Measurements of Nitric and Pernitric Acids at the South Pole during ISCAT 2000
Abstract
Pernitric acid (HO2NO2) and nitric acid (HNO3) levels were measured with a chemical ionization mass spectrometer 10 m above the snow in December 2000 at the South Pole. (ISCAT 2000). The average mixing ratios of HO2NO2and HNO3 were observed to be 25 and 22 pptv, respectively. Simple steady state calculations constrained by measurements of OH, HO2, j values and inferred NO2 demonstrate that both species have relatively short lifetimes of 1- 10 hours in this environment. The observed nitric acid levels were consistent with an average dry deposition lifetime of 3.5 hours and no evidence was found for a flux of nitric acid from the snow. The lifetime of pernitric acid was largely controlled by dry deposition, with thermal decomposition becoming increasingly important at warmer temperatures. The pernitric acid data also indicate that the thermal decomposition rate constant for HO2NO2 in the temperature range of 244 to 251 K is much less uncertain than indicated in the literature. One consequence of pernitric acid deposition to the snow surface is that it is an important sink for both NOx and HOx. Another is that the photochemistry of HO2NO2 in the Antarctic snowpack may be a NOx source in addition to nitrate photolysis. The formation of reasonably atmospheric high levels of pernitric acid may be a unique feature of SP relative to other warmer polar sites such as Summit, Greenland.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.A12E..02H
- Keywords:
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- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry