Fire-derived organic matter retains ammonia through covalent bond formation.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 30737387.
- Also identified by DOI 10.1038/s41467-019-08401-z and PMC identifier 6368596.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Fire-derived organic matter, often referred to as pyrogenic organic matter (PyOM), is present in the Earth's soil, sediment, atmosphere, and water. We investigated interactions of PyOM with ammonia (NH<sub>3</sub>) gas, which makes up much of the Earth's reactive nitrogen (N) pool. Here we show that PyOM's NH<sub>3</sub> retention capacity under ambient conditions can exceed 180 mg N g<sup>-1</sup> PyOM-carbon, resulting in a material with a higher N content than any unprocessed plant material and most animal manures. As PyOM is weathered, NH<sub>3</sub> retention increases sixfold, with more than half of the N retained through chemisorption rather than physisorption. Near-edge X-ray absorption fine structure and nuclear magnetic resonance spectroscopy reveal that a variety of covalent bonds form between NH<sub>3</sub>-N and PyOM, more than 10% of which contained heterocyclic structures. We estimate that through these mechanisms soil PyOM stocks could retain more than 600-fold annual NH<sub>3</sub> emissions from agriculture, exerting an important control on global N cycling.