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As lamas de depuração são um subproduto do tratamento de águas residuais que é produzido mundialmente. Como a sua composição em termos de matéria orgânica e nutrientes é muito interessante, estas podem ser reaproveitadas e aplicadas por exemplo para a valorização de solos agrícolas. Esta aplicação é uma prática comum, especialmente na Europa. Contudo, as lamas são vistas como uma fonte potencial de contaminação do solo. O objetivo deste trabalho foi o desenvolvimento de um método de extração QuEChERS para análise de 21 contaminantes orgânicos (pesticidas organoclorados (OCP), PCB, éteres difenílicos polibromados (PBDE) e pesticidas piretróides (PIR)) em lamas por cromatografia gasosa por captura de eletrões (GCECD), e de PAH em cromatografia líquida com detetores de conjunto de fotodiodos e fluorescência (LC-PDA-FLD).
O objetivo deste trabalho foi o desenvolvimento de um método de extração QuEChERS para análise de 21 contaminantes orgânicos (pesticidas organoclorados (OCP), PCB, éteres difenílicos polibromados (PBDE) e pesticidas piretróides (PIR)) em lamas por cromatografia gasosa por captura de eletrões (GCECD), e de PAH em cromatografia líquida com detetores de conjunto de fotodiodos e fluorescência (LC-PDA-FLD). O método foi desenvolvido para duas amostras de lamas de ETAR distintas (A e B), com possível destino para uso agrícola. As amostras de lamas foram também caracterizadas físicoquimicamente de acordo com o DL 276/2009, de 2 de outubro, para lamas destinadas ao uso agrícola. Foram analisados os parâmetros de pH, matéria seca (DM), matéria orgânica (OM), azoto Kjeldahl (N Kj), fósforo total (P total), Ca, Na, K, Mg e os metais pesados Zn, Cu, Cr e Ni. Os nutrientes e metais pesados foram quantificados através de espectroscopia de absorção atómica após digestão ácida das amostras, exceto para o N Kj e P total, cuja quantificação foi realizada através de espectrometria visível.
O método desenvolvido para análise de poluentes orgânicos persistentes (POP) e piretróides em GCECD resume-se numa extração com acetonitrilo (ACN) e sais de QuEChERS, seguida de uma etapa de limpeza por extração em fase sólida dispersiva (dSPE), em que foram usados amina primária secundária (PSA), C18, MgSO4, carbono grafitizado (GCB) e Z-Sep. Na amostra A quantificou-se α-endossulfão (110 ± 7 µg/kg), PCB 118 (263 ± 49 µg/kg), BDE 28 (148 ± 31 µg/kg), cipermetrina (89 ± 12 µg/kg), deltametrina (275 ± 60 µg/kg), e BDE 183 (36 ± 2 µg/kg). Na amostra A também se encontrou p,p´-DDE <LOD e na amostra B p,p´-DDE e dieldrina entre LOD-LOD. Concluiu-se que a otimização da metodologia, nomeadamente na etapa de limpeza dSPE da matriz, é determinante para esta matriz complexa e heterogénea. O método de análise PAH por LC-PDA-FLD após extração QuEChERS permitiu analisar simultaneamente 13 PAH, tendo encontrado sucesso em quantificar 6 na amostra A e 7 na amostra B, entre 12 identificados. A concentração total de PAH nas amostras foi de 1,086 µg/g na amostra A, e de 0,851 µg/g na amostra B.
Relativamente aos valores limite de concentração de compostos orgânicos nas lamas destinadas à agricultura, o DL 276/2009, de 2 de outubro, prevê limites de PCB de 800 µg/kg e de PAH de 6 µg/g. O PCB 118 quantificado na amostra A e os ∑PAH quantificados nas amostras A e B encontram-se abaixo desses valores limites. Quantos aos metais pesados, o Zn, Cu, Cr e Ni encontram-se também abaixo dos valores limite legislados (Zn:2500 mg/kg, Cu:1000 mg/kg, Cr: 1000 mg/kg e Ni:300 mg/kg). Para ambas as amostras, os valores obtidos foram: Amostra A - Zn: 814 mg/kg, Cu: 270 mg/kg, Cr: 217 mg/kg e Ni: 50 mg/kg; Amostra B - Zn: 436 mg/kg, Cu: 320 mg/kg, Cr: 29 mg/kg e Ni: 13 mg/kg.
Os métodos de análise desenvolvidos e otimizados provaram-se relativamente eficientes na análise de múltiplos contaminantes orgânicos, tendo em conta a complexidade da matriz. É, então, possível aplica-los para monitorização de contaminantes orgânicos em lamas de ETAR, com possível destino a aplicação agrícola. Alguns dos poluentes identificados, como os OCP, PBDE e PIR, não são contemplados no DL, enquanto os PCB, PAH e metais pesados, mesmo estando abaixo dos limites, representam riscos de exposição crónica a que os solos agrícolas estão sujeitos. Deste modo, conclui-se que é determinante o contínuo desenvolvimento e atualização de metodologias analíticas para identificação e quantificação de poluentes orgânicos em lamas para fins agrícolas e a importância de atualizar a legislação de forma a incluir outros contaminantes orgânicos.
Sewage sludge is a by-product of wastewater treatment that is produced worldwide. As its composition in terms of organic matter and nutrients is very interesting, it can be reused and applied, for example, in agricultural soils. This application is common practice, especially in Europe. However, sludge is seen as a potential source of soil contamination by metals, pharmaceuticals, PAH, PCB, pesticides, microplastics, among others. The aim of this work was the development of a QuEChERS extraction method for the analysis of 21 organic contaminants (OCPs, PCBs, PBDEs and PIRs) in sludge through GC-ECD, and of PAH through LC-PDA-FLD. The method was developed for two different WWTP sludge samples (A and B), with possible destination for agricultural use. The sludge samples were also physicochemically characterized according to the DL 276/2009, October 2nd, for sludge intended for agricultural use. The parameters pH, DM, OM, Kjeldahl N, total P, Ca, Na, K, Mg and the heavy metals Zn, Cu, Cr and Ni were analyzed. The nutrients and heavy metals were quantified through atomic absorption spectroscopy after acid digestion of the samples, except for Kjeldahl N and total P, whose quantification was performed by visible spectrometry. The method developed for analysis of POPs and PIRs in GC-ECD consists of an extraction with CAN and QuEChERS salts, followed by a dSPE cleanup step, in which PSA, C18, MgSO4, GCB and Z-Sep were emplyed. In sample A, α-endosulfan (110 ± 7 µg/kg), PCB 118 (263 ± 49 µg/kg), BDE 28 (148 ±31 µg/kg), cypermethrin (89 ± 12 µg/kg), deltamethrin (275 ± 60 µg/kg), and BDE 183 (36 ± 2 µg/kg) were quantified. In sample A, p,p'-DDE <LOD was also found, and in sample B, p,p'-DDE and dieldrin were detected (LOD-LOQ). It was concluded that the optimization of the methodology, namely the dSPE cleanup step, is determinant for this complex and heterogeneous matrix. The PAH analysis method by LC-PDA-FLD after QuEChERS extraction allowed simultaneous analysis of 13 PAHs, having found success in quantifying 6 in sample A and 7 in sample B, among 12 identified. The total concentration of PAHs in the samples was 1,086 µg/g in sample A, and 0,851 µg/g in sample B. Regarding the limit values for the concentration of organic compounds in sludge intended for agriculture use, the DL 276/2009 of October 2nd sets limits for PCBs of 800 µg/kg and PAH of 6 µg/g. The PCB 118 quantified in sample A and the ∑PAH quantified in samples A and B are below these limit values. As for the heavy metals, Zn, Cu, Cr and Ni are also below the legislated limit values (Zn:2500 mg/kg, Cu:1000 mg/kg, Cr: 1000 mg/kg and Ni:300 mg/kg). For both samples, the values obtained were: Sample A - Zn: 814 mg/kg, Cu: 270 mg/kg, Cr: 217 mg/kg and Ni: 50 mg/kg; Sample B - Zn: 436 mg/kg, Cu: 320 mg/kg, Cr: 29 mg/kg and Ni: 13 mg/kg. The developed and optimized analysis methods have proven to be relatively efficient in the analysis of multiple organic contaminants, considering the complexity of the matrix. It is then possible to apply them for monitoring organic contaminants in WWTP sludge, with possible destination for agricultural application. Some of the pollutants identified, such as OCPs, PBDEs and PIRs, are not contemplated in the DL, while PCBs, PAHs, and heavy metals, even if below the limits, represent risks of chronic exposure to which agricultural soils are subjected. In this way, we conclude that the continuous development and updating of methodologies for their identification and quantification and to reinforce the importance of updating the legislation in order to include other organic contaminants are determinant.
Sewage sludge is a by-product of wastewater treatment that is produced worldwide. As its composition in terms of organic matter and nutrients is very interesting, it can be reused and applied, for example, in agricultural soils. This application is common practice, especially in Europe. However, sludge is seen as a potential source of soil contamination by metals, pharmaceuticals, PAH, PCB, pesticides, microplastics, among others. The aim of this work was the development of a QuEChERS extraction method for the analysis of 21 organic contaminants (OCPs, PCBs, PBDEs and PIRs) in sludge through GC-ECD, and of PAH through LC-PDA-FLD. The method was developed for two different WWTP sludge samples (A and B), with possible destination for agricultural use. The sludge samples were also physicochemically characterized according to the DL 276/2009, October 2nd, for sludge intended for agricultural use. The parameters pH, DM, OM, Kjeldahl N, total P, Ca, Na, K, Mg and the heavy metals Zn, Cu, Cr and Ni were analyzed. The nutrients and heavy metals were quantified through atomic absorption spectroscopy after acid digestion of the samples, except for Kjeldahl N and total P, whose quantification was performed by visible spectrometry. The method developed for analysis of POPs and PIRs in GC-ECD consists of an extraction with CAN and QuEChERS salts, followed by a dSPE cleanup step, in which PSA, C18, MgSO4, GCB and Z-Sep were emplyed. In sample A, α-endosulfan (110 ± 7 µg/kg), PCB 118 (263 ± 49 µg/kg), BDE 28 (148 ±31 µg/kg), cypermethrin (89 ± 12 µg/kg), deltamethrin (275 ± 60 µg/kg), and BDE 183 (36 ± 2 µg/kg) were quantified. In sample A, p,p'-DDE <LOD was also found, and in sample B, p,p'-DDE and dieldrin were detected (LOD-LOQ). It was concluded that the optimization of the methodology, namely the dSPE cleanup step, is determinant for this complex and heterogeneous matrix. The PAH analysis method by LC-PDA-FLD after QuEChERS extraction allowed simultaneous analysis of 13 PAHs, having found success in quantifying 6 in sample A and 7 in sample B, among 12 identified. The total concentration of PAHs in the samples was 1,086 µg/g in sample A, and 0,851 µg/g in sample B. Regarding the limit values for the concentration of organic compounds in sludge intended for agriculture use, the DL 276/2009 of October 2nd sets limits for PCBs of 800 µg/kg and PAH of 6 µg/g. The PCB 118 quantified in sample A and the ∑PAH quantified in samples A and B are below these limit values. As for the heavy metals, Zn, Cu, Cr and Ni are also below the legislated limit values (Zn:2500 mg/kg, Cu:1000 mg/kg, Cr: 1000 mg/kg and Ni:300 mg/kg). For both samples, the values obtained were: Sample A - Zn: 814 mg/kg, Cu: 270 mg/kg, Cr: 217 mg/kg and Ni: 50 mg/kg; Sample B - Zn: 436 mg/kg, Cu: 320 mg/kg, Cr: 29 mg/kg and Ni: 13 mg/kg. The developed and optimized analysis methods have proven to be relatively efficient in the analysis of multiple organic contaminants, considering the complexity of the matrix. It is then possible to apply them for monitoring organic contaminants in WWTP sludge, with possible destination for agricultural application. Some of the pollutants identified, such as OCPs, PBDEs and PIRs, are not contemplated in the DL, while PCBs, PAHs, and heavy metals, even if below the limits, represent risks of chronic exposure to which agricultural soils are subjected. In this way, we conclude that the continuous development and updating of methodologies for their identification and quantification and to reinforce the importance of updating the legislation in order to include other organic contaminants are determinant.
Description
Keywords
POP Piretróides PAH QuEChERS Cromatografia Pyrethroids Chromatography