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      S, Zn, Cr, Cu and Fe changes during fluvial sediments oxidation Translated title: Transformaciones del S, Zn, Cr, Cu y Fe en sedimentos fluviales durante el proceso de secado

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          Abstract

          Acidification of dredged sediments which have been disposed on land is highly dependent on redox shifts. The aim of the present work was to assess changes in sulphur, metal speciation (Zn, Fe, Cr y Cu) and acidity caused by a polluted sediment oxidation event. Sediments were dessicated under controlled conditions and sulphide compounds (acid volatile sulphides-AVS- and sulphate), pH and neutralization potential were measured through time during 36 days. Zinc, Cu, Cr and Fe speciation (BCR metal sequential extraction procedure) were measured at the beginning of the experiment and at day 22. An acid-base equilibrium method based on the BCR procedure was employed to assess the sediment acidification risk. Some of the re-suspension experiments were inoculated with an Acidithiobacillus ferrooxidans strain to assess biological catalysis on sulphide oxidation. Acid-base equilibrium results indicated the sediment sample had a significant acidification potential. Oxidation increased sulphate levels (56 to 2300 mg S kg-¹ in the desiccation experiment with a temporal evolution adjusted by a logistic model, and a 2100 to 3000 mg SO4 -² L-¹ increase for the resuspension experiments). Sulphide oxidation rates varied between 0 to 3.1.10-9 mg O2 kg-¹ s-¹ for the drying sediment. Zinc changes could be explained partially by ZnS conversion to ZnSO4 during oxidation. Iron reduction could be attributed to an increase in Fe oxides crystallinity. Acid-base equilibrium for the sample indicated it was a potentially acid-generating material. Zinc increased its bioavailability during drying and was the only metal that appeared in significant amounts in solution during re-suspension. Land-filling with dredged sediments could present increased metals bioavailability problems despite having an important and effective neutralization potential.

          Translated abstract

          La evaluación de los riesgos de acidificación por deposición de sedimentos dragados en superficie es muy dependiente de los cambios generados por potencial redox. El objetivo del presente trabajo fue el de evaluar cambios en las formas de azufre, metales (Zn, Fe, Cr y Cu) y aumento de acidez generado por la oxidación de sedimentos contaminados durante un proceso de oxidación controlado. Se midió, sobre sedimentos en proceso de desecación y durante 36 días, sulfuros, sulfuros volátiles, sulfatos, pH y potencial de neutralización. A partir del día 22 se aplicó un procedimiento de extracción sequencial de Zn, Cu, Cr y Fe para evaluar el riesgo de acidificación del sedimento, incluyendo entre los tratamientos la inoculación con una cepa de Acidithiobacillus ferrooxidans como catalizador de la oxidación de los sulfuros. La oxidación de sulfatos aumentó de 56 a 2300 mg S kg-¹ con una evolución temporal que ajustó a un modelo logístico. Hubo un aumento de 2100 a 3000 mg SO4 -² L-¹ de sulfatos en el experimento de resuspensión. La oxidación de los sulfuros osciló entre 0 y 3,1.10-9 mg O2 kg-¹ s-¹. Los cambios en el comportamiento del Zn pueden ser explicados parcialmente por la conversión de ZnS a ZnSO4 durante el proceso de oxidación. La reducción del hierro podría ser atribuida a un aumento en la cristalinidad de los óxidos de Fe. El balance ácido-base señala que la muestra es un material con capacidad generadora de acidez. El Zn aumentó su biodisponibilidad durante el proceso de secado y es el único metal que se encuentra presente en cantidad significativa durante el proceso de resuspensión. La disposición en tierra firme de sedimentos dragados puede generar aumento de biodisponibilidad de metales más allá de su impacto en el potencial efectivo de neutralización.

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          Most cited references52

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          Bioleaching: metal solubilization by microorganisms

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            Contaminants in sediments: remobilisation and demobilisation.

            In this study, the contaminated anoxic sediment of the Mulde reservoir (Saxony, Germany) was investigated. Several sediment cores were analysed for heavy metals and organic chemicals such as chlorobenzenes and DDTs. The comparison between anoxic and oxidised sediment cores showed the potential danger for heavy metal (Zn and Cd) remobilisation from sediment due to bioturbation or resuspension by flooding. Chemical sequential extraction was used to describe partitioning of heavy metals among different mineralogical components in the sediments. Results showed remobilisation of Zn and Cd from the sediments. The stable fraction (organic/sulfidic-bound) of Zn and Cd decreased from 10 to 3%, and from 35 to 5%, respectively. Simultaneously, the carbonate fraction increased from 3 to 12% for Cd and from 10 to 22% for Zn. Furthermore, the simulation of the diffusion of organic pollutants showed remobilisation of 1,4-dichlorobenzene. The results confirmed the necessity of sediment remediation in the reservoir. Capping seems to be a promising approach for a low-cost remediation.
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              Bioleaching: metal solubilization by microorganisms

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                Author and article information

                Journal
                cds
                Ciencia del suelo
                Cienc. suelo
                Asociación Argentina de la Ciencia del Suelo (Ciudad Autónoma de Buenos Aires, , Argentina )
                1850-2067
                December 2009
                : 27
                : 2
                : 199-207
                Affiliations
                [03] Ciudad de Buenos Aires orgnameUniversidad de Buenos Aires orgdiv1Facultad de Agronomía orgdiv2Cátedra de Edafología Argentina
                [01] San Martín Buenos Aires orgnameUniversidad de San Martín orgdiv1Escuela de Ciencia y Tecnología Argentina
                [02] Ciudad de Buenos Aires orgnameCONICET Argentina
                Article
                S1850-20672009000200006 S1850-2067(09)02700200006
                8f883e24-caf5-4eef-be66-9c2d3d1f2a73

                This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

                History
                : 26 December 2008
                : 30 September 2009
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 40, Pages: 9
                Product

                SciELO Argentina


                Anaerobic sediments,BCR sequential chemical extraction,Desiccation,Dredged sediments,Fluvial sediments,Heavy metals,Re-suspension,Sedimentos anaeróbicos,Extracción secuencial (BCR),Desecación,Sedimentos fluviales,Sedimentos dragados,Metales pesados,Resuspensión

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