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 of atmospheric origin, which have been studied on the basis of single particle analyses with the aim of identifying the sources. The paper intends to fill the existing gap on the quantification of the 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 of each site and provide essential in-put for an exhaustive investigation of black 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.