Strontium incorporation into calcite generated by bacterial ureolysis

Abstract

Abstract-Strontium incorporation into calcite generated by bacterial ureolysis was investigated as part of an assessment of a proposed remediation approach for 90 Sr contamination in groundwater. Urea hydrolysis produces ammonium and carbonate and elevates pH, resulting in the promotion of calcium carbonate precipitation. Urea hydrolysis by the bacterium Bacillus pasteurii in a medium designed to mimic the chemistry of the Snake River Plain Aquifer in Idaho resulted in a pH rise from 7.5 to 9.1. Measured average distribution coefficients (D EX ) for Sr in the calcite produced by ureolysis (0.5) were up to an order of magnitude higher than values reported in the literature for natural and synthetic calcites (0.02-0.4). They were also higher than values for calcite produced abiotically by ammonium carbonate addition (0.3). The precipitation of calcite in these experiments was verified by X-ray diffraction. Time-of-flight secondary ion mass spectrometry (ToF SIMS) depth profiling (up to 350 nm) suggested that the Sr was not merely sorbed on the surface, but was present at depth within the particles. X-ray absorption near edge spectra showed that Sr was present in the calcite samples as a solid solution. The extent of Sr incorporation appeared to be driven primarily by the overall rate of calcite precipitation, where faster precipitation was associated with greater Sr uptake into the solid. The presence of bacterial surfaces as potential nucleation sites in the ammonium carbonate precipitation treatment did not enhance overall precipitation or the Sr distribution coefficient. Because bacterial ureolysis can generate high rates of calcite precipitation, the application of this approach is promising for remediation of 90 Sr contamination in environments where calcite is stable over the long term.

Modeling the evolution of complex conductivity during calcite precipitation on glass beads

“…Calcite precipitation modifies the rock porosity, and can have either benefits or side effects for the mechanical and transport properties of porous media. Calcite precipitation in porous media has broad applications in geotechnical engineering for soil strengthening (DeJong et al 2006(DeJong et al , 2010Whiffin et al 2007) and in environmental studies for the sequestration of heavy metals (Sturchio et al 1997;Cheng et al 1999), radionuclides (Fujita et al 2004;Mitchell & Ferris 2005), and CO 2 in geological formations Xu et al 2003). However, calcite precipitation can also have undesirable effects such as the decrease of the permeability of reactive barriers for the remediation of aquifers (Wilkin et al 2003;Scheibe et al 2006;Jeen et al 2007).…”

Carbonate Mineral Precipitation for Soil Improvement Through Microbial Denitrification

“…The complex interactions between microorganisms and minerals have been well-documented through the efforts of researchers attempting to understand the formation, dissolution, and alteration of minerals by microorganisms on geologic and engineering timescales (Ehrlich 2002;Drever 2008;Karatas 2008;Phoenix and Konhauser 2008;Shock 2009 Incorporation of divalent ions into the calcite structure appears to slow their transport and possibly immobilize them within the calcite structure (Mitchell and Ferris 2005;Colwell et al 2003;Fujita et al 2004;Fujita et al 2000;Smith et al 2004). If proven effective, immobilization of these contaminants through MICP may provide a sustainable and cost-effective in-situ remediation scheme for radionuclide and metal contaminated sites.…”

“…One such novel approach is microbial carbonate precipitation of radionuclides and metal contaminants through in-situ remediation of contaminated aquifers (Mitchell and Ferris 2005;Colwell et al 2003;Fujita et al 2000;Smith et al 2004 (Mitchell and Ferris 2005;Colwell et al 2003;Fujita et al 2004;Fujita et al 2000;Smith et al 2004). If proven effective, immobilization of these contaminants through MICP may provide a sustainable and cost-effective in-situ remediation scheme for radionuclide and metal contaminated sites.…”

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides – 1. Microbial Processes and Mechanisms Affecting Bioremediation of Metal Contamination and Influencing Metal Toxicity and Transport

“…The formation of calcium carbonates particles in microbial mats and other aggregates was suggested to be, at least in part, because of heterotrophic bacteria (Hammes & Verstraete 2002). Recently, interest in bacterially associated calcium carbonate precipitation has grown due to strategic bioremediation approaches involving solid phase capture of radionuclide and trace element contaminants by carbonates in groundwater systems (Curti 1999;Fujita et al 2004). Fe(III) oxides are commonly thought of as the most important sorbents responsible for sequestration of many metals and radionuclides in soils and groundwater systems (Warren & Haack 2001).…”

“…Associated solid phase capture of Sr was highly effective, capturing 95% of the 1 mM Sr added within 24 h . Because bacterial ureolysis can generate high rates of calcite precipitation, the application of this approach is promising for remediation of Sr contamination in environments where calcite is stable over the long term (Fujita et al 2004). …”