Understanding how volatile organic compounds (VOCs) that originate from living organisms like trees and plants could influence climate change and air pollution is an important area of research. Recently I had the opportunity to sit down and talk with Alfred Mayhew, who is postdoctoral researcher in the Department of Atmospheric Sciences here at the U. Alfred did his earlier graduate and PHD work at the University of York in the UK.
Dr. Mayhew’s research is focused on the intersection between air quality and climate change, and the very complex chemical interactions between biogenic volatile organic compounds. By trying to better understand how certain interactions take place between compounds and how significant they are for understanding and forecasting air pollution and climate change, he hopes his work will provide direction and focus for future lab and field researchers, and policymakers interested in understanding the climate feedback between the biosphere, atmosphere, and anthropogenic emissions.
I have to say this was a fascinating, and times challenging topic for me to wrap my head around, and Aflie was very gracious and patient to help get me up to speed on his work. I hope you enjoy our conversation.
Listen to the Interview:
Transcript:
Ross Chambless
Well, Alfred Mayhew, so glad to have you here today to talk. I’ve been looking forward to this conversation.
Alfred Mayhew
Thank you for having me.
Ross Chambless
So, just to start off, can you just give us like a quick summary of your background and what has been your journey up to now, coming to the University of Utah to do your research?
Alfred Mayhew
Yeah. So, my background is really in chemistry. I did my undergraduate degree at the University of York in the UK in chemistry, and the University of York has quite a large atmospheric chemistry department. And so, this is researching the compounds in the atmosphere, how they interact with each other, primarily to form air pollution. Obviously, we’ll talk about climate links there as well. And throughout my undergraduate degree, I was kind of exposed to that sort of field on the periphery. And when it came time to choose a master’s project for my undergraduate, I decided that I was interested in the field of atmospheric chemistry, and I conducted that project and really enjoyed it.
And so, an opportunity came up for a Ph.D. And again, I took that opportunity. And throughout that PhD process I was then exposed to some more environmental science sorts of topics. And then when I was interested in doing more research and I was applying around for various postdoctoral fellowships, I had the opportunity to apply for this Wilkes fellowship and to sort of design my own project in collaboration with my current supervisor. So, that’s why I started to apply the atmospheric chemistry subject that I’ve been learning up until this point to, I guess, a more sort of climate angle. Although I do still research some air quality implications as well.
Ross Chambless
Interesting. So, as I understand your research interests, when you got your Ph.D., your research revolved around Isoprene. And so, take a moment to just to explain what Isoprene is, exactly.
Alfred Mayhew
So, isoprene is a small organic compound. It’s made of five carbon atoms. And so, it’s kind of a slightly obscure thing to research from that point of view. But the reason a lot of people are interested in isoprene in the atmospheric chemistry world is because it’s actually the most emitted non-methane volatile organic compound in the atmosphere. So, volatile organic compounds are these carbon-based compounds that exist all around us in the atmosphere, and isoprene is emitted in huge quantities. It’s actually what we call a biogenic VOC, which means it’s primarily emitted by living organisms. So, in the case of Isoprene, it’s trees. So, it’s slightly different from the vehicles people tend to think about in urban environments where you’re thinking about things emitted out of the back of cars or solvents spelt and things like that. But because it’s emitted by trees, it means it’s emitted in huge quantities all around the world.
And so, yeah, my research was really looking at…. oh, I guess the other thing to say about Isoprene is that it’s very reactive. So, for any chemists, it’s got two carbon double bonds, which means it very easily reacts with oxidants in the atmosphere. So, that’s another reason why people care, is because it is present in large amounts and it’s very reactive. So that in turn means it’s important for the chemistry of the atmosphere.
Ross Chambless
Yeah, so this has been great because it’s given me an opportunity to learn more about Isoprene. I understand that there are, like you said, there are natural sources of it and then there are sort of human contributions as far as just emissions and fossil fuel combustion and that kind of thing. Could we start with the human contribution of isoprene formation? What kinds of human activities can cause high levels of isoprene emissions into the air?
Alfred Mayhew
So, isoprene is overwhelmingly emitted by trees. So, anthropogenic human emissions of isoprene are very small, actually, there’s some small emissions from petrol I think is the main one. So, if you’re in very, very, very polluted urban environments, then that can become quite important. But normally people don’t consider manmade isoprene at all and the interesting aspect from my PhD is a lot of the pollutants that I was interested in that form from Isoprene are often formed more predominantly in urban impacted environments. So, this is where you have natural isoprene in the air, and then you have emissions of things like nitrogen oxides or sulfur from people. And those two interact to form pollutants. And normally they form higher levels of pollutants than if those anthropogenic emissions weren’t there in the first place. So, it’s this very complex system of things that already exist in the atmosphere and anthropogenic emissions of interacting.
Ross Chambless
Interesting. So, if I understand correctly, basically you might have natural sources like plants or trees that are largely responsible for isoprene and aerosols, and the question is how they interact with these other gas formations. Whether they might be creating secondary organic aerosols and whether or not this could create a sort of negative feedback as far as making things warmer than they would, or causing air pollution in certain environments? That’s the question?
Alfred Mayhew
So, this is where we get into like the link with climate and air quality. Yeah, the main focus of my previous research with isoprene, but also my current research now, is the formation of, like you say, secondary organic aerosols. This is particulate matter in the atmosphere. So, small particles are formed and they’re Secondary Organic Aerosol because they’re formed in the atmosphere, they’re not directly emitted. That would be primary, and they’re formed as a result of this chemistry that I’m interested in.
So, isoprene is emitted, it undergoes chemical reactions, and potentially forms some particles. Now those particles are interesting from an air quality point of view because exposure to particulate matter is a bad thing. And so, there’s limits for how much particulate matter, and various governments have limits on that.
But also it’s interesting from a climate point of view, because those particles interact with incoming solar radiation, so they can either absorb or scatter that radiation. And this is a very complex sort of area, because depending on the properties of those particles, they can either absorb more than they scatter, or scatter more than they absorb. And that means that they might warm, they might cool. And it’s this really complex system that I’m not usually involved with. The particles interacting with the light and more the formation of the particles if that makes sense.
Ross Chambless
So, there’s different types of isoprene and it might react differently?
Alfred Mayhew
No. So, isoprene is just this precursor compound. So that’s the thing that’s emitted. That’s the individual chemical compounds in one structure. So, that is one individual biogenic volatile organic compound. Then there’s a whole range of different biogenic volatile organic compounds. There’re also terpenes and there’s alpha-pinene, and Sesquiterpenes. So, there’s a huge range. And then there’s anthropogenic volatile organic compounds. So, these are similar sort of compounds but emitted by people. And so, all of these are all different types of chemicals that can undergo hugely complex chemistry to form pollutants like secondary organic aerosol. So yeah, my Ph.D. work was very focused on this one individual compound. My current work is now more broadly looking at a specific chemical reaction pathway that could happen to any one of those compounds.
Ross Chambless
Interesting. So maybe we could focus a little bit on your current work and how that relates to climate change in a way. And it sounds like this is an area that really needs a lot more study. I mean, because I think people are familiar with carbon, CO2, carbon dioxide, or they are familiar with methane as far as often discussed greenhouse gas emissions. But isoprene seems to fit in this sort of niche area where not a lot of people are thinking about it. So, what are you exploring here with that?
Alfred Mayhew
So, the climate links. Again, they come through this particulate matter formation, and so an aerosol has been highlighted by the IPCC as one of the areas of largest uncertainty in terms of climate predictions. And a lot of that has to do with these complex radiation interactions that I was talking about before. And because depending on the type of particles, you could either have a cooling or a warming effect. And those two counterbalance each other in kind of complex ways.
But another aspect is the chemical formation of this aerosol. So, some small portion of that aerosol is secondary aerosol, and some small portion of that secondary aerosol is secondary organic aerosol.
So, my current research is not actually just focused on isoprene, it’s focused on, like I said earlier, a suite of different VOCs, but investigating a single chemical pathway which has been kind of predicted theoretically. So, through theoretical calculations of chemical reaction rates, they expect this particular pathway to occur. And they’ve also measured potential products of this pathway. But there hasn’t really been work to bridge that gap of implementing this chemistry into a global model, which is really the ultimate aim of my project: to take this theoretical chemistry, implement it into a global model, and just see what effect that has on particulate concentrations.
Ross Chambless
Interesting. So, it’s really kind of an unexplored chemical pathway. And do you plan to work in a laboratory to kind of simulate this to see how it might play out on a global scale?
Alfred Mayhew
Yeah, my work is currently entirely computational. So, my current workflow is to take these theoretically calculated rates and implement them into what’s called a chemical box model, which is separate from the global transport model. And it’s a bit more simplified, which allows me to have a lot more complex chemistry in there. I take these chemical rates, put them in this box model, produce some results, and then compare those to field measurements which have previously been made. And, so some people have made measurements of these potential products of this chemical reaction pathway. I take my box model and say, okay, does this roughly approximate what they’ve observed? If that’s the case, then I can start thinking about reducing that chemistry down to fit in the global model. And then we can see the impact. So yeah, not too much lab work at the moment. That is something I have done in the past and I do enjoy, but it’s all computational computation.
Ross Chambless
So, one of the questions I’ve had in trying to understand isoprene and its interactions with various other gases and elements and VOCs, is when it comes to considering air pollution and causes and what to do about it certainly in urban areas. Is it true that it could be a risk that a lot of urban areas have trees which we think are generally good for air pollution, for mitigating it in some cases in the right conditions or wrong conditions, that trees could actually be a contributing factor to air pollution problems?
Alfred Mayhew
Yeah, it’s a really weird and complex issue. But that is the case if, under certain conditions. If you didn’t think about what you were doing, you could have negative impacts on air quality by planting trees. I guess the good thing is that not all trees emit isoprene. Not all trees emit the same amounts of isoprene.
And I mentioned alpha-pinene before. That’s another important compound, especially for particulate matter. But essentially you can sort of pick your trees based on what kind of profile of compounds they give off. And because all plants give off some kind of organic compounds, they use it for signaling, they use it for stress tolerance and things like that. So, it’s something that generally should be considered.
I think, yeah, it’s always a risk with my work. The takeaway that some people have that trees are bad for air quality, which is a simplistic message. It’s not necessarily wrong. In some situations, trees may be contributing to negative air quality. But there’s all sorts of other things we care about for why we might plant trees.
And I guess the other thing to mention is these anthropogenic biogenic interactions that I mentioned before. So, if you’ve got no nitrogen oxides, for example… oh, sorry, if you have an existing city and you plant a lot of trees, then this may make air quality worse, if you don’t plant the right trees. But then if you also brought down your nitrogen oxide emissions at the same time, then that could offset that. You know, it’s a very complex system.
Ross Chambless
Yeah, lots of combinations.
Alfred Mayhew
Yeah, it’s not as simple as planting trees is good for air quality necessarily.
Ross Chambless
Yeah, that’s interesting because that often is sort the dogma or the often-stated assumption to explore. So, as I’m trying to understand this, you’re looking at biogenic volatile organic compounds, VOCs and various types that are less understood or talked about like Isoprene or alpha-pinene and you want to explore how these volatile compounds, when they’re released by both natural and or other sources, how they interact in the atmosphere and how they might be contributing to climate change forcing in some way? Is that sort of an accurate summary?
Alfred Mayhew
Yeah, that’s about right. I would flag that isoprene alpha-pinene are not understudied BVOCs, they’re the most studied BVOCs. It’s just that there’s such a complex system. There’s always something else to look at, right? So yeah, it’s not necessarily that they are understudied, it’s just that there’s aspects of that chemistry that are understudied and they are the most studied because they’re the most prevalent.
Apart from that, yeah, I think focusing on particulate formation through chemistry and the atmosphere, that’s of interest for air quality. But then also and trying to get some idea of what effect that could have on the climate system through these kind of radio radiation interactions and with incoming solar radiation.
Ross Chambless
So, with your work, I assume you have a couple of years planned out as far as research when you hope to reach some various conclusions with results. How do you see, at least at this point right now, where you hope that what you’re studying right now might inform policy decisions, behavior changes, or practical actions, you know, down the road? I know that’s a difficult question, but seeing the bigger picture, I guess.
Alfred Mayhew
Yeah, it’s always difficult with my kind of work, especially, I think, because it is so kind of fundamental science research. Yeah, it’s hard to say at the end of my research project we will know not to do this or to do that, because really the ultimate aim is just to improve the chemistry that ultimately feeds into climate models, in the sense of climate.
I’m not actually currently working with any climate models. I will kind of stop at what we call a chemical transport model, which tends to operate on the scale of a few years of model time. And, essentially a climate model will be a lot less complex so that you can run it for more time. Because obviously we care about climate over more than the next two years. So, my work would kind of stop there.
But I mean, it depends on what we show, right? If we show that this is not an important pathway, then I guess that’s good. We can just keep ignoring it. But there’s a possibility we will show that this has some significant impact on particulate formation. And then we’ll have to think about how we take this chemistry and represent it in some form and in these less complex models. Which is actually very difficult to do because just because of the way the chemistry works. It’s very complex chemistry. It requires the interactions of lots of different groups of compounds, which is difficult to represent in kind of a simplified form.
Ross Chambless
Right. You know, I was I was thinking about the study of atmospheric sciences, and how in your field of research, you’re dealing with these very complex phenomena that occur all around us all the time where we live our lives, but yet so much of it goes unseen. And so, unless you’re aware of it, but I think most people are not in tune with it necessarily, right? And so, trying to wrap your mind around it or explain what’s happening and make sense of it, you know, I’m sure it comes with its challenges, right, as far as trying to explain how these things are going on? And, yet obviously extremely important at the same time to understand. So, it’s just a very interesting line of work to be seeing things that not most people don’t see.
Alfred Mayhew
Yeah, well, you can’t see… well, sometimes you can see bad air quality, which I guess helps. But that’s actually an interesting part of messaging. Again, I keep straying into air quality because that’s my predominant focus. But there’s quite interesting messaging around air quality. You know, when you can see a haze over Salt Lake City like a few days ago, and everyone is very cognizant and realizes that it’s there. But with something like ozone which you can’t see, or even just lower particulate concentrations, which still may be above recommended guidelines or whatever, but they’re not visible, it’s harder to get across that message to people. That that’s still important.
That also ties into things to do with indoor air quality as well. This is a big area of research and sort of emerging. People spend most of their time indoors and indoor air quality can often be very different from the air that’s outside because we do all sorts of different things inside. We cook inside and we use cleaning products and things like that. And all of these are releasing compounds into the air that we breathe. Anyway, that’s not climate, so I’ll be quiet!
Ross Chambless
No, but very interesting and relevant, maybe for another conversation. Just a couple more questions I want to ask while we have you here. Kind of unrelated to your current research, but how is life in Utah now? Since coming here and doing your postdoctoral research, what have you been in your impressions? What have you found that you enjoy doing?
Alfred Mayhew
Yeah, it’s been good. I arrived from the UK in the middle of summer, and it was very, very, very warm. And now I’m sitting here looking out the window and it’s snowing. So, it’s definitely the extremes that we don’t really get in the UK in terms of weather. But, I’ve enjoyed that. I’ve gotten the opportunity to head out into the mountains a couple of times for some hikes, which I really enjoy. Yeah, it’s very different from York where I did my undergraduate and postgraduate degrees. It’s kind of a quaint English town, technically a city. Whereas this is a proper American city. But yeah, it’s really good. I’ve enjoyed the time in the departments. It’s great. And just kind of getting on with the work.
Ross Chambless
Well, Alfred Mayhew, thank you so much for taking your time to talk about your research with us, and perhaps we can follow up many months down the road and check in to see where you’re at. So, thanks again.
Alfred Mayhew
Yeah, thank you.