Date of this Version
Geophysical Research Letters, 1987
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.