Release of nitric oxide form building stones into the atmosphere.

Stone material from the corroding surface of buildings generally released nitric oxide with rates of 0.42-4.2 ng NO-N h high minus 1 g high minus 1 d.w. despite their large range of moisture, pH and content of anmonium, nitrite and nitrate. The net release rates of NO were independent of the NO mixing ratio of the atmosphere up to 1 ppmv NO. Whereas NO2 was taken up by all stones tested, uptake of NO was only observed in one out of five types of stone. NO release rates were highest at the stone surface and rapidly decreased in depth lower than 1 cm. NO release peristed for up to bigger than 3 months after the stone sample was removed from the building. NO was mainly produced during the biogenic oxidation of ammonium to nitrate at the stone surface which was probably due to endolithic nitrifying bacteria. Chemical decomposition of nitrite to NO and NO2 was only observed under acidic conditions.