Sea salt particles, one of the major sources of atmospheric aerosols, undergo complex multi-phase reactions and have profound consequences on their physical and chemical properties, thus on climate. Depletion of chloride in sea salt particles was reported in previous field studies and was attributed to the acid displacement of sea salt chlorides with inorganic acids, such as nitric and sulfuric acids. Some studies have also showed that the chloride deficit cannot be fully compensated by this mechanism. For the first part, I will present a new important pathway contributing to this chloride depletion: reactions of weak organic acids with sea salt particles.

Aerosol particles can serve as ice nuclei (IN) and thus initiate cirrus and mixed-phase cloud formation thereby indirectly affecting the climate. Atmospheric ice crystal formation by heterogeneous nucleation is poorly understood and poses one of the largest uncertainties in predicting future climate. I will present my Ph.D work on heterogeneous ice nucleation efficiencies and water uptake by various types of laboratory-generated and field-collected anthropogenic and marine impacted particles for temperatures and relative humidity typical of the troposphere.