Fourier transform infrared measurement of the formation of nitrogen compounds on sodium chloride particles exposed to the ambient air in the Arctic

The role of heterogeneous reactions on sea salts in the formation of particle nitrogen compounds in the Arctic during polar sunrise was studied. A diffuse reflection type Fourier transform infrared spectrometer was used to measure surface products on sodium chloride (NaCl) particles exposed to the ambient air at Alert, Northwest Territories, Canada (82.5°N, 62.3°W). The accumulation of nitrogen compounds on NaCl was observed in both winter and spring, while the rate in winter was greater. The important role of ambient N 2 O 5 as well as HNO 3 in the formation of nitrogen compounds on NaCl is deduced. The nitrogen compounds observed might be mainly composed of nitrate ion whose electronic states were different from those of nitrate ion in water solution and/or crystal. Its reactivity, including its possible photolysis to NO 2 − , is noted as to a potential formation pathway of particle nitrite in spring.