Baseline Acidity of Percipitation at the South Pole during the Last Two Millennia

Authors

J H. Cragin, U.S. Army Cold Regions Research and Engineering Laboratory
M B. Giovinetto, University of Calgary
A J. Gow, U.S. Army Cold Regions Research and Engineering Laboratory

Date of this Version

1987

Citation

Geophysical Research Letters, 1987

Comments

U.S. Government work

Abstract

Measurements of meltwater pH from annual layers of South Pole firn and ice samples ranging in age from 40 to 2000 years B .P. show that precipitation at this remote site has a higher natural acidity than that expected from atmospheric equilibrium with CO2. The average pH of deaerated (C O2-free)samples was 5 .64 + 0.08, while a irequilibrated samples averaged5 .37 + 0.08, a pH that is about a factor of two more acidic than the expected background pH of 5.65. The observed" excess" acidity can be accounted for by SO1-and NO7 levels in the samples originating from non-anthropogenic H2 SO4 and HNO3. Because of the presence of these naturally occurring acids in South Pole precipitation a pH of 5.4 is considered a more representative baseline reference pH for acid precipitation studies.