Ss. Yerrapragada et al., RATE OF WEATHERING OF MARBLE DUE TO DRY DEPOSITION OF AMBIENT SULFUR AND NITROGEN DIOXIDES, Analytical chemistry, 66(5), 1994, pp. 655-659
The thickness of crust upon marble is a measure of weathering due to d
ry deposition of pollutants in industrial environments. We monitored t
he rate of growth of crust upon marble due to the reaction of ambient
SO2 and NO2 with samples exposed outdoors but protected from rain. Eve
n when the atmospheric NO2 exceeded the SO2, the reaction product calc
ium sulfate exceeded calcium nitrate, indicating the predominance of S
O2 in marble decay. This result is consistent with a study of monument
s in cemeteries in the Los Angeles basin, where the NO2 concentration
has long been larger than the SO2 concentration. The kinetic rate cons
tant and the diffusion coefficient were obtained from a model equation
as being 395 cm/h and 0.13 cm(2)/h, respectively. These constants all
ow the prediction of crust thickness in a wide range of SO2 and NO2 co
ncentrations.