Western Regional Ozone Issues Observations and concerns Changing perspective- not all isolated ozone issues Trends in Colorado areas Near non-attainment and excessions of the standard Transport versus local Rural sources versus urban

1995 Forest Ozone Paper Bohm, McCune & Vandetta, JAWMA, June 1995 published two papers identifying impact on rural Western Forests from transport, non-urban ozone formation or tropospheric reservoir downward mixing

Observations and Concerns Nationally, 1-hour ozone levels have declined over the past 20 years as VOC and NOx emissions have been reduced Many areas met the 1-hour standard AND…

National Trends National 8-hour ozone trends show a 14% decrease in composite 4 th maximum levels over the past 20 years However: –Trends over the past 10 years show a 4% ozone increase while a subset of meteorologically adjusted sites show no change even with decreasing VOCs

Regional Trends The Pacific Southwest – LA area- indicates substantial improvements in 8- hour ozone over the past twenty years BUT- the Pacific Northwest indicates ozone levels are increasing AND- trends at individual more rural locations show mixed trends over the past ten years

Western Emissions and Non- Attainment Texas and California rank #1 and #2 for total Western Emissions of VOC’s and NOx There are only two other Western N/A areas with substantially lower VOC and NOx emissions Other Western States have comparable emissions but meet the standards

Emissions & Rank of Western States With Ozone Issues StateWestern Rank 1996 NEI NOx TPYVOC TPY Texas12,202,9351,451,353 California21,556,3741,213,033 Arizona3/5 463, ,039 Colorado4/6 425, ,347 New Mexico 6/8 324, ,835

Western Non-Attainment Areas

Threatened Non-attainment Areas of Colorado

Rural Ozone VS Urban

Other rural trends?

Denver High Station Trend

Denver Core Site Trend

Denver North South Trends

Episodes and Background Urban Denver ozone once thought to be isolated to the dynamics of front range emissions, topography and photochemistry Current analysis indicates episodes of high ozone can be a combination of long range transported ozone mixed with rural and urban components

Back Trajectory Analysis- AQI 119- NOAA Air Resources Laboratory

Emissions VOC and NOx Front range emissions have a substantial local source component Statewide VOC emissions are dominated by biogenic sources Future emissions are expected to decline only slightly

2002 Denver Metro and Statewide VOC EI with Biogenic Emissions

Existing O&G Sources in the San Juan Basin 22,500 existing sources- VOC’s and NOx 11,000 proposed new O&G sources

New Mexico Ozone Task Force Only other Early Action Compact area of the West Recognized signs of possible ozone problems Establishes a stepping stone for coordination of multi-State or Interstate ozone issue