Methylamines in the marine atmosphere

There is growing recognition of the possible importance of organic nitrogen compounds in the global atmospheric nitrogen cycle. Concentrations of gaseous methylamines (MAs) have been measured for the first time in the atmosphere of two non urban regions‐coastal Hawaii and Rhode Island. In Hawaii gaseous MA concentrations were as follows: monomethylamine (MMA), 11±5 pmol/m³ dimethylamine (DMA), 93±51 pmol/m³ and trimethylamine (TMA), 30±19 pmol/m³. Concentrations of these compounds were also measured in coastal seawater in Hawaii and Massachusetts and in rainwater from Rhode Island. Calculations of the fluxes of MAs across the air‐sea interface indicate that the oceans are a source for MMA and TMA but may be a sink for dimethylamine (DMA). The concentrations of MAs observed in rain can largely be explained by scavenging of gaseous MAs. Another important removal process for atmospheric MAs appears to be oxidation by OH radicals. Wet and dry removal combined with OH oxidation appear to balance oceanic production of MMA and TMA in the Hawaii region. Significant uncertainties remain about the cycling of DMA.