scholarly journals Sources and fate of terrestrial dissolved organic carbon in lakes of a Boreal Plains region recently affected by wildfire

2013 ◽  
Vol 10 (4) ◽  
pp. 6093-6141 ◽  
Author(s):  
D. Olefeldt ◽  
K. J. Devito ◽  
M. R. Turetsky
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Productivity ◽  
Fulvic Acids ◽  
Lake Morphometry ◽  
Humic And Fulvic Acids ◽  
Study Region ◽  
Boreal Plains ◽  
Peat Pore Water ◽  
Surface Geology

Abstract. Downstream mineralization and sedimentation of terrestrial dissolved organic carbon (DOC) render lakes important for landscape carbon cycling in the boreal region, with regulating processes potentially sensitive to perturbations associated with climate change including increased occurrence of wildfire. In this study we assessed chemical composition and reactivity (during both dark and UV incubations) of DOC from lakes and terrestrial sources within a peatland-rich western boreal plains region partially affected by a recent wildfire. While wildfire was found to increase aromaticity of DOC in peat pore-water above the water table, it had no effect on concentrations or composition of DOC from peatland wells and neither affected mineral well or lake DOC characteristics. Lake DOC composition reflected a mixing of peatland and mineral groundwater, with a greater influence of mineral sources to lakes in coarse- than fine-textured settings. Peatland DOC was less biodegradable than mineral DOC, but both mineralization and sedimentation of peatland DOC increased substantially during UV incubations through selective removal of aromatic humic and fulvic acids. DOC composition in lakes with longer residence times had characteristics consistent with increased UV-mediated processing. We estimate that about half of terrestrial DOC inputs had been lost within lakes, mostly due to UV-mediated processes. The importance of within-lake losses of aromatic DOC from peatland sources through UV-mediated processes indicate that terrestrial-aquatic C linkages in the study region are largely disconnected from recent terrestrial primary productivity. Together, our results suggest that characteristics of the study region (climate, surface geology and lake morphometry) render linkages between terrestrial and aquatic C cycling insensitive to the effects of wildfire by determining dominant terrestrial sources and within-lake processes of DOC removal.

scholarly journals Sources and fate of terrestrial dissolved organic carbon in lakes of a Boreal Plains region recently affected by wildfire

2013 ◽  
Vol 10 (10) ◽  
pp. 6247-6265 ◽  
Author(s):  
D. Olefeldt ◽  
K. J. Devito ◽  
M. R. Turetsky
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Mineral Soil ◽  
Terrestrial Ecosystems ◽  
Fulvic Acids ◽  
Mixing Model ◽  
Selective Removal ◽  
Boreal Plains ◽  
Peat Pore Water ◽  
Surface Geology

Abstract. Downstream mineralization and sedimentation of terrestrial dissolved organic carbon (DOC) render lakes important for landscape carbon cycling in the boreal region. The chemical composition of terrestrial DOC, the downstream delivery of terrestrial DOC and its processing within aquatic ecosystem may all be influenced by climate change, including increased occurrence of wildfire. Here, we assessed composition and lability (during both dark- and UV incubations) of DOC from peatland groundwater and mineral soil groundwater, and from shallow lakes within a peatland-rich region on the Boreal Plains of western Canada that was recently affected by wildfire. Wildfire was found to increase aromaticity of DOC in peat pore water above the water table, but had no effect on the concentrations or composition of peatland groundwater DOC or mineral soil DOC. Using a mixing model we estimated that on average 98 and 78% of terrestrial DOC inputs to the lakes in fine- and coarse-textured settings, respectively, originated from peatland groundwater sources. Accordingly, lake DOC composition reflected primarily a mixing of peatland and mineral soil groundwater sources, with no detectable influence of the recent wildfire. Lake and peatland DOC had low biodegradability, lower than that of mineral soil DOC. However, both mineralization and sedimentation of peatland DOC increased substantially during UV incubations through selective removal of aromatic humic and fulvic acids. Similar shifts in DOC composition as observed during the UV incubations were also observed across lakes with longer water residence times. The mixing model estimated that on average 54% (95% confidence interval: 36–64%) of terrestrial DOC had been removed in lakes as a result of mineralization and sedimentation. Meanwhile, the reduction in absorbance at 254 nm was 71% (58–76%), which suggests selective removal of aromatic DOC. Hence, incubation results, patterns of DOC composition among lakes and mixing model results were consistent with significant within-lake removal of terrestrial DOC through UV-mediated processes. Selective removal of highly aromatic DOC through UV-mediated processes implies that organic sources that are considered stabile in terrestrial ecosystems can be readily mineralized once entering aquatic ecosystems. Together, our results suggest that regional characteristics (climate, surface geology and lake morphometry) can prevent wildfire from causing pulse perturbations to the linkages between terrestrial and aquatic C cycling and also regulate the processes that dominate within-lake removal of terrestrial DOC.

scholarly journals New possibility for characterization of dissociation behaviour of supramolecular electrolytes: results obtained for the International Humic Substances Society standard and reference samples by coulometry

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Martina Klučáková
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Humic Substances ◽  
Functional Groups ◽  
Dissociation Constants ◽  
Fulvic Acids ◽  
Molecular Organization ◽  
Humic And Fulvic Acids ◽  
Acid Base ◽  
Reference Samples

Abstract Background Humic substances can be considered as polyelectrolytes with supramolecular character and complicated behaviour in water environment. The fractions of humic substances dissolved in water are the most active ones and determinative for their functioning in nature, where the proton-binding and dissociation ability play a crucial role. The dissociation behaviour of humic and fulvic acids can be affected by different circumstances including their concentration which is directly connected with the molecular organization of humic particles in solution and the accessibility of their ionizable functional groups. This study is focused just on these active fractions and their dissociation behaviour in the dependence on their content in studied system. Results Standards and reference samples of International Humic Substances Society were used. Flow-through coulometry was used to determine the total content of acidic functional groups in fulvic solutions and humic leachates. The amount of dissociated acidic groups was determined on the basis of potentiometry. Several differences between the behaviour of humic and fulvic acids were found. While whole samples of fulvic acids including the weakest functional groups were analysed, only the active dissolved humic fractions containing stronger acidic functional groups were characterized. The fractions containing higher amounts of the weakest functional groups remained insoluble. The dissociation degree of fulvic acids decreased with their increasing content, but a maximum on its concentration dependence obtained for humic acids was observed. Conclusions Two different values of dissociation constants were determined for each sample. The first was determined on the basis of the extrapolation of infinite dilution, second was determined as their average value in the region of high concentrations in which it was constant. Obtained values characterize the functioning of dissolved humic substances from point of view of their dissociation ability. The results obtained by this approach can help to predict the acid–base behaviour of dissolved organic carbon in soil and generally in nature. The acid–base behaviour of dissolved organic carbon depends on its ratio to water. It behaves differently in soil which is dry and in soil which is wet or saturated by water.

Carbon Flow in a Tundra Stream Ecosystem

1986 ◽  
Vol 43 (6) ◽  
pp. 1259-1270 ◽  
Author(s):  
Bruce J. Peterson ◽  
John E. Hobbie ◽  
Teresa L. Corliss
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Productivity ◽  
Net Primary Production ◽  
Epilithic Algae ◽  
Net Production ◽  
Organic Carbon Concentration ◽  
Temperate Streams ◽  
Tundra Vegetation ◽  
Order Of Magnitude

The carbon cycle of the Kuparuk River, a meandering tundra stream, is dominated by inputs of eroding peat and leaching dissolved organic carbon from the tundra. Net production of epilithic algae is about 13 g C∙m−2∙yr−1, an order of magnitude less than inputs of allochthonous particulate organic carbon and two orders of magnitude less than inputs of dissolved organic carbon. The streamwater has a mean total organic carbon concentration of 6.8 mg∙L−1, and the annual export of organic carbon from the watershed is 2–3 t∙km−2∙yr−1; both are similar to the average for temperate streams. However, because of the low primary productivity of tundra vegetation, the export of organic carbon from the watershed via the river is a larger fraction (2–6%) of the total watershed net primary production than the 0.1–0.4% usually found for temperate rivers.

scholarly journals Hydrological processes and permafrost regulate magnitude, source and chemical characteristics of dissolved organic carbon export in a peatland catchment of northeastern China

2017 ◽  
Author(s):  
Yuedong Guo ◽  
Changchun Song ◽  
Wenwen Tan ◽  
Xianwei Wang ◽  
Yongzheng Lu
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Climate Warming ◽  
Northeastern China ◽  
Organic Layer ◽  
Chemical Characteristics ◽  
Carbon Export ◽  
Study Region ◽  
Growing Seasons ◽  
Doc Export

Abstract. Permafrost thawing in peatland has the potential to alter the catchment export of dissolved organic carbon (DOC), thus influencing carbon cycling in linked aquatic and ocean ecosystems. However, peatland along the southern margins of Eurasian permafrost are seldom examined in spite of the presence of considerable risks associated with degradation due to climate warming. This study examines dynamics of DOC export from a permafrost peatland catchment located in northeastern China during the growing seasons of 2012 to 2014. Our findings show that runoff processes affect observed DOC concentrations, magnitudes, sources, and chemical characteristics of stream discharge. The entire catchment exhibits strong potential for annual DOC exporting (4.87 g C m−2), and DOC from the peatland landscape alone is estimated to amount to 12.89 g C m−2. Annual DOC export processes are closely related to total discharge levels, and floods contribute to approximately 85 % of DOC export levels. Flood volumes derived mainly from peat pore water stored in the upper organic layer of the soil profile prior to rainfall events, creating a strong linkage between discharge and DOC concentrations. DOC source and chemical characteristics, as indicated by three fluorescence indexes, have changed regularly according to source shifts occurring as a result of flood and baseflow processes. A deepening of the active layer due to climate warming should elevate proportions of microbial-originated DOC in the baseflow. Given expected future increases in precipitation, our results show that the magnitude of DOC exports from the study region will increase.

Bioavailability of dissolved organic carbon and fulvic acid from an Australian floodplain river and billabong

2007 ◽  
Vol 58 (2) ◽  
pp. 222 ◽  
Author(s):  
Suzanne McDonald ◽  
Jennifer M. Pringle ◽  
Paul D. Prenzler ◽  
Andrea G. Bishop ◽  
Kevin Robards
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Fulvic Acid ◽  
Heterotrophic Bacteria ◽  
Fulvic Acids ◽  
Lag Phase ◽  
Floodplain Ecosystems ◽  
Vital Resource ◽  
Number Of Bacteria

Dissolved organic carbon (DOC) is a vital resource for heterotrophic bacteria in aquatic ecosystems. The bioavailability of fulvic acid, which comprises the majority of aquatic DOC, is not well understood. The present study examined the bioavailability of bulk DOC and fulvic acid from two contrasting but inter-related water bodies: the Murrumbidgee River and adjacent Berry Jerry Lagoon. Bacteria utilised fulvic acids; however, bulk DOC was more bioavailable. Bacteria were able to utilise Murrumbidgee River DOC and fulvic acid more readily than Berry Jerry Lagoon DOC and fulvic acid, suggesting that the quality of carbon may be an important factor to consider when evaluating lateral exchange of nutrients between the main channel and floodplain. Chemical characteristics of fulvic acids appeared to explain some of the variation in fulvic acid bioavailability. The higher the molecular weight and complexity of the fulvic acid, the longer it took for bacteria to utilise the substrate (lag phase), but the larger the number of bacteria that grew on the substrate. The present study calls attention to the need for further multidisciplinary studies to address the quality of carbon in riverine-floodplain ecosystems.

Climatology and trends of Dissolved Organic Carbon in coastal waters off Sarawak, Borneo

2020 ◽  
Author(s):  
Nivedita Sanwlani ◽  
Patrick Martin ◽  
Nagur Cherukuru ◽  
Moritz Muller ◽  
Christopher Evans
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Coastal Waters ◽  
Distribution Patterns ◽  
Northeast Monsoon ◽  
Study Region ◽  
South West Monsoon ◽  
Ocean Carbon ◽  
Carbon Store

<p>South-East Asian peatlands are a globally significant carbon store. Rivers draining these peatlands have some of the highest dissolved organic carbon (DOC) concentrations in the world and account for up to 10% of the global land-to-ocean carbon flux, thus representing an important input to the marine carbon cycle. The release of DOC from peatlands is a natural process, yet the rapid and extensive transformation of these peatlands for agriculture over the past two decades is thought to have increased fluvial carbon losses significantly. However, not only do we lack a firm understanding of the fate of this terrigenous DOC in tropical seas, the distribution and long-term variability in DOC have never been studied at large scales in SE Asia. We will present the seasonal climatology (2002-2018) of spatial distribution patterns of DOC concentrations and optical properties (absorption coefficients, spectral slope) of colored dissolved organic matter (CDOM) for coastal waters of Sarawak, Malaysian Borneo derived using a regionally tailored semi-analytical inversion model from MODIS Aqua. Our results reveal substantial inputs of DOC from Sarawak rivers DOC close to shore exceeds 125 µM, and CDOM across the study region shows predominantly terrigenous spectral signatures. DOC concentrations were higher during the rainier northeast monsoon than during the drier south-west monsoon. Our data suggest that long-term increases in DOC concentration have occurred across parts of our study region from 2002–2018, which has implications for the aquatic light regime and coastal biogeochemistry[PM5]. These results will be discussed in the context of past anthropogenic disturbance to coastal peatlands.</p>

scholarly journals Changes in Water-Extractable Organic Carbon with Cover Crop Planting under Continuous Corn Silage Production

2016 ◽  
Vol 9 ◽  
pp. ASWR.S30708 ◽  
Author(s):  
Brian D. Grebliunas ◽  
Shalamar D. Armstrong ◽  
William L. Perry
Keyword(s):  
Organic Carbon ◽  
Cover Crops ◽  
Cover Crop ◽  
Agricultural Soils ◽  
Fulvic Acids ◽  
Humic And Fulvic Acids ◽  
Labile Carbon ◽  
Water Extractable Organic Carbon ◽  
Parallel Factor ◽  
Water Extractable

Long-term row crop agricultural production has dramatically reduced the pool of soil organic carbon. The implementation of cover crops in Midwestern agroecosystems is primarily to reduce losses of nitrogenous fertilizers, but has also been shown to restore soil carbon stocks over time. If labile carbon within agricultural soils could be increased, it could improve soil health, and if mobilized into subsurface drainage, it may positively impact watershed biogeochemistry. We tested for potential differences in water-extractable organic carbon (WEOC) at two different soil profiles (0-5 cm and 5-20 cm) between plots planted with cereal rye/daikon radish (cover crop), corn, and zero control (no vegetation) within the Illinois State University Research and Teaching Farm. We also tested for potential differences in denitrification within the upper soil profile throughout the growing year. We modeled excitation–emission matrices from soil cores through parallel factor analysis. We found no difference in WEOC concentrations between each crop treatment ( P = 0.2850), but concentrations of WEOC were significantly lower in the 5-20 cm profile than that in the upper (0-5 cm) profile ( P = 0.0033). There was a significant increase in WEOC after each treatment in samples after cover crop termination. The parallel factor analysis model found humic and fulvic acids to be the dominant fractions of WEOC in all soils tested. Humic and fulvic acids accounted for ~70% and 30% of model variation. Denitrification rates did not differ across treatments ( P = 0.3520), which is likely attributed to soil WEOC being in limiting quantities and in primarily recalcitrant fractions. After three years, cover crops do not appear to alter soil WEOC quantity and type. Restoring the availability of carbon within agricultural soils will not be a short-term fix, and fields will likely be a net carbon sink, contributing minimal labile carbon to receiving waterways.

scholarly journals An integrated Dissolved Organic Carbon Dynamics Model (DOCDM 1.0): model development and a case study in the Alaskan Yukon River Basin

2015 ◽  
Vol 8 (12) ◽  
pp. 10411-10454 ◽  
Author(s):  
X. Lu ◽  
Q. Zhuang
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Overland Flow ◽  
Terrestrial Ecosystems ◽  
Carbon Dynamics ◽  
Water Infiltration ◽  
Dynamics Model ◽  
Study Region ◽  
Doc Export ◽  
Doc Production

Abstract. Quantitative understanding of the variation in dissolved organic carbon (DOC) is important to studying the terrestrial ecosystem carbon cycle. This study presents a process-based, dissolved organic carbon dynamics model (DOCDM 1.0) that couples the soil heat conduction, water flow, DOC production, mineralization and transport in both surface and subsurface of soil profile to quantify DOC dynamics in boreal terrestrial ecosystems. The model is first evaluated and then applied for a watershed in Alaska to investigate its DOC production and transport. We find that 42 and 27 % of precipitation infiltrates to soils in 2004, a warmer year, and in 1976, a colder year, respectively. Under warming conditions, DOC transported via overland flow does not show the expected decrease trend while the overland DOC yield shows a 4 % increase. The horizontal subsurface flow only accounts for 1–2 % of total water flux, but transports 30–50 % of DOC into rivers. Water flush due to water infiltration controls DOC transport. Snowmelt plays a noticeable role in DOC flush-out and DOC transport significantly depends on flowpaths in the study region. High soil temperature stimulates DOC production. The overland DOC export does not necessarily follow the DOC downward trend in surface water transport. Overall, this study shows that DOC export behavior is complex under changing temperature and hydrological conditions in cold-region watersheds. To adequately quantify DOC dynamics in northern high latitudes, more DOC and hydrological data are needed to better parameterize and test the developed model before extrapolating it to the region.

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