Effect of Mn oxyhydroxides application on barite reduction (BaSO4) and availability of Ba in anoxic soils

• Grant number: 19/22280-1
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: October 01, 2021
• End date: September 30, 2022
• Field of knowledge: Agronomical Sciences - Agronomy - Soil Science
• Principal Investigator: Jussara Borges Regitano
• Grantee: Douglas Gomes Viana
• Supervisor: Owen Duckworth
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Institution abroad: North Carolina State University (NC State), United States
• Associated to the scholarship: 19/02796-3 - Effects of organic matter and microbial community structure on the availability and phytoremediation of BA (barite) in flooded soils, BP.DR

Abstract

Barium (Ba) has been widely used in oil drilling fluids in the barite form (BaSO4) due to its high density, low solubility and low toxicity. However, in anoxic soils, strictly anaerobic microorganisms use sulfate as the final electron acceptor reducing it to sulfide and making Ba available to the environment, posing a risk to human beings and plants. Manganese oxides are stronger oxidizing agents than sulfate, as they are reduced before sulfate (MnO2 > Fe (OH)3 > SO42-). Therefore, the addition of MnO2 may inhibit or affect sulfate reduction. In the view of above, we hypothesize that application of Mn oxyhydroxides (birnessite and hausmannite) with distinct reactivity will inhibit sulfate reduction and consequently decrease the availability of Ba in anoxic soils contaminated with barite. The extent of such effect will depend on the concentration and speciation of the elements in the environment. For this purpose, conventional and synchrotron radiation techniques will be used to i) select the concentration and reactivity of Mn oxyhydroxides with higher inhibition of sulfate reduction and lower availability of Ba; ii) verify the influence of Mn oxyhydroxides reactivity on sulfate reduction and barium availability for soil solution; iii) quantify the rates of both Ba mobilization and sulfate reduction in a barite contaminated soil after addition of Mn oxyhydroxides; iv) assess the chemical speciation of Ba in the solid phase and soil solution by X-ray absorption spectroscopy (XAS). (AU)