These animations display the National Trends Network (NTN) concentration and deposition maps of sulfate, nitrate, and ammonium and deposition maps of total inorganic nitrogen from nitrate and ammonium beginning in 1985. You can view two versions of the animations. The Flash version requires that Macromedia Flash Player be installed on your computer. You can download this free software by clicking on the icon below. The PowerPoint version can be downloaded and viewed by using PowerPoint, a software product of Microsoft, Inc.

Each frame represents a three-year precipitation-weighted mean concentration or three-year mean annual deposition. For example, the 1985 concentration map displays the precipitation-weighted mean concentration for 1984 - 1986. To maintain consistency throughout the animation, a subset of NTN sites that operated for the entire period was used. At least three factors are at work changing the spatial patterns from year to year and over the period of record: emissions changes, changes in weather patterns, and chemical changes in the airborne pollutants that are removed by precipitation.

If you intend on reprinting any of these maps for use in a publication, please read our Use Conditions.