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Summary of Methods for Monitoring Ozone Concentration Levels
Monitoring Methods for Ozone Concentration Detectors The monitoring methods for ozone concentration detectors mainly include the indigo disulfonate spectrophotometric method, ultraviolet photometry, chemiluminescence, and differential absorption spectroscopy. In 1995, China issued GB/T 15437-1995, "Ambient Air—Determination of Ozone—Indigo Disulfonate Sodium Spectrophotometric Method," and GB/T 15438-1995, "Ambient Air—Determination of Ozone—Ultraviolet Photometric Method," respectively, to standardize the determination of ozone in ambient air. These standards provide detailed instructions on the reagents used in ozone concentration detectors, operational procedures, and calibration methods. 200
Ozone Concentration Detector Monitoring Method
The monitoring methods for ozone concentration detectors mainly include the indigo disulfonate spectrophotometric method, ultraviolet photometry, chemiluminescence, and differential absorption spectroscopy. In 1995, China issued GB/T 15437-1995, "Ambient Air—Determination of Ozone—Indigo Disulfonate Spectrophotometric Method," and GB/T 15438-1995, "Ambient Air—Determination of Ozone—Ultraviolet Photometric Method," respectively, to standardize the determination of ozone in ambient air. These standards provide detailed instructions on the reagents used in ozone concentration detectors, operational procedures, and calibration methods. In 2009, HJ 504-2009 replaced GB/T 15437-1995. In 2010, HJ 590-2010 replaced GB/T 15438-1995. In 2018, the Ministry of Ecology and Environment released a draft guideline titled "Ambient Air—Determination of Ozone—Chemiluminescence Method"; however, this standard has not yet been implemented.
Indigo Disulfonate Spectrophotometric Method: The monitoring principle is based on the fact that ozone (O3) in the air, in the presence of a phosphate buffer solution, reacts with sodium indigo disulfonate (C16H8O8Na2S2, IDS) in the absorbing solution in a molar ratio, causing the blue color of the IDS to fade and forming sodium indigo disulfonate. The absorbance is measured at 610 nm, and the concentration of O3 in the air is determined by quantifying the degree of blue color attenuation.
This method requires the collection of samples using chemical monitoring techniques for analysis, involving cumbersome procedures and large sample volumes. It was the primary method for early environmental air ozone analysis but is now gradually being replaced by automated monitoring methods—though it still remains in use. It is mainly applied to ozone analysis in regions where testing conditions are particularly challenging and online equipment cannot function effectively.
Ultraviolet Absorption Method: This method monitors ozone concentration by leveraging the property that ozone exhibits maximum absorption at a wavelength of 253.7 nm. According to the Rumbel-Bill law, when a beam of light passes through an ozone-containing gas over a path length D, the ozone concentration C can be calculated simply by measuring the intensity I0 of the incident light and the intensity I of the beam after it has penetrated the air containing ozone.
This method is a non-destructive physical monitoring technique suitable for continuous, real-time monitoring; it is simple and highly sensitive. Due to the accuracy of ultraviolet radiation-based monitoring results and their specificity toward ozone, this method is currently widely used in automated air quality monitoring stations in urban areas.
In the actual monitoring process, it is necessary to calibrate environmental ozone monitors. The HJ 1099-2020 “Technical Specification for First-Class Calibration of Ambient Air Ozone Monitoring,” issued in 2020 by China’s Ministry of Ecology and Environment, specifies the methods for calibrating ozone transfer standards using first-class ozone standards, as well as the associated quality assurance and quality control measures. The first-class ozone standard refers to an ozone standard reference photometer recognized by the competent authority for ecological and environmental monitoring; it serves as the highest metrological institution within the national ecological and environmental system. An ozone transfer standard is a portable instrument or device capable of accurately reproducing or precisely analyzing ozone concentrations and traceable back to higher-level or more authoritative standards. Ozone transfer standards are used to calibrate ozone calibration instruments or ozone analytical instruments that serve either to verify the authority of first-class ozone standards or to calibrate monitoring stations. The first-class calibration facilities for ozone monitoring include an ozone standard reference photometer, a zero-gas generation device, auxiliary equipment, ozone transfer standards, and data collection and transmission devices. The ozone transfer standards are calibrated using the ozone standard reference photometer.
Key words: Ozone Concentration Detector
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