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Using 14C as a Tracer of Carbon Accumulation and Turnover in Soils

Published online by Cambridge University Press:  18 July 2016

G. M. Milton  and
S. J. Kramer
G. M. Milton
Affiliation:
Environmental Research Branch, AECL Chalk River Laboratories, Chalk River Ontario, Canada, K0J 1J0
S. J. Kramer
Affiliation:
Environmental Research Branch, AECL Chalk River Laboratories, Chalk River Ontario, Canada, K0J 1J0
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Abstract

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Three very different Canadian soils—clay soils of the St. Lawrence Lowlands, sandy forest soils of the Ottawa Valley, and organic-rich sediments from a wetland on the Canadian Shield—have been cored, sliced and separated into different density fractions, and the radiocarbon content of these soil fractions measured. In two of the areas sampled, cores were obtained close to operating nuclear reactors, as well as from beyond their region of influence. As a consequence, it has been possible to ascertain the depths of penetration of both the weapons-testing pulse (peaking in 1963), and a 25–50-yr chronic reactor input of 14C.

The percentage of carbon stored in different density fractions varied with soil type. Turnover times for bulk soil organic carbon, estimated from soil degassing rates, have been compared with those predicated on the residual “bomb” 14C in background cores, and/or on the ratio of reactor-emitted 14C retained in the soils to the total deposited during the lifetime of operation. Residence times for the heavy carbon fraction present at depths below the influence of anthropogenic inputs have also been estimated.

The accumulated data will be incorporated in a revised soil model, adjusted for the parameters deemed to be most important to carbon turnover rates under Canadian conditions.

Type
Part 2: Applications
Information
Radiocarbon , Volume 40 , Issue 2: 16th International Radiocarbon Conference June 16-20, 1997 Part 2: Applications, Conference Editors: Willem G. Mook Johannes van der Plicht , 1997 , pp. 999 - 1011
Copyright
Copyright © The American Journal of Science 

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