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Measuring Air Quality
We monitor air quality by measuring the amount of small particles in the air - the technical term is 'particulate matter smaller than 10 microns', or PM10. The National Environmental Standard for air quality states daily average concentrations must not be greater than 50 micrograms of PM10 per cubic metre of air for more than one day a year from 2013 onwards.
Between now and 2013 we need to decrease the number of exceedences to no more than 1. This is because there is a very significant increase in risk to human health above this level.
How We Measure Air Quality
We measure air quality in Richmond throughout the year to determine the volume of small particles in the air.
We also measure the weather conditions in Richmond, as wind direction, wind speed, rainfall, temperature and solar radiation may affect how air contaminants are dispersed, and where they build up. This is important in the process of managing Richmond’s air quality problem during winter. This will help us understand if air quality is improving for a certain meteorological condition.
Method for Measuring Air Quality in Richmond
To measure air quality in Richmond, we use a Beta Attenuated Monitor (BAM) to find out how much suspended particulate (PM10) is in the air. We also use a Partisol for specific investigations in Richmond and other towns.
A small pump in the instrument sucks air through a size-selective inlet and through a filter at a constant rate. A constant source of high energy electrons (beta particles) is beamed through the filter where the PM10 deposit is collected. The number of these electrons is reduced (attenuated) by the PM10 deposit on the filter at a rate directly related to particulate mass (weight) which is then calculated. Because the machine knows how much air was sucked through the filter the concentration of PM10 in outside (ambient) air can be calculated.
The information from the BAM is then automatically sent to Tasman District Council via the phone lines along with wind speed, wind direction and temperature data. Data you see on the website is raw data directly fed from the instrument.
The 1- minute or hourly PM10 readings are averaged into a daily reading, and are also displayed as daily averages for the past week and winter season.