Search

The National Environmental Isotope Facility (NEIF) Radiocarbon Laboratory at the Scottish Universities Environmental Research Centre (SUERC) performs radiocarbon measurement of a wide range of sample matrices for applications in environmental research. Radiocarbon is applied to palaeoenvironmental, palaeoceanographic, and palaeoclimatic investigations, as well as work to understand the source, fate, turnover, and age of carbon in the modern carbon cycle. The NEIF Radiocarbon Laboratory supports users in the development and deployment of novel sampling techniques and laboratory approaches. Here, we give an overview of methods and procedures used by the laboratory to support the field collection, laboratory processing, and measurement of samples. This includes in-house development of novel and/or specialized methods and approaches, such as field collection of CO2 and CH4, hydropyrolysis, and ramped oxidation. The sample types covered include organic remains (e.g., plant material, peat, wood, charcoal, proteins), carbonates (e.g., speleothems, foraminifera, mollusc shell, travertine), waters (dissolved organic and inorganic carbon), gases (CO2 and CH4), soils and sediments (including sub-fractions). [ABSTRACT FROM AUTHOR]

Radiocarbon (14C) measurements undertaken by the NERC Radiocarbon Laboratory using accelerator mass spectrometry (AMS) are now freely available on a new online database. The data presented covers measurement of the wide range of sample types that are processed for research projects in the fields of Earth and environmental science, supported by the United Kingdom's Natural Environment Research Council. Sample types within the database include organic remains, soils, sediments, carbonates, dissolved organic and inorganic carbon, and carbon dioxide. Currently, the database contains 14C data for over 2400 individual samples that were measured and reported between 2005 and 2013, but it is envisaged that this will expand considerably as more data are made available. Contextual information such as sampling location and associated publications are provided where available, and searches can be performed on sample location, sample type, project number, and publication code. This new database compliments an existing, publicly available database of measurements performed using radiometric methods by the laboratory which has recently been expanded to present over 2000 measurements. It is hoped that this archive will prove useful to workers in the community who would benefit from greater availability of measurements for particular locations or sample types, and for the purposes of performing meta-analyses, and/or synthesis of larger datasets. [ABSTRACT FROM AUTHOR]

Freshwater ecosystems are responsible for a large proportion of global methane emissions to the atmosphere. The radiocarbon (14C) content of this aquatic methane is useful for determining the age and source of this important greenhouse gas. Several methods already exist for the collection of aquatic methane for radiocarbon analysis, but they tend to only sample over short periods of time, which can make them unsuitable for characterizing aquatic methane over longer timespans, and vulnerable to missing short-term events. Here, we describe a new time-integrated method for the collection of aquatic methane that provides samples suitable for radiocarbon analysis, that are representative for periods of up to at least 16 days. We report the results of a suite of tests undertaken to verify the reliability of the method, and the 14C age of aquatic methane from field trials undertaken at sites within Scotland, UK. We believe that this new method provides researchers with a simple approach that is easily deployable and can be used to collect representative time-integrated samples of methane for radiocarbon analysis from a wide range of aquatic environments. [ABSTRACT FROM AUTHOR]

Sample materials such as sediments and soils contain complex mixtures of different carbon-containing compounds. These bulk samples can be split into individual fractions, based on the temperature of thermal decomposition of their components. When coupled with radiocarbon (14C) measurement of the isolated fractions, this approach offers the advantage of directly investigating the residence time, turnover time, source, or age of the different components within a mixed sample, providing important insights to better understand the cycling of carbon in the environment. Several laboratories have previously reported different approaches to separate radiocarbon samples based on temperature in what is a growing area of interest within the research community. Here, we report the design and operation of a new ramped oxidation facility for separation of sample carbon on the basis of thermal resistance at the NEIF Radiocarbon Laboratory in East Kilbride, UK. Our new instrumentation shares some characteristics with the previously-reported systems applying ramped oxidation and/or ramped pyrolysis for radiocarbon measurement, but also has several differences which we describe and discuss. We also present the results of a thorough program of testing of the new system, which demonstrates both the reproducibility of the thermograms generated during sample combustion, and the reliability of the radiocarbon measurements obtained on individual sample fractions. This is achieved through quantification of the radiocarbon background and analysis of multiple standards of known 14C content during standard operation of the instrumentation. [ABSTRACT FROM AUTHOR]

Rates of global and regional sea‐level rise between ~1850 and 1950 were high compared to those in preceding centuries. The cause of this sea‐level acceleration remains uncertain, but it appears to be pronounced in a small set of relative sea‐level proxy records from the Southern Hemisphere. Here we generate three new proxy‐based relative sea‐level reconstructions for southeastern Australia to investigate spatial patterns and causes of historical sea‐level changes in the Tasman Sea. Palaeo sea‐level estimates were determined using salt‐marsh foraminifera as sea‐level indicators. Records are underpinned by chronologies based on accelerator mass spectrometry 14C, radiogenic lead (210Pb), stable lead isotopes and palynological analyses. Our reconstructions show that relative sea level rose by ~0.2–0.3 m over the last 200 years in southeastern Australia, and rates of sea‐level rise were especially high over the first half of the 20th century. Based on modelled estimates of the contributing components to sea‐level rise, we suggest that the episode of rapid sea‐level rise was driven by barystatic contributions, but sterodynamic contributions were dominant by the mid‐20th century. Significant spatial variability in relative sea level indicates that local to sub‐regional drivers of sea level are also prominent. Our reconstructions significantly enhance our understanding of the spatiotemporal pattern of early 20th century sea‐level rise in the region. [ABSTRACT FROM AUTHOR]

Methane is the second most important anthropogenically produced greenhouse gas, and radiocarbon (14C) analysis is extremely valuable in identifying its age and source in the environment. At the NERC Radiocarbon Facility (East Kilbride, UK) we have developed expertise in analysis of methane 14C concentration and methodological approaches to field sampling over the past 20 years. This has opened a wide range of applications, which have mainly focused on (1) the age and source of methane emitted by peatlands and organic soils (e.g. to quantify the release of ancient carbon), (2) the source of aquatic emissions of methane, and (3) the age of methane generated by amenity and illegal landfill. Many of these scientifically important applications involve challenging sampling and measurement considerations, which our development program has continually aimed to overcome. Here, we describe our current methods, and recent improvements to aid field collection of samples in remote locations. We present the results of tests which (1) show the effectiveness of our methods to remove contaminants, especially CO2, (2) quantify the 14C background contribution, and (3) demonstrate the reliability of metal gas storage canisters for sample storage. [ABSTRACT FROM AUTHOR]

Carbon dioxide evasion from inland waters such as lakes, rivers and streams represents a significant component of the global carbon cycle, yet in many parts of the world, relatively little is known about its source. Radiocarbon dating of aquatic CO2 has the potential to provide new insights into C cycling in the terrestrial-aquatic-atmosphere continuum, and whilst a range of methods are available for the collection of samples for 14C analysis, they all have limitations or disadvantages (e.g. slow collection rates and potential non-equilibrium). These issues are further compounded in remote field sites. Here, we describe a new method for the field collection of CO2 samples from low-pH waters (pH < 7) for radiocarbon analysis, which involves a scaled-up version of the widely used headspace equilibration technique coupled with syringe injection of samples into molecular sieve traps for convenient and stable storage. We present the results of laboratory and field tests to verify this 'super headspace method' and discuss its advantages compared with existing techniques, particularly for sampling in remote locations. This includes its high portability, speed of use and absence of any special sample preservation requirements. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Clinical measurement of intracranial pressure ( ICP) is often performed to aid diagnosis of hydrocephalus. This review discusses analysis of ICP and its components' for the investigation of cerebrospinal fluid ( CSF) dynamics. The role of pulse, slow and respiratory waveforms of ICP in diagnosis, prognostication and management of hydrocephalus is presented. Two methods related to ICP measurement are listed: an overnight monitoring of ICP and a constant-rate infusion study. Due to the dynamic nature of ICP, a 'snapshot' manometric measurement of ICP is of limited use as it might lead to unreliable results. Therefore, monitoring of ICP over longer time combined with analysis of its waveforms provides more detailed information on the state of pressure-volume compensation. The infusion study implements ICP signal processing and CSF circulation model analysis in order to assess the cerebrospinal dynamics variables, such as CSF outflow resistance, compliance of CSF space, pressure amplitude, reference pressure, and CSF formation. These parameters act as an aid tool in diagnosis and prognostication of hydrocephalus and can be helpful in the assessment of a shunt malfunction. [ABSTRACT FROM AUTHOR]

Peatland streams typically contain high methane concentrations and act as conduits for the release of this greenhouse gas to the atmosphere. Radiocarbon analysis provides a unique tracer that can be used to identify the methane source, and quantify the time elapsed between carbon fixation and return to the atmosphere as CH4. Few studies - those that have focus largely on sites with bubble (ebullition) emissions - have investigated the 14C age of methane in surface waters because of the difficulty in collecting sufficient CH4 for analysis. Here, we describe new sampling methods for the collection of CH4 samples from CH4-oversaturated peatland streams for radiocarbon analysis. We report the results of a suite of tests, including using methane 14C standards and replicated field measurements, to verify the methods. The methods are not restricted to ebullition sites, and can be applied to peatland streams with lower methane concentrations. We report the 14C age of methane extracted from surface water samples (~4-13 l) at two contrasting locations in a temperate raised peat bog. Results indicate substantial spatial variation with ages ranging from ~400 (ditch in afforested peatland) to ~3000 years BP (bog perimeter stream). These contrasting ages suggest that methane in stream water can be derived from a wide range of peat depths. This new method provides a rapid (10-15 min per sample) and convenient approach, which should make 14CH4 dating of surface water more accessible and lead to an increased understanding of carbon cycling within the soil-water-atmosphere system. © 2015 The Authors. Ecohydrology published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

Knowing the rate at which carbon is cycled is crucial to understanding the dynamics of carbon transfer pathways. Recent technical developments now support measurement of the 14C age of evaded CO2 from fluvial systems, which provides an important "fingerprint" of the source of C. Here we report the first direct measurements of the 14C age of effluxed CO2 from two small streams and two rivers within the western Amazonian Basin. The rate of degassing and hydrochemical controls on degassing are also considered. We observe that CO2 efflux from all systems except for the seasonal small stream was 14C-depleted relative to the contemporary atmosphere, indicating a contribution from "old" carbon fixed before ~ 1955 AD. Further, "old" CO2 was effluxed from the perennial stream in the rainforest; this was unexpected as here connectivity with the contemporary C cycle is likely greatest. The effluxed gas represents all sources of CO2 in the aquatic system and thus we used end-member analysis to identify the relative inputs of fossil, modern and intermediately aged C. The most likely solutions indicated a contribution from fossil carbon sources of between 3 and 9 % which we interpret as being derived from carbonate weathering. This is significant as the currently observed intensification of weather has the potential to increase the future release of old carbon, which can be subsequently degassed to the atmosphere, and so renders older, slower C cycles faster. Thus 14C fingerprinting of evaded CO2 provides understanding which is essential to more accurately model the carbon cycle in the Amazon Basin. [ABSTRACT FROM AUTHOR]

Radiocarbon isotopes are increasingly being used to investigate the age and source of carbon released from peatlands. Here we use combined C and δC measurements to determine the isotopic composition of soil and soil decomposition products [dissolved organic carbon (DOC), CO and CH] in a peatland-riparian-stream transect, to establish the isotopic signature and potential connectivity between carbon pools. Sampling was conducted during two time periods in 2012 to investigate processes under different temperature, hydrological and flux conditions. Isotopic differences existed in the peatland and riparian zone soil organic matter as a result of the riparian depositional formation. The peatland had a mean radiocarbon age of 551 ± 133 years BP, with age increasing with depth, and δC values consistent with C3 plant material as the primary source. In contrast the riparian zone had a much older radiocarbon age of 1,055 ± 107 years BP and showed no age/depth relationship; δC in the riparian zone was also consistent with C3 plant material. With the exception of DOC in September, soil decomposition products were predominately >100 %modern with C values consistent with derivation from organic matter fixed in the previous 5 years. Emissions of CO and CH from the soil surface were also modern. In contrast, CO and CH evaded from the stream surface was older (CH: 310-537 years BP, CO: 36 years BP to modern) and contained a more complex mix of sources combining soil organic matter and geogenic carbon. The results suggest considerable vertical transport of modern carbon to depth within the soil profile. The importance of modern recently fixed carbon and the differences between riparian and stream isotopic signatures suggests that the peatland (not the riparian zone) is the most important source of carbon to stream water. [ABSTRACT FROM AUTHOR]

Cartridges containing a zeolite molecular sieve are used for the field collection of CO2 from a variety of environments (e.g. atmosphere, soil respiration, evasion from surface waters) for accelerator mass spectrometry (AMS) radiocarbon analysis by the NERC Radiocarbon Facility. Previously, sample CO² was recovered from the sieves by heating under vacuum prior to cryogenic purification and graphitization. An additional heating and evacuation stage was used to prepare the cartridge for the next sample. We have recently developed an alternative method using heating and purging with nitrogen gas to remove sample CO2 from the molecular sieve. An infrared gas analyzer (IRGA) is used to continuously monitor CO2 content in the purge gas. The preparation of the molecular sieve cartridge for the next use is performed simultaneously and the IRGA reading is used to verify that all sample CO2 has been removed from the sieve, ensuring insignificant carryover of CO2 into the next sample. We present the results of a suite of standards of distinctly different 14C and stable-carbon isotope composition, which we used to confirm the reliability of the new procedure. The new method has considerably reduced the time required to process a single sample from at least 2 hr to less than 40 min, and reduced the minimum sample size by 50%. [ABSTRACT FROM AUTHOR]