01922nam a2200229 a 450000100080000000500110000800800410001902400550006010000190011524501170013426001440025152011640039565000120155965000160157165000100158765300150159765300080161265300210162070000170164170000160165870000180167419515352023-09-25       2013    bl uuuu     u00u1 u    #d7 ahttps://doi.org/10.1007/978-94-007-5634-2_1782DOI1 aNOVOTNY, E. H.  aCharacterisation of humic substances extracted from soil treated with charcoal (Biochar).h[electronic resource]  aIn: XU, J.; WU, J.; HE, Y. (ed.). Functions of natural organic matter in changing environment. Dordrecht: Springer, 2013. p. 971-974.c2013  aThe high fertility and resilience of Terras Pretas de Índios are attributed to the high contents of polycondensed aromatic structures with carboxylic functionality originating from the natural alterations of carbonised biomass added to the soil by the pre-Columbian indigenous populations. There are several proposals to reproduce the positive characteristics of these special soils, including the use of charred biomass (biochar); however, the time necessary to modify this material in the peculiar organic matter of Terras Pretas de Índios is still undetermined. The 13 C NMR analysis of the humic acids extracted at pH 10.6 from soils treated with fines of charcoal indicates that after 3 years a small portion of the added charcoal is already partially oxidised to a compound similar to the ones found in Terras Pretas de Índios; however, the large fraction still looks like unaltered charcoal. Additionally, the proposed method of selective extraction of the characteristic humic fraction from Terras Pretas de Índios, combined with multivariate data analysis tools, can be used as a method to evaluate the proposals to reproduce these special soils.  abiochar  ahumic acids  ahumin  aChemometry  aNMR  aPyrogenic carbon1 aAUCCAISE, R.1 aLIMA, L. B.1 aMADARI, B. E.