This symposium seeks to bring together environmental and atmospheric photochemists to help bridge the topics of aquatic photochemistry and aerosol photochemistry. The field of aquatic photochemistry seeks to understand the photochemical properties of dissolved organic matter which lead to the degradation of pollutants, particularly in the context of water treatment. On the other hand, the field of aerosol photochemistry seeks to understand the properties of the organic fraction in atmospheric aerosol capable of impacting climate through aerosol-radiation and aerosol-cloud interactions. Both fields have similar goals of characterizing the response of organic matter whether it be in lakes, rivers and oceans or in the atmosphere to sunlight exposure. This symposium will facilitate these two fields coming together to share techniques, sampling protocols and chemical insights. The symposium will gather field and laboratory researchers, environmental engineers, aerosol scientists, and atmospheric chemistry modelers with the goal of discussing emerging research in photochemistry of organic matter both in the aquatic and aerosol phases.