Additions of Nutrients and Major Ions by the Atmosphere and Tributaries to Nearshore Waters of Northwestern Lake Huron |
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Authors: | B.A. Manny R.W. Owens |
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Affiliation: | U.S. Fish and Wildlife Service, Great Lakes Fishery Laboratory, Ann Arbor, Michigan 48105 |
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Abstract: | Nutrient additions by the atmosphere and six tributaries to nearshore waters of northwestern Lake Huron were measured at weekly intervals from August 1975 to July 1976. The atmosphere contributed 43% of the nitrogen (N) and 10% of the phosphorus (P) that was added during the year. The 1975–76 atmospheric loading rate of total N to this area (11 kg/ha/yr) was one of the highest found to date in the United States. N was conserved more efficiently than P in the tributary drainage basins. Of the N and P that fell annually on the watersheds under study, 2 to 37% of the N and 31 to 84% of the P was carried with runoff to the lake. From a basin where ditching and clear-cutting occurred, water, P, silica (SiO2), N, and sodium were lost at higher rates than from five other basins. Most of the N in bulk atmospheric samples (23%) and tributary waters (56%) was dissolved organic N, a form of N not often measured. |
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Keywords: | Phosphorus nitrogen silica acid rain runoff |
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