Multiphase Chemistry of Organic Nitrates from Monoterpene Oxidation and Their Role in Aerosol Growth

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In this project funded by the Environmental Chemical Sciences program of the Chemistry Division, Dr. Jonathan H. Slade of Purdue University is investigating the processes that affect the lifecycle of organic nitrates that are produced in the atmosphere from organic compounds that are emitted by trees. Organic nitrates serve as an important reservoir and sink for nitrogen oxides, the precursor to tropospheric ozone. Organic nitrates also impact the formation and fate of particulate matter, which affects human health, cloud formation and Earth's surface temperature. To better understand the role organic nitrates play in air quality and climate, new measurements are being made regarding the uptake, multiphase processing, and fate of organic nitrates that contain reactive functionalities and remain reactive in the particle phase. This effort consists of both laboratory and field work which significantly extends a growing knowledge base of the impact organic nitrates have on the evolution of atmospheric particulate matter, air quality, and climate.This project focuses on the multiphase chemistry of olefinic organic nitrates and their impact on the formation and fate of organic aerosol in forested environments. The organic nitrate yields from the oxidation of multi-olefinic monoterpenes, and the aerosol uptake kinetics of synthetic multifunctional monoterpene organic nitrates are examined as a function of relative humidity and particle acidity using chemical ionization mass spectrometry (CIMS) coupled with a reaction chamber and aerosol flow reactor. In addition, the hydrolysis rates and subsequent aqueous-phase chemical transformations including oligomerization and sulfonation of these organic nitrates are being evaluated. The production and chemistry of gas- and aerosol-phase terpene nitrates in a forested environment are being investigated during two summer field studies. The research contributes broadly to a fundamental understanding of the factors affecting air quality and climate, with respect to: air pollutants and climate forcers, ozone and particulate matter. This work broadly impacts the education of undergraduate and graduate researchers. The research is used to develop an annual outreach program aimed at providing local area high school students the experience of conducting research related to atmospheric science, weather, and air quality.