Hydrogen isotope biogeochemistry reactors in 1988, but nuclear weapons testing in the 1950s added large spikes of radioactive elements to the atmosphere, especially radiocarbon and tritium. This complicated measurements for geologists using radiometric dating of carbon. However, some oceanographers benefited from the tritium increase, utilizing the signal in the water to trace physical mixing of water masses. In biogeochemistry, scientists focused primarily on the stable isotope of deuterium as a tracer for environmental processes, especially the water cycle. The American geochemist Harmon Craig, once a graduate student of Urey's, discovered the relationship between rainwater's hydrogen and oxygen isotope ratios. The linear correlation between
Pertechnetate is found in a Meckel's diverticulum with Meckel's scans. All technetium salts are mildy radioactive, but some of them have explored use of the element for its chemical properties. In these uses, its radioactivity is incidental, and generally the least radioactive (longest-lived) isotopes of Tc are used. In particular, Tc (half-life 211,000 years) is used in corrosion research, because it is the decay product of the easily obtained commercial Tc isotope, which is its nuclear isomer. In theory, the longest-lived technetium isotope, Tc (half-life 4.2 million years), would be the optimal isotope for this use. Solutions of technetate(VII) react with