Contribution of Animal Feeding Operations and Synthetic Fertilizers to Ammonia Deposition in Rocky Mountain National Park

To ensure that agricultural producers are being treated fairly with respect to how much they contribute to ammonia deposition in Rocky Mountain National Park.


Justification

Ammonia (NH₃) is a serious concern as both a human health and environmental issue and has recently been targeted by Colorado as a primary contributor to atmospheric and ecosystem changes in Rocky Mountain National Park (RMNP). Ecological ramifications, including increased forest and grassland productivity, eutrophication and acidification of fresh waters, hypoxia (low oxygen levels in water), and loss of biodiversity, have been documented in terrestrial, freshwater, and coastal ecosystems worldwide. For NH₃ the estimated global emission for 1990 is about 54 million ton N year^-1. The major sources identified include excreta from domestic animals and wild animals, use of synthetic N fertilizers, oceans and biomass burning. The Colorado Department of Public Health and Environment estimates, that 60% of the NH₃ deposition in RMNP comes from agricultural activities with 40% from animal feeding operations (AFOs) and 20% from fertilizer. However, to ensure that these estimates are correct, one must verify these estimates with factual data. This becomes especially important if future federal regulations will require livestock producers or fertilizer companies to be financially responsible for NH₃-related ecosystem damage, in order to prevent a poor model estimate from resulting in an unrealistic financial burden. One of the most promising ways to track nitrogen (N) to its original source is via N isotopic signatures (ä¹⁵N) since the ratio between the ¹⁴N and ¹⁵N isotopes will be influenced by its source. For instance, manure/sewage often has a high positive ä¹⁵N value due to the fact that bacteria preferentially utilize ¹⁴N over ¹⁵N. In contrast, artificial fertilizers typically have a much lighter isotopic signature since it is manufactured by the fixation of atmospheric N₂, which has a ä¹⁵N value of 0%, and during the process of fixation the ¹⁴N is preferentially incorporated into the fertilizer resulting in a slightly lower than atmospheric (negative) isotopic signature. In general, agricultural practices produce ä¹⁵NH₃ values that are significantly different from those of non-agricultural sources. The N isotopic signature approach has been used successfully in the past to track nitrate sources, but very little research has been done on isotopic signatures of ammonia.


Objectives

To ensure that agricultural producers are being treated fairly with respect to how much they contribute to ammonia deposition in Rocky Mountain National Park, this proposal will focus on the following objectives:

1. Determine the major sources of NH₃ deposition in RMNP based on nitrogen isotopic signatures (ä¹⁵N) of different NH₃ sources (i.e., agricultural, natural and industrial sources).
2. Quantify the relative contribution of NH₃ to RMNP from animal feeding operations, synthetic fertilizers, and other sources.

Methodology
1.
Atmospheric NH₃ (gas and particle phase) will be sampled using a denuder/filter-pack sampling system. Acid coated diffusion denuders will be used to collect gas phase ammonia. A downstream Teflon filter will collect particulate ammonium. The samplers will be placed at all the major suspected sources of ammonia emission including livestock production facilities, dairies, recent fertilizer applications (agricultural and residential), native soils, wildlife, traffic sources, and human emissions (perspiration, breath). Following the detailed analysis of isotope ratios from these sources by isotope ratio mass spectrometry, we will analyze isotope ratios in the N deposition in Rocky Mountain National Park in order to test the consistency of results obtained by other methods (e.g., atmospheric models).

EXPECTED RESULTS: More accurate NH₃ deposition data in RMNP showing the true NH₃ contribution from livestock and synthetic fertilizers.