Phosphorus and calcium carbonate solubilities in Lake Kinneret

Phosphate and calcium carbonate solubilities were calculated from data obtained for near‐bottom water samples from Lake Kinneret during the years 1975–1977. A potential diagram technique was used to determine which solid phase is in equilibrium with the solution. Both phosphorus and calcium carbonate solubilities are controlled, during the January–August period, through equilibrium with calcium‐carbonate‐phosphate, Ca3(HCO3)3PO4. The calcium carbonate ionic product changes, depending on the phosphoric acid potential, during this period. The solubility product, (Ca2+)3 ×(HCO3−)3 ×(PO43−) is 10−28.5. Calcium carbonate activity is constant (10−8.56) during the last months of the stratified period (September–December). These findings support the hypothesis that the first and most reactive product of the reactions occurring between CaCO3 and phosphorus is a CaCO3H3PO4 surface complex.