scholarly journals Texas A&M University Radiocarbon Dates II

Radiocarbon ◽  
1972 ◽  
Vol 14 (2) ◽  
pp. 452-455 ◽  
Author(s):  
T. D. Mathews ◽  
A. D. Fredericks ◽  
W. M. Sackett
Keyword(s):  
Organic Carbon ◽  
Gulf Of Mexico ◽  
Inorganic Carbon ◽  
Experimental Methods ◽  
Radiocarbon Dates ◽  
Seawater Samples

The radiocarbon laboratory in the Oceanography Department at Texas A&M University was established primarily for the examination of seawater samples, although other types of samples have been run. Emphasis has been placed on seawater samples of the Gulf of Mexico and adjacent areas. Most of the samples examined have been inorganic carbon, but some organic-carbon samples are being run, mainly wood and charcoal whose ages have been determined previously. More samples of known age will be run as a further check on the reliability of experimental methods and procedures.

scholarly journals Improvements in Procedural Blanks at NOSAMS: Reflections of Improvements in Sample Preparation and Accelerator Operation

Radiocarbon ◽  
1995 ◽  
Vol 37 (2) ◽  
pp. 683-691 ◽  
Author(s):  
A.P. McNichol ◽  
A. R. Gagnon ◽  
E. A. Osborne ◽  
D. L. Hutton ◽  
K.F. Von Reden ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Sample Preparation ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Carbon Powder ◽  
Ocean Sciences ◽  
Accelerator Mass Spectrometer ◽  
One Step ◽  
Available Carbon ◽  
Seawater Samples

During the four years the Sample Preparation Laboratory (SPL) at the National Ocean Sciences Accelerator Mass Spectrometer (NOSAMS) Facilty has been in operation we have accumulated much data from which we can assess our progress. We evaluate our procedural blanks here and describe modifications in our procedures that have improved our analyses of older samples. In the SPL, we convert three distinct types of samples—seawater, CaCO3 and organic carbon—to CO2 prior to preparing graphite for the accelerator and have distinct procedural blanks for each procedure. Dissolved inorganic carbon (∑CO2) is extracted from acidified seawater samples by sparging with a nitrogen carrier gas. We routinely analyze “line blanks” by processing CO2 from a 14C-dead source through the entire stripping procedure. Our hydrolysis blank, IAEA C-1, is prepared by acidifying in vacuo with 100% H3PO4 at 60° overnight, identical to our sample preparation. We use a dead graphite, NBS-21, or a commercially available carbon powder for our organic combustion blank; organic samples are combusted at 850° for 5 h using CuO to provide the oxidant. Analysis of our water stripping data suggests that one step in the procedure contributes the major portion of the line blank. At present, the contribution from the line blank has no effect on our seawater analyses (fraction modern (fm) between 0.7 and 1.2). Our hydrolysis blanks can have an fm value as low as 0.0006, but are more routinely between 0.0020 and 0.0025. The fm of our best organic combustion blanks is higher than those routinely achieved in other laboratories and we are currently altering our methods to reduce it.

scholarly journals Deforestation in Amazonia impacts riverine carbon dynamics

2016 ◽  
Vol 7 (4) ◽  
pp. 953-968 ◽  
Author(s):  
Fanny Langerwisch ◽  
Ariane Walz ◽  
Anja Rammig ◽  
Britta Tietjen ◽  
Kirsten Thonicke ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Carbon ◽  
Land Use Change ◽  
Atlantic Ocean ◽  
Amazon Basin ◽  
Inorganic Carbon ◽  
Carbon Dynamics ◽  
Model System ◽  
Atmospheric Co2 ◽  
Terrestrial Productivity

Abstract. Fluxes of organic and inorganic carbon within the Amazon basin are considerably controlled by annual flooding, which triggers the export of terrigenous organic material to the river and ultimately to the Atlantic Ocean. The amount of carbon imported to the river and the further conversion, transport and export of it depend on temperature, atmospheric CO2, terrestrial productivity and carbon storage, as well as discharge. Both terrestrial productivity and discharge are influenced by climate and land use change. The coupled LPJmL and RivCM model system (Langerwisch et al., 2016) has been applied to assess the combined impacts of climate and land use change on the Amazon riverine carbon dynamics. Vegetation dynamics (in LPJmL) as well as export and conversion of terrigenous carbon to and within the river (RivCM) are included. The model system has been applied for the years 1901 to 2099 under two deforestation scenarios and with climate forcing of three SRES emission scenarios, each for five climate models. We find that high deforestation (business-as-usual scenario) will strongly decrease (locally by up to 90 %) riverine particulate and dissolved organic carbon amount until the end of the current century. At the same time, increase in discharge leaves net carbon transport during the first decades of the century roughly unchanged only if a sufficient area is still forested. After 2050 the amount of transported carbon will decrease drastically. In contrast to that, increased temperature and atmospheric CO2 concentration determine the amount of riverine inorganic carbon stored in the Amazon basin. Higher atmospheric CO2 concentrations increase riverine inorganic carbon amount by up to 20 % (SRES A2). The changes in riverine carbon fluxes have direct effects on carbon export, either to the atmosphere via outgassing or to the Atlantic Ocean via discharge. The outgassed carbon will increase slightly in the Amazon basin, but can be regionally reduced by up to 60 % due to deforestation. The discharge of organic carbon to the ocean will be reduced by about 40 % under the most severe deforestation and climate change scenario. These changes would have local and regional consequences on the carbon balance and habitat characteristics in the Amazon basin itself as well as in the adjacent Atlantic Ocean.

scholarly journals Particulate organic carbon (POC) in relation to other pore water carbon fractions in drained and rewetted fens in Southern Germany

2008 ◽  
Vol 5 (6) ◽  
pp. 1615-1623 ◽  
Author(s):  
S. Fiedler ◽  
B. S. Höll ◽  
A. Freibauer ◽  
K. Stahr ◽  
M. Drösler ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Pore Water ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Relative Importance ◽  
Pore Waters ◽  
Calcareous Fens ◽  
Essential Components ◽  
The Individual

Abstract. Numerous studies have dealt with carbon (C) contents in Histosols, but there are no studies quantifying the relative importance of the individual C components in pore waters. For this study, measurements were taken of all the carbon components (particulate organic carbon, POC; dissolved organic carbon, DOC; dissolved inorganic carbon, DIC; dissolved methane, CH4) in the soil pore water of calcareous fens under three different water management regimes (re-wetted, deeply and moderately drained). Pore water was collected weekly or biweekly (April 2004 to April 2006) at depths between 10 and 150 cm. The main results obtained were: (1) DIC (94–280 mg C l−1) was the main C-component. (2) POC and DOC concentrations in the pore water (14–125 mg C l−1 vs. 41–95 mg C l−1) were pari passu. (3) Dissolved CH4 was the smallest C component (0.005–0.9 mg C l−1). Interestingly, about 30% of the POM particles were colonized by microbes indicating that they are active in the internal C turnover. Certainly, both POC and DOC fractions are essential components of the C budget of peatlands. Furthermore, dissolved CO2 in all forms of DIC appears to be an important part of peatland C-balance.

scholarly journals Vertical marine snow distribution in the stratified, hypersaline, and anoxic Orca Basin (Gulf of Mexico)

Elem Sci Anth ◽  
2019 ◽  
Vol 7 ◽  
Author(s):  
Arne Diercks ◽  
Kai Ziervogel ◽  
Ryan Sibert ◽  
Samantha B. Joye ◽  
Vernon Asper ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Gulf Of Mexico ◽  
Particle Number ◽  
Sea Surface ◽  
Marine Snow ◽  
Particle Volume ◽  
Total Particle Number ◽  
Total Particle ◽  
Snow Distribution ◽  
Orca Basin

We present a complete description of the depth distribution of marine snow in Orca Basin (Gulf of Mexico), from sea surface through the pycnocline to within 10 m of the seafloor. Orca Basin is an intriguing location for studying marine snow because of its unique geological and hydrographic setting: the deepest ~200 m of the basin are filled with anoxic hypersaline brine. A typical deep ocean profile of marine snow distribution was observed from the sea surface to the pycnocline, namely a surface maximum in total particle number and midwater minimum. However, instead of a nepheloid (particle-rich) layer positioned near the seabed, the nepheloid layer in the Orca Basin was positioned atop the brine. Within the brine, the total particle volume increased by a factor of 2–3 while the total particle number decreased, indicating accumulation and aggregation of material in the brine. From these observations we infer increased residence time and retention of material within the brine, which agrees well with laboratory results showing a 2.2–3.5-fold reduction in settling speed of laboratory-generated marine snow below the seawater-brine interface. Similarly, dissolved organic carbon concentration in the brine correlated positively with measured colored dissolved organic matter (r2 = 0.92, n = 15), with both variables following total particle volume inversely through the pycnocline. These data indicate the release of dissolved organic carbon concomitant with loss in total particle volume and increase in particle numbers at the brine-seawater interface, highlighting the importance of the Orca Basin as a carbon sink.

A Syringe Gas-Stripping Procedure for Gas-Chromatographic Determination of Dissolved Inorganic and Organic Carbon in Fresh Water and Carbonates in Sediments

1973 ◽  
Vol 30 (10) ◽  
pp. 1441-1445 ◽  
Author(s):  
Michael P. Stainton
Keyword(s):  
Organic Carbon ◽  
Gas Phase ◽  
Atmospheric Pressure ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Chromatographic Determination ◽  
Canadian Shield ◽  
Gas Stripping ◽  
Inorganic And Organic

A simple, rapid method for determining dissolved inorganic carbon in water is described. A 20-cm3 sample of water is drawn into a 50-cm3 polypropylene syringe and acidified by injection of 1 cm3 of dilute sulphuric acid. Twenty-nine cubic centimeters of helium at atmospheric pressure is injected into the syringe followed by 10 sec of manual agitation to partition CO2 between gas and liquid phase. The gas phase containing 60% of CO2 from the sample is then analyzed by gas chromatography. This method has been used to determine dissolved inorganic and organic carbon in Canadian Shield waters and to determine total carbonates in sediments.

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.

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