Measurement of atmospheric amines and ammonia using the high resolution time-of-flight chemical ionization mass spectrometry

Ammonia (NH₃) and amines play important roles in the nucleation and growth of atmospheric aerosols. To identify the sources of these chemicals in the densely populated and industrialized Yangtze River Delta region of China, we conducted measurements of NH₃ and several amines, including methylamine (CH₃NH₂), C₂-amines (C₂H₇N), and C₃-amines (C₃H₉N) at a suburban site of Nanjing, China, during summer 2012. Using a high-resolution time-of-flight chemical ionization mass spectrometer (HRToF-CIMS, Aerodyne), 1-min-averaged concentrations of NH₃ and amines ranged from a few parts per trillions by volume (pptv) to dozens of parts per billion by volume (ppbv). The average±1σ concentrations of NH₃ and total amines during the measurement period were 1.7±2.3ppbv and 7.2±7.4 pptv, respectively. Among the amines, C₂-amines were the most abundant, accounting for 54% of the total amine loading. Significant correlations between NH₃ and all three types of amines (0.65<r²<0.80) indicate similar emission sources. Analysis of meteorological conditions indicated that these NH₃ and amine laden air masses mainly originated from nearby industrial areas where NH₃ was used for selective catalytic reduction of nitrogen oxides (NO_x). The results of this work indicate that industrial emissions in Nanjing, China may have a significant impact on local and regional aerosol chemistry by supplying considerable amount of amines.