Abstract
Microbially induced carbonate precipitation (MICP) has attracted worldwide attention as an environmentally friendly ground restoration technology in response to geohazards. This study describes the relationship between calcium carbonate growth within stalactite-type minerals formed around fractures in tuff breccia and microorganisms. Scanning electron microscopy revealed that calcium carbonate was precipitated in the interstices of rings formed in stalactite-type minerals, as if the carbonate minerals enhanced the strength of the silicate minerals. In addition, X-ray powder diffraction analysis detected that the calcium carbonates were calcite and vaterite. Moreover, microorganisms, such as diatoms and green algae, inhabited the interstices and, consequently, MICP by these microorganisms could play a role in the stability of outcrops. The stable isotope ratios of δ13C and δ15N and the mass spectral signals of the demineralized samples also encouraged diatoms and green algae to be involved in the formation of minerals.
Highlights
The calcium carbonate in the stalactite minerals was demineralized in 6M hydrochloric acid (HCl) for 24 h at 90 ◦ C, and the resulting solution was filtered through a 0.2 μm filter and freeze-dried to remove excess HCl [35]
The remaining solid was dissolved in water for the electrospray ionization mass spectrometry (ESI-MS) analysis
(1) Stalactite minerals are potential diatom stalactites and have ring structures where engineering techniques, such as artificial forming techniques for stalactite minerals should biomediated calcium carbonate exists in the interstices
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Calcium carbonate can be used as a repairing material by biomediated precipitation as a by-product of microbial metabolic reactions such as photosynthesis [3,9,10,11,12] and urea decomposition [3,9,13,14,15,16,17,18,19,20,21,22,23,24] In these biomediated environments, the cell wall and extracellular polymeric substances of the microorganism act as centers for carbonate precipitation [1,3,25].
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