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Chemical response of an acid-sensitive headwater stream to snowmelt and storm events: a field study and simulation model

Thesis/Dissertation ·
OSTI ID:5100921
A coordinated field and modelling effort was undertaken on an instrumented watershed within the Hubbard Brook Experimental Forest, New Hampshire to test an acid precipitation neutralization hypothesis. This two-step mechanism states that incident hydrogen ion acidity is quickly exchanged for aluminum (a Lewis acid); this reaction is followed by a slower step in which the aluminum acidity is neutralized by base cations. By this hypothesis, the residence time of the water within the soil system is the primary factor controlling its chemistry. In this study, the residence time hypothesis was translated into the hydrologic problem of hydrograph separation: during a snowmelt or storm event, the stream water is composed of both baseflow (water of long residence time) and event water (water of short residence time). Because some forms of aluminum are toxic to fish, a better understanding of neutralization mechanisms will enable a better assessment of the biological impacts of acid deposition. Fish kills in Scandanavia have been attributed to short-term depressions in pH and the accompanying increase in aluminum. Such observations justify the focus of this study on the chemical response of streams to individual events.
Research Organization:
Cornell Univ., Ithaca, NY (USA)
OSTI ID:
5100921
Country of Publication:
United States
Language:
English