Modulation of Optical Properties of Dissolved Humic Substances by their Molecular Complexity§

RICARDO MIGNONE; MARCELA MARTIN ; FAUSTINO E. MORAN VIEYRA,; VALERIA I. PALAZZI; BEATRIZ LOPEZ DE MISHIMA; DANIEL O. MARTIRE; CLAUDIO D. BORSARELLI

PHOTOCHEMISTRY AND PHOTOBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2011 vol. O p. 1 - 2

0031-8655

In the present work, we present several UV-VIS absorbance, steady-state and time-resolved fluorescence parameters of a series of dissolved humic substances (DHS) from differentsources and nature (e.g. terrestrial fulvic and humic acids, and humic acid-like substancesextracted from composted and vermicomposted wastes). Several spectroscopic parameterscorrelated with the molar absorptivity at 280 nm per mole of organic carbon (å8 280), which in turns is proportional to the molecular complexity (molecular size, aromaticity and oxidation degree, etc.) of the DHS. Both absorbance and fluorescence spectral responses were verysensitive to the molecular complexity associated with the maturation degree of the DHS.Therefore, depending on the molecular complexity of the DHS, different emitting responses by excitation at the UVA (360 nm) and VIS (460 nm) regions of the absorption spectra oDHS were observed. The results were explained in terms of the increment of intramolecularlow-energy absorbing and emitting energy/electron-transfer states formed by donor moietiesgroups, e.g. polyhydroxylated aromatics, indoles, etc. and more oxidized acceptor groups (e.g. quinones or other oxidized aromatics, etc.) as the molecular complexity of the DHS increased.