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#AESRC2014 Highlights

Well, AESRC is done for another year and with it my role as co-chair of the organizing committee! Thank goodness for that! Hopefully, I can finally get some actual thesis related work done in the coming months…and maybe get back to blogging a bit as well. However, as grateful as I am that AESRC is done, I have to say that it was a fantastic conference this year with a host of terrific talks from keynotes and grad students alike.

As I mentioned in my conference opening post AESRC is the only conference in Ontario, maybe Canada for all I know, that is organized by and for graduate students. The entire organizing committee is composed of graduate students and all of the talks, with the exception of keynotes, are given by graduate students. AESRC is meant to be a place where new and experienced grads alike can talk about their work in a less nerve-racking environment. We encourage in progress research or research that does not even have results yet. The idea is that every graduate student can feel comfortable, practice presenting to an educated audience and hopefully enjoy themselves and meet their colleagues from across the province.

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This AESRC was by far the most well attended in the past 10 years, with over 100 delegates attending from 8 different universities. The conference kicked off with the Icebreaker at a campus pub, where we all got meet each other or reconnect in many cases, while watching hockey and drinking beer. A nice relaxing end to the week and prelude to the science of the weekend. On a personal note, it is always worth attending the Icebreaker at every conference I have been to. More often than not there is free food and drink, but it is a great opportunity to meet new people, spot that keynote you want to talk with and introduce yourself. I try to make of point of meeting at least one new person at every Icebreaker I go to.

Saturday started with some great talk on Environmental Geoscience (my session) and Sedimentology and Petroleum Geology. We had two keynote speakers on Saturday: Paul Mackay from the Canadian Society of Petroleum Geologists and Dr. Jack Cornett from uOttawa. The video of Jack’s talk is below.

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To summarize, in case you didn’t watch the entire video, Jack discusses the incredible range of radionuclides that are found naturally occurring on Earth and the vast range of geologic problems these nuclides can be applied to. He also talks about how we can use accelerator mass spectrometry to measure these radionuclides at incredibly low levels, which is how we are able to apply them to geologic questions. To illustrate this point Jack discussed the case study of chlorine-36 in the Cigar Lake uranium mine in Saskatchewan, Canada.

Saturday concluded with a fantastic dinner at the nearby National Arts Centre and another terrific keynote by Dr. Becky Rogala on the challenges of extracting bitumen from the oil sands and the importance of having an accurate understanding of the sedimentology to ensure maximum efficiency of SAGD recovery. There was also quite a bit of beer.

Sunday started nice and early with the Geophysics session as well as the Paleontology and Tectonics sessions as well. Our keynote for the geophysics session was Dr. Glenn Milne from uOttawa, who was an author on the most recent IPCC report and is an expert on sea level change.

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We also had another great keynote from uOttawa in the tectonics session in Dr. Jon O’Neil. The video of his talk on the oldest rocks on Earth (4.4 billion years old) is coming soon! That pretty much wraps up AESRC2014! It was a great weekend, there was lots of great science and I am really glad its over. I likely won’t be around for next year’s AESRC at Queens University (fingers crossed), however, I am sure it will be great.

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Yours truly giving his talk on iodine-129 fallout from Fukushima. (Photo: Viktor Terlaky)

 

 

 

The Most Epic Unboxing Ever

The Most Epic Unboxing Ever

There is a strange phenomenon on the internet called unboxing. Unboxing is when a person receives a new package of something and takes a video or pictures of the process of opening it for the first time and posts it online.  Mostly, from what I can see, people “unbox” electronics or hockey cards or things of that nature. However, what I have today could be called the granddaddy of all unboxings; I have a series of photos of the unboxing and, initial stages of set-up of the University of Ottawa’s new, 3 million volt, accelerator mass spectrometer (AMS), which cost 5 million dollars. This takes opening your new laptop or that Sidney Crosby rookie card to a whole new level!!! The AMS will be housed in uOttawa’s new Advanced Research Complex.

The accelerator portion in its shipping container being transferred into our new building. (Photo: Dr. Liam Kieser)

The accelerator portion in its shipping container being transferred into our new building. (Photo: Dr. Liam Kieser)

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Easy does it. Now pivot!!! (Photo: Dr. Liam Kieser

Since I am showing pictures of this incredible piece of equipment being installed I’ll explain a bit about what it is an how it is used as well. I use the AMS in my own work to analyze iodine-129, chlorine-36 and once or twice carbon-14. In short, tools that can be used for groundwater dating. However, the AMS is capable of analyzing for a huge range of isotopes and this allows its use a wide variety of disciplines from health science to homeland security.

The AMS works on the same principles and a regular mass spectrometer, but it has a few key differences that make it extremely powerful.

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Lots of boxes to open. (Photo: Dr. Liam Kieser)

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Once the boxes have been unloaded the building begins. It is like building an IKEA desk, but somehow more… (Photo: Dr. Liam Kieser)

The process of AMS analysis begins with the preparation of the samples, which involves large amounts of lab time in extremely clean conditions. Contamination of samples with unwanted isotopes is a real problem in AMS so great care has to be taken to prepare good samples. The sample is then mixed with niobium powder and pressed into a steel cartridge. The cartridge then gets loaded into the ion source where cesium ions get fired at the sample like shooting a gun. The Cs ions physically break bits of the sample off the cartridge and these get negatively ionized and accelerated out of the ion source towards the first magnet. 

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Xiao-lei carefully taking the glass rings that are in the accelerator. These are to kill any free electrons that could escape from the stripper canal as well as keep the ions on a stable flight path. X-rays charged to 3 million volts are very bad! (Photo: Dr. Liam Kieser)

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The glass rings all put together with the stripper canal in the centre. The stripper canal is where electron get stripped off the negative ions turning them into positive ions as well as keeping the ions on a straight and even flight path. (Photo: Dr. Liam Kieser)

This is what the ion source looks like. Up to 200 samples sit in the big wheel waiting their turn. The AMS control room is those windows in the background.

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Our fancy new SO-110 ion source. (Photo: Matt Herod)

Once the samples leave the ion source they are accelerated to the first bending magnet which can bend an incredible range of masses. From tritium to plutonium tri-fluoride.

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The first magnet looking towards the accelerator. (Photo: Matt Herod)

The next step is firing the ion into the particle accelerator that carries a charge of 3 million volts! Inside the accelerator is a passage called a stripper canal that pulls electrons off the ions turning them from negative into positive ions. The reason for this is that this allows us to get rid of interferences that normal mass spectrometers face. For example, chlorine-36 has an interference with sulphur-36 making it impossible to analyse using normal mass specs. Actually, our AMS has another modification that makes 36Cl analysis possible on a 3MV machine, which is generally considered too small for this isotope. Usually, 36Cl needs a much larger accelerator however, our isobar separator for anions (ISA) allows this. Once the ion leaves the stripper canal it is accelerated at very great speed into the next magnet.

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Dunh, dunh, dunh. This is the A in AMS! (Photo: Matt Herod)

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This is the biggest magnet I have ever seen!! It is over 3m long and weighs 18 tonnes! This is why the room needs an overhead crane. (Photo: Matt Herod)

Once the ions are redirected and isotopes are further separated by the magnet they are ready to be analyzed in either the Faraday cups for the common isotopes or the gas ionization detector for rare isotopes.

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Me, touching the Faraday cups. (Photo: Laurianne Bouchard)

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The gas ionization detector. This bad boy literally counts atoms as they come around yet another magnet and through a silicon nitride window. Once they enter the detector which is filled with gas they ionize it which leads to pulses of electricity that are counted. This is the end of the AMS!!! (Photo: Matt Herod)

Once the atoms are counted in the gas ionization detector their trip around the AMS is over! It is quite a journey and full of positives and negatives (haha, a little pun there). Seriously, though this gigantic instrument is used to quantify the smallest of small quantities and can very literally count atoms. The AMS has a massive number of possible uses and I’ll likely be posting about these as this new facility starts to ramp up in the next few months. In addition to the AMS we also have an SEM, microprobe, stable isotope equipment, two noble gas mass spectrometers, ICP-MS, LA-ICP-MS, ICP-AES and a host of other MS’s as well. There will be very few types of isotopes that we cannot analyze for and this facility will be one of the best in the world for this type of geological research. Stay tuned for further developments as we start to move in soon!

Cheers,

Matt

AW# 60 – Radioactivity: What’s the use?

AW# 60 – Radioactivity: What’s the use?

I am very excited to be hosting the 60th Accretionary Wedge at GeoSphere! Sorry my own contribution is so slow in coming…it has been a busy month PhD wise. In fact, I expect it will be a busy year PhD wise since I am hoping to submit in the Fall of 2014 and I have got a LOT of writing to do. Anyway, in the call for posts I said:

For this wedge the topic will be momentous discoveries in geology or its sub-disciplines that you feel have altered or shaped our understanding of how the Earth works, or opened new doors into research that had never been considered before. The discovery you choose does not have to be universally recognized as momentous but should be in your opinion. It could be something that we take for granted every day, but is in actuality part of the underpinnings of our science.

The discovery I am going to discuss is one that a wide variety of different geoscience disciplines uses every day and one that is particularly near and dear to my heart, since my PhD. is about an application of this discovery: radioactivity and radioactive isotopes. The consequences of the discovery of radioactivity have been extremely far reaching in many fields, particularly the geosciences. For this post I am not going to describe what radioactivity is, but rather some of the fantastic applications and subsequent discoveries that have hinged on the initial discovery of radioactivity and radioactive elements. There are a lot, so for the ones I don’t talk about I’d love to see comments on.

Cherrenekoff radiation is a pretty way to demonstrate radiation. (Photo: Matt Herod)

Cherenkov radiation is a pretty way to demonstrate radioactivity. (Photo: Matt Herod)

The Earth is constantly in a state of change. The process that move and shape the Earth are doing so in front of our very eyes. If only we had a means to see it happen….oh wait. Radioactive isotopes can often be used as tracers of natural processes. Sometimes the isotopes are naturally occurring and sometimes they are added through human activities. Either way, we can use them to uncover Earth’s mysteries.

The first thing that everyone thinks about when discussing application of radioisotopes in geology is radioactive dating.  The basic principle of radioactive dating was discovered by Ernest Rutherford in 1905 and states that if we know the half life and the concentration of the decay product we can use that information to calculate how much of the parent isotope there was and then how old the material the daughter product was measured in is. This basic idea has spawned a wide variety of dating techniques using different isotopes with a range of half lives from very short to very, very long. Radioactive dating is the reason we know old the Earth is, when the dinosaurs lived and died, when ancient volcanoes erupted, what sort of tectonics took place on the early Earth, how long ago our ancestors lived and so much more. The problems to which radioactive dating can be applied are limited by the presence of a usable isotope rather than running out of questions. Indeed, there will always be more things to date using the wide varity of isotopes available. It is possible to date recent things using Carbon 14 or Tritium (Hydrogen), which both have fairly short half lives. The furthest back that I have seen dating methods go is for rocks from the Isua Greenstone belt, which were dated at 4.28 billion years using the samarium-neodymium isotope system (Note: This work was done by J. O’Neil a new prof at uOttawa). Either way, if it is new or old radioisotopes can date it.

Occasionally pollution can be useful. It goes without saying that pollution is bad. However, on occasion its presence can be used to solve scientific problems when nature does not provide a means to do so. One instance of this is using radioactive releases from nuclear fuel reprocessing to trace ocean currents in the North Atlantic ocean. The releases themselves are extremely low level, and are not dangerous to humans or the ecosystem in any way. However, they are easily detectable and therefore can be used. Fuel reprocessing releases a lot of iodine-129 and cesium-137, as well as some other isotopes. These isotopes are then released into the Atlantic ocean and circulate with currents. Using these isotopes to trace the depth profile of currents, where they move and how long it takes for them to circulate is a burgeoning field in oceanography research.

Not all radiotracers are pollution though. Ideally, we can use naturally produced radiotracers to tell us about the environment. For example, contaminated places aside, radon is produced by the decay of naturally occurring uranium-238. It can then be incorporated into groundwater or pass through the soil as a gas. One immediately obvious use of radon is in uranium exploration. If there is a higher concentration of uranium in the rocks more radon will be produced. Therefore, if soil gas sampling for uranium exploration finds elevated radon that could be an indication of a possible economic uranium enrichment. Another way of using radon is something that I have some personal experience with: tracing groundwater discharge into surface water. When groundwater comes in contact with uranium minerals it dissolves some of them or dissolves the radon gas directly. If this groundwater then discharges into a lake or a river for example we might expect to find higher radon at the discharge point. I did a lot of sampling for this one summer during my undergrad and we did find a few places where the radon concentrations were higher than background, which is an indication of groundwater discharge. We also canoed down an entire river with the instrument dangling out the side, sampling as we went. No radon was found in that instance, but it was really fun.

Radioactivity is also useful in the lab. In fact, I use the radioisotope iodine-125 almost every day as a tracer of a lab method I have been developing for the extraction of iodine-129 and 127 from organic materials. The process that I am using to extract iodine is combustion under a pure oxygen atmosphere and then trapping the iodine in a bubbler containing a hydroxide solution. However, it is often difficult to know if the extraction has been successful or not, particularly if I am playing with flow rates or temperature settings. The sample may be burnt, but did I capture the iodine? In order to test whether or not my combustion has been successful I add some iodine-125 to the sample before it is combusted. Then all I have to do at the end is see if my 125I, which is tested via gamma counting, is in my trap solution and I know if I got the other isotopes as well, because they all behave the same chemically. This line can also be used to extract other radiohalides from organic materials. In fact, as I type this a visitor from the Lamont-Doherty Earth Observatory is extracting chlorine-36 from vegetation and rat poop.

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My iodine combustion line. The paper describing the work done on this will be submitted very soon! (Photo: Matt Herod)

Cosmogenic isotopes are one of the most useful tools in the surficial geochemists arsenal and their use is very wide ranging. I wrote a very long post about cosmic rays and cosmogenic isotopes previously. See here. The big uses that I discussed for cosmogenics, which are radioisotopes that are produced when cosmic rays collide with particles in the atmosphere or directly with minerals to produce other isotopes that can then be used for a wide range of dating applications.

Exposure age dating is one of the principle uses of cosmogenic isotopes and several different ones have been employed to this end. Exposure age dating is when we use cosmogenic isotopes to date how long something has been exposed to secondary cosmic rays at the Earth’s surface. For example, a rock at the toe of a glacier may have just been exposed to cosmic rays a year ago and its exposure age date will tell us this. Another rock, 20 metres further from the glacier toe may have been exposed 5 years ago and this difference will be recorded. Basically, the clock starts ticking once cosmic rays are able to reach the rock or bone, or whatever material is being dated.

Carbon 14 is unquestionably the most used of any of the cosmogenic isotopes. 14C is produced primarily when neutrons collide with nitrogen in the atmosphere replacing a proton in the nitrogen nucleus and transforming it into carbon-14, although atmospheric nuclear weapons testing also produced a substantial amount of 14C. The primary use of 14C, or radiocarbon, is radiocarbon dating. Once radiocarbon is produced it enters the global carbon cycle and disperses throughout the environment. Since it is part of the carbon cycle it becomes incorporated into all living things, including people and animals. 14C continues to enter our bodies while we are alive. Once we die, there is no further addition of 14C and therefore, the clock starts ticking on its use as a dating tool. 14C has a 5,730 year half life and is therefore useful as a dating tool for biological materials up to ~45,000 years ago.

Sick of reading about how useful radioactivity is in geology? I don’t blame you. However, what I have presented here is just the tip of a very large iceberg. Other examples, include helium-tritium dating, helium ratios, tritium in natural systems, gamma logs for oil and gas exploration, and much, much more. It is all thanks to that very momentous discovery in 1896 by Henri Becquerel. If you have examples of the use of radioisotopes or radioactivity in geology please comment about it below.

The summary post for September’s AW will be up in a few days. So if you have a late submission you can still get it in.

Matt

The Mysteries of Maqarin

We all know that cement is a man-made substance and therefore cement is always synthetic right? Wrong!

In the unusual case of Maqarin, Jordan the stars aligned to produce natural cement and many of the “synthetic” minerals found therein. The Maqarin site has been the subject of an intense geological investigation by a consortium of over 100 researchers for years in an attempt to try and understand this system and its implications. A fairly good overview is available here.  Maqarin is located in  north-east Jordan, near the border with Syria, in the river valley of the Yarmouk River. The valley is deeply incised allowing a good view of the stratigraphy. There are also several springs coming out of the sides of the valley wall and it is these and their relationship to the unusual geology that make Maqarin so interesting.

A map of Jordan. The location of Maqarin is starred.

A map of Jordan. The location of Maqarin is starred. (Source)

Geologic History

The geologic history of the Maqarin site is very interesting and in many ways unique. Indeed, it was a unique combination of geology and geological events that led to its formation.

1. During the Cretaceous bituminous marls are formed. Basically, rocks that are full of bitumen and calcium carbonate. This rock has up to 20% organic matter! Bitumen forms when organic matter is heated during lithification and is similar to oil. It will burn. The marl is a white, chalky mineral primarily made of CaCO3. There is also about 10% sulphate, which becomes important later on in the geologic history.

2. Overlying the bituminous marls are chalky limestones that were deposited in the Tertiary.

3. The upper unit is basalt, which was deposited during the Pleistocene.

4. The bituminous marl underwent “pyro-metamorphism”. Basically, the rocks were heated to a point where the carbonate rocks cooked and formed high temperature cement minerals such as portlandite, ettringite and thaumasite. The heating though was not due to burial but actually from spontaneous combustion of the bitumen (Khoury et. al., 1992). The presence of sulphate allowed these minerals to form and better simulated a modern cement environment. When the marl, which is CaCO3, is combusted CaO or lime is formed. Then the infiltrating groundwater allows portlandite to form, which then reacted with the suplhates and silicates present to form the other cement minerals.

5. The rocks in the area are all highly fractured allowing water to easily seep through the site. This has led to weathering of the cements. The water seeping through the sites discharges near by and has a pH of 13!!!! The water that seeps through the “cement zone” of the Maqarin site picks up all sorts of dissolved ions and minerals. Remember that heating carbonate + water gives Ca(OH)2. Therefore, there is a huge supply of hydroxide available to raise the pH.

These 5 steps created the Maqarin analogue site as we see it now. Everything had to be perfect for it’s formation to happen:  the rocks had to have the right chemistry, pyro-metamorphism had to occur and, the hydrogeology had to allow water to infiltrate and react with the rocks to produce the hyperalkaline springs. See the references below for a more detailed description of the geology and mineralogy of Maqarin.

An image of the Yarmouk River Valley from the Jordan Times. Notice the bedded cliffs along the river. At Maqarin it is these cliffs that have the springs in them. In the distace you can also make out the sraker, overlying basalt. (Source)

Some Geochemistry

I mentioned the “hyper-alkaline springs” above. These springs are super interesting to geochemists, since there not very many places on Earth where we can find springs of highly elevated pH. Indeed, it is much more common to find acidic springs than alkaline ones. However, the springs of Maqarin have exceptionally high pH’s. Why?

The alkaline springs, which flow out of the hillsides at Maqarin, formed due to the unique combination of the hydrogeology, structural geology and mineralogy of the site. As the water infiltrates through fractures in the rock it intially dissolves NaOH and KOH followed by Ca(OH)2, which is the cement mineral portlandite. All of the OH ions that enter solution contribute to the raising of the pH to around 12.5. This now caustic water is then able to react with other minerals and pick up a lot of metals such as uranium, chromium, vanadium and other exotic elements that would usually be insoluble and hence difficult to transport (Khoury et. al, 1992).

The stable isotopes also tell and interesting story about the origins of the water and its pathways at Maqarin. In arid climates, such as Jordan, the groundwater often reflects evaporation that took place either before or during recharge.  The waters of Maqarin plot below the local meteoric water line, which is indeed indicative of evaporation before or during recharge of the groundwater. However, there is more to these waters than just evaporation. In fact, the hydration of the cement minerals, such as portlandite, can cause an 18O enrichment, which can also be seen in the Maqarin groundwaters, although it is difficult to differentiate this effect from that of evaporation, which also produces the same trend (Khoury et. al. 1992).

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Plot of 18O vs 2H in the hyperalkaline springs of Maqarin, Jordan. The local meteoric water line (Irbid) and the eastern Mediterranean meteoric water line are both shown. Modified from Khoury et. al., 1992.

Why study Maqarin?

We need to understand how cement will behave over long time scales because in most nuclear waste storage or carbon sequestration designs one of the primary barriers between radionuclides/CO2 and the environment are the engineered barriers, many of which are made of cement. In fact, in a repository setting cement is everywhere. It will be used to contain the waste itself, plug up fractures, reinforce structures, and eventually to seal the whole place up. Sealing the place up water-tight (hopefully radio-nuclide tight also) is great, but what happens to the seals when they are subjected to a million years of groundwater flow? Well, the modelling suggests that…. Wait, did I just say modelling? You mean we rely on computer generated geochemical models to tell us what might happen in a number of scenarios? We don’t know exactly what will happen to all that cement that is plugging up a waste site?

An artists depiction of a deep geologic repository for low and intermediate level radioactive waste. (Source)

Enter Maqarin. Maqarin is such an interesting place because “cement” occurs naturally here and it provides a rare opportunity for researchers to actually see how cement and the minerals composing it behave over long time scales when subjected to weathering processes. Therefore, the site can be considered an analogue for the future behaviour of cement in the environment. Indeed, the hydration process that occurs in Maqarin when the groundwater reacts with NaOH, KOH and Ca(OH)2 is exactly what will happen when “man-made” cement is exposed to groundwater. Understanding the geochemistry and hydrogeology of a site like Maqarin gives real-world insights into the outcome of our modelling and we can take the data collected at places like Maqarin and compare them to our model results to verify its accuracy. Furthermore, using observations and empirical data to make conclusions about the future of waste repositories adds a whole new level of confidence in their design or identifies possible weaknesses.

In summary, since radioactive waste storage facilities, which are designed to have million year lifespans, are made of cement it is crucial that we know what will happen to them over long time periods. However, the problem is that modern cement is just that: modern. Therefore, we don’t really know how it will behave in certain environments or when conditions change, or during an ice age, etc, etc. In order to solve this problem we must turn to the next best thing, which is a natural site, such as Maqarin, that mimics the environmental conditions we are looking for and hopefully it can answer some of these questions. Hence, the beauty of the natural analogue.

Thanks for reading,

Matt

References

Khoury, H.N., Salameh, E., Abdul-Jaber, Q., 1985. Characteristics of an Unusual Highly Alkaline Water from the Maqarin Area, Northern Jordan. Journal of Hydrology 81, 79–91.

Khoury, H.N., Salameh, E., Clark, I.D., Fritz, P., Bajjali, W., Milodowski, a. E., Cave, M.R., Alexander, W.R., 1992. A natural analogue of high pH cement pore waters from the Maqarin area of northern Jordan. I: introduction to the site. Journal of Geochemical Exploration 46, 117–132.