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Changes in the Output of Ions from a Watershed as a Result of the Acidification of Precipitation
Author(s) -
Lewis William M.,
Grant Michael C.
Publication year - 1979
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1936955
Subject(s) - bicarbonate , chemistry , nitrate , precipitation , inorganic chemistry , sulfate , phosphate , ammonia , watershed , environmental chemistry , nitrogen , potassium , biochemistry , machine learning , meteorology , computer science , physics , organic chemistry
The average hydrogen ion input to a mountain watershed in Colorado increased by a total of 0.142 meq.m — 2 . wk— 1 over a 150—wk study period. Over the same period, the output of bicarbonate ions from the watershed, as determined by weekly stream chemistry measurements, decreased by 0.162 meq.m— 2 . wk — 1 after correction for a slight decrease in bicarbonate input. The output of sulfate, nitrate, ammonia, and dissolved organic matter all increased significantly. These increases are not enough to constitute a major change in watershed mass balance, but the nitrate and ammonia changes in particular could be important to the stream biota because of the low background levels of inorganic nitrogen. Output of calcium, magnesium, sodium, potassium, phosphate, and hydrogen ions showed no significant individual trends, but there is some evidence of a decrease in total cation output. It is postulated that essentially all of the hydrogenon ions entering in the form of acid precipitation combine with bicarbonate ions in the soil, and this accounts for the reduction in bicarbonate output of the watershed. This hypothesis is well supported by the match between rates of change in hydrogen ion input and bicarbonate output. Since carbonates are not present in the soil, a combination of acid with bicarbonate would lead to the production and release of free CO 2 in amounts equivalent to the acid which is neutralized. Acidification of precipitation thus appears to cause a stoichiometric reduction in bicarbonate output and smaller but potentially important shifts in output of other ions as well.