LABORATORY MEASUREMENTS OF SULFUR-DIOXIDE DEPOSITION VELOCITY ON MARBLE AND DOLOMITE STONE SURFACES

The deposition velocity of SO2 on marble and dolomite stone surfaces i n a humid atmosphere was measured as a function of time in the laborat ory 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 dolo mite 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 depos ition velocity increased significantly when condensed moisture was obs erved on the stone surface. Chemical analysis of the stone samples ind icated 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.