Carbonate precipitation of divalent cations in lakes: interest, current knowledge of the mechanisms and suggestions (a critical review of the literature)
Carbonates that precipitate in the water column of the lakes are documented: these include siderite, rhodochrosite, calcite, magnesite, and dolomite. As climate indicators and indicators of changes in chemical characteristics of lakes, they are increasingly monitored in sediments. Often incomplete, the mechanisms of their precipitation in the water column of the lake and in pore waters are reviewed in this study. According to the literature, siderite and rhodochrosite precipitate in reducing environments saturated with iron carbonate and manganese carbonate respectively. These predictions are confirmed in this study, the redox potential being a key parameter for the precipitation of iron carbonate. However, the literature does not sufficiently describe the origin (geochemical or biological) of lacustrine solid carbonate components or the phenomena that stabilize or make them vulnerable (dissolution). This study provides further details on the endogenesis of these carbonates by taking account of the origin of their components. This study also shows that the character of the water (aggressive or encrusting) could have a significant impact on the fate of these carbonates. Thus, degassing a lake might make water encrusting; this encrusting character of water is ideal for the precipitation of carbonates, but detrimental to the stability of layers whose composition changes after precipitation of chemical species. Therefore any lake degassing project should consider this parameter (aggressive or encrusting nature of the water) in its design, implementation and operation.