Atmospheric nitric acid concentrations in a Mediterranean site, Patras, Greece

Atmospheric nitric acid was determined in two summer and one winter sampling periods. The 24 h mean summer concentrations were 3.2 and 4.1 μg m−3 and the winter one 1.2 μg m−3. Nitric acid showed a clear diurnal variation with the maximum concentrations occurring in the afternoon. Gaseous nitric acid is the predominant form of inorganic nitrate. Gas phase and particulate ammonia concentrations were very low so that solid NH4NO3 would not be expected to be formed under the hot and dry summer weather conditions of our area. Particulate Ca2+ is more likely the most important neutralizing agent.