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  • 1
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    A study on14C measurements of the forest soils in Dinghushan Biosphere Reserve (1998)
    Springer
    Details
    Publication Date: 1998-08-01
    Print ISSN: 1001-6538
    Electronic ISSN: 1861-9541
    Topics: Natural Sciences in General
    Published by Springer
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  • 2
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    Buried Ancient Forest and Implications for Paleoclimate Since the Mid-Holocene in South China (2010)
    Cambridge University Press
    Details
    Publication Date: 2010-01-01
    Description: The historical evolution of an ancient forest that developed at Gaoyao, south China, can be divided into 4 stages of radiocarbon intervals (1.1–1.5, 2.0–3.5, 3.6–4.0, and 4.3–4.9 ka) in which the last 3 stages all developed in a wetland and formed humic layers of 2.0, 0.5, and 0.7 m depth, respectively. The humic layers were interrupted by 2 white-gray silty clay layers that most likely formed during climate fluctuations. Four drought events were identified during the evolution of the ancient forest, occurring around 4.3, 3.6, 2.0, and 1.1 ka, respectively, with durations of ∼1000 14C yr. These events are consistent with other records both in low- and high-latitude areas, in particular with the little ice ages occurring since the mid-Holocene. Precipitation likely increased from 5.0 to 3.6 ka in south China, then decreased, which is probably the main cause for the development as well as the demise of the ancient forest.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 3
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    Improved Application of Bomb Carbon in Teeth for Forensic Investigation (2010)
    Cambridge University Press
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    Publication Date: 2010-01-01
    Description: While radiocarbon is widely applied in dating ancient samples, recent studies reveal that 14C concentrations in modern samples can also yield precise ages due to the atmospheric testing of thermonuclear devices between 1950 and 1963. 14C concentrations in both enamel and organic matter of 13 teeth from 2 areas in China were examined to evaluate and improve this method of forensic investigation. Choosing enamel near the cervix of the tooth can reduce the error caused by the difference between the sample formation time and whole enamel formation time because tooth enamel formations take a long time to complete. A proper regional data set will be helpful to get an accurate result when calculating the age of the sample (T1) by the CALIBomb program. By subtracting the enamel formation time (t), the birth date of an individual (T2) can be confirmed by enamel F14C from 2 teeth formed at different ages. Calculated enamel formation dates by 14C concentration are basically consistent with corresponding actual values, with a mean error of 1.9 yr for all results and 0.2 yr for the samples formed after AD 1960. This method is more effective for dating samples completed after AD 1960. We also found that 14C concentrations in organic matter of tooth roots are much lower than atmospheric concentrations in root formation years, suggesting that the organic material keeps turning over even after tooth formation is complete. This might be a potential tool for identification of death age to extract a proper component for 14C dating. We also observed that δ13C values between hydroxyapatite and organic matter indicate that isotopic fractionation during the biomineralization is 8–9%‰ more positive in mineral fractions than in organic matter.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 4
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    Small-mass graphite preparation for AMS 14C measurements performed at GIGCAS, China (2017)
    Cambridge University Press
    Details
    Publication Date: 2017-05-08
    Description: The sealed tube Zn reduction method has been applied for small-mass samples ranging from 15 to 100 μg carbon preparation for accelerator mass spectrometry (AMS) radiocarbon (14C) measurements at the AMS-14C Preparation Lab in Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS). The volume of the sealed reactor tube is reduced to ~0.75 cm3 in order to increase the yield of graphite. Graphite targets are measured at the Keck Carbon Cycle AMS Facility at the University of California, Irvine (KCCAMS). The targets generate a maximum 12C+1 current of about 0.5 μA per 1 μg C. The modern-carbon background is estimated to be 0.25–0.60 μg C, and dead-carbon background to be ~0.3–0.9 μg C. Both modern-carbon background and dead-carbon background are size dependent, so the results can be corrected. The precision of the small-mass modern carbon standard samples is±15–25‰ for the size of ~15–20 μg C,±5–10‰ for ~20–50 μg C, and±3–10‰ for 50–100 μg C. Further reduction of dead-carbon and modern-carbon contamination is needed in preparation of small-mass samples at GIGCAS.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 5
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    Fossil-Fuel-Derived CO2 Contribution to the Urban Atmosphere in Guangzhou, South China, Estimated by 14CO2 Observation, 2010–2011 (2013)
    Cambridge University Press
    Details
    Publication Date: 2013-01-01
    Description: From October 2010 to November 2011, the urban atmospheric CO2 concentration in Guangzhou ranged from 550 to 460 ppm, with mean monthly concentration fluctuating between 530 and 470 ppm. A lower concentration was observed in summer and autumn, while a higher concentration occurred in spring and winter. The urban atmospheric CO2 δ13C value varied between −9.00 and −13.10%, with mean monthly value fluctuating between −9.60 and −11.80%. There was no significant relationship between the CO2 concentration and δ13C value, reflecting the influence from the fossil-fuel-derived CO2 on the urban atmospheric CO2. The urban atmospheric CO2 Δ14C value fluctuated dramatically from 29.1 ± 2.5% to −85.2 ± 3. 1%, with a mean annual value of −16.4 ± 3.0%. A similar seasonal variation of Δ14C value with the concentrations was observed: the higher Δ14C values mainly appeared in summer and autumn (July to September), with a mean value of about −5.2 ± 2.9%, while lower Δ14C values occurred in spring and winter (December to April), about −27.1 ± 3.2% average. Based on the atmospheric Δ14C values, the calculated fossil-fuel-derived CO2 concentrations range between 1 and 58 ppm, with the mean annual concentration around 24 ppm. Similarly, a lower fossil-fuel-derived CO2 concentration appeared in summer and autumn (July to September) with a mean value of ∼17 ppm, while the higher fossil-fuel-derived CO2 concentration occurred in spring and winter (December to April) with an average value of ∼29 ppm. A comparison of the CO2 concentrations before and after the Guangzhou Asian Games (in November 2010) and the Spring Festival of 2011 confirmed that human activities can greatly decrease the fossil-fuel-derived CO2 emissions to the urban atmosphere in Guangzhou.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 6
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    14C and 10Be in Dust Deposited During the Storm of 16–17 April 2006 in Beijing (2013)
    Cambridge University Press
    Details
    Publication Date: 2013-01-01
    Description: The concentrations of 10Be and 14C and values of δ13C in samples collected during a major dust storm in Beijing on 16–17 April 2006 were studied. The 10Be concentrations ranged from 1.69 × 108 to 2.07 × 108 atom/g, 14C ages for black carbon (BC) ranged from 3001 to 5181 yr BP and for total inorganic carbon (TIC) from 8464 to 9119 yr BP, and δ13C values for BC ranged from -23.15% to -23.80% and for TIC from -5.39% to -5.98%. A comparison of BC content and δ13C value between the dust, surface soil in the dust source region, and aerosols in Beijing indicated that BC in the dust deposited in Beijing is significantly incorporated by aerosol BC during the dust transportation. Based on the 14C ages of BC, the proportion of fossil-fuel-derived BC was 0.35–0.49 of the total. In contrast to BC, the TIC deposited in Beijing can be firmly related to the source area and δ13C was not significantly modified during its transportation. According to the 14C ages of TIC, the proportion of the secondary carbonate in the dust was from 0.63 to 0.70. The results confirm that 14C of TIC is another useful tracer to indicate the source region of dust besides the content and δ13C value of TIC from the arid and semi-arid regions of China.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 7
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    Turnover Rate of Soil Organic Matter and Origin of Soil 14Co2 in Deep Soil from a Subtropical Forest in Dinghushan Biosphere Reserve, South China (2010)
    Cambridge University Press
    Details
    Publication Date: 2010-01-01
    Description: This paper examines the carbon isotopes (13C, 14C) of soil organic carbon (SOC) and soil CO2 from an evergreen broadleaf forest in southern China during the rainy season. The distribution of SOC δ13C, and SOC content with depth, exhibits a regular decomposition of SOC compartments with different turnover rates. Labile carbon is the main component in the topsoil (0–12 cm) and has a turnover rate between 0.1 and 0.01 yr–1. In the middle section (12–35 cm), SOC was mainly comprised of mediate carbon with turnover rates ranging between 0.01 and 0.025. Below 35 cm depth (underlayer section), the SOC turnover rate is slower than 0.001 yr–1, indicating that passive carbon is the main component of SOC in this section. The total production of humus-derived CO2 is 123.84 g C m–2 yr–1, from which 88% originated in the topsoil. The middle and underlayer sections contribute only 10% and 2% to the total humus-derived CO2 production, respectively. Soil CO2 δ13C varies from –24.7‰ to –24.0‰, showing a slight isotopic depth gradient. Similar to soil CO2 δ13C, Δ14C values, which range from 100.0‰ to 107.2‰, are obviously higher than that of atmospheric CO2 (60–70‰) and SOC in the middle and underlayer section, suggesting that soil CO2 in the profile most likely originates mainly from SOC decomposition in the topsoil. A model of soil CO2 Δ14C indicates that the humus-derived CO2 from the topsoil contributes about 65–78% to soil CO2 in each soil gas sampling layer. In addition, the humus-derived CO2 contributes ∼81% on average to total soil CO2 in the profile, in good agreement with the field observation. The distribution and origin of soil 14CO2 imply that soil CO2 will be an important source of atmospheric 14CO2 well into the future.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 8
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    Interannual 14C Variations During 1977–1998 Recorded in Coral from Daya Bay, South China Sea (2004)
    Cambridge University Press
    Details
    Publication Date: 2004-01-01
    Description: Twenty-two annually banded samples of coral from 1977 to 1998 were collected from Daya Bay, South China Sea, and bomb 14C concentrations were determined. The interannual variation of coral Δ14C is controlled mainly by oceanic factors. In ENSO years, the coastwise upwelling current of the South China Sea has been intensified; hence, the coral Δ14C displays its minimum value. The interannual variation curve of Δ14C in coral bears a relationship with the Southern Oscillation Index (SOI) curves: the correlation coefficient between Δ14C and (SOI)w is 0.43 and the correlation coefficient between Δ14C and (SOI)y is 0.27. The coral Δ14C has no remarkable response to the variation of solar radiation energy. In the past 20 yr or so, the general situation and oceanic thermal structure of the South China Sea are still stable even though interannual variations in atmosphere-sea interaction and upwelling current driven by the tropical energy have occurred.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 9
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    14C and 10Be in Dust Deposited During the Storm of 16–17 April 2006 in Beijing (2013)
    Cambridge University Press
    Details
    Publication Date: 2013-01-01
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 10
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    Quantification of Sedimentary Organic Carbon Storage and Turnover of Tidal Mangrove Stands in Southern China Based on Carbon Isotopic Measurements (2013)
    Cambridge University Press
    Details
    Publication Date: 2013-01-01
    Description: Mangrove ecosystems are highly productive and play an important role in tropical and global coastal carbon (C) budgets. However, sedimentary organic carbon (SOC) storage and turnover in mangrove forests are still poorly understood. Based on C isotopic measurements of sediment cores of 2 mangrove stands in southern China, SOC density was 431.77 Mg ha−1 at site 1 (a Aegiceras corniculatum-dominated high tidal stand) and 243.65 Mg ha−1 in site 2 (a Bruguiera gymnorrhiza + Kandelia candel-dominated middle tidal stand). SOC δ13C values at both mangrove sites ranged from -29.4% to −26.0%. SOC δ13C was enriched with depth at 20–50 cm at site 1, which possibly resulted from preferential microbial decomposition. SOC δ13C at site 2 experienced frequent tidal flushing, and presented relatively stable values with depth. A bomb-14C-based SOC turnover model indicated that turnover times of SOC at 20–50 cm at site 1 were 4.44–26.04 yr. Modern C input from abundant roots might account for the very short SOC turnover times at these subsurface layers. As a result, our study suggested that tidal processes had a great influence on SOC storage and turnover in mangrove forests.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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