Gas-phase ammonia and PM ammonium in a busy traffic area of Nanjing, China.

The gas-phase ammonia (NH) and fine particle PM ammonium (pNH) (collectively, NHx) were monitored between July 2013 and August 2014 in a busy traffic area of Nanjing, China. Results showed that PM concentration was 66.7 μg m, and NH concentration was 6.66 μg m. In the PM, the concentration of pNH was 3.04 μg m, SO (pSO) was 10.16 μg m, and NO (pNO) was 1.60 μg m. The significant correlation curves from the tests of PM revealed that molar ratio of pNH and pSO was approximately 2, which could be (NH)SO. Particulate NH primarily associated with pSO, which accounted for 4.54 % of total PM mass. The PM observed acidic and the NH in the atmosphere neutralized acidic species, mainly in a sulfate form. The traffic intensity in the region was partially related to the formation of PM and NH, suggesting that traffic pollution may be an important source of PM. The reaction between NHx and acidic species was assumed to the secondary PM. The neutralization and photochemical property of NHx were discussed. [ABSTRACT FROM AUTHOR]