| Abstract Title: | Implementation of a new (CCQM.O3.2019) value of the ozone absorption cross-section for measurements of ozone in ambient air |
| Presenter Name: | Dr Andrew Brown |
| Company/Organisation: | National Physical Laboratory |
| Country: | United Kingdom |
Abstract Information :
A new ozone absorption cross-section is being adopted globally. The new ozone cross-section value at room temperature at the mercury-line wavelength (253.65 nm, air), ‘CCQM.O3.2019’ is 1.1329 x 10-17 cm2 with a standard uncertainty of 0.0035 x 10-17 cm2 [1]. This is around 1.2 % lower than the conventionally accepted reference value ‘Hearn value’ [2] and has an uncertainty approximately six times smaller. It was defined by a task group established by the Gas Analysis Working Group of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM-GAWG), who analysed absorption cross-section data from fourteen independent sets of measurements between 1959 and 2016.
Implementation of the new CCQM.O3.2019 ozone cross-section across air quality networks will commence on 1 January 2025, and be completed 12 months later. In preparation for this change, the CCQM-GAWG Task Group on Ozone Absorption Cross-Section Change Management are overseeing the revision of international and national documentary standards (including the European standard EN 14625 [3]), actively communicating the change, and producing implementation documents for ozone calibration laboratories, instrument manufacturers, end-users and groups maintaining historical datasets of ozone concentrations.
We present the rationale for this change in the ozone-cross section, describe how it will be rolled out across Europe (including in United Kingdom through the Automatic Urban and Rural air quality monitoring Network (AURN)), and signpost the freely-available resources available to support the change.
