Determination of Heterogeneous Photochemistry Related to Atmospheric Reactive Nitrogen Species

Health Research Incorporated/New York State Department Of Health, Menands NY

Investigators

Abstract

Nitrogen oxides (NOx = NO+NO2) play a pivotal role in ground-level ozone formation, stratospheric ozone depletion, and acid deposition. Understanding atmospheric chemistry of reactive nitrogen species (NOY, where NOY is defined as the sum of NOx and the atmospheric oxidation products of NOx) is critical to pollution prevention and control efforts. While the homogeneous gas phase photochemistry of a large number of NOY has been studied, much less is known about the heterogeneous photochemistry of NOY species such as nitric acid (HNO3) and peroxynitric acid (HO2NO2). The photolysis of adsorbed HNO3 on ground surfaces has been proposed as a major daytime source of HONO in low-NOx environments. Little is known in particular about the UV absorption cross sections and the photolysis quantum yields of HNO3/H2O co-deposited on surface. The project seeks to characterize heterogeneous photolysis of surface-adsorbed HNO3 both in the absence and in the presence of water vapor, of HNO3/H2O co-deposited on surface, and of surface-adsorbed HO2NO2. Wavelength-dependent UV absorption cross sections of surface-adsorbed HNO3, HNO3/H2O, and HO2NO2 will be determined using Brewster-angle cavity ring-down spectroscopy. The photodissociation pathways and product yields from the heterogeneous photolysis of these species will be measured by combining laser photolysis either with Brewster angle cavity ring-down spectroscopy (fused silica surface) or with cavity ring-down spectroscopy (Al or ice film surface). The project will provide information essential to the assessment of the role of heterogeneous photolysis in converting NOx reservoirs into active forms and in producing tropospheric odd hydrogen radicals. The project will directly lead to the research training of a graduate student and a postdoctoral scholar. In addition to presenting research findings at national and international conferences by the project director, postdoctoral scholar and graduate student, and publishing results in professional journals, the project director, Dr. Lei Zhu, plans to periodically give lectures in the local colleges and universities in the region to share the research results with scientists in the area, excite students' interests in science, and promote intellectual exchanges between different institutions. The Principal Investigator (PI) also plants to increase outreach efforts and to contribute to the goal of diversity and inclusiveness in university education. SUNY-Albany has existing outreach programs such as the Shepherd Project. The Shepherd Project has the goal of establishing long-term partnerships with faculty at historically minority colleges. The PI plans to become an active member in the Shepherd Program at SUNY-Albany.