‘Black’ nitrogen can form without fire
Twelve-year outdoor oxidation of pine around iron nails produced condensed aromatic nitrogen like ‘black N’, implying non-fire ConAN fluxes (≈3–63 Tg yr−1) comparable to pyrogenic estimates.
Source
Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle
Study at a glance
- Design
- Other — Spectroscopic characterization of 12-year outdoor iron-nail pine oxidation plus global ConAN budget
- N
- Case study of pine deck oxidation; flux estimates are back-of-envelope budgets, not a sample N
- Population
- Condensed aromatic nitrogen formed in outdoor-oxidized pine (Norfolk, VA) and global litter fluxes
- Outcome
- Nonpyrogenic vs pyrogenic ConAN flux estimates to soils
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Authors characterized blackened pine around 12-year-old iron nails (a Fenton-like outdoor oxidation reactor) with elemental, isotopic, spectroscopic, and FT-ICR-MS methods, then combined rates with global litter fluxes for a back-of-envelope ConAN budget.
What they found
Oxidation built ConAC and ConAN without combustion and raised δ15N the way fire does. They estimate pyrogenic ConAN at 2–17 Tg yr−1 versus nonpyrogenic 3–63 Tg yr−1, so much ‘black N’ may not be from wildfire.
The limits
What it doesn't show
A deck-nail reactor is not all soils; the 3–63 Tg range is a first approximation using assumed ConAC formation rates and C/N ratios, not a direct global ConAN inventory.
Key terms
- ConAN
- Condensed aromatic nitrogen in heterocyclic rings (pyrrole/pyridine-like) within polyaromatic structures.
- Black nitrogen (BN)
- ConAN historically assumed to form only in combustion (pyrogenic).
- Nonpyrogenic pathway
- Abiotic oxidation of biomass (e.g., Fenton chemistry) that creates ConAN without fire.
- Fenton oxidation
- Iron-catalyzed production of hydroxyl radicals that oxidize lignin-rich wood.
- δ15N
- Nitrogen isotope ratio; enrichment is often read as a fire signal but arose here from oxidation alone.
Flashcards
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Quiz yourself
ConAN can form via:
Common questions
Does ConAN require fire?
No—oxidation around iron nails formed ConAN without combustion.
Field analog used?
12-year pine deck with iron nails in Norfolk, Virginia.
Nonpyrogenic flux estimate?
About 3–63 Tg ConAN per year to soils.
Isotope caveat?
δ15N enrichment can mimic fire even without burning.
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