Charring and non-additive chemical reactions during ramped pyrolysis: Applications to the characterization of sedimentary and soil organic material

Williams, Elizabeth K.; Rosenheim, B. E.; McNichol, Ann P.; Masiello, Caroline A.

doi:10.1016/j.orggeochem.2014.10.006

Cited by 31 publications

(37 citation statements)

References 35 publications

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“…CO 2 thermographs also showed some variability between analyses of the same sample (Figure ). In samples at 85, 95, and 192 cm core depths, the combination of multiple runs provides us with the opportunity to visualize the replicability of thermograph shapes when the same sample is analyzed by Ramped PyrOx multiple times in the same manner [ Williams et al ., ]. Each run was normalized and integrated onto the same temperature scale for statistical comparison.…”

Section: Resultsmentioning

confidence: 99%

Sub‐ice shelf sediment geochronology utilizing novel radiocarbon methodology for highly detrital sediments

Subt

Yoon

Yoo

et al. 2017

Geochem Geophys Geosyst

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Sub‐ice shelf sediments near Larsen C ice shelf (LIS‐C) show fine‐scale rhythmic laminations that could provide a near‐continuous seasonal‐resolution record of regional ice mass changes. Despite the great potential of these sediments, a dependable Late Quaternary chronology is difficult to generate, rendering the record incomplete. As with many marginal Antarctic sediments, in the absence of preserved carbonate microfossils, the reliability of radiocarbon chronologies depends on presence of high proportions of autochthonous organic carbon with minimized detrital organic carbon. Consequently, acid insoluble organic (AIO) 14C dating works best where high productivity drives high sediment accumulation rates, but can be problematic in condensed sequences with high proportions of detrital organic carbon. Ramped PyrOx 14C dating has progressively been shown to improve upon AIO 14C dates, to the point of matching foraminiferal carbonate 14C dates, through differential thermochemical degradation of organic components within samples. But in highly detrital sediments, proportions of contemporaneously deposited material are too low to fully separate autochthonous organic carbon from detrital carbon in samples large enough to 14C date. We introduce two modifications of the Ramped PyrOx 14C approach applied to highly detrital sediments near LIS‐C to maximize accuracy by utilizing ultra‐small fractions of the highly detrital AIO material. With minimization of the uncertainty cost, these techniques allow us to generate chronologies for cores that would otherwise go undated, pushing the limits of radiocarbon dating to regions and facies with high proportions of pre‐aged detritus. Wider use of these techniques will enable more coordinated a priori coring efforts to constrain regional glacial responses to rapid warming where sediments had previously been thought too difficult to date.

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Section: Resultsmentioning

confidence: 99%

Sub‐ice shelf sediment geochronology utilizing novel radiocarbon methodology for highly detrital sediments

Subt

Yoon

Yoo

et al. 2017

Geochem Geophys Geosyst

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“…Considering that fresh surface soils had a stable pool peaking at ~500°C (Figures a–c), the relatively younger radiocarbon ages of the last split in river sediments may reflect small inputs of OC from surface soils which has been noted in compounds indicative of such sources (Williams et al, ). Charring of a small fraction of less thermally stable compounds which decomposes at higher temperature (Williams et al, ) cannot be ruled out; however, the fresh surface material high‐temperature peaks are a more likely source of younger material to high‐temperature fractions. The suggestion that deep soils are the dominant inputs is also supported by the old bulk radiocarbon age (10,000 yr B.P.)…”

Section: Resultsmentioning

confidence: 99%

“…As mentioned earlier, deposition of soil material in the upstream river channels was mostly from deep soil horizons, suggesting that much of surface soil OC was transported downstream, eventually reaching the coast. Particularly, the abundance of lignin in surface soils (Feng et al, ) may explain the association of younger ages with high temperature in the RPO at Station L1, because lignin needs a higher temperature to decompose (Williams et al, ; Yang et al, ). Also, lignin decay proxies were relatively low ([Ad/Al] v = 0.47 and [Ad/Al] s = 0.52) (Table S3), indicating inputs of fresh material from surface soils at L1.…”

Section: Resultsmentioning

confidence: 99%

Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From ¹⁴C Ramped Pyrolysis and Lignin Biomarkers

Zhang

Bianchi

Cui

et al. 2017

Geophysical Research Letters

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The deposition of terrestrial‐derived permafrost particulate organic carbon (POC) has been recorded in major Arctic river deltas. However, associated transport pathways of permafrost POC from the watershed to the coast have not been well constrained. Here we utilized a combination of ramped pyrolysis‐oxidation radiocarbon analysis (RPO 14C) along with lignin biomarkers, to track the linkages between soils and river and delta sediments. Surface and deep soils showed distinct RPO thermographs which may be related to degradation and organo‐mineral interaction. Soil material in the bed load of the river channel was mostly derived from deep old permafrost. Both surface and deep soils were transported and deposited to the coast. Hydrodynamic sorting and barrier island protection played important roles in terrestrial‐derived permafrost POC deposition near the coast. On a large scale, ice processes (e.g., ice gauging and strudel scour) and ocean currents controlled the transport and distribution of permafrost POC on the Beaufort Shelf.

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“…Williams et al . [] found that char formation stabilizes some carbon to decompose at higher pyrolysis temperatures. However, the chars formed during Ramped PyrOx retain inherent stability from the bulk organic material and that the T max proxy for organic matter stability is unaffected by char‐forming reactions during pyrolysis as evidenced by the relationships between the Ramped PyrOx T max stability proxy and the compositional indicators of SOM decomposition described in Baldock et al .…”

Section: Discussionmentioning

confidence: 99%

What happens to soil organic carbon as coastal marsh ecosystems change in response to increasing salinity? An exploration using ramped pyrolysis

Williams

Rosenheim

2015

Geochem Geophys Geosyst

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Coastal wetlands store vast amounts of organic carbon, globally, and are becoming increasingly vulnerable to the effects of anthropogenic sea level rise. To understand the effect of sea level rise on organic carbon fate and preservation in this global sink, it is necessary to characterize differences in the biogeochemical stability of coastal wetland soil organic carbon (SOC). Here we use ramped pyrolysis/oxidation decomposition characteristics as proxies for SOC stability to understand the fate of carbon storage in coastal wetlands comprising the Mississippi River deltaic plain, undergoing rapid rates of local sea level rise. Soils from three wetland types (fresh, brackish, and salt marshes) along a salinity gradient were subjected to ramped pyrolysis analysis to evaluate decomposition characteristics related to thermochemical stability of SOC. At equivalent soil depths, we observed that fresh marsh SOC was more stable than brackish and salt marsh SOC. Depth, isotopic, elemental, and chemical compositions, bulk density, and water content of SOC all exhibited different relationships with SOC stability across the marsh salinity gradient, indicative of different controls on SOC stability within each marsh type. The differences in stability imply stronger preservation potential of fresh marsh soil carbon, compared to that of salt and brackish marshes. Considering projected marsh ecosystem responses to sea level rise, these observed stability differences are important in planning and implementing coastal wetland carbon-focused remediation and improving climate model feedbacks with the carbon cycle. Specifically, our results imply that ecosystem changes associated with sea level rise will initiate the accumulation of less stable carbon in coastal wetlands.

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Charring and non-additive chemical reactions during ramped pyrolysis: Applications to the characterization of sedimentary and soil organic material

Cited by 31 publications

References 35 publications

Sub‐ice shelf sediment geochronology utilizing novel radiocarbon methodology for highly detrital sediments

Sub‐ice shelf sediment geochronology utilizing novel radiocarbon methodology for highly detrital sediments

Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From ¹⁴C Ramped Pyrolysis and Lignin Biomarkers

What happens to soil organic carbon as coastal marsh ecosystems change in response to increasing salinity? An exploration using ramped pyrolysis

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Charring and non-additive chemical reactions during ramped pyrolysis: Applications to the characterization of sedimentary and soil organic material

Cited by 31 publications

References 35 publications

Sub‐ice shelf sediment geochronology utilizing novel radiocarbon methodology for highly detrital sediments

Sub‐ice shelf sediment geochronology utilizing novel radiocarbon methodology for highly detrital sediments

Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From 14C Ramped Pyrolysis and Lignin Biomarkers

What happens to soil organic carbon as coastal marsh ecosystems change in response to increasing salinity? An exploration using ramped pyrolysis

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Permafrost Organic Carbon Mobilization From the Watershed to the Colville River Delta: Evidence From ¹⁴C Ramped Pyrolysis and Lignin Biomarkers