The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Alex L Sessions - One of the best experts on this subject based on the ideXlab platform.
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Plant Wax d h ratios in the southern european alps record multiple aspects of climate variability
Quaternary Science Reviews, 2016Co-Authors: Stefanie B. Wirth, Alex L SessionsAbstract:We present a Younger Dryas–Holocene record of the hydrogen isotopic composition of sedimentary Plant Waxes (δD_(Wax)) from the southern European Alps (Lake Ghirla, N-Italy) to investigate its sensitivity to climatic forcing variations in this mid-latitude region (45°N). A modern altitudinal transect of δD values of river water and leaf Waxes in the Lake Ghirla catchment is used to test present-day climate sensitivity of δD_(Wax). While we find that altitudinal effects on δD_(Wax) are minor at our study site, temperature, precipitation amount, and evapotranspiration all appear to influence δD_(Wax) to varying extents. In the lake-sediment record, δD_(Wax) values vary between −134 and −180‰ over the past 13 kyr. The long-term Holocene pattern of δD_(Wax) parallels the trend of decreasing temperature and is thus likely forced by the decline of northern hemisphere summer insolation. Shorter-term fluctuations, in contrast, may reflect both temperature and moisture-source changes. During the cool Younger Dryas and Little Ice Age (LIA) periods we observe unexpectedly high δD_(Wax) values relative to those before and after. We suggest that a change towards a more D-enriched moisture source is required during these intervals. In fact, a shift from northern N-Atlantic to southern N-Atlantic/western Mediterranean Sea sources would be consistent with a southward migration of the Westerlies with climate cooling. Prominent δD_(Wax) fluctuations in the early and middle Holocene are negative and potentially associated with temperature declines. In the late Holocene (<4 kyr BP), excursions are partly positive (as for the LIA) suggesting a stronger influence of moisture-source changes on δD_(Wax) variation. In addition to isotopic fractionations of the hydrological cycle, changes in vegetation composition, in the length of the growing season, and in snowfall amount provide additional potential sources of variability, although we cannot yet quantitatively assess these in the paleo-record. We conclude that while our δD_(Wax) record from the Alps does contain climatic information, it is a complicated record that would require additional constraints to be robustly interpreted. This also has important implications for other water-isotope-based proxy records of precipitation and hydro-climate from this region, such as cave speleothems.
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Plant-Wax D/H ratios in the southern European Alps record multiple aspects of climate variability
Quaternary Science Reviews, 2016Co-Authors: Stefanie B. Wirth, Alex L SessionsAbstract:We present a Younger Dryas–Holocene record of the hydrogen isotopic composition of sedimentary Plant Waxes (δD_(Wax)) from the southern European Alps (Lake Ghirla, N-Italy) to investigate its sensitivity to climatic forcing variations in this mid-latitude region (45°N). A modern altitudinal transect of δD values of river water and leaf Waxes in the Lake Ghirla catchment is used to test present-day climate sensitivity of δD_(Wax). While we find that altitudinal effects on δD_(Wax) are minor at our study site, temperature, precipitation amount, and evapotranspiration all appear to influence δD_(Wax) to varying extents. In the lake-sediment record, δD_(Wax) values vary between −134 and −180‰ over the past 13 kyr. The long-term Holocene pattern of δD_(Wax) parallels the trend of decreasing temperature and is thus likely forced by the decline of northern hemisphere summer insolation. Shorter-term fluctuations, in contrast, may reflect both temperature and moisture-source changes. During the cool Younger Dryas and Little Ice Age (LIA) periods we observe unexpectedly high δD_(Wax) values relative to those before and after. We suggest that a change towards a more D-enriched moisture source is required during these intervals. In fact, a shift from northern N-Atlantic to southern N-Atlantic/western Mediterranean Sea sources would be consistent with a southward migration of the Westerlies with climate cooling. Prominent δD_(Wax) fluctuations in the early and middle Holocene are negative and potentially associated with temperature declines. In the late Holocene (
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Orbital- and millennial-scale changes in the hydrologic cycle and vegetation in the western African Sahel: insights from individual Plant Wax δD and δ^(13)C
Quaternary Science Reviews, 2010Co-Authors: Eva M Niedermeyer, Enno Schefuß, Alex L Sessions, Stefan Mulitza, Gesine Mollenhauer, Michael Schulz, Gerold WeferAbstract:To reconstruct variability of the West African monsoon and associated vegetation changes on precessional and millennial time scales, we analyzed a marine sediment core from the continental slope off Senegal spanning the past 44,000 years (44 ka). We used the stable hydrogen isotopic composition (dD) of individual terrestrial Plant Wax n-alkanes as a proxy for past rainfall variability. The abundance and stable carbon isotopic composition (d 13 C) of the same compounds were analyzed to assess changes in vegetation composition (C3/C4 Plants) and density. The dD record reveals two wet periods that coincide with local maximum summer insolation from 38 to 28 ka and 15 to 4 ka and that are separated by a less wet period during minimum summer insolation. Our data indicate that rainfall intensity during the rainy season throughout both wet humid periods was similar, whereas the length of the rainy season was presumably shorter during the last glacial than during the Holocene. Additional dry intervals are identified that coincide with North Atlantic Heinrich stadials and the Younger Dryas interval, indicating that the West African monsoon over tropical northwest Africa is linked to both insolation forcing and highlatitude climate variability. The d 13 C record indicates that vegetation of the western Sahel was consistently dominated by C4 Plants during the past 44 ka, whereas C3-type vegetation increased during the Holocene. Moreover, we observe a gradual ending of the Holocene humid period together with unchanging ratio of C3 to C4 Plants, indicating that an abrupt aridification due to vegetation feedbacks is not a general characteristic of this time interval.
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Rapid analysis of 13C in Plant-Wax n-alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments
Geochemistry Geophysics Geosystems, 2004Co-Authors: Kelsey E Mcduffee, Timothy I. Eglinton, Alex L Sessions, Sean P Sylva, Thomas Wagner, J M HayesAbstract:Long-chain, odd-carbon-numbered C25 to C35 n-alkanes are characteristic components of epicuticular Waxes produced by terrestrial higher Plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total Plant-Wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straight-chain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO4. Short-chain n-alkanes of nonvascular Plant origin (
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rapid analysis of 13c in Plant Wax n alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments
Geochemistry Geophysics Geosystems, 2004Co-Authors: Timothy I. Eglinton, Kelsey E Mcduffee, Alex L Sessions, Sean P Sylva, Thomas Wagner, J M HayesAbstract:Long-chain, odd-carbon-numbered C25 to C35 n-alkanes are characteristic components of epicuticular Waxes produced by terrestrial higher Plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total Plant-Wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straight-chain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO4. Short-chain n-alkanes of nonvascular Plant origin (
Sarah J. Feakins - One of the best experts on this subject based on the ideXlab platform.
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Identifying Plant Wax inputs in lake sediments using machine learning
Organic Geochemistry, 2021Co-Authors: Mark D. Peaple, Jessica E. Tierney, David Mcgee, Tim K. Lowenstein, Tripti Bhattacharya, Sarah J. FeakinsAbstract:Abstract This study aims to evaluate whether machine learning techniques can be successfully applied to process the complex information contained within the molecular abundance distributions of Plant Wax n-alkane and n-alkanoic acid homologous series. We trained five vegetation identification models using Plant Wax chain length distributions from modern Plants in the Mojave Desert (hyperarid) and the San Bernardino Mountains (conifer forest) and previously published data for macrophytes from Blood Pond (USA) and Mt Kenya (Kenya). All vegetation identification models proved accurate (mean classification accuracy = 0.81) at classifying the modern Plant Wax chain length distributions into desert Plants, conifer and macrophyte categories. We then applied the models to fossil Waxes extracted from a 76 m lacustrine sediment core drilled in Searles Valley, CA with an approximate age range of 10 to 150 kyrs (SLAPP-SRLS17) to reconstruct the proportion of desert Plants, conifer woodland and lake vegetation. We compared our machine learning models with a previously published linear mixing model and validated our modelled Plant type distributions by comparing the results with the archaeol caldarchaeol ecometric (ACE), a proxy for lake salinity, measured in the same core. We found a moderate positive correlation (r = 0.40) between the modelled desert Plant proportion and high lake salinity in our models as well as a negative correlation (r = –0.45) between modelled macrophyte Plants and ACE, validating the ability of the machine learning techniques to detect both xeric and macrophyte Plant communities. Our results suggest that machine learning of Plant Wax molecular abundance distributions has potential to reconstruct past Plant communities, given information from two compound classes and highly differentiated vegetation types.
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Plant Wax evidence for precipitation and vegetation change from a coastal sinkhole lake in the Bahamas spanning the last 3000 years
Organic Geochemistry, 2020Co-Authors: A. Tamalavage, Peter J. Van Hengstum, Patrick Louchouarn, Patricia L. Fall, Jeffrey P. Donnelly, Nancy A. Albury, Sloan Coats, Sarah J. FeakinsAbstract:Abstract Plant Wax hydrogen isotopic composition is commonly used to reconstruct the hydrogen isotopic composition of precipitation used by terrestrial vegetation. However, mangroves growing in coastal environments take up a mixture of freshwater and seawater. Biosynthetic fractionation (between source water and Plant Wax) differs between Plant types and as a function of salinity, potentially complicating interpretations of past precipitation in coastal environments. In order to reconstruct Holocene hydrologic and ecologic changes archived within sediments from Blackwood Sinkhole on Abaco Island in The Bahamas, we adopt a multi-proxy approach using Plant Wax hydrogen isotopic composition (δ2H) to reconstruct paleohydrology, together with Plant Wax carbon isotopic composition (δ13CWax), sterol biomarkers and pollen abundances to identify vegetation change. When pollen indicates a stable terrestrial Plant community (2950–850 cal yrs BP), variations of δ2H values measured on the Plant Wax C28 n-alkanoic acid are interpreted in terms of precipitation isotope (δ2Hprecip) changes, with 2H-depletion from 2950 to ∼2100 cal yrs BP and ∼1700 to 1000 cal yrs BP. However, interpretation is complicated at 850 cal yrs BP, when δ2H values decrease (−50‰) concurrent with increased Laguncularia racemosa (white mangrove) and Conocarpus erectus (buttonwood mangrove), and the mangrove-derived biomarker, taraxerol. We develop a pollen-based correction for mangrove inputs, yielding reconstructed precipitation isotope estimates (δ2Hprecip-corr). Low δ2Hprecip-corr values are synchronous with increased abundance of pine pollen, both of which may indicate wetter conditions from 850 cal yrs BP to present. This study provides additional evidence that mangroves can complicate hydrologic reconstructions from n-alkyl terrestrial Plant Wax biomarkers, and that such complication can be removed by pollen-based correction. After correcting for mangrove inputs, we obtain estimates of δ2Hprecip-corr from −33 to +25‰ throughout the last 2950 years, with uncertainties on the order of 10–20‰.
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Tropical soil profiles reveal the fate of Plant Wax biomarkers during soil storage
Organic Geochemistry, 2019Co-Authors: A. Joshua West, Sarah J. FeakinsAbstract:Abstract The Waxy coating that protects the leaves and other soft tissues of Plants includes n-alkane and n-alkanoic acid compounds that are commonly used as biomarkers to reconstruct past environment. Plant Waxes have geological relevance given their persistence in soils and paleosols, as well as in lake and marine sediments, yet diagenesis may alter their molecular and isotopic signatures from synthesis to deposition. This study seeks to understand the fate of Plant Wax biomarkers in soils after leaf-fall as characterized by a series of tropical soil profiles. We investigate the changes in abundance, molecular distributions, and hydrogen (δD) and carbon isotopic compositions (δ13C) of Plant Waxes (n-alkanes and n-alkanoic acids) in six litter-to-soil profiles along a 2740 m elevation transect from the eastern flank of the Andes mountains down to the lowland Amazon floodplain in Peru. From litter to soil, we find acid/alkane ratios increase while absolute abundances decrease. In contrast, within each soil, acid/alkane ratios are roughly constant, and we find an equivalent exponential decline in concentration in both compound classes with depth, with molecular distributions indicating some new production. We observe a 4–6‰ 13C-enrichment from litter to deeper soils for both C29 n-alkanes and C30 n-alkanoic acids, of which the Suess effect accounts for ≤2‰. We infer that microbial degradation and production (or ‘turnover’) processes influence the δ13C of Plant Waxes that survive in soils; in contrast, no systematic change in δD values is observed. The Plant Wax signal in soils includes averaging of inputs and diagenetic effects, so this signature is particularly relevant for the interpretation of Plant Wax archives in paleosols and the Plant Waxes eroded from soils and exported to downstream sedimentary archives. We show that soils represent the major stock of Plant Wax under living ecosystems, suggesting that soils may be a quantitatively-important source of Plant Waxes available for fluvial erosion, with implications for studies of carbon cycling and paleoenvironmental reconstructions from downstream geological archives.
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Dual isotope evidence for sedimentary integration of Plant Wax biomarkers across an Andes-Amazon elevation transect
Geochimica et Cosmochimica Acta, 2018Co-Authors: Sarah J. Feakins, Valier Galy, Camilo Ponton, A. Joshua WestAbstract:Abstract Tropical montane regions tend to have high rates of precipitation, biological production, erosion, and sediment export, which together move material off the landscape and toward sedimentary deposits downstream. Plant Wax biomarkers can be used to investigate sourcing of organic matter and are often used as proxies to reconstruct past climate and environment in sedimentary deposits. To understand how Plant Waxes are sourced within a wet, tropical montane catchment, we measure the stable C and H isotope composition (δ13C and δD) of n-alkanes and n-alkanoic acids in soils along an elevation transect and from sediments within the Madre de Dios River network along the eastern flank of the Peruvian Andes, draining an area of 75,400 km2 and 6 km of elevation. Soils yield systematic trends in Plant Wax δ13C (+1.75 and +1.31‰ km−1, for the C29 n-alkanes and C30 n-alkanoic acids respectively in the mineral horizon) and δD values (−10 and −12‰ km−1, respectively) across a 3.5 km elevation transect, which approximates trends previously reported from canopy leaves, though we find offsets between δ13C values in Plants and soils. River suspended sediments generally follow soil isotopic gradients defined by catchment elevations (δ13C: +1.03 and +0.99‰ km−1 and δD: −10 to −7‰ km−1, for the C29 n-alkanes and C30 n-alkanoic acids respectively) in the wet season, with a lowering in the dry season that is less well-constrained. In a few river suspended sediments, petrogenic contributions and depth-sorting influence the n-alkane δ13C signal. Our dual isotope, dual compound class and seasonal sampling approach reveals no Andean-dominance in Plant Wax export, and instead that the sourcing of Plant Waxes in this very wet, forested catchment approximates that expected for spatial integration of the upstream catchment, thus with a lowland dominance on areal basis, guiding paleoenvironmental reconstructions in tropical montane regions. The dual isotope approach provides a cross-check on the altitudinal signals and can resolve ambiguity such as might be associated with vegetation change or aridity in paleoclimate records. Further, the altitude effect encoded within Plant Waxes presents a novel dual-isotope biomarker approach to paleoaltimetry.
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Climatic and geomorphic drivers of Plant organic matter transport in the Arun River, E Nepal
Earth and Planetary Science Letters, 2016Co-Authors: Bernd Hoffmann, Sarah J. Feakins, Bodo Bookhagen, Stephanie Olen, Danda Pani Adhikari, Janardan Mainali, Dirk SachseAbstract:Fixation of atmospheric CO2 in terrestrial vegetation, and subsequent export and deposition of terrestrial Plant organic matter in marine sediments is an important component of the global carbon cycle, yet it is difficult to quantify. This is partly due to the lack of understanding of relevant processes and mechanisms responsible for organic-matter transport throughout a landscape. Here we present a new approach to identify terrestrial Plant organic matter source areas, quantify contributions and ascertain the role of ecologic, climatic, and geomorphic controls on Plant Wax export in the Arun River catchment spanning the world's largest elevation gradient from 205 to 8848 m asl, in eastern Nepal. Our approach takes advantage of the distinct stable hydrogen isotopic composition (expressed as δDδD values) of Plant Wax n-alkanes produced along this gradient, transported in river waters and deposited in flood deposits alongside the Arun River and its tributaries. In mainstem-flood deposits, we found that Plant Wax n -alkanes were mostly derived from the lower elevations constituting only a small fraction (15%) of the catchment. Informed by remote sensing data, we tested four differently weighted isotopic mixing models that quantify sourcing of tributary Plant-derived organic matter along the Arun and compare it to our field observations. The weighting parameters included catchment area, net primary productivity (NPP) and annual rainfall amount as well as catchment relief as erosion proxy. When weighted by catchment area the isotopic mixing model could not explain field observations on Plant Wax δDδD values along the Arun, which is not surprising because the large arid Tibetan Plateau is not expected to be a major source. Weighting areal contributions by annual rainfall and NPP captured field observations within model prediction errors suggesting that Plant productivity may influence source strength. However weighting by a combination of rainfall and catchment relief also captured the observed δDδD value pattern suggesting dominantly erosive control. We conclude that tributaries at the southern Himalayan front with high rainfall, high productivity, high relief and high erosion rates dominate Plant Wax exports from the catchment.
Timothy I. Eglinton - One of the best experts on this subject based on the ideXlab platform.
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Drought, agricultural adaptation, and sociopolitical collapse in the Maya Lowlands
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Peter M J Douglas, Timothy I. Eglinton, Mark Pagani, Mark Brenner, David A Hodell, Marcello A. Canuto, Jason H CurtisAbstract:Paleoclimate records indicate a series of severe droughts was associated with societal collapse of the Classic Maya during the Terminal Classic period (∼800–950 C.E.). Evidence for drought largely derives from the drier, less populated northern Maya Lowlands but does not explain more pronounced and earlier societal disruption in the relatively humid southern Maya Lowlands. Here we apply hydrogen and carbon isotope compositions of Plant Wax lipids in two lake sediment cores to assess changes in water availability and land use in both the northern and southern Maya lowlands. We show that relatively more intense drying occurred in the southern lowlands than in the northern lowlands during the Terminal Classic period, consistent with earlier and more persistent societal decline in the south. Our results also indicate a period of substantial drying in the southern Maya Lowlands from ∼200 C.E. to 500 C.E., during the Terminal Preclassic and Early Classic periods. Plant Wax carbon isotope records indicate a decline in C4 Plants in both lake catchments during the Early Classic period, interpreted to reflect a shift from extensive agriculture to intensive, water-conservative maize cultivation that was motivated by a drying climate. Our results imply that agricultural adaptations developed in response to earlier droughts were initially successful, but failed under the more severe droughts of the Terminal Classic period.
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pre aged Plant Waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records
Geochimica et Cosmochimica Acta, 2014Co-Authors: Peter M J Douglas, Timothy I. Eglinton, Mark Pagani, Mark Brenner, David A Hodell, Jason H Curtis, Keith F, Andy BreckenridgeAbstract:Sedimentary records of Plant-Wax hydrogen (dDWax) and carbon (d 13 CWax) stable isotopes are increasingly applied to infer past climate change. Compound-specific radiocarbon analyses, however, indicate that long time lags can occur between the synthesis of Plant Waxes and their subsequent deposition in marginal marine sediments. The influence of these time lags on interpretations of Plant-Wax stable isotope records is presently unconstrained, and it is unclear whether such time lags also affect lacustrine sediments. We present compound-specific radiocarbon ( 14 CWax) data for n-alkanoic acid Plant Waxes (n-C26 to n-C32) from: (1) a sediment core from Lake Chichancanab, Yucatan Peninsula, Mexico, (2) soils in the Lake Chichancanab catchment, and (3) surface sediments from three other lakes in southeastern Mexico and northern Guatemala. 14 CWax ages in the surface sediments are consistently older than modern, and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area. 14 CWax ages in soils surrounding Lake Chichancanab increase with soil depth, consistent with deep, subsoil horizons being the primary source of lacustrine aged Plant Waxes, which are likely delivered to lake sediments through subsurface transport. Plant Waxes in the Lake Chichancanab core are 350–1200 years older than corresponding ages of bulk sediment deposition, determined by 14 C dates on terrestrial Plant macrofossils in the core. A dDWax time series is in closer agreement with other regional proxy hydroclimate records when a Plant-Wax 14 C age model is applied, as opposed to the macrofossil-based core chronology. Inverse modeling of Plant-Wax age distribution parameters suggests that Plant Waxes in the Lake Chichancanab sediment core derive predominantly from millennial-age soil carbon pools that exhibit relatively little age variance (<200 years). Our findings demonstrate that high-temporal-resolution climate records inferred from stable isotope measures on Plant Waxes in lacustrine sediments may suffer from possible chronologic distortions as a consequence of long residence times of Plant Waxes in soils. They also underscore the importance of direct radiocarbon dating of these organic molecules.
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Pre-aged Plant Waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records
Geochimica et Cosmochimica Acta, 2014Co-Authors: Peter M J Douglas, Timothy I. Eglinton, Mark Pagani, Mark Brenner, David A Hodell, Jason H Curtis, Keith F, Andy BreckenridgeAbstract:Sedimentary records of Plant-Wax hydrogen (dDWax) and carbon (d 13 CWax) stable isotopes are increasingly applied to infer past climate change. Compound-specific radiocarbon analyses, however, indicate that long time lags can occur between the synthesis of Plant Waxes and their subsequent deposition in marginal marine sediments. The influence of these time lags on interpretations of Plant-Wax stable isotope records is presently unconstrained, and it is unclear whether such time lags also affect lacustrine sediments. We present compound-specific radiocarbon ( 14 CWax) data for n-alkanoic acid Plant Waxes (n-C26 to n-C32) from: (1) a sediment core from Lake Chichancanab, Yucatan Peninsula, Mexico, (2) soils in the Lake Chichancanab catchment, and (3) surface sediments from three other lakes in southeastern Mexico and northern Guatemala. 14 CWax ages in the surface sediments are consistently older than modern, and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area. 14 CWax ages in soils surrounding Lake Chichancanab increase with soil depth, consistent with deep, subsoil horizons being the primary source of lacustrine aged Plant Waxes, which are likely delivered to lake sediments through subsurface transport. Plant Waxes in the Lake Chichancanab core are 350–1200 years older than corresponding ages of bulk sediment deposition, determined by 14 C dates on terrestrial Plant macrofossils in the core. A dDWax time series is in closer agreement with other regional proxy hydroclimate records when a Plant-Wax 14 C age model is applied, as opposed to the macrofossil-based core chronology. Inverse modeling of Plant-Wax age distribution parameters suggests that Plant Waxes in the Lake Chichancanab sediment core derive predominantly from millennial-age soil carbon pools that exhibit relatively little age variance (
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14C and 13C characteristics of higher Plant biomarkers in Washington margin surface sediments
Geochimica et Cosmochimica Acta, 2013Co-Authors: Xiaojuan Feng, Daniel B. Montluçon, Bryan C. Benitez-nelson, Fredrick G. Prahl, Ann P. Mcnichol, Daniel J. Repeta, Timothy I. EglintonAbstract:Abstract Plant Wax lipids and lignin phenols are the two most common classes of molecular markers that are used to trace vascular Plant-derived OM in the marine environment. However, their 13 C and 14 C compositions have not been directly compared, which can be used to constrain the flux and attenuation of terrestrial carbon in marine environment. In this study, we describe a revised method of isolating individual lignin phenols from complex sedimentary matrices for 14 C analysis using high pressure liquid chromatography (HPLC) and compare this approach to a method utilizing preparative capillary gas chromatography (PCGC). We then examine in detail the 13 C and 14 C compositions of Plant Wax lipids and lignin phenols in sediments from the inner and mid shelf of the Washington margin that are influenced by discharge of the Columbia River. Plant Wax lipids (including n -alkanes, n -alkanoic (fatty) acids, n -alkanols, and n -aldehydes) displayed significant variability in both δ 13 C (−28.3‰ to −37.5‰) and Δ 14 C values (−204‰ to +2‰), suggesting varied inputs and/or continental storage and transport histories. In contrast, lignin phenols exhibited similar δ 13 C values (between −30‰ and −34‰) and a relatively narrow range of Δ 14 C values (−45‰ to −150‰; HPLC-based measurement) that were similar to, or younger than, bulk OM (−195‰ to −137‰). Moreover, lignin phenol 14 C age correlated with the degradation characteristics of this terrestrial biopolymer in that vanillyl phenols were on average ∼500 years older than syringyl and cinnamyl phenols that degrade faster in soils and sediments. The isotopic characteristics, abundance, and distribution of lignin phenols in sediments suggest that they serve as promising tracers of recently biosynthesized terrestrial OM during supply to, and dispersal within the marine environment. Lignin phenol 14 C measurements may also provide useful constraints on the vascular Plant end member in isotopic mixing models for carbon source apportionment, and for interpretation of sedimentary records of past vegetation dynamics.
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Rapid analysis of 13C in Plant-Wax n-alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments
Geochemistry Geophysics Geosystems, 2004Co-Authors: Kelsey E Mcduffee, Timothy I. Eglinton, Alex L Sessions, Sean P Sylva, Thomas Wagner, J M HayesAbstract:Long-chain, odd-carbon-numbered C25 to C35 n-alkanes are characteristic components of epicuticular Waxes produced by terrestrial higher Plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total Plant-Wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straight-chain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO4. Short-chain n-alkanes of nonvascular Plant origin (
Kelsey E Mcduffee - One of the best experts on this subject based on the ideXlab platform.
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Rapid analysis of 13C in Plant-Wax n-alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments
Geochemistry Geophysics Geosystems, 2004Co-Authors: Kelsey E Mcduffee, Timothy I. Eglinton, Alex L Sessions, Sean P Sylva, Thomas Wagner, J M HayesAbstract:Long-chain, odd-carbon-numbered C25 to C35 n-alkanes are characteristic components of epicuticular Waxes produced by terrestrial higher Plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total Plant-Wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straight-chain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO4. Short-chain n-alkanes of nonvascular Plant origin (
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rapid analysis of 13c in Plant Wax n alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments
Geochemistry Geophysics Geosystems, 2004Co-Authors: Timothy I. Eglinton, Kelsey E Mcduffee, Alex L Sessions, Sean P Sylva, Thomas Wagner, J M HayesAbstract:Long-chain, odd-carbon-numbered C25 to C35 n-alkanes are characteristic components of epicuticular Waxes produced by terrestrial higher Plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total Plant-Wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straight-chain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO4. Short-chain n-alkanes of nonvascular Plant origin (
J M Hayes - One of the best experts on this subject based on the ideXlab platform.
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Rapid analysis of 13C in Plant-Wax n-alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments
Geochemistry Geophysics Geosystems, 2004Co-Authors: Kelsey E Mcduffee, Timothy I. Eglinton, Alex L Sessions, Sean P Sylva, Thomas Wagner, J M HayesAbstract:Long-chain, odd-carbon-numbered C25 to C35 n-alkanes are characteristic components of epicuticular Waxes produced by terrestrial higher Plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total Plant-Wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straight-chain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO4. Short-chain n-alkanes of nonvascular Plant origin (
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rapid analysis of 13c in Plant Wax n alkanes for reconstruction of terrestrial vegetation signals from aquatic sediments
Geochemistry Geophysics Geosystems, 2004Co-Authors: Timothy I. Eglinton, Kelsey E Mcduffee, Alex L Sessions, Sean P Sylva, Thomas Wagner, J M HayesAbstract:Long-chain, odd-carbon-numbered C25 to C35 n-alkanes are characteristic components of epicuticular Waxes produced by terrestrial higher Plants. They are delivered to aquatic systems via eolian and fluvial transport and are preserved in underlying sediments. The isotopic compositions of these products can serve as records of past vegetation. We have developed a rapid method for stable carbon isotopic analyses of total Plant-Wax n-alkanes using a novel, moving-wire system coupled to an isotope-ratio mass spectrometer (MW-irMS). The n-alkane fractions are prepared from sediment samples by (1) saponification and extraction with organic solvents, (2) chromatographic separation using silica gel, (3) isolation of straight-chain carbon skeletons using a zeolite molecular sieve, and (4) oxidation and removal of unsaturated hydrocarbons with RuO4. Short-chain n-alkanes of nonvascular Plant origin (