The stable isotope ratios provide information on the presence and magnitude of important ecological processes. Many ecological processes produce characteristic isotope ratios. The stable isotope ratio value relative to known background values may indicate the presence or absence of such processes. The exact values of the iso­tope ratios make it possible to determine the magnitude of these processes, if any.

As mentioned previously, in the case of carbon isotope ratios, the climatic changes can influence the stable isotope ratios. In addition, the change of other environmental conditions can also affect the isotope ratios. Environmental changes can be studied using some substances (tree rings, hair, and ice cubes) that preserve a record of the isotope ratios for a long time.

The isotope ratios remain the same during the movement of different elements and compounds. As a result, the source of essential elements, resources, or pollutions is easily traced using isotope ratios. The isotope ratios can be very different depend­ing on geographic location. This provides a way to trace the movement or origin of a substance or component in the landscape to continental scales. The origins of envi­ronmental pollutions can be identified in this way. For example, the origin of waste deposits by paint factories can be identified using the lead isotope ratios of the raw material. Lead has four stable isotopes: 204Pb, 206Pb, 207Pb, and 208Pb. 204Pb is a primordial isotope, and the other ones are the final stable members of the radioactive decay series (as discussed in Section 4.2). Since the quantity of 204Pb isotope remains constant and the quantity of 206Pb, 207Pb, and 208Pb changes over time and depends on the uranium and thorium concentrations, the isotope composition of lead strongly depends on its origin, which can then easily be identified. As will be discussed in Section 4.3.1, the isotope ratios of lead can also be used to date rocks.

Further Reading

Choppin, G. R. and Rydberg, J. (1980). Nuclear Chemistry, Theory and Applications. Pergamon Press, Oxford.

Demeny, A. (2004). Stabilizoto’p-geoke’mia (Stable isotope geochemistry). Magyar Kemiai Folyoirat 109-110:192-198.

Friedlander, G., Kennedy, J. W., Macias, E. S. and Miller, J. M. (1981). Nuclear and Radiochemistry. John Wiley and Sons, New York, NY.

Ghosh, P., Adkins, J., Affek, H., Balta, B., Guo, W., Schauble, E. A., et al. (2006). 13C-18O bonds in carbonate minerals: a new kind of paleothermometer. Geochim. Cosmochim. Acta 70:1439-1456.

Haissinsky, M. (1964). Nuclear Chemistry and its Applications. Addison-Wesley Publishing Company, Inc., Reading, MA.

University of Wyoming, USA. <http://www. uwyo. edu/sif/stable-isotopes/index. html.> (accessed 24.03.12.)

Lieser, K. H. (1997). Nuclear and Radiochemistry. Wiley-VCH, Berlin.

McKay, H. A.C. (1971). Principles of Radiochemistry. Butterworths, London.