U of T’s Scarborough campus is home to the only fully functional nuclear magnetic resonance (NMR) facility in Canada that is devoted to answering environmental questions.
The technology used in NMR is relatively common. “It’s used a lot in chemistry, biochemistry and medicine, but not much in environmental science, so that’s why our lab is kind of novel,” explains Dr. Myrna Simpson, director of the Environmental NMR lab.
Dr. Simpson examines carbon-containing matter, including soils, sediments, air and water, elements of the environment that are often treated as indecipherable because they are so complex. “The soil contains inputs from plants, and plants are made up of carbohydrates, waxes, proteins [and other materials]. You have all these different plants adding stuff to the soil, then you’ve got animals adding stuff to the soil, and then you’ve got people adding stuff to the soil. You have to try and figure out what the soil is made of, and how it all got there.”
The most important environmental concern Simpson looks at is climate change and the how soil composition will be altered as a result. Soil can be divided into labile components, which microorganisms eat rapidly, and recalcitrant components, which they will not eat. NMR has been used to measure the ratio of labile versus recalcitrant carbon, and the results do not look good.
“We’ve actually found that there isn’t very much recalcitrant at all; there’s mostly labile. The implication is that with global warming, if the climate warms up and we have large reserves of labile carbon, it’s going to get eaten rapidly, and more carbon dioxide is going to end up in the air than they’re predicting,” said Simpson. The question the lab hopes to answer is why microorganisms have yet to eat all the labile carbon.
The key to studying carbon containing matter lies at the interface: the boundary between two layers. “That’s actually an area not many people look at, but that’s where all the action happens. For instance, if a contaminant enters the water, it’s going to happen at the solid-water interface.”
A special NMR technique is being used to look at the interaction between carbon-containing materials and the clay minerals they often coat. One possible reason why labile carbon might still be in the soil is that it is bound to clay, so organisms can’t pull it off and eat it. Understanding this problem might lead to a way to help combat climate change.
The lab is also looking at what happens when herbicides and pesticides interact with soil components. “A study came out a few years ago that found low levels of antibiotics in 170 lakes and streams in the US. Our clean-up technology, our water treatment plants, aren’t targeting these things,” said Simpson.
NMR analysis, by studying soil composition, can answer questions related to the movement and destination of contaminants. An understanding of soil is also being employed in a study aimed at developing green crop technology. The goals include knowing which crops are better for increasing the amount of carbon in our soil; which crops are better for maintaining sustainable soil quality over the next 50 years; and, especially, what will happen to carbon in the soil if we experience global warming.
“There hasn’t been enough molecular level type studies using NMR and other techniques that can definitely give us give us yes or no answers. Most studies treat soil as [too complex to piece apart]; they don’t look at the properties and the mechanisms, and that’s what we need to figure out before we can make decisions.”
Nuclear magnetic resonance (NMR) imaging relies on a similar but scaled down version of magnetic resonance imaging (MRI), a process used to study brain activity. While MRI is used to look at the entire human body, NMR looks at only one or two molecules at a time. Both MRI and NMR work by sending a pulse of energy through a sample, and then determining the amount of energy that the sample absorbs. Some mathematical calculations can help you figure out what sorts of atoms are present and how they are bonded to each other.
