Assessing the Ability of Nitrogen Isotopes to Distinguish Ammonia Sources Affecting Rocky Mountain National Park

Extensive evidence has shown that Rocky Mountain National Park (RMNP) has undergone ecosystem changes due to excessive nitrogen (N) deposition. Previously, the Rocky Mountain Atmospheric Nitrogen and Sulfur (RoMANS) study was conducted to identify the species of N that deposit in RMNP. Results from the RoMANS study showed that reduced N contributions from within Colorado were 45% and 36% for the spring and summer, respectively. There is still much uncertainty as to how much each source within Colorado contributes to ammonia deposition in RMNP. The major goal of this study is to determine whether the isotopic signature of nitrogen can be used as a tracer for ammonia released from sources within Colorado into RMNP. Samples were deployed in May of 2011. All samples were collected using passive samplers, Radiellos, deployed for 2 week and/or monthly integrations periods. Samples were collected from, but not limited to, confined animal feeding operations, dairies, wastewater reclamation, mobile sources, RMNP, etc. Sample locations were chosen based on the location in comparison to RMNP and the availability of meteorological data. The collected ammonia was analyzed using Ion Chromatography, and then diffused for isotopic analysis. Results will be discussed in terms of differences among ammonia emitters and in comparison to RMNP. Studies are also being conducted to investigate the isotopic values of ammonia lost from RMNP soils and wet deposition collected in RMNP.