Airborne Measurements of Organic acids, Inorganic acids and other Trace Gas Species in the Remote Regions of the Northern Hemisphere using a Chemical Ionisation Mass Spectrometer (CIMS)

• Main Author: Jones, Benjamin
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2016
• Subjects: Formic Acid; Nitric Acid; Dinitrogen Pentoxide; CIMS; Arctic
• Online Access: https://research.manchester.ac.uk/en/studentTheses/b67b7cf5-3ca1-4aaf-ab41-66c2b41c4a2f; https://pure.manchester.ac.uk/ws/files/61849807/FULL_TEXT.PDF

Formic acid and nitric acid have been found to contribute to aerosol formation and are key components of acidity in the troposphere. Tropospheric measurements of these species are often limited, resulting in major uncertainties when assessing their effects on the climate. Current global chemistry-transport models significantly under-predict formic acid concentrations, particularly in the mid-to-high latitudes of the Northern Hemisphere. Furthermore, large discrepancies exist in the role played by dinitrogen pentoxide on nitric acid production between two recently documented models assessing the global nitric acid budget. In order to accurately constrain the budget of these acids in the mid-to-high latitudes of the Northern Hemisphere, it is crucial that these uncertainties are addressed. In this work, airborne measurements of formic acid, nitric acid and dinitrogen pentoxide are presented from across different regions of the Northern Hemisphere to investigate direct and indirect sources contributing to the formic acid and nitric acid regional budgets. Measurements were collected using a Chemical Ionisation Mass Spectrometer (CIMS) fitted to the Facility for Atmospheric Airborne Measurements (FAAM) BAe-146 aircraft. Formic acid measurements within the European Arctic during March and July 2012 would indicate ocean sources dominate over terrestrial sources irrespective of seasonality. CH2I2 photolysis and oxidation was hypothesised as a marine source of formic acid. Modelled estimates would indicate the CH2I2 reaction route may represent a significant summer marine source of formic acid within the Fenno-Scandinavian Arctic. Additionally, low altitude aircraft measurements taken within the Fenno-Scandinavian Arctic over regions occupied by wetlands in August 2013 were used to calculate a formic acid surface flux. Results would suggest formic acid emission from wetlands may represent up to 37 times greater than its globally inferred estimate. A flux measurement conducted over a comparable region in September 2013 ...