Resumen
The mixing precipitation of CaCO3 in natural waters was theoretically studied by the methods of chemical equilibrium calculation. Results show that mixing precipitation of CaCO3 can be produced by mixing between two unsaturated water samples with respect to CaCO3, two oversaturated water samples, an unsaturated water sample and an oversaturated water sample. Mixing precipitation can be classified into two major different types: mixing precipitation in a strict sense and mixing precipitation in a broad sense. Mixing precipitation in a strict sense refers to the mixing effect that makes the state of CaCO3 change from dissolution into precipitation, or the increases in the precipitability of CaCO3 in mixed water. Mixing precipitation in a broad sense refers to the mixing effect that reduces the solubility of CaCO3 in mixed water. Mixing precipitation is controlled by simultaneous chemical equilibria. Generally, if the HCO3- concentration is higher in one solution and the Ca2+ concentration is higher in the other, mixing precipitation of CaCO3 will occur when they are combined.