Nitrogen is an essential element to all life and cascades through biogeochemical cycles as reactive nitrogen (Nr) in many different chemical forms.  The atmosphere is an important reservoir of Nr, where significant photochemical reactions and partitioning from gaseous to particulate and dissolved phases takes place. The chemical form of Nr dictates the form and degree to which Nr is deposited to the landscape, or re-emitted to the atmosphere. The exchange of Nr between the atmosphere and the surface is important, given the role of excess Nr as an environmental pollutant.

NADP has played an integral role in better understanding atmospheric cycling of Nr and in the exchange between the atmosphere and earth’s surface, including biosphere, lithosphere, and hydrosphere.

Here we present highlights from an updated NADP nitrogen brochure entitled Nitrogen from the Atmosphere, which updates and replaces the former publication, Nitrogen in Rain, which was originally developed ~2000. The brochure is designed for a general audience in order to better communicate the issues related to atmospheric Nr, its measurement, and impact on the environment.

Some important points presented in this brochure include:

• The many forms of Nr and their sources
• The relative importance of atmospheric emissions of NOx and NH₃ which contribute to Nr in the landscape
• Effects of nitrogen on forests, freshwaters and estuarine systems, and a case study of how nitrogen impacts Chesapeake Bay, as well as mitigation efforts to reduce negative impacts.
• Critical loads for nitrogen as a policy tool to reduce negative impacts of nitrogen deposition
• Measurement of Nr deposition by NADP and CASTNET to better quantify trends and rates of N deposition by various species (e.g. wet and dry NO₃^- and NH₄⁺, NH₃)
• The role of agriculture in managing nitrogen inputs
• Quantification of total atmospheric N deposition using both measured and modeled estimates for the USA