Atmospheric loading of phosphorus and other chemicals to Lake Michigan

TitleAtmospheric loading of phosphorus and other chemicals to Lake Michigan
Publication TypeJournal Article
Year of Publication1977
AuthorsEisenreich S.J, Emmling P.J, Beeton A.M
JournalJournal of Great Lakes Research

Bulk precipitation was collected on a monthly basis in the Lake Michigan basin for 18 months during 1975-1976 to determine atmospheric total phosphorus (TP) loadings to Lake Michigan. The sampling network consisted of bulk collectors at 23 land stations and 2 in-lake buoys located off urban and rural areas. Annual TP loading to Lake Michigan for 1976 based on loading rates of 0.184 and 0.303 ug/cm2/mo for the north and south basins, respectively, was 1690000 kg/year, representing ~ 16% of the total P budget. North and south basins showed different TP loading properties with ~62% depositing in the south basin. Seasonal variations in loading rates showed maxima in late spring and early summer, and minima in winter. In-lake buoy samplers yielded enhanced loading of TP compared to land stations. Wet-only precipitation concentrations for TP average 15% of bulk deposition values. Weighted-average TP concentrations in bulk precipitation were 0.050 and 0.064 mg/l in the north and south basins, respectively. Atmospheric TP loading was closely correlated to Ca and Mg loading, independent of precipitation amount, and exhibited a large dry fall component. Wind-blown soil and re-entrained dust are believed to be the major source of atmospheric phosphorus addition to Lake Michigan.