Radiocarbon, Volume 49 (2007)
http://hdl.handle.net/10150/635076
2024-03-27T13:33:46ZFrom the Editor
http://hdl.handle.net/10150/655160
From the Editor
Jull, A. J. Timothy
2007-01-01T00:00:00ZValidating and Improving Archaeological Phasing at St. Mary Spital, London
http://hdl.handle.net/10150/654084
Validating and Improving Archaeological Phasing at St. Mary Spital, London
Sidell, Jane; Thomas, Christopher; Baylis, Alex
This paper outlines the radiocarbon program applied to the excavation and skeletal assemblage from the cemetery of the medieval Priory and Hospital of St. Mary Spital in London. Problems encountered in dating medieval cemeteries are outlined. The problems were addressed through the application of Bayesian modeling to validate and refine conventional approaches to constructing phases of archaeological activity. It should be noted that this project was solely funded by the developer of the land; such projects rarely undertake even modest programs of 14C dating. We aim to show how the investment of a proportionally small sum, compared to the overall project costs, may reap significant benefits.
From the 19th International Radiocarbon Conference held in Keble College, Oxford, England, April 3-7, 2006.
2007-01-01T00:00:00ZUsing a Soil Chronosequence to Identify Soil Fractions for Understanding and Modeling Soil Carbon Dynamics in New Zealand
http://hdl.handle.net/10150/654083
Using a Soil Chronosequence to Identify Soil Fractions for Understanding and Modeling Soil Carbon Dynamics in New Zealand
Prior, Christine A.; Baisden, W. Troy; Bruhn, Frank; Neff, Jason C.
We are developing practical methodologies to characterize pool sizes and residence times for fractions of soil organic matter (SOM) using radiocarbon, with a particular focus on SOM in New Zealand pasture soils that responds to global change on decadal timescales. As single mean residence times for the entire SOM pool can be misleading or uninterpretable, we focus on the use of samples collected about 7 and 40 yr after the bomb-14C spike to separate SOM into at least 2 pools. These results from a box model methodology yield sensible estimates of the proportion of passive SOM, and the residence time of the dominant pool with approximately decadal residence times. These results are supported by chemical analysis. Approximately 45-yr residence times of light-fraction SOM in a relatively infertile soil contrast with ~16-yr residence times in a more fertile soil, and correspond to large differences in the proportion of lignin- and polysaccharide-derived SOM in these soils measured using pyrolysis-GC/MS. To achieve greater detail and assess the degree to which active SOM with annual turnover rates may bias results from the simple model, we use density as a means of isolating SOM with different degrees of mineral association. Initial results from grazed pasture soils sampled in 20034 emphasize that isolating non-mineral-associated light fractions can improve understanding, but may be less important than identifying fractions associated with unique mineralogy. In this soil, a fraction with density =2.55 g/mL shows much larger proportions of passive SOM than other fractions.
From the 19th International Radiocarbon Conference held in Keble College, Oxford, England, April 3-7, 2006.
2007-01-01T00:00:00ZTwo Decades of Regular Observations of 14CO2 and 13CO2 Content in Atmospheric Carbon Dioxide in Central Europe: Long-Term Changes of Regional Anthropogenic Fossil CO2 Emissions
http://hdl.handle.net/10150/654044
Two Decades of Regular Observations of 14CO2 and 13CO2 Content in Atmospheric Carbon Dioxide in Central Europe: Long-Term Changes of Regional Anthropogenic Fossil CO2 Emissions
Kuc, T.; Rozanski, K.; Zimnoch, M.; Necki, J.; Chmura, L.; Jelen, D.
Time series are presented of radiocarbon and 13C contents in atmospheric carbon dioxide over eastern Europe (southern Poland), covering the periods 19831994 and 20002004. The carbon isotope composition was measured in biweekly composite samples of atmospheric CO2, collected about 20 m above the local ground level. The data for 2 observational sites are presented: i) city of Krakw (50 degrees 04'N, 19 degrees 55'E; 220 m asl; for 1983-1994 and 2000-2004); and ii) Kasprowy Wierch, Tatra Mountains (49 degrees 14'N, 19 degrees 56'E; 1989 m asl; for 2000-2004). The latter site is considered a regional reference station, relatively free of anthropogenic influences. During the period 1983-1994, observations in the Krakw area revealed a gradual decrease of 14C content with a broad minimum around 1991 and a small increase by about 10 in the subsequent years. d13C also changes with time, showing a decreasing trend from approximately 9.6 in 1983, with a slope of 0.02/yr. The observed trends for both isotopes coincide well with a substantial reduction of coal consumption in Poland and partial replacement of coal by natural gas, especially in urban regions. After 2000, the d13C slightly increases, reaching a mean value of 10 in 2004, while delta-14C is below the reference level by ~3.5. Observations at Kasprowy Wierch (regional reference station) also reflect a diminishing input of fossil carbon into the regional atmosphere. The fossil component in atmospheric CO2, calculated with the aid of 14C data available for the 2 study periods, shows a reduction of anthropogenic input by a factor of 2, which is confirmed by annual statistics of coal consumption.
From the 19th International Radiocarbon Conference held in Keble College, Oxford, England, April 3-7, 2006.
2007-01-01T00:00:00Z