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Absolute determination of the activity of two 14C dating standards
... Estimation of the fossil fuel CO2 basically comes from two mass balance equations, for CO2 and 14 C (or 14 CO2), which are presented in the concentration form (or, more often, in the mixing ratio form; the mixing ratio is defined as = / , where is a CO2 density and is the air density) (10) where the superscripts stand for, respectively, the observed ( obs ) mixing ratio, background ( bg ) mixing ratiowithout the local fossil fuel emission, fossil fuel ( ff ) mixing ratio, biosphere (photosynthesis and heterotrophic respiration) component ( bio ), and other components, like those coming from burning of biomass, nuclear industry or ocean ( other ). The 14 C isotope is typically measured as a relative difference between the ( 13 C corrected) sample and absolute rate [40,65] (11) where the absolute (abs) value is the absolute radiocarbon standard (1.176ˑ10 -12 mol 14 C/molC), related to oxalic acid activity. Equation (11) is usually expressed in per mill (‰) and written as As the concentration (and mixing ratio) of 14 C in the fossil fuel CO2 is equal to 0, then from (11) we have Δ 14 Cff = −1000. ...
... We run the G4M model for a number of CO2 price scenarios: initial prices starting in 2020 (0, 1,3,5,10,15,20,25,30,40,50,60,80, 100, 120 USD/tCO2) and rising 5% per year (that results in CO2 price range of 4-520 USD/ton CO2 in 2050) using standard parameter values as in [2]. For the purposes of sensitivity analysis we vary the values cr, w, and l mentioned above: we decrease/increase them by 1, 2.5, 5, 10, 50 and 90% (only single parameter was changed during a run). ...
Spatial inventory of greenhouse gas (GHG) emissions allows to identify emission changes in space. In this study we have analyzed the specificity of territorial distribution of GHG emission sources for Poland and Ukraine. Mathematical models and geoinformation technology for spatial analysis of GHG emissions from fuel consumption by power and combined heat and power plants have been improved by taking into account uncertainty of input parameters and specific factors for every separate electricity/ heat generating companies. We have updated the input digital maps of emission point sources. Based on it, we have developed a spatial GHG emission distribution for 2012. The uncertainties of GHG emissions in CO2-equivalent for the power plants which we consider in our study are asymmetric and the upper bounds of 95% confidence intervals do not exceed 20,3%.
... DI 14 C is used as normalized concentration in order to minimize the numerical error of carrying very small numbers. The normalization is done by dividing the real DI 14 C by the standard ratio of 14 C / 12 C = 1.176 × 10 −12 (Karlen et al., 1968). To obtain comparable DI 14 C values as measured, we multiply the simulated DI 14 C by this scaling factor of 1.176 × 10 −12 . ...
... As for the abiotic radiocarbon, we use scaled variables for 13 C and 14 C in order to minimize the numerical error of carrying very small numbers (particularly for 14 C). The scaling factor is the commonly used standard iso C / 12 C for each isotope, i.e., 1.12372 × 10 −8 for iso = 13 C (Craig, 1957) and 1.176×10 −12 for iso = 14 C (Karlen et al., 1968). This means that we use 13 R Std = 1 and 14 R Std = 1 in the code, and that the model-simulated isotopic carbon pools are multiplied by the respective scaling factor to compare them with observations. ...
Carbon isotopes in the ocean are frequently used as paleoclimate proxies and as present-day
geochemical ocean tracers. In order to allow a more direct comparison of climate model results
with this large and currently underutilized data set, we added a carbon isotope module to the ocean
model of the Community Earth System Model (CESM), containing the cycling of the stable isotope
13C and the radioactive isotope 14C. We implemented the 14C tracer
in two ways: in the "abiotic" case, the 14C tracer is only subject to air–sea gas
exchange, physical transport, and radioactive decay, while in the "biotic" version, the
14C additionally follows the 13C tracer through all biogeochemical and
ecological processes. Thus, the abiotic 14C tracer can be run without the ecosystem
module, requiring significantly fewer computational resources. The carbon isotope module calculates
the carbon isotopic fractionation during gas exchange, photosynthesis, and calcium carbonate
formation, while any subsequent biological process such as remineralization as well as any
external inputs are assumed to occur without fractionation. Given the uncertainty associated with
the biological fractionation during photosynthesis, we implemented and tested three
parameterizations of different complexity. Compared to present-day observations, the model is able
to simulate the oceanic 14C bomb uptake and the 13C Suess effect reasonably
well compared to observations and other model studies. At the same time, the carbon isotopes reveal
biases in the physical model, for example, too sluggish ventilation of the deep Pacific Ocean.
... Thus, the range goes from 2.7mg carbon required to fill a 5m1 `micro' to 1 atmosphere with CO2 or CH4, to ca 80mg to fill a 30m1 `mini' to 5 atmospheres (Table 1). Following from this, taking the disintegration rate of "modern" carbon as 13.56dpm/g (Karlen et al, 1966), the comparable counting time in days to obtain the precisions, in this case, just Poisson counting statistics on the sample count, is shown in Table 2. These are clearly minimum times, as there is more to an error estimate than simply the counting statistics. ...
... The underlying reason for lack of precision seems to have been the Currie, Noakes & Breiter (1978) *Normalized to `modern' as 13.56 dpm/g (Karlen et al, 1966) unfavorable signal:background ratios; signal, meaning the count rate obtained for an equivalent modern sample (the ratio refers to modern: background therefore here). Table 3 shows very reasonable values of background (B) for counters of the volumes (V) compared to the ultimate estimated theoretical background values (B = 0.013 V23) (Oeschger & Loosli, 1975) but modern:background ratios of only around unity. ...
Miniature gas counters have been in use since the early 1960s for the measurement of 14 C but were for a long time seen as suitable for providing approximate indications of activity rather than measurements for more precise dates. In recent years the need for better measurements of small samples has posed a continuing challenge for the 14 C laboratories. This paper examines how the challenge has been met across the world using conventional beta decay counting techniques and proportional gas counters of 50ml volume or less. A survey is made of the rise of these techniques and attention paid to the solution through modern technology of earlier problems. Some practical systems, now in routine use, are described and consideration is given to the future for miniature counter measurements. Such systems have several attractive features that will guarantee their usefulness in 14 C measurements for the future.
... DI 14 C is used as normalized concentration in order to minimize the numerical error of carrying very small numbers. The normalization is done by dividing the real DI 14 C by the standard ratio of 14 C/ 12 C = 1.176 × 10 −12 (Karlen et al., 1968). To obtain comparable DI 14 C values as measured, we multiply the simulated DI 14 C by this scaling factor of 1.176×10 −12 . ...
... i.e., 1.12372 × 10 −8 for iso = 13 C (Craig, 1957) and 1.176 × 10 −12 for iso = 14 C (Karlen et al., 1968). This means that we use 13 R Std = 1 and 14 R Std = 1 in the code, and that the model simulated isotopic carbon pools are multiplied by the respective scaling factor to compare them with observations. ...
Carbon isotopes in the ocean are frequently used as paleo climate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized dataset, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM), containing the cycling of the stable isotope 13C and the radioactive isotope 14C. We implemented the 14C tracer in two ways: in the "abiotic" case, the 14C tracer is only subject to air–sea gas exchange, physical transport, and radioactive decay, while in the "biotic" version, the 14C additionally follows the 13C tracer through all biogeochemical and ecological processes. Thus, the abiotic 14C tracer can be run without the ecosystem module, requiring significantly less computational resources. The carbon isotope module calculates the carbon isotopic fractionation during gas exchange, photosynthesis, and calcium carbonate formation, while any subsequent biological process such as remineralization as well as any external inputs are assumed to occur without fractionation. Given the uncertainty associated with the biological fractionation during photosynthesis, we implemented and tested three parameterizations of different complexity. Compared to present-day observations, the model is able to simulate the oceanic 14C bomb uptake and the 13C Suess effect reasonably well compared to observations and other model studies. At the same time, the carbon isotopes reveal biases in the physical model, for example a too sluggish ventilation of the deep Pacific Ocean.
... 14 C is a cosmogenic radionuclide, which is produced by secondary cosmic-ray neutrons interacting with nitrogen in the atmosphere. The 14 C produced rapidly oxidized in the atmosphere to CO 2 , where it becomes well-mixed there and enters to the carbon cycle (Lal and Suess 1958;Damon 1968;Karlen et al. 1968;Kutschera 2019Kutschera , 2013. ...
Biobased content analysis is a well-established, analytically independent, standardized method to determine the biobased content of fuels and plastics, based on differences of the specific radiocarbon (14C) activity of fossil and recent biogenic compounds. This biogenic content analysis can be useful for the producers as a quality assurance tool, for the customers as feedback about the truly biobased products and for the control organizations as an independent analytical tool to prove the biological origin. More than 100 commercially available foods, cosmetics, and drug samples have been used for biobased carbon content analysis by accelerator mass spectrometry (AMS) 14C measurement to demonstrate the potential of this technique. Our results show that this measurement technique is a unique tool for the determination of biocontent in foodstuff and medical products. Most of the tested materials were nearly or completely biobased (≥ 98 pMC), and no completely fossil-based final product was detected. The lowest biogenic compound was measured in a vanilla aroma flavor. In 45 of the 102 samples selected a wide range (2–98%) presented fossil-based carbon content. The method can be applied for monitoring raw materials and final products for biobased content in the industry and consumer protection as well.
... (F 14 C), which is a measurement of the deviation of a sample's radiocarbon content from that of the "modern" standard (Donahue et al., 1990;Reimer et al., 2004). "Modern" is defined as 95% of the radiocarbon concentration (in AD 1950) of NBS Oxalic Acid I, normalized to δ 13 C VPDB (δ 13 C VPDB = À19‰; Karlen et al., 1964;Olsson, 1970). A correction to F 14 C is made to normalize the sample result to a δ 13 C VPDB value of À25‰, assuming a quadratic mass fractionation dependency using simultaneously measured 13 C/ 12 C ratios on the AMS system. ...
Age validation is a critical component of an age‐based stock assessment and subsequent species management. Our study used bomb radiocarbon analysis to validate age estimates of Blueline Tilefish Caulolatilus microps, a species for which regional stock assessment scientists have identified age validation as a high priority. We compared a C. microps F¹⁴C chronology to F¹⁴C chronologies for finfish of the U.S. South Atlantic Bight (SAB) and the north‐west Atlantic. The high degree of correspondence in the chronologies exhibited for C. microps and other species of the SAB suggests a differential ¹⁴C uptake pattern in the SAB slope waters that is likely the result of local hydrological processes that delay ¹⁴C reaching the environments inhabited by these species. Our study was able to validate C. microps ages up to 25 years in the SAB, with strong evidence suggesting they are living to at least 50 years old.
... A 14 C bétasugárzó radioaktív izotóp, felezési ideje 5700±30 év. ßbomlással, egy elektron és egy antineutrínó kibocsátásával nitrogén 14-re ( 14 N) bomlik (Karlen et al., 1968;Kutschera, 2019Kutschera, , 2013. ...
Radiocarbon (14C) has an important role both in the environment and climate research as well as in radiocarbon dating. As a natural tracer, radiocarbon can be applied to differentiate fossil or modern derived inorganic and organic compounds. Although fossil materials do not contain radiocarbon, recent modern materials have a well-measurable radiocarbon content as they are closely related to the atmospheric carbon dioxide. In certain cases, different methods apart from the isotope analysis cannot be applied to discriminate the two sources, like in the case of the discrimination of fossil and modern CO2 emissions (Suess, 1955). The method is not only applicable for discrimination of emission sources, but also in industry for the investigation of materials containing fossil and bio components as well, like plastic and fuel samples (Oinonen et al., 2010). In addition, the 14C emission of nuclear facilities can be investigated, as the 14C/12C ratio of nuclear emission are easily distinguishable from the natural background (Zhang et al., 2021). Plants collect and fix the carbon from the atmospheric CO2 by the photosynthesis, for this reason, some plant organic material, like cellulose, well represent the local atmospheric 14C/12C ratio of CO2 in the year of the production (Rakowski, 2011; Richardson et al., 2013). Based on this, plant materials (tree rings and leaves) can be applied to high spatial and temporal resolution passive sampling in urban and rural areas or around nuclear power plants, for recent and retrospective investigations. By this method, areas can be investigated, where instrumental sampling is not possible or would be very costly. Furthermore, the method is applicable to signals of extraterrestrial events, that cannot be performed by ordinary instrumental sampling, like investigation of 14C fingerprints of the supernova explosions in tree ring samples, which are over a thousand years old (Miyake et al., 2012)
My presented PhD work was performed in the Eövtös Lóránd Research Network, Institute for Nuclear Research (ATOMKI), Isotope Climatology and Environmental Research Centre (ICER). In my research I was aiming to develop and apply accelerator mass spectrometry (AMS) based radiocarbon measurement methods that have not been applied in Hungary for environmental research. My aim was mapping the fossil carbon load in urban and background areas with high spatial resolution without instrumental air sampling, based on plant samples in Hungary (Debrecen) and Indonesia (Bali). In addition, I aimed to determine the effect of the Fukushima nuclear accident for the level of 14C in tree ring samples, 50 km west from the Fukushima Nuclear Power Plant. Beside nuclear emission, my research aim was also the investigation of the 14C fingerprints of natural cosmic events in tree ring samples. I tried to reproduce a previously published rapid 14C increase event in tree ring samples produced between 3351-3392 BCE. Furthermore, I wanted to expand the application of the applied 14C methods for such type materials that have not been investigated in Hungary before, such as fuel and honey samples. By these studies, in addition to radiocarbon dating, my aim was to open new perspectives in the Hungarian radiocarbon research, that can be the base of long-term researches in the future and open new research directions.
... The last counter (C31) presented performances lower than those of the C24 counter (C24) with a background of 1.67 cpm. Background level and NIST Oxalic Acid I activity (Karlen et al. 1964) at LSM are reported in Table 1. The comparison of the background levels shows a reduction of 65 to 85% of this parameter at LSM compared to Gif-sur-Yvette. ...
In 1991, a ¹⁴ C ß-counting installation with four proportional CO 2 gas counters was tested at the Modane underground laboratory, 1700 m below the summit of Pointe du Fréjus, reducing the muon flux to 4 muons per square meter and per day. With cosmic radiation attenuated by a factor of 2.10 ⁶ , the background level of the counters was reduced by 65 to 85% while its variability was reduced by a factor of 30–80 depending on the type of counter. The dating limit of these counters extends to well beyond 60,000 years.
... where ( 14 C/ 12 C) Sample denotes the 14 C : 12 C ratio of the sample, and A ABS denotes the 14 C : 12 C ratio of the standard. A ABS is set to be 1.176 × 10 −12 (Karlen et al., 1965;Stuiver, 1980). The 14 C input can then be calculated as ...
There is increasing recognition that lateral soil organic carbon (SOC) fluxes due to erosion have imposed an important impact on the global C cycling. Field and experimental studies have been conducted to investigate this topic. It is useful to have a modeling tool that takes into account various soil properties and has flexible resolution and scale options so that it can be widely used to study relevant processes and evaluate the effect of soil erosion on SOC cycling. This study presents a model that is capable of simulating SOC cycling in landscapes that are subjected to erosion. It considers all three C isotopes (12C, 13C and 14C) with flexible time steps and a detailed vertical solution of the soil profile. The model also represents radionuclide cycling in soils that can assist in constraining the lateral and vertical redistribution of soil particles within landscapes. The model gives a three-dimensional representation of soil properties including 137Cs activity, SOC stock, and δ13C and Δ14C values. Using the same C cycling processes in stable, eroding and depositional areas, our model is able to reproduce the observed spatial and vertical patterns of C contents, δ13C values, and Δ14C values. This indicates that at the field scale with a similar C decomposition rate, physical soil redistribution is the main cause of the spatial variability of these C metrics.
... RafterRadiocarbon.co.nz). Measurements were provided as Δ 14 C (‰), defined as the deviation of 14 C/ 12 C of the sample relative to a 95% NBS oxalic acid standard, and corrected for the year of formation (Karlen et al. 1964;Stuiver and Polach 1977). Based on the results of Kalish (1993), a Δ 14 C value below −40‰ to −50‰ represents an environment where the bomb-produced radiocarbon signal has yet to appear. ...
Black oreo (Allocyttus niger) and smooth oreo (Pseudocyttus maculatus) are commercially exploited deepwater fishes in New Zealand. They are considered to be long-lived with unvalidated maximum otolith growth zone counts of 153 years and 86 years, respectively. Bomb radiocarbon dating results supported the otolith age estimates for A. niger, but those for P. maculatus provided only partial support. Oxygen isotope (δ¹⁸O) results for A. niger otoliths suggested that juveniles were in near-surface waters and adults in depths of 700–1300 m. In contrast, P. maculatus otoliths suggested a variable depth history (500 to at least 1500 m) throughout life. Carbon isotope (δ¹³C) results showed a steady enrichment from core values to c. 20 years for both species, owing to changes in diet and metabolic rate from the juvenile to the adult fish, associated with a depth increase. Von Bertalanffy growth parameters are provided for both species.
... The variables requested for CMIP6 are stocks and fluxes of 14 C and 13 C from any model including 14 C or 13 C in the land or ocean component. Stocks and fluxes of 14 C should be reported with a normalization factor of 1 / Rs, where Rs is the standard 14 C / C ratio, 1.176 × 10 −12 (Karlen et al., 1965), whereas 13 C should be reported without normalization. For the ocean, the variables requested are the net air-sea fluxes of 14 C and 13 C and the dissolved inorganic 14 C and 13 C concentration (Jones et al., 2016;Orr et al., 2017). ...
The isotopic composition of carbon (Δ14C and δ13C) in
atmospheric CO2 and in oceanic and terrestrial carbon reservoirs is
influenced by anthropogenic emissions and by natural carbon exchanges, which
can respond to and drive changes in climate. Simulations of 14C and
13C in the ocean and terrestrial components of Earth system models
(ESMs) present opportunities for model evaluation and for investigation of
carbon cycling, including anthropogenic CO2 emissions and uptake. The
use of carbon isotopes in novel evaluation of the ESMs' component ocean and
terrestrial biosphere models and in new analyses of historical changes may
improve predictions of future changes in the carbon cycle and climate system.
We compile existing data to produce records of Δ14C and
δ13C in atmospheric CO2 for the historical period 1850–2015.
The primary motivation for this compilation is to provide the atmospheric
boundary condition for historical simulations in the Coupled Model
Intercomparison Project 6 (CMIP6) for models simulating carbon isotopes in
the ocean or terrestrial biosphere. The data may also be useful for other
carbon cycle modelling activities.
... The same units used for carbon should be used for carbon-13 and carbon-14. Stocks and fluxes of carbon-14 should be normalized with the standard 14 C / C ratio, Rs, of 1.176×10 −12 (Karlen et al., 1968). This means that reported stocks and fluxes of carbon-14 should be divided by Rs. ...
Coordinated experimental design and implementation has become a cornerstone of global climate modelling. Model Intercomparison Projects (MIPs) enable systematic and robust analysis of results across many models, by reducing the influence of ad hoc differences in model set-up or experimental boundary conditions. As it enters its 6th phase, the Coupled Model Intercomparison Project (CMIP6) has grown significantly in scope with the design and documentation of individual simulations delegated to individual climate science communities.
The Coupled Climate–Carbon Cycle Model Intercomparison Project (C4MIP) takes responsibility for design, documentation, and analysis of carbon cycle feedbacks and interactions in climate simulations. These feedbacks are potentially large and play a leading-order contribution in determining the atmospheric composition in response to human emissions of CO2 and in the setting of emissions targets to stabilize climate or avoid dangerous climate change. For over a decade, C4MIP has coordinated coupled climate–carbon cycle simulations, and in this paper we describe the C4MIP simulations that will be formally part of CMIP6. While the climate–carbon cycle community has created this experimental design, the simulations also fit within the wider CMIP activity, conform to some common standards including documentation and diagnostic requests, and are designed to complement the CMIP core experiments known as the Diagnostic, Evaluation and Characterization of Klima (DECK).
C4MIP has three key strands of scientific motivation and the requested simulations are designed to satisfy their needs: (1) pre-industrial and historical simulations (formally part of the common set of CMIP6 experiments) to enable model evaluation, (2) idealized coupled and partially coupled simulations with 1 % per year increases in CO2 to enable diagnosis of feedback strength and its components, (3) future scenario simulations to project how the Earth system will respond to anthropogenic activity over the 21st century and beyond.
This paper documents in detail these simulations, explains their rationale and planned analysis, and describes how to set up and run the simulations. Particular attention is paid to boundary conditions, input data, and requested output diagnostics. It is important that modelling groups participating in C4MIP adhere as closely as possible to this experimental design.
... Every group of samples processed included an appropriate blank, namely a Johnson-Mathey 99.9999% graphite powder, which was analyzed concurrently with the group. ally accepted modern value of 1.176 ± 0.010 × 10 -12 (Karlén et al. 1968), and a final 13 C correction is made to normalize the sample F m to a δ 13 C VPDB value of -25‰. Stable isotope measurements of sample δ 13 C used to correct F m values were made with either a VG PRISM or VG OPTIMA mass spectrometer by analyzing subsamples of the CO 2 gas generated during graphite production. ...
In the Great Basin of North America, big sagebrush ( Artemisia tridentata Nutt.) growth rings can be used to reconstruct environmental changes with annual resolution in areas where there is otherwise little such information available. We tested the annual nature of big sagebrush wood layers using accelerator mass spectrometry (AMS) radiocarbon dating. Four cross-sections from 3 sagebrush plants were collected near Ely, Nevada, USA, and analyzed using dendrochronological methods. Ten 14 C measurements were then used to trace the location of the 1963–64 “bomb spike.” Although the number of rings on each section did not exceed 60, crossdating was possible within a section and between sections. Years assigned to individual wood layers by means of crossdating aligned with their expected 14 C values, matching the location of the 14 C peak. This result confirmed the annual nature of growth rings formed by big sagebrush, and will facilitate the development of spatially explicit, well-replicated proxy records of environmental change, such as wildfire regimes, in Great Basin valleys.
... The radioactivities typically used in tracer experiments can be several million times modern levels and very small residual amounts can contaminate samples collected for the measurement of natural levels of 14 C. Table 3.2 details the concentration differences between natural levels and those typically found in productivity measurements. Because of the difficulties in methodology and the potential for cross-contamination, great care and Karlen et al., 1964). The productivity work abundance is based on published JGOFS protocols for measuring primary productivity (Karl et al., 1996). ...
... The differences in photosynthetic pathways lead to variations in the natural isotopic contents of plants and make it possible to trace their origin in the SOC pool (Ryan et al. 1995). In nature, carbon is represented by three isotopes ( 12 C, 13 C, and 14 C) of which the stable forms, 12 C and 13 C, account for nearly 98.89 and 1.11 % of the total, respectively (Karlén et al. 1968). The presence of three very distinct photosynthetic pathways among terrestrial plants (C 3 , C 4 , and CAM) enables them to show a preferential and varying discrimination towards 13 C during carbon assimilation (Cernusak et al. 2009). ...
Long-term storage of soil organic carbon (SOC) is essential for sustainability of agricultural ecosystems and maintaining overall environment quality as soils contain a significant part of global carbon stocks. In this study, we attempted to explain the carbon mineralization and temperature sensitivity of SOC in maize–wheat systems, a common cropping system in the semi-arid regions of India. Soil samples(0–0.15 m) from long-term experimental plots laid in split plot design with two tillage systems (conventional tillage and bed planting) and six nutrient management treatments (T
1 = control, T
2 = 120 kg urea—N/ha, T
3 = T2 (25 % N substituted by farmyard manure (FYM)), T
4 = T
2 (25 % N substituted by sewage sludge), T
5 = T
2 + crop residue, T
6 = 100 % recommended doses of N through organic source - 50 % FYM + 25 % biofertilizer + 25 % crop residue) were incubated at different temperatures (25, 30, 35, and 40 °C) to determine the thermal sensitivity parameters associated with carbon mineralization. Earlier reports suggest a selective preservation of C3-derived carbon fractions over C4 in the SOC pool, and this is the first instance where δ
13C signatures (C4-derived carbon) were used as a qualitative measure to assess thermal sensitivity of SOC pools in the maize—wheat crop rotation systems of semi-arid India. Among the nutrient management treatments, mineral fertilizers were found to add more C4-derived carbon to the SOC pool in both the tillage systems but shows less promise in SOC stability as indicated by their lower activation energies (Ea) (14.25 kJ mol−1). Conventional tillage was found to mineralize 18.80 % (T
1—control at 25 °C) to 29.93 % carbon (T
3—mineral fertilizer + FYM at 40 °C) during the 150 days of incubation which was significantly higher than bed planting system (14.90 % in T
1—control at 25 °C and 21.99 % in T
6—100% organic sources at 40 °C). Organic manures, especially FYM (19.11 kJ mol−1) and 100 % organics (19.33 kJ mol−1) were more effective in enhancing the Ea of SOC than plots with mineral fertilizers alone (14.25 kJ mol−1), but had relatively higher Q
10 values thereby corroborating the thermal sensitivity hypothesis of recalcitrant organic compounds in soil. Michaelis–Menten derivatives along with thermal sensitivity indicators such as Ea and Q
10 were found to be efficient parameters for explaining carbon mineralization and CO2 efflux from soils.
... This problem can be avoided by using the 14 C isotopic content as a tracer for CO 2 ff. CO 2 ff contains no 14 C: the half-life of 14 C is 5730 years (Karlen et al., 1968 ) and all of the 14 C has decayed away from fossil fuels. Other sources of CO 2 have roughly the same 14 C content as the atmosphere. ...
We examine the utility of tree ring 14C archives for detecting long-term
changes in fossil CO2 emissions from a point source. Trees assimilate
carbon from the atmosphere during photosynthesis, in the process faithfully
recording the average atmospheric 14C content in each new annual tree
ring. Using 14C as a proxy for fossil CO2, we examine interannual
variability over six years of fossil CO2 observations between 2004–2005
and 2011–2012 from two trees growing near the Kapuni Gas Treatment
Plant in rural Taranaki, New Zealand. We quantify the amount of
variability that can be attributed to transport and meteorology by simulating
constant point-source fossil CO2 emissions over the observation period
with the atmospheric transport model WindTrax. We compare model simulation
results to observations and calculate the amount of change in emissions that
we can detect with new observations over annual or multi-year time periods,
given both the measurement uncertainty of 1ppm and the modelled variation in
transport. In particular, we ask, what is the minimum amount of change in
emissions that we can detect using this method, given a reference period of
six years? We find that changes of 42 % or more could be detected in a
new sample from one year at the same observation location or 22 % in the
case of four years of new samples. This threshold is reduced and the method
becomes more practical the more the size of the signal increases. For point
sources 10 times larger than the Kapuni plant (a more typical size for power
plants worldwide), it would be possible to detect sustained emissions changes
on the order of 10 %, given suitable meteorology and observations.
... Measurements were provided as D 14 C, defined as the deviation of the sample 14 C activity (i.e. the normalised 14 C isotopic ratio) from 0.95 times the activity of the oxalic acid standard, expressed in parts per million (Karlen et al. 1964;Stuiver and Polach 1977). ...
Black cardinalfish (Epigonus telescopus, Apogonidae) is an important component of deepsea commercial fishing activity in the New Zealand region. It is estimated to live longer than 100 years on the basis of counts of unvalidated annual growth zones in otoliths. Age-validation procedures for long-lived fishes are often one of the following two techniques: (1) lead-radium disequilibria, which uses the natural decay of radium-226 into lead-210 as a natural clock; or (2) bomb radiocarbon (D14C) dating, which relies on the marine signal created by nuclear testing. The high estimated lifespan, as well as the large size of the otolith core region, make E. telescopus an excellent candidate for a combined application of these two independent age-validation techniques. The lead-radium dating using otolith cores indicated that growth-zone counts less than ,60 years were consistent with radiometric ages, whereas higher counts appeared to be under-estimates. There was 95% confidence that maximum age was at least 95 years. The validation indicated that fish aged over 60 years tended to be under-aged by up to 30%. The bomb radiocarbon levels in otolith cores supported age estimates up to ,40 years made from zone counts, and by inference from the zone counts validated with lead-radium dating, longevity exceeds 100 years. Journal compilation.
... The same units used for carbon should be used for carbon-13 and carbon-14. Stocks and fluxes of carbon-14 should be normalized with the standard ratio of 1.176 x 10 -12 (Karlen et al. 1968). 10 ...
Coordinated experimental design and implementation has become a cornerstone of global climate modelling. So-called Model Intercomparison Projects (MIPs) enable systematic and robust analysis of results across many models to identify common signals and understand model similarities and differences without being hindered by ad-hoc differences in model set-up or experimental boundary conditions. The activity known as the Coupled Model Intercomparison Project (CMIP) has thus grown significantly in scope and as it enters its 6th phase, CMIP6, the design and documentation of individual simulations has been devolved to individual climate science communities. The Coupled Climate-Carbon Cycle Model Intercomparison Project (C4MIP) takes responsibility for design, documentation and analysis of carbon cycle feedbacks and interactions in climate simulations. These feedbacks are potentially large and play a leading order contribution in determining the atmospheric composition in response to human emissions of CO2 and in the setting of emissions targets to stabilise climate or avoid dangerous climate change. For over a decade C4MIP has coordinated coupled climate-carbon cycle simulations and in this paper we describe the C4MIP simulations that will be formally part of CMIP6. While the climate-carbon cycle community has formed this experimental design the simulations also fit into the wider CMIP activity and conform to some common standards such as documentation and diagnostic requests and are designed to complement the CMIP core experiments known as the DECK. C4MIP has 3 key strands of scientific motivation and the requested simulations are designed to satisfy their needs: (1) pre-industrial and historical simulations (formally part of the common set of CMIP6 experiments) to enable model evaluation; (2) idealised coupled and partially-coupled simulations with 1 % per year increases in CO2 to enable diagnosis of feedback strength and its components; (3) future scenario simulations to project how the Earth System will respond over the 21st century and beyond to anthropogenic activity. This paper documents in detail these simulations, explains their rationale and planned analysis, and describes how to set-up and run the simulations. Particular attention is paid to boundary conditions and input data required, and also the output diagnostics requested. It is important that modelling groups participating in C4MIP adhere as closely as possible to this experimental design.
... Fraction Modern (Fm) is a measurement of the deviation of the 14C/C ratio of a sample from "modern." Modern is defined as 95% of the radiocarbon concentration (in AD 1950) of NBS Oxalic Acid I normalized to 613CVPDB = -19 per mil (Olsson, 1970). AMS results are calculated using the internationally accepted modern value of 1.176 +0.010 x 10-12 (Karlen, et. al., 1968) and a final 13C correction is made to normalize the sample Fm to a 613CVPDB value of -25 per mil. ...
... A ° et A t sont exprimés en pour cent de carbone moderne (pcm), avec 100 pcm =13,56 ± 0,07 désin- tégration par minute et par gramme de carbone (Karlen et al., 1964 L'activité agricole, l'intensité du pompage et le contact direct entre l'aquifère plio-quaternaire et la lagune de Oualidia, constituent autant de facteurs pouvant favoriser la salinisation des eaux souterrai- nes par des intrusions marines. L'examen de la relation δ 2 H/ δ 18 O, montre que la contamination marine est très localisée. ...
The study area «Haouz plain» is Located at the center of Morocco, it extend on a surface of 2800 km2, limited by the Jbilet hills in the North, the High-Atlas range in the South, R' dat wadi in the East and the Essaouira-Chichaoua plateau in the West. The area climate is semi-arid, characterized by low precipitations varying between 160 mm/ year and 250mm/year and important variation in temperature between the winter and the summer with respectively 5°C and 45°C. Its hydrographic network is represented by the Tensift system which receives all the affluents of central and Western Haouz. These affluents are characterized by weak flows with important seasonal variations. The Hao uz plain is a sedimentary basin, being along the northern edge of the high atlas, it presents a geologic succession going from the primary to the recent Quaternary. The mio-plioquaternary formations, stemming from the dismantling of the atlasic chain, refuge an important and generalized water table on all the plain. This water table shows very variable hydrodynamic characteristics, reflecting the complexity of the deep structures of the plain, 1986) and also the lithological variability of the mio-plioquaternary formations. The Haouz plain inclu des also the deep reservoirs of the Jurassic, Cretaceous and Eocene which finish some meters at the north of the Atlas, thus having a, very limited extension and thereafter a low productivity. Five representative samples of water taken on the haouz water table were analyzed by the ABHT, the projection of these contents on the potability diagram enabled us to show that water of the water table generally has a good quality to passable. In the east quality becomes poor related to the existence of a zone arranged for agriculture (piezometer 1903/44). The nastiest potability is observed on the piezometer 3828/44 located at north of Marrakech at elazouzia zone of spreading of worn water of this city. The representation of the percent ages of anions and major cations shows the prevalence of ions Ca2+ and HCO3- and makes it possible to show up the Bicarbonate calcic facies of the water table. During these last decades, the use of stable isotopes, such oxygen 18 and deuterium, became necessary for the study of subsoil waters, it makes possible the estimation of the surfaces of refills, the determination of water origin. The samples taken on water points well distributed in the area of study allowed us a better comprehension of the function of the plioquaternary water table. The relation oxygen 18, deuterium shows that water is aligned on a line of slope 8.09, slightly different from the world meteoric line, thus characterizing precipitations of oceanic origin which did not endure notable isotopic fractionation therefore not important evaporation. Using the isotopic m easures for the samples taken in January 2002 on wells well distributed in the area of study, allows us to show a variation of the contents of 018 with the altitude of the zones of refill. Thus we could delimit the surfaces of refill between 1500 and 800meters height. The relation oxygen-18 deuterium ∂2H = 8.0932 ∂18O + 14.214 (R2 = 0.7449) translated an Atlantic mode of precipitations without remarkable evaporation.
... In further action, the meeting adopted the AD 1950 absolute NBS oxalic acid disintegration rate of 14.27 ± 0.07 disintegrations per minute per gram of carbon. This corresponds with an activity for 95 percent of oxalic acid of 13.56 ± 0.07 disintegrations per minute per gram carbon, which gives a 14C/C ratio of (1.176 ± 0.010) 10-12 (Karlen andothers, 1968, first reported in 1964). The above activities are normalized on an oxalic acid 813CPDB value of -19 per mil. ...
The purpose of the workshop was to clarify any possible confusion related to the reporting 14 C data. Two areas of concern, the use of the new NBS oxalic acid standard (Cavallo and Mann, 1980), and the reporting of marine sample ages, were singled out for detailed discussions.
... where the superscripts stand for, respectively, the observed ( obs ) mixing ratio, background ( bg ) mixing ratio -without the local fossil fuel emission, fossil fuel ( ff ) mixing ratio, biosphere (photosynthesis and heterotrophic respiration) component ( bio ), and other components, like those coming from burning of biomass, nuclear industry or ocean ( other ). The 14 C isotope is typically measured as a relative difference between the ( 13 C corrected) sample and absolute rate (Karlen et al., 1968;Stuiver and Polach, 1977) (11) where the absolute (abs) value is the absolute radiocarbon standard (1.176ˑ10 -12 mol 14 C/molC), related to oxalic acid activity. Equation (11) is usually expressed in per mill (‰) and written as (12) After some transformation the following final equation can be obtained (13) From (9), the concentration of one component can be calculated and inserted to (13). ...
Because of the G4M model non-linearity marginal abatement cost curves (MACCs) are
sensitive to variation of the model parameters, irrespective of the fact that the same parameter
variations are applied in both zero-CO2 price and non-zero-CO2 price runs. Since integrated
assessment models in general are complex computer models with non-linearity one may
expect all MACCs constructed using such models are sensitive to variation of the model
parameters. The MACCs constructed using G4M are much more sensitive to parameter
variation at a certain range of CO2 prices, usually low CO2 prices. The MACCs for total
biomass CO2 emissions constructed using G4M are most sensitive to variation of corruption
coefficient (measuring efficiency of use of abatement costs) and, on the second place, to
agriculture land price. Experts applying MACCs for policy analysis must be aware of
uncertainty features of the MACCs as the uncertainty can influence the outcome of the
analysis.
... 14 C is defined by Stuiver and Pollach (1977) and Stuiver (1980) where 14 C values ≥ 0 are completely modern OC and reported as "modern"; 14 C values < 0 indicate the presence varying proportions of old carbon. "Modern" is conventionally defined as 95 % of the 14 C activity of an oxalic acid standard for AD 1950 (Karlen et al., 1964). The fraction of carbon in a sample that is modern, f m , ranges fromf m values > 1 (if 14 C from atmospheric nuclear bomb testing is present) to 0 (containing no measurable 14 C). ...
Rivers are the primary means by which sediments and carbon are transported from the terrestrial biosphere to the oceans but gaps remain in our understanding of carbon associations from source to sink. Bed sediments from the Sacramento-San Joaquin River Delta (CA) were fractionated according to density and analyzed for sediment mass distribution, elemental (C and N) composition, mineral surface area, and stable carbon and radiocarbon isotope compositions of organic carbon (OC) and fatty acids to evaluate the nature of organic carbon in river sediments. OC was unevenly distributed among density fractions. Mass and TOC were in general concentrated in mesodensity (1.6–2.0 and 2.0–2.5 g cm−3) fractions, comprising 84.0 ± 1.3 % of total sediment mass and 80.8 ± 13.3 % of total OC (TOC). Low density (< 1.6 g cm−3) material, although rich in OC (34.0 ± 2.0 % OC) due to woody debris, constituted only 17.3 ± 12.8 % of TOC. High density (> 2.5 g cm−3) organic-poor, mineral material made-up 13.7 ± 1.4 % of sediment mass and 2.0 ± 0.9 % of TOC. Stable carbon isotope compositions of sedimentary OC were relatively uniform across bulk and density fractions (δ13C −27.4 ± 0.5 ‰). Radiocarbon content varied from Δ14C values of −382 (radiocarbon age 3800 yr BP) to +94 ‰ (modern) indicating a~mix of young and pre-aged OC. Fatty acids were used to further constrain the origins of sedimentary OC. Short-chain n-C14–n-C18 fatty acids of algal origin were depleted in δ13C (δ13C −37.5 to −35.2 ‰) but were enriched in 14C (Δ14C > 0) compared to long-chain n-C24–n-C28 acids of vascular plant origins with higher δ13C (−33.0 to −31.0 ‰) but variable Δ14C values (−180 and 61 ‰). These data demonstrate the potentially complex source and age distributions found within river sediments and provide insights about sediment and organic matter supply to the Sacramento-San Joaquin River Delta.
... A ° et A t sont exprimés en pour cent de carbone moderne (pcm), avec 100 pcm =13,56 ± 0,07 désin- tégration par minute et par gramme de carbone (Karlen et al., 1964 L'activité agricole, l'intensité du pompage et le contact direct entre l'aquifère plio-quaternaire et la lagune de Oualidia, constituent autant de facteurs pouvant favoriser la salinisation des eaux souterrai- nes par des intrusions marines. L'examen de la relation δ 2 H/ δ 18 O, montre que la contamination marine est très localisée. ...
Morocco is classified as an arid to semi-arid country with a population
according to 2013 estimates of 35 million inhabitants and a growth rate of 1,4
%. Efficient use of Morocco’s scarce water is becoming increasingly important
as the urban population grows. This study concerns the groundwater recharge in
the Kourimat basin and describes a combined methodology for groundwater
recharge estimation in Morocco, through the isotopic and hydrochemical
approaches.
Groundwater samples from Essaouira basin, east Morocco, falls along the
Global Meteoric Water Line (GMWL), and below the Local Meteoric Water
Line (LMWL), suggesting that the waters have been recharged under a different
climatic regime, different from today.
Water isotopic composition shows low evaporation of precipitations during
infiltration. Depletion in heavy isotopes is the characteristic of mountain
rainfalls or of a climate colder and wetter than present at the research area.
Carbon-14 activities (30 – 60 pMC) indicate a long residence time.
Tritium levels in the groundwater of the Kourimat Basin are below the detection
limit (<1.5 TU). Five groundwater samples in South-West of Essaouira city,
presents tritium content between 1 and 3 TU.
Keywords: Kourimat Basin, Arid climate, groundwater resources, stable and
radioactive isotopes, Morocco.
... A ° et A t sont exprimés en pour cent de carbone moderne (pcm), avec 100 pcm =13,56 ± 0,07 désin- tégration par minute et par gramme de carbone (Karlen et al., 1964 L'activité agricole, l'intensité du pompage et le contact direct entre l'aquifère plio-quaternaire et la lagune de Oualidia, constituent autant de facteurs pouvant favoriser la salinisation des eaux souterrai- nes par des intrusions marines. L'examen de la relation δ 2 H/ δ 18 O, montre que la contamination marine est très localisée. ...
Climate aridity and intensive exploitation due to uncontrolled pumping for
irrigation have caused a drastic decrease in the piezometric level aquifers of
ouazzi basin plain, and have seriously degraded groundwater quality.
Overexploitation of coastal aquifers and pollution vulnerability are among the
main problems related to groundwater resources assessment and management in
arid and semi-arid regions threatened by desertification being the only source
for agricultural and public water supply.
The overall objective of this study is to identify the possible human impact on
groundwater quality, and the elaboration of a conceptual circulation model of
Essaouira coastal aquifer (W Morocco).
A study was conducted, having as main goal the characterization of the
groundwater evolution from the chemical and isotopic point of view from the
recharge areas towards the coast line. Groundwater samples from Plio-
Quaternary and Turonian aquifers were collected and analysed: i) variable
electric conductivity from 900 μs/cm to 3880 μs/cm with similar Cl-Na facies;
ii) carbon-14 varies from30 to 60 pMC, with3H levels (Ouazzi Basin) below the
detection limit, SW of Essaouira city, tritium content range between 1.5 and 3
TU.
Keywords: Wadi Ouazzi, Arid climate, Groundwater resources, Environmental
isotopes, Morocco.
... A ° et A t sont exprimés en pour cent de carbone moderne (pcm), avec 100 pcm =13,56 ± 0,07 désin- tégration par minute et par gramme de carbone (Karlen et al., 1964 L'activité agricole, l'intensité du pompage et le contact direct entre l'aquifère plio-quaternaire et la lagune de Oualidia, constituent autant de facteurs pouvant favoriser la salinisation des eaux souterrai- nes par des intrusions marines. L'examen de la relation δ 2 H/ δ 18 O, montre que la contamination marine est très localisée. ...
Climate aridity and intensive exploitation due to uncontrolled pumping for
irrigation have caused a drastic decrease in the piezometric level aquifers of
ouazzi basin plain, and have seriously degraded groundwater quality.
Overexploitation of coastal aquifers and pollution vulnerability are among the
main problems related to groundwater resources assessment and management in
arid and semi-arid regions threatened by desertification being the only source
for agricultural and public water supply.
The overall objective of this study is to identify the possible human impact on
groundwater quality, and the elaboration of a conceptual circulation model of
Essaouira coastal aquifer (W Morocco).
A study was conducted, having as main goal the characterization of the
groundwater evolution from the chemical and isotopic point of view from the
recharge areas towards the coast line. Groundwater samples from Plio-
Quaternary and Turonian aquifers were collected and analysed: i) variable
electric conductivity from 900 μs/cm to 3880 μs/cm with similar Cl-Na facies;
ii) carbon-14 varies from30 to 60 pMC, with3H levels (Ouazzi Basin) below the
detection limit, SW of Essaouira city, tritium content range between 1.5 and 3
TU.
Keywords: Wadi Ouazzi, Arid climate, Groundwater resources, Environmental
isotopes, Morocco.
... After the death of an organism, the 14 C in its tissues is no longer refilled through direct or indirect exchange with atmospheric CO 2, and undergoes radioactive decay back to 14 N. If the plants or animals tissues remain intact and isolated from exchange, the decrease in its 14 C content (expressed as a ratio of 14 C/ 12 C) from that in living organism, may be used to indicate the time since the death of the organism (figure II.11) (Trumbore, 2000 Calculation of a radiocarbon age requires the assumption that the 14 C content of the carbon originally fixed in plant or animal tissues equalled that of the atmospheric CO 2 (Karlen et al., 1966). There are two major problems with this assumption. ...
This research addresses interactions between tectonics, climate and geomorphic processes at the surface of the Earth through the study of river terraces in Venezuela and Albania. Both areas have been exposed to moderate uplift, to Quaternary climatic variations and provide a wide record of river terraces. These contexts furnish opportunities to investigate the dynamics of terraces formation at 102-105 year time scale. Thus, a morphochronologic approach was applied in order to achieve greater understanding about this issue for the Venezuelan and Albanian rivers. In the Pueblo Llano and Santo Domingo rivers system located in the Southeastern flank of the Mérida Andes in Venezuela, twelve river terraces were identified for the last 200 ka. Analysis of 10Be concentration provides for the first time exposure ages for seven terraces and for one frontal moraine complex. A terraces model supported by these dating and geomorphologic, stratigraphic and sedimentologic data indicates that the formation of terraces was mainly controlled by high frequency (103-104 years) climatic variations through unsteady discharge of water and sediments. Nevertheless, the type of response was highly related to the altitude of the site and the influence of usptreams glaciers. As a matter of fact, in the upper reaches of the system, the succession of aggradation and incision phases were synchronized with the succession of cold-dry and warm-humid periods, while the lower reaches of the system show the opposite pattern. Based on the temporal restoration of the incision rate of the lower reaches of the system an uplift rate at 1.1 mm/a for the last 70 ka was estimated for the Southeastern flank of the MA. Additionally, the identification and dating of a frontal moraine complex located at elevation of 2300 m a.s.l. in the Pueblo Llano valley highlights the fact that the glacier advance during the Last Glacial Maximum, in other areas of the MA could have also reached lower elevation than those reported between 2900 and 3500 m a.s.l. In the Albania domain, the terrace records of the six main Albanian rivers were analyzed. New geomorphologic and geochronological data were integrated with published data in order to propose a regional homogeneous stratigraphic/chronologic framework for the last 200 ka. Based on this framework the timing of formation of eleven regional river terraces was established. In Albania, the processes of terraces formation were also mainly controlled by high frequency (103-104 years) climatic variations. Nonetheless, the results also show that the geomorphic responses of the fluvial systems were probably modulated by the size of the catchments and by eustatic variations. Indeed, for the pre-Marine Isotope Stage 2 (MIS 2) period, fill and strath terraces were formed in the large and small catchments, respectively. After the beginning of the MIS 2, a complex relation between climatic and eustatic variations only favored the development of strath terraces in large and small catchments. Despite of the differences between the rivers responses, the succession of aggradation or lateral erosion and incision phases were synchronized with the succession of cold-dry and warm-humid periods in all the rivers of Albania. Finally, the restoration of spatial and temporal variation of incision rate allowed: 1) identify the spatial variation of the mean long-term incision rate. It varies from less than 0.1 mm/a in Southern Albania to 1 mm/a in Northern Albania; 2) estimate vertical slip rates for eight active faults for the last 19 ka in Southern Albania. These vertical slip rates appear to decrease from ~2 to ~0.1 mm/a from the extensional domain in the Eastern Albania to the compressional domain in Western Albania.
... A ° et A t sont exprimés en pour cent de carbone moderne (pcm), avec 100 pcm =13,56 ± 0,07 désin- tégration par minute et par gramme de carbone (Karlen et al., 1964 L'activité agricole, l'intensité du pompage et le contact direct entre l'aquifère plio-quaternaire et la lagune de Oualidia, constituent autant de facteurs pouvant favoriser la salinisation des eaux souterrai- nes par des intrusions marines. L'examen de la relation δ 2 H/ δ 18 O, montre que la contamination marine est très localisée. ...
The present study aims at characterizing the hydrogeochemistry and the piézomètrie of the
basin of Mejjate (Haouz Western, Morocco) in the objective to contribute to the development
of the potential in resources of this arid region to semi-arid. It is based on the compilation and
the interpretation of the whole of the data available. The first phase of study shows the quality
of surface waters and those underground. The study of facies highlight two different chemical
groupings (Ground water and deep tablecloth). According to the piézomètrie, the effects of the
last years of drynesses A contributes a considerable fall of the water level (deficit general of
about 320 l/s). The objectives of the SIG are mainly a generalization of the geological and
hydrogeologic space information of the studied site and the integration of this one in layers of
the digital model, while ensuring the transparency of the model by the creation of charts sets
of themes (altitude, slope and hydrographic network, occupation of the grounds).
Observations of radiocarbon ( ¹⁴ C) in Earth’s atmosphere and other carbon reservoirs are important to quantify exchanges of CO 2 between reservoirs. The amount of ¹⁴ C is commonly reported in the so-called Delta notation, i.e., Δ ¹⁴ C, the decay- and fractionation-corrected departure of the ratio of ¹⁴ C to total C from that ratio in an absolute international standard; this Delta notation permits direct comparison of ¹⁴ C/C ratios in the several reservoirs. However, as Δ ¹⁴ C of atmospheric CO 2 , Δ ¹⁴ CO 2 is based on the ratio of ¹⁴ CO 2 to total atmospheric CO 2 , its value can and does change not just because of change in the amount of atmospheric ¹⁴ CO 2 but also because of change in the amount of total atmospheric CO 2 , complicating ascription of change in Δ ¹⁴ CO 2 to change in one or the other quantity. Here we suggest that presentation of atmospheric ¹⁴ CO 2 amount as mole fraction relative to dry air (moles of ¹⁴ CO 2 per moles of dry air in Earth’s atmosphere), or as moles or molecules of ¹⁴ CO 2 in Earth’s atmosphere, all readily calculated from Δ ¹⁴ CO 2 and the amount of atmospheric CO 2 (with slight dependence on δ ¹³ CO 2 ), complements presentation only as Δ ¹⁴ CO 2 , and can provide valuable insight into the evolving budget and distribution of atmospheric ¹⁴ CO 2 .
This is a detailed study on oxide (CO2) and reduced (hydrocarbons, CnHm) forms of ¹⁴C releases through gaseous effluents from the Kaiga nuclear power plant (NPP), on the West Coast of India, where 4 × 220 MW(e) pressurized heavy water reactors (PHWRs) are operating. The gaseous effluent from the common stack of reactor units 3 and 4 (each of 220 MW(e)) was sampled from 2017 to 2020 for ¹⁴C activity monitoring and analysed for ¹⁴C activity by liquid scintillation counting. The normalized release rate corresponding to the four-year monitoring period had a geometric mean value of 0.12 TBq GW(e)⁻¹ a⁻¹ (geometric standard deviation = 7.4), and the arithmetic mean with associated standard deviation was 0.75 ± 1.47 TBq GW(e)⁻¹ a⁻¹. The relative percentage contribution of reduced form (CH4) of ¹⁴C species was less than 1.27% of the total release. The normalized release rate from Kaiga NPP was similar to those reported for the other PHWR NPPs of the world. The ¹⁴C specific activity in the ambient air in the vicinity of the NPP was monitored at four locations. The maximum excess ¹⁴C activity values in the ambient air in the vicinity of the NPP, evaluated by comparing the specific activity recorded for the clean air region at ∼300 km from the NPP, were 65.1 Bq kg⁻¹C (28.76 pMC) and 222.4 Bq kg⁻¹C (98.23 pMC) for the years 2019 and 2020 respectively. In addition, the release rates were calculated from the Gaussian plume model using site-specific atmospheric dilution factors and the excess ¹⁴C specific activity measured at four off-site monitoring stations. The calculated values of release rates were in agreement (within a factor of ∼3) with the measured values.
A method for the determination of ¹⁴C activity in the ambient air was optimised with the development of a simple setup for the regeneration of CO2 from carbonate sample and saturating the absorber in <45 min for direct determination of activity by liquid scintillation counting (LSC). Atmospheric CO2 was trapped in NaOH solution and precipitated as BaCO3 by adding BaCl2. The carbonate sample was taken in a newly designed regeneration system, subjected to acid hydrolysis, and the absorber (CarboSorb-E) was saturated with the CO2 regenerated from carbonate sample. This allowed optimisation of CO2 absorption by the absorber (up to ∼ 2.3941 g of CO2/10 mL with an average of 2.1688 g) and a minimum detectable activity value of 14 Bq kg⁻¹C for a counting time of 300 min (8 Bq kg⁻¹C for 1000 min) was achieved with Quantulus - 1220 LSC system. The necessity of (i) the measurement of the total volume of air sampled, (ii) the determination of trapping efficiency for CO2 in the NaOH, recovery of ¹⁴C in chemical processing of BaCO3, and subsequent regeneration and absorption processes, and (iii) independent determination of carbon content in the air for expressing the results in terms of ¹⁴C specific activity (Bq kg⁻¹C), are avoided in this method. The method is capable of yielding accurate results, in a considerably short time when compared to previously reported methods, with a deviation of <2.2% from the target value (with a relative standard deviation of 1.1%, and a relative error of 0.53%) when ambient air samples from clean air region (region not affected by local anthropogenic sources of ¹⁴C) are analysed. Validation of the method was performed by (i) analysing BaCO3 sample derived from ambient air by accelerator mass spectrometry, and (ii) analysing the CO2 produced from the combustion of IAEA C3 reference material. Upon validation, the suitability of the method for determining small excess ¹⁴C specific activity in the vicinity of a nuclear power plant was demonstrated.
Geochemical assessment of the Hueco Bolson, New Mexico and Texas, 2016–17
Seagrasses are marine angiosperms that can form highly productive, and valuable underwater meadows, which are currently in regression. A reliable assessment of their status and future evolution requires studies encompassing long-term temporal scales. With the aim of understanding seagrass ecosystem dynamics over the last centuries and millennia, twelve sediment cores were studied from seagrass meadows located along the Andalusian coast and at the Cabrera Island (western Mediterranean). This study is pioneer in using Fourier Transform Infrared (FTIR) spectroscopy as a tool to study environmental change in seagrass sediments. FTIR is a form of vibrational spectroscopy that provides information about the sediment chemical composition. Principal Component Analysis (PCA) was used to summarise spatio-temporal data of the FTIR vibratory peaks in combination with climate and geochemical proxy data. Several PCA signals were identified: (1) one likely related to the relative changes of the main primary producers and the sedimentary environment (carbonate or siliciclastic sediments, with aromatic or aliphatic organic matter); (2) the marine community production (polysaccharides, total organic matter content and biogenic silica); and (3) the seagrass production (aromatics, carbohydrates, phenols, proteins and lipids). A decrease of seagrass production along the mainland coast was evident since AD ~1850, which may be due to combined negative impacts of seawater warming, local anthropogenic impacts, and extreme setting conditions. The legacy of these combined stressors might have influenced the current poor state of seagrass meadows in the Alboran Sea. Our results also revealed a significant long-term trade-off between the level of seagrass production and its temporal stability (calculated as the inverse of the coefficient of variation). This study provides a reliable baseline data, helping to assess the magnitude of seagrass regression and its drivers. This paleoecological information can help design more targeted management plans and identify meadows where local management could be more efficient.
Coastal vegetated “blue carbon” ecosystems can store large quantities of organic carbon (OC) within their soils; however, the importance of these sinks for climate change mitigation depends on the OC accumulation rate (CAR) and residence time. Here we evaluate how two modeling approaches, a Bayesian age‐depth model alone or in combination with a two‐pool OC model, aid in our understanding of the time lines of OC within seagrass soils. Fitting these models to data from Posidonia oceanica soil cores, we show that age‐depth models provided reasonable CAR estimates but resulted in a 22% higher estimation of OC burial rates when ephemeral rhizosphere OC was not subtracted. This illustrates the need to standardize CAR estimation to match the research target and time frames under consideration. Using a two‐pool model in tandem with an age‐depth model also yielded reasonable, albeit lower, CAR estimates with lower estimate uncertainty, which increased our ability to detect among‐site differences and seascape‐level trends. Moreover, the two‐pool model provided several other useful soil OC diagnostics, including OC inputs, decay rates, and transit times. At our sites, soil OC decayed quite slowly both within fast cycling (0.028 ± 0.014 yr⁻¹) and slow cycling (0.0007 ± 0.0003 yr⁻¹) soil pools, resulting in OC taking between 146 and 825 yr to transit the soil system. Further, an estimated 85% to 93% of OC inputs enter slow‐cycling soil pools, with transit times ranging from 891 to 3,115 yr, substantiating the importance of P. oceanica soils as natural, long‐term OC sinks.
The paper presents a review of the methods which can be useful in quantification of greenhouse gas (GHG) emissions at a fine spatial resolution. The discussed approaches include: spatial disaggregation of GHG emissions based on proxy data and/or statistical modeling of spatial correlation, an estimation of fossil fuel emission changes from measuring rates (mixing ratios) of tracer (like \(^{14}\)CO\(_{2}\)) concentrations in the atmosphere, the atmospheric inversion methods, and flux tower observations.
We outline the methodology for detection of carbon dioxide (CO2) leaks to the atmosphere from carbon capture and storage (CCS) using measurements of radiocarbon in CO2. The radiocarbon method can unambiguously identify recently added fossil-derived CO2 such as CCS leaks due to the very large isotopic difference between radiocarbon-free fossil derived CO2 and natural CO2 sources with ambient radiocarbon levels. The detection threshold of 1 ppm of fossil-derived CO2 is comparable to other proposed atmospheric detection methods for CCS leakage. We demonstrate that this method will allow detection of a 1000 ton C yr⁻¹ leak 200–300 m from the source during the day and more than 600 m away at night. Using time-integrated sampling techniques, long time periods can be covered with few measurements, making the method feasible with existing laboratory-based radiocarbon measurement methods We examine the method using previously published observations and new model simulations for a case study in Taranaki, New Zealand. Plant material faithfully records the radiocarbon content of assimilated CO2 and we show that short-lived grass leaves and cellulose from tree rings provide effective time-integrated collection methods, allowing dense spatial sampling at low cost. A CO2 absorption sampler allows collection at controlled times, including nighttime, and gives similar results.
A standard sample (SS) of 14 C-specific β activity has been created based on benzene containing radioactive carbon diluted with “dead” benzene.
Marine transport of inorganic and organic carbon is simulated by means of a computer model in which the oceans are divided into a high and low latitude region. Water transport (and with it carbon transport) is reproduced 1) as downwelling of surface waters at low latitudes, and 2) in general, as different depth-dependent turbulent diffusion in both deep-sea regions. The model is calibrated with pre-bomb 14 C and validated against perturbations of total carbon, 13 C/C- and 14 C/C-ratios; it is compatible with carbon release from fossil fuels and from biogenic sources.
Atmospheric 14 C concentrations vary with time and latitude. These variations, measured directly on atmospheric samples, or in independently-dated organic material such as tree rings, supply data essential for the calibration of dynamic models of the global carbon cycle. Short variations in the production rate of atmospheric 14 C are strongly attenuated in the relatively large atmospheric CO 2 reservoir. In-situ production of 14 C should be negligible for ages up to 80 ka bp. Background problems in AMS dating are more likely attributable to contamination of very small samples.
14 C measured in trace gases in clean air helps to determine the sources of such gases, their long-range transport in the atmosphere, and their exchange with other carbon cycle reservoirs. In order to separate sources, transport and exchange, it is necessary to interpret measurements using models of these processes. We present atmospheric 14 CO 2 measurements made in New Zealand since 1954 and at various Pacific Ocean sites for shorter periods. We analyze these for latitudinal and seasonal variation, the latter being consistent with a seasonally varying exchange rate between the stratosphere and troposphere. The observed seasonal cycle does not agree with that predicted by a zonally averaged global circulation model. We discuss recent accelerator mass spectrometry measurements of atmospheric 14 CH 4 and the problems involved in determining the fossil fuel methane source. Current data imply a fossil carbon contribution of ca 25%, and the major sources of uncertainty in this number are the uncertainty in the nuclear power source of 14 CH 4 , and in the measured value for δ 14 C in atmospheric methane.
The result of a radiocarbon determination is commonly expressed as an age given in radiocarbon years. An error is usually assigned to each value as a measure of the statistical uncertainty of the measurement. Date lists published in this journal use a standard form of reporting dates and their errors (see Editorial Statements in Radiocarbon, v. 3 and v. 4). The conversion of a radiocarbon age, given in radiocarbon years B.P. (i.e., radiocarbon years elapsed since the origin of the sample) to a true calendar year makes necessary certain assumptions with respect to: (1) the half-life of C 14 , (2) the production rate of C 14 by cosmic rays, (3) the size of reservoirs into which C 14 is distributed and the exchange rate of this distribution. Libby (1955, p. 10) has shown that as an approximation one may assume that reservoir size and production and distribution rates, and therefore the C 14 activity in atmospheric CO 2 have been constant. However, the more accurate measurements of recent years have shown that at least one of these quantities must have varied with time. This means that a more complicated relationship exists between radiocarbon age and exact calendar age of a sample than had been assumed by Libby. This relationship cannot be determined theoretically, but can be derived empirically by determination of the radiocarbon contents of samples of known age. The following summarizes our present knowledge regarding differences between radiocarbon ages and true ages and the present status of the empirical calibration of the radiocarbon time scale.
This chapter begins by summarizing some of the recent changes in the global carbon (C) cycle, contrasting patterns that exist today with those of the past several hundred years. With this backdrop, the chapter then examines the overall distribution of C isotopes as a framework for understanding the global C cycle and the changes that are happening to it. These important themes are followed in more detail throughout other chapters of this book, giving insight into C cycling from small to large scales and through all of the important Earth reservoirs.
The radiologic impact of ¹⁴ C produced by the nuclear fuel cycle is assessed at both global and local levels. In the former context, it is predicted here that the specific activity of atmospheric CO 2 in the year 2050 will be ca 7.6 pCig ⁻¹ C. Although this is similar to the present level, the subsequent collective dose commitment could be highly significant.
The enhancement of ¹⁴ C concentrations around the nuclear fuel-reprocessing plant at Sellafield (Windscale) in Cumbria, U K has been monitored over recent years. For example, maximum levels of 27.2 pCig ⁻¹ C (∼350% above natural) during 1984 were observed < 1 km from the plant, with enhanced activities detectable to at least 29km. Nevertheless, it is clear that the radiologic significance to the local population is low. The spatial distribution of the excess ¹⁴ C allows atmospheric dispersion models to be tested in the context of continuous releases and the results thus far show that the Gaussian plume model performs successfully.
A large number of radionuclides are produced in the terrestrial atmosphere as a result of nuclear reactions involving cosmic rays. These comprise very energetic radiation falling upon the Earth from outer space and consisting mainly of charged particles of which the majority are probably protons, although alpha particles and electrons are also present. There is some evidence that approximately 2% of the primary radiation consists of heavy atomic nuclei. Cosmic rays originate from the Sun as well as from galactic sources. Their flux depends upon the kinetic energies of their components which may be as great as 102 GeV (1 GeV = 109 eV); it appears that about half of the flux has a value between 0·5 and 5 GeV.
Gas counting is a mature and powerful technique central to radiocarbon dating. The method was taken from the detection techniques used in nuclear physics and adapted to the special requirements of low-level counting of the carbon gases. A compilation made by W G Mook in 1983 lists 174 gas counters used in 14C dating, the counting gases being CO2 (115 counters), CH4 (38), C2H2 (20) and C2H6 (1). In the present contribution, the current status of CO2 gas counting is reviewed. The emphasis on CO2 is justified by several observations: 1) CO2 is the primary gas to be produced in all methods; 2) routine techniques are able to achieve high purity CO2 gas, so further conversion to hydrocarbons appears unwarranted; 3) the cryogenic properties of CO2 facilitates handling and thus minimizes contamination; 4) all gas counting laboratories involved in high-precision work, eg, for calibration, use CO2 as counting gas. Most of the techniques mentioned in this review were already available around 1975 (see the Proceedings of the Ninth International Radiocarbon Conference (Berger & Suess 1979)); since that time, gas proportional counting has become a routine operating technique in several laboratories. Wherever possible, reference is made to individual laboratories; however, as the more technical aspects of the technique that are central to this chapter are rarely fully documented in the literature, we take most examples from the Heidelberg laboratory, and are fully aware that this description gives heavy weight to a single installation.
The atmospheric testing of nuclear weapons during the 1950s and early 1960s produced large amounts of radiocarbon. This 14C bomb pulse provides useful age information in numerous scientific fields, e.g. in geosciences and environmental sciences. Bomb-pulse dating can also be used to date human material (e.g. in forensics and medical science). Bombpulse dating relies on precise measurements of the declining 14C concentration in atmospheric carbon dioxide collected at clean-air sites. However, local variations in the 14C specific activity of air and foodstuffs occur, which are caused by natural processes as well as by various human activities. As 14C enters the human body mainly through the diet, variations of 14C concentration in foodstuffs need to be considered. The marine component of the diet is believed to be of particular importance due to the non-equilibrium in 14C specific activity between the atmosphere and aquatic reservoirs during the bomb pulse. This article reviews the 14C concentration in marine foodstuffs during the bomb-pulse era, and models how the marine component in one's diet can affect the precision of bomb-pulse dating of human material. © 2010 by the Arizona Board of Regents on behalf of the University of Arizona.
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