Air quality monitoring in Cork City
Calculation of the Air Quality Index for Health The EPA uses the data collected from the automatic air quality monitoring network to measure how much air pollution there is at specific location. This data is measured at a rate of work out by cubic metre (m 3 ) every hour. The index (number) for each pollutant is calculated separately and the overall AQIH is the highest of the five pollutant indices. For example, if there is more ozone than sulphur dioxide, the higher number for the ozone is applied to the overall AQIH. Cork City Local Air Quality Monitoring Network Cork City Council has procured a number of air quality sensors to measure particulate matter (PM 2.5 ) and has installed them at locations across the metropolitan area of Cork city. These sensors use laser particle counters that provide an accurate and low-cost way to measure smoke, dust, and other particulate air pollution. Whilst the sensors have undergone a validation and recalibration process in a collaborative project between Cork City Council and University College Cork, they provide indicative air quality data only and the data displayed should be interpreted alongside the EPA reference sensors mentioned in section 3.2 below. Nitrogen Dioxide Diffusion Tube Survey Diffusion tubes are passive air samplers that consist of small plastic tubes containing a chemical reagent to absorb the specific pollutant to be measured directly from the air. Nitrogen dioxide concentrations often show seasonal variation, so it is recommended that all surveys should be carried out for a minimum of six months, therefore diffusion tube monitoring is typically carried out over an entire year in order to attain an annual mean value. The immediate area around the sampler location must be open, allowing free circulation of air around the tube. Ideally, samplers would be placed at breathing height, but in order to reduce theft of tubes, they are usually placed at a height of 2 to 4m from the ground. Concentrations of NO 2 typically decrease with height above street level, so tubes placed some metres above street level can under-estimate the actual concentrations to which the public are exposed. As far as is practical, all tubes within any given monitoring programme should be placed at similar heights. Diffusion tubes are inexpensive and can be positioned over a wider area to get a greater picture of NO 2 levels within a local area. Results from diffusion tubes have a higher level of uncertainty than concentrations measured using the European Standard Method (CEN) (i.e. the approved standard reference method), and for this reason they are categorised as an ‘indicative’ monitoring technique. A diffusion tube study to measure nitrogen dioxide (NO 2 ) was conducted in Dublin between 2016 and 2017 and in Cork City between 2019 and 2020. This study was designed to test the feasibility of using diffusion tubes to determine NO 2 concentrations in the air. Indicative NO 2 concentrations were determined using passive diffusion tube samplers throughout this survey. The results of the Cork City survey will be made available to the public in 2021. 3.2 Monitoring Programme There are 4 ‘reference level’ air quality monitoring stations installed across Cork City Council’s functional area that provide live, continuous air quality data. These stations are termed reference air quality monitoring stations and are used by the EPA for national reporting purposes. The stations are located at:
» Heatherton Park » South Link Road » University College Cork (UCC), Distillery Fields, North Mall Campus » Munster Technological University (MTU).
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