WRAP Technical Comments concerning the EPA PM NAAQS proposal of January 17, 2006

DRAFT February 21, 2006 DRAFT

Summary: The Western Regional Air Partnership has several concerns and suggestions with regard to the proposed changes to the PM NAAQS related to its mission to help western states and tribes achieve reasonable progress toward the national visibility goal and implement the Regional Haze Rule. Specifically WRAP has the following comments.

  1. WRAP believes that a secondary standard for the PM2.5 NAAQS is necessary to protecturban visibility, as was considered but not included in the proposal,and will provide the additional benefits of reduced haze levels in many proximate and distant downwind federally-protected areas by further reducing emissions that are transported out of western urban areas. EPA should modify the proposal to include nationally-applicable secondary standards as recommended by CASAC,for a short-termmaximum value of 20μg/m3 to 30μg/m3 to reduce urbanas well as remote area haze levels.
  1. WRAP is concerned that the rationale for limiting the PMcoarse NAAQS to urban areas is problematic. WRAP believes that the EPA assertion that PMcoarsein rural areas are composed of benignmaterials is unfounded/not well-founded. Limited compositional analysis using the IMPROVE network PM10 filters and other western monitoring programs show PMcoarseto be composed of complex mixtures of components that vary regionally and are not necessarily benign. The highest concentrations of coarse mass are in areas where playas and terminal lakebeds that are naturally enriched with soluble salts and heavy metals are the principal emission sources. EPA should modify the proposal to make the PMcoarse NAAQS and the supporting monitoring networks applicable to rural and urban locations across the nation, not just in large population centers.
  1. The collective experience of WRAP memberswith PM monitoring since the inception of the federal Clean Air Act tells us that the recently proposed monitoring plan for PMcoarseis short-sighted and inappropriate because it would restrict monitoring to urban areas and does not include speciation. PMcoarse is known to travel hundreds of kilometers without significant loss. Without a national network that monitors PMcoarse to assess regional events and without speciated PMcoarse to aid in assessing the source types and health threat, chances of ever having an adequate understanding of the PMcoarse impacts will be severally hampered. EPA should modify the proposal to endorse the use of IMPROVE Network PMcoarse monitoring and to expand its capabilities to include routine speciationso that it would be the rural counterpart to the urban monitoring conducted by state and local air agencies.Include charts from Lydia Wegman’s presentation and map of IMPROVE and IMPROVE protocol sites.
  1. WRAP is concerned that the proposal to both eliminate the PM10 NAAQS and replace it with an urban-only PMcoarse standard, which includes exemptions for agricultural and mining emissions, will result in the removal of current and planned emission control measures for substantial primary PM source activities throughout the western U.S. Progress in meeting the regional haze goals for many western Class I areas would be jeopardized if dust contributions, which are already substantial in some areas, were to increase due to loss of a federal standard and the resulting backsliding. EPA should promulgate a 24-hour PMcoarse secondary NAAQS that would apply nationwide with a 98th percentile standard in the range from 50μg/m3 to 135μg/m3and with no exemptions for any source type or industry.

Documentation: This section briefly documents rationale for thefour numbered recommendations summarized above. Some of the information supports more than one of the recommendations.

Visibility impairment is caused by both PM2.5 PMcoarse (supports recommendations 1 and 4)

Light extinction effects of PM have been known for many decades through laboratory and field measurements, and are precisely predicted by Mie Theory calculations. The EPA “Guidance for Tracking Progress Under the Regional Haze Rule” includes an algorithm used to estimate haze levels for the Regional Haze Rule that has both PM2.5 and PMcoarse terms. PMcoarse is not as efficient on a per unit mass concentration basis as the various PM2.5 components, but at some locations and times the high concentrations of PMcoarsecompared to the PM2.5makes PMcoarse the single largest contributor to haze. This can be seen in the map in Figure 1 that shows the fraction of IMPROVE samples where dust contribution to light extinction is the largest of component (other components include sulfate, nitrate, organic mass and black carbon). In this map dust includes light extinction from PMcoarse plus PM2.5 soil, but the PMcoarse is generally 80% to 90% of the dust extinction.

Figure 1. Percentage of IMPROVE sample days between 1997 and 2002 when haze from dust (coarse mass plus fine soil) is the largest component.

The Regional Haze Rule is particularly concerned with the 20% worst haze days based on monitoring data. Figure 2 shows that the PMcoarse contributes substantially at SaguaroNational Park(near TucsonArizona and typical of a number of southwestern class I areas). The worst days in these stacked bar plots are labeled with a W at the top. This plot shows that PMcoarse (light gray at the top of the bars) is a major contributor on most of the worst haze days. Similar plots can be seen for many federally protected areas in the southwestern U.S. by using the composition tool on the VIEWS web site at:

Figure 2. Stacked bar plots showing the six components of light extinction for SaguaroNational Park in Arizona.

A more restrictive nationally-applicable secondary PM2.5 NAAQS for urban visibility leading to urban emissions source reductions will have beneficial effects on proximate downwind areas with federal visibility protection (supports recommendation 1)

Western metropolitan areas such asthe Colorado Front Range (Denver and other cities) and the Phoenixarea have adopted urban visibilityindices[1],[2] because former and current secondary PM NAAQS do not protect scenic views and welfare effects within and across their urban regions. Federally–protected Class I areas are contiguous and/or proximate to a large number of metropolitan areas in the West, see for example Class I areas proximate to the Phoenix and Tucson urban areas.

Figure 3. Arizona state map showing the proximity of visibility-protected Class I areas to the Phoenix and Tucson metropolitan areas.

WRAP has prepared emissions analyses for 50 kilometer buffer zones around western Class I areas. See the example of SaguaroNational Park’s West Unit contiguous to the Tucson urban area. Emissions in the Tucson area are important contributors to the visibility impairment observed at SaguaroNational Park. Therefore a secondary PM2.5 NAAQS set between 20μg/m3 and 30μg/m3 to reduce urban haze would result in improved haze in nearby class I areas.

Near Emissions Project Home Page

The maps and data on this site are intended to illustrate the general landscape of emissions in and near WRAP Class I areas. For purposes of this illustration, "near" is defined as a 50 km area surrounding the borders of the Class I areas. Because in several cases areas are adjacent and have similar characteristics, some areas are analyzed and displayed together as a single group. There are 82 groups representing 117 areas. Start here to review maps and tables for a particular Class I area.
All emissions are derived from WRAP emission databases for the year 1996. Their spatial allocation to the analysis areas, however, are based on several data sets (e.g., population density, land use/cover, etc.) which span a few different years over the 1996 period. Additional details on the methods and data sources can be obtained by clicking on the "About" links on other pages within this site.
A survey of local officials in each Class I group was conducted to ensure reasonableness of the data and to identify activities, trends, and proposed projects which may affect emissions but which may not be apparent in the emission databases. Results of this survey are available upon request.

Figure 4. Map showing that the Tucson metropolitan area is within 50km of the western unit of SaguaroNational Park.

Table 1. Emissions within 50km of the West Unit of SaguaroNational Park.

1996 Emissions (tons) Near WRAP Class I areas
Group 54: Saguaro (West)
Source Category / VOC / NOx / SO2 / PM10 / PM2.5 / NH3
Point Sources / 189 / 8,147 / 2,805 / 5,124 / 942 / 2
Area Sources (excluding windblown dust) / 18,978 / 4,117 / 387 / 7,617 / 2,740 / 1,847
Residential Wood Combustion / 478.2 / 30.6 / 4.4 / 298.0 / 298.0 / 0.0
Other Fuel Combustion / 55.3 / 3,950.4 / 348.9 / 89.6 / 54.7 / 10.0
Industrial Processes / 10.7 / 0.0 / 0.0 / 714.6 / 170.9 / 0.0
Construction Dust / 0.0 / 0.0 / 0.0 / 4,284.5 / 1,428.2 / 0.0
Solvent Utilization / 14,138.7 / 0.0 / 0.0 / 0.0 / 0.0 / 0.0
Petroleum Storage and Transport / 3,509.6 / 0.0 / 0.0 / 0.0 / 0.0 / 0.0
Waste Disposal and Recycling / 785.4 / 136.1 / 34.1 / 557.6 / 469.9 / 149.6
Agricultural Activities (except burning) / 0.0 / 0.0 / 0.0 / 1,672.5 / 318.6 / 1,687.6
Fires / 2 / 1 / 0 / 4 / 4 / 0
Management Fires / 2.1 / 1.0 / 0.3 / 4.3 / 3.7 / 0.2
Wildfires / 0.0 / 0.0 / 0.0 / 0.0 / 0.0 / 0.0
On-Road Mobile Sources / 22,143 / 19,574 / 354 / 2,185 / 827 / 455
Light-Duty Vehicle Emissions / 20,821.5 / 13,053.8 / 258.7 / 250.6 / 191.4 / 441.7
Heavy-Duty Vehicle Emissions / 1,321.3 / 6,520.0 / 95.8 / 355.3 / 332.2 / 13.0
Fugitive Dust - Paved Roads / 0.0 / 0.0 / 0.0 / 660.0 / 165.0 / 0.0
Fugitive Dust - Unpaved Roads / 0.0 / 0.0 / 0.0 / 919.2 / 137.9 / 0.0
Off-Road Mobile Sources (excluding airports and commercial marine vessels) / 6,400 / 8,116 / 806 / 558 / 513 / 40
Lawn & Garden Equipment / 4,956.4 / 546.8 / 48.9 / 149.4 / 137.5 / 10.6
Recreational Equipment / 160.7 / 7.0 / 0.6 / 0.8 / 0.7 / 0.2
Commercial and Industrial Equipment / 667.8 / 909.5 / 67.3 / 63.0 / 58.1 / 18.3
Construction and Mining Equipment / 405.2 / 1,956.1 / 270.5 / 212.6 / 195.5 / 3.7
Agricultural Equipment / 18.7 / 105.8 / 13.2 / 16.3 / 15.0 / 0.2
Recreational Marine Vessels / 0.0 / 0.0 / 0.0 / 0.0 / 0.0 / 0.0
Locomotives and Railroad Equipment / 190.8 / 4,591.0 / 405.9 / 115.7 / 106.4 / 7.1
Logging Equipment / 0.0 / 0.0 / 0.0 / 0.0 / 0.0 / 0.0
Total / 47,711 / 39,955 / 4,353 / 15,488 / 5,026 / 2,344

PMcoarse concentrations are regionally highest in areas impacted by suspended dust from certain desert playas that are enriched in salts and heavy metals that cannot be assumed to be benign. Regions with substantial agricultural dust emissions do not exceed the annual 98th percentile level proposed for the urban only standard. (supports recommendations 2, 3 and 4).

PMcoarse data from the IMPROVE Network for 2002 through 2004 were used to determine the highest annual 98th percentile values for each site. The mean values of these are shown in Figure 5. This shows that the region of highest coarse mass is in southern NM and west TX.

Table 2 shows the sites with the largest three-year mean of annual PMcoarse 98th percentile concentrations. None of these sites would violate the proposed PMcoarse NAAQS. The five highest concentrations are at sites influenced by suspended dust from desert playas and those in or near urban areas. The Cherokee Nation site with a mean 98th percentile concentration of 41ug/m3 is the highest is in an agricultural area. Again, none of these sites exceed the proposed urban PMcoarse standard of 70μg/m3.

Figure 5. Map of the average 2002-0498th percentile PMcoarse concentration values for the IMPROVE Network sites.(prettier map to follow)

Table 2. PMcoarse 98th percentile concentrations for sites with three year mean values above 30μg/m3.

Site / State / 2002 / 2003 / 2004 / Mean / Max
GuadalupeMountainsNP / TX / 41.72 / 109.00 / 56.71 / 69.14 / 109.00
Birmingham / AL / 54.51 / 54.51 / 54.51
Phoenix / AZ / 57.18 / 55.00 / 35.08 / 49.09 / 57.18
SaltCreek / NM / 39.89 / 73.75 / 24.67 / 46.10 / 73.75
Douglas / AZ / 43.63 / 43.63 / 43.63
CherokeeNation / OK / 32.23 / 50.77 / 40.21 / 41.07 / 50.77
VirginIslandsNP / VI / 37.44 / 39.12 / 43.63 / 40.06 / 43.63
SaguaroWest / AZ / 34.17 / 58.95 / 22.92 / 38.68 / 58.95
ElDoradoSprings / MO / 54.78 / 35.35 / 25.43 / 38.52 / 54.78
QueenValley / AZ / 31.08 / 55.02 / 27.87 / 37.99 / 55.02
DomeLandsWilderness / CA / 36.07 / 28.39 / 41.30 / 35.26 / 41.30
WalkerRiverPaiuteTribe / NV / 30.75 / 37.20 / 33.98 / 37.20
CedarBluff / KS / 48.56 / 29.23 / 23.61 / 33.80 / 48.56
SanGabriel / CA / 65.11 / 18.14 / 17.16 / 33.47 / 65.11
Omaha / NE / 29.70 / 34.11 / 31.91 / 34.11
DeathValleyNP / CA / 41.77 / 20.63 / 32.77 / 31.72 / 41.77
SpokaneRes. / WA / 38.68 / 34.58 / 21.58 / 31.61 / 38.68
SycamoreCanyon / AZ / 34.88 / 31.96 / 27.78 / 31.54 / 34.88
VikingLake / IA / 28.75 / 35.87 / 27.87 / 30.83 / 35.87
BlueMounds / MN / 23.80 / 38.26 / 28.47 / 30.17 / 38.26

Agricultural emissions of PMcoarse are significant and shouldnot be exempted from possible controls for their contributions to the NAAQS or regional haze. (supports recommendation 4)

Figure 6 shows a map of wind-blown dust emissions in the western U.S.developed using a model of wind suspension of dust with soil characteristics and land-use data coupled to a wind field model. The results may seem counter-intuitive in that the region of largest emissions is not the deserts of the southwest, but the agricultural regions where soil tillage and harvesting periodically disturbs and exposes bare soil to wind erosion. While the relative contributions of dust to haze are largest in the desert southwest and these locations experience some of the highest extremes (as seen in Figure 5), the absolute dust contribution to annual haze levels are larger in the areas influenced by agricultural emissions. This is clearly seen in Figure 7 that shows that the annual PMcoarse concentrations as measured by the IMPROVE network is high in the agricultural center of the country and Central Valley of California. Any exemption for agriculture emission controls for PMcoarse could adversely affect the long-term success of the regional haze rule. Blanket exemptions for mining emission controls could have similar effects on a more local scale.

Figure 6. Map of the model-estimated wind-blown dust emissions for 2002.

Figure 7. Map showing the annual PMcoarse concentration from the IMPROVE network for 2004.

A PMcoarse secondary standard set no higher than 135μg/m3and applicable nationwide is needed to prevent backsliding resulting from the rescinding of the PM10 NAAQS.

WRAP’s Dust Emissions Joint Forum recently sponsored research conducted by Midwest Research Institute on the PM2.5 fraction of PM10 emissions from fugitive dust sources (unpaved roads, agriculture, etcetera) employing a variety of soil material suspended under laboratory wind-tunnel conditions. This work is documented in a peer-reviewed project report[3] and recommended changes to the PM2.5 to PM10 ratio[4] in AP-42 (EPA’s emissions guidance document). This work shows that 80% to 90% of the PM10 is PMcoarse for fugitive emissions sources. Table 1 below from the report on proposed revisions to AP-42 shows that these values differ from currently used values in AP-42, which show a smaller PMcoarse fraction of PM10. The difference is principally due to the use of a sharper cut, ambient particle sampler instead of the cyclone samplers that were used in the measurements that were the basis of AP-42.

Using the 90% value as the basis for setting the level of a secondary PMcoarse NAAQS that would be equivalent to the current primary PM10 NAAQS of 150μg/m3 give a value of 135 μg/m3 (90% of 150 is 135). The photographs (not yet produced) show computer simulated haze conditions at Saguaro National Park under typical conditions, worst haze conditions, and typical PM2.5 conditions but with 135μg/m3, 100μg/m3, 70μg/m3, and 50μg/m3 of PMcoarse. These clearly show the added benefit for haze of having a smaller secondary PMcoarse NAAQS.

Table 3. Proposed particle size ratios for AP-42.

Fugitive dust source category / AP-42
Section / PM2.5/PM10 Ratio
Current / Proposed
Paved Roads / 13.2.1 / 0.25 / 0.15
Unpaved Roads (Public & Industrial) / 13.2.2 / 0.15 / 0.1
Construction & Demolition / – / 0.208 1 / 0.1
Aggregate Handling & Storage Piles / 13.2.4 / 0.314 / 0.1 (traffic)
0.15 (transfer)
Industrial Wind Erosion / 13.2.5 / 0.40 / 0.15
Agricultural Tilling / – / 0.222 2 / 0.2 (no change)
Open Area Wind Erosion / – / - / 0.15
Notes:
1 AP-42 Section 13.2.3 suggests using emission factors for individual dust producing activities, e.g., materials handling and unpaved roads. The WRAP Fugitive Dust Handbook recommends using a fine fraction ratio of 0.208 from a report prepared for the US EPA, Estimating Particulate Matter Emissions from Construction Operations (MRI, 1999).
2 Agricultural tilling was dropped from the 5th edition of AP-42. The WRAP Fugitive Dust Handbook recommends using a fine fraction ratio of 0.222 from Section 7.4 of the California Air Resources Board’s Emission Inventory Methodology (CARB, 2003).

References:

1

[1]Colorado Department of Public Health and Environment. Denver Metropolitan Area Visibility Standard Index.

[2]Arizona Department of Environmental Quality. Phoenix Metropolitan Area Visibility Index. 2003.

[3]Cowherd, C. and J. Donaldson. 2005. Analysis of the Fine Fraction of Particulate Matter in Fugitive Dust. Final report prepared for the Western Governors’ Association, Western Regional Air Partnership (WRAP), MRI Project No. 110397, October 12, 2005.

[4] Proposed Revisions to Fine Fraction Ratios Used for AP 42 Fugitive Dust Emission Factors by Chatten Cowherd of Midwest Research Institute for the Western Regional Air Partnership (WRAP), MRI Project No. 110397, November 7, 2005