Presents:/slides/greg/PSAT_ ppt Implementing PM Source Apportionment (PSAT) in CAMx Greg Yarwood, Ralph Morris and Gary Wilson ENVIRON International Corporation Novato, CA National RPO Modeling Meeting Denver, Colorado May 24-25, 2004

Presents:/slides/greg/PSAT_ ppt Outline Introduction Update on approach Initial results Questions (mine and yours)

Presents:/slides/greg/PSAT_ ppt Implementing PSAT in CAMx4 Conceptual design completed, but “living document” (needs update) Similar to OSAT > OSAT has 4 tracer classes for ozone > PSAT has 36 tracer classes for ozone, sulfate, nitrate, ammonium, SOA, primary, mercury > Computational burden if all 36 tracer classes are required every time PSAT design revised so that pollutant tracking can be selected at run time > e.g., just sulfate/nitrate/ammonium; just mercury, etc.

Presents:/slides/greg/PSAT_ ppt PSAT Tracer Classes SULFATE - 2 classes > SO2 = SO2 (i.e., tracer SO2 tracks model species SO2) > SO4 = PSO4 (i.e., tracer SO4 tracks model species PSO4) NITRATE - 7 classes for nitrate and ammonium > RGN = NO + NO2 + HONO + NO3 + N2O5 > TPN = PAN + PNA (SAPRC has several PANs) > NTR = NTR (RNO3 in SAPRC) > PN3 = PNO3 > HN3 = HNO3 > NH3 = NH3 > PN4 = PNH4

Presents:/slides/greg/PSAT_ ppt PSAT Tracer Classes (continued) SOA - 14 classes for secondary organics > ALK = PAR > ARO = TOL + XYL > CRE = CRES > TRP = OLE2 > CG1 = CG1 and PS1 = SOA1 > CG2 = CG2 and PS2 = SOA2 > CG3 = CG3 and PS3 = SOA3 > CG4 = CG4 and PS4 = SOA4 > CG5 = CG5 and PS5 = SOA5 Required CAMx modification to split old CG3/SOA3 into CG3/SOA3 and CG5/SOA5 Delete SOA yields from Alkenes because > Uncertain and insignificant

Presents:/slides/greg/PSAT_ ppt PSAT Tracer Classes (continued) PRIMARY - 6 classes > PEC - PEC > POC - POA > PFC – FCRS > PFN - FPRM > PCC - CCRS > PCS - CPRM MERCURY - 3 classes > HG0 - HG0 (elemental gaseous mercury) > HG2 - HG2 (reactive gaseous mercury) > HGP - HGP (primary particulate mercury)

Presents:/slides/greg/PSAT_ ppt Status of Implementation Fully implemented in all CAMx modules for all tracer families (O3, SO4, NO3, SOA and primaries) Successfully tested for all tracer families to assure mass conservation with host model Currently in evaluation phase against “zero- out” modeling Currently evaluating “how low you can go” with PSAT/OSAT Results for SO4 follow

Presents:/slides/greg/PSAT_ ppt Source Regions and Point Sources for PSAT Versus Zero-Out Test Runs Four hypothetical point sources located in each of the four eastern US RPOs run with large and small Emissions

Presents:/slides/greg/PSAT_ ppt Hypothetical Point Source Parameters Stack Height = 500 feet (152.2 m) Stack Diameter = 17 feet (5.2 m) Exit Velocity = 100 feet/sec (30.5 m/s) Exit Temperature = 265 F (402 K) Large Source > NOx = 164 TPD (~60,000 TPY) > SOx = 848 TPD (~310,000 TPY) Small Source (= Large/1000) > NOx = TPD (~60 TPY) > SOx = TPD (~310 TPY)

Presents:/slides/greg/PSAT_ ppt SO4 -- PSAT versus “Zero-Out” MRPO Large Source -- Episode Average

Presents:/slides/greg/PSAT_ ppt SO4 -- PSAT versus “Zero-Out” MRPO Small Source -- Episode Average

Presents:/slides/greg/PSAT_ ppt SO4 -- PSAT versus “Zero-Out” MRPO Large Source – Max Hourly

Presents:/slides/greg/PSAT_ ppt SO4 -- PSAT versus “Zero-Out” MRPO Small Source – Max Hourly

Presents:/slides/greg/PSAT_ ppt SO4 -- PSAT versus “Zero-Out” MANE-VU Small Source – Max Hourly

Presents:/slides/greg/PSAT_ ppt Sulfate Comparisons for PSAT Good agreement for extent and magnitude of sulfate impacts between PSAT and zero-out > Comparing the outer plume edge is a stringent test Zero-out impacts tend to be smaller because oxidant limited sulfate formation distorts the zero-out measure of sulfate impacts Zero-out impacts of Small Source noisy due to noisy ISORROPIA numerics > Saw same noisiness in VISTAS CMAQ mass conservation patch sensitivity test Run times look very good > efficiency for sulfate >50 relative to zero-out

Presents:/slides/greg/PSAT_ ppt Oxidant Limiting Case for Sulfate PSAT result is more reasonable than zero-out

Presents:/slides/greg/PSAT_ ppt How low can you go? What is the smallest source that can be tracked using PSAT/OSAT and using the brute force method? Compare Large and Small Source Impacts

Presents:/slides/greg/PSAT_ ppt So, how low can you go? Conducted preliminary experiments reducing the magnitude of an SO2 source by 1000 > Differences between PSAT and zero out due to oxidant limitation seem more apparent for smaller source > Noise shows up in the zero out result Finite precision limits resolution of small impacts Numerical noise from model components comparable to some real impacts Reasons to suspect ISORROPIA as a source of numerical noise. Likely due to the nature of the calculation rather than any specific limitation within ISORROPIA.

Presents:/slides/greg/PSAT_ ppt Equilibrium Question Should HNO3/PNO3 tracers reach full equilibrium every time step? > Full equilibrium will mean that HNO3 and PNO3 have the same source apportionment > Unclear what happens in real world > Host model assumes equilibrium; brute force tests will behave as if full equilibrium exists. Therefore, initial PSAT implementation also assumes full equilibrium Same question for NH3/NH4 and CG/SOA pairs PSAT and TSSA differences?

Presents:/slides/greg/PSAT_ ppt Potential Uses for PSAT Diagnostic Testing and Evaluation > Where does PM come from? > Role of biogenics, background, other sources > Other? Source Culpability Assessment > State Contributions (e.g., CAIR/IAQR) > BART or other source Contributions Control Strategy Design > Rank Source Contributions > DDM also useful

Presents:/slides/greg/PSAT_ ppt Modeling Options for Proposed BART Rule Two roles for modeling in proposed BART rule > Does a potential BART-eligible source contribute to visibility impairment at a Class I area (max 24-hr) > What is degree of visibility improvement due to BART controls at a specific facility Do BART controls result visibility improvements of > 0.5 dV averaged across 20% worst modeled days Once a facility is BART-eligible, then all visibility precursor species must be considered (SOx, NOx, PM and VOC) > For most sources SO4 and NO3 will be primary pollutants of interest (SOx and NOx emissions)

Presents:/slides/greg/PSAT_ ppt Modeling Options for Proposed BART Rule CALPUFF – Lagrangian non-steady-state Gaussian puff model with simplified parameterized chemistry Advantages > Simple integrated modeling package w/ GUIs available > Computationally efficient for a few sources > EPA guideline model for > 50 km and PSD pollutants (SO2, NO2 and PM) > Mentioned in proposed BART rule Disadvantages > Chemistry incorrect and out of date (1982) > SO4 and NO3 estimates likely not accurate and reliable

Presents:/slides/greg/PSAT_ ppt Modeling Options for Proposed BART Rule SCICHEM – Second Order Closure Lagrangian non- steady-state model with full chemistry – requires 3-D fields of concentrations Advantages > Treats full nonlinear chemistry > Less computationally demanding than a photochemical grid model (PGM) for a few sources Disadvantages > Not easy to use and not widely used > Uncertainty in applicability, hasn’t been demonstrated for this type of application > Need 3-D fields without BART source(s) > More computationally demanding than CALPFF

Presents:/slides/greg/PSAT_ ppt Modeling Options for Proposed BART Rule CMAQ – One-atmosphere photochemical grid model Advantages > Full chemistry > Will be set up for 36 km inter-RPO grid and several RPO 12 km grids Disadvantages > Coarse grid resolution (36/12 km) and one-way grid nesting limit ability to resolve point sources and get correct chemistry (Plume-in-Grid may help) > How to get single source impacts: > Zero-out? > TSSA Source Apportionment? > Computationally demanding

Presents:/slides/greg/PSAT_ ppt Modeling Options for Proposed BART Rule CAMx – One-atmosphere photochemical grid model Advantages > Same as CMAQ > Two-way nesting and flexi-nesting can better resolve point source plumes > PSAT may be useful Disadvantages > How to get single source impacts: > Zero-out? > TSSA Source Apportionment? > Computationally demanding

Presents:/slides/greg/PSAT_ ppt Modeling Options for Proposed BART Rule One potential approach using CAMx/PSAT Address each state one at a time Center 12 km modeling grid over state to include all key nearby Class I area Develop BCs from 36 km Inter-RPO grid 2002 run Add 4 km flexi-nest over state of interest Base Case run and zero-out all BART-eligible sources to identify most important visibility species (i.e., SO4 and NO3) Apply PSAT with ~30 BART-eligible facilities as separate source groupings Post-process to estimate each BART-eligible facility’s visibility impacts at Class I areas