Simulation of the dissolution of weathered versus unweathered limestone in carbonic acid solutions of varying strength
Abstract A simulation was undertaken within a climatic chamber to investigate limestone dissolution under varied carbonic acid (H 2 CO 3 ) strengths as a possible analogue for future increases in atmospheric CO 2 arising from global warming. Twenty‐eight samples cut from a block of Bath (Box Hill) l...
| Published in: | Earth Surface Processes and Landforms |
|---|---|
| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
2006
|
| Subjects: | |
| Online Access: | http://dx.doi.org/10.1002/esp.1441 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fesp.1441 https://onlinelibrary.wiley.com/doi/pdf/10.1002/esp.1441 |
| Summary: | Abstract A simulation was undertaken within a climatic chamber to investigate limestone dissolution under varied carbonic acid (H 2 CO 3 ) strengths as a possible analogue for future increases in atmospheric CO 2 arising from global warming. Twenty‐eight samples cut from a block of Bath (Box Hill) limestone from Somerville College, Oxford, which had been removed during restoration after 150 years in an urban environment, were weighed and placed in closed bottles of thin plastic containing varying concentrations of H 2 CO 3 . Half of the stone samples were derived from exposed surfaces of the stone block (weathered) while the others were obtained from the centre of the block on unexposed surfaces (unweathered). The purpose of this was to compare dissolution of previously weathered versus unweathered surfaces in strong (pH 4·73) versus weak (pH 6·43) solutions of H 2 CO 3 . A temperature of c. 19 °C was maintained within the chamber representing a plausible future temperature in Oxford for the year 2200 given current warming scenarios. The simulation lasted 25 days with a few stone samples being removed midway. Stone samples show reduced weight in all cases but one. There was greater dissolution of stone samples in a strong H 2 CO 3 solution as conveyed by higher concentrations of total hardness and Ca 2+ in the water samples as well as enhanced microscopic dissolution features identified using SEM. The simulation confirms that enhanced atmospheric CO 2 under global warming, given adequate moisture, will accelerate dissolution rates particularly of newly replaced limestone building stones. However, previously weathered surfaces, such as those on historical stone exposed for a century or more, appear to be less susceptible to the effects of such increased rainfall acidity. Conservation techniques which remove weathered surfaces, such as stone cleaning, may accelerate future decay of historical limestone structures by increasing their susceptibility to dissolution. Copyright © 2006 John Wiley & Sons, Ltd. |
|---|