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Hydroxyapatite rapidly precipitated onto quartz sand grains from a solution that was supersaturated with respect to hydroxyapatite, thus demonstrating that an input of P to Ca rich, alkaline porewaters can result in the precipitation of secondary hydroxyapatite. The dissolution rate of hydroxyapatite is strongly pH dependent, however within the aquifer porewaters, the solution is often close to equilibrium with respect to hydroxyapatite, which causes the dissolution rate to have a greater dependence on the PO43- concentration. Within the range of measured pH and PO43- concentrations, the dissolution rate ranges between 10-12.25 to 10-9.15 mol kg-1 s-1, contributing P to the catchment headwaters. Over a 1D flow path, there is dynamic precipitation and dissolution of hydroxyapatite, as well as PO43- 37 sorption and desorption, over relatively short timescales. These results indicate that hydroxyapatite is likely to precipitate within the pore space of the aquifer, but can then dissolve and re-precipitate, adsorb and desorb, under expected spatial and temporal variations in pH and water chemistry within the aquifer. Hydroxyapatite may therefore represent temporary pool of anthropogenic P, sourced from P-fertilisers, which represents a previously unrecognised pathway for anthropogenic P transfer between the soil surface and surface waters.
- mineral dissolution rates
- reactive transport
FingerprintDive into the research topics of 'Rates of hydroxyapatite formation and dissolution in a sandstone aquifer: Implications for understanding dynamic phosphate behaviour within an agricultural catchment'. Together they form a unique fingerprint.
- 2 Finished
Determination of the nature and origins of riverine phosphorus in catchments underlain by Upper Greensand Aquifer
1/04/16 → 31/03/20
1/01/16 → 31/12/18