Evaluation of Halogen-Induced Ozone Depletions Near Salt Lake City
Abstract
An unexpected halogen-rich plume, originating from an industrial plant on the western shore of the Great Salt Lake, was sampled on nine separate flights during the NOAA 2017 Utah Winter Fine Particulate Study (UWFPS). Tropospheric ozone depletions were also measured in the halogen plume, analogous to halogen-induced ozone degradation in other regions of the atmosphere such as the arctic troposphere and the stratosphere. Our study sought to quantify the halogen flux from the industrial plant and to characterize the photochemical processes that result in tropospheric ozone depletions. Flux calculations for chlorine and hydrochloric acid emitted by the industrial plant were predominantly within the same order of magnitude as per-second flux values derived from the plant's EPA emissions inventory. The inventory does not report fluxes of bromine and bromine chloride, but our calculated fluxes of these species were also significant. Assumptions of instrument sensitivity, constant wind speed, and plume behavior introduced uncertainty into the flux calculations. The ozone depletions were investigated using a semi-Lagrangian plume setup in a zero-dimensional atmospheric chemistry box model (F0AM). Our box model was able to reproduce the magnitude of ozone depletion observed in the daytime January 26 plume (>35 ppbv below background levels). The model confirmed that chlorine and bromine radicals, generated from the photolysis of halogen species emitted by the plant, were responsible for the observed ozone depletions. Bromine chemistry dominated the ozone depletion due to its higher reaction rate with ozone, despite its lower emission relative to chlorine. The results of the modeling component of our study suggest that atypical levels of industrial halogen emissions may have significant impacts on local air quality, which is particularly relevant in the case of this industrial plant due to its close proximity to Salt Lake City.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA150.0010C
- Keywords:
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- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3355 Regional modeling;
- ATMOSPHERIC PROCESSES