The University of Arkansas Stable Isotope Lab, or UASIL, was established in 2000 to provide isotope analysis to researchers at the university. Erik Pollock, who came to the U of A from Maine in 2002 to earn a master’s degree in geosciences, became the lab manager in 2007. His research was in low temperature water isotope geology and geochemistry. Under his direction, UASIL continued to acquire instrumentation that was not otherwise available in Arkansas, until it made sense to spin off an additional lab under Pollock’s direction: the Trace Element and Radiogenic Isotope Lab, or TRAIL. In the following conversation Pollock discusses the purpose and mission of these labs.

Q: Why was the Stable Isotope Lab established?

A: Stable isotope measurements are fairly unique in the analytical world. Most analytical methods ignore that isotope ratios differ from sample to sample. The need for a lab that can analyze those small differences is fairly specific. The laboratory was set up in 2000 to answer questions largely for a snake physiologist and a soil scientist who were interested not only in background isotope ratio changes, but also in adding labeled substrates to their systems to determine other properties further down the road. At the time there was no stable isotope instrumentation in the state of Arkansas. The Stable Isotope Lab would be the center for the state for these specific kinds of measurements. That largely holds true, except for about two other systems that I know of that can do light isotope measurements in the state.

Q: Okay. Let’s take the snake researcher. How do stable isotopes fit in with what he was trying to learn about snakes?

A: Snakes have really interesting physiology in that they can fast for long periods of time. Fasting is not being quite dead so there’s still physiological things that happen. They're still using up energy stores and they're still using up water. As the snake hibernates, there’s still physiological activity and as it goes through this activity, it uses up water which changes the ratio of the remaining water. For the hydrogen in particular. As it goes through energy and metabolism, it uses up some of the oxygen in the water to do this, so those activities are fractionating in their nature. That is, they change the ratio as they go from one phase to the other, and so over time we can begin to look at how these processes are happening by measuring the changes in the isotope ratio [of hydrogen and oxygen] over the fasting time.

Headspace purging table for nitrate isotope analysis.

Q: What departments are most likely to use the Stable Isotope lab?

A: Currently, biology and geology are two major users, with anthropology probably third in line. Other departments sort of come and go less frequently depending on their project load. Poultry science, food science, health, human performance and recreation, crop soils and environmental science are some of the others.

Q: Is there a standard type of analysis that you are typically asked to do?

A: So probably the big three analyses we do would be looking at hydrogen and oxygen isotopes in waters. And those are both natural waters and physiological waters. The next would be doing carbon and nitrogen analysis in solids. This is often plant material like microbial biomass or soils. And then the third one would be doing carbonates where we can get the carbon and oxygen isotope simultaneously out of carbonates.

Q: How many samples do you analyze in a typical year?

A: In a year we’ll do something like 40,000 analyses. Some projects may require hundreds or thousands of samples over a period of years.

Q: So around 2017 you spun off a second lab, the Trace Element and Radiogenic Lab. Why?

The plasma of an inductively coupled plasma mass spectrometer

A: That facility came out of a hole in the analytical capabilities at the university. We had the stable isotope analysis fairly well covered for our users. We had an organic mass spec[trometry] center that was doing lots of small molecules and proteins. But we really had no general user facility that could analyze metals at a trace level. That was the reason for starting that.

Q: For the lay person, what is the difference between an isotope and a trace element?

A: So if we think about isotopes and we think about carbon, you and I are about 50% carbon. It’s a macro amount of carbon and you have an isotope ratio of that. And that ratio is independent of the amount of carbon you have.

When we think about trace elements, we're thinking about things that are very minor constituents within the system. The upper boundary might be parts per thousand, but more typically we're talking about a parts per million and we're regularly analyzing parts per billion and occasionally even below that. And so that's sort of the span of trace elements. There’s some crossover in who uses the labs, but TRAIL has much higher engineering and chemistry use.

Q: Can you give us an example of a research project this might be used in support of?

A: So I've been I've been working with a colleague up in Maine and we've been trying to assess the wild turtle trafficking problem, which I didn't know about until I met with him. What happens is that these turtles are stolen out of the woods and sold as pets, which depletes the natural population. Some of these are threatened  woodland turtles, so we've developed a way to take a small piece of the turtle claw, bring it down to the trace element lab, analyze it for a handful of different trace elements, and compare that to captive turtles versus wild turtles. And we've found that we can differentiate with 99% certainty whether the turtle that you gave us was caught in the wild and brought into captivity or whether it was raised in captivity just with the next elements.

Q: So there are a couple specific trace elements you’re looking for?

A: In that case there turns out to be a handful of sensitive ones. Manganese is one.
Strontium is another one. It was fun because we actually started doing like 30 elements, you know, just a fishing trip. And then as we built the database, we found there were certain elements that were much more indicative and some were just noise. The wild turtles have a tendency to have increased trace element concentrations in them. We’re still sort of working on the physiology of that.

Q: TRAIL recently got a million-dollar piece of equipment through the NSF. What will it allow you to do?

A: In the Stable Isotope Lab we really focus on carbon, nitrogen, oxygen and hydrogen and those ratios, which are prominent in living and critical zone systems. But there's a whole periodic table of isotopes, and what this new system will allow us to do is work on non-traditional and heavy isotope systems. We've done some work with lead, some with neodymium, some with strontium, but there's a wide open field there that our previous instrumentation couldn't really access. And so we'll be able to open up that box of potential element isotopic tools that we couldn't before. Additionally, we'll be able to interface this with our laser ablation system, which we couldn't do before. So we could potentially do in situ isotope heavy isotope analysis of solids, perhaps turtle claws. Lastly, our hope to do something called laser ablation split stream, which is we take our laser, we ablate a bit of material, and we split it into two different sample streams. One will go to our new multi-collector and we'll get heavy isotope information from that. The other will go to our existing ICPMs and we'll get trace elements from that. So simultaneously getting isotopes and trace elements out of a single spot.

Q: What is something people should know about both labs?

A: I think the important thing is to realize that the lab is there as a service to the research community here at U of A, the state and the region. It exists not to give me a job, but rather for me and the facility to help. Researchers across the spectrum — and I mean researchers from undergrad to graduate to faculty level — all interact in our lab, and the reason we do these things is to provide for them.