Orthophosphate and Calcium Carbonate Solubilities in the Upper Jordan Watershed Basin
- Yigal Salingar *,
- Yoel Geifman and
- Michael Aronowich
An understanding of the mechanisms controlling the P concentrations in the Upper Jordan River is necessary to develop strategies to avoid eutrophication of Lake Kinneret. This study examines the solubility of orthophosphate and CaCO3 in the calcareous Upper Jordan Basin via a thermodynamic model. The variation in alkalinity, pH, Ca, and phosphate concentrations in the surface waters of the Jordan River are consistent with an equilibrium between the solution and a metastable Ca phosphocarbonate phase with an apparent composition of Ca2(HCO3)2HPO4. This phase, CBP2, has not been observed in sediments or suspended particles. However, it rapidly forms on calcite surfaces in laboratory experiments. The CBP2 is replaced after a few days by a more stable compound, CBP3, with an apparent composition of Ca3(HCO3)3PO4. The apparent solubility product of CBP2 is 10−19.96±0.87. The consistency of the observed water chemistry collected from a variety of stations in the Upper Jordan Watershed over a period of 20 yr with this simple metastable “equilibrium” model suggests that CBP2 is rapidly formed in the Jordan River waters and its tributaries and needs to be considered in models of fluvial P transport.
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