Using delta15N values to characterise the nitrogen nutrient pathways from intensive animal units

Area of Science:

• Environmental Science
• Isotope Geochemistry
• Biogeochemistry

Background:

• Foliar delta15N values in bryophytes have shown similarities to pollutant source signatures.
• Understanding isotopic fractionation is crucial for interpreting these signatures.

Purpose of the Study:

• To investigate the mechanisms of isotopic fractionation in nitrogen transformations.
• To examine the utility of delta15N values as indicators of atmospheric ammonia (NH3) pollution.
• To characterize fractionation effects near emission sources.

Main Methods:

• Field measurements of delta15N in atmospheric NH3, throughfall, vegetation, and soil.
• Analysis of fractionation effects associated with nitrogen transformations.
• Atmospheric dispersion modeling using UK-ADMS for delta15NH3 emissions.

Main Results:

• Negative shifts in delta15N signatures were observed downwind of an agricultural NH3 source.
• Dispersion patterns of delta15NH3 mirrored NH3 concentration data.
• Fractionation effects were characterized in various environmental compartments.

Conclusions:

• Delta15N values in bryophytes can reflect NH3 pollution, but fractionation processes complicate interpretation.
• The study highlights issues in using delta15N as a sole pollution indicator.
• Integrated approaches using dispersion models and direct measurements are valuable.