State University, 2016.), have quantified heavy metals in soils. The most frequently found heavy metals above legally established limits are chromium and lead (BARROS et al., 2008BARROS Y. J.; FREITAS MELO, V. D.; ZANELLO, S.; LIMA ROMANÓ, E. N. D.; LUCIANO, P. R. Teores de metais pesados e caracterização mineralógica de solos do Cemitério Municipal de Santa Cândida, Curitiba (PR). Revista Brasileira de Ciência do Solo, v. 32, n. 4, p. 1763-1773, 2008. https://doi.org/10.1590/S0100-06832008000400041
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); chromium, copper, zinc, rubidium, strontium, cesium, and lead (JONKER & OLIVIER, 2012JONKER, C.; OLIVIER, J. Mineral contamination from cemetery soils: case study of Zandfontein Cemetery, South Africa. International Journal of Environmental Research and Public Health, v. 9, n. 2, p. 511-520, 2012. https://doi.org/10.3390%2Fijerph9020511
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); arsenic, chromium, and lead (AMUNO, 2013AMUNO, S. A. Potential ecological risk of heavy metal distribution in cemetery soils. Water Air Soil Poll, v. 224, n. 2, p. 224-1435, 2013. http://doi.org/10.1007/s11270-013-1435-2
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); and iron, chromium, copper, nickel, lead, and zinc (SILVA, 2019SILVA, R. B. P. D.; CAMPOS, M. C. C.; SILVA, L. S.; FILHO, E. G. D. B.; LIMA, A. F. L. D.; PINHEIRO, E. N.; CUNHA, J. M. Concentration of Heavy Metals in Soils under Cemetery Occupation in Amazonas, Brazil. Soil and Sediment Contamination: An International Journal, v. 29, n. 2, p. 192-208, 2020. https://doi.org/10.1080/15320383.2019.1696280
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).
According to He et al. (2004HE, Z. L.; ZHANG, M. K.; CALVERT, D. V.; STOFFELLA, P. J.; YANG, X. E.; YU, S. Transport of heavy metals in surface runoff from vegetable and citrus fields. Soil Science Society of America Journal, v. 68, p. 1662-1669, 2004. https://doi.org/10.2136/sssaj2004.1662
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), the availability and mobility of heavy metals are controlled by chemical and biochemical processes such as precipitation-dissolution, adsorption-desorption, complexation-dissociation, and oxidation-reduction. Moreover, these processes are affected by pH and biological processes as well as the environment and the chemical toxicity of the element (OLIVEIRA, 2012OLIVEIRA, M. D. R. Avaliação da contaminação do solo pela disposição inadequada de resíduos sólidos em Romaria-MG. [Master’s thesis]. Uberlândia: Federal University of Uberlândia, 2012.). In the case of cemeteries, where burials normally occur in deep layers of the soil (1.5 to 1.8 m), the amount and quality of clay are determinant factors of heavy-metal adsorption capacity (BARROS et al., 2008BARROS Y. J.; FREITAS MELO, V. D.; ZANELLO, S.; LIMA ROMANÓ, E. N. D.; LUCIANO, P. R. Teores de metais pesados e caracterização mineralógica de solos do Cemitério Municipal de Santa Cândida, Curitiba (PR). Revista Brasileira de Ciência do Solo, v. 32, n. 4, p. 1763-1773, 2008. https://doi.org/10.1590/S0100-06832008000400041
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).
Most studies quantifying metals in soils affected by cemeteries have not considered physicochemical characteristics, and no studies have analyzed the natural amount of metals in soils of the surrounding region. Resolution No. 335/2003 of the National Environment Council (Conselho Nacional do Meio Ambiente - CONAMA, 2003), which regards the environmental licensing of cemeteries as well as issues involving construction aspects and cemetery regulations, establishes minimal norms that must be observed regarding the depth of the grave and properties of the subsoil. This resolution also stipulates the distance from the grave to the maximum height of the water table, practices for the burial of bodies, the location of the burial area, practices that enable gas exchange, and criteria for horizontal cemeteries in areas of springs that supply water for human use (BRAZIL, 2003).
When the characteristics of the soil at burial sites are unsuitable for the retention and filtration of the necro-leachate, the liquid lixiviated through the unsaturated zone reaches the underlying aquifer. The conditions of the unsaturated zone determine attenuation processes and the eventual elimination of chemicals or the lixiviation of necro-leachate and the contamination of surface and groundwater bodies (OLIVEIRA et al., 2013OLIVEIRA, B.; QUINTEIRO, P.; CAETANO, C.; NADAIS, H.; ARROJA, L.; FERREIRA DA SILVA, E.; SENOS MATIAS, M. Burial grounds’ impact on groundwater and public health: an overview. Water and Environment Journal, v. 27, n. 1, p. 99-106, 2013. https://doi.org/10.1111/j.1747-6593.2012.00330.x
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; IEPA, 2015SCOTTISH ENVIRONMENT PROTECTION AGENCY (SEPA). Guidance on Assessing the Impacts of Cemeteries on Groundwater. Land Use Planning System. Guidance Note. 2015.). Unlike most organic contaminants, metals are not degraded or promptly detoxified by microorganisms, in such a way these elements pose a greater pollution problem over time (OLIVEIRA et al., 2010OLIVEIRA, L. F.; LEMKE-DE-CASTRO, M. L.; RODRIGUES, C.; BORGES, J. D. Isotermas de sorção de metais pesados em solos do cerrado de Goiás. Revista Brasileira de Engenharia Agrícola e Ambiental, Agriambi, v. 14, p. 776-782, 2010. https://doi.org/10.1590/S1415-43662010000700014
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).
The aim of the present study was to identify the adequacy of burial activities at two public urban cemeteries located in the municipality of Lages, southern Brazil, to quantify levels of heavy metals in the soil affected by these activities, and to compare the results to the limits established by the Brazilian environmental legislation.
METHODOLOGY
Study area
The municipality of Lages is located in the state of Santa Catarina, in southern Brazil, and has a population of 157,727 residents, 98.22% of whom live in urban areas and 1.78% live in rural areas (IBGE, 2010INSTITUTO BRASILEIRO DE GEOGRAFIA E ESTATÍSTICA (IBGE). Características da População e dos domicílios. 2010.). The city has two public cemeteries in urban areas: Nossa Senhora da Penha (NCP) and Cruz das Almas (CA). The NCP cemetery is located between the following geographic coordinates: 50°17’29.6” to 50°17’34.7” W and 27°48’29.6” to 27°48’37.4” S. It has been operating for approximately 75 years, occupying an approximate area of 60,817 m². NCP is the largest public urban cemetery in the city, with an average of 44 burials per month. It has a slope of approximately 30 m between the highest and the lowest points. The surroundings are mostly occupied by residences and the cemetery is close to water bodies. The CA cemetery is located between the following geographic coordinates: 50°20’13.7” to 50°20’06.5” W and 27°49’36.8” to 27°49’46.5” S. It has been operating for 127 years and is the second largest public urban cemetery in Lages, covering an area of 38,824 m². It is located on a water divide and has an average of 13 burials per month. Residences and businesses, such as gas stations, funeral homes, and commercial buildings, compose the surrounding area. This study received authorization from the city of Lages, which is responsible for the surveyed cemeteries.
Sampling
For the CA cemetery, control soil samples were collected from adjacent areas unaffected by human activities to represent the levels of metals normally found in soils outside the study area. A total of ten soil samples were collected from the cemetery itself. The sampling criterion was the direction of the hydrostatic flow, which normally follows the surface topography. The sampling points inside and outside the CA cemetery are shown in Figure 1. For the NCP cemetery, 13 samples were collected from within the cemetery, in addition to collecting three control samples, two samples from a swamp area between the cemetery and a water body (not identified) located south-southwest to the cemetery, and three samples of alluvial soil, which were collected from the eastern bank of the creek (Figure 2). Samples were collected at depths between 160 and 180 cm, utilizing Dutch and screw augers, following Technical Norm No. 15,492 (ABNT, 2007ASSOCIAÇÃO BRASILEIRA DE NORMAS TÉCNICAS (ABNT) NBR 15.492: Sondagem de reconhecimento para fins de qualidade ambiental. Rio de Janeiro: Procedimento, 2007.). In cases where the bedrock was located at less than 160 cm from the ground, samples were collected as close to the bedrock as possible. All samples were dried in an oven at 65°C for at least 24 hours, ground, and sieved with a 0.212 mm/μm stainless-steel sieve (65 mesh).
Physicochemical characterization
Physicochemical analyses of the control soil samples were conducted (three duplicate samples from NCP and three from CA). The analyses were performed at the Soil Analysis Laboratory of the Santa Catarina Agricultural-Livestock Research and Extension Company (Empresa de Pesquisa Agropecuária e Extensão Rural de Santa Catarina - EPAGRI) in the city of Chapecó, Brazil, which is accredited by the Official Network of Soil Analysis Laboratories (Rede Oficial de Laboratórios de Análise de Solo e de Tecido Vegetal nos Estados do Rio Grande do Sul e de Santa Catarina - ROLAS). The physical analysis of the soils consisted of the quantification of particle size following the methods described by Embrapa (1997EMPRESA BRASILEIRA DE PESQUISA AGROPECUÁRIA (EMBRAPA). Manual de métodos de análise de solo. Distrito Federal: Embrapa, 1997. 212 p.) and Klein (2008KLEIN, V. A. Física do solo. Passo Fundo: University of Passo Fundo, 2008. 212 p.). The chemical analysis was performed for the determination of organic matter (OM), potential of hydrogen in water (pH H2O), available phosphorus (P; Mehlich), exchangeable potassium (K; Mehlich), and exchangeable aluminum (Al), calcium (Ca), and magnesium (Mg) using methods described by Tedesco et al. (1995TEDESCO, M. J.; GIANELLO, C.; BISSANI, C. A.; BOHNEN, H.; VOLKWEISS, S. J. Análises de solo, plantas e outros materiais. Porto Alegre: Rio Grande do Sul Federal University, 1995.) (standards of the Brazilian Soil Science Society). Potential acidity (H + Al), cation exchange capacity (CEC), Al (M-value), and saturation percentage of the CEC at pH 7.0 (bases, K, Ca, Mg) were obtained from mathematical calculations. The physicochemical characterization was only performed in the control samples of both cemeteries, as the physicochemical characteristics of the samples from within the cemeteries have been altered, making the analysis of the environmental adequacy of these soils for the burial activity unfeasible.
Determination of heavy metals
Acid digestion and the determination of heavy metals were performed at the Routine Water and Waste Analysis Laboratory of the Department of Environmental and Sanitary Engineering of Universidade do Estado de Santa Catarina following the methods described by the United States Environmental Protection Agency (USEPA, 1996UNITED STATES ENVIRONMENTAL PROTECTION AGENCY (USEPA). Method 3050B: acid digestion of sediments, sludges and soils. In: Test methods for evaluating solid waste, physical/chemical methods. Washington DC: USEPA, 1996.). Levels of cadmium (Cd), lead (Pb), copper (Cu), chromium (Cr), nickel (Ni), and zinc (Zn) were determined in the samples from the NCP cemetery, CA cemetery, and control samples for both cemeteries. The minimum detection limits were 0.0004 mg/kg for Cd; 0.005 mg/kg for Pb; 0.001 mg/kg for Cu; 0.005 mg/kg for Cr; 0.012 mg/kg for Ni; and 0.001 mg/kg for Zn. The digestion of the samples followed the USEPA 3050B method (USEPA, 1996UNITED STATES ENVIRONMENTAL PROTECTION AGENCY (USEPA). Method 3050B: acid digestion of sediments, sludges and soils. In: Test methods for evaluating solid waste, physical/chemical methods. Washington DC: USEPA, 1996.), using reagents with Merck analytical standards. Digestion of the samples was performed with nitric acid (HNO3), hydrochloric acid (HCl), and hydrogen peroxide (H2O2). Metals were determined using the direct air-acetylene flame method through high-resolution continuum source atomic absorption spectrometry (HR-CS AAS), using the Analytik Jena contrAA 700 spectrometer. The equipment was calibrated with stock solutions prepared for each metal of interest based on the calibration curves created from reference stock solutions. Descriptive statistics were performed to determine the behavior of the data. Geographical spatialization of the data was conducted using the kriging method with the aid of the ArcGIS 10.1 software. Concentrations of metals detected in the samples were compared with the Prevention and Intervention Values established by CONAMA (2009BRAZIL. Resolução nº 420, de 28 de dezembro de 2009. Ministério do Meio Ambiente. Conselho Nacional de Meio Ambiente. Brasília: Diário Oficial [da] República Federativa do Brasil, Poder Executivo, 2009.) Resolution No. 420/2009.
RESULTS AND DISCUSSION
Physicochemical characterization
The depth of the soils ranged from 50 to 180 cm in the NCP cemetery and from 95 to 180 cm in the CA cemetery. The shallow depth at some sampling points is due to the closeness to the bedrock, with graves built directly over it at these spots. The depth of the saturated zone and the type of geological material are determinant factors for the filtering of liquids resulting from body decomposition (SILVA & MALAGUTTI FILHO, 2008SILVA, R. D. C.; MALAGUTTI FILHO, W. Cemitérios como áreas potencialmente contaminadas. Revista Brasileira de Ciências Ambientais, n. 9, p. 26-35, 2008.), as this zone serves as a filter and adsorbent (UÇISIK & RUSHBROOK, 1998UCISIK, A. S.; RUSHBROOK, P.; WORLD HEALTH ORGANIZATION. The impact of cemeteries on the environment and public health: an introductory briefing. Copenhagen: WHO Regional Office for Europe, 1998. 15 p.). However, there are no reference values for these characteristics. CONAMA (2006BRAZIL. Resolução nº 368, de 28 de março de 2006. Ministério do Meio Ambiente. Conselho Nacional de Meio Ambiente. Brasília: Diário Oficial [da] República Federativa do Brasil, Poder Executivo, 2006.) Resolution No. 368/2006 only establishes that the lowest level of the graves must be at least 150 cm above the highest level of the water table measured at the end of the rainy season (BRAZIL, 2006BRAZIL. Resolução nº 368, de 28 de março de 2006. Ministério do Meio Ambiente. Conselho Nacional de Meio Ambiente. Brasília: Diário Oficial [da] República Federativa do Brasil, Poder Executivo, 2006.).
The physicochemical characteristics of the control soils from both cemeteries are presented in Table 1. Both of them had similar mean percentages of clay and sand. The soils from the CA cemetery had a predominance of sand (47.32%), followed by clay (29.40%), whereas the soils from the NCP cemetery were predominantly clay (38.07%), followed by sand (34.13%). The soils had a suitable texture for the burial activity, which, according to Silva (1995, apudSILVA & MALAGUTTI FILHO, 2008SILVA, R. D. C.; MALAGUTTI FILHO, W. Cemitérios como áreas potencialmente contaminadas. Revista Brasileira de Ciências Ambientais, n. 9, p. 26-35, 2008.), ranges from 20 to 40% of clay to favor aerobic decomposition and the drainage of the necro-leachate. Soils composed of a mixture of clay and sand of low porosity and a small to fine grain texture maximize the retention of degradation products (UÇISIK & RUSHBROOK, 1998UCISIK, A. S.; RUSHBROOK, P.; WORLD HEALTH ORGANIZATION. The impact of cemeteries on the environment and public health: an introductory briefing. Copenhagen: WHO Regional Office for Europe, 1998. 15 p.) due to the larger specific surface area and, consequently, higher CEC. According to the Potash and Phosphate Institute (1998), the CEC depends on the amount and type of clay and organic matter. Higher CEC values are commonly found in weathered soils.
Soils from the NCP cemetery had CEC values ranging from 12.55 to 22.73 cmolc/dm³ and those from the CA cemetery had values ranging from 12.27 to 16.73 cmolc/dm³, suggesting that the predominant clay minerals in both cemeteries are kaolinite, which has a CEC between 5 and 15 cmolc/dm³, and illite, which has a CEC between 10 and 50 cmolc/dm³ (RONQUIM, 2010RONQUIM, C. C. Conceitos de fertilidade do solo e manejo adequado para as regiões tropicais. Embrapa Monitoramento por Satélite. Boletim de Pesquisa e Desenvolvimento. Campinas: Embrapa Monitoramento por Satélite, 2010. 26 p.). According to Becegato et al. (2006BECEGATO, V. A.; FERREIRA, F. J. F.; MACHADO, W. C. P.; CASSOL, P. C.. Monitoramento ambiental da radioatividade do U, Th e K oriunda de fertilizantes fosfatados em área agrícola no sul do Brasil. Revista de Estudos Ambientais, v. 1, p. 5-19., 2006.), clay soils that have 2:1 clay minerals (montmorillonite) have a higher CEC compared with soils with a sandy/clay texture. Moreover, high amounts of sand result in less water retention and proneness to the lixiviation of cations (BECEGATO et al., 2006BECEGATO, V. A.; FERREIRA, F. J. F.; MACHADO, W. C. P.; CASSOL, P. C.. Monitoramento ambiental da radioatividade do U, Th e K oriunda de fertilizantes fosfatados em área agrícola no sul do Brasil. Revista de Estudos Ambientais, v. 1, p. 5-19., 2006.). A low CEC indicates that the soil has little capacity for retaining cations, resulting in greater loss through lixiviation (RONQUIM, 2010RONQUIM, C. C. Conceitos de fertilidade do solo e manejo adequado para as regiões tropicais. Embrapa Monitoramento por Satélite. Boletim de Pesquisa e Desenvolvimento. Campinas: Embrapa Monitoramento por Satélite, 2010. 26 p.).
Another important characteristic to consider is the fact that the metal-adsorption of soils depends on the aluminum (Al3+) concentration, as this metal affects the CEC. Al3+ was high in the control soils for both cemeteries, with values ranging from 66.74% (NCP16) to 90.16% (NCP15). The exception was CA13, for which 0.0% of Al3+ was found. The presence of this element in the CEC indicates that the metal is adsorbed by negative charges (PPI, 1998POTASH AND PHOSPHATE INSTITUTE (PPI). Manual internacional da fertilidade do solo. Tradução e adaptação de Alfredo Scheid Lopes. 2ª ed. ampliada e revisada. Piracicaba: POTAFOS, 1998. 177 p.; ZAMBROSI et al., 2007ZAMBROSI, F. C. B.; ALLEONI, L. R. F.; CAIRES, E. F. Teores de alumínio trocável e não trocável após calagem e gessagem em Latossolo sob sistema plantio direto. Bragantia, v. 66, n. 3, p. 487-495, 2007. https://doi.org/10.1590/S0006-87052007000300016
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), preventing other cations, such as Cr, Cd, Pb and Cu, to be adsorbed by negative charges.
The amount of organic matter in the study areas ranged from 14 g/dm³ (NCP14) to 27 g/dm³ (NCP15 and CA12). Soils with more than 60 g/dm3 normally indicate an accumulation of organic matter due to poor drainage conditions or high acidity (CÓ JR., 2011CÓ JR., C. Matéria orgânica, capacidade de troca catiônica e acidez potencial no solo com dezoito cultivares de cana-de-açúcar. [Doctoral dissertation]. Jaboticabal: São Paulo State University, 2011.). The pH was between 4.0 and 5.0 for all soils, except for that collected from CA13 (pH 6.10). The NCP and CA cemeteries had a mean pH of 4.2 and 4.8, respectively. The pH value exerts a strong influence on the dynamics of metal cations, which are more mobile under conditions of low pH (RIEUWERTS et al., 2006RIEUWERTS, .J S.; ASHMORE, M. R.; FARAGO, M. E.; THORNTON, I. The influence of soil characteristics on the extractability of Cd, Pb and Zn in upland and moorland soils. Science of the total Environment, v. 366, n. 2-3, p. 864-875, 2006. https://doi.org/10.1016/j.scitotenv.2005.08.023
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).
According to He et al. (2005), the availability and mobility of heavy metals are controlled by chemical and biochemical processes such as precipitation-dissolution, adsorption-desorption, complexation-dissociation, and oxidation-reduction. However, these processes are affected by pH and biological processes as well as the environment itself and the chemical toxicity of the element (OLIVEIRA, 2012OLIVEIRA, M. D. R. Avaliação da contaminação do solo pela disposição inadequada de resíduos sólidos em Romaria-MG. [Master’s thesis]. Uberlândia: Federal University of Uberlândia, 2012.). Although clay was within the recommended amount for both criteria (SILVA, 1995, apudSILVA & MALAGUTTI FILHO, 2008SILVA, R. D. C.; MALAGUTTI FILHO, W. Cemitérios como áreas potencialmente contaminadas. Revista Brasileira de Ciências Ambientais, n. 9, p. 26-35, 2008.), chemical characteristics such as the CEC, Al3+ saturation in CEC, and pH, indicate that soils from both cemeteries are prone to the lixiviation of cations and possible contaminants, which places groundwater at risk.
Heavy metals in soil
In the control samples, the concentrations of heavy metals were lower than the minimum detection limits of the spectrometer or lower than the mean values obtained in the samples from the cemeteries, except for Cr in the NCP cemetery and Pb in the CA cemetery (Table 2). For NCP, the mean concentration of Cr was higher in the control samples compared with the mean concentration in the samples obtained from the cemetery. However, Cr levels were higher at NCP04 and NCP13 than the levels in the control samples.
Considerable variability was found in the levels of Cu, Cr, Pb, Zn, and Ni at both cemeteries, ranging from 55.83% to 104.40% in NCP and 29.44% to 144.50% in CA (Table 2). This variability may be attributed to the geology of the area, which is influenced by the Lages Dome, the sedimentary extracts of which were mixed by the Botucatu-Pirambóia, Teresina and Rio do Rastro formations. This combination affected the mineralogical and textural compositions of the soils (BECEGATO et al., 2019BECEGATO, V. R.; BECEGATO, V. A.; BARCAROLLI, I. F.; CONTE, G.; BAUM, C. A.; LAVNITCKI, L.; PAULINO, A. T. Geoquímica ambiental aplicada na avaliação dos solos de um aterro sanitário desativado no município de Lages-SC. In: ZUFFO, A. M. (Org.). A produção do conhecimento nas ciências agrárias e ambientais. 3ª ed. Ponta Grossa: Atena Editora, 2019. p. 194-211.) and, consequently, their metal-retaining capacity. Higher concentrations of Cu, Ni, Zn, and Cd were detected at lower topographic heights, which may be associated with lixiviation of heavy metals and their accumulation, as the terrain topography normally follows the direction of the hydrostatic flow. In the case of the CA cemetery, the variability may also be due to the age of the burials, which are more recent in the southern and southwestern portions of the cemetery.
Comparing the total amounts of Cu, Cr, Pb, Ni, Zn, and Cd in the soil samples from the NCP and CA cemeteries with the Prevention and Intervention Values stipulated by the environmental legislation (CONAMA Resolution No. 420/2009BRAZIL. Resolução nº 420, de 28 de dezembro de 2009. Ministério do Meio Ambiente. Conselho Nacional de Meio Ambiente. Brasília: Diário Oficial [da] República Federativa do Brasil, Poder Executivo, 2009.), all concentrations at both cemeteries were below the established limits. The Prevention Value is the concentration limit of a given substance that enables the soil to fulfill its main functions, whereas the Intervention Value is the concentration of a substance above which there are potential risks to human health (BRAZIL, 2009BRAZIL. Resolução nº 420, de 28 de dezembro de 2009. Ministério do Meio Ambiente. Conselho Nacional de Meio Ambiente. Brasília: Diário Oficial [da] República Federativa do Brasil, Poder Executivo, 2009.). Nevertheless, due to the broad pedological variability in Brazil, the Intervention and Prevention Values may not reflect the actual situation of some places suited to the existing types of pedology.
Rocha (2016ROCHA, L. A. G. Estudo do potencial contaminante do Cemitério Jardim, Botucatu-SP. [Master’s thesis]. Botucatu: São Paulo State University, 2016.) also evaluated heavy metals in cemetery soils and found values below the Prevention Values proposed by CONAMA Resolution No. 420/2009 (BRAZIL, 2009BRAZIL. Resolução nº 420, de 28 de dezembro de 2009. Ministério do Meio Ambiente. Conselho Nacional de Meio Ambiente. Brasília: Diário Oficial [da] República Federativa do Brasil, Poder Executivo, 2009.). In a pioneering study on soil contamination due to cemetery activities, Spongberg and Becks (2000SPONGBERG, A. L.; BECKS, P. M. Inorganic soil contamination from cemeteries leeched. Water Air Soil Poll, v. 117, n. 1, p. 313-327, 2000. http://doi.org/10.1023/A:1005186919370
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) found values similar to those found in the present study: Cu = 0.27 mg/kg; Zn = 2.64 mg/kg; Pb = 0.41mg/kg; and Cr = 0.16 mg/kg. As the soils from the NCP and CA cemeteries have clay content suitable for the burial activity and have peculiarities in their topography, the behavior of metals in the area consists in a relevant information.
The spatialization of the concentration of metals in the NCP cemetery is demonstrated in Figure 3. In Figures 3a and 3b, the resemblance between the spatialization of the concentrations of Cd and Zn may be due to the fact that Cd is rarely found in its pure form in nature, and its presence in the environment is directly related to zinc ore (ADRIANO 1986, apudMELLIS, 2006MELLIS, E. V. Adsorção e dessorção de Cd, Cu, Ni e Zn, em solo tratado com lodo de esgoto. [Doctoral dissertation]. Piracicaba: University of São Paulo, 2006.). Nascimento et al. (2010NASCIMENTO, R. S. D. M. P.; SANTOS CARVALHO, G.; PAIXÃO PASSOS, L.; MARQUES, J. Lixiviação de chumbo e zinco em solo tratado com resíduos de siderurgia. Pesquisa Agropecuária Tropical, v. 40, n. 4, p. 497-504, 2010. https://doi.org/10.1590/S1983-40632010000400001
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) state that Cd, Zn, and Ni pose higher risks of contaminating groundwater due to their greater mobility through soil compared with Pb, Cr, and Cu. Regarding concentrations of Cu and Ni in the NCP cemetery, the points with higher levels of both metals were located at lower topographic altitudes. Cr concentrations were higher than Pb concentrations, even at lower topographic altitudes. However, in Figure 3f it is verified that the control sampling points also had high Cr concentrations, which may be related to the geology of the area. Regarding the spatialization of the metals studied in the CA cemetery (Figures 4b and 4c), control sampling point CA13 (Figures 4a, 4b, and 4c) had slightly high amounts of Cd and Zn, and the highest Pb concentration may be related to another contamination source or from the cemetery itself. This behavior may be due to the fact that the texture of the soils is mainly composed of sand from the Botucatu-Pirambóia formation, which is more porous, thereby facilitating the percolation of contaminants. Cd and Zn concentrations had a similar spatial distribution, with higher concentrations in sites at lower topographic altitudes (Figures 4b and 4c). Cu, Cr, and Ni levels exhibited a similar behavior (Figures 4d, 4e, and 4f), with low concentrations at the control sampling points and high levels at a lower topographic altitude, demonstrating the possibility of lixiviation and the accumulation of contaminants in the area. Burial age is another possible factor of influence, considering that the areas at lower altitudes correspond to more recent burials.
Spatialization of the concentration of metals Cd (A), Zn (B), Cu (C), Ni (D), Pb (E) and Cr (F) in the soil of Nossa Senhora da Penha cemetery.
Spatialization of the concentration of metals Pb (A), Cd (B), Zn (C), Cu (D), Cr (E) e Ni (F) in the soil of Cruz das Almas cemetery.
CONCLUSIONS
The studied cemeteries were in compliance with the legislation that guides their activities. Soils in the areas of both cemeteries had physical characteristics suitable for the burial activity. However, the analysis of the chemical characteristics demonstrated that the soils do not have the potential to adsorb metallic cations, which poses a risk of groundwater contamination.
Concentrations of metals were below the Prevention and Intervention Values for soils established by CONAMA (2009) Resolution No. 420/2009. Nevertheless, the spatialization of the metal concentrations in the investigated areas indicates higher concentrations of all elements at lower topographic altitudes. There is need for soil quality regulations regarding chemical substances at limits that are suitable for the different pedologies of the country.
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Funding: Fundação de Amparo à Pesquisa e Inovação do Estado de Santa Catarina - process number 05/2015.
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3
Reg. ABES: 20200030
Publication Dates
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Publication in this collection
08 Nov 2021 -
Date of issue
Sep-Oct 2021
History
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Received
30 Jan 2020 -
Accepted
06 Oct 2020