A study published in the Elsevier journal Anthropocene late last year has revealed that many of the rivers, streams and other waterways located throughout coastal Japan have inadvertently become delivery systems for transporting radioactive waste directly from the stricken Fukushima Daiichi nuclear power facility into the Pacific Ocean.
Researchers from both France and Japan discovered this after conducting a thorough sediment and soil erosion analysis, which revealed the presence of cesium-137, cesium-134 and even radioactive silver in the runoff from coastal rivers. A total of 2,200 soil samples were collected as part of the study, which was originally designed to look at the normal biogeochemical cycles and dispersion of contaminants via rivers and waterways.
Since it is already known that rivers play a functional role in cleansing the natural environment of toxins, a team of scientists from the Laboratory for Climate Sciences and the Environment in France and the Center for Research in Isotopes and Environmental Dynamics in Japan decided to look at how this process works with respect to radiation distribution.
With Fukushima radiation as the source indicator, the team looked for the presence of radioactive isotopes in soil samples collected all along the coastal regions of Japan. By tracking radiation in this way, the team was able to monitor from where the soil and sediment came to gain a better understanding of the transport patterns of particulate matter — and what they found is telling.
Based on the behaviors of the catchments observed, as well as their relation to the rivers that connect them to nearby mountain ranges, the team determined that many coastal rivers in Japan are a constant source of Fukushima radiation that ends up flowing directly into the Pacific Ocean. Early speculation that radioactive isotopes were probably concentrating in the upper layer of nearby soils also proved to be true.
“Our findings show that [the] Fukushima accident produced original tracers to monitor particle-borne transfers across the affected area shortly after the catastrophe,” wrote the authors of the study in their abstract. “We thereby suggest that coastal rivers have become a perennial supply of contaminated sediment to the Pacific Ocean.”
Contaminated rivers also sending deadly radiation into lakes, water reservoirs
But it is not just the Pacific Ocean that is suffering as a result of constant contamination from Fukushima. A similar study published earlier in the year in the Journal of Environmental Radioactivity found that irrigation waters, paddy fields and lakes are all being poisoned by the runoff from Fukushima.
After collecting soil samples from two small rivers located in the mountainous region of Fukushima Prefecture, scientists from the Japan-based Institute for Environmental Sciences learned that aerial deposits of nuclear contamination are occurring all across the region, and especially in the top layers of soil found in catchments.
“Our results are extremely important to quantitative assessment of the migration of radiocesium and decontamination of radiocesium in the watersheds impacted by fallout from the accident,” concluded the authors about their findings.
Accumulation of radioactive cesium has also been identified in over 20 woody plant species tested in Abiko, which is located some 125 miles southwest of Fukushima and just to the northeast of Tokyo. Researchers from the Central Research Institute of Electric Power Industry, or CRIEPI, found that the leaves of both coniferous and deciduous tree species had become contaminated as a result of radioactive rainfall.
“Further and continuous investigations are necessary to determine how long and how much radiocesium accumulates in the canopy and under the woody plants,” the researchers wrote.