03066naa a2200301 a 450000100080000000500110000800800410001902400570006010000180011724502070013526000090034230000100035152020590036165000160242065000360243665000240247265300190249665300090251565300190252465300260254370000190256970000200258870000260260870000230263470000240265770000190268177300640270021407102023-11-08       2022    bl uuuu     u00u1 u    #d7 ahttps://doi.org/10.1016/j.scitotenv.2021.1526052DOI1 aTADINI, A. M.  aStructural characterization using 2D NMR spectroscopy andTMAH-GC × GC-MSbapplication to humic acids from soils of anintegrated agricultural system and an Atlantic native forest.h[electronic resource]  c2022  a14 p.  aUnderstanding the chemical make-up of soils and their structure is critical for constraining the role of soil organic mat-ter (SOM) into the global biogeochemical cycles, as well as to understand the capability of SOM to sequester carbonand mitigate greenhouse gas emissions. Here, we use two-dimensional1H-13C heteronuclear single quantum coher-encenuclear magnetic resonance (2D1H-13C HSQC NMR) spectroscopy to structurally characterize the most refractorycomponent of SOM, the humic acid (HA). The observations from 2D1H-13C HSQC NMR were coupled with lignin phe-nol and fatty acid measurements using tetramethylammonium hydroxide (TMAH) thermochemolysis?two-dimensional gas chromatography?mass spectrometry (TMAH-GC × GC-MS). We studied humic acids extractedfrom an integrated Crop?Livestock?Forest System (CLFS) agricultural area and an undisturbed Atlantic Native Forest(NF) area. We evaluated soils from two different depths: the topsoil (0?20 cm) and subsoil (60?100 cm) layers, andreveal the presence of oxidized ligninaceous phenols as we had previously hypothesized. Collectively, our results indi-cate that there are significant oxidative processes with increasing soil depth which are more pronounced in the CLFSrelative to the NF area. Degradation of stearic acid with increasing depth in the CLFS soils indicated that the CLFS ismore microbiologically active than NF. Therefore, CLFS is less biochemically stable than we originally perceived.The enhanced bio-reactivity of CLFS is likely driving the enhanced carbon sequestration in the CLFS soils. This is perhaps dueto the diversityof biomass remnants available at the CLFS soil rhizosphere which allowsfor more differenttypes of biomass to be sequestered as oxidized ligninaceous phenols. Our results employing structural characterizationwith 2D1H-13C HSQC NMR and TMAH-GC × GC-MS provide a new layer of knowledge about the practice of inte-grated agricultural systems and allow us to understand the structure and fate of sequestered carbon in soils from dif-ferent soil environments.  aHumic acids  aIntegrated agricultural systems  aSoil organic matter  a2D1H 13CHSQCNM  aILPF  aLignin phenols  aTMAH thermochemolysis1 aGORANOV, A. I.1 aMARTIN NETO, L.1 aBERNARDI, A. C. de C.1 aOLIVEIRA, P. P. A.1 aPEZZOPANE, J. R. M.1 aHATCHER, P. G.  tScience of The Total Environmentgv.815, apr. 2022, 152605.