The influence of source on the sorption of dissolved organic carbon by soils

1999 ◽  
Vol 79 (2) ◽  
pp. 321-324 ◽  
Author(s):  
T. R. Moore ◽  
L. Matos
Keyword(s):  
Humic Acid ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Partition Coefficient ◽  
Sandy Soils ◽  
Organic Soil ◽  
Solution Concentration ◽  
Null Point ◽  
Doc Concentration ◽  
Sorption Characteristics

We examined the influence of dissolved organic carbon (DOC) source on the sorption of DOC by two clayey and two sandy soils using seven extracts from plant tissues and organic soil horizons. Sorption characteristics, such as null-point DOC concentration, partition coefficient and intercept, were determined over the initial solution concentration range of 0–50 mg DOC L−1. The clayey soils had larger partition coefficients and higher null points than the sandy soils. There was an average threefold variation in null-point DOC concentration and partition coefficient amongst the seven DOC extracts. Fractionation of the DOC samples into humic acid and hydrophobic and hydrophilic acids, bases and neutrals revealed weak relationships between the sorption characteristics and DOC chemistry. Key words: Dissolved organic carbon, sorption, fractionation, humic acid, fulvic acid

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 Aspen Soils Retain More Dissolved Organic Carbon Than Conifer Soils in a Sorption Experiment

2020 ◽  
Vol 3 ◽  
Author(s):  
Antra Boča ◽  
Astrid R. Jacobson ◽  
Helga Van Miegroet
Keyword(s):  
North America ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Tree Species ◽  
Mineral Soil ◽  
Null Point ◽  
Conifer Forest ◽  
Sorption Experiment ◽  
Subalpine Fir ◽  
Doc Concentration

The effect tree species have on soil organic carbon (SOC) has been hotly debated but, so far, few clear patterns have emerged. One example of a differing tree species effect on SOC are aspen forests in North America, which have been found to have more stable SOC than adjacent conifer forest stands. An important source for the formation of stable organo-mineral complexes in soil is dissolved organic carbon (DOC). DOC concentrations in mineral soil are often higher under the thick O-horizons of conifer forests than under aspen forests, but this does not correspond to more stable mineral SOC. This suggests that, instead of DOC concentration, DOC quality could be driving the observed differences in SOC. Therefore, we quantified the retention of contrasting forest detritus DOC in soils. Using a batch sorption experiment approach, we compared the retention of detritus leachates from four sources – aspen leaves (AL), aspen roots (AR), conifer (subalpine fir) needles (CN), and conifer (subalpine fir) roots (CR) – on soils sampled under aspen and conifer (subalpine fir and Douglas fir) overstories. The calculated sorption isotherms showed a higher retention of AL DOC than AR DOC, as indicated by all four sorption parameters – k and n (curve-fitting parameters), null point concentration (NPC; net sorption = net desorption), and endpoint (EP, retention at the highest initial DOC concentration). Leachates from CN and CR showed very similar retention behavior, and between the two species the retention of root leachates was more similar than the retention of foliage leachates. Soils sampled from aspen forests showed higher affinity for new DOC than conifer soils [higher sorption rate (n), lower NPC, and higher EP] regardless of the DOC source. The findings suggest that the higher DOC sorption on aspen soils might be a major driver for more stable SOC under aspen stands in North America.

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.

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.

Dissolved organic matter from agricultural fields in the irrigation period

2005 ◽  
Vol 52 (12) ◽  
pp. 233-241 ◽  
Author(s):  
S. Shim ◽  
B. Kim ◽  
Y. Hosoi ◽  
T. Masuda
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Paddy Fields ◽  
Agricultural Fields ◽  
Uv Absorbance ◽  
Crop Fields ◽  
Irrigation Period ◽  
Doc Concentration ◽  
Specific Uv Absorbance ◽  
Hydrophobic Fraction

The aim of this study was to quantify and characterize the dissolved organic carbon (DOC) of paddy fields and crop fields in Tottori, Japan. Dissolved organic carbon (DOC) and ultraviolet (UV) absorbance was measured for the filtrated water of each samples. DOC concentration and SUVA (specific UV absorbance) of biodegradation analysis samples were determined around 50 days after the incubation. In the Fukui paddy fields, DOC concentration varied seasonally from 1.1 to 10.1mg.Cl−1, showing higher concentration in heavy runoff of non-agriculture period in April. However, DOC concentration variation did not always correspond to rainfall. The Obadake paddy fields also showed a similar pattern with Fukui paddy fields. The daily DOC discharge per area in Fukui (up), Fukui (down), Obadake (south), Obadake (north) paddy fields influent from paddy fields were 0.02, 0.0161, 0.0135 and 0.0027kg.a−1.day−1, respectively. These differences resulted from differences in agricultural types and customs of farmers according to paddy fields and fields. Also, SUVA (an indirect means to evaluate humic substances (hydrophobic fraction)) of the studied influent waters from paddy fields were generally lower than the influent waters from crop fields. The non-biodegradable DOC accounted for 50.2–98%, 46.8–85.5% of the total DOC in the paddy fields and crop fields.

Pulsed terrestrial organic carbon persists in an estuarine environment after major storm events

2020 ◽  
Author(s):  
Eero Asmala ◽  
Christopher Osburn ◽  
Ryan Paerl ◽  
Hans Paerl
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River Estuary ◽  
River Mouth ◽  
Neuse River Estuary ◽  
Storm Events ◽  
Dynamic Component ◽  
Neuse River ◽  
Doc Concentration ◽  
A Minor

&lt;p&gt;The transport of dissolved organic carbon from land to ocean is a large and dynamic component of the global carbon cycle. Export of dissolved organic carbon from watersheds is largely controlled by hydrology, and is exacerbated by increasing major rainfall and storm events, causing pulses of terrestrial dissolved organic carbon (DOC) to be shunted through rivers downstream to estuaries. Despite this increasing trend, the fate of the pulsed terrestrial DOC in estuaries remains uncertain. Here we present DOC data from 1999 to 2017 in Neuse River Estuary (NC, USA) and analyze the effect of six tropical cyclones (TC) during that period on the quantity and fate of DOC in the estuary. We find that that TCs promote a considerable increase in DOC concentration near the river mouth at the entrance to the estuary, on average an increase of 200 &amp;#181;mol l&lt;sup&gt;-1&lt;/sup&gt; due to storms was observed. TC-induced increases in DOC are apparent throughout the estuary, and the duration of these elevated DOC concentrations ranges from one month at the river mouth to over six months in lower estuary. Our results suggest that despite the fast mineralization rates, the terrestrial DOC is processed only to a minor extent relative to the pulsed amount entering the estuary. We conclude that the vast quantity of organic carbon delivered to estuaries by TCs transform estuaries from active biogeochemical processing &amp;#8220;reactors&amp;#8221; of organic carbon to appear more like passive shunts due to the sheer amount of pulsed material rapidly flushed through the estuary.&lt;/p&gt;

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

2019 ◽  
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 ◽  
Natural Processes ◽  
Median Concentration ◽  
Carbon Isotopic ◽  
Groundwater Samples ◽  
Doc Concentration ◽  
Geochemical Analyses

Abstract. The terrestrial sub-surface 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 in groundwater is low compared to surface waters suggesting significant processing in the subsurface. Yet the processes that remove this dissolved organic carbon (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 inorganic (δ13CDIC) and organic (δ13CDOC) carbon isotope geochemical analyses, to fingerprint the various DOC sources that influence the concentration, carbon isotopic composition and character with distance from surface water sources, depth below surface and groundwater residence time (using 3H) in groundwater. It was found that the average groundwater DOC concentration was five times higher (5 mg L−1) than the global median concentration and it doubled with depth, but the chromatographic character did not change significantly. The anoxic saturated conditions of the aquifer have limited the rate of organic matter processing leading to enhanced preservation and storage of the sources such as peats and palaeosols. All groundwater samples are more aromatic for their molecular weight in comparison to lakes and rivers and surface marine samples. The destabilisation or changes in hydrology, whether by anthropogenic or natural processes could lead to the flux of up to ten times more unreacted organic carbon from this coastal aquifer than compared to deeper inland aquifers.

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