Binding of Organic Ligands with Al(III) in Dissolved Organic Matter from Soil: Implications for Soil Organic Carbon Storage

Abstract

The binding characteristics of organic ligands with Al(III) in soil dissolved organic matter (DOM) is essential to understand soil organic carbon (SOC) storage. In this study, two-dimensional (2D) FTIR correlation spectroscopy was developed as a novel tool to explore the binding of organic ligands with Al(III) in DOM present in soils as part of a long-term (21-year) fertilization experiment. The results showed that while it is a popular method for characterizing the binding of organic ligands and metals, fluorescence excitation-emission matrix-parallel factor analysis can only characterize the binding characteristics of fluorescent substances (i.e., protein-, humic-, and fulvic-like substances) with Al(III). However, 2D FTIR correlation spectroscopy can characterize the binding characteristics of both fluorescent and nonfluorescent (i.e., polysaccharides, lipids, and lignin) substances with Al(III). Meanwhile, 2D FTIR correlation spectroscopy demonstrated that the sequencing/ordering of organics binding with Al(III) could be modified by the use of long-term fertilization strategies. Furthermore, 2D FTIR correlation spectroscopy revealed that the high SOC content in the chemical plus manure (NPKM) treatment in the long term fertilization experiment can be attributed to the formation of noncrystalline microparticles (i.e., allophane and imogolite). In summary, 2D FTIR correlation spectroscopy is a promising approach for the characterization of metal-organic complexes.

In situ visualisation and characterisation of the capacity of highly reactive minerals to preserve soil organic matter (SOM) in colloids at submicron scale

“…Our results were used to quantify the effect of highly reactive Al and Fe minerals, led by the allophane (41.38%) and ferrihydrite composition (25.68%), which were consistent with studies by a selective extraction method (Yu et al, 2012;Zhang et al, 2013a;Wen et al, 2014). This result could be because with a shift in microbial metabolism and enzyme production, the meta-stable highly reactive Al and Fe minerals (e.g., allophane and ferrihydrite) could form stable organo-mineral bonds through anion and inner-sphere ligand-exchange reactions, thus being well-suited to physically protect the geometries (Rasmussen et al, 2006;Schmidt et al, 2011;Xie et al, 2014).…”

“…Previous studies have shown that organic fertilisation increased the concentration of highly reactive Al and Fe minerals, which are strongly linked to the SOM preservation capability (Kögel-Knabner et al, 2008;Solomon et al, 2012;Yu et al, 2012;Zhang et al, 2013b;Vogel et al, 2014b). In this study, the soil sample from the MNPK-treated plot was rich in SOC (13.50 g/kg) and SON (1.70 g/kg).…”

“…(Jandl and Sollins, 1997;von Lützow et al, 2006;Kleber et al, 2007Kleber et al, , 2015Keiluweit et al, 2012Keiluweit et al, , 2015. It remains to be seen that the protonated Fe and Al oxides, e.g., allophane, imogolite and ferrihydrite, which affect the physical and chemical stability of SOM in the aqueous and acidic environments (Susan and Margaret, 1997;Eusterhues et al, 2005;Schumacher et al, 2005;Rasmussen et al, 2006;Yu et al, 2012;Wen et al, 2014;Kleber et al, 2015). However, the multiple adsorption/binding mechanisms between organic ligands and mineral surfaces (e.g.…”

Insight into the evolution, redox, and metal binding properties of dissolved organic matter from municipal solid wastes using two-dimensional correlation spectroscopy

“…1a). The signal at 2908-2634 cm À1 was generated by the CAH stretching of aliphatic structures (He et al, 2011;Yu et al, 2012). The existence of the negative cross-peak suggests that the polysaccharide-like and aliphatic substances degraded asynchronously/inversely during composting.…”

“…For instances, the heavy metals bound with humic substances exhibit a low bioavailability compared with the free meal ions, and hexavalent chromium shows a high toxicity with regard to trivalent chromium (He et al, 2014a). DOM can interact with heavy metals or adsorb hydrophilic organic pollutants due to the existence of O-, N-, and S-containing functional groups (Hur and Lee, 2011;Yu et al, 2012), which has an important influence on the bioavailability of the metals in MSWs (Xi et al, 2012). Furthermore, DOM can accept or donate electrons and act as an oxidant or reducing agent (Maurer et al, 2010;Gu et al, 2011), which change the valence state and toxicity of the metals such as Cr (He et al, 2014a).…”