Radiocarbon cycles

Throughout this chapter many of the arguments are based on an assumption of steady state. Before the agricultural and industrial revolutions, the carbon cycle presumably was in a quasi-balanced state. Natural variations still occur in this unperturbed environment the Little Ice Age, 300-400 years ago, may have influenced the carbon cycle. The production rate of varies on time scales of decades and centuries (Stuiver and Quay, 1980,1981), implying that the pre-industrial radiocarbon distribution may not have been in steady state. 

Berner, W., Oeschger, H. and Stauffer, B. (1980). Information on the CO2 cycle from ice core studies. Radiocarbon 22,227-235. 

The carbon dioxide molecules including a radiocarbon atom are chemically undistinguishable from those of ordinary carbon dioxide, with which it mixes, and eventually, carbon dioxide, including a radiocarbon atom, is homogeneously distributed throughout the earth s atmosphere and hydrosphere. Thus there is a state of constant production, distribution, and decay of radiocarbon, which results in the relative amount of radiocarbon in the atmosphere and hydrosphere remaining constant. In this homogeneously distributed condition, radiocarbon enters the carbon cycle - as the... 

Carbon Dioxide. Carbon dioxide, also a colorless and odorless gas, makes up about 0.03% of dry air. Carbon dioxide is introduced into the atmosphere by several natural processes it is released from volcanoes, from burning organic matter, and from living animals as a byproduct of the respiration process. It is for this latter reason that carbon dioxide plays a vital role in the carbon cycle (see Fig. 62), which makes possible one of the more important scientific tools in archaeology, radiocarbon dating (see Textbox 52). 

The chemistry of carbon, and radiocarbon, in the atmosphere represents one of the most important areas of environmental research today. The primary practical reason for this is the increasing attention which must be paid to the critical balance between energy and the environment, especially from the viewpoint of man s perturbations of natural processes and his need to maintain control. Probably more than other species, carbonaceous molecules play a central role in this balance. Some of the deleterious effects of carbonaceous gases and particles in the atmosphere are set down in Table 3. The potential effects of increased local or global concentrations of these species on health and climate have led to renewed interest in the carbon cycle and the "C02 Problem". It should be evident from the table, however, that carbon dioxide is not the only problem. In fact, the so-called "trace gases and particles" in the atmosphere present an important challenge to our interpretation of the climatic effects of carbon dioxide, itself [20]. 

Radiocarbon (14C) is produced in the atmosphere by the cosmic ray neutron flux interacting with 14N[14N(n,p)14C], The 14C hot1 atom then equilibrates with atmospheric C02 which participates in the C-0 cycle and passes into the food chain (biosphere). Most of the radiocarbon is taken up by the oceans which constitute the largest reservoir of C02 within the secondary geochemical cycle. 

Burchuladze, A. A., Pagava, S. V., Povinect, P., Togonidze, G. I., Usacevt, S., Radiocarbon variations with the 11-year solar cycle durinq the last century. Nature, 287, 320-322 (1980). 

Guilderson, T.P., K. Caldeira, and P.B. Duffy. 2000. Radiocarbon as a diagnostic tracer in ocean and carbon cycle modeling. Global Biogeochemical Cycles 14(3) 887-902. 

Key, R.M., and S. Rubin. 2002. Separating natural and bomb-produced radiocarbon in the ocean The potential alkalinity method. Global Biogeochemical Cycles. 

Levin, I., and V. Hesshaimer. 2000. Radiocarbon—A unique tracer of global carbon cycle dynamics. Radiocarbon 42 69-80. 

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