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A year ago, around this time, I posted an entry on this blog explaining why I was on my way to start a fieldwork trip to the Chernobyl Exclusion Zone, in Ukraine, in search of amphibians (“Why I am going to Chernobyl?”). Now, I am ready to get back to Chernobyl to extend the work done last year examining the effects that living under chronic low dose radiation has on amphibians. I will arrive to Ukraine on Sunday 7th May, for more than a week of intensive field and lab work in the Zone.



The Chernobyl Exclusion Zone includes some of the most radioactively contaminated areas in the world as a consequence of the accident occurred in the reactor number 4 of the Chernobyl Nuclear Power Plant on the 26 April 1986. It is estimated that the accident caused the release of ca. 5200 PBq of radioactive material to the atmosphere. In comparison, this is equivalent to about 400 Hiroshima atomic bombs, whereas <800 PBq were released in the 2011 Fukushima accident in Japan.


However, after the acute phase of the accident, and all the severe impact it caused on humans and the environment, radiation levels started to decay. For example, one of the most dangerous products of radioactive fission, Iodine-131, which accounted for about half of the radionuclides dispersed after the Chernobyl accident, has a half-life of ca. 8 days. For putting another example, shortly after the explosion, radiation levels around the reactor peaked at 300 Sv/hour (300,000,000 microSv/hour), whereas in the same area radiation levels are now ❤ microSv/hour. Furthermore, the differences in wind direction, precipitation, etc. during the atmospheric releases created a pattern of uneven, patchy, distribution of radioactive contamination inside the Zone.


Currently, one of the crucial questions in field radioecology is trying to understand what are the long term effects of radiation for organisms living in low-dose radioactive contaminated areas? Visiting the Zone, it’s obvious that the area is full of wildlife (see last year’s post “Chernobyl recap: the wildlife”), although many studies have also reported damaging effects in animals living inside the Zone (see last year opening post “Why I am going to Chernobyl?”). The main goal of our project is, thus, to evaluate the impact that living in areas with radioactive contamination has on the genetics, physiology and morphology of wildlife, paying special attention to detecting patterns of adaptive responses to radiation. And for this, we use amphibians as study models, in particular treefrogs (genus Hyla).


Last year, we managed to collect frogs in six localities distributed across a gradient of radioactive contamination ranging from >1000 kBq/m2 Cs-137 and >8000 kBq/m2 Sr-90 in the most contaminated area (just 1km from the reactor), to 70 kBq/m2 Cs-137 and 23 kBq/m2 in the non-contaminated area (i.e. background radiation levels). The main goal for this year is extending the sampling to more localities across the gradient of radioactive contamination inside the Chernobyl Exclusion Zone, as well as collecting an additional bunch of material for new analyses on coloration, genomics and transcriptomics. The big objective is to extend this sampling to a total of 15 localities, including a few ones from the higher levels of radioactive contamination.

The will be a few things different from last year, of course.

One of the things that will change with respect to last year is that we will adopt the new taxonomic developments, and no longer consider that we work in Chernobyl with the European tree frog (Hyla arborea), but with the Eastern tree frog (Hyla orientalis, see Dufresnes et al. 2016). Not a big change in our approach, mainly a change of names. But, you need to properly address these changes.


Another big change is that this year I will be joined in the field by my colleague, and friend, Pablo Burraco from the Doñana Biological Station (EBD-CSIC, Spain). I will miss the great help, and fun, provided last year by Nele Horemans and Robin Nauts (Belgian Nuclear Research Centre, SCK-CEN) during nights in which they become top-level frog-catchers. However, having extra hands in the lab for processing all the frogs, and from a well-trained amphibian ecologist, will be a huge improvement. And the fun is also more than guaranteed…


Something different also is that this year I will fly with a dry shipper in order to (try to) fly back to Sweden carrying all the frozen samples myself. Last year we sent one through a cargo company only to face all the unimaginable bureaucratic barriers for getting it into Ukraine, and out of Ukraine, which resulted in getting the samples five months later… In short, a dry shipper is a container with a matrix that absorbs liquid nitrogen, and maintains your samples deep frozen without the need to have liquid in the container. So you can just close it properly, and fly with it on a plane. Or at least that’s the theory. Let’s see if there is no problem with the customs…

But something that will not change this year is that we will be in the Zone together with our colleague Sergey Gaschack, from the International Radioecology Laboratory, Chornobyl Centre, Ukraine. Sergey has been working there since the year of the accident, in different tasks around radiation, and in particular with the wildlife of the Zone. Moving around the Zone during the night with him on the driving seat was one of the most amazing experiences from last year trip. Impossible to have anyone with more knowledge about the zone in our team!!


And, same as last year, we will have another part of the team waiting for our samples in the labs of the French Institute for Radiological Protection and Nuclear Safety (IRSN) in Cadarache. Jean Marc Bonzom, Olivier Armant, Chirstelle Adam-Guillermin and Karine Beaugelin are also an essential part of this project, both for the molecular and the dose rate analyses. Also Clare Bradshaw will keep on helping with many different aspects from Stockholm University. I have to say that it’s such a pleasure to form part of this amazing, international, multidisciplinary, team!!

The work will be conducted as one of the last actions of the European Union FP7 funded project COMET (COordination and iMplementation of a pan-European instrumenT for radioecology), but also thanks to the financial support of the Swedish Radiation Safety Authority (SSM) to the project “Effects of long-term exposure to ionizing radiation on Chernobyl’s treefrogs”. Thanks!!

Last year I was able to write a daily entry on this blog from the Zone, which was a great experience (thanks to all the people that read these entries!!). That was thanks to one of the totally unexpected things that I discover once there: it was possible to have great wifi at our hotel in Chernobyl!! This year the hotel is fully booked by tourists coming to the Zone to see the reactor, the abandoned city of Prypiat and the derelict villages. So, we will need to stay at a different place, and I am not sure if we are going to have wifi there. Anyway, my plan is writing again a daily entry describing how is it to work in the Chernobyl Exclusion Zone, the animals and landscapes we encounter, and our fate on the pursue of amphibians there. If possible, I will send these entries from the field, if not I will publish them once back to “wifi land”. You will be able to follow also some updates in Twitter using #ChernobylFrogs17, on my account @GOrizaola or on Pablo’s @pabloburraco.

It’s time now for me to finish with some deadlines, and to organize all the material needed for the fieldwork (it’s crazy when you have to carry everything with you, from vials, to gloves, to scissors…), and to develop a clear plan for sampling procedures in the lab (too many different things to sample at once).

Weather forecast looks just perfect for this week in the Zone (sunny and around 20 °C), but a bit colder and with more chances of rain for the start of our fieldwork there, not good for treefrog males calling during the night. But let’s see…

Hopefully, next post will be already from Ukraine, from the Airport hotel, and with a dry shipper on my side… Fingers crossed.