Calcium Carbonate Formations in Edaphic Components of Ecosystems

Abstract

Calcium carbonate is an important component of the edaphic components of ecosystems (soils, river and lake sediments, suspensions). Calcite, aragonite, and vaterite are the three its polymorphs, in order of decreasing thermodynamic stability. Aragonite and vaterite, as less thermodynamically stable and more soluble polymorphs than calcite, are found in natural setting much rare (except for their biogenic formations) and are much less studied. Although they are important precursors in many carbonate-forming systems. We found examples of vaterite microforms in the river ice suspensions, river and lake bottom sediments of the different natural zones – the Amur and the Simmi Rivers (the Amur River basin, Khabarovsk Region, Russia), the Jordan River (Jordan). Vaterite was originally thought to have a very short lifespan; however it may have greater longevity. In the presence of low molecular amino acids ex and in situ vaterite is stabilized as toroidal suprastructures. These microforms of CaCO3 are characterized with internal diameter of 8–10 m and cross-sectional radius of about 1 m. The age of peat stratum, in which the toroidal vaterite microforms were found, is more than 6000 years. Another polymorphic modification of CaCO3, aragonite, is stabilized in the bottom sediments of drainless lakes of the arid zone with extremely high salinity, e.g. the famous ooids of the Grand Salt Lake (USA). However, outside the "habitat" – the salt water of the lake – aragonite ooids are destroyed.