Data/hora: 07/06/2024 18:26:14

Biblioteca(s): 	Embrapa Solos.	
Data corrente: 	09/12/2008	
Data da última atualização: 	27/10/2021	
Autoria: 	NOVOTNY, E. H.; KNICKER, H.; MARTIN NETO, L.; AZEREDO, R. B. V.; HAYES, M. H. B.	
Afiliação: 	ETELVINO HENRIQUE NOVOTNY, CNPS; H. Knicker, Lehrstuhl fur Bodenkunde, Technische Universitat Munchen; LADISLAU MARTIN NETO, DE/P&D; R. B. V. AZEREDO, UFF; M. H. B. HAYES, Chemical and Environmental Sciences University of Limerick.	
Título: 	Effect of residual vanadyl ions on the spectroscopic analysis of humic acids: a multivariate approach.	
Ano de publicação: 	2008	
Fonte/Imprenta: 	European Journal of Soil Science, Oxford, v. 59, n. 3, p. 439-444, Jun. 2008.	
DOI: 	https://doi.org/10.1111/j.1365-2389.2007.00983.x	
Idioma: 	Inglês	
Conteúdo: 	In a study of the vanadyl (VO2þ)-humic acids system, the residual vanadyl ion suppressed fluorescence and specific electron paramagnetic resonance (EPR) and NMR signals. In the case of NMR, the proton rotating frame relaxation times (T1qH) indicate that this suppression is due to an inefficient H-C cross polarization, which is a consequence of a shortening of T1qH. Principal components analysis (PCA) facilitated the isolation of the effect of the VO2þ ion and indicated that the organic free radical signal was due to at least two paramagnetic centres and that the VO2þ ion preferentially suppressed the species whose electronic density is delocalized over O atoms (greater g-factor). additionally, the newly obtained variables (principal components ? PC) indicated that, as the result of the more intense tillage a relative increase occurred in the accumulation of: (i) recalcitrant structures; (ii) lignin and long-chain alkyl structures; and (iii) organic free radicals with smaller g-factors.	
Palavras-Chave: 	Ácidos húmicos; Análise espectroscópica.	
Categoria do assunto: 	P Recursos Naturais, Ciências Ambientais e da Terra	
Registro original: 	Embrapa Solos (CNPS)	
Exemplares: 	CNPS - (13577-1) - UPC - AP - DD -  -  - 2008.00057 - DIS