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Baseline acidity of precipitation at the South Pole during the last two millennia
Author(s) -
Cragin J. H.,
Giovinetto M. B.,
Gow A. J.
Publication year - 1987
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl014i008p00789
Subject(s) - precipitation , meltwater , firn , baseline (sea) , environmental science , acid rain , environmental chemistry , atmospheric sciences , mineralogy , chemistry , geology , glacier , oceanography , meteorology , geography , geomorphology , organic chemistry
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 CO 2 . The average pH of deaerated (CO 2 ‐free) samples was 5.64 ± 0.08, while air‐equilibrated samples averaged 5.37 ± 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 SO 4 2− and NO 3 − levels in the samples originating from non‐anthropogenic H 2 SO 4 and HNO 3 . 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.