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

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

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

COHA Physiographic Regions

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 r 2 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

Example fitted curve for sulfate, Cascade Region OC

Zone of Representation Cascade Range region example Average sulfate extinction on 20% worst days= Mm -1 Rep. Distance = = 139 km Sulfate contributed 37% to worst case extinction Sulfate distance when r 2 = 0.7

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

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

11 Tribes totally outside of ZoR

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

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 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)