Influence of seasonal changes in runoff and extreme events on dissolved organic carbon trends in wetland- and upland-draining streams

2008 ◽  
Vol 65 (5) ◽  
pp. 796-808 ◽  
Author(s):  
M Catherine Eimers ◽  
Jim Buttle ◽  
Shaun A Watmough
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Extreme Events ◽  
Seasonal Pattern ◽  
South Central ◽  
Doc Export ◽  
Doc Concentration ◽  
Spring Flow ◽  
Doc Load ◽  
Headwater Basins

Dissolved organic carbon (DOC) fluxes at eight headwater basins in south-central Ontario were strongly related to seasonal streamflow, and extreme events contributed to both interannual and intercatchment variability. Six catchments with high stream DOC and greater peatland coverage exhibited a different seasonal pattern of DOC concentration compared with two catchments with low DOC and less wetland influence. In wetland-dominated catchments, DOC concentrations decreased during fall wet-up and spring melt, and because of the dominance of the spring melt period in annual budgets, variations in spring flow explained 39%–48% of the intervariability in DOC concentration. Significant increases in average DOC concentration between 1980 and 2001 at all six wetland-dominated catchments were driven by relatively high DOC concentrations in the latter years of record, consistent with low spring flow in these years, and were not translated into greater DOC export to downstream lakes. Localized rainstorms in summer and fall resulted in differences in DOC export among adjacent catchments, and a single fall storm in September 1998 was only detected at one of six catchments draining into Harp Lake but accounted for one-quarter of the annual tributary DOC load to the lake.

scholarly journals Dissolved organic carbon concentrations vary with season and land use – investigations from two fens in Northeastern Germany over two years

2014 ◽  
Vol 11 (5) ◽  
pp. 7079-7111 ◽  
Author(s):  
M. Schwalm ◽  
J. Zeitz
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Environmental Concern ◽  
Doc Export ◽  
Doc Concentration ◽  
Agricultural Use ◽  
Northeastern Germany ◽  
Carbon Concentrations ◽  
Discharge Measurements

Abstract. The rising export of dissolved organic carbon (DOC) from peatlands during the last 20 years is of great environmental concern, as DOC harms drinking water quality and diminishes the carbon storage of peatlands. Lack of knowledge particularly exists for fens. The aim of our study was to determine DOC concentrations at an agriculturally used fen and a rewetted fen throughout the year. We measured DOC concentrations in ditch water of these fens in 2011 and 2012. Furthermore, discharge measurements were condcucted to detect DOC export. Overall DOC concentrations at our agriculturally used site and at our rewetted site were 35 mg L−1 and 26 mg L−1 (median), respectively. The maximum DOC concentration at our agriculturally used site was twice as high as at the rewetted site (134 mg L−1 vs. 61 mg L−1). Annual DOC export was calculated for the rewetted site, amounting to 200 kg C ha−1 on average. Our results suggest that rewetting of degraded fens reduces DOC export in the long-term, while agricultural use of fens leads to enhanced decomposition and thus, elevates DOC export.

Can tributary in-flows improve the recovery of the dissolved organic carbon regime in a snowmelt river regulated by a large reservoir?

2016 ◽  
Vol 67 (9) ◽  
pp. 1338 ◽  
Author(s):  
Ann-Marie Rohlfs ◽  
Simon M. Mitrovic ◽  
Simon Williams ◽  
Daniel Coleman
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River System ◽  
Main Stem ◽  
Water Diversion ◽  
Regulated River ◽  
Regulated Rivers ◽  
Large Reservoir ◽  
Doc Export ◽  
Doc Concentration

Although tributary inputs can accelerate the recovery of many physical and chemical gradients below large reservoirs, their contribution to the dissolved organic carbon (DOC) regime in regulated rivers remains poorly studied. In some regulated tributaries, flow volumes can be manipulated, potentially influencing DOC supply to the main stem. The present study examines how tributary water diversion affects DOC supply to a snowmelt river regulated by large reservoirs. DOC concentration was measured at tributary and main stem sites, and tributary DOC export was estimated under different tributary flow-diversion scenarios. Significant, positive correlations between DOC concentration and discharge were absent directly below the dam, but were present in the unregulated tributary, and re-emerged below the tributary confluence. Irrespective of water-diversion practices, tributary in-flows reconnected the regulated main stem to a more variable DOC regime driven by catchment flushing processes. However, tributary water diversion dampened the tributary signal by reducing DOC pulse frequency and total DOC export to the regulated river. These aspects of the DOC regime may influence basal resource availability and ecosystem functioning in the regulated main stem. The present study illustrates how an ecologically valuable tributary function can be addressed and quantified to guide the management and rehabilitation of a regulated river system.

scholarly journals Dissolved Organic Carbon Driven by Rainfall Events from a Semi-arid Catchment during Concentrated Rainfall Season in the Loess Plateau, China

2019 ◽  
Author(s):  
Linhua Wang ◽  
Haw Yen ◽  
Xinhui E ◽  
Liding Chen ◽  
Yafeng Wang
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
The Loess Plateau ◽  
Rainfall Season ◽  
Doc Export ◽  
Doc Concentration ◽  
Doc Flux ◽  
Event Based ◽  
Runoff Discharge ◽  
Semi Arid

Abstract. Dissolved organic carbon (DOC) transported by surface runoff has been identified as an important role of the global carbon cycle. Despite there being many studies on DOC concentration and flux, but little information is available in semi-arid catchments of the Loess Plateau Region (LPR). The primary goal of this study was to quantify DOC exported from a sequence of runoff events during the concentrated rainfall season. In addition, factors that affect DOC export from a small headwater catchment will be investigated accordingly. Runoff discharge and DOC concentration were monitored at the outlet of the Yangjuangou catchment in Yanan, Shaanxi Province, China. The results showed that DOC concentration was highly variable (1.91–34.70 mg L−1), with event-based DOC concentrations ranging from 4.08 to 15.66 mg L−1. The mean monthly DOC flux loading from the catchment was 94.73–110.17 kg km−2 from June to September, while the event-based DOC flux ranged from 0.08 to 2.81 kg km−2. Intra-events of rainfall amount and runoff discharge led to event-based/monthly differences in DOC concentration and flux. Hysteresis analysis showed a nonlinear relationship between DOC concentration and discharge in the runoff process. Our results highlighted the advantages of high-frequency monitoring for DOC export and indicated that DOC export from a catchment is largely influenced by the interaction of rainfall and antecedent conditions for a rainfall event. Engineering and scientists can take advantage of the derived results to better develop advanced field monitoring work. In addition, release of DOC runoff can take quantified during hydrological and biogeochemical processes within catchments in LPR.

Effect of pH and Dissolved Organic Carbon on the Toxicity of Copper to Larval Fathead Minnow (Pimephales promelas) in Natural Lake Waters of Low Alkalinity

1993 ◽  
Vol 50 (7) ◽  
pp. 1356-1362 ◽  
Author(s):  
P. G. Welsh ◽  
J. F. Skidmore ◽  
D. J. Spry ◽  
D. G. Dixon ◽  
P. V. Hodson ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Fathead Minnow ◽  
Pimephales Promelas ◽  
Multiple Regression Model ◽  
Aquatic Life ◽  
South Central ◽  
Doc Concentration ◽  
Current Water ◽  
Ph Range

The impacts of pH and dissolved organic carbon (DOC) on the acute toxicity of Cu to larval fathead minnow (Pimephales promelas) were determined using natural soft water from two Precambrian Shield lakes in south-central Ontario. By artificially manipulating the pH and DOC levels of the water, we demonstrated that both acidification and the removal of DOC increased the toxicity of Cu. The 96-h Cu LC50s were determined over a pH range from 5.4 to 7.3 and a DOC concentration range from 0.2 to 16 mg∙L−1. The LC50s ranged from a low of 2 μg∙L−1 (pH 5.6, DOC 0.2 mg∙L−1) to a high of 182 μg∙L−1 (pH 6.9, DOC 15.6 mg∙L−1). A multiple regression model (log1096-h Cu LC50 = −0.308 + 0.192 pH + 0.136 (pH∙log10DOC)) was used to describe the relationship between Cu toxicity, pH, and DOC. The model was significant (p < 0.00001) and explained 93% of the variability in the toxicity data. These results suggest that current water quality objectives for Cu, and possibly for other metals, may not be sufficiently protective of aquatic life in soft, moderately acidic water containing low levels of DOC.

scholarly journals Landscape controls on riverine export of dissolved organic carbon from Great Britain

2021 ◽  
Author(s):  
Jennifer L. Williamson ◽  
Andrew Tye ◽  
Dan J. Lapworth ◽  
Don Monteith ◽  
Richard Sanders ◽  
...  
Keyword(s):  
Land Use ◽  
Great Britain ◽  
Population Density ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Forest Cover ◽  
River Systems ◽  
C Cycle ◽  
Global Land ◽  
Doc Export

AbstractThe dissolved organic carbon (DOC) export from land to ocean via rivers is a significant term in the global C cycle, and has been modified in many areas by human activity. DOC exports from large global rivers are fairly well quantified, but those from smaller river systems, including those draining oceanic regions, are generally under-represented in global syntheses. Given that these regions typically have high runoff and high peat cover, they may exert a disproportionate influence on the global land–ocean DOC export. Here we describe a comprehensive new assessment of the annual riverine DOC export to estuaries across the island of Great Britain (GB), which spans the latitude range 50–60° N with strong spatial gradients of topography, soils, rainfall, land use and population density. DOC yields (export per unit area) were positively related to and best predicted by rainfall, peat extent and forest cover, but relatively insensitive to population density or agricultural development. Based on an empirical relationship with land use and rainfall we estimate that the DOC export from the GB land area to the freshwater-seawater interface was 1.15 Tg C year−1 in 2017. The average yield for GB rivers is 5.04 g C m−2 year−1, higher than most of the world’s major rivers, including those of the humid tropics and Arctic, supporting the conclusion that under-representation of smaller river systems draining peat-rich areas could lead to under-estimation of the global land–ocean DOC export. The main anthropogenic factor influencing the spatial distribution of GB DOC exports appears to be upland conifer plantation forestry, which is estimated to have raised the overall DOC export by 0.168 Tg C year−1. This is equivalent to 15% of the estimated current rate of net CO2 uptake by British forests. With the UK and many other countries seeking to expand plantation forest cover for climate change mitigation, this ‘leak in the ecosystem’ should be incorporated in future assessments of the CO2 sequestration potential of forest planting strategies.

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.

Application of Dissolved Organic Carbon Runoff Model Considering Soil Infiltration and River Runoff Processes in Multiple Forested Watersheds

2021 ◽  
Author(s):  
Kazunori Ebata ◽  
Yutaka Ichikawa ◽  
Hiroshi Ishidaira ◽  
Yoshitaka Matsumoto ◽  
Kei Nishida
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Transport Processes ◽  
Subsurface Water ◽  
Short Time Scale ◽  
Seasonal Temperature ◽  
Soil System ◽  
System A ◽  
Monsoon Area ◽  
Doc Load

&lt;p&gt;Estimation of dissolved organic carbon (DOC) runoff load in forested watershed is important for the assessment of the global carbon cycle as well as for the control of regional water environments. A few process-based models have been proposed to estimate the DOC load to water environments, which assume DOC source in topsoil and transport processes to the river, however, these models exhibited difficulties with the availability of input data and applicability to short time-scale rainfall-runoff processes in the Asian monsoon area. This study presents a new process-based model that consists of two separate systems for determining DOC load enforced by DOC Source Area (DSA) concept. For the runoff system, a semi-distributed hydrological modelling unit (&amp;#8216;modified-TOPMODEL&amp;#8217;) was installed, by which surface and subsurface water flows, representing for DSA, were sequentially simulated. For the soil system, a wet-dry cycle was successfully simulated by an advection-diffusion and dissolution formulation as well as seasonal temperature effect. The model is first evaluated upstream (98ha) and downstream (1798ha) in the Mizugaki Watershed, Yamanashi, Japan and then applied for a Miuchi (203ha) watershed, Aichi, Japan during 2014 to 2018. The results of cumulative DOC load at baseflow and stormflow periods that the model performed well between the simulations and observations for both study sites. Considering the stormflow periods, from 25.2% to 32.0%, and 31.1% of high flows contributed to 50% of the total DOC load at Mizugaki and Miuchi watershed, respectively. Overall, the proposed model successfully simulated DOC load under different geochemical and hydrological condition by capturing the DSA variability.&lt;/p&gt;

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).

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