The choice of parameters to be monitored will be based on a number of factors, including those laid down in regulations, local sources of pollutants, or for particular studies. Typical pollutants sampled in a monitoring system include Suspended Particulate Matter (SPM), preferably at the PM10 or PM2.5 size range as these have the greatest health impacts; Sulfur Dioxide (SO2), Oxides of Nitrogen (NOx), Ozone (O3), Carbon Monoxide (CO), and Lead (Pb). Meteorological data should also be monitored.
There are a number of different methods to measure any given pollutant, varying in complexity, reliability, and detail of data. These range from simple passive sampling techniques to highly sophisticated remote sensing devices. A monitoring strategy should carefully examine the options to determine which methodology is most appropriate, taking into account initial investment costs, operating costs, reliability of systems, and ease of operation.
The locations for monitoring stations depend on the purpose of the monitoring. Most monitoring networks are designed with human health objectives in mind, and monitoring stations are therefore established in population centers. Many governments (local, regional or national) give specific guidelines on where to monitor within these areas - next to busy roads, in city center locations, or at a location of particular concern - such as a school or hospital. Background monitoring stations are also established, to act as a "control" when determining source apportionment.
The data collected from air quality monitoring systems may be used for a variety of purposes. In all cases, however, the data must be robust.
Quality Assurance/Quality Control systems are vital to ensure reliability of data, and should be determined at each step of the monitoring process - from sampling to laboratory analysis (where required) to data manipulation.
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