The origin of nitrogen deposited in Rocky Mountain NP during the ROMANS Study: A weight of evidence analysis and representativeness of results

The Rocky Mountain Atmospheric Nitrogen and Sulfur (RoMANS) study was conducted to improve our understanding of dry and wet deposition of all nitrogen (N) and sulfur species to Rocky Mountain National Park (RMNP), their sources, and transport pathways. As part of this study, intensive monitoring campaigns were conducted for five weeks in spring and five weeks in summer 2006, when ambient concentrations and deposition rates are typically high. These data were then used to assess the contributions of source regions within and outside of Colorado to RMNP N deposition for each season. Apportioning N deposition in RNMP is challenging, and typical chemical transport models do not have sufficient accuracy making their results questionable. Therefore, a weight of evidence approach, comparing and contrasting results from multiple analyses, was used to conduct the apportionment of ambient and deposited N species. This was done through a multistep process, starting from a simple qualitative spatial data analysis to a final quantitative hybrid-receptor modeling technique that incorporated chemical transport modeling results and measured data. Each successive analysis built on the previous method, incorporating new data and/or more sophisticated statistical methods to refine the results. This process allowed for a better understanding of the effects of the additional data and statistical methods, providing insights into the quality of the final results. The weight of evidence approach and results will be presented. In addition, representativeness of the RoMANS results to other times of the year and other years will be