Search results for "Natural Organic Matter"
showing 10 items of 12 documents
Photochemical Mineralization of Terrigenous DOC to Dissolved Inorganic Carbon in Ocean
2018
Sequestration of organometallic compounds by natural organic matter. binding of trimethyltin(IV) by fulvic and alginic acids
2006
The binding capacity of fulvic and alginic acids towards trimethyl tin(IV) cation was quantitatively determined in order to evaluate the sequestering ability of toxic organometallic compounds by natural organic matter. Investigations were performed in the pH range of natural waters (5–8.5) where the carboxylate groups, largely present in both sequestering agents, are the main binding sites. A chemical interaction model, according to which both the protonation of polyelectrolyte ligands and the hydrolysis of the organotin cation in NaCl aqueous solution were considered, was used to define the speciation of the systems under investigation. Measurements performed at different ionic strength va…
Effect of RF Field Inhomogeneity and Sample Restriction on Spectral Resolution of CP/MAS-13C NMR Spectra of Natural Organic Matter
2010
It is well known that the induced B1 magnetic field in an NMR coil is inhomogeneously distributed. However, this issue has so far received little attention in the field of environmental NMR. As this research field often aims at quanti- tative results as well as relaxation phenomena, the repercussions of such inhomogeneity on peak integrals and relaxation times need to be taken into account. The objective of the present study was to test standard recording conditions on different sample positions in an NMR coil in order to determine the effect of the RF field inhomogeneity on the spectrum of a molecularly complex humic material and on some standard molecules of known structure and conformati…
A screening study on the fate of fullerenes (nC60) and their toxic implications in natural freshwaters
2013
Increasing usage of fullerenes (C60) increases their opportunities to be released into the environment. For risk assessment, it is important to understand the environmental fate and ecotoxicological effects of C60. In the present study, fullerene settling was measured during a 1-yr period with 4 different lake waters and an artificial freshwater, and Daphnia magna immobilization and fullerene accumulation was also measured in each of the lake waters. Depending on the characteristics of the lake waters, fullerenes either exhibited extended water stability or settled rapidly; in all waters, there was a fraction that remained stable after 1 yr. Water stability was affected by the quality and m…
Low field NMR spectroscopy for quality evaluation of natural organic matter
2009
Effect of wetting/drying on the conformational arrangement of a heterogeneous organic mixture as assessed by solid state 13C NMR spectroscopy
2008
State of the art of CPMAS 13C-NMR spectroscopy applied to natural organic matter
2004
A number of different techniques are presently available for characterizing humified natural organic matter (NOM). Carbon-13 nuclear magnetic resonance spectroscopy (13C-NMR) in the solid state using cross-polarization (CP) and magic angle spinning (MAS) represents the most powerful experimental approach used to collect direct information on the structural and conformational characteristics of humic carbon backbones. Despite the problems due to the presence of paramagnetic impurities and the generally low organic matter concentration, cross-polarization magic angle spinning 13C-NMR spectroscopy (CPMAS 13C-NMR) is applied in soil chemistry and geochemistry mainly because of its relevance in …
ChemInform Abstract: Environmental NMR: Fast-Field-Cycling Relaxometry
2016
Fast-field-cycling (FFC) NMR relaxometry deals with the variation of the spin–lattice relaxation times (T1) in a complex system, as the strength of the applied magnetic field is changed. Information about molecular dynamics can be achieved. Until now, only model theories for FFC NMR relaxometry have been developed for polymer and material sciences. Just a few applications have been performed in the environmental sciences. These mainly deal with soil porosity, rock permeability, biomass transformations, and natural organic matter dynamics. Further, FFC NMR relaxometry can also be applied to monitor the environmental fate of contaminants, to understand the dynamics of nutrients at the soil–pl…
Environmental NMR: Fast-field-cycling Relaxometry
1996
Fast-field-cycling (FFC) NMR relaxometry deals with the variation of the spin–lattice relaxation times (T1) in a complex system, as the strength of the applied magnetic field is changed. Information about molecular dynamics can be achieved. Until now, only model theories for FFC NMR relaxometry have been developed for polymer and material sciences. Just a few applications have been performed in the environmental sciences. These mainly deal with soil porosity, rock permeability, biomass transformations, and natural organic matter dynamics. Further, FFC NMR relaxometry can also be applied to monitor the environmental fate of contaminants, to understand the dynamics of nutrients at the soil–pl…
Solid state nuclear magnetic resonance spectroscopy as a tool to characterize natural organic matter and soil samples. The basic principles
2007
Basic principles of solid state nuclear magnetic resonance spectroscopy (SS-NMR) are presented here. This paper is not pretending to provide an exhaustive treatment of the basics of SS-NMR. However, it will give an overview of the main applications in the characterization of environmental systems and will describe the problems related to the acquisition of quantitative solid state NMR spectra.