Improving Reactive Nitrogen Deposition Budgets
by John T. Walker
Accurate and complete budgets of reactive nitrogen (Nr) deposition are needed for ecosystem risk assessments, including the development of critical loads for nutrients and acidity and review of the secondary U.S. National Ambient Air Quality Standards. Members of the National Atmospheric Deposition Program Total Deposition Science Committee (NADP/TDep), along with collaborators from federal agencies and academia, recently completed a review of the state of the science of Nr deposition budgets in the United States.
The report highlights that while much progress has been made in improving deposition budgets over the past decade, further improvements remain limited by important data and knowledge gaps. The report is categorized into specific areas of deposition research where these gaps are identified and briefly discussed in terms of their importance and, where applicable, potential research paths are identified.
In this issue of EM, we summarize several overarching examples of policy-relevant research needed to better understand emissions, air concentrations, and deposition of Nr, and to improve models and measurement-model fusion methods for estimating total and speciated Nr deposition for ecosystem assessments.