The Planet Earth podcast - 'Brown water, bats and streetlights, plant methane'.
13 July 2012
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Sue Nelson:Hello, I'm Sue Nelson and welcome to the Planet Earth podcast. Now, think of that Harry Potter scene where they first learn to ride a broomstick at Hogwarts. Now you've got a pretty good idea now of what the University of Glasgow's quadrangle looks like and in a moment I will be going up one of its turrets for a glass of water.
Later on there's news of the methane project in Edinburgh and we will also be going in search of bats in Bristol.
Richard Hollingham:It's like a particularly grim episode of Spring Watch isn't it?
Emma Stone:There's a blank screen and presenters standing around twiddling their thumbs.
Sue Nelson:Drinking a clear, cool glass of water is one of life's essential pleasures but if you've ever turned on a tap and experienced brown water coming out then you will know that it is less than appealing. However, it is a definite interest to Professor Susan Walden in Glasgow University's water and sediment lab and that's where I am now. Susan, what causes that brown colour sometimes to come out of a tap?
Professor Susan Walden:The brown colour occurs when there is a high concentration of dissolved organic carbon in the sample and the higher the concentration of dissolved organic carbon the deeper the colour and that dissolved organic carbon is coming from the soils that are in the catchment around about the drainage system, they break down and produce material that goes into solution and then when we have movement of water from the catchment soil, such as under a rainfall event, we have movement of that carbon into the catchment water.
Sue Nelson:Now you've got a couple of samples of water here ranging in colour where we've got a bottle of mineral water on the side there, so that's very clear to, I suppose there's no way of putting this, it could be urine samples, I suppose.
Professor Susan Walden:Well we like to think of them closer to whisky but, yes, the darker the colour the higher the concentration generally of dissolved organic carbon and in river systems we can see concentrations that can be up to 16 mg/litre carbon and they can really be quite dark brown samples.
Sue Nelson:So where have these particular samples come from? Are these from rivers around the Glasgow area?
Professor Susan Walden:These particular samples are from one of our study sites which is our wind farm development where we are trying to better understand if there is an increase in the amount of carbon that is exported from the catchment soils into the rivers in response to either the wind farm being built or after the wind farm has been built.
Sue Nelson:Has there been an increase in the amount of carbon and brown water that you get nowadays?
Professor Susan Walden:Within the UK there are quite a large group of scientists who understand very well the processes by which carbon is transmitted into a catchment drainage systems and what they have observed is that there has been an increase in the amount of carbon that is going into water or Europe, the UK, parts of North America and this has happened over quite a long timescale, about 20 or 30 years. There are multiple competing hypotheses for this but the one that is most commonly accepted is that actually as we clean up our atmospheres then we reduce the amount of acid deposition that there is, it promotes the breakdown of organic material and produces this dissolved organic carbon that can then go into the river systems. So, effectively, as the atmosphere's become cleaner the water can become browner.
Sue Nelson:That seems counter intuitive doesn't it?
Professor Susan Walden:Yes, but it is the sulphate deposition inhibited the production of dissolved organic carbon.
Sue Nelson:Sorry, what do you mean by that?
Professor Susan Walden:Sulphate deposition is your acid drain. Okay, so as we clean up the acid deposition that is coming from large scale industrial manufacturing, we're cleaning up the atmosphere and we're not depositing so much sulphate on our soils and we're increase the amount of carbon that is being produced as dissolved organic carbon.
Sue Nelson:Is it harmful this water? If I was to drink my brown carbon saturated water would it be doing me any harm?
Professor Susan Walden:Many people who have private water supplies do drink brown water. I'm not a medic so I can't comment on whether there is a long term impact of them drinking brown water, but my understanding is probably not.
Sue Nelson:But water companies, I am assuming, though, must spend extra money trying to make brown water clear?
Professor Susan Walden:That's correct because aesthetically people don't like to drink brown water, it looks dirty. We associate the brown colour with soils and therefore we think that our waters are contaminated with soils and it could be that if the water is not purified of the material that gives it the colour it may not also be purified of other components so this is understandable why people don't want to drink coloured water. So, therefore, the fact that our waters are becoming more coloured presents a problem for the water companies because they have to invest more in cleaning up the water and they need to also understand how the carbon is arriving at the water purification plant. So, is it coming in at a continuous low level which is just increasing or is it coming in in spikes and can their equipment actually cope with this increase in carbon concentration if it comes in in a spike or not.
Sue Nelson:And what are discovering so far?
Professor Susan Walden:That land [unintelligible 0:05:10.6] change can affect the increase in carbon concentrations. We know well that there is a very strong hydrological response to movement of carbon into river systems and that there is a seasonable component as well. So, we understand that at the end of the summer when we've had higher productivity in the landscapes and then subsequent breakdown of this organic matter and we're supposedly into a wetter period when the catchment start to wet up again in the autumn time when we have heavier rainfall then that is when we have the largest amount of carbon moved into the catchment. But it is very interesting because we are potentially moving to a situation where we will have different levels of productivity as temperature regimes changed and as has been apparent over the past few months where we have had the wettest quarters since records began recently, the time period when water was being delivered to the catchment also changes. So what we don't understand yet is how carbon will be delivered to the catchment under a changing climate and that's very important because the company's need to be able to understand better how to manage their resources in purifying their water as best as possible. So we're taking our knowledge amount what we know the processes that generate carbon in the catchments, how it is delivered to the catchment and then trying to understand how the changes might occur under projected climate change.
Sue Nelson:Professor Susan Walden, thank you. You touched on wind farms there and we will be reporting from a wind farm about the range of research associated with carbon and the environment in the autumn. Now nights aren't as dark as they used to be as street lights have transformed our towns, cities and even our countryside, but how have they affected wild life. Emma Stone from the University of Bristol has been looking at the effects of street lights on bats. So Richard Hollingham joined Emma in the centre of Bristol at dusk in the hope of finding some bats, but the evening didn't quite go as planned.
Emma Stone:We are along the Cedar Road which is behind the train station and we've got one of the main rivers that run through the centre of Bristol and along this river which is used quite a lot for fishing and boating you also get quite a lot of bat activity during the summer. There are a number of roosts in the old warehouses that are used along the river, mainly pipistrelles, and Daubenton's.
Richard Hollingham:I have to say I think it's a fairly grim location. We're standing under a willow tree beside a fairly brown murky river in the rain with the road behind us, both shivering slightly. But there are warehouses either side of the river and there are bats in here?
Emma Stone:Yes, there are, yeah, and the species that tend to roost within central city locations will always pick out the greenest and best areas to roost which are close to foraging grounds and river ways even though they are in the centre with these nice overhanging willow trees do provide shelter for insects where the bats can come out and forage at night. The bat species that will roost along here, the pipistrelles are very, very generalist species, they roost in pretty much anything so they will be quite happy in a building, in a crack or crevice, the size of your thumb you can 50 to 100 bats in there.
Richard Hollingham:What's the fascination with bats because we don't often see them but there are an awful lot around.
Emma Stone:Well they are very, very interesting animals. They use echo location which is fascinating, they also use vision, they are the most adapted flight, they are much better at flying than birds in terms of efficiency, they are highly manoeuvrable - I mean there are so many things to like about bats. They're highly manoeuvrable. I mean there are so many things to like about bats.
Richard Hollingham:You're looking at bats and street lights?
Emma Stone:Yeah. So, what we're trying to do is look at whether the increasing number of street lights and the new developments in technology are having negative impacts for bats, because obviously all our bats are protected in the UK and in European level, so what we're trying to do is just look at those species that might be negatively impacted by street lighting and understand what those impacts are and how best to mitigate them.
Richard Hollingham:Now you've been doing this research for some years now, what have you found so far?
Emma Stone:We've mainly focused on woodland adapted species so Lesser Horseshoe bats. We've also compared this with other species which are more dominant in the landscape, so pipistrelles, which are your common ones and what we've done is we did some experiments where we took standard streets out into the field, along the flight routes of these bats and see how they responded.
Richard Hollingham:So you actually took street lights to areas rather than just look at street lights?
Emma Stone:Yeah, because most of the research so far has focused on existing lights and obviously they are only going to be having those bats around that are able to cope with lighting or actually forage under street lights because of the increased insects, but those species that may be are negatively impacted you are not going to be able to study if you look at existing street lights. So we went to areas where there was woodland adapted species, we know they forage there, we know they commute along those linear features and we took the lights to them to see how they respond. And we looked at the impact of high pressure sodium lights which are, well, previously, the most dominant light type in the UK-
Richard Hollingham:They're the orangey glow ones, the oldest ones?
Emma Stone:Yeah, not the really amber ones - they're the sort of pinkish amber ones. So we tested the impact of those on the commuting routes, the flyways of horseshoe bats and found that they actively avoided them so they wouldn't fly along their normal flight routes when the area was light with high pressure sodium lights.
Richard Hollingham:Now, sodium lights are the oldest ones. They are being phased out. You also looked at the new lights, the LED lights which are environmentally friendly in that they use less electricity?
Emma Stone:Yeah, so that was next stage in the process really was to say, okay, well these older lights we know they have a negative effect. What about the way forward? What about these new technologies that they are bringing in that are being promoted as green technology, are they really green for biodiversity, so we brought LED lights out into the environment and did the same experiments and unfortunately we found the same negative impact. So these bats also tend to not like LED lights either and will avoid light areas with LED white lights.
Richard Hollingham:Well as we have been talking it has been getting darker and we are hopeful we will see some bats. It has also pretty much stopped raining, there's still a little bit of drizzle. It's not the warmest night though.
Emma Stone:No, it's not the warmest night and temperature will affect activity. Really you don't want it to be any colder than 6 degrees and obviously you don't want heavy rain because the insects will then shelter in the vegetation.
Richard Hollingham:Now you've got a bat detector here. What is this actually going to detect, we hope.
Emma Stone:Well hopefully I've got a frequency...sorry a heterodyne detector which you tune to the individual bats species, so each bat species echo locates at different frequencies. So if you tune it to the right frequency you can tell what bat you are listening to. And so what we will do is we will have a listen and see if we can pick up any pipistrelles and pipistrelles are the most common species, we've got sopranos and common pipistrelles, two different species and the most common ones echo locate at 45 kilohertz.
Richard Hollingham:So adjust the box there to 45.
Emma Stone:I'm tuning it now to 45 and the soprano pipistrelles echo locate slightly higher hence the name soprano and they echo locate at 55.
Richard Hollingham:Well we've been here for about half an hour now and so far we have seen several sea gulls, a boat and many cars going behind us, but still no bats. But it is, finally, starting to get a bit darker now.
Emma Stone:Yeah, I think in the next 20 minutes or so you start to get a few bats coming out.
Richard Hollingham:We're just picking our way very carefully alongside this canal. It's slight rough ground and a very narrow path, so that would be the worst outcome of the evening would be falling in the river.
Emma Stone:It would add some excitement though.
Richard Hollingham:I almost did actually!
Emma Stone:The bats have been doing strange things this season actually. They have delayed...a lot of the bats where we've been working this season at the roosts have delayed giving birth and that's basically because we have had such bad weather in April, so they weren't able to benefit from good foraging opportunities, so they've delayed and they've not given birth as early as they normally would.
Richard Hollingham:It's like a particularly grim episode of Spring Watch isn't it?
Emma Stone:Yeah with a blank screen and presenters standing around twiddling their thumbs!
Richard Hollingham:Okay, we've been here an hour now. Dusk officially has come and gone. It's starting to get dark now and no bats.
Emma Stone:There are no bats, but I think if I was a bat I would be staying in bed. It's a little bit chilly.
Richard Hollingham:I'm inclined to agree, it's really quite cold.
Emma Stone:It's a little bit chilly. It's not exactly inviting out here so if I was them I would be staying tucked up a little bit longer.
Richard Hollingham:Well at least this is realistic isn't it. This is what wild life watching, wild life listening is all about. You actually spend quite a lot of time standing around and nothing happening.
Emma Stone:Yeah you do, you spend a lot of time being very bored actually. Not seeing a lot and then you get those lovely genius moments and those little glimpses and that is what you wait for, but you can't guarantee it, you never know what's going to happen. Most of the animals don't read the text books, they do what they want and you can never predict it, but that's the beauty of it actually because you never know what you're going to get from one day to the next but unfortunately we're just unlucky tonight.
Richard Hollingham:I was going to say tonight, nothing.
Emma Stone:Nothing, absolutely nothing, but you pays your money and you takes your chance, you never know.
Sue Nelson:Emma Stone with Richard Hollingham in the rain in the centre of Bristol without any bats.
In 2006 it was discovered that plants produce significant amounts of the greenhouse gas methane. The research caused quite a stir at the time and it forced scientists to rethink the role of plants and forests in global warming. One of the questions that needed answering was how plants emit methane and so a research group at the University of Edinburgh set up The Methane Project. I went to met Dr Andy McLeod at Edinburgh University School of Geosciences to find out more.
Dr Andy McLeod:The Methane Project is to investigate the mechanisms by which plant leaves can emit the greenhouse gas methane.
Sue Nelson:So how do you go about doing that because I don't see many plants here in your laboratory?
Dr Andy McLeod:Well there are no plants here now but what we do is enclose the plant leaves inside chambers and these chambers are specially constructed to transmit ultra violet radiation which you find in sunlight and we use the chambers to determine what gasses are emitted and that includes methane.
Sue Nelson:Although scientists now that this process is happening, you know that methane is being produced by plants, albeit relatively recently, we still don't know how this methane is produced and this is where your labs come in.
Dr Andy McLeod:Yeah, the purpose of the project was to investigate the role that ultraviolet radiation may play in causing this methane emission and it would seem that the ultraviolet radiation when it impacts organic molecules within the leaf can result in the release of methane into the atmosphere.
Sue Nelson:Right, well let's go through how you actually go about doing that - we've got two small labs off a corridor side by side, let's start with the quieter one inside, what goes on in here?
Dr Andy McLeod:In this lab we have a very powerful xenon arc lamp which can produce very high levels of visible and ultraviolet radiation.
Sue Nelson:That's just a black box here which produces a huge blinding white bit of light I assume.
Dr Andy McLeod:Yes, absolutely. We have to wear eye protection when we're using this and we filter out the infrared radiation which would heat up the leaves of the plants, we then filter out particular wave lengths of ultraviolet so that we can determine which waves lengths of ultraviolet are producing the effects we observe.
Sue Nelson:Do you use any types of plant in particular or is that irrelevant?
Dr Andy McLeod:The purpose of the project was to evaluate a range of plant types to determine whether particular plant types produce more methane or UV radiation compared to others. Our partners in the project are the Royal Botanic Gardens in Edinburgh where they have a large range of plant types in their collection which are made available to us for this investigation.
Sue Nelson:Right, well let's go to the next lab which is a little bit noisier - here we go - there's a big fan whirring at the end. We've got a bench with what looks like kitchen fluorescent tubes of lighting above it, almost like a sun bed but with all sorts of wiring and copper tubing and syringes beneath, not the sort of sun bed you would want to actually lay on.
Dr Andy McLeod:No, in fact it is in fact very like a sun bed but the tubes used in this system produce very high levels of ultraviolet B radiation which would actually give us a sun tan far too quickly and be quite dangerous.
Sue Nelson:So you eradiate effectively the plants and then you simply attach some sort of piece of equipment to the plant in order to measure the methane. We must be talking about very small amounts of methane here?
Dr Andy McLeod:Yes, and one of the problems is measuring the very small amounts of methane produced and we do this in two different ways. When we have a closed chamber where there is no air flowing through it we can transfer gas samples in a syringe to the gas chromatograph on the other side of the lab where the concentrations are measured. We also have a monitor beneath the system here which gives us continuous measurements of methane if the gas is flowing through the chamber.
Sue Nelson:And what stage are you at at the moment in terms of your project?
Dr Andy McLeod:This is the final stages of the project where we're completing some of the measurements and we're analysing some of the chemical constituents of the leaves to see how they may be involved in the process.
Sue Nelson:And at the end of it what do you hope to gain? Obviously you want more of an insight into how the process works but do you think you're at that stage of getting it? Do you know how this process works now?
Dr Andy McLeod:We're fairly confident that ultraviolet radiation does result in the production of methane and some other trace gases from plant leaves. In terms of quantifying how much that is it seems that it is still a very small amount making quite a small contribution to global emissions of methane into the atmosphere.
Sue Nelson:So there are still other areas to be discovered in terms of how methane is produced by plants?
Dr Andy McLeod:There may indeed be other mechanisms and there are reports in the literature that physical damage causes the emission of methane from plant leaves and also other environmental stresses like high temperature.
Sue Nelson:Recently on the Plant Earth podcasts we featured a sort of unexpected result of your work which was that it was used by space scientists to examine meteorites.
Dr Andy McLeod:Yes, that's correct. At a meeting with other scientists in Europe we debated the possibility that ultraviolet radiation will contribute to the methane in the Martian atmosphere and we therefore decided to do some experiments to investigate whether this might be true. We used samples of a meteorite called Murchison which fell in Australia in 1969 and the substrate of this meteorite is very similar to what you would find on the surface of the planet Mars. We ground samples of this meteorite up and then we radiated them in equipment similar to the equipment you can see here and again we measured the methane that was produced.
Sue Nelson:And sure enough...
Dr Andy McLeod:The samples produced methane on UV radiation, sometimes much more than we found from substrates that we've been studying in a study here.
Sue Nelson:Dr Andy McLeod from the University of Edinburgh. The Planet Earth podcast was brought to you by the Natural Environment Research Council from the University of Glasgow. Do check out our Facebook page and Twitter feed but until next time thanks for listening.