Long-term atmospheric deposition of nitrogen, phosphorus and sulfate in a large oligotrophic lake Bonnie K. Ellis, James A. Craft and Jack A. Stanford Flathead Lake Biological Station, University of Montana, Polson, MT, USA

ABSTRACT We documented significantly increasing trends in atmospheric loading of ammonium (NH4 ) and nitrate/nitrite (NO2/3 ) and decreasing trends in total phosphorus (P) and sulfate (SO4 ) to Flathead Lake, Montana, from 1985 to 2004. Atmospheric loading of NO2/3 and NH4 increased by 48 and 198% and total P and SO4 decreased by 135 and 39%. The molar ratio of TN:TP also increased significantly. Severe air inversions occurred periodically year-round and increased the potential for substantial nutrient loading from even small local sources. Correlations between our loading data and various measures of air quality in the basin (e.g., particulate matter

Long-term atmospheric deposition of nitrogen, phosphorus and sulfate in a large oligotrophic lake.

We documented significantly increasing trends in atmospheric loading of ammonium (NH4) and nitrate/nitrite (NO2/3) and decreasing trends in total phos...
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