THE INFLUENCE OF COMBUSTION-DERIVED POLLUTANTS ON LIMESTONE DETERIORATION .1. THE DRY DEPOSITION OF POLLUTANT GASES

Citation
Jb. Johnson et al., THE INFLUENCE OF COMBUSTION-DERIVED POLLUTANTS ON LIMESTONE DETERIORATION .1. THE DRY DEPOSITION OF POLLUTANT GASES, Corrosion science, 38(1), 1996, pp. 105-131
Citations number
52
Categorie Soggetti
Metallurgy & Metallurigical Engineering
Journal title
ISSN journal
0010938X
Volume
38
Issue
1
Year of publication
1996
Pages
105 - 131
Database
ISI
SICI code
0010-938X(1996)38:1<105:TIOCPO>2.0.ZU;2-S
Abstract
This study concerns quantification of the relative chemical degradatio n effects of dry deposition of combustion-derived atmospheric pollutan ts, HCl, SO2 and NO2, on Portland and Monks Park limestones, employing laboratory exposure chambers for periods of 30 days. Using presentati on rates up to 40 x 10(-4) mu g cm(-2) s(-1), the pollutants were asse ssed individually and in various combinations, along with ozone as oxi dant, at 84% RH with dry or water-wetted surfaces. The degradation was followed by analysis of exposed stone, for Cl-, SO42- and NO3-, and o f run-off solution for Ca2+, in addition to the anions. From these dat a, the total calcium released from limestone to reaction ions and prod ucts and the percentages of each pollutant reacted (and so the deposit ion velocity (V-D)) in each exposure regime were calculated. HCl acted independently of the presence of other pollutants, showed 40 and 100% reaction (mass transport control) and V-D values of 2.2 and 5.3 mm s( -1), at 84% RH and on wetted surfaces, respectively. The reactivity of SO2 rose from 2.5 to 35%, and V-D from 1 to 2.9 mm s(-1), from condit ions of 84% RH to those with the presence of water, NO2 and O-3. Simil arly, the reactivity of NO2 rose from 3 to 40% at 84% RH in the presen ce of SO2 and O-3, with a V-D at 3 mm s(-1), but decreased in the pres ence of run-off solution. A limited study was performed on smoke-coate d and naturally exposed, reaction-product-coated, samples. In addition to obvious factors such as deposited mass, chemical constitution and transfer, smoke particle size distribution should also be considered i n any possible action on limestone. Concerning naturally exposed sampl es, non-wetted surface reaction products tended to reduce the attack o f pollutants, but had no resisting effect when wetted.