Quantitative data on carbon fractions in interpretation of black crusts and soiling on European built heritage

Black crusts have been known for decades to be one of the major damage features affecting the built heritage in urban
areas worldwide. Their patterns, surface distribution and composition have evidenced the key role played by
carbonaceous particles ofatmospheric origin, which have been studied on the basis of single particle analyses with the
aim ofidentif ying the sources. The paper intends to fill the existing gap on the quantification ofthe carbonaceous
fraction within damage layers. Organic and elemental carbon (OC and EC) in damage layers on historic buildings were
measured at different European urban sites. The data reported show how OC and EC concentrations and OC/EC ratio
are typical ofeach site and provide essential in-put for an exhaustive investigation ofblack crust formation. The organic
carbon concentration is found to predominate over the EC concentration at almost all the target sites. In view of
foreseeable future trends of multipollutant deposition on the built heritage, the OC and EC concentrations become the
most important components to be quantified within black crust. The paper is pioneering in presenting data directly
correlated with the blackening encountered on European cultural heritage.