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
Hydrogen isotope biogeochemistry spectroscopic lines for publishable data, Murphy and Urey paired with Ferdinand Brickwedde and distilled a more concentrated pool of heavy hydrogen, known today as deuterium. This work on hydrogen isotopes won Urey the 1934 Nobel Prize in Chemistry. Also in 1934, scientists Ernest Rutherford, Mark Oliphant, and Paul Harteck, produced the radioactive isotope tritium by hitting deuterium with high energy nuclei. The deuterium used in the experiment was a generous gift of heavy water from the Berkeley physicist Gilbert N Lewis. Bombarding deuterium produced two previously undetected isotopes, helium-3 and hydrogen-3. Rutherford and his colleagues successfully created tritium, but incorrectly