Effect of ionic strength on the dissolution and precipitation of carbonate minerals and the nature of ionic species from some calcareous soil

A laboratory study was conducted to demonstrate the effect of ionic strength on the dissolution and precipitation of carbonate minerals and ionic species using well water with ionic strengths of (0.013, 0.065, 0.130) mol l-1 by the method of wetting and drying of natural, unexcited soil columns taken from five different sites in their content of calcium carbonate within Nineveh Governorate / northern Iraq, classified within the Calciothirds soil group, and for five wetting and drying cycles, the duration of one cycle being ten days. After the fifth cycle of wetting and drying, water is added in the amount of two pore sizes to obtain a displacement solution of one pore size, which is collected in plastic bottles to conduct analysis of the main dissolved ions and entered into the VisualMinteq A2 geochemical equilibrium program to obtain saturation index values for carbonate minerals. The outputs of the program showed the superiority of well water with an ionic strength of (0.130) mol l-1 in the quantity and number of precipitated carbonate minerals represented by minerals (Calcite, Argonit, Vitrite, Regular Dolomite, Irregular Dolomite, Honet and Magnesite). The results of the theoretical correlation showed that the dominant ionic species were arranged as follows: CaSO4.2H2O >MgCl2>CaCl2> Ca(HCO3)2 > MgSO4> Mg(HCO3)2. The results show an increase in the percentages of all ionic species for all sites with an increase in the ionic strength of the water. Keywords: Ionic strength, dissolution, precipitation, carbon minerals, ionic species, saturation index, Ionic composition.