Date of Award

Summer 2019

Project Type

Thesis

Program or Major

Earth and Environmental Sciences

Degree Name

Master of Science

First Advisor

Jack E Dibb

Second Advisor

Meredith G. Hastings

Third Advisor

Katharine A Duderstadt

Abstract

The Western wildfire Experient for Cloud chemistry, Aerosol absorption, and Nitrogen (WE-CAN), an NSF funded multi-platform campaign, launched with the goal of expanding scientific knowledge of the complex chemical reactions taking place inside biomass burning plumes. As a part of the WE-CAN 2018 field campaign this investigation focuses on the diurnal cycles of nitrous and nitric acid in fresh and aged smoke plumes from the Rabbit Foot Fire in the Salmon-Challis National Forest, ID. The measurements of nitrous and nitric acid in smoke plumes were made with a dual Mist Chamber/Ion Chromatograph system installed in the NOAA CSD mobile laboratory.

From these measurements we observe a clear distinction between daytime and nighttime levels of nitrous and nitric acid in smoke plumes. Nitrous acid levels peaks in the early morning hours, as high as 2ppb, and dissipates a few hours after sunrise to ~50pptv. In contrast, nitric acid levels are highest in aged smoke, 0.5 ppb, and lowest during the nighttime hours, ~20pptv. We also observe a high level of variability in individual plumes. Sample to sample concentrations of nitrous and/or nitric acid vary as much as 50%. Additionally, the two species increase both in and out of phase with one another with no distinct pattern. The ratio of the two species is a useful metric for determining the age or level of chemical processing the plume had undergone. Most prominently, we observe the rapid production of HNO3 outpaced the production of HONO during both day- and nighttime regimes.

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