Sources and concentrations of gaseous and particulate reduced nitrogen in the city of Muenster (Germany)

摘要

Atmospheric ammonia mixing ratios and the main inorganic ions NH_4~+, NO_3~- and SO_4~(2-) of size-resolved particles in the range from 0.05 to 10μm were measured at an urban site in Muenster, Germany. High mixing ratios of ammonia with a median of 5.2 ppb and a maximum of 50ppb were detected. The mass fraction of submicron particles was much higher during the day than at night. At night, a greater particle mass and an increased presence of particulate nitrate was measured. Recurring patterns of particle distribution were distinguished and their characteristics analysed. In half of the measurements, the accumulation mode was clearly dominating, which is an indication of aged aerosol. In some measurements, higher concentrations of fine particles were found indicating particle formation. In these cases, a smaller particle mass and about four times greater ratios of ammonia versus ammonium concentrations were observed. These data show that ammonia contributes considerably to the formation of secondary particulate material.