Molecular composition of several soil organic matter fractions from anthropogenic black soils (Terra Preta de Índio) in Amazonia — A pyrolysis-GC/MS study

Exploratory on-line pyrolysis and thermally assisted hydrolysis and methylation for evaluating non-hydrolyzable organic matter in anthropogenic soil from Central Brazilian

“…This trend was less evident for dibenzofuran/ metlhyldibenzofuran and biphenyl/methylbiphenyl, these ratios being higher in the ADE sample considering only the three lowest horizons (p<0.01, Table II, Figure 2). This major relative contribution of aromatic compounds vs. their methylated counterparts in the ADE is a distinct feature of BC, in agreement with the greater contribution from PAHs without alkyl side chains in a TPI (Terra Preta de Índio) soil samples reported by Schellekens et al [30] and Justi et al [49]. These results may indicate a more recalcitrant BC with a highly condensed aromatic structure and, consequently, a higher dealkylation ratio of pyrolysis product in anthropogenic soils [26][27]49].…”

“…These results may indicate a more recalcitrant BC with a highly condensed aromatic structure and, consequently, a higher dealkylation ratio of pyrolysis product in anthropogenic soils [26][27]49]. These differences may also be the result of different inputs and/or decomposition processes for the two soils [30].…”

“…The non-hydrolyzable SOM was marked by a similar distribution of Py-GC-MS and THM-GC-MS products for the ADE and adjacent soil profiles (Tables II and III), with only small differences in the relative abundances, which was mainly demonstrated by the dealkylation ratios of the pyrolysis product ( Figure 2). The pyrolysis of SOM obtained from mineral and organic soils generally leads to a high relative contribution of PAH and benzene derivatives [24,30,[38][39] of which alkyl benzenes and PAH have been attributed to the burning of biomass (BC) [24,[26][27]30], methoxyphenols from lignin and carbohydrates andcontaining compounds from microbes [40]. In this study, benzene was a prominent component in the ADE products, mainly at lower depths (36-150 cm), with a lower abundance being observed for the AS profile (Table II, p<0.05).…”

Chemical characteristics of Amazonian Dark Earth in Santarem, Brazil

“…ADEs present higher amounts of calcium, manganese and phosphorus in relation to the nonanthropogenic Oxisols and Ultisols [4][5][6]. They also present high amounts of stable organic matter, being rich in pyrogenic carbon (black carbon) [4,7] thus the presence of ceramics and/or lithic material is a striking feature [8][9]. Their high fertility is due to the incorporation of inorganic (bones and ashes) and organic (plants and animals) residues into the soil [4,10], which results in soils with moderate acidity and low levels of exchangeable aluminum [11].…”

Long-term persistence of soil organic matter in Amazonian Dark Earth

“…3). Several studies have been conducted in Caldeirão to investigate ADE characteristics (Barbosa Lima et al, 2015;Germano et al, 2012;Kern et al, 2019;Nakamura et al, 2014;Schellekens et al, 2017;Schmidt, 2006;Schmidt et al, 2014;Taube et al, 2013), which makes it one of the most extensively studied and represented ADE site. Nonetheless, future studies at other ADE sites are encouraged to use the geostatistical method I propose in Chapter 2 (Alho et al, 2019) for a better comprehension of the high spatial variation in other ADE sites and to systematically distinguish ADE from ADJ and therefore account for the overall differences between these areas.…”