Ozone Monitoring Issues & Opportunities - II Ozone Transport Commission MANE-VU Fall Meeting November 19, 2014 Crystal City, VA Will Ollison 1220 L Street, NW Washington, DC

Recommendations EPA should allow elevation adjustments to O 3 design values (DVs) to account for population dose, as they presently do for PM DVs, to reduce over-regulation of elevated (> 1000 feet) locations Similarly, EPA should allow inlet height DV adjustments to 2 meters, within the 2-15 meter inlet height limit, to account for typical outdoor breathing zone heights EPA should facilitate NO-scrubber upgrades of the existing compliance UV monitor network to reduce network positive interference bias 1220 L Street, NW Washington, DC

Compliance with PM NAAQS PM 2.5/10 Compliance Addresses Altitude Effects 40 CFR Part 50, Appendix L, Section 2.2: Each filter is weighed…before and after sample collection to determine the net gain due to collected PM2.5. The total volume of air sampled is determined by the sampler from the measured flow rate at actual ambient temperature and pressure and the sampling time. The mass concentration of PM2.5 in the ambient air is computed as the total mass of collected particles in the PM2.5 size range divided by the actual volume of air sampled, and is expressed in micrograms per cubic meter of air L Street, NW Washington, DC

O 3 Risk Assessment (EPA- 452/R , August 2014) “The controlled human exposure studies drawn upon for this lung function risk assessment were conducted at low altitudes (< 600 feet). It is not known whether it is more appropriate to use a mass concentration (µg/m³) or a mixing ratio concentration (ppm) at higher altitudes where the barometric pressure is lower…if in fact mass concentrations are the appropriate exposure metric, then the lung function responses in a high-altitude city such as Denver (5300 feet) could be overestimated by about 15%.” (p. 6-8) 1220 L Street, NW Washington, DC

High Elevation O 3 Monitors ( > 1000 feet) ● 14,100 ft DV cut 28 ppb ● ,000 ft DV cut ppb ● ft ● ft DV cut ppb ● ft DV cut ppb ● ft DV cut 5-9 ppb ● ft DV cut 2-4 ppb 1220 L Street, NW Washington, DC

40 CFR Part 58, Appendix E to Part 58 – O 3 Inlet Height “ The probe…must be located between 2 and 15 meters above ground level for all O 3 …monitoring sites …at least 1 meter vertically or horizontally away from any supporting structure, walls, etc…[and] located on the [prevailing] windward side of the building during the season of highest concentration potential for the pollutant being measured.” 1220 L Street, NW Washington, DC

O 3 Monitor Inlet Heights Above Grade 1220 L Street, NW Washington, DC

Quarterly O 3 Gradient by Monitor Inlet Height AGL(m) 1220 L Street, NW Washington, DC

Altitude/Inlet Height-Estimated 75 ppb/2 meter Equivalent D Vs Altitude > MSL (m) Altitude Adj. Eqv. DV (ppb) Inlet Height AGL (m) Inlet Height Eqv. DV (ppb) L Street, NW Washington, DC