Environmental Controls on Carbonate Mineral Dissolution: Rates and Magnitudes

• Main Author: Ezell, John E
• Language: English
• Published: University of Florida 2016
• Subjects: carbonates; dissolution; karst; kinetics; Carbonic acid
• Online Access: http://ufdc.ufl.edu/UFE0049519/00001

Carbonate dissolution in low elevation karst settings is driven by precipitation which reacts with the land surface and can force river water into river banks and spring systems. The dissolution driven by precipitation occurring prior to reaching the river was found to be greater than dissolution driven by river water intruding the river banks and springs. River water dissolution also occurred less frequently than the precipitation dissolution, but river water dissolution is more intensely concentrated than precipitation dissolution which is spread more evenly over the drainage basin. Dissolution driven by river water forced into spring systems can be up to up to 17 orders of magnitude faster than rates seen at baseflow which makes dissolution in spring systems episodic. During spring reversals dissolution is driven by the initial undersaturation of river water with respect to calcite and prolonged by organic carbon remineralization. Dissolution occurring during a spring reversal is slowed more by mixing with waters near saturation with respect to calcite than by the addition of calcium ions due to dissolution. The balance of dissolution driven by precipitation and river waters is key in the hydrology and geomorphology of north Florida. Dissolution can also affect the geomorphology of blueholes in coastal settings where biogeochemical reactions control carbonate dissolution. In blueholes tidal and diel cycles vary the influence of vegetation photosynthesis and respiration byproducts on water column chemistry. During the day sulfuric acid is formed and carbonic acid is formed at night. Sulfuric acid was found to be responsible for twice as much dissolution as carbonic acid and bluehole morphology supports this conclusion by demonstrating the greatest dissolution expansion where the sulfuric acid is produced. Carbonate dissolution shapes karst landscapes and can be influential in regional hydrology.