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
Bioremediation of radioactive waste suitable for transfer to a nuclear waste repository). Phytovolatilization involves the capture and subsequent transpiration of radionuclides into the atmosphere. It does not remove contaminants but releases them in volatile form (less harmful). Despite not having too many applications for radioactive waste, it is very useful for the treatment of tritium, because it exploits plants' ability to transpire enormous amounts of water. The treatment applied to tritium (shielded by air produces almost no external radiation exposure, but its incorporation in water presents a health hazard when absorbed into the body) uses polluted effluents to irrigate phreatophytes. It becomes a system