Oxygen isotope uses:

Oxygen Isotopes

In order to understand the different uses of Oxygn isotopes one first needs to know what an isotope is and be able to differentiate between stable and radioactive isotopes. Oxygen as an isotope is widely used within the scientific community to accomplish a number of things some of which will be explored in this blog.

What is an isotope:

An isotope is a variation of an element which either has more or less neutrons than the most abundant form of that particular element in question. This variation in the number of neutrons within the elements nucleus increases or decreases the atomic mass of the element and allow for the element to have different chemical reaction rates even though all the different elemental isotopes will have the same chemical reaction principles. There are however, two different types of isotopes namely stable and unstable isotopes. Radioactive and stable isotopes are not very different in the sense that they all contain differing numbers of neutrons however radioactive isotopes have excess nuclear energy which allows them to radioactively decay and give off that excess energy with it known that radioactive decay is responsible for the earths internal heat budget, while stable isotopes do not have excess nuclear energy and do not radioactively decay. Just as every element has an isotope each element has both stable and radioactive isotopes which is important to known since they each have different applications.

Oxygen Isotope Earth Science uses:

Oxygen has three known stable isotopes: 16-oxygen, 17-oxygen and 18-oxygen, and a number of Radioactive isotopes. The main use of oxygen isotopes specifically the ratio between 16-oxygen and 18O is in paleoclimate reconstruction studies. An example of such paleoclimate reconstruction is using the stable isotope composition of marine calcite which looks at the 18-oxygen signature of shell marine life to determine the seawater temperature which has been done by Tindal .Tindal in a study found that the use of 18-oxygen composition within shell marine life is useful as the marine life incorporates the 18-oxygen signature of the seawater with the fractionation of which is temperature dependent allowing us to reconstruct the temperature at which these marine creatures lived and therefore the temperature of the sea body. 18-oxygen is used to determine the water temperature because 16-oxygen is more readily evaporated than 18-oxygen, this relation is also important as it allows for the origin of precipitation to be found. This reaction rate differential between 16-oxygen and 18-oxygen is important in paleoclimate reconstruction studies as the lighter oxygen isotope will have a higher concentration within glaciers and terrestrial waterbodies compared to oceans which would have greater concentrations of 18-oxygen.

Oxygen isotopes are extensively used within the field of petrology because of the important role which hydrothermal fluids play in magmatic processes and metamorphic processes. Most studies that use Oxygen isotopes look at the interaction between hydrous and anhydrous minerals within whole rocks. Schiffman used 18-oxygen isotope analysis of hydrothermal zonation within the northern Troodos complex to indicate that the rock complex was formed in the upper Cretaceous within a seawater hydrothermal system. Schiffman found out that the complex is rich in subgreenschist facies mineral assemblages that contain high ratios of 18-oxygen isotopes which is indicative of rocks formed within areas where seawater diffuse recharge is an important component of rock formation.

Other uses of Oxygen Isotope:

Most Earth Science studies use the stable isotopes of oxygen within their studies to get to whatever answer they desire to however Earth Scientist are not the only users of isotopes, medical researchers like Ter-pogossian have previously used 15-oxgen to study the cerebral blood flow, blood volume, and oxygen metabolism because of the short half-life of 15-oxygen, which is 2 minutes. The use of radioactive 15-oxygen within the medical world has also been used to determine the functionality of the human respiratory system with a study by Dyson used 15-oxygen to determine the regional lung function within humans. These are two of many examples of the application of radioactive oxygen isotopes outside of the Earth sciences.

Overall the use of Oxygen isotopes goes beyond just paleoclimate reconstruction with this blog giving a number of different applications both within and outside the Earth Science stream for the different applications of both stable and radioactive oxygen isotopes. However, there are a lot more applications out there which this blog has not looked into but hopes that an interest within the topic has been ignited within my readers.

Reference List:

 Schiffman, P. and Smith, B.M., 1988. Petrology and oxygen isotope geochemistry of a fossil seawater hydrothermal system within the Solea graben, northern Troodos ophiolite, Cyprus. Journal of Geophysical Research: Solid Earth, 93(B5), pp.4612-4624.

 Tindall, J., Flecker, R., Valdes, P., Schmidt, D.N., Markwick, P. and Harris, J., 2010. Modelling the oxygen isotope distribution of ancient seawater using a coupled ocean–atmosphere GCM: implications for reconstructing early Eocene climate. Earth and Planetary Science Letters, 292(3-4), pp.265-273.

 Ter-Pogossian, M.M. and Herscovitch, P., 1985, October. Radioactive oxygen-15 in the study of cerebral blood flow, blood volume, and oxygen metabolism. In Seminars in nuclear medicine (Vol. 15, No. 4, pp. 377-394). WB Saunders.

 Dyson, N.A., Hugh-Jones, P., Newbery, G.R., Sinclair, J.D. and West, J.B., 1960. Studies of regional lung function using radioactive oxygen. British medical journal, 1(5168), p.231.