A quantitative methodology for carbon speciation in black crusts on monuments.

The availability of a correct, accurate and reproducible analytical method for a complete carbon balance in black crusts is of major importance in understand the effects of the interaction between atmospheric pollutants and the environment, particularly in the portioning of pollutant sources, damage mechanism identification, and a sustainable protection of cultural heritage. The EC Project CARAMEL has, among its primary goal, the setting up of a suitable and reliable analytic technique able to distinguish and measure carbon fractions in damage layers, particularly elemental carbon. The presence of a significant amount of carbonate carbon and the removal of organic carbon are critical steps in the measurement of carbon compounds in black crusts. A chemical-thermal methodology for carbon analyses in black crusts was set up whose specificity, accuracy and precision were tested on appropriate standard samples. The results obtained indicate that the methodology satisfactorily distinguishes among carbon species an allows a reliable evaluation of their quantities in damage layers.