Banca de DEFESA: TAMIRIS CONCEIÇÃO DE AGUIAR

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : TAMIRIS CONCEIÇÃO DE AGUIAR
DATE: 28/05/2021
TIME: 09:00
LOCAL: vídeo conferência
TITLE:

Structural pattern of humic substances using humic acids of different origins as a model

KEY WORDS:

Humic substances. Spectroscopy. Organo-mineral interactions.

PAGES: 40
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUBÁREA: Ciência do Solo
SUMMARY:

humification process of soil organic matter (SOM) as well as the structural identity of humic substances (HS) is today one of the most debated topics in soil science. In the best of our understanding, the criteria reported to challenge the humus theory still lack plausible scientific data and argumentation. In this study, we discuss an hypothetical approximation to the structural patterns of HS, specifically humic acids (HA), which demonstrates that, although there is a need for even more in-depth studies on the chemistry of humus, the existing theories are still valid and HS have a unique and characteristic structural pattern independent of the source of origin. According to this line, the objective of the present dissertation was to access the patterns and structural differences of eighty HA samples isolated from different types of soils and vermicompost through spectroscopic characterization ¹³C NMR CP MAS combined with chemometric techniques of multivariate analysis and descriptive statistics with spectral data. For this, the spectra of eighty HA samples previously isolated and published in other studies and belonging to the spectral database of the Laboratory of Biological Chemistry of Soil, were used for the study. The spectra belong to soil samples from soils classified as Organosol (Brazil), Latosols (Brazil), Cambisolo (Brazil), Chernossolo (Brazil), Ferralitic Rojo (Cuba), Sandy Planossolo (Brazil) and vermicompost (Brazil). All HA were obtained using the same methodology (IHSS) and the ¹³C NMR CP MAS spectra recorded under the same experimental conditions. All spectra were worked using the ACD / Labs 2020 1.1 software. Chemometrics was performed by applying principal component analysis (PCA), multivariate resolution curves (MCR) and descriptive analysis using the software The Unscrambler (version 10.4). The characterization of 81 HA samples using ¹³C NMR CP MAS, extracted from different types of soil and vermicomposting, combined with chemometric techniques, showed an efficient methodology for the study of the structural patterns of humified organic matter in soils and composted sources. All 81 HA characterized have a similar structural pattern, regardless of the source of origin, but all have different relative amounts of chemical structures in their composition. The similarities in the structural patterns show that the humification process occurs in each of these sources and therefore HS are formed. The different structural amounts generate different properties in each HA such as hydrophilicity, hydrophobicity, aromaticity and aliphaticity and therefore there will be a similar function, but with different intensities for each HA. The results suggest that HS are a group of compounds with unique structural identity and different from the molecules that gave rise to them. It suggests that there is not a single humification process and therefore, in each source of origin a humification will develop depending on the characteristics of the environment and therefore, this process occurs with different extensions. This dissertation dialogues with the most current debate on the existence of SH and the soil humus paradigm, as well as providing new evidence in favor of the recognition of SH as compounds with unequivocal structural identity present in the environment.

BANKING MEMBERS:
Externo à Instituição - ADEMIR FONTANA - EMBRAPA
Presidente - 1399485 - ANDRES CALDERIN GARCIA
Interno - 1060711 - MARCOS GERVASIO PEREIRA