Caratterizzazione della qualità dell'aria all'interno e all'esterno della Chiesa di San Luigi dei Francesi in Roma

Simultaneous indoor and outdoor samples collected in the Church of San Luigi dei Francesi were analised for nitrous acid, sulphur dioxide, nitrogen oxides and ammonia in the gas phase and for ammonium, sulphate, and nitrate ions in the particulate matter. Indoor levels of nitrogen oxide, nitrous acid and ammonia were found to largely exceed those outdoors. For NO2 and SO2 lower indoor levels were always measured, while for nitrate and sulfate, the indoor/outdoor ratìos ranged from 0.5 to 3,5. These results show that indoor production of nitrous acid could result from heterogeneous reactions indoors, on the walls and exposed surfaces. Furthermore, they demonstrate that non-reactive species such as nitrogen oxide and particles penetrate indoors, where they remain segregated and are very slowly depleted, due to their small deposition velocities.