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  • Rights: The University of Waikato
    Published 18 June 2008 Referencing Hub media
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    Professor Simon Kingham, from the University of Canterbury, discusses how air pollution can be made up of many components. The size and amount of particulates1 in the air can give a measure of the level of air pollution. A team of researchers collect samples of air in various ways to measure these particulates, which can vary in size.

    Transcript

    PROFESSOR SIMON KINGHAM
    The reason, in New Zealand, that we are particularly interested in particulates is because it comes out of domestic fires, and we have a lot of people heating the home with domestic wood burners. In countries where traffic is the main source of pollutants, it’s other pollutants like nitrogen dioxide2, carbon monoxide3 and things. A particulate is a type of air pollution. A particulate is dust, in essence – it’s a solid, it’s not a gas, like you might have heard of things like nitrogen4 dioxide and carbon5 monoxide. In particulates, we talk about micrograms, so the amount of dust per cubic metre6 of air. Some people also like to count the number of particles – they say it’s not the size of the particles that's important, it’s the number of the particles. The particulate we are most interested in is very fine dust – it’s dust so fine, you can't see it. And so we classify it according to the size, so we have a thing called PM10, which is particulate matter7 less than 10 microns. So if you looked at a human hair, you get five particles of PM10 for a human hair, so you can't see it. We also talk about PM2.5, which is even smaller, PM1 , which is smaller again. There is different ways of measuring particulates – the simplest way is you draw air through a filter and you catch the particles, the dust, on filters. And what you find is that, the longer you do that on the filter, you can see the particulate because it ends up looking black. You calculate how much air you've drawn through the filter, and you weigh the filter before and after, and then you can convert that into micrograms per metre. The problem with that is that you only get an average over a fairly long period of time, so normally you have to monitor for 24 hours to get a reasonable amount of sample in New Zealand. And sometimes, what we are really interested in is how much it varies over much shorter periods of time. So we use a way of shining a beam of light through the air, and as the particles pass by that beam of light, it can measure how many particles are passing through. There is also a debate that it’s not the number, or the weight8, or the volume9 of the particles, but it’s actually what the particles are, in a way, carrying. So there is argument that, with diesel fumes, it’s… other compounds attach themselves to the particles, and it’s the particles that take these other pollutants into your lung. So, for instance, you might hear things called aromatic hydrocarbons. The idea is that they attach themselves to the particle10, and you breathe them into your lung, and maybe it’s them that's harming you.

    Acknowledgments:
    Sue Tyler

    1. particulates: Extremely small solid particles suspended in a gas or liquid, for example, soot or dust suspended in the air.
    2. nitrogen dioxide: Atmospheric gas that comes from the combustion of fossil fuels (coal, gas and oil), especially fuel used in vehicles. Nitrogen dioxide can have harmful impacts on the human respiratory system.
    3. carbon monoxide: Carbon monoxide consists of one carbon atom and one oxygen atom. It is an odorless, colourless, tasteless, flammable gas.
    4. nitrogen: A non-metal – symbol N, atomic number 7. Nitrogen is essential for life. It is a component of many molecules that make up cells, including DNA and proteins.
    5. carbon: A non-metal element (C). It is a key component of living things.
    6. metre: The base unit of length in the International System of Units (SI).
    7. particulates: Extremely small solid particles suspended in a gas or liquid, for example, soot or dust suspended in the air.
    8. weight: Force due to gravity acting on an object, measured in newtons.
    9. volume: 1. The quantity of space occupied by a liquid, solid or gas. Common units used to display volume include cubic metres, litres, millilitres, tablespoons and teaspoons. (Volume can refer to a large quanity of something). 2. The degree of sound intensity or audibility; loudness.
    10. particle: A tiny piece of matter. A particle may refer to an atom, part of an atom, a molecule or an ion.
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      particulates

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    2. Extremely small solid particles suspended in a gas or liquid, for example, soot or dust suspended in the air.

      nitrogen

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    4. A non-metal – symbol N, atomic number 7. Nitrogen is essential for life. It is a component of many molecules that make up cells, including DNA and proteins.

      weight

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    6. Force due to gravity acting on an object, measured in newtons.

      nitrogen dioxide

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    8. Atmospheric gas that comes from the combustion of fossil fuels (coal, gas and oil), especially fuel used in vehicles. Nitrogen dioxide can have harmful impacts on the human respiratory system.

      carbon

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    10. A non-metal element (C). It is a key component of living things.

      volume

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    12. 1. The quantity of space occupied by a liquid, solid or gas. Common units used to display volume include cubic metres, litres, millilitres, tablespoons and teaspoons. (Volume can refer to a large quanity of something).

      2. The degree of sound intensity or audibility; loudness.

      carbon monoxide

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    14. Carbon monoxide consists of one carbon atom and one oxygen atom. It is an odorless, colourless, tasteless, flammable gas.

      metre

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    16. The base unit of length in the International System of Units (SI).

      particle

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    18. A tiny piece of matter. A particle may refer to an atom, part of an atom, a molecule or an ion.