Morphological analysis of soil particles at multiple length-scale reveals nutrient stocks of Amazonian Anthrosols

Abstract

We have imaged the particles of Brazilian soils at multiple length scales, from a few microns to millimeters, and soil particle size distributions were calculated with unmatched precision. The analysis included the Amazonian soil "Terra Mulata de Índio" (TMI), an anthropogenic soil (Anthrosol) with sustained fertility and a large amount of stabilized organic matter. Firstly, the soils were imaged ex situ, without any chemical processing, with sequential electron scanning of the pelletized soil samples, covering a total area of 8 × 8 mm. Secondly, it was performed a computational analysis of the large-field X-ray images assembled from hundreds of adjacent elemental maps, thus resulting in high-definition images (4800 × 4800 pixels). This analytical approach provides a large sampling with the identification of > 10,000 particles over the scanned area. The particles identified consisted of Al, C, Ca, Cr, F, Fe, Mg, Mn, Na, O, P, S, Si and Ti. A significantly larger concentration of C-, Ca-and P-based particles, of up to 100 μm 2 of cross-section area, was found in TMI samples in comparison with oxisol and ultisol soils. While the mean distance between neighboring C, Ca and P particles in TMI was of 40-70 μm, the value was of hundreds of microns in oxisol and ultisol. Furthermore, mapping of micrometric carbon particles by Raman spectroscopy indicated that they have a graphitic structure with a large amount of defects, partially associated with particle oxidation, although a well-preserved sp 2 graphitic structure is also present. From a technological perspective, improved soil amendments, such as biochar, can be rationally designed from the "fingerprint" described here for soil particles of Amazonian Anthrosols (i.e., morphological and structural characteristics), which can result in an increase in fertility and the optimization of carbon sequestration in the future.

Chemical and Spectroscopic Characteristics of Anthrosol (Amazonian Dark Earth) and Surrounding Soil from the Brazilian Amazon Forest: Evaluation of Mineral and Organic Matter Content by Depth

“…The hydrophobic SOM was mainly in the top layer, thereby suggesting that the layer most altered by anthropogenic action was at the surface. Beyond the nutrient contents that were present in the OM, 11,12,68 the alkaline extraction showed a greater interaction of SOM with aluminum from soil minerals. Both hydrophobicity and interactions with minerals play an important role in SOM stabilization, 27 thereby increasing the thermodynamic stability as pointed out by DTG.…”

“…10 ADE soils are highly fertile because the OM is present in recalcitrant and reactive forms, which is attributed to the presence of carbon nanoparticles (2-8 nm) with a graphitelike core and oxidized surface. [11][12][13] Thus, graphite-like structures prolong the amount of time that the carbon is in the soil and the oxidized surface promotes the increased cation exchange capacity of the soil, thereby increasing the retention of nutrients. This practice inspired the production of pyrochar/hydrochar for soil applications (biochar) worldwide in efforts to mimic some of the properties of ADE soils.…”

Disponibilidade De Nutrientes E Carbono Orgânico Em Solos Contendo Carvão Hidrotérmico Lavado E Não Lavado E Comparação Com Solos Antropogênicos

“…As amostras de solos foram coletadas nas camadas superficiais de 0-20 cm, secas ao ar a temperatura ambiente, homogeneizadas e peneiradas (<2 mm). 42 Para os experimentos de liberação em coluna, foram utilizados 4 tipos de solos (1) argissolo (20°48'19.0"S e 49°19'40,2"W), (2) latossolo (20°48'19.79"S e 49°19'43.51"W) 30,39 solos antropogênicos da Amazônia: (3) Terra Mulata (TM) (3°04'05.17"S e 58°34'11.68"O) 30 e (4) Terra Preta de Índio (TPI) (04°04'51.9''S e 058°24'50.7''O) e (5) um controle de areia quartzosa. Os solos antropogênicos foram coletados e tiveram liberação do Instituto Brasileiro do Meio Ambiente e dos recursos Ambientais Renováveis (Autorização de Coleta SISBIO n° 50042-2) e cadastro no Sistema Nacional de Gestão do Patrimônio Genético e do Conhecimento Tradicional Associado (SISGen) número A0018C2.…”

“…[27][28][29] A inspiração de aplicar carvões ao solo surgiu com o advento dos solos denominados "Terra Preta de Índio" (TPI) e Terras Mulatas (TM) encontrados na Amazônia, os quais são solos antropogênicos conhecidos pela elevada fertilidade associada à presença de P, Ca, Mg, Zn, Mn e ao alto teor de C estável (de origem pirogênica). 30 Essa característica contribui com a estabilização da matéria orgânica no solo (MOS), proporciona aumento da atividade microbiana e o sequestro de carbono. [31][32][33] Além disso, contribui para o aumento da capacidade de troca catiônica (CTC) dos solos.…”

Dynamic of the structural alteration of biochar in ancient Anthrosol over a long timescale by Raman spectroscopy

“…Raman spectroscopy is very sensitive to alterations in the structure of carbon and therefore is able to shed light on the degradation of biochar in soil. This technique has been used for studies of the nanostructures of charcoal (biochar) in Anthrosols [4,20,32,33].…”