Tribal Causes of Haze Representativeness Assessment Phase I

1. Tribal Causes of Haze Representativeness Assessment Phase I Mark Green, Alissa Smiley, and Dave DuBois Desert Research Institute

2. Overview • Goals: 1) determine whether each tribal area in the western US is “represented” by an IMPROVE monitor; 2) which IMPROVE monitors, if any, represent each tribal area • Use physiographic regions to group sites in similar areas • Consider correlation coefficients by chemical species between sites in each region and how they decay with distance to establish “representative distances” • Fit correlation versus distance curves for each region with at least 4 sites

3. Task 2 WRAP tribal areas in blue and IMPROVE sites as yellow dots

4. COHA Physiographic Regions

5. Zone of Representation • For each major component (sulfate, nitrate, OC, EC, fine soil, CM) plot correlation versus distance between sites- define zone of representation as distance where correlation coefficient falls to 0.7 • r=0.7 somewhat arbitrary, but gives r2 of 0.49, so about one-half of variance at that distance can be explained by variation at IMPROVE site • This gives a regionally representative distance for each aerosol component • Each aerosol distance was then weighted by its contribution to light extinction on worst visibility days • Weighted distances summed over all aerosol species to create a regional representative distance

6. Example fitted curve for sulfate, Cascade Region OC

7. Zone of Representation • Cascade Range region example Average sulfate extinction on 20% worst days= 15.57 Mm-1 Sulfate contributed 37% to worst case extinction Sulfate distance when r2 = 0.7 Rep. Distance = 94 + 0 + 34 + 5 + 6 + 0 = 139 km

8. Zone of Representation • Regional ZoR ranged from 91 km in Colorado Plateau to 210 km in Northern Great Plains • For those regions with less than 4 aerosol monitoring sites, we used a regional ZoR of 150 km • For each region, we calculated the distance from each tribe to each IMPROVE site • If the distance to the nearest IMPROVE site was greater than the regional ZoR, then we colored the area red • Portions of many tribes outside of regional ZoR • Total of 11 tribes entirely outside of regional ZoR

9. Example: Central Rocky Mountains Region • Red dots denote IMPROVE sites • Blue circles-140 km aerosol zone of influence • Purple circles around non-represented tribal area (Uintah & Ouray) • 17 Class I Areas

10. 11 Tribes totally outside of ZoR

11. Monitoring Recommendations • For those 11 tribes not represented we did a regional scale examination to determine if a new aerosol sampling site is warranted • We determined that 6 new monitoring sites would satisfy our criteria • Spirit Lake, ND • Sisseton-Wahpeton Sioux, ND/SD • NW Band of Shoshoni Nation, north of Salt Lake City • Pueblo of Acoma, NM • Quechuan and Cocopah near Yuma, AZ • Northern NV and SE Oregon

12. Tribal representative analysis Phase 1 summary • Method gives a representative distance based on objective criteria that weights importance of each chemical compound to light extinction • Representative distances ranged from 91-210 km • All but 11 tribal areas had representative IMPROVE monitors • Several regions had fewer that 4 IMPROVE monitors and were assigned representative disance of 150 km • Did not include effects of intervening terrain or emission sources (phase 2 did)