To address the problem of nuclear wastewater storage, the Japanese Cabinet enacted a measure on August 26, 2021, authorizing the discharge of treated Fukushima nuclear disaster tainted water into the Pacific Ocean.
When high concentrations of radionuclides are breathed by marine species, they can disrupt marine biological chains and have a negative impact on marine fisheries and human health.
The worldwide consequences of the Fukushima disaster, which will span 30-40 years, are unclear. As a result, determining the mechanism of radioactive water dispersion in seas is crucial.
To address this issue, a team from Tsinghua University in China created analytical models from both the macroscopic and microscopic viewpoints in order to replicate the nuclear element diffusing process.
The former is concerned with the overall distribution of pollutants, whereas the latter is concerned with the behavior of specific contaminants.
Macro modeling findings (Figure b) show that in the early stages of pollution discharge, the contaminated region expands fast, reaching 30° latitude 40° longitude after 120 days. Pollutant diffusion speed is much faster in the latitude direction than in the longitude direction due to ocean currents.
The contaminants will then travel quickly to the South Pacific Ocean, aided by the equatorial current that runs through the Panama Canal. In 2400 days, the Indian Ocean will be impacted by waters infiltrating from north of Australia. By 3600, the contaminants will have covered nearly the whole Pacific Ocean.
Figure d depicts the team’s plot of pollution concentrations in surrounding waterways of Miyazaki, Shanghai, and San Diego, all of which are approximately 30°N. In order of distance from Fukushima, Miyazaki is the most contaminated, followed by Shanghai and San Diego.
Although San Diego is the latest of the three cities to be afflicted, the steady-state concentration of pollution in its nearby waterways is higher than that near Miyazaki.
The strong ocean current near Japan causes disparities in pollution concentrations around Miyazaki, Shanghai, and San Diego. Fukushima is specifically placed at the junction of the Kuroshio (northward) and Oyashio (southward) rivers (southward).
As a result, most contaminants do not travel north and south along land borders, but instead expand eastward with the North Pacific west wind drift. The influence of treated water outflow on coastal Asia should be considered early on. However, the large concentration of radioactive materials near North America will undoubtedly become an issue at a later point.
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