title: Sulphur and oxygen isotope analysis to identify sources of sulphur in gypsum-rich black crusts developed on granites.
abstract: We describe the results of sulphur and oxygen isotope analyses used to identify sources of the gypsum present in black crusts that grow on the granite of historical buildings. The crusts were sampled at various locations in and near the city of Vigo (NW Spain) and were analysed for their sulphur content and δ(34)S and δ(18)O isotope ratios. Sampled crusts had δ(34)S values of 7.3‰ to 12.9‰ and δ(18)O values of 6.56‰ to 12.51‰. Sampled as potential sulphur sources were bulk depositions, seawater, foundation, ashlar and construction materials and combustion residues. The results indicated marine and, to a lesser extent, anthropogenic, origins for the sulphur and ruled out the contribution of sub-soil sulphates by capillary rise from building foundations. Isotope analyses would indicate that cement and mortar were enriched in sulphur after their application in buildings. The fact that facade orientation (towards the sea or fossil fuel pollution sources) was correlated with sulphur isotope distribution pointed to various contributions to black crust formation.
authors.affiliation: Dpt. Ingeniería de los Recursos Naturales y Medioambiente, E.T.S. Ingenieros de Minas, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain. Electronic address: trivas@uvigo.es.
authors.forename: T
authors.initials: T
authors.lastname: Rivas
authors.affiliation: Dpt. Ingeniería de los Recursos Naturales y Medioambiente, E.T.S. Ingenieros de Minas, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Pozo
authors.affiliation: Dpt. Ingeniería de los Recursos Naturales y Medioambiente, E.T.S. Ingenieros de Minas, Universidad de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Paz
mesh_terms: D002133:Calcium Sulfate / Q000032:analysis*; D003252:Construction Materials / Q000032:analysis; D004784:Environmental Monitoring; D010103:Oxygen Isotopes / Q000032:analysis*; D012623:Seawater / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013030:Spain; D013455:Sulfur / Q000032:analysis*; D013460:Sulfur Isotopes / Q000032:analysis*
chemical_list: D010103:Oxygen Isotopes; D013460:Sulfur Isotopes; C007886:granite; D013455:Sulfur; D012822:Silicon Dioxide; D002133:Calcium Sulfate
keywords: Black crust; Cultural heritage; Granite; Marine spray; δ(18)O; δ(34)S