Radiocarbon(14C) measurement of dissolved organic carbon(DOC) is a very powerful tool to study the sources, transformation and cycling of carbon in the ocean. The technique, however, remains great challenges for compl...Radiocarbon(14C) measurement of dissolved organic carbon(DOC) is a very powerful tool to study the sources, transformation and cycling of carbon in the ocean. The technique, however, remains great challenges for complete and successful oxidation of sufficient DOC with low blanks for high precision carbon isotopic ratio analysis, largely due to the overwhelming proportion of salts and low DOC concentrations in the ocean. In this paper, we report an effective UV-Oxidation method for oxidizing DOC in natural waters for radiocarbon analysis by accelerator mass spectrometry(AMS). The UV-oxidation system and method show 95%± 4% oxidation efficiency and high reproducibility for DOC in both river and seawater samples. The blanks associated with the method was also low(about 3 μg C) that is critical for 14 C analysis. As a great advantage of the method, multiple water samples can be oxidized at the same time so it reduces the sample processing time substantially compared with other UV-oxidation method currently being used in other laboratories. We have used the system and method for 14 C studies of DOC in rivers, estuaries, and oceanic environments and have received promise results.展开更多
Fast and accurate quantitative detection of ^(14)CO_(2) has impor-tant applications in many elds.The optical detection method based on the sensitive cavity ring-down spectroscopy technol-ogy has great potential.But cu...Fast and accurate quantitative detection of ^(14)CO_(2) has impor-tant applications in many elds.The optical detection method based on the sensitive cavity ring-down spectroscopy technol-ogy has great potential.But currently it has diffculties of insuffcient sensitivity and susceptibility to absorption of other isotopes/impurity molecules.We propose a stepped double-resonance spectroscopy method to excite ^(14)CO_(2) molecules to an intermediate vibrationally excited state,and use cavity ring-down spectroscopy to probe them.The two-photon process signi cantly improves the selectivity of detection.We derive the quantitative measurement capability of double-resonance absorption spectroscopy.The simulation results show that the double-resonance spectroscopy measurement is Doppler-free,thereby reducing the e ect of other molecular absorption.It is expected that this method can achieve high-selectivity detection of ^(14)CO_(2) at the sub-ppt level.展开更多
Radiocarbon content in biogenic samples is widely used to study the variation of atmospheric CO<sub>2</sub> due to anthropogenic activities. A total of 20 samples of several types of tree leaves, were anal...Radiocarbon content in biogenic samples is widely used to study the variation of atmospheric CO<sub>2</sub> due to anthropogenic activities. A total of 20 samples of several types of tree leaves, were analyzed for this study. Sampling was carried out at the end of the rainy season in 2017 from the surrounding of the SOCOCIM cement factory in Rufisque town. Rufisque is located on the peninsula of Cape Verde, 25 km east of Dakar, where it is the 《south gate》 of the agglomeration. Reference samples of five different species were collected during the same period (2017) from a clean zone. The <sup>14</sup>C method was used for the determination of Δ<sup>14</sup>C values. The data show that the <sup>14</sup>C concentration in the studied sites was significantly lower than the clean area, due to the release of anthropogenic CO<sub>2</sub>. To estimate the Suess effect, the fossil fuel fraction was determined based on equations of mass balance for CO<sub>2</sub> concentration, stable isotopic composition of carbon, and <sup>14</sup>C concentration. The results show that selected locations are affected differently according to their distance from the factory and the wind direction.展开更多
The accurately determining the lake ^14C reservoir age has a crucial significance for climatic reconstruction. In this study, the optically stimulated luminescence （OSL） dating method is employed to date samples fro...The accurately determining the lake ^14C reservoir age has a crucial significance for climatic reconstruction. In this study, the optically stimulated luminescence （OSL） dating method is employed to date samples from highstand lacustrine sediments, palaeoshoreline, fluvial terrace, and the alluvial fan of the Heihai Lake catchment. Accelerator mass spectrometry （AMS） 14C dating was also used to date fossil plants from highstand lacustrine sediments. Based on the calculations of linear regression with OSL against radiocarbon ages for same layers of two sections, the quantitative ^14C reservoir ages were estimated to lie between 3 353 and 3 464 yr during the 1.8 to 2.4 ka, which showed temporal variation. The sources of old carbon are the dissolution of carbonate bedrocks distributed along the Kunlun Mountain. The OSL ages of the different members of the hydatogen sedimentary system at Heihai Lake catchment indicate that a stronger hydrologic condition occurred from 3.0±0.2 to 1.8±0.2 ka, with a maximum lake level of 9 m higher than present. This humid stage was widely recorded in different sediments on the QTP and Chinese Loess Plateau （CLP）, indicating its broad synchronicity across the Asian Summer Monsoon region. The enhanced East Asian Summer Monsoon （EASM） and the Indian Summer Monsoon （ISM） resulted in the increase of moisture availability for the Heihai Lake area during this stage.展开更多
Air pollution and climate change are two important threats facing in our planet and are tightly linked to carbonaceous components in the atmosphere.A better understanding of the emission sources and environmental fate...Air pollution and climate change are two important threats facing in our planet and are tightly linked to carbonaceous components in the atmosphere.A better understanding of the emission sources and environmental fate/sink of carbonaceous components is critical for improving our knowledge of the global carbon cycle and mitigating the negative environmental impacts of air pollution and climate change on human well-being.Radiocarbon(^(14)C),which is decayed completely in fossil fuel(e.g.coal and petroleum),is an ideal tool for quantifying the carbon flow in various carbon reservoirs.This study reviews the current knowledge of 14C in organic carbon(OC),elemental carbon(EC),individual organic compounds,methane(CH_(4)),carbon dioxide(CO_(2)),annual plants,and tree rings.The impacts of fossil and non-fossil sources on the atmosphere can be quantified by measuring^(14)C.We also report on the influence of nuclear power plants and sea-air gas exchange on the abundance of^(14)C in the atmosphere.The increasing fossil fuel emissions indicated by the depletion of^(14)CO_(2)under IPCC RCP scenarios,support the urgent need to devise ambitious strategies of reducing carbonaceous components to achieve sustainable development on Earth.This review summarizes the challenges and perspectives of 14C studies of the atmosphere.展开更多
The accurate radiocarbon dating of loess-soil sequences plays an essential role in the reconstruction of the environmental and climatic changes in continental settings during the last glaciation and Holocene. However,...The accurate radiocarbon dating of loess-soil sequences plays an essential role in the reconstruction of the environmental and climatic changes in continental settings during the last glaciation and Holocene. However, our knowledge about the reliability of radiocarbon ages of various fractions of soil and loess samples is still insufficient. Here, we present our study results on radio- carbon ages based on bulk organic matter, humin fraction, and carbonate of samples collected from a loess-paleosol section in the western Chinese Loess Plateau. We compare these observations with the optically stimulated luminescence ages and charcoal radiocarbon ages to evaluate the reliability of these fractions. We observed that the radio- carbon ages of humin fraction are very close to those of charcoal and are consistent with the optically stimulated luminescence ages within the experimental errors. We observed a significant deviation in the radiocarbon ages of carbonate and bulk organic matter from those of charcoal and optically stimulated luminescence ages, likely due to the dilution of these fractions during the pedogenetic process. Our results reveal that, except for charcoal, the humin fraction may yield reliable laC ages for the Chinese loess-soil sequence.展开更多
To meet the measurement demands on small-mass radiocarbon （carbon content at 10.6 g level） which are becoming increasingly significant, Xi＇an-AMS has made improvements to the existing method of sample loading and h...To meet the measurement demands on small-mass radiocarbon （carbon content at 10.6 g level） which are becoming increasingly significant, Xi＇an-AMS has made improvements to the existing method of sample loading and has upgraded the Cs sputter ion source from the original SO-110 model. In order to study the feasibility of small-mass samples in Xi＇an-AMS and evaluate the radiocarbon sample preparation ability using existing routine systems of H2/Fe and Zn/Fe, the small-mass samples prepared by four different methods are tested. They are the mass division method, mass dilution method, H2/Fe reduction method and Zn/Fe reduction method. The results show that carbon mass above 25 μg can be prepared using the existing Zn/Fe system, but no less than 100 μg is required using the existing H2/Fe system, which can be improved. This indicates Xi＇an-AMS are now able to analyze small-mass radiocarbon samples.展开更多
Examining the contribution of fossil fuel CO_(2) to the total CO_(2) changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe,specifically developing countries...Examining the contribution of fossil fuel CO_(2) to the total CO_(2) changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe,specifically developing countries.Atmospheric radiocarbon represents an important observational constraint and utilized to trace fossil fuel derived CO_(2)(CO_(2ff))in the atmosphere.For the first time,we have presented a detailed analysis on the spatial distribution of fossil fuel derived CO_(2)(CO_(2ff))over India using radiocarbon(Δ14C)measurements during three-year period.Analysis shows that theΔ14C values are varying between 29.33‰ to-34.06‰ across India in the year 2017,where highest value belongs to a location from Gujarat while lowest value belongs to a location from Chhattisgarh.Based on the14C patterns,spatial distributions of CO_(2ff) mole fractions have been determined over India and the calculated values of CO_(2ff) mole fractions are varying between 4.85 ppm to 26.59 ppm across India.It is also noticed that the highest CO_(2ff) mole fraction is observed as 26.59 ppm from a site in Chhattisgarh.CO_(2ff) mole fraction values from four high altitude sites are found to be varied between 4.85 ppm to 14.87 ppm.Effect of sampling different crop plants from the same growing season and different crop plant organs(grains,leaves,stems)on theΔ14C and CO_(2ff) have been studied.Annual and intra seasonal variations in theΔ14C and CO_(2ff) mole fractions have also been analyzed from a rural location(Dholpur,Rajasthan).展开更多
With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences,the research team led by Prof.Li Jun(李军)at the State Key Laboratory of Organic Geochemistry,Guangzhou Institut...With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences,the research team led by Prof.Li Jun(李军)at the State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,illustrated the source dynamics of carbonaceous aerosol during the haze bloom-decay process in Beijing and Guangzhou based on展开更多
A small sample of human bone from Tomb BSII of the Chalcolithic cemetery of RemedelloSotto (Brescia, Northern Italy) was processed with the AMS technique. It gave a date of 4070 ± 70BP (Beta-35224; ETH-6196) corr...A small sample of human bone from Tomb BSII of the Chalcolithic cemetery of RemedelloSotto (Brescia, Northern Italy) was processed with the AMS technique. It gave a date of 4070 ± 70BP (Beta-35224; ETH-6196) corresponding to 2711 (2609) 2512 cal BC yrs (1 sigma). Una datazione radiometrica per la Tomba BSII del cimitero Calcolitico di RemedelloSotto (Brescia). Viene presentata la datazione radiometrica eseguita con il metodo dell’acceleratore sudi un frammento di osso di calcagno del piede destro dello scheletro di inumato della Tomba BSII delsepolcreto di Remedello Sotto. L’analisi ha fornito il risultato di 4070 ± 70 BP (Beta-35224; ETH-6196)corrispondente a 2711 (2609) 2512 cal BC (1 sigma).展开更多
基金Financial support for this work was provided by Ocean University of China(841312004)National Natural Science Foundation of China(Grant Nos.41476057 and 41221004)
文摘Radiocarbon(14C) measurement of dissolved organic carbon(DOC) is a very powerful tool to study the sources, transformation and cycling of carbon in the ocean. The technique, however, remains great challenges for complete and successful oxidation of sufficient DOC with low blanks for high precision carbon isotopic ratio analysis, largely due to the overwhelming proportion of salts and low DOC concentrations in the ocean. In this paper, we report an effective UV-Oxidation method for oxidizing DOC in natural waters for radiocarbon analysis by accelerator mass spectrometry(AMS). The UV-oxidation system and method show 95%± 4% oxidation efficiency and high reproducibility for DOC in both river and seawater samples. The blanks associated with the method was also low(about 3 μg C) that is critical for 14 C analysis. As a great advantage of the method, multiple water samples can be oxidized at the same time so it reduces the sample processing time substantially compared with other UV-oxidation method currently being used in other laboratories. We have used the system and method for 14 C studies of DOC in rivers, estuaries, and oceanic environments and have received promise results.
基金This work was jointly supported by the National Natural Science Foundation of China(No.21688102 and No.11974328)the Chinese Academy of Sci-ences(XDB21020100 and XDC07010000)An-hui Initiative in Quantum Information Technologies(AHY110000).
文摘Fast and accurate quantitative detection of ^(14)CO_(2) has impor-tant applications in many elds.The optical detection method based on the sensitive cavity ring-down spectroscopy technol-ogy has great potential.But currently it has diffculties of insuffcient sensitivity and susceptibility to absorption of other isotopes/impurity molecules.We propose a stepped double-resonance spectroscopy method to excite ^(14)CO_(2) molecules to an intermediate vibrationally excited state,and use cavity ring-down spectroscopy to probe them.The two-photon process signi cantly improves the selectivity of detection.We derive the quantitative measurement capability of double-resonance absorption spectroscopy.The simulation results show that the double-resonance spectroscopy measurement is Doppler-free,thereby reducing the e ect of other molecular absorption.It is expected that this method can achieve high-selectivity detection of ^(14)CO_(2) at the sub-ppt level.
文摘Radiocarbon content in biogenic samples is widely used to study the variation of atmospheric CO<sub>2</sub> due to anthropogenic activities. A total of 20 samples of several types of tree leaves, were analyzed for this study. Sampling was carried out at the end of the rainy season in 2017 from the surrounding of the SOCOCIM cement factory in Rufisque town. Rufisque is located on the peninsula of Cape Verde, 25 km east of Dakar, where it is the 《south gate》 of the agglomeration. Reference samples of five different species were collected during the same period (2017) from a clean zone. The <sup>14</sup>C method was used for the determination of Δ<sup>14</sup>C values. The data show that the <sup>14</sup>C concentration in the studied sites was significantly lower than the clean area, due to the release of anthropogenic CO<sub>2</sub>. To estimate the Suess effect, the fossil fuel fraction was determined based on equations of mass balance for CO<sub>2</sub> concentration, stable isotopic composition of carbon, and <sup>14</sup>C concentration. The results show that selected locations are affected differently according to their distance from the factory and the wind direction.
基金supported by the National Natural Science Foundation of China(No.41401008)West Light Foundation of the Chinese Academy of Sciences(No.Y412021005)+1 种基金Natural Science Foundation of Qinghai Province(No.2016-ZJ-926Q)the instrument function development program of the Chinese Academy of Sciences(No.Y410041013)
文摘The accurately determining the lake ^14C reservoir age has a crucial significance for climatic reconstruction. In this study, the optically stimulated luminescence （OSL） dating method is employed to date samples from highstand lacustrine sediments, palaeoshoreline, fluvial terrace, and the alluvial fan of the Heihai Lake catchment. Accelerator mass spectrometry （AMS） 14C dating was also used to date fossil plants from highstand lacustrine sediments. Based on the calculations of linear regression with OSL against radiocarbon ages for same layers of two sections, the quantitative ^14C reservoir ages were estimated to lie between 3 353 and 3 464 yr during the 1.8 to 2.4 ka, which showed temporal variation. The sources of old carbon are the dissolution of carbonate bedrocks distributed along the Kunlun Mountain. The OSL ages of the different members of the hydatogen sedimentary system at Heihai Lake catchment indicate that a stronger hydrologic condition occurred from 3.0±0.2 to 1.8±0.2 ka, with a maximum lake level of 9 m higher than present. This humid stage was widely recorded in different sediments on the QTP and Chinese Loess Plateau （CLP）, indicating its broad synchronicity across the Asian Summer Monsoon region. The enhanced East Asian Summer Monsoon （EASM） and the Indian Summer Monsoon （ISM） resulted in the increase of moisture availability for the Heihai Lake area during this stage.
基金This research was supported by the National Natural Science Foundation of China(Nos.42030715,41877349)Guangdong Foundation for Program of Science and Technology Research(Nos.2017BT01Z134,2019B121205006)National Key R&D Program of China(2017YFC0212000).
文摘Air pollution and climate change are two important threats facing in our planet and are tightly linked to carbonaceous components in the atmosphere.A better understanding of the emission sources and environmental fate/sink of carbonaceous components is critical for improving our knowledge of the global carbon cycle and mitigating the negative environmental impacts of air pollution and climate change on human well-being.Radiocarbon(^(14)C),which is decayed completely in fossil fuel(e.g.coal and petroleum),is an ideal tool for quantifying the carbon flow in various carbon reservoirs.This study reviews the current knowledge of 14C in organic carbon(OC),elemental carbon(EC),individual organic compounds,methane(CH_(4)),carbon dioxide(CO_(2)),annual plants,and tree rings.The impacts of fossil and non-fossil sources on the atmosphere can be quantified by measuring^(14)C.We also report on the influence of nuclear power plants and sea-air gas exchange on the abundance of^(14)C in the atmosphere.The increasing fossil fuel emissions indicated by the depletion of^(14)CO_(2)under IPCC RCP scenarios,support the urgent need to devise ambitious strategies of reducing carbonaceous components to achieve sustainable development on Earth.This review summarizes the challenges and perspectives of 14C studies of the atmosphere.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant No. 40971056） and the Fundamental Research Funds for the Central Universities （Grant No. Lzujbky-2010-120）. We would like to thank Dr. Loukas Bardon of the University of Chicago and Dr. Yanxia Zhong of the Ningxia University for their assistance during fieldwork. We thank Dr. Saeed Doroudiani and Dr. Shiyong Yu for their critical reading and editing of the manuscript.
文摘The accurate radiocarbon dating of loess-soil sequences plays an essential role in the reconstruction of the environmental and climatic changes in continental settings during the last glaciation and Holocene. However, our knowledge about the reliability of radiocarbon ages of various fractions of soil and loess samples is still insufficient. Here, we present our study results on radio- carbon ages based on bulk organic matter, humin fraction, and carbonate of samples collected from a loess-paleosol section in the western Chinese Loess Plateau. We compare these observations with the optically stimulated luminescence ages and charcoal radiocarbon ages to evaluate the reliability of these fractions. We observed that the radio- carbon ages of humin fraction are very close to those of charcoal and are consistent with the optically stimulated luminescence ages within the experimental errors. We observed a significant deviation in the radiocarbon ages of carbonate and bulk organic matter from those of charcoal and optically stimulated luminescence ages, likely due to the dilution of these fractions during the pedogenetic process. Our results reveal that, except for charcoal, the humin fraction may yield reliable laC ages for the Chinese loess-soil sequence.
基金Supported by National Natural Science Foundation of China(11205161,41290254)
文摘To meet the measurement demands on small-mass radiocarbon （carbon content at 10.6 g level） which are becoming increasingly significant, Xi＇an-AMS has made improvements to the existing method of sample loading and has upgraded the Cs sputter ion source from the original SO-110 model. In order to study the feasibility of small-mass samples in Xi＇an-AMS and evaluate the radiocarbon sample preparation ability using existing routine systems of H2/Fe and Zn/Fe, the small-mass samples prepared by four different methods are tested. They are the mass division method, mass dilution method, H2/Fe reduction method and Zn/Fe reduction method. The results show that carbon mass above 25 μg can be prepared using the existing Zn/Fe system, but no less than 100 μg is required using the existing H2/Fe system, which can be improved. This indicates Xi＇an-AMS are now able to analyze small-mass radiocarbon samples.
文摘Examining the contribution of fossil fuel CO_(2) to the total CO_(2) changes in the atmosphere is of primary concern due to its alarming levels of fossil fuel emissions over the globe,specifically developing countries.Atmospheric radiocarbon represents an important observational constraint and utilized to trace fossil fuel derived CO_(2)(CO_(2ff))in the atmosphere.For the first time,we have presented a detailed analysis on the spatial distribution of fossil fuel derived CO_(2)(CO_(2ff))over India using radiocarbon(Δ14C)measurements during three-year period.Analysis shows that theΔ14C values are varying between 29.33‰ to-34.06‰ across India in the year 2017,where highest value belongs to a location from Gujarat while lowest value belongs to a location from Chhattisgarh.Based on the14C patterns,spatial distributions of CO_(2ff) mole fractions have been determined over India and the calculated values of CO_(2ff) mole fractions are varying between 4.85 ppm to 26.59 ppm across India.It is also noticed that the highest CO_(2ff) mole fraction is observed as 26.59 ppm from a site in Chhattisgarh.CO_(2ff) mole fraction values from four high altitude sites are found to be varied between 4.85 ppm to 14.87 ppm.Effect of sampling different crop plants from the same growing season and different crop plant organs(grains,leaves,stems)on theΔ14C and CO_(2ff) have been studied.Annual and intra seasonal variations in theΔ14C and CO_(2ff) mole fractions have also been analyzed from a rural location(Dholpur,Rajasthan).
文摘With the support by the National Natural Science Foundation of China and the Chinese Academy of Sciences,the research team led by Prof.Li Jun(李军)at the State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,illustrated the source dynamics of carbonaceous aerosol during the haze bloom-decay process in Beijing and Guangzhou based on
文摘A small sample of human bone from Tomb BSII of the Chalcolithic cemetery of RemedelloSotto (Brescia, Northern Italy) was processed with the AMS technique. It gave a date of 4070 ± 70BP (Beta-35224; ETH-6196) corresponding to 2711 (2609) 2512 cal BC yrs (1 sigma). Una datazione radiometrica per la Tomba BSII del cimitero Calcolitico di RemedelloSotto (Brescia). Viene presentata la datazione radiometrica eseguita con il metodo dell’acceleratore sudi un frammento di osso di calcagno del piede destro dello scheletro di inumato della Tomba BSII delsepolcreto di Remedello Sotto. L’analisi ha fornito il risultato di 4070 ± 70 BP (Beta-35224; ETH-6196)corrispondente a 2711 (2609) 2512 cal BC (1 sigma).
