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.

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.

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.

scholarly journals Three representative UK moorland soils show differences in decadal release of dissolved organic carbon in response to environmental change

2011 ◽  
Vol 8 (12) ◽  
pp. 3661-3675 ◽  
Author(s):  
M. I. Stutter ◽  
D. G. Lumsdon ◽  
A. P. Rowland
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Environmental Change ◽  
Soil Properties ◽  
Process Models ◽  
Environmental Drivers ◽  
Specific Response ◽  
Soil C ◽  
Doc Concentration ◽  
Mineral Soils

Abstract. Moorland carbon reserves in organo-mineral soils may be crucial to predicting landscape-scale variability in soil carbon losses, an important component of which is dissolved organic carbon (DOC). Surface water DOC trends are subject to a range of scaling, transport and biotic processes that disconnect them from signals in the catchment's soils. Long-term soil datasets are vital to identify changes in DOC release at source and soil C depletion. Here we show, that moorland soil solution DOC concentrations at three key UK Environmental Change Network sites increased between 1993–2007 in both surface- and sub- soil of a freely-draining Podzol (48 % and 215 % increases in O and Bs horizons, respectively), declined in a gleyed Podzol and showed no change in a Peat. Our principal findings were that: (1) considerable heterogeneity in DOC response appears to exist between different soils that is not apparent from the more consistent observed trends for streamwaters, and (2) freely-draining organo-mineral Podzol showed increasing DOC concentrations, countering the current scientific focus on soil C destabilization in peats. We discuss how the key solubility controls on DOC associated with coupled physico-chemical factors of ionic strength, acid deposition recovery, soil hydrology and temperature cannot readily be separated. Yet, despite evidence that all sites are recovering from acidification the soil-specific responses to environmental change have caused divergence in soil DOC concentration trends. The study shows that the properties of soils govern their specific response to an approximately common set of broad environmental drivers. Key soil properties are indicated to be drainage, sulphate and DOC sorption capacity. Soil properties need representation in process-models to understand and predict the role of soils in catchment to global C budgets. Catchment hydrological (i.e. transport) controls may, at present, be governing the more ubiquitous rises in river DOC concentration trends, but soil (i.e. source) controls provide the key to prediction of future C loss to waters and the atmosphere.

scholarly journals The effect of dissolved organic carbon on pelagial and near-sediment water traits in lakes

2011 ◽  
Vol 74 (2) ◽  
pp. 133-139 ◽  
Author(s):  
Krzysztof Banaś
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Redox Potential ◽  
Environmental Conditions ◽  
Calcium Concentration ◽  
Total Hardness ◽  
Sediment Layer ◽  
Ph Values ◽  
Doc Concentration ◽  
Good Transparency

The effect of dissolved organic carbon (DOC) on the environmental conditions of macrophytes has been studied in 35 lakes divided into soft- and hardwater: oligohumic (&lt;4.0 mg C dm<sup>-3</sup>), α-mesohumic (4.0-8.0 mg C dm<sup>-3</sup>), β-mesohumic (8.1-16.0 mg C dm<sup>-3</sup>) and polihumic (&gt;16.0 mg C dm<sup>-3</sup>). The optimum environmental conditions for macrophytes have been found in oligohumic lakes, characterised by low water colour and its good transparency. In soft- and hardwater lakes increasing concentration of DOC is accompanied with an increase in the colour (r=0.95), while the visibility decreases. With increasing DOC in the near-sediment layer the pH values decrease while the concentration of nitrogen increases and the concentration of phosphorus slightly increases. In hardwater lakes with increasing DOC concentration, the redox potential, conductivity, total hardness and calcium concentration in the near-sediment water decrease, whereas the content of CO<sup>2</sup> remains at a very low level.

Humic Colloid Generation of Transuranic Elements in Groundwater and Their Migration Behaviour

1986 ◽  
Vol 84 ◽  
Author(s):  
J.I. Kim ◽  
G. Buckau ◽  
W. Zhuang
Keyword(s):  
Heavy Metal ◽  
Humic Acid ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Metal Ions ◽  
Fulvic Acid ◽  
Photoacoustic Spectroscopy ◽  
Heavy Metal Ions ◽  
Colloidal Form ◽  
Doc Concentration

AbstractThe generation of humic colloids of Am(III) has been investigated in Gorleben groundwaters containing different amounts of humic substances. Dissolved organic carbon (DOC) in these groundwaters consists mainly of humic acid and fulvic acid, which is present in a colloidal form through aggregation with trace heavy metal ions of groundwater constituents. Concentrations of these heavy metal ions are proportional to the DOC concentration. The generation of Am(III) pseudocolloids through geochemical interactions with humic colloids in different groundwaters is quantified by ultrafiltration as well as ultracentrifugation by the aid of radiometric concentration measurements. The speciation of dissolved Am(III) species in groundwaters is carried out by laser induced photoacoustic spectroscopy (LPAS).

scholarly journals Representation of dissolved organic carbon in the JULES land surface model (vn4.4_JULES-DOCM)

2018 ◽  
Vol 11 (2) ◽  
pp. 593-609 ◽  
Author(s):  
Mahdi Nakhavali ◽  
Pierre Friedlingstein ◽  
Ronny Lauerwald ◽  
Jing Tang ◽  
Sarah Chadburn ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Land Surface ◽  
Soil Column ◽  
River System ◽  
Terrestrial Ecosystems ◽  
Surface Model ◽  
Organic C ◽  
C Cycle ◽  
Doc Concentration

Abstract. Current global models of the carbon (C) cycle consider only vertical gas exchanges between terrestrial or oceanic reservoirs and the atmosphere, thus not considering the lateral transport of carbon from the continents to the oceans. Therefore, those models implicitly consider all of the C which is not respired to the atmosphere to be stored on land and hence overestimate the land C sink capability. A model that represents the whole continuum from atmosphere to land and into the ocean would provide a better understanding of the Earth's C cycle and hence more reliable historical or future projections. A first and critical step in that direction is to include processes representing the production and export of dissolved organic carbon in soils. Here we present an original representation of dissolved organic C (DOC) processes in the Joint UK Land Environment Simulator (JULES-DOCM) that integrates a representation of DOC production in terrestrial ecosystems based on the incomplete decomposition of organic matter, DOC decomposition within the soil column, and DOC export to the river network via leaching. The model performance is evaluated in five specific sites for which observations of soil DOC concentration are available. Results show that the model is able to reproduce the DOC concentration and controlling processes, including leaching to the riverine system, which is fundamental for integrating terrestrial and aquatic ecosystems. Future work should include the fate of exported DOC in the river system as well as DIC and POC export from soil.

scholarly journals Isotopic and chromatographic fingerprinting of the sources of dissolved organic carbon in a shallow coastal aquifer

2020 ◽  
Vol 24 (4) ◽  
pp. 2167-2178 ◽  
Author(s):  
Karina T. Meredith ◽  
Andy Baker ◽  
Martin S. Andersen ◽  
Denis M. O'Carroll ◽  
Helen Rutlidge ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Coastal Aquifer ◽  
Carbon Isotopic Composition ◽  
Median Concentration ◽  
Carbon Isotopic ◽  
Groundwater Samples ◽  
Doc Concentration ◽  
Geochemical Analyses ◽  
Terrestrial Subsurface

Abstract. The terrestrial subsurface is the largest source of freshwater globally. The organic carbon contained within it and processes controlling its concentration remain largely unknown. The global median concentration of dissolved organic carbon (DOC) in groundwater is low compared to surface waters, suggesting significant processing in the subsurface. Yet the processes that remove this DOC in groundwater are not fully understood. The purpose of this study was to investigate the different sources and processes influencing DOC in a shallow anoxic coastal aquifer. Uniquely, this study combines liquid chromatography organic carbon detection with organic (δ13CDOC) carbon isotope geochemical analyses to fingerprint the various DOC sources that influence the concentration, carbon isotopic composition, and character with respect to distance from surface water sources, depth below surface, and inferred groundwater residence time (using 3H activities) in groundwater. It was found that the average groundwater DOC concentration was 5 times higher (5 mg L−1) than the global median concentration and that the concentration doubled with depth at our site, but the chromatographic character did not change significantly. The anoxic saturated conditions of the aquifer limited the rate of organic matter processing, leading to enhanced preservation and storage of the DOC sources from peats and palaeosols contained within the aquifer. All groundwater samples were more aromatic for their molecular weight in comparison to other lakes, rivers and surface marine samples studied. The destabilization or changes in hydrology, whether by anthropogenic or natural processes, could lead to the flux of up to 10 times more unreacted organic carbon from this coastal aquifer compared to deeper inland aquifers.

Sign in / Sign up

Export Citation Format

Share Document