Mg Of Organic Carbon Research Articles

Microgram level radiocarbon (14C) determination on carbonaceous particles in ice

In climate research the interest on carbonaceous particles has increased over the last years because of their influence on the radiation balance of the earth. Nevertheless, there is a paucity of available data regarding their concentrations and sources in the past. Such data would be important for a better understanding of their effects and for estimating their influence on future climate. Here, a technique is described to extract carbonaceous particles from ice core samples with subsequent separation of the two main constituents into organic carbon (OC) and elemental carbon (EC) for analysis of their concentrations in the past. This is combined with further analysis of OC and EC 14C/12C ratios by accelerator mass spectrometry (AMS), what can be used for source apportionment studies of past emissions. We further present how 14C analysis of the OC fraction could be used in the future to date any ice core extracted from a high-elevation glacier. Described sample preparation steps to final analysis include the combustion of micrograms of water–insoluble carbonaceous particles, primary collected by filtration of melted ice samples, the graphitisation of the obtained CO2 to solid AMS target material and final AMS measurements. Possible fractionation processes were investigated for quality assurance. Procedural blanks were reproducible and resulted in carbon masses of 1.3±0.6μg OC and 0.3±0.1μg EC per filter. The determined fraction of modern carbon (fM) for the OC blank was 0.61±0.13. The analysis of processed IAEA-C6 and IAEA-C7 reference material resulted in fM=1.521±0.011 and δ13C=−10.85±0.19‰, and fM=0.505±0.011 and δ13C=−14.21±0.19‰, respectively, in agreement with consensus values. Initial carbon contents were thereby recovered with an average yield of 93%.

Composition and distribution of meiofauna, including nematode genera, in two contrasting Arctic beaches

The meiofauna of two tidal beaches, one exposed and one more sheltered, on Bjornoya (Bear Island) was investigated in summer 2000. Both meiofaunal densities and composition seem to be controlled by physical properties of the sediment, which in turn are controlled by exposure. The moderately and poorly sorted sediments in the sheltered beach were more abundant in terms of meiofaunal densities than the well sorted sediments in the exposed beach (254–481 individuals in 10 cm2 vs 7–269 individuals in 10 cm2, respectively). In total, seven higher meiofaunal taxa were found. Turbellaria were the numerically dominant taxon in the exposed beach. In the sheltered beach, Turbellaria also dominated, followed by Nematoda and Harpacticoida. The vertical distribution of the meiofauna was in accordance with what has been reported from other intertidal beaches. Nematoda were studied in detail and their densities ranged over 0.7–7.7 individuals in 10 cm2 in the exposed beach and 2.7–186.0 individuals in 10 cm2 in the sheltered beach. Nematodes were identified to genus level and a total of eight nematode genera were found. Sediment community respiration, measured as oxygen consumption, ranged between 2.3 cm3 O2 m−2 h−1 in the exposed beach and 7.3 cm3 O2 m−2 h−1 in the sheltered beach (respectively, the equivalent of 24 mg and 75 mg of organic carbon metabolised per day). Values from the sheltered site are within the range of results registered in much warmer localities.

Development of a modified medium pressure microwave vapor-phase digestion method for difficult to digest organic samples.

A previously developed microwave heated vapor-phase digestion method for biological samples was modified to enable digestion of difficult to digest organic samples. Organic samples containing ca. 100 mg of organic carbon were digested using volume calibrated quartz inserts inside second generation type medium pressure microwave vessels. As digestion reagents, 98% sulfuric acid, 70% nitric acid and 30% hydrogen peroxide were used. The accuracy of the method was tested with six certified reference materials. Elements Ca, Fe, K, Na, Mg, P and Zn were determined from NIST-SRM 8433 corn bran. Elements Al, Fe, Cd, Cu, and Zn were determined from NRCC DOLT-2 dogfish liver. The element Cd was determined from IRMM-VDA Cd in polyethylene No. 001-004 reference materials. These elements were determined from digested samples by ICP-OES. The results were close or within certified limits. The modified method could digest nearly all the materials tested, including the above mentioned reference materials, 2-nitrobenzoic acid (2-NBA), 4-NBA and copper(II) phthalosyanine-3, 4',4',4'-tetrasulfonic acid tetrasodium salt (CPS). The method could not digest 3-NBA.

Sources of terrestrially-derived organic carbon in lower Mississippi River and Louisiana shelf sediments: implications for differential sedimentation and transport at the coastal margin

In this study, we examined the temporal and spatial variability of terrestrial organic carbon sources in lower Mississippi River and Louisiana shelf sediments (during 11 cruises over a 22-month period) to further understand the sorting dynamics and selective transport of vascular plant materials within the primary dispersal system of the river. Bulk δ 13 C values in lower river sediments ranged from −21.90‰ to −24.64‰ (mean=−23.20±1.09‰), these values were generally more depleted than those found in shelf sediments (−22.5‰ to −21.2‰). The Λ 8 (Λ 8 =sum of vanillyl, syringyl and cinnamyl phenols produced from the oxidation of 100 mg of organic carbon) values in the lower river ranged from 0.71 to 3.74 (mean=1.78±0.23). While there was no significant relationship between Λ 8 and river discharge ( p >0.05), the highest value occurred during peak discharge in April 1999—which corresponded to the highest observed C/N value of 17.41. The Λ 8 values on the shelf ranged from 0.68 to 1.36 (mean=0.54±0.30) and were significantly lower ( p <0.05) than the average value for lower river sediments. The range of S/V (syringyl/vanillyl) and C/V (cinnamyl/vanillyl) ratios on the shelf, 0.11 to 0.95 and 0.01 to 0.08, respectively, were similar to that found in the lower river. These low C/V ratios are indicative a mixture of woody and non-woody carbon sources. Recent work by Goni et al. [Nature 389 (1997) 275; Geochim. Cosmochim. Acta 62 (1998) 3055], which did not include sampling transects within the primary dispersal system of the Mississippi River, showed a non-woody vascular plant signature on the Louisiana shelf. This suggests that riverine-derived woody tissues preferentially settle out of the water column, in the lower river and inner shelf, prior to the selective dispersal of C 3 versus C 4 non-woody materials in other regions the shelf and slope. This works further demonstrates the importance of differential settlement of particles, sampling location within the dispersal system, and river discharge, when examining biogeochemical cycles in river-dominated margins.

An altered Pseudomonas diversity is recovered from soil by using nutrient-poor Pseudomonas-selective soil extract media.

We designed five Pseudomonas-selective soil extract NAA media containing the selective properties of trimethoprim and sodium lauroyl sarcosine and 0 to 100% of the amount of Casamino Acids used in the classical Pseudomonas-selective Gould's S1 medium. All of the isolates were confirmed to be Pseudomonas by a Pseudomonas-specific OprF antibody and a Pseudomonas-specific PCR targeting 16S ribosomal DNA. The Pseudomonas isolates were characterized by classical physiological tests, repetitive extragenic palindromic-PCR, Fourier transform infrared spectroscopy, and carbon source utilization patterns. Several of these analyses showed that the amount of Casamino Acids significantly influenced the diversity of the recovered Pseudomonas isolates. Furthermore, the data suggested that specific Pseudomonas subpopulations were represented on the nutrient-poor media. The NAA 1:100 medium, containing ca. 15 mg of organic carbon per liter, consistently gave significantly higher Pseudomonas CFU counts than Gould's S1 when tested on four Danish soils. NAA 1:100 may, therefore, be a better medium than Gould's S1 for enumeration and isolation of Pseudomonas from the low-nutrient soil environment.

Biodegradability enhancement of refractory pollutants by ozonation: a laboratory investigation on an azo-dyes intermediate

The effectiveness of ozone treatment for improving the biodegradability of recalcitrant pollutants has been proved by investigating the ozonation reaction of FAST-VIOLET-B (FVB) a bioresistant chemical intermediate of azo-dyes. Laboratory scale experiments have been carried out, at room temperature, by bubbling, for 90 min, ozonated air (9ppmO3/min) into 0.35 1 of an alkaline (pH=11) aqueous solution (50 ppm) of FVB. The experimental results indicate that during the ozonation, even though complete FVB degradation occurs in 10 min, ozone consumption goes on for a further 20 min after which time most degradation reactions are completed. The main ozonation by-products, identified by HPLC, IC, and GC-MS are formaldehyde, acetaldehyde, glyoxal, acetone, acetic-, formic-, oxalic- and carbonic-acid, plus six FVB derivatives scarcely biodegradable. At the end of the ozonation, i.e. after 30 min., the initial values of TOC (35 mgC/l) and COD (103 mgO2/l) are respectively 27 and 25 and correspond to a relative removal of about 23% and 76%. As for FVB solution biodegradability expressed as (BOD5)/(COD) ratio, during the first 10 min its value regularly increases from zero up to a maximum of 0.75 that corresponds to an ozone consumption of 2.4 mg per each mg of organic carbon initially present in the solution.

A reevaluation of the chromic acid colorimetric procedure for soil organic carbon

Two methods are currently used to measure soil organic carbon (SOC); one based on measuring CO2 evolution after high temperature combustion of the sample and the other on measuring dichromate reduction after organic carbon (OC) oxidation. The former method is the more accurate, but requires correction for soils with free calcium carbonate; the latter uses a hazardous heavy metal, dichromate (Cr 6+), but is easier when done colorimetrically (Cr 3+ measured at 625 ran) and is less expensive. If we could minimize the hazard and health concerns associated with the hexavalent chromium (Cr 6+), which is required in excess for complete SOC oxidation, and assure adequate accuracy, this method may be more acceptable especially where samples are few, and free calcium carbonate may be present. A methodology is presented where the amount of soil sample (0.1 to 0.5 g) and dichromate used in the analysis (2.5 mL of 0.167M dichromate) is small. The unreacted dichromate after analysis, is further reduced with glucose or other carbon (C) source to produce the less toxic Cr 3+, which in small quantities, can be discarded to landfills once properly precipitated and neutralized. Accuracy of the colorimetric procedure when compared to the CN Analyzer was adequate for samples with less than 1.3% SOC [2% soil organic matter (SOM)], amounts typical for cultivated soils of the Central Great Plains. For samples above 1.3% SOC (>2% SOM), accuracy was improved by reducing sample size so 2.0 to 5.5 mg of OC was contained in the sample.

Gut repletion during diel vertical migration in the benthopelagic crustacean Eurydice truncata Norman, 1868 (Isopoda, Cirolanidae)

The sand-burrowing isopod Eurydice truncata migrates from the benthos up to the neuston layer during the night. The gut contents of vertical migrant animals sampled in nocturnal neuston hauls off the Mediterranean coast of France were examined. The hauls were performed, on the one hand, from dusk to dawn, at a single station on the shelf and another on the slope, and, on the other hand, in the middle of the night, at various stations from the inner shelf to the slope. In shelf waters, the percentage rate of filled guts increased quickly after dusk and had reached almost 100% after 3 h of darkness. Isopods feed on living neustonic animals, preferably immobilized or passive living matter such as insects trapped at the surface or fish spawn. During the night, the gut contents gradually became more compact, and the remains of prey became less identifiable. The dry weight of the compacted gut contents of a single adult averages 0.50 mg, including 0.26 mg of organic carbon. At dawn, the downward migration leads to this neustonic matter being vertically transferred from the surface layer to within the sediment. A decrease in the animal's level of gut fullness occurs from inshore to offshore waters; this decrease in the feeding activity might generate a high rate of mortality in animals advected to slope water.

Biodegradability enhancement of refractory pollutants by ozonation: A laboratory investigation on an azo-dyes intermediate

The effectiveness of ozone treatment for improving (he biodegradability of recalcitrant pollutants has been proved by investigating the ozonation reaction of FAST-VIOLET-B (FVB) a bioresistant chemical intermediate of azo-dyes. Laboratory scale experiments have been carried out, at room temperature, by bubbling, for 90 min, ozonated air (9ppmO3/min) into 0.35 l of an alkaline (pH=11) aqueous solution (50 ppm) of FVB. The experimental results indicate that during the ozonation, even though complete FVB degradation occurs in 10 min, ozone consumption goes on for a further 20 min after which time most degradation reactions are completed. The main ozonation by-products, identified by HPLC, IC, and GC-MS are formaldehyde, acetaldehyde, glyoxal, acetone, acetic-, formic-, oxalic- and carbonic-acid, plus six FVB derivatives scarcely biodegradable. At the end of the ozonation, i.e. after 30 min., the initial values of TOC (35 mgC/l) and COD (103 mgO2/l) are respectively 27 and 25 and correspond to a relative removal of about 23% and 76%. As for FVB solution biodegradability expressed as (BOD5)/COD) ratio, during the first 10 min its value regularly increases from zero up to a maximum of 0.75 that corresponds to an ozone consumption of 2.4 mg per each mg of organic carbon initially present in the solution.

Analysing energy content: a new micro-assay and an assessment of the applicability of acid dichromate assays

This study describes a micro-assay, based on acid dichromate oxidation, with a resolution of at least 0.5 μg organic carbon and an upper limit of ≤20 μg C. We also document several important properties of acid dichromate assays and establish their effectiveness for quantifying organic carbon and energy content of marine and freshwater organisms. Both the micro-assay and the previously described standard assay are highly sensitive to chloride: absorbance readings were significantly depressed by the presence of only 0.5–1.0 μl of seawater, and the effect of seawater was shown to be due to its chloride content. The amount of chloride contained within the bodies of very small marine organisms may therefore be sufficient to interfere with the assay. Contrary to previous claims, we found that incubating samples with phosphoric acid did not prevent chloride from interfering with the assays. The micro- and standard assays were not sensitive to inorganic carbon and were therefore specific to organic carbon. The assays were effective in estimating total energy content of carbohydrate and lipid material, but underestimated the energy content of protein material by 47–69%. This limitation can be overcome by using a protein micro-assay to correct for underestimation by the acid dichromate assays. Based on our findings, the reliability of acid dichromate oxidation assays for analysing samples of marine organisms is questionable. The assays are effective, however, for analysing chloride-free tissues or extracts. In addition, the assays have considerable potential for determining energy content of small freshwater organisms. In particular, the micro-assay is at least an order of magnitude more sensitive than the standard assay, and constitutes a relatively simple way of measuring energy content of very small samples, such as individual embryos or early juveniles of aquatic animals and plants.

Soil humic substances stimulate proton release by intact oat seedling roots

The effect of a soil humic fraction (HS) on proton extrusion into deionized water by intact oat seedling roots was studied. In the presence of HS, at concentration of 10 μg organic carbon (C) mL‐1, a clear stimulation of acidification of the outer medium by the roots was observed after three to four hours of incubation. The addition of 0.5 mM vanadate to the solution bathing the roots drastically reduced the net proton extrusion, either in the presence or absence of HS, suggesting the involvement of the plasma membrane H+‐ATPase in the stimulation of the acidification of the outer medium by oat roots. The release of potassium (K) from the roots into deionized water was also monitored concomitantly to the proton extrusion. The loss of endogenous K from the roots was similar in the presence or absence of HS, while the recovery of the cation was slower in the presence of the humic fraction. However, after reabsorption of the released K, no net acidification was observed in control roots, while HS‐treated roots significantly decreased the pH of the deionized water. The addition of 3 mM K to the external medium greatly enhanced the proton release from roots, while the presence of humic substances reduced the magnitude of the stimulation by K. When K was supplied at a concentration closer to that encountered in the soil (<0.1 mM), HS significantly stimulated proton release. The effect of HS on root extracellular acidification supports the idea of a role of soil humic substances on plant nutrition via interaction with cell membrane functions.

Paleoproductivity from benthic foraminifera abundance: Glacial to postglacial change in the west-equatorial Pacific

Research Article| December 01, 1991 Paleoproductivity from benthic foraminifera abundance: Glacial to postglacial change in the west-equatorial Pacific Juan C. Herguera; Juan C. Herguera 1Scripps Institution of Oceanography 0215, University of California, San Diego, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar W. H. Berger W. H. Berger 1Scripps Institution of Oceanography 0215, University of California, San Diego, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar Geology (1991) 19 (12): 1173–1176. https://doi.org/10.1130/0091-7613(1991)019<1173:PFBFAG>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Juan C. Herguera, W. H. Berger; Paleoproductivity from benthic foraminifera abundance: Glacial to postglacial change in the west-equatorial Pacific. Geology 1991;; 19 (12): 1173–1176. doi: https://doi.org/10.1130/0091-7613(1991)019<1173:PFBFAG>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Surface productivity is correlated with the rate of accumulation of benthic foraminifera on the deep-sea floor. As a rule of thumb, for each 1 mg of organic carbon arriving at the sea floor, one benthic foram shell >150 μm is deposited. The correlation can be used to reconstruct organic flux to the sea floor in the past, and hence the productivity of past oceans. Applying the appropriate equations to box core data from the Ontong Java Plateau in the western equatorial Pacific, we found that productivity during the last glacial maximum exceeded present productivity by a factor of between 1.5 and 2.0, with intermediate values for the mid-transition period. Accumulation of benthic foraminifera was depressed on top of the plateau during the glacial and transitional period, presumably because increased winnowing removed part of the food supply. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Growth characteristics of the soil oligotrophic bacterium: Agromonas oligotrophica JCM 1494 on diluted nutrient broth.

The quantitative growth characteristics of the soil oligotrophic bacterium Agromonas oligotrophica JCM 1494 on diluted nutrient broth were investigated. The growth of the bacterium was totally inhibited in full strength nutrient broth (NB) but was supported in serially diluted NB of NB/10, NB/100, NB/1, 000, and NB/10, 000 with varied specific growth rates (k, 1/hr) of 0.102, 0.156, 0.117, and 0.089, respectively. The Ksvalue for NB was estimated to be NB/17, 500 or 0.46mg as organic carbon/ml. A yield value of 1.48×109 colony-forming unit mg of organic carbon was also calculated from the maximum growth yield analysis. From these results the oligotrophic nature of the bacterium was compared to those of other known oligotrophic bacteria.

The Effect Of Preozonation On The Control Of Trihal Omethane Formation

Abstract A study was made to obtain a better understanding of the manner in which preozonation affects trihalomethane (THM) formation with respect to humic acid, citric acid, and 11 aromatic compounds which were components of humic acid, all in dilute aqueous medium. Ozonation before chlorination is able tonotonly decrease, butalso increase the concentrations of THM precursors. The compounds which are inherently high THM precursors, such as resorcinol, aniline, salicyl-aldehyde, phenol, andp-hydroxybenzoic acid, are controlled with respect tothe increase inthe amount ofozone consumed, but the compounds which have essentially no or alow potential for chloroform formation, such as hydroquinone. salicylic acid, methoxybenzene. benzaldehyde. and benzole acid, produce their maximum THM levels at a certain value of ozone consumed. When 1mg of organic carbon consumes more than 8 mg of ozone, THM formation from thetested aromatic compounds isdepressed by ozone. Aliphatic carbonyl compounds which are the products ...

The feeding response of the epibenthic amphipod Siphonoecetes dellavallei Stebbing to varying food particle sizes and concentrations

The feeding reponse of the surface deposit-feeding amphipod Siphonoecetes dellavallei Stebbing was studied by measuring the uptake of four different 14C-labelled foods (a pure culture of bacteria and three diatom species) lying on top of the sediment, as a function of incubation time. Both the particle size of the food and, to a lesser degree, food density affected feeding. When the foods were offered at the same concentration in terms of organic carbon (23 μg·cm −2), ingestion rate was positively related to particle size, and varied from 4.5 to 85 × 10 −4 μg organic carbon·μg individual dry wt −1·h −1.The relation between feeding rate and density of a given food was similar to that reported for planktonic suspension-feeders, i.e. a saturated feeding curve. In these conditions, the upper limit of ingestion rate appeared to be fixed by the maximal capacity of the gut. Feeding rhythm switched from continuous to intermittent feeding at relatively low densities of large food particles, and appeared to be determined by the time required to fill the gut. This study shows that although S. dellavallei is capable of ingesting a wide range of food particle sizes, only large enough particles are used efficiently and enable the animals to maximize the ingested energy while minimizing the time spent feeding.

Growth patterns and substrate requirements of naturally occurring obligate oligotrophs

Eighteen strains of obligately oligotrophic bacteria that grow in a medium containing 1 mg of organic carbon per liter and do not grow in a rich medium (5 g/liter of nutrient) were isolated as dominant organisms from the oligotrophic water of Lake Biwa. The growth properties of these, especially of five strains, were examined. The maximum cell yield ranged from 8.5×10(4)/ml to 2.3×10(6)/ml, and their doubling times ranged from 6.6/h to 11.8/h in LT10(-4) medium (0.5 mg trypticase and 0.05 mg yeast extract in 1 liter of filtered and aged lake water). They also showed good growth in lake water medium without adding nutrients. The optimum concentrations for their growth were 5 mg/1, 5-50 mg/1, 50 mg/1, or 500 mg/1, depending on the strains. They utilized glutamate, glycine, serine, and glycolate, but not acetate, proline, or leucine. Several properties were examined. Their growth properties were very different from those of oligotrophs or oligocarbophiles isolated by other researchers.

Volatile organic compounds in coastal seawater

The occurence and temporal variations of a variety of low to medium polarity organic compounds in the volatility range bracketed by n-heptane and n-octadecane have been studied in seawater from a station in Vineyard Sound, Massachusetts, and from a tidal creek in Sippewisset Marsh, Massachusetts. The closed-loop vapor phase stripping method of Grob and Zürcher ( J. Chromatogr., v. 117, p. 285–294), high resolution glass capillary gas chromatography, and gas chromatography-mass spectrometry were used. Approximately 50 compounds were found at ≥ 2 ng/kg; most were recovered at less than 10 ng/kg, while the 20 ng/kg level was only rarely exceeded by a few components. The total material recovered was 0.2–1.0 μg organic carbon equivalent/kg seawater. The major compound classes found were normal alkanes, alkenes, aromatic and alkylaromatic hydrocarbons, n-aldehydes, dimethyldisulfide and dimethyltrisulfide, and a few halogenated hydrocarbons. The preliminary results suggest that both biogenic and anthropogenic sources were representted. Also, air-sea gas exchange and other physical processes may be important non-biological sinks.

THE EFFECTS OF THE DEPOSIT FEEDING POLYCHAETE PECTINARIA GOULDII ON THE INTERTIDAL SEDIMENTS OF BARNSTABLE HARBOR1

Under laboratory conditions, individual Pectinaria gouldii worked 6 g of sediment/day. This rate was related directly to sediment temperature and inversely to sediment pigment concentration. At this rate, corrected for the effects of daily tidal exposure and annual temperature fluctuations, the worm population in the flat studied (10 worms/m2) would completely work all sediment in the 6‐cm thick surface layer every 15 years. The observed activity of other deposit feeders would substantially reduce this time. P. gouldii removed 3.55 units of sediment pigment (42%) and 1.43 mg of organic carbon (45%) from each gram of sediment worked, suggesting a rapid utilization of the available organic matter.

Die analytische anwendung der kohlendioxyddestillation: Destillations- und titrationsmethode zur bestimmung des sich bei der totalen oxydation von organischen stoffen bildenden kohlendioxyds

Organic materials in aqueous solution are determined by the carbon dioxide formed by complete oxidation. This is distilled in a special apparatus into barium hydroxide solution covered with pentane and the excess of alkali titrated, 0.06–6 mg of organic carbon can be determined.