Chemical Analysis and Molecular Models for Calcium–Oxygen–Carbon Interactions in Black Carbon Found in Fertile Amazonian Anthrosoils

• Published in: Environmental science & technology Vol. 48; no. 13; pp. 7445 - 7452
• Main Authors: Archanjo, Braulio S, Araujo, Joyce R, Silva, Alexander M, Capaz, Rodrigo B, Falcão, Newton P. S, Jorio, Ado, Achete, Carlos A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.07.2014
• Subjects: Brazil; Calcium; Calcium - chemistry; Carbon; Carbon - chemistry; Climate change; Earth sciences; Earth, ocean, space; Electrons; Engineering and environment geology. Geothermics; Exact sciences and technology; Models, Molecular; Molecular Conformation; Nanoparticles; Nanostructures - ultrastructure; Oxygen; Oxygen - chemistry; Photoelectron Spectroscopy; Pollution, environment geology; Soil - chemistry; Soil fertility; Soil sciences; Soils; Soot - chemistry; Spectrometry, X-Ray Emission; Spectrum analysis; Surficial geology; South America; Amazonia; Fourier transformation; calcium; fertilization; oxides; X-ray spectroscopy; human activity; chemical analysis; molecular structure; carbon; humidity; transmission electron microscopy; residence time; particles; soils; oxygen; climate change; infrared spectroscopy
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es501046b

Carbon particles containing mineral matter promote soil fertility, helping it to overcome the rather unfavorable climate conditions of the humid tropics. Intriguing examples are the Amazonian Dark Earths, anthropogenic soils also known as “Terra Preta de Índio’’ (TPI), in which chemical recalcitrance and stable carbon with millenary mean residence times have been observed. Recently, the presence of calcium and oxygen within TPI-carbon nanoparticles at the nano- and mesoscale ranges has been demonstrated. In this work, we combine density functional theory calculations, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transformed infrared spectroscopy, and high resolution X-ray photoelectron spectroscopy of TPI-carbons to elucidate the chemical arrangements of calcium–oxygen–carbon groups at the molecular level in TPI. The molecular models are based on graphene oxide nanostructures in which calcium cations are strongly adsorbed at the oxide sites. The application of material science techniques to the field of soil science facilitates a new level of understanding, providing insights into the structure and functionality of recalcitrant carbon in soil and its implications for food production and climate change.