Concentration and source of gaseous dimethylamine and trimethylamine and their particulate partners in marine atmospheres across the marginal seas of China

Ocean is an important source of amines in the atmosphere, but the transport mechanisms of the amines from ocean to atmosphere are poorly understood. In this study, high time-resolution mass concentrations of gaseous amines and their particulate partners in marine atmospheres were measured across the marginal seas of China in December 2019. The concentrations of atmospheric dimethylamine (DMA) and trimethylamine (TMA) were 0.006±0.006 μg m^-3 and 0.031±0.009 μg m^-3, respectively. Atmospheric DMA and TMA correlated well with ambient temperature during the sampling period, and their response to ambient temperature was stronger under larger wind speed (11.0±2.0 m s^-1), implying the volatilization of DMA and TMA from seawater was facilitated by high temperature and wind speed. The observed concentrations of dimethylaminium (DMA⁺) and trimethylaminium (TMA⁺) in PM_2.5 were 0.067±0.072 μg m^-3 and 0.29±0.18 μg m^-3, respectively. The TMA⁺ concentrations were from one to three orders of magnitude larger than the concentrations reported in most of other marine atmospheres. Based on the correlation analysis between DMA⁺ and TMA⁺ with ammonium (NH₄⁺) and meteorological conditions, we speculated that TMA⁺ was mainly emitted from ocean source and linked to the emissions of sea-spray aerosols especially under high wind speed. But DMA⁺ was probably associated with both emissions of ocean source and the long-range transport from adjacent continents.