ASSESSING CARBON DIOXIDE-INDUCED ACIDIFICATION ON CARBONATE-BEARING MATERIALS

Carbonate-bearing rocks are susceptible to chemical erosion from low-pH solutions such as rainwater and other acids. Marble and limestone have revealed noteworthy differences in their dissolution rates when exposed to carbonic acid, despite an identical chemical composition. This indicates that a structural component of the limestone and marble is affecting the dissolution rate. Carbonate-bearing materials such as marine animal shells and dolostone are also susceptible to chemical erosion. Materials like these, that are not completely composed of calcite, should have a different dissolution rate than limestone and marble. The impact of the dissolution rate discrepancy was tested by comparing the rates of the calcium carbonate polymorphs to other carbonate-bearing materials such as dolostone and organic shells. Samples of mineral calcite, marble, dolostone, and organic CaCO3 were weighed and placed into test tubes with liquids of various pH levels such as seawater, deionized water, hydrochloric acid, and carbonic acid. These samples were sealed for 7 days, then removed from the test tubes and weighed again to determine the change in weight percentage. This process was repeated 3 times for each sample. There was a noticeable discrepancy between the mass weight percent of the carbonate polymorphs, the dolostone and the organic shells from each other. Increasing carbon dioxide concentration in the atmosphere has increased the acidity of rainwater and the oceans from carbonic acid creation, increasing the amount of chemical erosion in carbonates. Understanding the differences in acid susceptibility between carbonates and carbonate-bearing organics can predict changes to sea life population and shoreline degradation.