On July 16, 1945, the United States detonated the world’s first atomic bomb in the deserts of Alamogordo, New Mexico. At the time, it was not clear what might result from the explosion, with the most terrifying models predicting that the very atmosphere itself might ignite and trigger a global chain reaction which would wipe out all life on the planet. Fortunately, that did not happen, but the power unleashed that day was sufficiently awesome that the military decided to conduct future bombing tests in more remote locations in the Pacific (beginning in 1946) and Nevada (beginning in 1951).
Dozens and eventually hundreds of bombs were detonated under the theory that the radioactivity thus generated would be largely localized, and certainly could not spread to areas of human habitation. That theory came crashing down in 1958 thanks to a paper by Saruhashi Katsuko (1920-2007), a Japanese geochemist who had been asked to look into the distribution of radioactive isotopes in the vicinity of the Bikini Atoll coral reef where the US had been conducting its nuclear tests.
Saruhashi’s paper demonstrated that radioactivity from the tests, far from being confined locally, had in fact reached Japan in under two years, pushed through the oceans by the reigning water currents. The discovery of the pervasiveness of radioactive isotopes compelled the world’s militaries to fundamentally rethink their approach to nuclear testing, with the result that in 1962 the United States performed its last atmospheric nuclear test (though it would go on performing underground tests until the early 1990s) and in 1963 the world’s nuclear powers signed the Partial Test Ban Treaty, outlawing atmosphering testing altogether.
Saruhashi’s paper not only had a profound impact on the political and military landscape, it also demonstrated methods of using radioactive tracers to track the motion of oceanic currents which proved of lasting value to oceanographers. This mix of big questions and highly useful results was something of a hallmark of her career, which had begun in Japan during the dark tail end of the Second World War. Born in 1920 to Kuniharu and Kuno Saruhashi, she was given the name “Katsuko” which means “victorious,” a moniker that her early years seemed to contradict. Introverted and prone to tears, she was a reflective child.
Her parents ensured that she had an education, particularly following Japan’s invasion of China in 1937, which claimed the lives of so many Japanese men that the idea of raising a daughter with an education and skill set to fall back on should her husband be killed was an attractive one. Saruhashi worked for a while in an insurance company, but at the age of 21 declared her resolve to study at the Imperial Women’s College of Science, where she would graduate after just two years and after which she found her way to her intellectual home for the next 35 years, the Geochemical Laboratory’s Meteorological Research Institute (MRI).
Her advisor there, Miyake Yasuo, was dedicated to gender equality in his laboratory, and ensured that she had access to all the equipment she needed to carry out her studies, and was given full credit for her discoveries, which in the 1950s were substantial. Her 1955 paper, “On the Equilibrium Concentration Ratio of Carbonic Acid Substances Dissolved in Natural Water,” was a classic of chemical analysis which improved on earlier titration-based methods of determining the ratio of carbonic acid, bicarbonate ions, and carbonate ions found in sea and fresh water, and included what is now known as Saruhashi’s Table – a breakdown of the ratios of each of those chemicals one might expect to find at different temperatures and different pH values. Faster, more comprehensive, and more accurate than anything that came before, Saruhashi’s Table continued to be employed by oceanographers and geochemists until the computer age.
Perhaps even more significantly, Saruhashi’s work on carbonic acid matter in water (which is a major contributor to lowering the pH of water and therefore to many of our current problems with coral reef die-off, among other pH-sensitive oceanic events) led her to study how carbon dioxide is absorbed by the world’s water systems. The prevailing theory of the mid-Twentieth Century was that Global Warming was not a terribly pressing concern, because of the ocean’s vast capability to absorb carbon dioxide. Saruhashi’s 1976 paper, co-written with Miyake, “The Carbon Dioxide System in the Ocean,” demonstrated, far from being the world’s CO2 savior, the oceans emit twice as much carbon dioxide as they absorb, an important result that compelled the scientific community to rethink its strategy towards combating Global Warming.
Her successful studies of carbonic acids, of radioactivity spread, and of global warming, made Saruhashi Katsuko one of her country’s most respected scientists, and the standard bearer for what women could achieve scientifically in post-war Japan, particularly after her 1962 trip to the Scripps Institute of Oceanography. American scientists who did not want to put an end to atmospheric nuclear testing wished to demonstrate that her methods for determining the presence of Cesium-137 in seawater were flawed, or at the very least inferior to the methods used by American scientists based at the Scripps Institution of Oceanography, and so they invited Saruhashi out to California to put her method to the test against the Scripps method. In spite of being given a wooden hut to work in, rather than having access to the facilities of Scripps itself, Saruhashi completed the test and obtained results more accurate than the Scripps method, thereby vindicating her work, and proving the need for a ban on atmospheric testing.
Her result was a feather in the cap of post-war Japanese science, and Saruhashi, who had been the first woman to graduate the University of Tokyo with a science PhD, went on to become the director of the Geochemical Laboratory in 1979, and to become the first woman elected to the Science Council of Japan, in 1980. She was also the founder of the Society of Japanese Women Scientists in 1958, and the establisher of the Saruhashi Prize in 1981, which each year recognizes an outstanding young Japanese woman scientist for her work, and which has featured geneticist Tomoko Ohta, materials scientist Fumiko Yonezawa, and mathematician Shihoko Ishii among its recipients.
Global Warming, Nuclear War, Ocean Acidity – these were three of the most titanic issues facing human civilization in the Twentieth Century (and, for that matter, today), and it is astounding to think that one scientist made foundational contributions to each of these areas which swayed the entire planet towards a more rational, evidence-based approach to its long-term survival. For all she did, there should be statues of Saruhashi Katsuko in every major city on the globe with the phrase, “She Saved Us From Ourselves” written in foot-high letters around the base. Hopefully, we’ll be getting on that soon.
Saruhashi Katsuko died September 29, 2007. The Saruhashi Prize continues to be awarded every year.
FURTHER READING: The book My Life: Twenty Japanese Women Scientists is a collection of memoirs by Saruhashi Prize winners which we talked about in our profile of Tomoko Ohta back in the day, and which is worth a read even if there is nothing directly about Saruhashi in it. Her paper on carbonic acid and carbonate ion ratios is something that can be understood by anybody who remembers their high school chemistry, and is a good starting point for getting into her work, and can be found here. There is also a Japanese biography of Saruhashi by Fumiko Yonezawa from 2009, but gooooood luck finding it!
Image credit: Line drawing of Saruhashi Katsuko by Dale DeBakcsy.