Suspended matter in run-off water from limestone exposure setups

The effects of air pollution on stone deterioration can be assessed by analyses of the run-off water from exposure racks. Many research programmes calculate the material loss of limestone from the calcium ion concentration in solution. This paper provides evidence of the high calcium content in the non-dissolved matter in limestone run-off water. For this purpose, run-off water was collected from freshly quarried limestone slabs exposed in the field. Analyses by means of electron probe X-ray micro-analysis, energy-dispersive X-ray fluorescence analysis and atomic absorption spectrometry have been performed on the suspension in the run-off water in order to identify the suspended matter in the run-off water and to assess the importance of the material lost in the solid phase relative to that in the dissolved phase. By not considering the stone material which is eroded in the suspended phase this gives a serious underestimation of the erosion rates.