It is well known that the inorganic mineral phase, calcite (CaCO3), is commonly supersaturated in natural waters, with no observed precipitation (Reynolds, 1979). The reason for this phenomenon is that crystal growth is greatly reduced by various naturally-occurring kinetic inhibitors, e.g. magnesium ion, phosphate ion and dissolved organic carbon.
In the Everglades calcite precipitation associated with periphyton (shallow algal mats) has a pronounced effect on pH, pO2, pCO2, calcium concentration and bicarbonate concentration. Calcite precipitation may also influence the bioavailability of phosphorous and may be responsible for low natural concentrations of phosphorous in Everglades waters (Browder et al., 1994).
Calcite precipitates in the presence of algae because of the localized environment of high pH and elevated calcium and bicarbonate concentration. It has been proposed that presence or absence of calcite in the periphyton is related to hydrology and effects of dilution on supersaturation (Gleason and Stone, 1994), with no consideration of inhibitory kinetic effects.
In this poster we present results showing effects of natural hydrophobic organic acids from the Everglades on calcite crystal growth kinetics.
