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Nr Deposition Science Needs White Paper

NADP’s Total Deposition Science Committee (TDep) has released a white paper, Science needs for continued development of total nitrogen deposition budgets in the United States.

Critical load frameworks for limiting ecosystem exposure to nutrients and acidity require accurate and complete deposition budgets of reactive nitrogen (Nr). Determination of the amount of deposition in excess of the ecosystem critical load (i.e. “exceedance”) requires an estimate of total deposition, which is typically derived from gridded chemical transport models or a combination of measurements and models. While much progress has been made in developing total Nr deposition budgets for the U.S. over the past several years, improvement in the completeness, accuracy, and spatial representativeness of total Nr deposition budgets remains limited by key data and knowledge gaps. This report details the state of the science of Nr deposition budgets in the U.S. and identifies research needed to improve deposition budgets to support critical loads and the secondary National Ambient Air Quality Standards. The document is intended to serve as a roadmap for research activities but also to provide program and natural resource managers, policy makers and scientists with an understanding of the need for complete and accurate Nr deposition budgets to protect ecosystem health and the linkages between the underlying policy-relevant science questions and the knowledge and data gaps needed to improve Nr deposition budgets.