||Illinois State Water Survey Div., Champaign.; Illinois Univ. at Urbana-Champaign.; Department of Agriculture, Washington, DC.; Department of the Interior, Washington, DC.; Environmental Protection Agency, Washington, DC.
This report presents data summaries from three networks. Contour maps present NTN data. Concentration and deposition maps present MDN data. The bar graphs present AIRMoN concentrations over time. The NTN maps portray spatial variability in the concentration and deposition of selected acids, nutrients, and base cations on regional and national scales. Only sites that meet prescribed data completeness criteria are included. In 1998, 161 sites met these criteria. Annual concentration or deposition values are printed next to each site. The concentrations are volume-weighted averages. The MDN maps show the concentration and deposition of total mercury in precipitation. Only sites meeting prescribed data completeness criteria are included. In 1998, 30 sites met these criteria. Annual concentration or deposition is printed next to each site. The concentrations are volume-weighted averages. Bar graphs show average seasonal nitrate (NO3-) and ammonium (NH4+) deposition for the nine AIRMoN sites active at the end of 1998. These are 1993-1998 averages at all sites except Maryland (MD15) and Florida (FL18), which joined AIRMoN in late 1995 and 1996, respectively. The averaging period for these two sites is 1996-1998 (MD15) and 1997-1998 (FL18). Seasons are winter, (December-February), spring (March-May), summer (June-August), and fall (September-November). Not shown is the AIRMoN site at South Lido Key, near Sarasota, Florida, which began its operations in September 1998. Average seasonal depositions were calculated by computing the seasonal weighted-average concentrations of nitrate and ammonium then multiplying these concentrations by the average seasonal precipitation amounts. Depositions in the bar graphs are in units of equivalents per hectare. The bar graphs show how nitrogen from nitrate and ammonium and the sum of these forms of inorganic nitrogen vary by season and among sites.