Location: Hydrology and Remote Sensing Laboratory
Title: Characterizing the isotopic composition of atmospheric ammonia emission sources using passive samplers and a combined oxidation-bacterial denitrifier approach Authors
Submitted to: Rapid Communications in Mass Spectrometry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 2013
Publication Date: October 30, 2013
Citation: Felix, J.D., Elliott, E.M., Gish, T.J., McConnell, L.L., Shaw, S.L. 2013. Characterizing the isotopic composition of atmospheric ammonia emission sources using passive samplers and a combined oxidation-bacterial denitrifier approach. Rapid Communications in Mass Spectrometry. 27:2239-2246. Interpretive Summary: Ammonia is a gas that is released from agricultural, industrial and natural sources. Ammonia gas can be deposited to waterways and serves as a source of nitrogen. Too much ammonia deposition can cause water quality to decline. The nitrogen in ammonia is made up of two different isotopes. The ratio of these two isotopes can serve as a signature for different sources of ammonia. This paper describes an improved analytical method to measure ammonia concentrations in air and to measure the isotope ratio. The method uses passive air samplers that don’t require electricity followed by an analytical procedure that requires very little mass of nitrogen to determine the isotope ratio. This new approach will allow scientists to collect samples from remote areas and increases their ability to measure the isotope ratio of samples with very low concentrations. Knowledge of the isotope ratio of ammonia in different locations will provide important information on the sources of ammonia to sensitive waterways.
Technical Abstract: Ammonia (NH3) emissions are a substantial source of nitrogen pollution to sensitive terrestrial, aquatic, and marine ecosystems. Dependable quantification of NH3 sources is of growing importance due to recently observed increases in ammonium (NH4+) deposition rates that are directly proportional to NH3 emissions. Determination of the nitrogen isotopic composition of NH3 (d15N-NH3) can aid in the quantification of NH3 emission sources. To build a more comprehensive inventory of the isotopic composition of NH3 sources, we report d15N- NH3 values of emissions collected from various livestock operations, power plants, vehicles, and fertilized cornfields. To analyze these NH3 emissions, we developed a method for the isotopic analysis of low concentration NH4+ samples (std. dev. + 0.7 ‰) that couples bromate oxidation of NH4+ to nitrite (NO2-) wherein NO2- is subsequently analyzed using the microbial denitrifier method for d15N. This approach reduces required amount of sample NH4+ needed for conventional d15N-NH4+ analysis via combustion by 50 times. The method is also less time intensive and eliminates the use of toxic chemicals used in a prior method for analysis of low concentration samples. Using this approach, the compiled d15N-NH3 source inventory reveals that NH3 emitted from volatilized livestock waste and fertilizer (-56 to -23 ‰) has relatively low d15N values, allowing it to be differentiated from fossil fuel sources including vehicle exhaust and coal combustion characterized by relatively high d15N values (-15 to +2 ‰).