Estimating the Age of Lime Mortars by Luminescence to Measure Pollution Rates

Lime mortars can suffer alterations when subjected to gaseous pollutants. Particulate air pollutants can also be deposited and incorporated to the mortar surfaces. Thus, they can be used as pollution tracers allowing us to measure deposition rates of pollutants to compare pollution loads. To calculate deposition rates the absolute age of the studied mortars must be known. Luminescence dating allows estimating the age of lime mortars but involves some partially unsolved problems. Luminescence yields the age of an object from the ratio between paleodose or cumulative radiation dose in the minerals of that object and the annual dose rate of ionizing radiation. The development of optically stimulated luminescence (OSL) in the last years and the application of statistical tools have resulted in the first dating of lime mortars. In this work mortars from old buildings and have been collected from two urban sites (A Coruña, Spain, and Braga, Portugal) to estimate their ages by luminescence. Thus, the mortars could be used as passive samplers to calculate deposition rates and relate these to different pollution loads. Results show partial successful estimates and some related problems in younger mortars are discussed.
Fundação das Universidades Portuguesas e Ministerio de Ciencia e Innovación (Espanha) através da “Ação Integrada E-141/10"/“Acción Integrada PT2009-0077” (Espanha)
Projeto PUDC10N04 da Universidade de A Coruña
Fundação para a Ciência e Tecnologia (programa plurianual de financiamento das unidades de investigação; fundos nacionais).