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Mon Sep 7, 2020, 05:13 PM

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:

More than half of the radiocesium (i.e., 134Cs and 137Cs) released as a result of the Fukushima Dai-ichi nuclear power plant (FDNPP) accident was deposited and/or released into the nearshore ocean.(1−4) That radiocesium, however, moved via dilution and advection into the open ocean because the FDNPP is located at a coastal site, and the adjacent coastal waters are directly connected to the North Pacific Ocean. The decrease in radiocesium activity in water column in the offshore area to 0.1 Bq/L within 1 year(5,6) led to a rapid decline in Cs levels in marine organisms.(7−9)
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:

Figure 1. Schematic diagram of riverine suspended particle behavior (light brown arrows) along the southward-flowing coastal current (blue arrow) including high radiocesium water from the plant in the coastal zone of Fukushima Prefecture from the FDNPP to the south of the prefecture. The dark blue arrow indicates the ground water discharge. The box at the right hand indicates sources of (1) the FDNPP site local sources (that can come in many forms, from GW at the site to tank leaks to over land contamination/rain inputs, etc.), (2) the more disperse release from GW associated with beach sands (Sanial et al.(16)), and (3) rivers and desorption. Riverine suspended particles introduced into the marine environment provide dissolved radiocesium through the desorption process while drifting in the longshore current.

The caption:

Figure 2. Sampling stations in the vicinity of the FDNPP (red circles: stations in downstream reaches of rivers; light blue circles: nearshore stations; dark blue circles: offshore stations). Area α is the area within a 30 km radius of the FDNPP. Area β is the area outside of Area α. The spatial distribution of 137Cs inventory is based on the third airborne survey by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) in 2011; the 137Cs inventory data were obtained from the website of the Japan Atomic Energy Agency; Airborne Monitoring in the Distribution Survey of Radioactive Substances (https://emdb.jaea.go.jp/emdb/portals/b1010301/).

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:

Figure 3. Distribution of (A) temperature (Temp.), (B) salinity (Sal.), (C) suspended particles, and (D) particulate 137Cs in rivers (Tomioka, Kido, Asami, Natsui, Fujiwara, Same, and Binda rivers) and adjacent nearshore (S1–S6) and offshore (O1–O12) stations. Gray circles indicate the geomean value in each station. Errors are not shown in this figure for readability but are listed in Table S1.

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:

Figure 4. Distribution of (A) dissolved 137Cs, (B) particulate 137Cs, (C) percentage of particulate 137Cs in total 137Cs, and (D) Kd values in rivers (Tomioka, Kido, Asami, Natsui, Fujiwara, Same, and Binda rivers) and adjacent nearshore (S1–S6) and offshore (O1–O12) stations. Gray circles indicate the geomean value in each station. Errors are not shown in this figure for readability but are listed in Table S1.

Radioactivity as a function of distance to the shoreline.

The caption:

Figure 5. Variation in the river–nearshore–offshore system as a function of distance from the shoreline (0 km) in (A) 137Cs in particles, (B) dissolved 137Cs, (C) particulate 137Cs, and (D) Kd values. Negative distances indicate the fluvial area; positive distances indicate the offshore area. Errors are not shown in this figure for readability but are listed in Table S1.

The caption:

Figure 6. Light blue and blue bars indicate the estimated desorbed 137Cs activity (DesCsdis in eq 2) and observed dissolved 137Cs activity in which estimated desorbed activity has been deducted. Blue bars could originally include seawater through ongoing release from the FDNPP facility and re-entry through SGD. (A, B, C) Fraction (f) in eq 2 = 0.03 and (D, E, F) f = 0.3. Graphs on the left side of each figure are the pre-typhoon period in 2019 (high-river-flow condition from June to September). Graphs on the right are from the post-typhoon period. Dissolved 137Cs activity for offshore in (A) and (D) is mean value of station O1–4 (6.6 mBq/L). Dissolved 137Cs activity for offshore in (B), (C), (E) and (F) is mean value of station O5–12 (3.2 mBq/L). An asterisk (*) indicates a 137Cs concentration of 12 mBq/L at station TD-9 (37°20.0′N,141° 4.3′E) sampled on 14 Nov. 2019. Double asterisks (**) indicate a 137Cs concentration of 11 mBq/L at station M-G0 (37°5.0′N,141°8.4′E) sampled on 2 Nov. 2019. Both of these values were provided by the Nuclear Regulation Authority (https://radioactivity.nsr.go.jp/en/list/292/list-1.html).

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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Reply Suspended Particle−Water Interactions Increase Dissolved 137Cs Activities in Typhoons (Fukushima). (Original post)
NNadir Sep 7 OP
Ferrets are Cool Sep 7 #1
NNadir Sep 7 #2
Ferrets are Cool Sep 7 #3
Warpy Sep 8 #4

Response to NNadir (Original post)

Mon Sep 7, 2020, 05:42 PM

1. As much as I love this stuff

I no longer possess the patience to read scientific articles.

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Response to Ferrets are Cool (Reply #1)

Mon Sep 7, 2020, 07:15 PM

2. No problem. They're not for everyone, especially those that I write.

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Response to NNadir (Reply #2)

Mon Sep 7, 2020, 07:47 PM

3. I salute you!!!!

The world needs more smart people.

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Response to NNadir (Reply #2)

Tue Sep 8, 2020, 06:33 PM

4. It's a nice vacation from the heavy virology I've been grappling with lately

I took microbioloby in those innocent days before AIDS and viruses were given short shrift. The field has exploded since then and I've been busy hacking and slashing my way through a couple of parallel courses.

Reading about a measurable Ce137 increase in sea water after a typhoon is almost restful.


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