Modelling effects of alkylamines on sea salt aerosols using the Extended Aerosols and Inorganics Model

Sea salt aerosols are known to serve as effective cloud condensation nuclei and are prominent contributors of light scattering in the atmosphere. More light scattering reduces solar radiations to the Earth and lowers the global temperature. Researchers observed that ambient sea salt aerosols may contain ammonium sulfate (AS) and sodium chloride (NaCl). Recent studies showed that alkylamines, derivatives of ammonia, can react with ammonium salts in the aerosol, displacing ammonium and altering the particle’s properties. Our study investigated the effects of atmospheric alkylamines on the properties of sea salt aerosols using a chemical system of methylamine (MA), AS, and NaCl. We determined the relative humidity when these aerosols start to absorb water vapor from the air (deliquescent relative humidity, DRH), and concentrations of ammonia and MA in aqueous/gas phases using the Extended Aerosols and Inorganics Model. Our findings indicate a notable negative relationship between MA concentration and the DRH for both AS and NaCl. We determined that five parts per billion or higher of MA effectively lowered the DRH of sea salt aerosol particles. The concentrations of ammonia and MA in aqueous and gas phases had a complex dependence on MA concentration and aerosol chemical composition. Aerosol deliquescence often leads to cloud/fog processing which may cool the Earth by reflecting sunlight away from the surface. Therefore, our results implicate a potential role for alkylamines in climate change, suggesting the importance of monitoring alkylamine concentrations in the atmosphere. Future studies are needed to better predict the deliquescent behaviors of aerosols, namely particles containing AS and NaCl, such as those found near coasts.