scholarly journals Determination of dissolved organic carbon in soils with UV spectroscopy, ultrasonic dispersion pre-treatment and separation with size exclusion chromatography .

2014 ◽  
Vol 4 ◽  
Author(s):  
Schomakers Jasmin ◽  
Mentler Axel ◽  
Herwig Mayer
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Size Exclusion Chromatography ◽  
Uv Spectroscopy ◽  
Energy Levels ◽  
Carbon Pool ◽  
Size Exclusion ◽  
Soil Types ◽  
Exclusion Chromatography ◽  
Pre Treatment

This study aimed to reveal differences in UV (ultraviolet) -absorbing dissolved organic carbon (DOC) between three prominent Austrian soil types: a Cambisol and a Chernozem developed from Tertiary marl, both under agricultural management, and a Podzol from a mixed coniferous beech forest stand. Topsoil samples (0–300 mm) were pre-treated, air-dried, sieved and four grams of each probe was added to 80 cm<sup>3</sup> of de-ionized water and subjected to ultrasonic treatment with specific energies of 6.7 J cm<sup>-3 </sup>and 161 J cm<sup>-3</sup>, respectively, which dispersed the macroaggregates and released formerly occluded soluble carbon. The soils were investigated for morphological differences with a scanning electron microscope after sonication. The suspensions were filtered &lt; 0.45 µm and UV-spectroscopy at 254 nm was performed after the dispersion pre-treatment. In addition the suspension was separated by high performance size exclusion chromatography linked to an UV-vis detector measuring at 254 nm and 210 nm and dissolved organic carbon (DOC) was determined. More DOC was released with higher specific energies for all soil types in the sequence Podzol &gt; Cambisol &gt; Chernozem but the differences in SOM/DOC ratio became less significant with increasing ultrasonic energy. The detected molecules were in the range of 1300-1600 Da for Cambisol, 1500-5400 Da for Chernozem and 1700-10400 Da for Podzol. The different energy levels reached different carbon pools. Based on a model according to von Lützow et al. (2008), the applied energy levels of 6.7 J cm<sup>-3</sup> reached the active carbon pool consisting of plant residues and exudates, and microbial/faunal biomass and residues. Sonication with 161 J cm<sup>-3</sup> dispersed more aggregate fractions and released carbon from the intermediate carbon pool where biogenic aggregation preserves the organic matter pool.

Measuring dissolved organic matter in estuarine and marine waters: size-exclusion chromatography with various detection methods

2018 ◽  
Vol 15 (7) ◽  
pp. 436 ◽  
Author(s):  
Gabriel Dulaquais ◽  
Johann Breitenstein ◽  
Matthieu Waeles ◽  
Rémi Marsac ◽  
Ricardo Riso
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Humic Substances ◽  
Size Exclusion Chromatography ◽  
Size Exclusion ◽  
Marine Waters ◽  
Wide Range ◽  
Exclusion Chromatography

Environmental contextDissolved organic matter (DOM), a key parameter in aquatic biogeochemistry, is difficult to characterise owing to its variable composition and structure. We report a chromatographic method with carbon, nitrogen and absorbance detection able to record the size distribution of DOM and changes in its composition. The method could be used to identify additional sources to river or coastal waters as well as monitoring the DOM size/reactivity continuum in open oceans. AbstractWe studied the performance and limitations of size-exclusion chromatography with organic carbon, ultraviolet and organic nitrogen detectors (SEC-OCD-UVD-OND) for characterising dissolved organic matter (DOM) in estuarine and marine waters. We identified a strong salt effect on dissolved organic carbon (DOC) determination; however, calibration gave good results at salinity levels close to those of the sample analysed (ΔS ± 2 psu (practical salinity units)), with limited matrix effects, enabling an accurate measurement of DOC, as demonstrated by an intercalibration exercise. The repeatability, reproducibility and limit of detection (3 ppb for both carbon and nitrogen) for the three detectors demonstrated the robustness of the method for a wide range of natural waters, including carbon-rich freshwaters and deep seawaters with low carbon content (6000 ppb-C to 300 ppb-C). Deeper analysis of the SEC demonstrated that proteins and polysaccharides are partly fractionated within the column, and that terrestrial humic substances, isolated on a XAD-8 resin, can also be eluted in both fractions associated with biopolymers and low-molecular-weight neutrals. Application of the method to the study of DOM along a macrotidal estuary that was influenced by agricultural activities revealed significant changes in its composition despite a conservative DOC distribution. Distinct origins and qualities of high-molecular-weight (>500 kDa) organic compounds were identified for riverine and marine end-members. A new diagram to track changes in DOM lability is proposed to complete the humic-substances diagram.

Modification of Spruce Lignans with Trametes hirsuta Laccase

Holzforschung ◽  
2002 ◽  
Vol 56 (6) ◽  
pp. 579-584 ◽  
Author(s):  
J. Buchert ◽  
A. Mustranta ◽  
T. Tamminen ◽  
P. Spetz ◽  
B. Holmbom
Keyword(s):  
Gas Chromatography ◽  
Size Exclusion Chromatography ◽  
Uv Spectroscopy ◽  
Size Exclusion ◽  
Trametes Hirsuta ◽  
Spruce Wood ◽  
Exclusion Chromatography

Summary The effect of Trametes hirsuta laccase on isolated spruce wood lignans was evaluated. Lignans were isolated from the heartwood of spruce branches and treated with different laccase dosages and treatment times. The effect of the treatment was monitored by gas chromatography, size exclusion chromatography and ionization difference UV spectroscopy. Lignans were efficiently oxidized by T. hirsuta laccase. About half of the phenolic groups present in lignans remained intact during the treatment. The oxidation of phenolic groups in lignans produced oligomeric structures containing approximately 4–5 lignan units (i.e., 8–10 phenyl propane units). Precipitation of the formed oligomeric structures probably prevented further polymerization.

Influence of porosity and surface chemistry of commercially available powdered activated carbons for the removal of dissolved organic carbon

2006 ◽  
Vol 6 (3) ◽  
pp. 27-34 ◽  
Author(s):  
R. Treguer ◽  
A. Couvert ◽  
D. Wolbert ◽  
H. Suty ◽  
G. Randon
Keyword(s):  
Drinking Water ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Surface Chemistry ◽  
Size Distribution ◽  
Activated Carbons ◽  
Size Exclusion ◽  
Drinking Water Resources ◽  
Exclusion Chromatography ◽  
Maximum Removal

More restricting legislation on Dissolved Organic Carbon (DOC) content in drinking water, especially when applied to waters with high DOC contents and low turbidity, urges the industry to improve, all along the processes, the removal of dissolved organic matter (DOM) in drinking water resources. This work focused on the characterisation of the performances of commercially available powdered activated carbons (PAC). Equilibrium isotherms were carried out on pre-treated water, i.e. after coagulation, flocculation and sedimentation. In order to determine the efficiency of the PAC, the DOM content was estimated through DOC and UV absorbance measures, as well as being characterised by size exclusion chromatography. The various experiments carried out showed some differences in the adsorption capacity, depending on their pore distribution and surface chemistry. The maximum removal ratio reached 82% and 45% for DOC and SUVA respectively. The isotherm equilibrium results can be used to define several kinds of DOC fractions, which were modelled by the Freundlich equation. Finally, the SEC chromatograms showed that the pore size distribution of the activated carbons affected significantly the compound size distribution of the removed DOM.

Dissolved organic carbon characteristics in an acidified groundwater-dependent ecosystem

2015 ◽  
Vol 66 (7) ◽  
pp. 582 ◽  
Author(s):  
Azra Mat Daud ◽  
Suzanne McDonald ◽  
Carolyn E. Oldham
Keyword(s):  
Molecular Structure ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Principal Component ◽  
Size Exclusion ◽  
Acidic Groundwater ◽  
Column Adsorption ◽  
Exclusion Chromatography ◽  
Doc Concentration ◽  
High Concentrations

Quantifying and characterising dissolved organic carbon (DOC) is critical to understanding its role in aquatic ecosystems. This is particularly challenging in acidic groundwater-dependent ecosystems, where low pH and high concentrations of Fe affect DOC characterisation. We investigated the variability in DOC concentrations and chemical structure in an acidic wetland, using UV visible spectrophotometry, a range of digestion methods and subsequent TOC analysis, high-pressure size exclusion chromatography (HPSEC) and rapid fractionation techniques. HPSEC results showed that increasing the pH from an original pH 2.3 to a neutral pH reduced the column adsorption of organic carbon, but did not change molecular weight distributions. Principal component analysis suggested that iron concentrations had a more direct effect on molecular structure than pH. The pH, Fe concentrations and DOC characteristics were highly dynamic and spatially variable, and were linked to surface water–groundwater connectivity, as well as horizontal connectivity of surface ponding. The changing pH and Fe concentrations affected DOC concentration and molecular structure with expected effects on bioavailability of DOC.

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