Sheep and Chernobyl

Dear Reader,

I have just discovered that the Chernobyl related controls which were imposed on sheep farms in England and Wales have just been lifted. The radioactive cesium from Chernobyl will have become weaker because of the radioactive (physical) decay, while the cesium-137 will only have decayed slightly the cesium-134 will have decayed a lot by now.

I imagine that by now that the cesium will have migrated deeper into the soil, this makes the cesium less able to enter the grass. Also I am hoping that the cesium will be more tightly bonded now to the soil minerals, one of the problems with the hill sheep farms is that the soil is poor in potassium and the minerals which will bind the cesium are not present in large amounts. This will lower the Kd value for cesium in the soil as a result the plants will be more able to absorb the cesium via their roots.

I saw with interest that Naofumi Kozai, Toshihiko Ohnuki, Makoto Arisaka, Masayuki Watanabe, Fuminori Sakamoto, Shinya Yamasaki & Mingyu Jiang published an article (Chemical states of fallout radioactive Cs in the soils deposited at Fukushima Daiichi Nuclear Power Plant accident) in the Journal of Nuclear Science and Technology, 2012, volume 49, issue 5, pages 473 to 478.

In this paper the authors report some leaching experiments which have been done on cesium contaminated soil from Japan, they found that the majority of the cesium stayed in the soil even when the soil was treated with ammonium chloride and acetic acid solution. This suggests to me that much of the cesium is locked up inside the soil which will prevent both the easy washing of the cesium out of the soil and also prevent the plants absorbing the cesium with ease.

More about prussian blue

Dear Reader,

Now some of my readers have become interested in Prussian blue, this is the miracle drug which removes cesium from human bodies. I was recently reading the work of Peter W. Stephens et. al., Inorganic Chemistry, 2010, 49, pages 1524 to 1534. His paper is about the crystal structures and magnetic properties of mixed oxidation state manganese versions of Prussian blue. This has allowed us to use X-ray technology to look inside a prussian blue crystal.

Here is a chance to look at the potassium version of the prussian blue, it is clear that the potassium atoms are in channels which run through the solid.

K2Mn{Mn(CN)6}

The way in which the prussian blue works is to allow out the potassium, the cesium ions then diffuse in to take the place of the potassium ions. When the potassium ions are replaced in this solid with cesium the larger cesium ions cause the solid to change slightly. Here is a picture of the cesium solid.

Cs2Mn{Mn(CN)6}

I checked the literature and other prussian blue like model compounds have similar structures, one early report was made by R. Rigamonti, Gazzetta Chimica Italiana, 1938, 68, 803-809. Where this italian reported a potassium salt of Co[Fe(CN)6]. I think that due to the ligand field energy effects this was a simple cubic solid which looked just like the cesium one which I showed above.

Now I am going to tell you the story about how I found out about Prussian blue, years ago in 1999 I went on an adventure to eastern europe. I joined Josef Novosad’s research group for a while. While I worked with Josef on phosphorus chemistry (we both share an affinity for this element), between making some interesting compounds which may have improved our understanding of dithioimidodiphosphinates and enjoying the delights of Brno (it is a very wonderful place) we did talk about chemistry.

One of the things which Josef told me about was what he did in his youth, he told me that he was given a job by the communists working on uranium in farmyard animals at a research centre close to Brno. But after the Chernobyl accident he was moved onto cesium in farmyard animals. What used to happen at Josef’s research site was that an animal would be given a dose of 1 MBq of Cs-137, then using additives to the animal’s feed the workers would then try to remove the cesium from the animal.

Before anyone gets worried about the effect of the cesium on the farmyard animal lets do an estimate of the dose which the animal gets. If we assume that the animal is identical to a typical human in size and that it is identical to a human then we can use the data for humans. Using the radiation protection advice from a US university we can get a thing called an ALI for oral exposure to Cs-137. The ALI is the Annual Limit of Intake which for Cs-137 in the US is 100 microcuries. As 1 Ci = 37 GBq this works out as a dose of 3.7 MBq to the animal being the limit. The US limit is worked out based on a 5 rem dose to the body. So the animal will get 1.35 rem. Now some of you might be getting a bit confused with the different radiation units. Here is a look up sheet

100 rem = 1 Sv

100 rad = 1 Gy

1 Curie = 37 GBq = 37000 MBq = 37000000 KBq = 37000000000 Bq

1 milli Curie = 37 MBq

1 microcuries = 37 kBq

So our “animal” will have got a 13.51 mSv dose, this dose is far too small to cause “radiation sickness”. If we repeat the calculation using the ALI value used in Sweden (based on a 20 mSv dose) which is 1.5 MBq then our animal gets a dose of 13.33 mSv. This is not a dose which will make the animals die of radiation sickness and if we use the accepted dose to chance of cancer conversion factor of 5 % for a 1 Sv dose then if we assume that the LNT model is right then if the animal was a human then it would have a 1 in 1500 chance of getting cancer as a result of the cesium intake. As most farmyard animals weigh more than a human the real dose to the animal would be likely to be lower.

To put it in perspective if I got a dose of 13.3 mSv at work then I know that my radiation protection officer would be very very concerned about me but I would not have gone over the yearly limit for a classified radiation worker, but if I got that dose in one month in Sweden then it would trigger an investigation into me. Such a dose is in the range where the national radiation protection authority would want to know what I was doing and how I got the dose. However if a member of the public got that dose at work then I imagine that the national radiation protection would be hopping mad to say the least ! The occupational dose for a non radiation worker is only 1 mSv per year, as a non-radaition worker is unlikely to be wearing a film or TLD badge then it might take quite a lot of extra work to work out the dose compared with the effort needed to estimate a dose for a dosemeter wearing radiation worker.

But lets get back to the prussian blue.

Josef told me that he tried almost every transition metal, I think that he did not try using nickel as nickel is toxic. He then used the batches of the “prussian blues” to try to clean the animals up. What Josef found was that no two batches of prussian blue which he made worked quite the same way in the experiments. So my advice to anyone planning on making prussian blue for medical use in Japan is that the production of the medical grade solid is not a simple matter, I have to confess that I do not know how to reliably make medical grade prussian blue.

If you want to read about Josef’s cesium work then see  H. Prochazka, J. Jandl, J. Novosad, O. Neruda, J. Hejzlar and S. Spelda, Veterinarni Medicina, 1991, 36, 341 to 348. The paper is entitled “Affection of Radiocesium Retention in Miniature Pigs”

The abstract of this paper comments that stable cesium (1 mg per kilo of body weight) is not effective as a means of removing cesium from pigs. Josef and J. Jandl published another paper in which they used a modified zeolite to treat sheep which were contaminated with cesium. This paper can be found at “In-Vivo Reduction of Radiocesium by Modified Clinoptilolite in Sheep”, Veterinarni Medicina, 1995, 40, pages 237-241.

Have the sunflowers failed

Dear Reader,

I have read that the sunflower plants in Japan have failed to remove much cesium from the soil, it was reported in a Japanese news paper that suggested that if 10 kilos of sunflowers are grown per square meter that only 0.2 % of the cesium will be removed. The problem with phytoremediation is that ability of the sunflower plants to remove the cesium will depend a lot on the Kd value for the soil. I know that sunflowers which are grown under soil free (hydroponic) conditions are very good at absorbing the cesium.

This failure of the sunflowers to absorb the cesium may in some ways be a good thing, it may suggest that the Kd value for cesium on the Japanese soil is very high. In some ways a high Kd value for cesium is good, if the cesium sticks like glue to the soil then it will be less able to enter plants. The best possible soil for the Japanese to have would be a potassium rich soil which has plenty of clay in it.

I predict that for farming that this year will be the worst for cesium, this year cesium will have been able to absorb through leaves and the other surfaces of plants which are above the ground. In future years the cesium will have to pass through the soil, the soil will act as a filter which will reduce the uptake of the cesium by the plants.

The Japanese have found that by removing the top layer of the soil that they are able to greatly lower the cesium contamination level, but they will create vast amounts of contaminated soil. I would suggest that for the worst hot spots that the Japanese should scrap the soil but for less contaminated areas they should deep plough the soil to put the cesium out of reach of the roots of grass. An alternative is to only grow oil crops like sunflowers / rape or plants which have very deep root systems.

It has been shown that sunflowers can be grown on radioactive land with very little of the cesium entering the plants, which sets us up well for biodiesel production.

Very little cesium is transferred into the part of the plant which is pressed to provide the oil. So the sunflowers could play a role in the cleanup of the area. The farms near to the stricken reactors could be used to grow vast fields of oilseed rape. This oilseed rape could then be pressed to give oil which will be very low in cesium. The oil could then be converted into FAME diesel, the conversion process is likely to lower the cesium content yet further.

The FAME biodiesel could help Japan as it normally has to import lots of motor fuel, so the product of these farms would have a use rather than being a crop which has no use. So maybe together with things like prussian blue the sunflowers may have a role to play in the recovery.

Cesium maps for Japanese farmland

Dear Reader,

The Japanese government have issued maps of cesium contamination on farmland in the areas near to the Fukushima reactor accident. The main map of that area of Japan is here. Based on a google translate examination of the text with the map the soil has been taken from paddy fields at up to 15 cm depth while for upland soils it is the top 30 cm of soil. If any of my readers can read Japanese then I would be very grateful if they could give me a translation of the text from the Japanese Agriculture, Forestry and Fisheries Research Information Technology Center.

The bad news is that the cesium level in some areas is high, but the good news is that there are things which normal farmers can do which will lower the transfer of cesium to the food crops. I think that farms are going to need to learn a few new skills to allow them to farm in a safe and healthy way using their contaminated land.

Peachs, cesium, fruit and fukuashima

Dear Reader,

I have read with interest the blog of a lady called Dr Susan Burton who teaches English at a Japanese University. She is quite reasonable to be concerned about the levels of radioactivity in her diet. In her blog she questioned the wisdom of selling fruit from the Fukuashima area in the supermarket, right now I can not say if they are safe or not to eat. This question is one which can be better answered by the radiation protection authority in Japan.

Susan lamented that the cesium has a half life which is greater than a decade, she was worried that the cesium would spoil her enjoyment of Japan for a very long time. This comment about cesium and peaches prompted me to check the literature on radioactivity and fruit.

Back in 2001 a person in Italy published a review paper on the transfer of radioactivity from soil to fruit (F. Carini, Journal of Environmental Radioactivity, 2001, volume 52, pages 237 to 279). I went through this review and I found some data for peach trees.

One of the most important things to know about farming in a radioactive area is the transfer factor. The transfer factor is a measure of how easy it is for radioactivity to get from the soil into the part of the plant which you eat. It is defined as the ratio of the radioactivity (Bq kg^-1) of the food to the radioactivity level of the soil (Bq kg^-1). It is important to bear in mind that the transfer factor depends on the species of the plant, the soil type and the element.

Element	Soil type	Transfer factor
Cs	Not recorded	0.0131
Cs	Sandy loam	0.009
Sr	Not recorded	0.0218
Sr	Sandy loam	0.07
Pu	Not recorded	0.000163
Am	Not recorded	0.000436
I	Not recorded	0.0109
Ru	Not recorded	0.00109
Ce	Not recorded	0.000436
Cm	Not recorded	0.000436

As the main radioisotopes released by the accident were noble gases, iodines and cesiums it should be clear from the table above that in future years the humble peach tree will have a filtering effect. While most people do not like eating mud, if you were to eat mud then you would get a greater intake of cesium than if you ate the same mass of fruit from a tree grown on the radioactive soil.

I predict that in future years that the radioactivity level in the fruit will be dictated by the absorption of radioactivity by the roots of the tree and the transport of the radioisotopes through the tree into the fruit. But this year due to the direct deposition of radioactivity onto the leaves of the plant we need to consider a different route.

Sadly I could not find any results for peach trees but for bean plants I could find some results. In an experiment a leaf of a bean plant was soaked in a solution of a radioisotope to simulate radioactive rain. Then the plant was grown further before the radioactivity levels in different parts of it was measured. It was found that most of the radioactivity absorbed remained in the leaves.

Only 13 % of the cesium, 0.06 % of the strontium, 0.2 % of the americium and 0.002 % of the plutonium was found in the bean pods.(P. Henner, C. Colle and M. Morello, Journal of Environmental Radioactivity, 2005, volume 83, pages 213 to 229) This suggests that while cesium might be mobile inside plants the other elements are not very mobile inside the plants. While this effect may protect the consumer from plutonium, strontium and americium (which have not been released from Fukuashima in large amounts) due to the fact that the cesium is mobile it is possible that fruit grown this year on trees may be contaminated by cesium which was absorbed directly into leaves and then transferred through the plant into the fruit. So this year great care is needed to check the contamination level of the fruit, in future years it is likely that the cesium contamination level in the fruit could be much lower than this years contamination level.

Now one of the wicked lies which some parts of society like to either spread about deliberately, imply or assume is that humans are powerless in the face of the evil radioactive atoms. This idea is clearly wrong in several ways.

1. Atoms and radiation knows no morality, no matter how good or evil you are atoms / radiation will treat you the same way.
2. Humans can take action to alter their exposure to radiation and radioactivity.

For example by changing farming methods the level of cesium in the crop can be lowered. I saw one paper (W.L. Robison, P.H. Brown, E.L. Stone, T.F. Hamilton, C.L. Conrado and S. Kehl, Journal of Environmental Radioactivity, 2009, volume 100, pages 76 to 83) which explained that by using potassium fertiliser on coconut trees which were growing on Bikini island (Where the Americans used to test H-bombs) that the cesium level in the edible parts of the coconuts can be greatly lowered.

My advice to any Japanese farmers who might be reading this blog is to do the following.

1. Find out what sort of soil your farm has.
1. Clay soil tends to bind cesium more than sandy soil
2. Find out from a cesium map how contaminated your farm is likely to be
3. Ask the farmer’s union, TEPCO and the state radiation protection authority for advice on how to lower the contamination level of your crops. I would suggest that you ask about the following
1. Deep ploughing to prevent the transfer of cesium via grass to livestock
2. Prussian blue to decontaminate livestock
3. Potassium fertilizers to prevent plants taking up cesium
4. Changing to a different crop which is less able to take up contamination. Oilseed rape might be a good plant. The oil pressed from the seeds is normally has very little contamination in it even if the rest of the plant is contaminated. Also onions may be a good crop to plant. Below is some data from 1989 in Finland ( A. Paasikallio, A. Rantavaara and J. Sippola, The Science of the Total Environment, 1994, volume 155, pages 109-124) which shows that some crops are better able to avoid taking up cesium from the soil.

Transfer factors for different crops in three different soil types

Cesium in beef

Dear Reader,

I have discovered from the news that radioactive cesium has been found in beef (http://news.yahoo.com/more-radioactive-beef-shipped-japan-161903589.html), it appears that the cattle were fed straw which was contaminated with cesium.

This looks to me like a classic case of contamination being passed via animal food to animals and then onto humans. I think that the affected cattle should have prussian blue added to their diet to lower their cesium content.

If the cattle are put on a cleaner diet and/or fed prussian blue then it is possible to lower the cesium levels in the food which finally is put on a plate in front of a human.

Now that the rate at which the reactors emit cesium into the air has gone down greatly, I think it is time to start to clean the land which the cattle graze from. I think that where possible the land should be deeply ploughed to bury as much of the cesium as possible out of reach of the roots of the grass.

One possible method of dealing with the cesium problem would be for clean food (grain ?) to be supplied to cattle farms this year while the pastures are dug up to deal with the cesium problem. This change to grain might however push up the price of beef at the farms where the feed has been changed.

Food contamination

Dear Reader,

I want to tell you about some simple agricultural countermeasures, these are the ways in which farmers can change the way they behave to lower the level of the radioactive contamination in the food which they make. I imagine that a lot of farm workers in Japan are normal men and women who want to earn a honest living and that the events right now are a deep source of worry to them. They may be asking themselves if they are going to be forced to give up their way of life because of this accident.

I have read on the BBC that radioactive iodine has been found in food stuffs in Japan. This is not a good thing to have happened. The IAEA site stated that it was radioactive iodine. I have no idea how much radioactive iodine has appeared in the food or what the limit is in Japan for radioactivity in milk.

The iodine could pose some threat to health, the Japanese government have introduced rules controlling the sale of food from the affected area.

My advice now to food producers is not to panic, even if the food is not fit for human consumption now it may be possible to improve the radiological quality of the food in the following way. If the milk only contaminated with radioactive iodine then it could be converted into cheese. The cheese if it was stored for 80 days would then have 1000 times less radioactive iodine in it as a result of radioactive decay.

If you are a dairy farmer in an affected area my advice is ask the authorities in your area before you start cheese making. While it is one method the authority might rather a different method is used to protect the public’s health.

http://www.iaea.org/Publications/Magazines/Bulletin/Bull383/richards.html

If the accident gets worse and cesium is released then while cesium contamination is a more long lived problem. But there is a way out of the problem, Prussian Blue is a cheap non toxic chemical which can be fed to farmyard animals and humans. What it does is to increase the rate at which the radioactive cesium is lost from the animal or human. If you do want to use prussian blue then make sure that you get the right grade, the pigment grade used in paint is not as good as the special medical grade.

Another method for protecting dairy farming is to deeply plough the grass fields where the cows graze. This is a method which should not be done now while the nuclear accident is still occurring. After the nuclear accident is over and the cesium has stopped being deposited onto the land, then if you do choose to deeply plough then this should start.

The reason why deep ploughing works is this, the cesium is very immobile in most soils so it stays in the top layer where the roots of the grass is. If the soil is deeply ploughed up to mixed the different layers up then the majority of the cesium is then buried below the point to which the grass roots can grow. As a result because the grass roots are now in soil which has a lower average radioactive cesium content in terms of Bq per litre the grass which now grows on the land will be less radioactive.

If the grass is less radioactive then the cows which eat the grass will be less radioactive, and finally the milk and meat will be less radioactive.

In some cases a farmer might want to consider changing from growing food to growing a non food crop. This may help some farmers to containue to earn a living.