Katsuko Saruhashi

Career

Saruhashi conducted research with Teruko Kanzawa from 1973 to 1978. They began their research by measuring the pH of every rainfall event over the five-year period at the Meteorological Research Institute in Tokyo. On average, they found the pH to be around 4.52 which was an increase from 4.1 in the previous years of research done by Miyake in 1939. According to Miyake, the pH varied during different seasons (summer and winter); however, Saruhashi noted no variation between seasons in their findings, showing how conditions changed during the 1970s.

Nuclear tests

Katsuko Saruhashi made several discoveries in both geochemistry and, most notably, oceanography. The most salient of these are: Saruhashi's Table; her novel method for measuring the amounts of caesium-137 and strontium-90 in seawater, and her research concerning the environmental impact of the US bomb test site, Bikini Atoll, which ultimately provided justification for the prohibition of above-ground nuclear testing. She also made important contributions to the study of the carbon dioxide system in the oceans, finding that the Pacific Ocean emits more CO₂ than it absorbs.

Saruhashi's table

Presented in her 1955 paper ‘On the Equilibrium Concentration Ratio of Carbonic Acid Substances Dissolved in Natural Waters: A study on the Metabolism in Natural Waterways’, Saruhashi's table provided oceanographers with a method for determining the composition of three carbonic acid substances based on water temperature, pH, and salinity.

Artificial radioisotopes in seawater

In response to the influx of nuclear testing occurring in the Pacific, the Japanese Government requested that Saruhashi – along with Yasuo Miyake - lead a research project into the long-term and global effects of such activities. To do so, Saruhashi worked at the Central Meteorological Observatory in Tokyo to find a new method for measuring radioactive fallout. The findings of Saruhashi and Miyake investigation were explicated in their paper 'Cesium 137 and Strontium 90 in Sea Water'.

Their studies concluded that in the Western North Pacific, there were substantially higher amounts of ¹³⁷Cs and ⁹⁰Sr than were found in samples obtained from the Atlantic and Northeast Pacific. Given these results, Saruhashi and Miyake concluded that the differing quantities of artificial radioisotopes found in the Pacific was a direct consequence of the nuclear testing occurring in the Pacific Tropics.

Despite the corroborating evidence in favor of Saruhashi's claim concerning the discrepancy in the quantity of ¹³⁷Cs and ⁹⁰Sr present in different regions of the Atlantic and North Pacific, conclusion was challenged by {American scientists}, who called into doubt the methodology and technique applied by Saruhashi's team; contending that their novel investigatory method was fallible and erroneous.

Bikini Atoll fallout

The contention surrounding the methodology that Saruhashi's team used was settled two years after the publication of her research concerning the artificial radioisotopes in seawater. The US Atomic Energy Commission funded a six-month long lab swap in which Saruhashi met with fellow oceanographer Ted Folsom at the Scripps Institution of Oceanography at the University of San Diego. Saruhashi's team used absolute standards for ¹³⁷Cs, different from those accepted by the scientific community in the United States. This largely attributed to the skepticism of American scientists regarding Saruhashi's work, as well as the political climate at the time. The United States was likely against the ban on above-ground nuclear testing, as this would make it more difficult for them to develop nuclear weapons. In order to compare the two scientists' respective methods for the analysis of ¹³⁷Cs in seawater, Saruhashi and Folsom were both tasked with analyzing the values of ¹³⁷Cs present in identical samples of seawater. Despite the independent absolute standards of ¹³⁷Cs, and use of different reagents and gamma analytical techniques, there was less than 10% discrepancy between the results of the two laboratories. Some discrepancy can be attributed to inconsistent settling of the sediment during the specimen's travel by boat. Although efforts were made to ensure that the samples being compared were as similar as possible, this experiment relied on the assumption that the samples compared were identical, which is unlikely since the precise location and time of collection varied. However, the results of the two laboratories were extremely similar. After the six-month lab-exchange ended, it was clear that Saruhashi's method provided incredibly accurate and consistent results; and therefore, the two distinct analytical techniques were both appropriate scientific approaches for measuring the quantity of artificial radioisotopes in seawater. As a result, given they were no longer subject to dispute, Saruhashi's findings could serve as justification for the prohibition of above-ground nuclear testing.

Seawater carbon dioxide absorption

In 1956, Saruhashi and Miyake discussed in great detail how oxidation of organic material served to augment the values of carbon dioxide present in seawater. Previous to their study, it was believed that the high values of carbon dioxide and alkalinity present in the oceans resulted from the dissolution of calcium carbonate. Saruhashi demonstrated that this hypothesis was untenable; as a consequence, scientists were no longer able to purport that global warming could be mitigated naturally by seawater's supposed capacity for the absorption of carbon dioxide gas. Instead, Saruhashi and Miyake provided empirical evidence that seawater in the Pacific releases twice as much CO₂ as it absorbs.

Influence over women in science

Saruhashi spent much of her career actively fighting for equal opportunity in science and advocating for women. She acknowledged the reasons why women are under-represented in science, saying, “the lack of equal opportunity is one. There is also the attitude of society, of parents and teachers. And there is little recognition of the contributions of women scientists.” She worked to establish both funding opportunities and community for women scientists.

In 1958, Saruhashi established the Society of Japanese Women Scientists to promote Japanese women in science. In 1967, she attended the second International Conference of Women Engineers and Scientists with a group of Japanese women scientists and engineers, speaking on the Importance of Fishery in Food Problems.

In 1981, she established the Saruhashi Prize, a $2400 cash award given to a Japanese woman fifty years old or younger who has made considerable contributions in the physical sciences. The award is also intended to help those wanting to pursue projects overseas. Saruhashi wanted to gift the award recipients larger amounts, contributing personally and with help from friends, but the funds are small compared to other prizes.