SGER: Independent Determinations of Bromine (Br) and Chlorine (Cl) in Barrow, Alaska

Ohio University, Athens OH

Investigators

Abstract

This project makes use of an Arctic sunrise experiment scheduled for March-April 2005 at Barrow, Alaska to evaluate a previously untested method for quantifying halogen atom activity in the Arctic troposphere. Halogen radicals such as bromine monoxide (BrO) and chlorine monoxide (ClO) catalyze ozone destruction photochemical cycles in the near-surface polar atmosphere and also in the remote marine boundary layer, thereby controlling to some extent the oxidizing capacity of the lower troposphere over select regions of the globe. Current chemical transport models of the Arctic springtime boundary layer calculate ratios of atomic Br to Cl, [Br]/[Cl], that are not consistent with observations of hydrocarbon loss rates. The PI will measure the [Br]/[Cl] ratios using (i) a traditional method inferring the ratio from relative loss rates of reactive hydrocarbons through reaction, and (ii) a previously untested method through direct measurement of the halogenated organic compound products. The broader impact of this research includes providing a fundamental test bed for a novel approach to addressing the confounding discrepancy between modeled [Br]/[Cl] ratios and those inferred from in situ measurements. Better constraints on these data should benefit understanding through improved insight into springtime polar halogen photochemistry and catalytic ozone destruction. This research also has policy implications in that mercury cycling, which affects exposure to the resident population, is intimately linked with these photochemical cycles. The project will facilitate original interdisciplinary collaborative research involving the PI as well as researchers at Purdue University and Argonne National Laboratory. The project will also support the dissertation research and professional development of a female graduate student. This project will be supported via a Small Grant for Exploratory Research funded jointly by the Atmospheric Chemistry Program and the Arctic Natural Science Program.