– the intergovernmental organization through which Member States act together
     on matters related to measurement science and measurement standards.
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Publication of new ozone cross-section measurements for the accurate monitoring of air quality

Ozone is a major air pollutant affecting human health and agriculture, with many national and regional regulations defining maximum exposure limits and requiring continual air-quality monitoring for the protection of their populations. Measurements of ozone concentrations at the ground level are based on the absorption of UV light at 254 nm, with the traceability and consistency of measurements assured through national ozone reference photometers, notably the NIST Standard Reference Photometer, and their comparisons coordinated by the BIPM (BIPM.QM-K1).

New measurements of the ozone cross section carried out in the BIPM laboratories, together with visiting scientists from KRISS (Republic of Korea), and GUM (Poland), have been published. These measurements report a value 1.8 % lower than the conventionally used value. The description of the experimental design and measurement results appeared in the journal Atmospheric Measurement Techniques*. A discussion of the potential impact of this result on ozone-monitoring networks will take place within the CCQM Gas Analysis Working Group.

BIPM experimental set up for O3 cross section measurements. AOM Acousto-Optic Modulator; BS Beam Splitter;
CDG Capacitive Diaphragm Gauge (Baratron); CRYO cryogenic ozone generator; LT Light Trap; M Mirror;
RGA Residual Gas Analyser (Quadrupole mass spectrometer); TMP Turbo Molecular Pump; V Valve; WM Wavemeter

*Viallon J., Lee S., Moussay P., Tworek K., Petersen M., and Wielgosz R.I., Accurate measurements of ozone absorption cross-sections in the Hartley band, Atmos. Meas. Tech., 2015, 8, 1245-1257.

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