Formation of Char-Like, Fused-Ring Aromatic Structures from a Nonpyrogenic Pathway during Decomposition of Wheat Straw

Abstract

Fused-ring aromatics, important skeletal components of black carbon (BC), contribute to long-term carbon (C) sequestration in nature. They have previously been thought to be primarily formed by incomplete combustion of organic materials, whereas the nonpyrogenic origins are negligible. Using advanced solid-state 13C nuclear magnetic resonance (NMR), including recoupled long-range C–H dipolar dephasing, exchange with protonated and nonprotonated spectral editing (EXPANSE), and dipolar-dephased double-quantum/single-quantum (DQ/SQ) spectroscopy, we for the first time identify fused-ring aromatics that formed during the decomposition of wheat (Triticum sp.) straw in soil under aerobic, but not anaerobic conditions. The observed formation of polyaromatic units as plant litter decomposes provides direct evidence for humification. Moreover, the estimation of the annual flux of such nonpyrogenic BC could be equivalent to 3–12% of pyrogenic BC added to soils from all other sources. Our findings significantly extend the understanding of potential sources of fused-ring aromatic C and BC in soils as well as the global C cycle.

Molecular-Level Study of the Photo-Oxidation of Aqueous-Phase Guaiacyl Acetone in the Presence of 3C*: Formation of Brown Carbon Products

“…Photo-oxidation reactions ultimately lead to the formation of CO 2 , the most oxidized form of carbon. , However, dissolved oxygen might be limited in larger aqueous volumes such as surface and terrestrial water, especially after Norrish photoreactions have occurred. Photoreactions in the oxygen-deficient aqueous phase have been shown to undergo a nonoxidative degradation pathway, which often forms pyrolytic-like condensed aromatic products, and this reaction pathway has been observed in terrestrial lignin-derived organic matter . These products are often strongly light-absorbing due to the conjugated double bonds.…”

Nonpyrogenic charring of Late Pleistocene large mammal remains in northeastern Russia

“…The possibility of black carbon forming in the organic matter by nonpyrogenic pathways has been experimentally proven to occur in soil under aerobic conditions (Chen et al . 2020). Similar features are observed as a result of oxidation of organic matter during prolonged intervals of degradation (Semenov et al .…”

Aspergillus nigerEnhances Organic and Inorganic Phosphorus Release from Wheat Straw by Secretion of Degrading Enzymes and Oxalic Acid

“…6,7 Long-term straw returning increases nitrogen (N), phosphorus (P), and potassium (K) contents in the soil, reducing the dependence on fertilizers. 8 In terms of P, straw returning not only reduces P sorption in soil but also increases inorganic and organic P contents. 9 It is estimated that the globally accumulative amounts of straw are 1.62 × 103 Gg, corresponding to 11.5% of P fertilizers between 2000 and 2017 years.…”

“…Straw returning has been widely practiced in agricultural production systems to alleviate soil degradation and maintain soil fertility. , Long-term straw returning increases nitrogen (N), phosphorus (P), and potassium (K) contents in the soil, reducing the dependence on fertilizers . In terms of P, straw returning not only reduces P sorption in soil but also increases inorganic and organic P contents .…”