Carbonate removal from coastal sediments for the determination of organic carbon and its isotopic signatures, δ<sup>13</sup>C and Δ<sup>14</sup>C: comparison of fumigation and direct acidification by hydrochloric acid

Komada, Tomoko; Anderson, Mark R.; Dorfmeier, Corin L.

doi:10.4319/lom.2008.6.254

Cited by 172 publications

(115 citation statements)

References 46 publications

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“…Soils were then air-dried, passed through a 2-mm sieve, and stored at room temperature. Soil carbonates were removed from an aliquot of each sample by the acid fumigation technique (Harris et al 2001;Komada et al 2008). Briefly, 25 µL of deionized water were added to 15 mg of soil in a ceramic crucible, and exposed to the vapors of concentrated HCl in a sealed glass desiccator for 48 hr.…”

Section: Methodsmentioning

confidence: 99%

Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation

Plante

Beaupré²,

Roberts³

et al. 2013

Radiocarbon

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ABSTRACT. Radiocarbon analysis is an important tool in quantifying soil organic matter (SOM) dynamics within the terrestrial carbon cycle. However, there is increasing appreciation that representing SOM as a single, homogeneous pool with a single, mean 14 C concentration is inadequate. We investigate whether the differing patterns in CO 2 release during rampedtemperature oxidation reflect organic matter of different ages, and hypothesize that thermally labile SOM (combusting at low temperatures) consists of younger carbon than thermally resistant organic matter. Topsoil samples under contrasting land uses (native vegetation and long-term cultivation) were selected for 14 C analysis before and after acid fumigation for the removal of carbonates. Results of bulk 14 C analyses showed a significant shift in 14 C age from 0.944 Fm under native vegetation to 0.790 Fm under cultivation. Four to 5 "fractions" associated with different CO 2 -evolution regions were identified by thermal analysis and analyzed for 14 C via modifications to NOSAMS' established "programmed temperature pyrolysis system," in which discrete CO 2 fractions evolved during ramped-temperature oxidation were isotopically characterized by a microwave gas ion source (GIS) continuous-flow AMS (CFAMS) system. Results showed that while acid fumigation removed soil carbonates, the treatment also significantly altered the thermograms and inferred SOM composition. While direct attribution of 14 C values to individual peaks is somewhat confounded by overlapping temperature ranges for oxidation of unique populations of carbon, in general, thermally stable fractions of SOM appear to be 14 C-depleted compared to thermally reactive (low temperature) fractions regardless of pretreatment.

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Section: Methodsmentioning

confidence: 99%

Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation

Plante

Beaupré²,

Roberts³

et al. 2013

Radiocarbon

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show abstract

“…Hence, the PIC data presented here only reflect carbonates that were finely disseminated throughout the sediment matrix. POC content was determined using a Costech ECS-4010 after fumigation with HCl (Komada et al 2008); total nitrogen (TN) content was determined on untreated samples. For determination of 14 C and 13 C values of POC, the samples were oxidized by sealed quartz-tube combustion at 850uC for 4 h in the presence of CuO and Ag (Druffel et al 1992) after fumigation as described above.…”

Section: Methodsmentioning

confidence: 99%

Transformations of carbon in anoxic marine sediments: Implications from Δ¹⁴C and δ¹³C signatures

Komada

Polly

Johnson

2012

Limnology & Oceanography

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Organic-rich nearshore sediment was incubated in sealed vessels under sulfate-reducing conditions to investigate the mechanism of dissolved organic carbon (DOC) production in marine sediments. Concentrations and isotopic signatures (d 13 C and D 14 C) of particulate organic carbon (POC), DOC, dissolved inorganic carbon (DIC), and particulate inorganic carbon (PIC) were monitored for 130 d. POC solubilization was largely counterbalanced by respiration, resulting in a net increase in DIC of . 35 mmol L 21 . Net accumulation of DOC was relatively muted, yet significant, at , 0.04 mmol L 21 . All carbon pools exhibited distinct d 13 C and D 14 C signatures prior to the incubation. Once the incubation began, these isotopic values varied with time, reflecting exchanges of isotopically distinct moieties across carbon pools. The 14 C-enriched (modern) component of bulk POC was selectively solubilized into DOC, and the majority of this DOC was rapidly respired to DIC. However, net accumulation of DOC was accompanied by a drop in D 14 C, suggesting that during selective solubilization of the younger component of bulk POC, there was concomitant solubilization of pre-aged organic matter that subsequently accumulated as DOC. PIC was minor in terms of pool size, but likely played a critical role in determining the d 13 C signature of pore-water DIC through isotope exchange.

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“…Encrusted kelp and feces from this diet were acidified prior to analysis to remove CaCO 3 from Membranipora membranacea. Small aliquots of 1 N HCl were added to each sample drop by drop, drying in between at 40°C, until no more CO 2 was released (Kennedy et al 2005, Komada et al 2008. The procedure was repeated twice more to ensure that all CaCO 3 was removed.…”

Section: Field Feeding Experimentmentioning

confidence: 99%

Fecal production by sea urchins in native and invaded algal beds

Sauchyn¹,

Scheibling²

2009

Mar. Ecol. Prog. Ser.

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-1). Low C:N ratios of feces obtained from grazing C. fragile (8.5) or encrusted kelp (11.4), compared to clean kelp (30.7), suggest that feces from invaded assemblages are a higher quality food source for microbes and detritivores. To compare dispersal characteristics of feces from each diet, we measured pellet shape, size, density, and settling and critical erosion velocities. Using a wave model, we estimated the depth at which feces would be deposited under seasonally varying wave conditions. We found that pellets of C. fragile are likely deposited at the greatest depths (33 to 55 m), pellets of clean kelp at intermediate depths (28 to 47 m), and pellets of encrusted kelp at the shallowest depths (22 to 40 m). Our findings suggest a smaller amount of higher quality feces enters the detrital food web at greater depths from Codium meadows than from native kelp beds.

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Carbonate removal from coastal sediments for the determination of organic carbon and its isotopic signatures, δ¹³C and Δ¹⁴C: comparison of fumigation and direct acidification by hydrochloric acid

Cited by 172 publications

References 46 publications

Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation

Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation

Transformations of carbon in anoxic marine sediments: Implications from Δ¹⁴C and δ¹³C signatures

Fecal production by sea urchins in native and invaded algal beds

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Carbonate removal from coastal sediments for the determination of organic carbon and its isotopic signatures, δ13C and Δ14C: comparison of fumigation and direct acidification by hydrochloric acid

Cited by 172 publications

References 46 publications

Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation

Distribution of Radiocarbon Ages in Soil Organic Matter by Thermal Fractionation

Transformations of carbon in anoxic marine sediments: Implications from Δ14C and δ13C signatures

Fecal production by sea urchins in native and invaded algal beds

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Product

Resources

About

Carbonate removal from coastal sediments for the determination of organic carbon and its isotopic signatures, δ¹³C and Δ¹⁴C: comparison of fumigation and direct acidification by hydrochloric acid

Transformations of carbon in anoxic marine sediments: Implications from Δ¹⁴C and δ¹³C signatures