Assessment of lability and bioavailability of metals in a uranium mining restoration site using DGT and phytoscreening techniques
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2021-02-23
Autores
Gemeiner, Hendryk [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A técnica difusão em filmes finos por gradientes de concentração (DGT) mostrou ser uma ferramenta promissora em vários estudos para avaliar a labilidade e biodisponibilidade de metais no solo. No presente trabalho, foram coletadas amostras pareadas do solo e núcleo de árvores de uma área de referência e três áreas impactadas pela mineração no complexo de mineração de urânio de Poços de Caldas no sul de Minas Gerais (Brasil). As amostras de solo foram analisadas quanto ao teor total de Al, Co, Cu, Fe, Mn, Ni, Pb, Zn e U por XRF e, posteriormente, a labilidade e potencialmente a biodisponibilidade ambiental desses metais foi investigada pela técnica DGT e análise da água intersticial usando ICP-MS. Além disso, os resultados foram comparados com a concentração de metais obtida pela técnica de Tree Coring da vegetação florestal, a fim de avaliar a transferência solo-planta desses metais. Em todas as áreas de amostragem, as concentrações totais médias dos elementos U (Ctot.= 100.5 ± 66.5 mg kg-1 até 129.6 ± 57.1 mg kg-1), Pb (Ctot.= 30.8 ± 12.7 mg kg-1 até 90.8 ± 90.8 mg kg-1), Zn (Ctot.= 91.5 ± 24.7 mg kg-1 até 99.6 ± 10.3 mg kg-1), Cu (Ctot.= 26.3 ± 4.8 mg kg-1 até 27.9 ± 4.0 mg kg-1), Ni (Ctot.= 49.1 ± 8.7 mg kg-1 até 73.7 ± 17.4 mg kg-1), Co (Ctot.= 73.8 ± 25.5 mg kg-1 até 119.7 ± 26.4 mg kg-1) e Mn (Ctot.= 554.0 ± 163.6 mg kg-1 até 1080.4 ± 697.9 mg kg-1) nos solos foram explicitamente superiores aos valores de referência de qualidade para solos do estado de Minas Gerais. Os resultados do estudo sugerem que a influência dos efluentes da drenagem ácida causou o aumento das concentrações lábeis de Zn nos solos afetados pela drengaem ácida. Frações altamente lábeis dos elementos Pb (R= 62 ± 34 % to 81 ± 29 %), U (R= 57 ± 20 % to 77 ± 28 %) e Zn (R= 21 ± 25 % to 34 ± 31 %) juntamente com altos fatores de bioconcentração encontrados em as amostras de madeira dos elementos Pb (BCF= 0.04 ± 0.03 % to 0.26 ± 0.33 %) e Zn (BCF= 1.2 ± 1.3 % to 2.5 ± 2.1 %) indicam um alto potencial tóxico desses elementos no solo para a biota em todas as áreas de amostragem do local de estudo. A combinação de análise de água intersticial e DGT com Tree Coring mostrou ser uma abordagem útil para especificar o risco de solos poluídos por metais. No entanto, a comparação dos resultados de DGT e Tree Coring não podia prever a absorção de metais nos xilemas dos indivíduos dos árvores amostrados e, portanto, é limitado para avaliar a biodisponibilidade ambiental e biodisponibilidade toxicológica.
The technique of diffusive gradients in thin films (DGT) has been shown to be a promising tool to assess lability and bioavailability of metals in soils in a variety of studies. In the present work, paired topsoil and tree core samples from a reference area and three mining impacted areas at the Uranium mining complex of Poços de Caldas in Southern Minas Gerais (Brazil) were collected. Soil samples were analysed for their total content of Al, Co, Cu, Fe, Mn, Ni, Pb, Zn and U by XRF and subsequently, the lability and potential environmental bioavailability of these metals were investigated by DGT and pore water analysis using ICP-MS. In addition, results were compared with metal concentrations obtained by Tree Coring from the forest vegetation to potentially evaluate the soil-plant-transfer of these metals. In all sampling areas, mean total concentrations of the elements U (Ctot.= 100.5 ± 66.5 mg kg-1 to 129.6 ± 57.1 mg kg-1), Pb (Ctot.= 30.8 ± 12.7 mg kg-1 to 90.8 ± 90.8 mg kg-1), Zn (Ctot.= 91.5 ± 24.7 mg kg-1 to 99.6 ± 10.3 mg kg-1), Cu (Ctot.= 26.3 ± 4.8 mg kg-1 to 27.9 ± 4.0 mg kg-1), Ni (Ctot.= 49.1 ± 8.7 mg kg-1 to 73.7 ± 17.4 mg kg-1), Co (Ctot.= 73.8 ± 25.5 mg kg-1 to 119.7 ± 26.4 mg kg-1) and Mn (Ctot.= 554.0 ± 163.6 mg kg-1 to 1080.4 ± 697.9 mg kg-1) in soils were explicitly higher than quality reference values for soils from Minas Gerais. Study results suggest that influence of AMD effluents caused the increase of relative labile concentrations of Zn in AMD affected soils. High labile fractions of the elements Pb (R= 62 ± 34 % to 81 ± 29 %), U (R= 57 ± 20 % to 77 ± 28 %) and Zn (R= 21 ± 25 % to 34 ± 31 %) in soils together with high bioconcentration factors found in wood samples for Pb (BCF= 0.04 ± 0.03 % to 0.26 ± 0.33 %) and Zn (BCF= 1.2 ± 1.3 % to 2.5 ± 2.1 %) indicate a high toxic potential of these elements to living organisms in the soils of the study site. The combination of pore water and DGT analysis with Tree Coring showed to be a useful approach to specify the risk of metal polluted soils. However, the comparison of the results from DGT and Tree Coring could not predict the uptake of metals into the xylems of the sampled tree individuals and are thus limited to assess environmental and toxicological bioavailability.
The technique of diffusive gradients in thin films (DGT) has been shown to be a promising tool to assess lability and bioavailability of metals in soils in a variety of studies. In the present work, paired topsoil and tree core samples from a reference area and three mining impacted areas at the Uranium mining complex of Poços de Caldas in Southern Minas Gerais (Brazil) were collected. Soil samples were analysed for their total content of Al, Co, Cu, Fe, Mn, Ni, Pb, Zn and U by XRF and subsequently, the lability and potential environmental bioavailability of these metals were investigated by DGT and pore water analysis using ICP-MS. In addition, results were compared with metal concentrations obtained by Tree Coring from the forest vegetation to potentially evaluate the soil-plant-transfer of these metals. In all sampling areas, mean total concentrations of the elements U (Ctot.= 100.5 ± 66.5 mg kg-1 to 129.6 ± 57.1 mg kg-1), Pb (Ctot.= 30.8 ± 12.7 mg kg-1 to 90.8 ± 90.8 mg kg-1), Zn (Ctot.= 91.5 ± 24.7 mg kg-1 to 99.6 ± 10.3 mg kg-1), Cu (Ctot.= 26.3 ± 4.8 mg kg-1 to 27.9 ± 4.0 mg kg-1), Ni (Ctot.= 49.1 ± 8.7 mg kg-1 to 73.7 ± 17.4 mg kg-1), Co (Ctot.= 73.8 ± 25.5 mg kg-1 to 119.7 ± 26.4 mg kg-1) and Mn (Ctot.= 554.0 ± 163.6 mg kg-1 to 1080.4 ± 697.9 mg kg-1) in soils were explicitly higher than quality reference values for soils from Minas Gerais. Study results suggest that influence of AMD effluents caused the increase of relative labile concentrations of Zn in AMD affected soils. High labile fractions of the elements Pb (R= 62 ± 34 % to 81 ± 29 %), U (R= 57 ± 20 % to 77 ± 28 %) and Zn (R= 21 ± 25 % to 34 ± 31 %) in soils together with high bioconcentration factors found in wood samples for Pb (BCF= 0.04 ± 0.03 % to 0.26 ± 0.33 %) and Zn (BCF= 1.2 ± 1.3 % to 2.5 ± 2.1 %) indicate a high toxic potential of these elements to living organisms in the soils of the study site. The combination of pore water and DGT analysis with Tree Coring showed to be a useful approach to specify the risk of metal polluted soils. However, the comparison of the results from DGT and Tree Coring could not predict the uptake of metals into the xylems of the sampled tree individuals and are thus limited to assess environmental and toxicological bioavailability.
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Palavras-chave
DGT, Soil contamination, Phytoscreening, Metal lability, Bioavailability, Uranium mining, Contaminação de solo, Metais labeis, Biodisponibilidade, Mineração de urânio