Bacterially-induced dissolution of calcite: the role of bacteria in limestone weathering

Abstract

The interaction between microorganisms and the calcite mineral surface in aqueous solutions, under earth surface conditions, was the focus of this study. More specifically, we investigated if bacterial attachment and metabolism increase the dissolution rates of calcite crystals and alter their surfaces in solution. A natural microbial consortium, rather than model organisms, was used in the experiments. Weathered samples from the Trenton carbonates were collected on the flanks of Mount Royal in Montréal (Québec, Canada). The associated bacteria were identified using molecular biology DNA fingerprinting techniques. This information was used to determine the nutrient requirements of suitable growth media. Samples contained typical soil dwelling organisms from the phylum Actinobacteria, gram-positive heterotrophs. Bacteria were combined with cleaved Iceland Spar calcite rhombohedra in a low-ionic strength (10−2 M) NaCl solution at ambient pCO2 , 25°C and 1 atm pressure. The effect of solution chemistry (e.g. the presence of phosphate) on the calcite dissolution kinetics was also investigated. The dissolution rates in the presence of bacteria, did not vary significantly from abiotic conditions, but decreased notably in the presence of phosphate.