Laboratory measurements of sulfur dioxide deposition velocity on marble and dolomite stone surfaces

The deposition velocity of SO₂ on marble and dolomite stone surfaces in a humid atmosphere was measured as a function of time in the laboratory using continuous monitoring techniques. The deposition velocity of SO₂ on marble varied between 0.02 and 0.23 cm s⁻¹, and was generally observed to decrease with time. The deposition velocity of SO₂ on dolomite varied between 0.02 and 0.10 cm s⁻¹, and gradually increased over the first 2000 ppm-h of exposure. For both types of stones, the deposition velocity increased significantly when condensed moisture was observed on the stone surface. Chemical analysis of the stone samples indicated that the SO₂ deposited reacted with the stone materials to form gypsum (CaSO₄·2H₂O) on the marble surfaces and gypsum and epsomite (MgSO₄·7H₂O) on the dolomite surfaces.