| We measured low molecular-weight alkylamines (methylamine, dimethylamine,ethylamine and diethylamine) in urban aerosols in the Yangtze River Delta region of eastern China in August, 2014 and from November, 2015 to May, 2016. After examining artifact formation on sample filters, methylamine, dimethylamine and ethylamine concentrations were quantified. The three C1-C2 amines exhibited a unimodal size distribution that maximized between 0.56nm and 1.0 μm. Their concentrations in PM2.5 were 5.7±3.2 ng/m3, 7.9±5.4 ng/m3 and 20.3±16.6 ng/m3,respectively, with higher concentrations during the daytime and in warm seasons.Amine uptake to particles larger than 56 nm was barely enhanced on new particle growth days. The molar ratios of individual amine/NH4+ were on the order of 10-4-10-3 in PM2.5. Amines were far less to out-compete NH4+ in neutralizing acidic species in particle sizes down to 56 nm. Abundant nitrate (NO3-/SO42- molar ratio ≈3)and its correlation to methylamine and ethylamine implied that nitrate might be the preferred aminium salt over sulfate in urban aerosols of this area. Direct measurement of particle-phase amine emission from coal and biomass burning showed that coal burning is an important atmospheric amine source, considering coal burning is top-ranked particulate matter source in China. |
