Update on Proposed Ozone FRM Ozone Transport Commission Spring Committee Meeting April 10, 2014 Washington, DC Will Ollison 1220 L Street, NW Washington, DC

New O 3 Federal Reference Method CASAC doubts proposed NO-CL FRM, UV-SL a better choice? An April 3, 2014 EPA CASAC-AMMS presentation and other recent publications suggest that a scrubberless UV (UV-SL) method is superior to the proposed FRM nitric oxide chemiluminescent (NO-CL) method – An “absolute” FRM UV methodology complements the current U.S. O 3 compliance and global NIST/BIPM Standard Reference Photometer networks Current U.S. O 3 network UV photometers can be economically upgraded to FRM status by replacing metal oxide O 3 scrubbers with NO scrubbers L Street, NW Washington, DC

EPA Comparison of NO-CL & UV-SL Methods to FRM NO-CL versus ethylene-CL FRMUV-SL versus ethylene-CL FRM 3

GPT Scrubberless Module™ Drop-in NO-scrubbers are commercially available to convert Teledyne-API & Thermo O 3 photometers to “interference-free” (H 2 O, Hg, aromatic VOCs) O 3 monitors. 4

CASTNet & SLAMS Site O 3 Values Need Adjustment A recent O 3 network protocol review identifies a number of needed improvements (Leston, See 4/3/14 public comment at O 3 inlet height above grade can high bias O 3 values by 3-4 ppb at 10 meter rural/remote CASTNet sites compared to 3-4 meter urban/suburban SLAMS sites High altitude O 3 design values overstate 75 ppb NAAQS stringency, for example by 13 ppb in Denver compared to sea level sites, since residents respond to inhaled O 3 concentrations, not to pressure-invariant mixing ratios Use of dry ozonized zero air to assess O 3 photometer bias & precision discounts substantial sample matrix interference in current network photometers 1220 L Street, NW Washington, DC

Design Value Adjustment for Inhaled O 3 Altitude Effect City Altitude & Inhaled O 3 Effect NE City, Altitude, & DV Adjustment 1220 L Street, NW Washington, DC