Reference Measurement Principle and Calibration Procedure for the Measurement of Ozone in the Atmosphere (Chemiluminescence Method)

Document Headings Document headings vary by document type but may contain the following: the agency or agencies that issued and signed a document the number of the CFR title and the number of each part the document amends, proposes to amend, or is directly related to the agency docket number / agency internal file number the RIN which identifies each regulatory action listed in the Unified Agenda of Federal Regulatory and Deregulatory Actions See the Document Drafting Handbook for more details. Environmental Protection Agency 40 CFR Part 50 [EPA-HQ-OAR-2022-0007; FRL 9344-01-OAR] RIN 2060-AV63 AGENCY: Environmental Protection Agency (EPA). ACTION: Proposed rule. SUMMARY: The Environmental Protection Agency (EPA) is proposing to update the current ozone absorption cross-section to the recommended consensus-based cross-section value of 1.1329x10 − 17 cm 2 molecule − 1 or 304.39 atm − 1 cm − 1 , with an uncertainty of 0.94 atm − 1 cm − 1 . The new value is 1.2% lower than the current value of 308 atm − 1 cm − 1 , and reduces the uncertainty in the value to 0.31%. The adoption of this updated ozone absorption cross-section could result in increases in measured ozone concentrations but given the existing sources of potential variability in monitoring data, it is unlikely that there would be any consistent measurable and predictable effect on reported data. The EPA is also proposing to update the dates of publication for two references, add a new reference for the updated cross-section value, and move the figures inadvertently placed in Section 6.0 References to a new Section 7.0 Figures. DATES: Comments must be received on or before March 27, 2023. Public hearing: If requested by March 1, 2023, the EPA will hold a virtual public hearing on March 17, 2023. Please refer to the SUPPLEMENTARY INFORMATION section for additional information on the public hearing. ADDRESSES:   Comments. You may send your comments, identified …