0 1990, by the American Society of Limnology and Oceanography, Inc. Alkalinities of Maine lakes: Are they really changing?

• Main Author: Rober T E. Staufferl
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: cent #alkalinity measurements (e.g. Norton; Gorham; Kramer; Carbonic acid
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.541.1145; http://www.aslo.org/lo/toc/vol_35/issue_6/1238.pdf

Alk.alinity changes between 1938-1944 and 1985 were evaluated for Maine lakes (zmaX 2 15 m) in granitic watersheds. Modern (late summer 1985) Gran alkalinities for the hypolimnion were compared with historical alkalinities computed using: tog,JHCO,-1 = PH(T)- PK’,( ~ + log[HXO,*l where pH(T) is the historic reported calorimetric pH at each hypolimnctic sampling depth and temperature, pK’,(T) the temperature-dependent negative logarithm of the first dissociation con-s’tant for carbonic acid, and H,CO, * represents initial CO, at last spring overturn, plus the change in CO, associated with the hypolimnetic oxygen deficit developed over summer (estimated from the historic oxygen data). With modern data for representative Maine lakes and historical (1932) data on dissolved gases reported for northern Wisconsin lakes, the apparent respiratory quotient relating ACO, to A02 = 0.92. The above model yields alkalinity estimates with a relative root-mean-square (RMS) error of- 15%. The alkalinities of the Maine lakes have increased by 15-50 peq liter- ’ (> 30%) since the original surveys. Lake alkalization is not the result of differences in antecedent weather, since abnormally dry weather predating 1942 would have acted to elevate alkalinities. Environmental research in northern Eu-rope and eastern North America generally supports.the hypothesis that the long-term deposition of excess sulfuric acid on geo-logically vulnerable watersheds results in partial losses of surf&ce-water alkalinity and, in extreme cases, to severe regional lake and stream acidification (Gorham 1984). The reconstruction of historical changes in lake alkalinity in Maine has proved difficult be-cause, with few exceptions (e.g. Moosehead Lake, summer 1944), the extensive pio-neering lake surveys of Cooper ( 19 39- 1946) made no measurements of alkalinity. In ret-rospect, this omission is riot grave, because biased data would likely have resulted in the titrations of Maine’s dilute waters to the standard methyl-orange endpoint (Kramer