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‘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.
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What is ConAN?
Nitrogen in fused aromatic (pyrrole/pyridine-like) rings—the most stable soil organic N form discussed here.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
How was ConAN historically interpreted?
As combustion-derived ‘black nitrogen’ from fires and fossil-fuel burning.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
What field system did they use?
Pine deck boards with iron nails, ~12 years outdoors in Norfolk, Virginia.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
Why do iron nails matter?
Corrosion drives Fenton-like hydroxyl radicals that oxidize biomass.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
Did ConAN form without fire?
Yes—oxidation accumulated ConAC and ConAN; they are not equivalent to BC/BN.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
What happened to δ15N?
15N enrichment like post-fire soils, but without combustion.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
Pyrogenic ConAN flux estimate?
2–17 Tg ConAN yr−1.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
Nonpyrogenic ConAN flux estimate?
3–63 Tg ConAN yr−1.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
How do those fluxes compare?
Nonpyrogenic estimate is comparable to (or larger than) the pyrogenic flux.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
Share of soil organic N that can be ConAN?
Current estimates 10–35%.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified
Why is the global number uncertain?
No direct ConAN method like BPCA for ConAC; they used a back-of-envelope calculation.
Source: Nonpyrogenic "Black" Nitrogen Likely Plays a Major Yet Underrecognized Role in the Global Nitrogen Cycle · DOI · quote verified