Low-Temperature and Temperature Stepped-Combustion of Terrace Sediments from Nanfu, Taiwan

We discuss a radiocarbon study of sediment samples collected from Nanfu terrace in western Taiwan. From these, we extracted humic acids (HA) and humin from the very fine and coarse grain-size fractions using a standard acid-alkali-acid pretreatment. The humin extracts were combusted at 400 and 1100 °C by stepped-combustion, to yield a low-temperature (LT) carbon component and a high-temperature (HT) carbon component. We compare the ages of the LT and HT humin fractions to the HA fractions, in samples collected at 2 depths within the Nanfu terrace. As in previous stepped-combustion studies on sediments, we find that the HA ages are the youngest on average, and overlap the LT ages, and that the carbon contained in the HT fraction is always distinctly older than the LT and HA ages. To better understand the relationship between 14C age and combustion temperature, we conducted an incremental stepped-combustion experiment with one of the samples (1E) using 50 °C steps that ranged from 300 to 1100 °C. The 14C results of the stepped-combustion products show a clear division between 2 isotopically identifiable carbon constituents, from carbon released below 400 °C and carbon released above 550 °C. By comparing the δ13C and 14C results, we find evidence for a third carbon isotopic component in the humin that is released when combusted at ∼500 °C.

[1]  D. Froese,et al.  Low temperature (LT) combustion of sediments does not necessarily provide accurate radiocarbon ages for site chronology , 2010 .

[2]  D. Froese,et al.  Low Temperature (LT) combustion of sediments does not provide accurate radiocarbon dates for site chronology , 2010 .

[3]  Yue‐Gau Chen,et al.  Touhuanping Fault, an active wrench fault within fold-and-thrust belt in northwestern Taiwan, documented by spatial analysis of fluvial terraces , 2009 .

[4]  J. H. Mayer,et al.  Comparisons and Interpretations of Charcoal and Organic Matter Radiocarbon Ages from Buried Soils in North-Central Colorado, USA , 2008, Radiocarbon.

[5]  P. Sollins,et al.  Organic C and N stabilization in a forest soil: Evidence from sequential density fractionation , 2006 .

[6]  I. Schöning,et al.  Chemical composition of young and old carbon pools throughout Cambisol and Luvisol profiles under forests , 2006 .

[7]  G. Sposito,et al.  Molecular structure in soil humic substances: the new view. , 2005, Environmental science & technology.

[8]  K. Sieh,et al.  Neotectonic architecture of Taiwan and its implications for future large earthquakes , 2005 .

[9]  I. Schöning,et al.  O/N-alkyl and alkyl C are stabilised in fine particle size fractions of forest soils , 2005 .

[10]  P. Reimer,et al.  CALIB 5.0.2 [WWW program and documentation] , 2005 .

[11]  K. Uto,et al.  14C dating of soil samples from the Unzen volcano scientific drilling boreholes , 2004 .

[12]  K. Paustian,et al.  Stabilization mechanisms of soil organic matter: Implications for C-saturation of soils , 2002, Plant and Soil.

[13]  C. Chenu,et al.  The dynamics of carbon in particle-size fractions of soil in a forest-cultivation sequence , 1998, Plant and Soil.

[14]  G. Burr,et al.  Stepped-Combustion 14C Dating of Bomb Carbon in Lake Sediment , 2004, Radiocarbon.

[15]  M. Kleber,et al.  Stabilisation of soil organic matter by interactions with minerals as revealed by mineral dissolution and oxidative degradation , 2003 .

[16]  J. van der Plicht,et al.  Mean residence time of soil organic matter associated with kaolinite and smectite , 2003 .

[17]  J. Southon,et al.  Stepped-Combustion 14C Dating of Sediment: A Comparison with Established Techniques , 2001, Radiocarbon.

[18]  Weijian Zhou,et al.  Evaluation of NaOH leaching techniques to extract humic acids from palaeosols , 2000 .

[19]  Shui-Beih Yu,et al.  Velocity field of GPS stations in the Taiwan area , 1997 .

[20]  P. Vitousek,et al.  Mineral control of soil organic carbon storage and turnover , 1997, Nature.

[21]  Yue‐Gau Chen,et al.  Sea Level Changes in the Last Several Thousand Years, Penghu Islands, Taiwan Strait , 1996, Quaternary Research.

[22]  R. Amundson,et al.  Rapid Exchange Between Soil Carbon and Atmospheric Carbon Dioxide Driven by Temperature Change , 1996, Science.

[23]  Charles W. Martin,et al.  Variation in Radiocarbon Ages of Soil Organic Matter Fractions from Late Quaternary Buried Soils , 1995, Quaternary Research.

[24]  P. Liew,et al.  A 5000-Year Pollen Record from Chitsai Lake, Central Taiwan , 1994 .

[25]  D. Brockmeier,et al.  Mean residence time. , 1986, Methods and findings in experimental and clinical pharmacology.

[26]  D. Anderson,et al.  Organo-Mineral Complexes and Their Study by Radiocarbon Dating1 , 1984 .