THE EFFECT OF A BIOCIDE TREATMENT AND A SILICONE TREATMENT ON THE WEATHERING OF LIMESTONE

The effects of a biocide treatment, pentachlorophenol, and a silicone water repellant on the dissolution processes of limestone were investigated. Limestone microcatchment units were exposed on the pavillion roof of Trinity College, Dublin for a period of 68 days. The effect of the treatment on the chemical composition of runoff from the units was investigated. The pentachlorophenol treatment appeared to cause a decrease in the output of bicarbonate and an increase in the output of nitrite, nitrate and ammonia from the limestone when compared with untreated control stones. These effects are thought to be due to the elimination of biological growth from the stone. The silicone treatment appeared to have decreased the bicarbonate and particulate output relative to the untreated stones. This effect is thought to be due to the decreased residence time of water in the stone.