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 measurement nowadays. The commercial products of GC-IRMS include both combustion and pyrolysis interfaces so that δC and δD can be measured simultaneously. The significant advantage of GC/pyrolysis method for hydrogen isotope measurement is that it can separate different compounds in the samples. It requires the smallest sample size (a typical size of ~ 200 ng) relative to other methods and also has a high precision of 1~5 ‰. But this method is relatively slow and limited to the samples which can be applied in GC system. Laser Spectroscopy (or Cavity ring-down spectroscopy, CRDS) is able to directly measure D/H, O/O