U.S. Department of Defense


Date of this Version



Geophysical Research Letters, 1987


U.S. Government work


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.