Fate of Food Cooking Emissions in the Atmosphere

Food cooking emissions represent an important source of particulate matter in urban areas, contributing 10-35% of total organic aerosol. Cooking emissions also contribute significant levels of volatile organic compounds (VOCs) such as carbonyls which are important precursors to formation of secondary organic aerosol (SOA). In this work, I use heated cooking oils as a model to investigate the reaction pathways that drive formation of VOCs and cooking organic aerosol (COA), and their evolution in physicochemical properties. I demonstrate that VOCs and primary COA emissions are driven by autoxidation reactions involving radical species, and the composition of cooking oils strongly influences the reaction mechanisms. Antioxidants, routinely employed in food industry to delay oil oxidation have complex effects on autoxidation reaction mechanisms. Furthermore, in this work, physicochemical properties and chemistry of COA are investigated. I demonstrate that evaporation of oxidized cooking oil particles is much slower than unoxidized oil particles, despite containing a higher fraction of volatile reaction products than unoxidized cooking oil particles. Additionally, a new analytical approach was developed to characterize the chemical composition of SOA. It is shown that SOA formed from cooking oil vapors undergo fragmentation reactions with increasing atmospheric oxidative aging. Moreover, detailed chemical speciation and total production of SOA from heated cooking oils are explained from aldehydes and its oxidation products which are significant contributors to VOCs from cooking emissions. Overall, knowledge about both oxidation pathways provide useful insights into the importance of fragmentation reactions during evolution of cooking emissions in the atmosphere.Ph.D