Studies of the Impact of Organic Nitrates on Nitrogen Cycling and Aerosol Production

Purdue University, West Lafayette IN

Investigators

Abstract

This project aims to improve the understanding of the role of organic nitrates as reservoirs for atmospheric nitrogen oxides, and the role of biogenic volatile organic compound (BVOC) oxidation in the production of organic nitrates. Organic nitrate production can limit the production of ozone, and deposit atmospheric nitrogen back to forests, where it can be utilized in plant biochemistry and thus carbon sequestration. This study also aims to better understand the role of organic nitrates derived from BVOCs in the production of secondary organic aerosol SOA, and chemistry in the aerosol phase that can result in low vapor pressure products contributing to SOA mass. The focus is on improving our understanding of the atmospheric chemistry of three of the most important BVOCs (representing approximately 600 teragrams per year of emissions), i.e., isoprene, alpha-pinene and beta-pinene. The specific objectives are: 1. Determine individual and total gas phase yields of organic nitrates from hydroxyl radical (OH) reaction with alpha- and beta-pinene, as well as measurements of the aerosol phase organic nitrate yields. 2. Study the partitioning of the alpha-pinene and beta-pinene nitrates between gas and aerosol phases. 3. Investigate aerosol-phase chemistry, specifically oxidation and oligomerization of organic nitrates, and sulfonation of olefinic nitrates and those with alcohol groups. 4. Measure the OH and ozone reaction rate constants for isoprene nitrates and alpha-pinene nitrates (APNs), and measure the yield of nitrogen dioxide from OH- and ozone oxidation of these species. 5. Develop detailed photochemical oxidation mechanisms for isoprene and alpha- and beta-pinene. Improved understanding of this chemistry will aid in the ultimate development of Earth System Models that describe the chemistry of BVOCs and their impact on climate and air quality. Collaborations will be established with scientists and students at the University of East Anglia (UEA) in the United Kingdom, and at other partnering universities, thus creating opportunities to connect students at Purdue and the partnering universities in semester or summer abroad experiences that include participation in research in the respective collaborators' laboratories. Local high school students and teachers will be engaged in the science, through participation in the Global Ozone Project (see: http://go3project.com/network2/ index.php/ pages/home), which involves a network of measurements of tropospheric ozone by students, who learn about atmospheric science through active research. Specifically, an ozone instrument will be installed in a rooftop weather station at West Lafayette Junior/Senior High School where an earth science class will participate in the interpretation of data, and incorporation of that data in a global network of similar measurements, that can connect their learning to that of other students around the world. Interpretation of data will teach them about relationships between human activities, weather, and air quality. Students will be invited to attend the principal investigator's group meetings, and connect to this research, so that high school students get an advance perspective on how science is conducted in a university research laboratory. Graduate students will engage in this process, so that learning is a two-way effort for the students.