Suspended Particle−Water Interactions Increase Dissolved 137Cs Activities in Typhoons (Fukushima).
The paper I'll discuss in this post is this one: Suspended Particle–Water Interactions Increase Dissolved 137Cs Activities in the Nearshore Seawater during Typhoon Hagibis (Hyoe Takata,* Tatsuo Aono, Michio Aoyama, Mutsuo Inoue, Hideki Kaeriyama, Shotaro Suzuki, Tadahiko Tsuruta, Toshihiro Wada, and Yoshifumi Wakiyama, Environ. Sci. Technol. 2020, 54, 17, 10678–10687)
The 137Cs isotope being discussed here is that released by the much discussed nuclear meltdowns at the Fukushima Dai-ichi nuclear power plant. It discusses the behavior of radioactive cesium released by the reactors when their containment buildings were damaged by a hydrogen explosion. The hydrogen was generated by a steam/zirconium interaction: Zr(s) + 2H2O(g) <-> 2H2(g) + ZrO2 solid. This reaction takes place at very high temperatures, temperatures that were experienced in the reactor core - zirconium is a key element in the structure of reactor cores as well as in the cladding of fuel elements - when the back up diesel generators that were supposed to keep the reactor cool during shut down failed when inundated with seawater.
Seawater killed about 20,000 people, but this is far less interesting to most people than the escape of radioactivity from the reactor, just as the 19,000 people who will die today, and died every day since March of 2011, and will die for an indefinitely defined people, from air pollution is not as interesting as the escape of radioactive materials from the reactors.
Cesium is a cogener of two elements that are essential to all living things, sodium and potassium. Physiologically cesium tends to behave very much like potassium, as does it's lighter cogener, rubidium. (Lithium is also a cogener of these elements.) Salts of these elements are all highly soluble in water, but cesium, and to a lesser extent, rubidium, tend to adhere to the surfaces of minerals commonly found in soil. The adsorption of cesium on to soil particles is a key point in the paper under discussion.
Natural cesium is not radioactive; natural rubidium and potassium are (slightly) radioactive owing to the naturally occurring long lived isotopes Rb-87 and K-40.
All human beings, indeed all living things, contain significant radioactivity as a result of the presence of potassium as well as its cogener rubidium, albeit to a lesser extent.
A common unit among many to quantify radioactivity is the "Bequerel," named for the scientist who discovered radioactivity in 1897. The Bequerel (Beq) is defined as one radioactive decay per second in any radioactive substance. The mBeq, the milliBequerel, which appears prominently in the paper is strictly speaking, 1/1000th of this amount. I mBeq is the number of decays that will take place in 1000 seconds. It is useful to think of mBeq as its reciprocal for values of less than 1000 mBeq; the reciprocal is the number of seconds (on average) that will pass before a decay is observed.
It can be shown that a 70 kg human being, owing to the natural radioactivity associated with potassium, will have about 4250 Beq of radioactivity in their flesh. There will also be some radioactivity associated with rubidium, which is not essential to human beings or other life forms but which is nonetheless almost always found in human and other living flesh. Rubidium can and does behave like potassium to some extent, particularly in instances of hypokalemia, too little potassium, where it can serve to ameliorate the shortage. One sometimes hears from a certain class of people that "there is no safe amount of radioactivity." These people are - there's no polite way to put this - idiots. Potassium is an essential element. Without potassium, one dies. It is thus essential that a healthy 70 kg human being contain around 4250 Beq of radioactivity.
In October of 2019, the Fukushima region was struck by a typhoon, and this paper is about the behavior of cesium which had adhered to soil particles after release from the reactor in this typhoon, as well as in high flow events in the rivers near the reactor.
From the introduction:
In 2019, 8 years after the accident, 137Cs activities in the waters >30 km offshore from Miyagi to Chiba prefectures on the Pacific Ocean side of Japan were approaching the 2010 pre-accident levels (<2.4 mBq/L), and 134Cs, which has a half-life of 2.06 years, is now almost undetectable because four half-lives have passed.(10)
In contrast, 137Cs activities in nearshore waters in the vicinity of the FDNPP and within 10 km of Fukushima and neighboring prefectures(11) are still higher than those before the accident.(12) It is known that longshore currents flow primarily from the north of the Pacific Ocean side of Japan,(13) so 137Cs activities in nearshore waters were statistically higher in the south than to the north of the FDNPP from 2014 to 2016.(14) Furthermore, the quantification of the fluxes of 137Cs associated with direct release from the plant, re-entry of 137Cs from sediments through the submarine groundwater discharge (SGD), and fluvial inputs have indicated that direct discharge is the principal source of 137Cs that has maintained the relatively high 137Cs activities in the coastal waters during the 2 year period of 2014–2016.(6,14?16) However, the contribution of the ongoing release has declined. A sharp decline in radionuclide releases with water from the FDNPP after completion of a frozen soil wall in 2015 and of the water treatment system (e.g., pumping up the polluted water)(17) was probably the result of a reduction in the flow from the FDNPP because the flux from the plant has been decreasing since then.(15) Hence, it is likely that the constant flux of 137Cs from rivers, the catchment areas of which are contaminated, now plays a more important role in the activities of 137Cs in coastal areas in addition to the re-entry of 137Cs from sediments through SGD, which increases dissolved 137Cs in coastal waters of the wide area from both north and south of the FDNPP.(16)...
...It has been recognized that dissolved Cs+ is the dominant form of cesium in the ocean, but cesium is found in both particulate and dissolved forms in coastal areas.(21) Although riverine radiocesium includes both dissolved and particulate forms, a high proportion of radiocesium in rivers is associated with particles.(22,23) In particular, the heavy rainfall from typhoons, which cause devastating floods over wide areas, could result in contaminated surface soils being swept into rivers. In fact, the particulate fraction of radiocesium accounted for almost 100% of the radiocesium in the particulate phase after the typhoon of September 2011, and the fluxes of particulate radiocesium accounted for 30%–50% of the annual radiocesium flux from inland to coastal ocean regions in 2011.(22) In addition to elucidating the dynamics of dissolved radiocesium in the marine environment, it is necessary to understand the dynamics of its particulate phase and the interactions between dissolved and particulate radiocesium when river water mixes with seawater in the coastal areas, in which salinity changes markedly from 0 to 34.
There are several studies available in the literature concerning the behavior of radiocesium in river–sea systems: Although much of the radiocesium carried by rivers is in particulate form (i.e., adsorbed onto suspended particles), the salinity increase along the system results in the desorption of this radiocesium from the riverine suspended particles, thus increasing radiocesium activity in the dissolved phase in coastal seawaters (Figure 1).(24?32)...
... The goal of this study was therefore to explore the distribution of radiocesium in dissolved and particulate phases in the downstream reaches of rivers and the nearshore and offshore waters south of the FDNPP shown in Figure 2 with their catchment areas and mean 137Cs inventories in Table 1 (see detailed information on sampling sites and methods in the Supporting Information). Particularly, we focus on to what extent the desorbed fraction of riverine radiocesium contributed to the elevated levels of 137Cs in the dissolved phase in the nearshore areas after the heavy rainfall from typhoon Hagibis in the middle of October 2019...
Figure 1:
The caption:
The caption:
Table 1:
The following figure refers to large volumes of water passed through a weighed dried 0.45 micron filter, designed to collect suspended particles, drying and weighing and then performing the counts of radiation obtained. The details can be found in the supplemental information which is open and free at the web page of the full paper.
The caption:
From the following graphic, one can estimate how much river water one would need to drink to get a single Beq of cesium-137.
The caption:
Radioactivity as a function of distance to the shoreline.
The caption:
The caption:
The overall amount of cesium-137 released into the ocean is rather prodigious, on the order of GBq/day. A unit of radioactivity the Curie (Ci) is roughly equal to the number of decays in one gram of radium, = 3.7 X 10^(10) Beq, 37 megaBeq. Thus amounts approximating a Curie/day leach into the ocean.
However, the ocean contains vast amounts of potassium. I have done some calculations elsewhere to show how much radioactivity is present in the ocean from potassium alone: How Radioactive Is the Ocean?. In this calculation, I showed that the potassium associated radioactivity of the ocean was approximately 530 billion curies, or 2 X 10^(22) Beq, 20 zetaBeq.
I trust you've having a pleasant Labor Day afternoon.
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I no longer possess the patience to read scientific articles. 
The world needs more smart people.
