Contribution of the “Great Carbon Tracker” in the Dilution of Atmospheric Radiocarbon Emissions

Contribution of the “Great Carbon Tracker” in the Dilution of Atmospheric Radiocarbon Emissions

Sergey Olegovich Travin (Federal Research Center for Chemical Physics After N. N. Semenov of the Russian Academy of Sciences, Russia) and Oleg Borisovich Gromov (High-Tech Research Institute of Inorganic Materials Named After Academician A. A. Bochvar, Russia)
DOI: 10.4018/978-1-7998-1241-8.ch006

Abstract

The general model of global carbon circulation (in particular 14C) have been known for half a century and includes both natural and anthropogenic sources and sinks. The main problem was the lack of information about rates of migration from one form to another. The authors made fitting of model data concerning both 12C and 14C dynamics in atmosphere and in sea water. The 70-times discrepancy between generation and decay rates for radiocarbon was explained. The main channel of 14C disappearance is not decay but dissolution in sea waters. By this reason, they deny the Suesse hypothesis because atmospheric carbon dioxide is diluted not by 14C-free substance (after burning of fossil fuels) but from the source of oceans. Multiple numeric experiments modeling 14C pulse or permanent input to the environment had demonstrated the exclusive stability of natural system. It obeys homeostatic principle and resists any attempts to shift steady state concentration. So, all speculations about extraordinary threat from technogenic 14C from nuclear industry do not have any scientific base.
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Introduction

Recent years, increasing public attention is drawn to the discussion of various aspects of the emergence, transformation and migration of radioactive isotope 14C (hereinafter, radiocarbon). To some extent this is due to really existing risk of receiving high doses of radiation as a result of anthropogenic emissions of this radionuclide. Much more “popularity” of radiocarbon is connected with its fame, as a basic element used in the dating of historical artifacts by Libby method. In this paper we will be interested in primarily quantitative picture of the sensitivity of the atmosphere and biosphere of the Earth to additional emissions of 14C.

The model of global circulation of carbon-14 have been known for over half a century and includes both natural and anthropogenic sources and sinks. Along with the generation of 14C from atmospheric nitrogen by cosmic radiation and radiation arising from nuclear testing one should take into account also flow to the atmosphere from the emissions and discharges of the nuclear fuel cycle plants. Currently, the main source of the anthropogenic radiocarbon are not the nuclear power plants themselves (as it is sometimes presented by the media), but factories for the regeneration of spent fuel rods.

Carbon-14 exists in the atmosphere mainly in the form of 14СО2 and partly in the form of 14СО, which is then oxidized with the characteristic time 978-1-7998-1241-8.ch006.m01 (Arslanov, 1987).

It is believed that the modern nuclear industry gives wastes in the atmosphere from 0.01 to 1 TBq of 14C per day (Bolin, 1972). Even for the upper limit the ratio of anthropogenic radiocarbon does not exceed 25% of its natural production and cannot play important role in the radiological impact on the Biosphere.

In addition, over the last 50 years, at the same 25% increase in the quasi-equilibrium CO2 (stable isotope) in the atmosphere (Fig. 1). This leads to the so-called Suesse effect: the burning of fossil fuels containing no radiocarbon, lowers its relative content in the atmosphere. Really, the dilution of the “modern” carbon dioxide with “ancient” one, in which 14C had existed hundreds of half-lives without exchange with the atmosphere and completely disintegrated. The content of CO2 in the atmosphere has increased dramatically over the past decade and now stands about 400 ppm.

Figure 1.

The long-term increasing trend for concentration of atmospheric carbon dioxide over the whole observation period in the Observatory of Mauna Loa (USA) from March 1957 to July 2015 (Dr. Pieter Tans, 1915) – pale line. Dark line – our kinetic modeling

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To estimate the dynamic characteristics of transfer processes in the carbon cycle of the planet, one must notice the high-frequency oscillations superimposed on the growing trend.

Figure 2.

Annual variations in the concentration of carbon dioxide in the atmosphere

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Figure 2 shows the model curve approximation of the annual fluctuations in the concentration of atmospheric carbon dioxide. The maximum rate of recession, i.e. CO2 consumption by plants and oceanic plankton occurs in June-July, while the maximal excess of industrial emission upon biogenic) consumption correspond to the peak of heating season (in the Northern hemisphere, where than 90% of the population is located), i.e. in December-January.

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