Air pollution loads on historical monuments: an air quality model application to the marble Arch of Titus in Rome

Atmospheric pollution is one of the reasons for stone weathering of monumental structures; at the same time old town centres are high concentration areas of pollutant sources (traffic and domestic heating) and of outdoor works of art. The use of air dispersion models represents a short means of answering many questions concerning pollution and it is a complementary way to the traditional ad hoc measurement of pollutant concentrations. An application of DIMULA, an analytical multisource dispersion model, and of CALINE 3, an air dispersion model specially developed for pollutant line sources (road links) will be described. The first was applied to the entire urban area of Rome and the second to the surroundings of the Arch of Titus. A simulation was performed relative to the period of in situ monitoring of air pollutant species and meteorological conditions. Moreover simulations of the effect of possible actions to reduce pollution around the monument (e.g., traffic limitation, use of different fuels) have been performed. Once the model has been validated, this approach, compared with the traditional approach involving a large amount of measurements, has the merits of being reliable and economical.