Air quality management and research relies on accurate measurement data that gives information about emission, concentration and immission (deposition) processes. The location of measurement sites has to be selected based on the atmospheric lifetime and the impact scale of the investigated material; thus the air quality measurement points range from global background sites far from any human activities to emission measurement in the vicinity of the source areas.
To measure concentrations, there are various methods available. Most of them are based on wavelength-selective radiation detectors and spectrum analyses, using absorption spectrophotometry, fluorescence or chemiluminescence. Greenhouse gas concentrations are often measured with gas chromatography, a tool where a column interacts with the sample in a selective way that each material reaches the detector separately. Dry deposition can be measured through high temporal resolution concentration measurement to estimate fluxes, or using passive sampling to directly measure fallout of a pollutant over a certain period. Wet deposition is estimated from rainwater pH monitoring and chemical composition analysis.
Remote sensing tools have gone through a fast development in the past decade. Ground-based LIDAR and DOAS instruments are able to measure detailed 3D profiles of concentration and wind, while space-based spectrophotometers provide high temporal and spatial resolution data of vertical total concentrations, and they are able to estimate vertical profiles based on Doppler broadening of absorption bands. Polar orbiter satellites are often equipped with LIDAR-s to obtain high resolution vertical profiles along the satellite path. Satellite measurements have now become the most effective tools to monitor air pollution as well as atmospheric trace gas fluxes and transport.
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