Sviluppo di un campionatore diffusivo per la determinazione simultanea di acido nitrico, acido nitroso e biossido di azoto per il monitoraggio in ambienti interni e in ambienti dedicati alla conservazione dei beni culturali

In indoor environments NO2 hydrolysis can take place on surfaces covered by a thin layer of humidity leading to the formation of nitrous and nitric acid. The acidification, mainly caused by nitric acid which has the tendency to remain on the surfaces rather than being released in the air, can lead to damage to materials indoors. A correct speciation of compounds such as nitrous acid and nitrogen dioxide, intertwined through this hydrolysis mechanism and with a mutual interference on the measurements, could only be achieved by the subsequent collection of the two species on selective substrates. To overcome these problems a novel “multipollutant” diffusive sampler was designed for the collection of three different pollutants (nitric acid, nitrous acid and nitrogen dioxide) at separate sampling stages. The diffusive sampler was tested against reference techniques showing a good agreement and fulfilling the basic requirements of a measurement method (linearity, selectivity and reproducibility of the measurement provided). A survey aimed at a preventive conservation activity was performed inside two archives (Swiss National Library and Biblioteque de Geneve) using the new selective sampling method. Laboratory development, field validation and some results collected in indoor environments are reported and discussed.