Gas-phase alkyl amines in urban air; comparison with a boreal forest site and importance for local atmospheric chemistry

Low-molecular-weight aliphatic amines were measured in the ambient urban background air at the SMEAR III station (Station for Measuring Forest Ecosystem–Atmosphere Relations III) in Helsinki, Finland, from May until late August 2011. The alkyl amines measured were dimethylamine (DMA), ethylamine (EA), trimethylamine (TMA), propylamine (PA), diethylamine (DEA), butylamine (BA) and triethylamine (TEA). se amines, DMA + EA and TMA + PA were the most abundant, with average concentrations of 24 and 8 ppt. The ranges of weekly mean concentrations of DMA + EA and TMA + PA were <DL (9.5 ppt) – 55 ppt and 4–27 ppt. The concentrations of all amines in urban background air in Helsinki were lower than at a boreal forest site (SMEAR II), indicating the presence at the latter site of some additional sources. Amine lifetimes are short, varying from 2.3 h to 7.6 h against hydroxyl (OH) radicals. The amine concentrations were scaled against OH reactivity and compared with the OH reactivities of aromatic hydrocarbons and terpenes. The results showed that amines strongly influenced the total OH reactivity, especially at the boreal forest site in May, September and October, showing contributions almost as high as those of monoterpenes.