Contribution of marine biological emissions to gaseous methylamines in the atmosphere: An emission inventory based on multi-source data sets.

Methylamines are a class of highly reactive organic alkaline gases in the atmosphere. At present, the gridded emission inventories of amines used in the atmospheric numerical model is mostly based on the amine/ammonia ratio method and do not consider the air-sea exchange of methylamines, which oversimplifies the emission scenario. Marine biological emissions (MBE), an important source of methylamines, has been insufficiently investigated. These shortcomings in the inventories can limit the simulation of amines by numerical models in the context of compound pollution in China. To acquire a more complete gridded inventory of amines (monomethylamine (MMA), dimethylamines (DMA), and trimethylamines (TMA)), we established a more reasonable MBE inventory of amines by using multi-source data sets (Sea Surface Temperature (SST), Chlorophyll-a (Chla), Sea Surface Salinity (SSS), NH3 column concentration (NH3), and Wind Speed (WS)), and merged it with the anthropogenic emissions (AE) inventory (by adopting the amine/ammonia ratio method and the Multi-resolution Emission Inventory for China (MEIC)). The new methodology can reveal the air-sea exchange fluxes and direction of different amines. Oceans can act as a sink for DMA and source for TMA while it can be either a source or sink for MMA. The concentration of amines above the coastal area increased significantly when the MBE was merged to the AE inventory. TMA and MMA showed significant increases, TMA increased by 43,917.0 %, and 804.0 %, in July 2015 and December 2019, respectively; while MMA increased by 2635.4 % and 0.37 % during the same periods; however, only slight changes were observed in the DMA concentration (-3.9 % in July 2015, and 1.1 % in December 2019). WS, Chla, and the total dissolved concentration of amines ([C+(s)tot]) were found to be the dominant factors affecting MBE fluxes. In addition, the emission fluxes and spatial distribution of AE, and wet deposition also affect the simulation of amines concentration.