Susceptibility of northern Minnesota lakes to acid deposition impacts

Journal Article · · Journal of the Minnesota Academy of Science; (USA)

OSTI ID:5630216

Twaroski, C J; Thornton, J D; Strassman, R L; Brezonik, P L

Lake chemistry surveys indicate a large number of lakes with acid neutralizing capability (ANC) below 200 microeq/L occur in northeast Minnesota where shallow soils over bedrock and exposed rock outcrops predominate, and in moraine areas having rolling to steep topography in north-central and east-central Minnesota. Relationships found between ANC and bedrock geology, and between ANC and landform and soils, provided the basis for mapping the distribution of low ANC surface waters in Minnesota. Empirical and process models used to evaluate the actual susceptibility of low ANC lakes in the Upper Midwest to acid deposition impacts indicated a precipitation pH of 4.6-4.7 is a threshold level for lake acidification. Modeling also indicated that lakes with ANC < 50 microeq/L are very susceptible to acidic inputs and are considered critically sensitive. At present, no culturally acidified lakes have been found in northeast Minnesota, although acid lakes have been found Wisconsin and the Upper Peninsula of Michigan. The Hovland-Grand Marais-Isabella area of northeast Minnesota currently receives precipitation with an annual average pH of 4.7. This area is considered to be on the edge of the effects area and is a major focus of the Minnesota Pollution Control Agency's long-term research and monitoring program on lake and stream response to annual and episodic inputs of acids. 35 refs., 7 figs.

• OSTI ID: 5630216
• Journal Information: Journal of the Minnesota Academy of Science; (USA), Journal Name: Journal of the Minnesota Academy of Science; (USA) Vol. 55:1; ISSN JMNAA; ISSN 0026-539X
• Country of Publication: United States
• Language: English

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ACID NEUTRALIZING CAPACITY
ACID RAIN
ACIDIFICATION
ATMOSPHERIC PRECIPITATIONS
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PH VALUE
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SURFACE WATERS
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WATER CHEMISTRY
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