Sources of Dissolved Inorganic Carbon in Two Small Streams with Different Bedrock Geology: Insights from Carbon Isotopes

Radiocarbon ◽  
2015 ◽  
Vol 57 (3) ◽  
pp. 439-448 ◽  
Author(s):  
Naoto F Ishikawa ◽  
Ichiro Tayasu ◽  
Masako Yamane ◽  
Yusuke Yokoyama ◽  
Saburo Sakai ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Carbon Cycling ◽  
Carbonate Rock ◽  
Dissolved Inorganic Carbon ◽  
Stable Carbon Isotope ◽  
The Other ◽  
Biological Degradation ◽  
Small Streams ◽  
Limestone Bedrock

Radiocarbon natural abundances (Δ14C) are being increasingly used to trace carbon cycling in stream ecosystems. To understand the ultimate sources of carbon, we determined the stable carbon isotope ratios (δ13C) and Δ14C values of dissolved inorganic and organic carbon (DIC and DOC, respectively) and of particulate organic carbon (POC) in two small streams in central Japan, one of which flows over limestone bedrock (Seri) and the other does not (Fudoji). Investigations over four seasons revealed that the Δ14C values of the DIC (from −238‰ to −174‰ for Seri and −23‰ to +10‰ for Fudoji) were less variable than those of the other carbon fractions (DOC: from −400‰ to −138‰ for Seri and −2‰ to +103‰ for Fudoji; POC: from −164‰ to −60‰ for Seri and −55‰ to +37‰ for Fudoji). Based on mass balance calculations using the δ13C and Δ14C values, the proportions of carbon in the DIC originated from (1) atmospheric CO2 were 47% to 57% for Seri and 74% to 90% for Fudoji, (2) organic matter degradation were 29% to 35% for Seri and 4% to 21% for Fudoji, and (3) carbonate rock were 14% to 22% for Seri and 4% to 6% for Fudoji. We compared the results with previous studies that had been conducted in larger rivers and showed that in small streams, the dissolution of atmospheric CO2 and weathering of carbonate rock are more important factors in the carbon cycling than the biological degradation of organic matter.

scholarly journals Radiocarbon Dating of Individual Fatty Acids as a Tool for Refining Antarctic Margin Sediment Chronologies

Radiocarbon ◽  
2003 ◽  
Vol 45 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Naohiko Ohkouchi ◽  
Timothy I Eglinton ◽  
John M Hayes
Keyword(s):  
Fatty Acids ◽  
Organic Matter ◽  
Organic Carbon ◽  
Radiocarbon Dating ◽  
Inorganic Carbon ◽  
Surface Sediments ◽  
Ross Sea ◽  
Dissolved Inorganic Carbon ◽  
Accumulation Rate ◽  
Sea Surface

We have measured the radiocarbon contents of individual, solvent-extractable, short-chain (C14, C16, and C18) fatty acids isolated from Ross Sea surface sediments. The corresponding 14C ages are equivalent to that of the post-bomb dissolved inorganic carbon (DIC) reservoir. Moreover, molecular 14C variations in surficial (upper 15 cm) sediments indicate that these compounds may prove useful for reconstructing chronologies of Antarctic margin sediments containing uncertain (and potentially variable) quantities of relict organic carbon. A preliminary molecular 14C chronology suggests that the accumulation rate of relict organic matter has not changed during the last 500 14C yr. The focus of this study is to determine the validity of compound-specific 14C analysis as a technique for reconstructing chronologies of Antarctic margin sediments.

Particulate organic matter in soil under different management systems in the Brazilian Cerrado

Soil Research ◽  
2012 ◽  
Vol 50 (8) ◽  
pp. 685 ◽  
Author(s):  
Arcângelo Loss ◽  
Marcos Gervasio Pereira ◽  
Adriano Perin ◽  
Fernando Silva Coutinho ◽  
Lúcia Helena Cunha dos Anjos
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
The Other ◽  
Management Systems ◽  
Soil Conditions ◽  
Brazilian Cerrado ◽  
Cerrado Vegetation ◽  
No Till ◽  
Planting System

The combination of the no-till planting system (NTS) and pasture (e.g. brachiaria grass, Urochloa sp.) for livestock production constitutes a crop–livestock integration (CLI) system. CLI systems significantly increase the total organic carbon (TOC) content of soil and the particulate organic carbon (POC) of soil organic matter (SOM). The present study evaluated TOC and the granulometric fractions of SOM under different management systems in a Cerrado area in the state of Goiás. Two areas applying crop rotation were evaluated, one using CLI (corn/brachiaria grass/bean/cotton/soybean planted sequentially) and the other NTS (sunflower/pearl millet/soybean/corn planted sequentially). A third area covered with natural Cerrado vegetation (Cerradão) served as a reference to determine original soil conditions. Soil was randomly sampled at 0–5, 5–10, 10–20, and 20–40 cm. The TOC, POC, and mineral-associated organic carbon (MOC) were assessed, and POC and MOC stocks calculated. The CLI system resulted in greater TOC levels than NTS (0–5, 5–10, and 10–20 cm). Compared with the Cerradão, CLI areas exhibited higher stocks of TOC (at 5–10 and 10–20 cm) and POC (at 0–40 cm). Results obtained for TOC and POC fractions show that land management with CLI was more efficient in increasing SOM than NTS. Moreover, when compared with NTS, the CLI system provided better POC stratification.

scholarly journals Chemical and physical fractions of soil organic matter under various management regimes in Roraima, Brazil

2017 ◽  
Vol 38 (4Supl1) ◽  
pp. 2419
Author(s):  
Marden Daniel Espinoza Guardiola ◽  
José Frutuoso Vale Júnior ◽  
Edmilson Evangelista da Silva ◽  
Celeste Queiroz Rossi ◽  
Marcos Gervasio Pereira
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
Chemical Elements ◽  
The Other ◽  
Management Systems ◽  
Natural Fertility ◽  
Chemical Attributes ◽  
Pasture Area ◽  
Physical And Chemical

The crop-livestock integration (CLI) and crop-livestock-forest integration (CLFI) management systems, have been shown to be viable approaches for increasing carbon sequestration in soils, resulting in the improvement of physical and chemical soil attributes. The objective of this study was to evaluate the chemical attributes and organic matter in soils under Natural Forest (NF) converted to different uses and managed differently: rotational pasture area (PAST), crop-livestock integration (CLI), and crop-livestock-forest integration (CLIF). The research was conducted at the São Paulo farm, in Iracema, located in the south-central region of the state of Roraima, Brazil. The studied soil type was classified as Ultisol. Soil samples were taken by opening ditches and examining layers at 0.1-m depth intervals from surface to 0.60-m depth. Total organic carbon (TOC), chemical and granulometric fractionation of soil organic matter (SOM), oxidizable fractions, and light organic matter in water were analyzed. Our results showed low levels of the analyzed chemical elements, a characteristic of a soil with low natural fertility. This matches conditions inherent in source material, weathered by high rainfall, a warm and humid climate, and flat topographic relief. In the 0-0.1 m layer, the PAST and CLI systems had the highest TOC contents relative to the other systems studied. At other depths, there were no statistical differences among TOC levels. The highest concentration of C in the particulate fraction (POC) was noted in the surface layer in all management systems. The pasture system had the highest concentration POC in the top 0.10 m. Our results also showed that the upper 0.10 m of soil in NF contained the lowest content of organic carbon associated with mineral (MOC) relative to the managed agrosystems. In addition, humin provided the largest contribution to SOM in all evaluated management systems. The crop-livestock integration (CLI) and crop-livestock integration forest (CLIF) systems, emerged as a strong alternative to carbon incorporation and subsequently the improvement of physical and chemical soil attributes. The objective of this work to evaluate the chemical attributes and organic matter in soils under Natural forest (NF) converted into different use and management systems: pasture (PAST), crop-livestock Integration (CLI) and crop-livestock Integration forest (CLIF). The research was conducted at São Paulo farm in Iracema, located in the Center-South region of the State of Roraima, Brazil. The soil studied was classified as Argissolo Amarelo Distrófico. The samples were taken by the opening of trenches in layers of 0-0.10, 0.10- 0.20, 0.20- 0.40, and 0.40-0.60 m depth. Total organic carbon (TOC), chemical and granulometric fractionation of soil organic matter (SOM), oxidizable fractions and organic matter in water were analyzed. The results showed low levels of the analyzed chemical elements which characterizes soils with low natural fertility, which matches the conditions of the source material, high rainfall and regional temperature, as well as the flat local relief. In the 0-0.1 m layer, the PAST and CLI systems had the highest TOC contents when compared to the other systems studied, in the other depths there were no statistical differences between the TOC levels. The highest amount of C in the particulate fraction (COp) was verified in the surface layer in all evaluated management systems. The pasture area was the system with the greatest contribution of COp to the depth of 0-0.0 m. In relation to the carbon content associated with minerals (COam), the results showed that the depth of 0-0.05 m NF area presented the lowest levels when compared to the other systems. Regarding the humic substances, there was a larger contribution of humin in all evaluated systems.

scholarly journals Presentation, calibration and validation of the low-order, DCESS Earth System Model (Version 1)

2008 ◽  
Vol 1 (1) ◽  
pp. 17-51 ◽  
Author(s):  
G. Shaffer ◽  
S. Malskær Olsen ◽  
J. O. Pepke Pedersen
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Oxygen ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
System Model ◽  
Earth System ◽  
Weathering Rates ◽  
Ocean Sediment ◽  
System Data

Abstract. A new, low-order Earth System Model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years. The atmosphere module considers radiation balance, meridional transport of heat and water vapor between low-mid latitude and high latitude zones, heat and gas exchange with the ocean and sea ice and snow cover. Gases considered are carbon dioxide and methane for all three carbon isotopes, nitrous oxide and oxygen. The ocean module has 100 m vertical resolution, carbonate chemistry and prescribed circulation and mixing. Ocean biogeochemical tracers are phosphate, dissolved oxygen, dissolved inorganic carbon for all three carbon isotopes and alkalinity. Biogenic production of particulate organic matter in the ocean surface layer depends on phosphate availability but with lower efficiency in the high latitude zone, as determined by model fit to ocean data. The calcite to organic carbon rain ratio depends on surface layer temperature. The semi-analytical, ocean sediment module considers calcium carbonate dissolution and oxic and anoxic organic matter remineralisation. The sediment is composed of calcite, non-calcite mineral and reactive organic matter. Sediment porosity profiles are related to sediment composition and a bioturbated layer of 0.1 m thickness is assumed. A sediment segment is ascribed to each ocean layer and segment area stems from observed ocean depth distributions. Sediment burial is calculated from sedimentation velocities at the base of the bioturbated layer. Bioturbation rates and oxic and anoxic remineralisation rates depend on organic carbon rain rates and dissolved oxygen concentrations. The land biosphere module considers leaves, wood, litter and soil. Net primary production depends on atmospheric carbon dioxide concentration and remineralization rates in the litter and soil are related to mean atmospheric temperatures. Methane production is a small fraction of the soil remineralization. The lithosphere module considers outgassing, weathering of carbonate and silicate rocks and weathering of rocks containing old organic carbon and phosphorus. Weathering rates are related to mean atmospheric temperatures. A pre-industrial, steady state calibration to Earth system data is carried out. Ocean observations of temperature, carbon 14, phosphate, dissolved oxygen, dissolved inorganic carbon and alkalinity constrain air-sea exchange and ocean circulation, mixing and biogeochemical parameters. Observed calcite and organic carbon distributions and inventories in the ocean sediment help constrain sediment module parameters. Carbon isotopic data and carbonate vs. silicate weathering fractions are used to estimate initial lithosphere outgassing and rock weathering rates. Model performance is tested by simulating atmospheric greenhouse gas increases, global warming and model tracer evolution for the period 1765 to 2000, as forced by prescribed anthropogenic greenhouse gas inputs and other anthropogenic and natural forcing. Long term, transient model behavior is studied with a set of 100 000 year simulations, forced by a slow, 5000 Gt C input of CO2 to the atmosphere, and with a 1.5 million year simulation, forced by a doubling of lithosphere CO2 outgassing.

scholarly journals Migration and transformation of dissolved carbon during accumulated cyanobacteria decomposition in shallow eutrophic lakes: a simulated microcosm study

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5922 ◽  
Author(s):  
Zhichun Li ◽  
Yanping Zhao ◽  
Xiaoguang Xu ◽  
Ruiming Han ◽  
Mingyue Wang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Cycling ◽  
Dissolved Inorganic Carbon ◽  
Eutrophic Lakes ◽  
Overlying Water ◽  
Dissolved Carbon ◽  
Laboratory Microcosm ◽  
Transformation Mechanisms ◽  
Diffusive Fluxes ◽  
Sediment Interface

The decomposition processes of accumulated cyanobacteria can release large amounts of organic carbon and affect the carbon cycling in shallow eutrophic lakes. However, the migration and transformation mechanisms of dissolved carbon (DC) require further study and discussion. In this study, a 73-day laboratory microcosm experiment using suction samplers (Rhizon and syringe) was conducted to understand the migration and transformation of DC during the cyanobacteria decomposition. The decomposition of cyanobacteria biomass caused anoxic and reduction conditions, and changed the acid-base environment in the water column. During the early incubation (days 0–18), a large amount of cyanobacteria-derived particulate organic matter (POM) was decomposed into dissolved organic carbon (DOC) in the overlying water, reaching the highest peak value of 1.82 g L−1 in the treatment added the high cyanobacteria biomass (470 g). After 18 days of incubation, the mineralization of increased DOC to dissolved inorganic carbon (DIC) maintained a high DIC level of overlying water in treatments added cyanobacteria biomass. The treatment added the medium cyanobacteria biomass (235 g) presented the lower DOC/total dissolved carbon ratio than the high cyanobacteria biomass associated with the lower mineralization from DOC to DIC. Due to the concentration differences of DIC at water-sediment interface, the main migration of DIC from pore water to overlying water occurred in the treatment without added cyanobacteria biomass. However, the treatments added the cyanobacteria biomass presented the obvious diffusion of DOC and the low migration of DIC at the water-sediment interface. The diffusive fluxes of DOC at the water-sediment interface increased with the cyanobacteria biomass added, reaching the maximum value of 411.01 mg/(m2·d) in the treatment added the high cyanobacteria biomass. In the overlying water, the group added the sediment and medium cyanobacteria biomass presented a faster degradation of cyanobacteria-derived POM to DOC and a higher mineralization level of DOC to DIC than added the medium cyanobacteria biomass without sediment. Therefore, during accumulated cyanobacteria decomposition, the biomass of accumulated cyanobacteria and sediment property can influence the migration and transformation of DC, playing an important role in carbon cycling in shallow eutrophic lakes.

scholarly journals Oxidizable fraction of organic carbon in an Argisol under different land use systems

CERNE ◽  
2012 ◽  
Vol 18 (2) ◽  
pp. 215-222 ◽  
Author(s):  
Caio Batista Müller ◽  
Oscarlina Lúcia dos Santos Weber ◽  
José Fernando Scaramuzza
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Soil Organic Matter ◽  
Organic Carbon ◽  
The Other ◽  
Control Treatment ◽  
Native Vegetation ◽  
Labile Carbon ◽  
Land Use Systems ◽  
Oxidizable Fraction

The objective of this study was to evaluate carbon input in labile and stable fractions in an ARGISOL of northwestern Brazil under different land use systems. Use systems being evaluated include: forest - MA (reference), agrosilvopasture - TCP (teak, cocoa and pasture); agroforest - TC (teak and cocoa); teak forest at 8 and 5 years - T8 and T5, and pasture - PA. In each system three furrows were made at depths of 0-5 cm, 5-10 cm and 10-20 cm. An area consisting of native vegetation (forest) adjacent to the experiment was sampled and used as control treatment. The use systems MA, T8 and T5 had higher levels of total organic carbon (COT) and the MA system had higher levels of labile carbon (CL) than the other systems, with the exception of TC at a depth of 10-20 cm. In the MA system, COT levels were higher in comparison to use systems TCP, TC and PA while CL levels were higher than the levels observed in use systems TCP and TC. In most cases being analyzed, CL levels were lower than COT levels, therefore this trait can be used as an indicator to assess anthropogenic changes relating to the maintenance or condition of soil organic matter.

Carbone organique: indicateur potentiel de paléoenvironnements; deux exemples

1981 ◽  
Vol 18 (12) ◽  
pp. 1838-1849 ◽  
Author(s):  
R. Bertrand ◽  
Y. Héroux
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Sedimentary Rock ◽  
Depositional Environment ◽  
Statistical Processing ◽  
Depositional Environments ◽  
The Other ◽  
Early Paleozoic

The paleoenvironment of deposition and the total organic carbon (TOC) content of two sedimentary rock sequences are studied. One has a Cenozoic age and is located on the Labrador shelf; the other is early Paleozoic and is found in the St. Lawrence Lowlands. In both sequences, variations in the paleoenvironments correspond to changes in the TOC content, despite important differences between them (age, tectonic and general paleogeographic contexts, lithologies, nature of the organic matter).A statistical processing of the data is used in order to show this parallelism between the paleoenvironment and the TOC content. In both cases, the higher the TOC content, the greater is the distance of the depositional environment from the shore. This result is in agreement with the conclusions of many other authors. This method may be very useful for detecting bathymetric variations in depositional environments, especially in monotonous sequences.

scholarly journals Organic matter sources, fluxes and greenhouse gas exchange in the Oubangui River (Congo River basin)

2012 ◽  
Vol 9 (6) ◽  
pp. 2045-2062 ◽  
Author(s):  
S. Bouillon ◽  
A. Yambélé ◽  
R. G. M. Spencer ◽  
D. P. Gillikin ◽  
P. J. Hernes ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Seasonal Variations ◽  
Dissolved Inorganic Carbon ◽  
Low Flow ◽  
Tropical Rivers ◽  
Particulate Nitrogen ◽  
Congo River

Abstract. The Oubangui is a major tributary of the Congo River, draining an area of ~500 000 km2 mainly consisting of wooded savannahs. Here, we report results of a one year long, 2-weekly sampling campaign in Bangui (Central African Republic) since March 2010 for a suite of physico-chemical and biogeochemical characteristics, including total suspended matter (TSM), bulk concentration and stable isotope composition of particulate organic carbon (POC and δ13CPOC), particulate nitrogen (PN and δ15NPN), dissolved organic carbon (DOC and δ13CDOC), dissolved inorganic carbon (DIC and δ13CDIC), dissolved greenhouse gases (CO2, CH4 and N2O), and dissolved lignin composition. δ13C signatures of both POC and DOC showed strong seasonal variations (−30.6 to −25.8‰, and −31.8 to −27.1‰, respectively), but their different timing indicates that the origins of POC and DOC may vary strongly over the hydrograph and are largely uncoupled, differing up to 6‰ in δ13C signatures. Dissolved lignin characteristics (carbon-normalised yields, cinnamyl:vanillyl phenol ratios, and vanillic acid to vanillin ratios) showed marked differences between high and low discharge conditions, consistent with major seasonal variations in the sources of dissolved organic matter. We observed a strong seasonality in pCO2, ranging between 470 ± 203 ppm for Q < 1000 m3 s−1 (n=10) to a maximum of 3750 ppm during the first stage of the rising discharge. The low POC/PN ratios, high %POC and low and variable δ13CPOC signatures during low flow conditions suggest that the majority of the POC pool during this period consists of in situ produced phytoplankton, consistent with concurrent pCO2 (partial pressure of CO2) values only slightly above and, occasionally, below atmospheric equilibrium. Water-atmosphere CO2 fluxes estimated using two independent approaches averaged 105 and 204 g C m−2 yr−1, i.e. more than an order of magnitude lower than current estimates for large tropical rivers globally. Although tropical rivers are often assumed to show much higher CO2 effluxes compared to temperate systems, we show that in situ production may be high enough to dominate the particulate organic carbon pool, and lower pCO2 values to near equilibrium values during low discharge conditions. The total annual flux of TSM, POC, PN, DOC and DIC are 2.33 Tg yr−1, 0.14 Tg C yr−1, 0.014 Tg N yr−1, 0.70 Tg C yr−1, and 0.49 Tg C yr−1, respectively. While our TSM and POC fluxes are similar to previous estimates for the Oubangui, DOC fluxes were ~30% higher and bicarbonate fluxes were ~35% lower than previous reports. DIC represented 58% of the total annual C flux, and under the assumptions that carbonate weathering represents 25% of the DIC flux and that CO2 from respiration drives chemical weathering, this flux is equivalent to ~50% of terrestrial-derived riverine C transport.

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