Nitrite in rain and dew in Santiago city, Chile. Its possible impact on the early morning start of the photochemical smog

Cations (pH, potassium, sodium, calcium, magnesium, and ammonium) and anions (sulfate, nitrate, nitrite, and chloride) concentrations were measured in Santiago city rain and dew waters collected during the 1995 to 1999. Concentrations measured in dews are considerably higher than those measured in rains. The high ionic concentration present in dew waters could contribute to their corrosion potential. Natural dust makes an important contribution to the ions present in dews, but the presence of rather high sulfate concentrations (up to 900 μeq/l) indicate a significant contribution of anthropogenic sources. A peculiar characteristic of dew waters is the relatively high nitrite concentrations (up to 180 μeq/l). This nitrite can be resuspended into the boundary layer after dew water evaporation, possibly due to the relatively high volatily of ammonium nitrite. This upward flux could constitute an important source of hydroxyl radicals in the early morning, contributing so to the initial steps of the observed photochemical smog.