Influência de hidrocarbonetos do petróleo na mobilidade de arsênio em solos tropicais
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Data
2020-05-13
Autores
Luko, Karen Silva [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O objetivo deste trabalho foi investigar a influência da contaminação por gasolina e diesel na mobilidade das espécies inorgânicas de arsênio no solo. Para tanto, amostras de solo (n = 25) foram coletadas em uma área de mineração, uma área de cobertura vegetal e uma área agrícola, e foram contaminadas em laboratório. Foram coletados os extratos de saturação para as amostras dos três tratamentos (controle, gasolina e diesel) e os resultados de arsênio no extrato de saturação obtidos foram comparados através de testes estatísticos não paramétricos e análise multivariada de dados. Foi realizada análise de especiação redox para todas as amostras e o fracionamento químico do arsênio no extrato de saturação do solo para amostras selecionadas através da técnica Difusão em Filmes Finos por Gradiente de Concentração. As concentrações de arsênio também foram comparadas quanto a parâmetros físicos, químicos e quanto à presença de sete genes funcionais relativos ao metabolismo de arsênio (resistência, oxidação, respiração e metilação) em micro- organismos. A adição de gasolina e de diesel resultou no aumento das concentrações de arsênio extraível em água nos solos. O aumento da mobilidade do arsênio em solo na presença dos contaminantes, apesar de significativo, foi menos expressivo quando comparado a outros sistemas (e.g. aquífero e áreas úmidas) e outras fontes de matéria orgânica (e.g. biocarvão e serapilheira) reportados na literatura. As concentrações de As(III) foram menores em solos urbanos, quando comparadas às obtidas para solos rurais e com cobertura vegetal, possivelmente devida a uma menor atividade microbiológica nos solos urbanos. A respiração basal do solo foi a principal variável de influência na mobilidade de As(III). Uma taxa de biodegradação estimada em aproximadamente 7% foi o suficiente para extrair frações de As(III), antes imobilizadas pela fase sólida, para 60% dos solos estudados. A metilação, importante fator de regulação da concentração de As(III) nos solos não contaminados, não foi significante quando gasolina ou diesel foram adicionados ao sistema. A relação entre o teor de Mn no solo e As solúvel pode indicar a ocorrência de um mecanismo de reoxidação abiótica de As(III). A adição de gasolina ou diesel aos solos aumentou a fração de arsênio extraível em água em até 20 vezes, porém a adição destes contaminantes não influenciou a fração lábil de arsênio, sendo esta relacionada ao carbono orgânico dissolvido do solo natural do solo.
The aim of this work was to investigate the influence of gasoline and diesel contamination on the mobility of inorganic arsenic species in soil samples. Soil samples (n = 25) were collected in a mining area, in an area characterized by natural vegetation cover and in an agricultural area. The soil samples were contaminated in laboratory with gasoline and diesel. Saturation extracts were collected from soil subsamples of the three treatments (control, gasoline and diesel) and the results of arsenic concentration in the extracts were analyzed by non-parametric statistical tests and multivariate data analysis. Redox speciation analysis for all samples and chemical fractionation of arsenic were performed in some of the water extracts samples by Diffusive Gradients in Thin Films technique. Arsenic concentrations were compared to physical and chemical parameters as well as to the presence of seven functional genes related to arsenic microbial metabolism (resistance, oxidation, respiration and methylation). The addition of gasoline and diesel to surface soils resulted in an increase in the water extractable arsenic in surface soils. The increased mobility of arsenic in the presence of contaminants, although significant, was less expressive than what has been reported for other systems (e.g. aquifers and wetlands) and other sources of organic materials (e.g. litter and biochar). As(III) concentrations were lower in urban soils when compared to agricultural and vegetation cover soils, possibly due to a less expressive microbiologic activity in urban soils. Basal soil respiration was the main variable influencing As(III) mobility. An estimated biodegradation rate of approximately 7% was sufficient to make As(III) fractions, previously immobilized by solid phase, present in the solution for 60% of the studied soils. Methylation, an important factor in controlling the As(III) concentration in uncontaminated soils, was not significant when gasoline or diesel were introduced in the system. As(III) in the solution was negatively related to the content of Mn in the soil which may indicate an occurrence of an important mechanism of abiotic reoxidation of As (III). The addition of gasoline or diesel to the soils increased the fraction of arsenic extractable in water up to 20-fold. However, the addition of these contaminants did not influence the labile fraction of arsenic, which was strongly influenced by the soil dissolved organic carbon, naturally occurring in soils.
The aim of this work was to investigate the influence of gasoline and diesel contamination on the mobility of inorganic arsenic species in soil samples. Soil samples (n = 25) were collected in a mining area, in an area characterized by natural vegetation cover and in an agricultural area. The soil samples were contaminated in laboratory with gasoline and diesel. Saturation extracts were collected from soil subsamples of the three treatments (control, gasoline and diesel) and the results of arsenic concentration in the extracts were analyzed by non-parametric statistical tests and multivariate data analysis. Redox speciation analysis for all samples and chemical fractionation of arsenic were performed in some of the water extracts samples by Diffusive Gradients in Thin Films technique. Arsenic concentrations were compared to physical and chemical parameters as well as to the presence of seven functional genes related to arsenic microbial metabolism (resistance, oxidation, respiration and methylation). The addition of gasoline and diesel to surface soils resulted in an increase in the water extractable arsenic in surface soils. The increased mobility of arsenic in the presence of contaminants, although significant, was less expressive than what has been reported for other systems (e.g. aquifers and wetlands) and other sources of organic materials (e.g. litter and biochar). As(III) concentrations were lower in urban soils when compared to agricultural and vegetation cover soils, possibly due to a less expressive microbiologic activity in urban soils. Basal soil respiration was the main variable influencing As(III) mobility. An estimated biodegradation rate of approximately 7% was sufficient to make As(III) fractions, previously immobilized by solid phase, present in the solution for 60% of the studied soils. Methylation, an important factor in controlling the As(III) concentration in uncontaminated soils, was not significant when gasoline or diesel were introduced in the system. As(III) in the solution was negatively related to the content of Mn in the soil which may indicate an occurrence of an important mechanism of abiotic reoxidation of As (III). The addition of gasoline or diesel to the soils increased the fraction of arsenic extractable in water up to 20-fold. However, the addition of these contaminants did not influence the labile fraction of arsenic, which was strongly influenced by the soil dissolved organic carbon, naturally occurring in soils.
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Palavras-chave
Labilidade, Análise de especiação, Contaminantes orgânicos, Gasolina, Diesel, DGT, Lability, Speciation analysis, Organic contaminants, Gasoline, Diffusive gradients in thin films