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Dust Definition: Saguaro West Case Study

This report examines the feasibility of a draft definition of dust to distinguish between natural and anthropogenic sources. The case study focuses on Saguaro West in Arizona and explores the characterization, estimation, and partitioning of emissions from windblown dust and agricultural activities.

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Dust Definition: Saguaro West Case Study

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  1. Dust Definition: Saguaro West Case Study Julia Lester WRAP DEJF Meeting ENVIRON International November 16, 2005

  2. BACKGROUND • WRAP’s Dust Emissions Joint Forum (DEJF) developed a draft definition of dust to discriminate between natural and anthropogenic sources of dust • WRAP sought a feasibility assessment of draft definition • Draft Feasibility Assessment Report with Protocol (May) • Case studies as examples of Protocol application • Recommended revisions of the draft dust definition, if necessary • Implementation support, as resources permit

  3. Case Studies • Several potential case studies identified • Based on latest Causes of Dust results, COHA analyses, other WRAP programs, 2 case studies identified through discussion with WRAP staff and the DEJF: • Saguaro West (SAWE) in Pima County Arizona • CoD / CoHA: 123 dust days with soil / coarse mass significant contributors to 20% worst visibility days • Salt Creek Wilderness in New Mexico • Interaction with the New Mexico SIP Pilot Project

  4. Dust Definition Categories • Feasibility Assessment Proposed 3 Categories • Anthropogenic • Natural (some sources currently not inventoried) • Mixed: Natural sources that can be anthropogenically influenced • WRAP interested in partitioning existing dust emission estimates for this category (natural vs. anthropogenic) • Identified data/method resources may be used for new or revised inventories for some sources

  5. Feasibility Assessment Protocol • Identify the purpose and goals of the analysis • Conceptual Model and rank order the dust sources in the project area by chosen criteria • Identify major Category 3 sources • Identify controls/mitigations, if desired • For major Category 3 contributors, are existing methods/databases available to characterize, estimate, and/or partition the emissions? • If not, can the necessary methods/databases be developed and at what cost? • If the answers to 5 and/or are yes, definition can be implemented

  6. Step 1: Saguaro West (SAWE) Study Purpose and Goals • Pilot-scale feasibility assessment (conserve resources for Salt Creek Wilderness assessment)

  7. Step 2: SAWE Study Conceptual Model • Conceptual Model Elements • Geographic setting • PM and visibility setting • Focus of this study is worst dust days for visibility impairment • Latest CoD and CoHA results • Geological, topical, ecological, and climatological setting • Land use setting • Summary, including significance threshold

  8. Conceptual Model: CoD Information Source: CoD Report, DRI

  9. Conceptual Model: SAWE CoHA Information Source: CoHA Report, DRI

  10. Conceptual Model: Land Use Source: CoHA Report, DRI

  11. Conceptual Model: Land Use • Focus area dominated by open shrub/grass lands, with small areas of agricultural row crops and urban uses (Mining activities, if study area expanded) • Potential grazing areas not yet identified Agricultural crops 5 to 10 km SW of Saguaro West

  12. Conceptual Model: Summary • Based on the latest CoD results, case study will focus on worst dust days related to local dust sources • 135 to 225 quadrant focus, radius 20 km (local sources) • April through July have greater CM and fine soil contributions, so seasonal emissions will be reported if they exist

  13. Step 2 (cont): Initial Ranking of Sources

  14. Step 2: Initial Ranking of Sources (cont.)

  15. Step 2: Initial Ranking of Sources (cont.)

  16. Step 2/3: Initial Ranking Summary • Most relevant: Windblown dust (Category 3) • Next most relevant: Agriculture (Category 1) • If the study area was extended to 50 km, surface mining would also be included at this level • Emissions from animal movement and burrowing, or the effects of these activities on windblown dust emissions, (Category 3) • relevance cannot be assessed without further investigation • Results of Step 5 may indicate the need to re-order the source rankings

  17. Step 5: Resource Availability for Category 3 Sources • For major Category 3 contributors, are resources available to characterize, estimate, and/or partition the emissions? • Data and Model Resource Identification • Dust source characterization • Site-specific dust emission estimates • Emission partitioning

  18. Step 5: Resource Identification • 32 data/model resources identified for study area (many are in the process of development or revision)

  19. Step 5: Dust Source Characterization, Emission Estimation, and Partitioning • Most significant SAWE source (windblown dust) resource analysis

  20. Step 5: Dust Source Characterization, Emission Estimation, and Partitioning • Potentially major SAWE source (animal movement, impact of burrowing animals) resource analysis

  21. Step 5: Emission Estimates • Windblown Dust • Current windblown dust model estimates • Spatially and temporally-resolved • Specific windblown sources considered: • Agricultural lands • Grasslands • Shrublands • Barren lands

  22. Agricultural Emissions

  23. Grasslands

  24. Shrublands

  25. Barren Lands

  26. Step 5: Emission Summary • Shrublands dominant • Grasslands contribute with a significantly lesser contribution from barren lands • Agricultural sources in study area appear not to be inventoried • Based on current inventory evaluation for non-windblown sources in Pima County: • Ag tilling and mining operations ~ 500 tpy PM10 each • Unpaved roads contribute ~4500 tpy; prevalence in study area unknown but considered low • Animal movement, burrowing emissions unknown

  27. Step 5: Category 3 Partitioning • For windblown dust from shrublands, are there areas that are anthropogenically disturbed or impacted? • Reviewing grazing databases • Searching for unpaved road databases • If anthropogenic influences identified, partition based on: • Level 1: areal extent • Level 2: comparison to reference natural area

  28. Next Steps • Study area finalization • Resolve inventory discrepancies • Attempt to assess potential relevance of animal-related emissions or impacts • Partition scrubland emissions • Assess dust definition feasibility • Finalize draft SAWE Case Study report by end of year • Begin Salt Creek Wilderness Case Study

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