Science Interviews

On the Road with Mobile Sensors

Helen -  You are listening to The Naked Scientists with Chris Smith and me, Helen Scales and we have heard a lot about the portable sensors that Rod Jones and his team are using to monitor pollutant levels whilst walking around a city.  So lets now join Meera to see how these sensors actually work in action.  

Meera Senthilingam -   Yes, so I am now here at the Chemistry Department at the University of Cambridge with Rod Jones and we’ve got one of these handheld devices in front of us and there’s a lot packed in here so what have we got here, at the top we’ve got the three sensors, what are these sensors detecting?  

Rod Jones -   Well the three that you can see here are detecting nitrogen dioxide, nitric oxide and carbon monoxide.  Inside each sensor there’s a small amount of fluid which is called the electrolyte and when the gases enter the sensors that actually forces very small current to flow in that electrolyte and you measure the current so you can relate the current from this which is very small, to the amount of gas that you are trying to detect, and of course this box does rather more than that then because what it has to do is to take that current and digitize it so that we can then transfer it to a computer.  

These boxes actually also determine where we are using GPS that everybody knows, and in fact there’s a blue tooth connection here which then links it to a mobile phone which is sitting just next with me now and it’s that mobile phone which transmits the data from the sensor in real time to a central computer so that we can look at it.  

Meera Senthilingam -   Now you have managed to pack all of this into not only a light box but it’s size is actually quite small, it’s only about 15 cms by about 5 cms - and you are going to take me on a particular route around Cambridge so we can see these devices in action.  Where are we going to go?  

Rod Jones -   Well we’re going to go from the Chemistry Department which then enters immediately a busy road.  We are gong to walk towards a major traffic junction and then into an area which is green park area really.  These are typical of the kinds of places that we have been making these kinds of measurements.  

Meera Senthilingam -   We are outside the Chemistry Department now with the handheld monitor.  Rod, how are you going to turn it on?  What should we do before we start our walk?  

Rod Jones -   Well I have just turned the phone on and it now shows the screen which I can then use to detect the sensor box.  On the sensor box I am just switching on that by pushing one single button and in a minute, there we are, it’s telling us that the device is working and has actually detected the GPS satellites.  So we are now ready to go.  

Meera Senthilingam -   Okay, so lets go.  We are heading down towards a particularly busy junction.  Now I can imagine that the sensor will be particularly active right now.  

Rod Jones -   Well yes, the chemistry of the atmosphere is really quite complex.  A lot of these vehicles are going to be releasing a fair amount of nitric oxide and so we’d like to expect to see really quite high values of nitric oxide and of course individual cars have very different emission a month.  So and the age of it already matters as well that if a vehicle is old and not particularly well maintained, it is quite likely that the emissions from that are going to be much higher.  

Meera Senthilingam -   It is very busy here.  There are numerous cars, motorbikes, lorries, trucks just going by but now we are going to head over into the quite Parkers Piece.  

Rod Jones -   It’s very interesting because if we are trying to understand how the chemistry of the troposphere works, we actually have to look at a lot of different sources and immediately you can see that we have trees and greenery here, all of which can emit a range of different molecules which can affect the chemistry of the troposphere.  So we need to get the complete picture and this little box is part of that process.  

Meera Senthilingam -   We are now in the middle of Parkers Piece, which is a very large green area here in Cambridge.  Now it is much quieter, the cars are much further away but you know, they are still not that far so surely the pollutants are still going to be reasonably high here.  

Rod Jones -   That’s right, and in fact we can feel a slight breeze, that’s obviously going to bring the pollution from the road which we can see just over there into Parkers Piece.  We are not likely to see quite as big fluctuations in the emissions from vehicles because they have now tended to mix out a little bit.  

Meera Senthilingam -   As pleasant and sunny as it is here we now are going to go back to the lab in order to look at the information of this particular ride.  

We are now back on Rod Jones’s lab in the Chemistry Department but joining me now is Mark Calleja who is a software developer on the project.  So Mark, you’ve got your laptop with you here and it’s got Google Earth on it so on your Google Earth now we’ve got a satellite view of the area that I just walked with Rod.  What are you going to show me on this particular view of Cambridge?