Hydrogen ion input to the Hubbard Brook Experimental Forest, New Hampshire, during the last decade

Abstract

Being downwind of eastern and midwestern industrial centers, the Hubbard Brook Experimental Forest offers a prime location to monitor long-term trends in atmospheric chemistry. Continuous measurements of precipitation chemistry during the last 10 years provide a measure of recent changes in precipitation inputs of hydrogen ion. The weighted average pH of precipitation during 1964-65 to 1973-74 was 4.14, with a minimum annual value of 4.03 in 1970-71 and a maximum annual value of 4.21 in 1973-74. The sum of all cations except hydrogen ion decreased from 51 μeq/l in 1964-65 to 23 μeq/l in 1973-74 providing a significant drop in neutralizing capacity during this period. Based upon regression analysis, the input in equivalents of hydrogen ion and nitrate increased by 1.4-fold and 2.3-fold respectively, from 1964-65 to 1973-74. Input of all other ions either decreased or showed no trend. Based upon a stoichiometric formation process in which a sea-salt, anionic component is subtracted from the total anions in precipitation, SO₄^-2 contribution to acidity dropped from 83% to 66%, whereas NO₃^-1 increased from 15% to 30% during 1964-65 to 1973-74. The increased annual input of hydrogen ion at Hubbard Brook during the past 10 years is highly correlated with the increased input of nitrate in precipitation.

Parent Publication

• Proceedings of the first international symposium on acid precipitation and the forest ecosystem

Citation

Likens, Gene E.; Bormann, F. Herbert; Eaton, John S.; Pierce, Robert S.; Johnson, Noye M. 1976. Hydrogen ion input to the Hubbard Brook Experimental Forest, New Hampshire, during the last decade. In: Dochinger, L. S.; Seliga, T. A., eds. Proceedings of the first international symposium on acid precipitation and the forest ecosystem; Gen. Tech. Rep. NE-23. Upper Darby, PA: U.S. Department of Agriculture, Forest Service, Northeastern Forest Experiment Station. 397-407