Studies of the Compositions of Humic Acids from Amazonian Dark Earth Soils

Abstract

ABSTRACT. The compositions of humic acids (HAs) isolated from cultivated and forest 'Terra Preta de Índio' or Amazonian Dark Earth (ADE) soils (formed as the result of pre-Columbian anthropogenic activity) were compared with those from adjacent non-anthropogenic soils (NAS) using elemental and thermogravimetric analyses, and a variety of solid state nuclear magnetic resonance (NMR) techniques. The thermogravimetric index (TGI, or the ratio of the weight lost in the range 378 to 623K, indicative of polysaccharides and the decarboxylation of acidic groups, to that in the range 623 to 923K, indicative of combustion of aromatic structures and cleavages of C-C bonds) was greater for the anthropogenic soils than for the control soils indicating polycyclic aromatic components in the former. The cultivated anthropogenic soils (CAS) were more enriched in C and depleted in H than the anthropogenic soils under forest (ASF), as the result of the selective degradation of aliphatic structures and the possible enrichment of H-deficient condensed aromatic structures.

Variabilidade Espacial e Densidade Amostral da Suscetibilidade Magnética e dos Atributos de Argissolos da Região de Manicoré, AM

“…Esse resultado é em razão da presença do horizonte antrópico na superfície do solo. Campos et al (2011) encontraram valores semelhantes para Ca 2+ e Mg 2+ , os quais afirmaram que as TPAs exibem elevados níveis de nutrientes, principalmente Ca 2+ e P, provavelmente proveniente de restos de ossos humanos e de animais, além da formação de complexos matéria orgânica-Ca, de alta estabilidade (elevados teores de Ca), associados ao carvão pirogênico (Novotny et al, 2007). O P normalmente apresenta valores elevados em solos com presença de horizonte antrópico, de acordo com Falcão e Borges (2006), os quais afirmaram que esses altos valores de P são uma característica peculiar das TPAs; essa característica tem sido observada por muitos autores e é atribuída à incorporação de ossos de animais (e, possivelmente, de seres humanos), de espinhas de peixes e de carapaças de quelônios (Lima et al, 2002 A acidez potencial (H+Al) foi menor para a área com TPA e maior para as áreas com floresta e pastagem, respectivamente.…”

Biochar: Pyrogenic Carbon for Agricultural Use - A Critical Review

“…The quantification of pyrogenic C is of paramount importance to evaluate its role in soil C stocks and its fate in the environment, but is a great methodological challenge (Derenne and Largeau, 2001;Masiello, 2004;Simpson and Hatcher, 2004;Novotny et al, 2006Novotny et al, , 2007Hammes et al, 2007). The reason is that, first of all, the pyrogenic C pool must be considered in a continuum model of carbonization (Figure 3) (Masiello, 2004), which is very complex and comprises different products, ranging from slightly charred, degradable biomass to highly condensed, refractory soot, with gradual changes in properties and structures, in which the co-existence of several of the continuum products is common.…”

“…This correction however assumes that the mass ratio of BPCA/pyrogenic C is constant, which was not properly evaluated for a broad spectrum of charred materials or weathered coal, which is already partially oxidized to aromatic carboxylic acids (Glaser et al, 2002;Kramer et al, 2004;Novotny et al, 2007Novotny et al, , 2009Maia et al, 2011;Linhares et al, 2012;Araujo et al, 2014).…”

“…The CEC depends mainly on: the content and properties of volatile matter for low carbonized biochar (Mukherjee et al, 2011), however due to the lability of this fraction, this effect is probably transient; the cooling of biochar with O 2 supply can oxidize it, generating carboxylic functionalities (Spokas et al, 2012); the aging of biochar also generates these functionalities (Cheng et al, 2006;Novotny et al, 2007Novotny et al, , 2009Heitkötter and Marschner, 2015). On the other hand, the anionic exchange capacity decreases with aging (Cheng et al, 2008); d. Sorption of nutrients and heavy metals (Beesley et al, 2011;Kookana et al, 2011;Melo et al, 2013): the adsorption of hard Lewis acids (e.g.…”

“…In addition to these misuses, concerning the objectives of biochar, of terms dissenting from the definition, the expression "biochar in Terra Preta de Índios (Amazonian Dark Earth)" presupposes that the pre-Columbian Native Americans treated and improved soil intentionally, which is definitely not a consensus in the literature (Novotny et al, 2007). The use of the term biochar for the pyrogenic C found in the Terra Preta de Índios must therefore be completely avoided, to prevent the common mistake of assuming that these soils resulted from intentional treatments.…”