UV - visible spectroscopic properties of dissolved fulvic acids extracted from salined fluvo-aquic soils in the Hetao Irrigation District, China

Abstract

The elemental composition and the UV–visible spectroscopic properties of dissolved fulvic acids (FA) extracted from salined fluvo-aquic soils in the Hetao Irrigation District were examined to evaluate the humification degree of FA and salinisation processes of soils. Composite soil samples of different depths (0–20, 20–40, 40–60, 60–80 cm) were collected from four native halophyte soils [communities Salicornia europaea (CSE), Suaeda glauca (CSG), Kalidium foliatum (CKF), Sophora alopecuroides (CSA)] and two furrow-irrigated fields [corn (CFD), wheat (WFD)] along a saline impact gradient. Seven humification indices (HIXs: C/N, SUVA, E2/E3, E2/E4, S275–295, S350–400, and S250–400), deduced from elemental analysis and UV–visible spectroscopy of FAs, were used to evaluate the humification degree. The humification degree of FA from the WFD soil was the highest, followed by CFD, CSA, CKF, CSG, and CSE. There were significant relationships between the seven HIXs (P < 0.05). The exchangeable sodium percentage (ESP) exhibited close correlations with the seven HIXs, and the humification degree increased with decreasing ESP. The HIX can not only indicate the humification degree of soil organic matter but also characterise the salinisation processes of soils.

Combination of two-dimensional correlation spectroscopy and parallel factor analysis to characterize the binding of heavy metals with DOM in lake sediments

“…1c). However, the absorbance of MDOM was higher than that of ADOM along the whole wavelength, implying that MDOM was characterized with more aromatic substances and functional groups (i.e., C O or OH) than ADOM [12,32]. Fig.…”

“…The absorbance of both MDOM and ADOM exhibited gradual increase with step addition of metal titrants. DOM binding with metal ions was reported to be related to some functional groups containing lone pairs and bonds electrons such as C O, OH, and aromatic structures [32,33]. These possible complexations increased the dislocation of electrons, which consequently led to an increase in absorbance [33].…”

Soil Organic Carbon Molecular Properties: Effects of Time Since Reclamation in a Minesoil Chronosequence

“…Spectroscopic techniques provide useful information about the structural and compositional characteristics of SOC molecules (Muñoz et al ., ), based on the intensity and position of different absorption bands, diagnostic to the structure and composition of specific chromophores (functional groups) (Liying et al ., ; Yu et al ., ). A variety of ultraviolet‐visible (UV‐vis) (Chin et al ., ; Khorsin et al ., ; Peuravori and Pihlaja, ; Jiang et al ., ), fluorescence (Senesi et al ., , ; Baker, ; Swietlik and Sikorska, ; Birdwell and Engel, ), and Fourier transform infrared (FT‐IR) (Haberhauer et al ., , ; Ellerbrock et al ., ; Gerzabek et al ., ) spectroscopic indices have been devised to relate molecular characteristics of SOC to its source, quality, and decomposition pathways. The advantages of spectroscopic techniques include the following: (i) a nondestructive aspect of methodology; (ii) a small sample size; and (iii) the simplicity in sample preparation (Chen et al ., ).…”

Differentiation Between Humic and Non-Humic Substances Using Alkaline Extraction and Ultraviolet Spectroscopy

“…Numerous studies have explored the differences in UV-Vis light spectra of alkaline extracts of dissolved natural organic matter in an effort to establish UV-Vis indices of humification ( 15 ). The indices have been used to determine the degree of humification in soils ( 16 ), composts ( 21 ), the aquatic environment ( 22 ), and peat ( 5 , 23 ), using either ratios of absorbance, molar absorption coeffcients, or absorbance relative to normalized carbon concentration at specific wavelengths of light ( Table 1 ). As these indices demonstrate there are distinct differences between humified and non-humified materials, an investigation into their potential fit for purpose as standardized analytical methods was carried out.…”

“…used absorbance data at wavelengths <280 and/or >350 nm to determine the degree of humification ( 16 , 17 , 27 ),…”