A Survey of the Occurence of Oxygen 18 in Natural Sources

Abstract

An investigation of the concentration of the heavy isotope of oxygen, O18, in various samples of water was carried out. Natural variations as high as 2.9% were found - glacier water being 2.3% light and Dead Sea water 2.0% heavy, as compared to Lake Ontario water as standard. Other values - water from tank oxygen + 2.9%, atmospheric water vapor -0.9%, Atlantic Ocean water +0.4%, Pacific Ocean water - 0.8% , and atmospheric carbon dioxide - 0.5%. The water samples were equilibrated with tank carbon dioxide, which was then analyzed using the mass spectrometer. Some work was also done on photosynthesis. The free water, water of crystallization, and tissue oxygen (as water) , in a normal leaf which had bean photosynthesizing for 8 hours, were analyzed by equilibration with carbon dioxide as above. It was found that all of these were more enriched in oxygen 18 than the water with which they were fed . The free water averaged about 1.3% heavy, water of crystallization as high as 8.7% heavy, and tissue oxygen varied from 0.5% light to 5.5% heavy. This work only just touches the edges of this field - many more interesting experiments remain to be carried out later.