02184naa a2200241 a 450000100080000000500110000800800410001902400510006010000190011124501200013026000090025050000250025952014190028465000160170365300170171965300300173665300420176665300210180870000200182970000220184970000210187177300500189221354612021-10-20       2006    bl uuuu     u00u1 u    #d7 ahttps://doi.org/10.1007/s00114-006-0126-x2DOI1 aNOVOTNY, E. H.  aCharacterisation of black carbon-rich samples by 13C solid-state nuclear magnetic resonance.h[electronic resource]  c2006  aShort communication.  aThere are difficulties in quantifying and characterising the organic matter (OM) in soils that contain significant amounts of partially oxidised char or charcoal materials. The anthropogenic black carbon (BC), such as that found in the Terra Preta de Índio soils of the Amazon region, is a good example of the OM that is difficult to analyse in such soils. 13C direct polarisation/magic angle spinning (DP/MAS) at high MAS frequency, 1H-13C cross polarisation (CP)/MAS with total suppression of spinning sidebands (TOSS), and chemical shift anisotropy (CSA) filter nuclear magnetic resonance techniques have been applied successfully for quantifying the different components of OM. However, because pyrogenic materials present strong local magnetic susceptibility heterogeneities, the use of CSA-filter and TOSS make the pulse sequences very sensitive to imperfections in the π pulses. In this study, the DP/MAS pulse sequence was replaced by a CP with a radio frequency ramp-variable amplitude CP (VACP)-VACP/MAS pulse sequence, and composite π pulses were used in the CSA-filter and TOSS pulse sequences. In that way, the component functionalities in a humic acid from a BC soil were successfully determined. The spectrometer time needed was greatly decreased by employing this VACP/MAS technique. This development provides an accurate method for characterising BC-rich samples from different origins.  aHumic acids  aBlack carbon  aChemical shift anisotropy  aInternational Humic Substance Society  aMagic angle spin1 aHAYES, M. H. B.1 aAZEVEDO, E. R. de1 aBONAGAMBA, T. J.  tNaturwissenschaftengv. 93, p. 447-450, 2006.