UnitedStates Environmental Protection Agency 

## AIR OfficeofAllQuality PlanningandStandards ResearchTrianglePark,NC 2n11 EPA-450/4-91-015 May1991**~** • I ' J

# 8~E

# PA CRITERIAFORASSESSINGTHEROLE

.

# .

.

# -- 

# OFTRANSPORTEDOZONE/PRECURSORS INOZONE**NOt~ATTAINMENT**

# AREAS

# ..aNVIHUI'\MiNlM PROTEC'T't8M 

### AGiNCY 8AU.AS, 1111&1 

# liBRARY

CRITERIA FOR ASSESSING THE ROLE OF TRANSPORTED OZONE/PRECURSORS IN OZONE NONATTAINMENT AREAS

MAY 1991

U. 

## s. Environmental Protection Agency Office of Air Quality Planning and Standards Technical Support Division Research Triangle Park, NC 27711TABLE OF CONTENTS

LIST OF FIGURES 

# . . .

# .. . . . . . . . . . iii LIST OF TABLES iv 1.0 INTRODUCTION

. 1 2.0 ROLE OF TRANSPORT DETERMINATIONS IN IMPLEMENTING CLEAN AIR ACT REQUIREMENTS.

. . . . . . . . . . • . . . . 3

3.0 2.1 2.2 Implications for Modeling and Monitoring

... CAA ModelingRequirements and Implications for Determining Transport

. . . . . .. . . CONSIDERATION OF TRANSPORT IN THE DESIGN OF CONTROL STRATEGIES

. . . . . . . . • . . . . . . . 3.1 Determining Whether an Exceedance is Primarily Due 3 4

9

to Local Emissions

. . . . . • . . • . . . . . 9 3.2 Determining Likely Contributing Areas in cases of

3.3 overwhelming Transport

. . . . . . . . . . 15 3.2.1 A Predominant source Area is Identified 16 3.2.2 No Predominant Source Area is Identified 17 Consideration of Transport in Attainment Demonstrations

. . . . . . . . . . . . . . 3.3.1 3.3.2 3.3.3 Use of Regional Scale Models Use of Monitored·Data to Estimate Model Boundary Conditions ..•..•..• Use of Modeling Procedures to Diminish Importance of Transport

. . . . . . . 18 19 23 26 4.0 MONITORING DATA FOR CHARACTERIZING TRANSPORT IN RECOMMENDED MODELS

. . . . . . . . . . . . . 31 4.1 Data Needed to Support Characterization of Transport in Models

. . . . . . . . 4.1.1 4.1.2 4.1.3 4.1.4 Trajectory Models

. . . . . . . Urban Airshed Model

. . . . . . . . . . . . Empirical Kinetics Modeling Approach

. . . . Regional oxidant Model

. . . . . . . . . . .

i 31 31 33 36 374.2 Instrumentation/Deployment 4.2.1 4.2.2 4.2.3 4.2.4 4.2.5 Winds, Other Meteorological Data

..... . Ozone

. . . . . . . . . . . . • . . . . NOX • • • • • 

### co
. NMOC

. 4.3 Quality Assurance of Monitored Data

. 5.0 SUMMARY REFERENCES CITED

ii 38 38 38 38 39 39 40 43 491

2

3 LIST OF FIGURES

Multiperiod Back Trajectory With Area Most Likely Contributing to Observed ozone Identified Portion of United States Covered By Potential ROM Applications Future Ozone Transport as a Function of Present Transport 12
21
27
4 Minimal Ozone Monitoring Network

. . . . . . . . . . . . 34



# ..

iii1 LIST OF TABLES



### Default Recommendations for Present Transported Boundary Conditions

iv 301.0 INTRODUCTION The intent of this document is to present means (i.e., criteria) for assessing the effect of transported ozone (03 ) and its precursors on 03 concentrations observed in locations not attainingtheNational AmbientAir Quality Standard (NAAQS)· for 03 • The primary purpose for making such an assessment is to foster design of control strategies which are most responsive to environmental conditions prevailing in a nonattainment area. Therefore, the criteria discussed herein address not only current conditions but future periods (after control strategies are implemented) as well. This is necessary in orderto assesswhether
a proposed control strategy is likely to be successful in meeting prescribed deadlines for attaining the NAAQS for 03 • Thisdocument isprepared inresponse to Section 184(d) of the Clean Air Act (CAA) as amended in 1990. Section 184(d) states the following: "For purposes of this section, not later than 6 months after the date of the enactment of the Clean Air Act Amendments of 1990, theAdministratorshallpromulgatecriteriaforpurposes of determining contribution of sources in one area to concentrations of ozone in another area which is a nonattainment area for ozone. Such criteria shall require that the best available air quality monitoring and modeling techniques be used for purposes of making such determinations." The remainder of the document is organized in the following
manner. Section 2 discusses why it is important to be able to characterize transport. This is done by identifying pertinent requirements in the amended Clean Air Act and by noting. how consideration of transport is a prerequisite for meeting these

1

### requirements. Because Section 184(d), as well as other portions oftheCAA, implytheneed for quantitativeestimatesof transport, modeling is recommended as the prime means for making this determination. Monitaring is needed to support and estimate performance of the recommended modeling procedures. Section 3 describes the appropriate sequence of modeling analyses for considering transport in the design of control strategies. This sequence proceeds by first noting the role of transport determinations in selectinglocations inwhichto applycontrolsto most effectively reduce 03 

### during an observed episode. Next, procedures for considering transport in order to quantify the controls needed in identified ·areas to reduce 03 

### to the level specified in the NAAQS (

### o.12 ppm) are described. Section 4 presents monitoring recommendations (criteria) for estimating transported ozone and precursors needed in the modeling analyses recommended inSection 3. Section5 summarizes identifiedmodeling andmonitoring criteria for determining contributions of transport in downwind nonattainment areas.

22.0 ROLEOFTRANSPORTDETERMINATIONS IN IMPLEMENTING CLEANAIRACT REQUIREMENTS. 2.1 Implications for Modeling and Monitoring The 1990 Clean Air Act amendments reflect a mix of ptescribed reductions of volatile organic compound (VOC) and nitrogen oxides precursors of (technology-based requirements). The Act also requires States to ensure that prescribed emission reductions are sufficient to meet the 0 3 NAAQS (air qualitymanagement requirements) inmany nonattainment areas. It is inmeetingthe Act's airqualitymanagementrequirements that properconsiderationoftransport isimportant. Thisconsideration fulfills several roles: (1) tohelp identifytheprimaryreason (i.e., transport
or local emissions) for an observed "exceedance "* of the NAAQS in
a nonattainment area, (2) to identify an upwind location(s) most likely to contribute to (and therefore the most appropriate locations to apply a set of strategies for reducing) an observed "exceedance", (3) toallowquantitativeestimatestobemade regarding reductions in 

### voc and/or NOx emissions needed in areas identified
as likely to contribute to an observed exceedance in order to remedy the exceedance, (4) to ensure and track effectiveness of promulgated control strategies, and

*In**thi~**document, the term "exceedance" isused to denote any observed daily maximum ozone concentration greater than the level specified in the NAAQS (0.12 ppm). 3(5) to assess the extent of interstate transport throughout designated Transport Regions and assess strategies for mitigating interstate transport. Useofphotochemical airqualitydispersionmodels isthe only practicalwaytomeetthethird and fifthroles identifiedabove

-- that of assessingwhether contemplated emission control strategies will be sufficientto reduce 03 to**~0.12** ppm and whether interstate transport has been reduced sufficiently to make the goal a realizable one. The roles of meteorological and air quality monitoring are threefold:(1) to provide information concerning which areas and episodes to model; (2) to provide input information to models so that they might be used to make estimates of needed emission reductions in modeled areas; and (3) to aid in evaluating the performance of selected models. 2.2 CAA Modeling Requirements Determining Transport and Implications for
The CAA amendments categorize ozone nonattainment areas into five groups. These are, in descending order of severity, extreme, severe, serious, moderate, and marginal. Air quality management-related requirements are imposed in the first four of these categories. In addition, rural transport areas, as defined in**~ection** 182(h), are subject to the same restrictions as a marginal nonattainmentarea, regardless ofthe severityofmeasured 4ozone levels, if it can be shown that failure to attain in such an
area is attributable to transport. Finally, certain small areas,
as defined in Section 185(e), may be exempted from sanctions for failure to attain the NAAQS by a prescribed date, if attainment is prevented by transport-after all local State Implementation Plan (SIP) provisions are implemented. In extreme, severe, and serious areas, use of a photochemical grid model is required to demonstrate that proposed control
measures will be sufficientto attainthe NAAQS by specifieddates. The Urban·Airshed Model (UAM) is the gridmodel recommended by the EPA for this purpose, and is expectedtobe widelyused (Morris, et al. 1990 a,b; Douglas et al. 1990; causley 1990; Tang et al. 1990). In moderate nonattainment areas, use of grid modeling is required if the area includes territory in more than one state. Otherwise, grid modeling is preferred, but the Empirical Kinetics Modeling Approach (EKMA) is also an acceptable procedure (USEPA 1989 a-c; Systems Applications, Inc., 1988; Meyer et al. 1989). Both the UAM and EKMA are regarded as "urban scale" models. That is, the modeling domain ordinarily addressed is sufficiently large to considermovement of pollutants over 12 daylight hours (e.g., 8
a.m.- 6 p.m.). Generally, this has resulted in applications over domains on the order of a couple hundred kilometers on an upwind/ downwind axis at most. However, it is possible to consider larger domains for urban grid models. Domain size is usually limited by data base management considerations and computer limitations

.


# ..

5Criteria for considering transport must address the following issues relating to use of the UAM and EKMA models. (1) Is use of one of these models appropriate for modeling the nonattainment area containingthe ozone exceedance in question? If not, what should be done? (2) What areajmodeling domain should be modeled to adequately consider the effects of a proposed control strategy on
an observed exceedance? (3) What inputs are needed to these models in order to reflect effects of transport? (4) How can the inputs needed for the urban scale models be derived? The EPA_has publishedguidance describing suitable·procedures for using the UAM and EKMA in attainment demonstrations (USEPA 1991a, USEPA 1989c). Much of the ensuing discussion regarding criteria for considering transport is drawn from these guidance documents and from Meyer, et al. 1989. Each model application is likely to have to respond to some area-specific characteristics which cannot be anticipated in general guidance. Thus, model application guidance has recommended formation of working groups consisting of representatives from each State affected in a particular modeling demonstration, appropriate US EPA. representatives and other interestedparties (USEPA 1991a). It is expected that criteria for assessing the role of transported ozone and precursors identified in this document will be treated similarly. That is, a group of general procedures are identified

6herein. It will be up to the working group responsible for developingand implementinga modelingprotocol for a specific area to adapt this general guidance for use in specific areas. It is also conceivable that special circumstances prevailing in a particular area for which a modeling protocol is being developed may warrant use of procedures which differ from those described herein. In such cases, the rationale for a different procedure must be documented and submitted to the appropriate 

### U.s. EPA Regional Office for consideration on a case-by-case basis.

7This page intentionally left blank

83.0 CONSIDERATIONOF TRANSPORT INTHEDESIGNOFCONTROL STRATEGIES In order to quantify effects of transport and to ensure that transport is appropriately considered in the design of a SIP to demonstrate attainment of the NAAQS for ozone, it is necessary to
use sophisticated, resource intensivemodelingtools. To conserve resources, itisuseful to focus modeling analysis on locations and incidents which, if remedied, would most likely result in attainment of the NAAQS. The discussion in Section 3.0 begins by describing several relatively simple tools (trajectory models) whichmaybeuseful in focusing analyseswithcomplexmodels (e.g., UAM, Regional Oxidant Model (ROM)) needed to consider transport quantitatively. section 3.0 concludes with a discussion of urban and regional scale photochemical dispersion models needed to quantify effects of transport in SIP attainment demonstrations. 3.1 Determining Whether an Exceedance is Primarily Due to Local Emissions The first step in assessing the role of transport is to determine whether transport is so overwhelming that the contribution of local emissions to an observed exceedance is relatively minor. such a case is referred to as "overwhelming transport". Procedures described in this step are useful in selecting episodes to test whether local control measures are sufficientto eliminate exceedances which are largely attributable to local emissions. Inmany cases, theremaybe anupwind/downwind gradient in observed 03 concentrations andjor man-made VOC and NOx emissJon density is much greater in the Consolidated Metropolitan Statistical Area (CMSA) or Metropolitan statistical Area (MSA) 9under consideration than in surrounding locations. In such cases it is the prerogative of those responsible for the area's modeling protocol whether to perform an ·"overwhelming transport" determination using more rigorous procedures described below. If it is decided that a rigorous overwhelming transport determination isunnecessary, the analyst shouldproceedto Section 3. 3. Failure to perform an adequate "overwhelming transport" analysis when a detailed analysis is warranted could lead to very stringent prescriptions for control of local emissions. While such prescriptions might possibly work, they may not be a particularly efficientway to eliminate an exceedance which is largely a result of transport from external sources. If an assessment of overwhelming- transport is performed, the approachgenerallyrecommendedistoperformtrajectoryanalysesto
assess the likelihood of overwhelming transport. The model ordinarily recommended for this purpose is the

## us EPA TRAJECTORY model (Meyer, et al. 1989). However, as described shortly, other trajectory models may be used if it can be shown that use of surface wind measurements alone inadequately describes transport. The EPA TRAJECTORY model uses surfacewind datato constructa back trajectory from the site of the observed exceedance, beginning at the time of the daily maximum 03 concentration observed on the day of the exceedance. There is usuallyconsiderable uncertaintyregarding the exact position of an air parcel nominally following a computed trajectory. The TRAJECTORY model incorporates this by considering
10variability inwind data noted atnearby stations. The further one progresses from the back trajectory's starting point (i.e., the
ozone monitoring site recording the exceedance) the greater this uncertainty becomes. As a result, one obtains a cone-like figure, emanating**fro~** the monitoring site, which**d~scribes** the_probable position of pollutant-laden air during periods preceding the observed exceedance. This is shown conceptually in Figure 1. Figure 1 depicts a back trajectory from a monitoring site with an observed daily maximum 0 3 concentration at 2:00 p.m. The "v1t" represent distance traveled during eachhour. The 

### 61 are measures of uncertainty whose derivation is described in Meyer et al. (1989). Significanceof the shadedareawillbedescribed shortly. The trajectory is computed using surface wind data from all National Weather Service and other suitably sited wind monitors (see USEPA, 1987) within 160 km of the most likely computed position of an air parcel following the trajectory at any hour. Because the nighttime surface layer may be very shallow and winds aloft may differ significantly from surface observations at night, TRAJECTORY may onlybe applied for daytime hours (e.g., 8 a.m.- 8 p.m.). An underlying assumption in the USEPA TRAJECTORY model application for identifying overwhelming transport is that if an airparcel correspondingwith an observed exceedance is within the nonattainment area during 8 a.m. - 12 noon on the day of the exceedance, there is a good chance that local emissions play a significant role in causing the exceedance. This assumption is
11t-' [\) V·t 5 **~t** v

0 t

Figure **~** - Multlperlod Back Trajectory With Area Most

Likely Contributing to Observed Ozone Identifiedsupported by diurnal meteorological conditions as well as by typical diurnal emission patterns for many important source categories of

## voc and NOx precursors for 03 • Thus, if all or part of the local CMSA/MSA containing or in close proximity to the site withthe observedexceedance falls within**~he** shaded area inFigure 1, it can be assumed that its emissions play a significant role in leading to the observed exceedance. As noted in Meyer et al. 1989, if the average resultant wind velocity is low, it should be assumed the local area contributes to the exceedance. If such a finding is made, the analyst can skip Step 2 in the procedure for considering transport (i.e., Section 3.2) and proceed to Step 3 (Section 3.3). If a finding of overwhelmingtransport ismade, the episode in question can be ignored in the local area's attainment demonstration unless it is not possible to identify an upwind CMSA/MSA(s) likely contributing to the observed exceedance. In this case, see the discussion in Section 3.2.2. It should be noted that it is possible for the TRAJECTORY model to yield misleading results under some circumstances. For example, if an exceedance occurs as the result of mid-morning fumigation of ozone which remains aloft overnight, it is conceivable that this is a result of transport rather than recirculated locally generated pollution. For exceedances occurring at 11 a.m., local civil time (LCT), or earlier, a trajectory model such as the Atmospheric Transport and Dispersion Model (ATAD) or the Branching Atmospheric Trajectory model (BAT) (Heffter 1980, 1983) is recommended to assess the likelihood of
13overwhelming transport. These models utilize upper air data. Prior to applying such a trajectory model, the modeling protocol working group should consider whether the exceedance is due to fumigation. Review of available diurnal mixing height information and time series analysis of**ai~** quality data may be helpful**~n** distinguishinga fumigation-inducedproblemfromoneresultingfrom photochemistry relatively early in the day. If a multiday trajectory model is used to assess likely sources of a morning exceedance, attention shouldbe given to MSA/CMSA's traversedby a swath surrounding the trajectory from 8 a.m. - 6 p.m. on the preceding day. Width of the swath is a function of uncertainty associated with the trajectory estimates. Uncertainty can be determined by a climatological review of trajectories computed under similar synoptic conditions and wind patterns. TheTRAJECTORY model generallyremainsthemodel of choice for addressingexceedancesoccurringafter 11a.m., because itutilizes
more dense surface monitoring networks and its application is confined to periods of the day when wind shear is likely to be minimized. Thus, surface winds would be more representative of flow in the mixed layer in most locations. Choice of the trajectorymodel and itsunderlyingrationalemustbedocumentedby the working group preparing a modeling protocol and is subject to review by the

## u.s. EPA. It 

### is next appropriate to consider rural transport areas, as described in CAA Section 182(h), more explicitly. Use of trajectory models, as described in the previous paragraphs, is
14generallythepreferredapproachfor confirmingthatan area, which otherwise qualifies, may be treated as a rural transport area. However, it may happen that the wind data available near such locations are too sparse to be reliable, or available trajectory models are otherwise.unsuitable. If the workipg group responsible for a modelingprotocol determinesthatavailabletrajectorymodels
are inappropriate for the purpose of identifying overwhelming transport into a proposed rural transport area, the reasons for this determination should be documented and are subject to review by the U.S. EPA. If the EPA agrees with this assessment, other methods may be used to justify treatment of a candidate geographical location as a rural transport area. An area may be treated as a rural transport area if justified by the weight of supporting evidence of two or more of the following types (1) NOx and VOC inventories are much less than those in locations where it is plausible to believe pollution may be originating, (2) a past photochemical grid modeling analysis supports the hypothesis of overwhelming transport, (3) a field study supports the likelihood of overwhelming transport, or (4) other pertinent**gu~dance** can be presented. If an area is determined to be a rural transport area, exceedances occurring therein should be considered in selecting episodes to model and in the choice of modeling domains for nearby CMSA's/MSA's. 3.2 Determining Likely Contributing Areas in Cases of Overwhelming Transport Once it is determined that "overwhelming transport" is likely, the next step is to try to establish the most likely 15predominant source(s) of an observed "exceedance". If the TRAJECTORY model is used, this is done by noting any CMSA/MSA's locatedcompletelyorpartiallywithinthe shaded area inFigure 1. If a model using upper air data is used to estimate the cause of a morningexceedance, CMSA's/MSA's**loca~ed**withina swath surrounding the trajectory during 8 a.m. - 6 p.m. of the preceding day should be identified. As noted in Section 3.1, the width of the swath is
a function of uncertainty in the trajectory path as estimated from climatology of the area with the observed exceedance. Results of applying any of the trajectory models may yield any of several outcomes: (a) one of the identified CMSA/MSA's has many more NOx
or voc emissions than any of the other identified CMSA/MSA's. (b) Several CMSA/MSA's are identified, but it is not obvious which one(s) exerts the predominant influence on transported ozone/precursors; (c) No CMSA/MSA's are identified. 3.2.1 A Predominant Source Area is Identified If the emissions of NOx or VOC in 9ne of the identified CMSA/MSA's greatly exceed those in the others, it may be assumed to be the predominant cause of the observed exceedance. In this case, the episode in question should be among those considered for modeling for this upwind CMSA/MSA. Procedures for selecting episodes tomodel withUAM or EKMA are described inUSEPA 1991a and in USEPA 1989c, respectively. If the UAM is used and the episode in question is one of those selected for modeling, the downwind
16boundary of the modeling domain for this upwind CMSA/MSA should extend beyond the monitoring site, as described in USEPA 1991a. 3.2.2 No Predominant Source Area is Identified Outcomes (b) or (c) above are possible if an exceedance is the.composite.effect of- emissions in many areas or is a result of multiday transport. Several approaches are possible if one of these outcomes occurs. First, if there are a number of such incidents, this might serve as one consideration in deciding whether to petition the EPA Administrator to establish a Transport Region in accordance with Section 176A of the CAA. Cumulative effects of SIP's in several CMSA's/MSA's or States are best simulated with regional scale models, such as the EPA ROM, (Lamb, 1983) used inconcertwithurban scalemodels. Regional models are alsotherecommendedapproachforquantifyinginterstatetransport,
as required in Transport Regions. Application of ROM and its role in assessing effects of transport will be described more fully in Section 3.3. Ifthere is a limitednumberof "unattributed" exceedances, it may be possible to address the problem without establishing a TransportRegion. Asecond approach couldbe use of an urban scale photochemical grid model, like the UAM, and a large modeling domain. The domain would encompass monitoring site(s) observing unattributed exceedances as well as the several CMSA/MSA's identified through use of trajectory methods as potential contributors to those exceedances. The episode(s) including the unattributed exceedances would be among those considered for
17simulating over the large modeling domain (USEPA, 1991a). In such cases, the effect of emissions in one or several CMSA/MSA's on air quality downwind can be assessed through model sensitivity tests. If it is not feasible to exercise either of the preceding two approaches, itwould be necessary to focus once again on the local area's attainment demonstration. As noted previously, it is not necessary to simulate effects of local controls on an exceedance which is a product of overwhelming transport. Instead, it should be treated as an "irreducible exceedance". IfEKMA isused for the local area's attainmentdemonstration, guidancewithrespectto irreducibleexceedancespresentedinMeyer et al. 1989 shouldbe followed. In essence, this requires reducing the number of incidents in which an exceedance is allowed after simulation of proposed controls. A similar procedure is recommended if a photochemical gridmodel (e.g., UAM) is used. For example, supposeguidance inUSEPA 1991apermittedonepost-control modeled exceedance. In this case, presence of one or more irreducibleexceedanceswouldmeanthata proposedcontrol strategy would no longer be acceptable if it resulted in any modeled exceedances. 3.3 Consideration of Transport in Attainment Demonstrations The preceding two sections addressed qualitative procedures for identifying location(s) most likely to be the primary cause of an observed exceedance. Once these are identified, an urban scale modeling analysis should be focused on the identified area(s) using guidance in USEPA 1991a or USEPA
181989c. An identified area is, by definition, one whose control strategiesmay significantly affectwhether an observed exceedance is eliminated. Effectiveness of controls in such an area may, nevertheless, be influenced by transport. The purpose of this ·section is_to present recommendations for considering transported
ozone and precursors in urban scale modeling used for attainment demonstrations. In attainment demonstrations, transport is considered by specifying boundary conditions for urban scale models. Approaches for doing this are enumerated below. 3.3.1 Use of Regional Scale Models Thepreferredapproachforgeneratingboundaryconditions for urban scale modeling applications is to "nest" the urban scale modeling domain within a regional modeling domain. Typical regional modeling applications consider domains on the order of 1000 km ormore on a side. Regional scalemodeling simulations are begun two ormore days priortothe period to be simulatedbyusing
a gridded photochemical model such as the US EPA's ROM. The regional model isusedto simulatebase caseboundaryconditions as well as regional**i~pact** of control strategies likelyto be applied in and between the various CMSA's/MSA's within the regional modeling domain. The procedure followed in the regional (and urban) modeling analysis is to assume past meteorological episodes correspondingwithhighozone arecharacteristicof future episodes with ozone-conducive conditions, and apply a control strategy for
some future year. Generally, the year chosen would be the year in which the CAA specifies attainment of the NAAQS should be reached.
19As noted in CAA Section 181(a), this varies according to how serious the present ozone problem is for a CMSA/MSA. Use of a gridded regional model requires a large amount of computer capacity. Further, the domain is often likely to encompassmanypolitical·jurisdictions, making itdifficulttohave
access to the requisite emission information over the entire domain. This latter problem can only be overcome if states submit point, area and mobile source information to some centralized data systemwhich canbe accessedbythe regional model. Because of the difficulties listed in this paragraph, it is recommended that the
us EPA ROM model be used as the model of choice whenever feasible. States should submitemissionsdatatotheus EPA's Aerometric Information Retrieval System (AIRS) data base (USEPA, 1989d) by November 1992, so that regional modeling efforts might make use of these estimates within the limited time allotted by the Clean Air Act. The us EPA will runROM for as many episodes and locations as
resources permit. Figure 2 depicts that portion of the United States for which itwill be possibleto runROM within the next 3-4 years. Clearly, the task of ensuring consistent data bases and strategy assumptions in regional andurban scalemodeling analyses requires extensive coordination. For this reason, whenever regional models are used, the EPA should be represented on the technical or policy work group responsible for conducting urban scale attainment demonstrations. An infrastructure exists to enable States to readily access and use the results of ROM simulations as input to their urban

201\.) ...... 99 98 97 96 ss 94 9.3 92 91 90 89 88 87 86 85 84 83 82 81 80 79 78 11 76 75 74 73 72 7t 10 69 ea 67

47 . . 47

,• •' I'' •" **'·~** I

\ .1 ... _...... **~·** ..... -

. '\ ....... •""'[ **~**

I ,, ·--

... ··- ,_., .. .... **.-[..~** '-- .

..... )-"".... ·-

.... . ............ , \'' **r···'·~** .. , .. _ **-~~** .......... ;J; --\

( "· ' •• , • A , .... **~** ....,, 't

.. I ;' • • (, **···"~ ~**  ....

( I ,) I ( .... \ :L ..

·'ll ?IJ ) '> ',\ . ir -4-.,

•. (/ I . 1-\ . •. ) / 1 At\ 1\tt•'

\ I (. . .... **~** ... • . },.,J.,..

•,\ (/'' .•. **-~·-** -·-\ ,.:' 'i,. """. + «

,... .. ........ " ......... \ . J /' ..l f

< i' ./ ( __ c-·· - ...... · · v 1 .f. 4.3

. / \ "\ '""." ........ "........ **~** .. .---- ...... **c.;-·-~)** '}

\ MIDWEST " j·' ,. .... **~** ·

. ) . . , •' -./"-- _ ..... ··"!...... ......... .......... ""' ... , Jl'\ '

) ' ,_.I"'"'"''""""' **["'"''-~** ..... **'.~** \ **•'~**

\ . . t ... . ... ..;::....... .... .. . ..,. .../-1: • **~A** "'

\ ) / ......... .., .. ..qy

(\ "" ............... '\• ) {. 1.:.--

\ { ;)

" . ""·-;\ ' . ·--·-l"""" ",. -·. . -·\"\·····

\ ··... . ,...... ...../'/· } **·~**

... \... **~'\** _( I 1 •• ''1

l ) r· -

........ "'·· ./ ;·.../'' l .l · **-~**

l... / , t '\\r•v. .,

., ( , ... r-- -.:: ·11

\ ' **···~** . . -s."' ........ /"'\.. ........ **..~-··:** ... **~·** r NORTHEAST

:J -

.................. **-·--~--** ·---- -

." ............. '"''") ,i'""""""' . ---- -.

, , ..... . **'~**

. . ·;1 . **../~·** :·' lj.J

\ ( ./_. r-·---.. **~··~,** -::. ..

46 45 44 4.3 42 41 **40~·** ..... 39 38 37 36 35 .) \ 46 42 41 -40 39 Ja .37 36 .35

._ ----·.... l· **~-·r~·**

I I

34+1 ··., ··i • .. 1 ... , ' .

,. .\ ;·

t '

•. •. '',.··· ..

{ , I I • **·-~**

**~** ' / 34

**~** 1... t

.... t ' **~**

t

33 3.3

) /' \'

\ . '

I **~** ............ **~** ,. ............... \ .\

( '•, ' . . ..... - .. ·----- .. ·-/'""'

.. /':'""'"'· jl. }/,, .... ,,-. I

i t.. .. **~:ri** · · .. - ·· **~.:** J""· ...

I ' **~.** .. . ' ' \ **~** , ... J t., ·: . .-. \\

32 31 30 .32 31 .30

\:··· .......... ' **.~,'\** .. . ... \

2 9 -H I'. · .. " **·"':'~j·** '•iJ' L

2 T .. r - souTHEAsT t \ , I 29 28

**~I ~** 

27+ /i \ 27

26 + **'~** + + I I I I I I I I I I I I ·,\ I ) I I I I I I I I I 4 • • 26

99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 '84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 69 68 67

Figure 2. Portion Of The United States Covered By Potential ROM Applications

### scale modeling analyses. States may access ROM-generated data using the Gridded Model Information Support System (GMISS) (Computer Sciences Corporation, 1991). The us EPA archives air quality predictions as well as certain input information corresponding with·each application of ROM into GMISS. Groups using the UAM can readily make use of data retrieved from GMISS using the ROM/UAM Interface Program System (Tang et al. 1990). Similar means exist for using data retrieved from GMISS if EKMA is used (USEPA, 1991b). As impliedby Figure 2, there are locations within the United states where itwill not be feasible to use ROM in the foreseeable future. Further, ROM results may not be available for every episode which is of interest in every nonattainment area. Use of alternative regional scale models to generate**bounda~y** 

### conditions for urban scale models is acceptable. Such use should be specifically addressed in modeling protocols developed for each urban modeling application, and coordinated with the appropriate
u. s. EPA Regional Office(s) for approval on a case-by-case basis. Use of regional scale models is the preferred method for considering transport into a nonattainment area for several
reasons. First, it is the most defensible means for estimating boundary conditions (i.e., transport) after implementation of regional and urban strategies in upwind areas. As noted, attainmentdemonstrationsmustfocus onfuture periods specifiedin the Clean Air Act. Therefore, credibility of estimated future transport is a key consideration. A second advantage of using

22regional models is that they provide a far more comprehensive set of present boundary conditions than is feasible using any other method. This, inturn, replacesmuch of the subjectivitynecessary in specifying present boundary conditions using other means. For example, the Urban Airshed Model generally considers five or more vertical layers in the atmosphere. It is necessary to specify boundary conditions for each grid cell in each of these layers along a domain's upwindboundary for eachhour simulated. As noted in Section 3.3.2, it is impractical to collect monitored data for each of these grid squares. If monitoring data rather than regional models are used to specify boundary conditions, the specifications must be based on a limited number of direct observationsandinterpolationorsomeother, subjectiveprocedure. 3.3.2 Use of Monitored Data to Estimate Model Boundary Conditions If it is not possible to use a regional scale model to generateboundaryconditions forurban scalemodels, an alternative approach is to derive estimates of boundary.conditions based on available airqualitymonitoring data. If theUAM is used, Section 4.2.6 in Morris et al. 1990b shows grid cells in the UAM modeling domain for which boundary conditions must be specified for each hour of the simulation. As described inMorris et al. 1990b, it is possibletodividethemodelinggrid'sboundaries into subsegments. This may be useful if monitored data suggest a distinct horizontal concentration gradient along the modeling grid's boundaries. The UAM software permits use of two procedures for estimating hourly boundaryconcentrations in surface levelgridcellscomprisingeach 23

### segment of the domain's boundaries. The first of these assumes a constant concentration (of 03 , 

### precursors) for each segment. The second approach performs a linear interpolation between concentrations specified at each segment's end points to estimate boundary conditions in each surface grid cell included in a boundary segment. Morris et al. 1990b note that the procedure generally followed is to assume a spatially invariant (i.e., constant) concentration for cells in each segment. The UAM software also contains provisions for specifying hour-by-hour boundary conditions in grid cells aloft. These are described in Section 4.1.7 of Morris et al. 1990b. Two procedures have been most commonly used in past applications of UAM: (1) Assume a concentration which is constant with height; (2) Specify a vertical concentration profile pattern which varies between a concentration estimated, as described previously, in a surface grid square and a concentration specified
or calculated previously in a grid cell just above the mixing height (i.e., DIFFBREAK). The first method is the simpler of the two and may be justified, particularlyduring times of day with vigorous vertical mixing. The secondmethod is seeminglymore sophisticatedbut, if used, a rationale for the selected vertical profile should be included in the protocol describing the technical basis for the attainment demonstration. In the second method, concentrations

24above DIFFBREAK are usually initially assumed to be at background levels (see Section 3.3.3). It may often happen that monitored data for ozone exist to enable specification of boundary conditions, but there are no data for the NO, N02 , CO; and

### voc species which must also be specified. In this case, information in Table 1 (see Section 3.3.3·) will have to suffice for specifying values for unmonitored species. Boundary conditions are considered somewhat differently if EKMA is used. In the OZIPM4 model underlying EKMA, one models concentrations within a moving column of air. As described in USEPA 1989c, the simulation begins at 8 a.m. on the day of an observed exceedance, with the column located over the central city in the modeled CMSA/MSA. The column follows a straightline trajectory which places it at the monitoring site recording the exceedance at the time of the exceedance. During the simulation, the column grows in height to reflect the typical diurnal rise in mixing height. As the column height grows, air is entrained from aloft. Boundary conditions are consideredby specifying ozone and precursor qoncentrations in this layer aloft at the beginning of the simulation. These specified concentrations aloft are invariant with time. As noted previously, for attainment demonstrations, an estimate of future transported ozone and precursors is needed. In the absence of regional models, Figure 3 has been used to estimate future transported 03 , given an observed level of transported 03 (USEPA 1989c). To illustrateuse of the Figure, suppose a boundary
2503 concentration for an isolated urban area is estimated to be 0.10 ppm. The corresponding future boundary condition for 03 would be 0.09 ppm. Figure 3 is based on application of OZIPM4/EKMA with a 20 percent reduction in

## voc, no change in VOC speciation, and no change in NOx. Thus, for consistency, these latter assumptions should be used in conjunction with Figure 3.· In the absence of better information, this methodology may be applied for use with UAM as well as with EKMA. Use of alternative procedures for estimating future transport in the absence of regional modeling must be justified, and is subject to approval by the US EPA on a case-by-case basis. 3.3.3 Use of Modeling Procedures to Diminish Importance of Transport Barringan intensivefield study, itisclearfrom Section 3.3.2 that specification of present boundary conditions based on monitoring data requires a number of arbitrary procedures andjor subjectivejudgment. Unfortunately, evenwhen intensive field data
are available, the period of an intensive study often will not coincide with03 episodes of greatest interest. Further, the basis for estimating future boundary conditions is not strong. Therefore, it is appropriate to consider ways in ·which the sensitivityofmodel predictionstoassumedboundaryconditionscan be diminished. sensitivity of UAM predictions to boundary conditions can likely be diminished by increasingthe size of the modeling domain

26N-...}0.120.1 1"""'0.1//////,'0.0.09a.../t1-0.080n.(/)0.07z(20.06rwz0.050N'r00.04w0.0.3:::>r-:::>lL.0.020.0100Source:EPA,1989C/./_,////////J40.020.040.060.080.10.120.140.16·0.180.2PRESENTOZONETRANSPORT(PPM)Isolated/\rea____Mea:HthlargeAreaUpwindFIGURE3FUTUREOZOilETnAIISPORTASAFUIICTIOIIOFPRESEIHTRAHSPORTon the upwind side of the CMSA/MSA which is the focus of attention. There are, of course, practical limits to this in terms of data basemanagement andcomputerconstraints. Further, a tradeoffmust be made against the desirability of extending the domain downwind beyond the location of monitors observing.exceedances attributable to the CMSA/MSA being modeled. Table 1 contains recommended default inputs for boundary conditions contained in USEPA 1989c. Defaults may be used if the UAM modeling domain is enlarged, as described above. The recommendations for nonmethane organic compounds* (NMOC), NMOC speciation, and 0 3 are based on a review of aircraft observations in an unpublished report by Baugues (1987). Subsequent to the Baugues (1987) review, doubt was cast on the observed NOx data. Hence the NOx defaults are based on earlier recommendations (USEPA 1978). Recommendations for CO are based on a review of data produced from sampling aboard aircraft during the 1980 PEPE/NEROS study. The 

### co recommendation differs from that in USEPA (1989c). Therecommendationsmadeherein arebelievedmorerepresentative of available data and should supersede the CO default value recommended in USEPA (1989c). In the absence of better, areaspecific information, these defaults may be assumed to be constant vertically and horizontally. In USEPA 1989c, it is noted that future levels of NMOC and 

### co may·be reduced 20 percent, and NOx kept constant. NMOC composition is kept constant.

*The term "nonmethane organic compounds" applies to ambient measurements of organic compounds. 28Recommendations in Table 1 differ from some published elsewhere for use with the UAM (Morris et al. 1990c). The Morris et al. (1990c) recommendations are based on observations in more remote areas, whereas those in Table 1 are based on observations upwind and aloft of several cities. Unless the upwind bounds of the UAM modeling .domain are reflective of a remote area, information in Table 1 would appear more appropriate. If the Morris et al. (1990c) recommendations are consideredmore suitable in specific cases, future boundary conditions should be assumed identical to present boundary conditions. This is appropriate since the Morris et al. (1990c) suggestions are believed more reflective of natural background. As described inUSEPA 1989c, thevalues inTable 1 may be used
as defaults for the layer aloft considered in the OZIPM4/EKMA procedure. As with the UAM, the defaults for NMOC and 

## co may be reduced by 20 percent for future boundary conditions.

29Table 1

DEFAULT RECOMMENDATIONS FOR PRESENT TRANSPORTED BOUNDARY CONDITIONS

NMOC CBIV Speciation (Carbon Fractions)

03 NO" NO 

## co

*Source: PEPE/NEROS Study 30 ppbc

30 40 ppb 2 ppb 0 ppb 350 ppb* PAR = 0.498 ETH = 0.034 OLE 

### = 0.020 ALD2 

### = 0.037 FORM 

### = 0.070 TOL 

### = 0.042 XYL 

### = 0.026 ISOP = 0 NR = 0.2734.0 MONITORING DATA FOR CHARACTERIZING TRANSPORT IN RECOMMENDED MODELS 

### An obvious question to askupon reading Section 3.0 is, "What monitoring data are needed to drive the methods used to estimate boundary conditions for use with UAM and EKMA?" · This subject_ is addressed in Section 4. For serious, severe, and extreme 03 

### nonattainmentareas, recommendationscontainedhereinmustberegarded
as interim. Monitoring for these locations will be subject to regulations for enhanced monitoring networks in accordance with Section 182 (c)(1) of the CleanAirAct. These regulations are to bepromulgatedbyJune 1992. Recommendations inthis Sectionwhich
are inconsistentwiththose future regulations will be superseded. The discussion below proceeds by noting meteorological and air qualitydataneededtosupporteachmodelingproceduredescribedin Section 3. Next, suggestions aremade for samplingandanalysis to obtain thedata identifiedas necessary. Section4concludeswith recommendations regarding quality assurance of**coll~cted** 

### data. 4.1 Data Needed to Support Characterization of Transport in Models 4.1.1 TrajectoryModels As describedinSections 3.1and 3.2, thetrajectory models areusedtoestablishwhichCMSA/MSA(s) is (are) most likely contributingto an observed exceedance. The keydata required by the U.S. EPA TRAJECTORY model are hourly National Weather Service (NWS) surfacewinddatameasuredwithin 160km of themostprobable location of an air parcel during each hour from 8 a.m., LCT to the time of the observed daily maximum 0 3 

### concentration at the 0 3 

### 31monitor recording an exceedance. Because of concern over the representativeness of surface data at night, only 8 a.m.- 8 p.m., LCT, surface wind data recorded on the day(s) of an observed exceedance are needed. Table B-1 inMeyer et al. (1989) lists NWS sites for which data may be ordered. It is desirable to use as many wind observations as possible toconstructtrajectorieswithTRAJECTORY. However, priortousing additional observations, a note about NWS wind data is in order. These data reflect observations taken over a few minutes during eachhour rather than continuous hourly averages. Allowances have beenmade inthe TRAJECTORY model for this. It is recommendedthat data used to supplement the NWS observations be compatible with this characteristic. Two kinds of ancillary data are useful with the TRAJECTORY model. These are surface 03 measurements and upper air wind observations. Upper air wind data are useful as a guide to test whether adjustments made to surface data by TRAJECTORY are appropriate. These adjustments are made to make surface observations more representative of mean hourlywinds in the mixed layer. Clearly, if a trajectory model, like BAT or ATAD, which requires use of upper air data is used, upper air wind information is not ancillary, but essential. In ATAD and BAT, upper air-data
are used directlyto estimatemeanmixed layerwinds orto estimate winds in discrete layers.
ozone data are useful for testing the plausibility of conclusions drawn from trajectory models about whether or not
32overwhelming transport is likely. Time sequences for ozone data observed along the track of an estimated trajectory may provide additional support for conclusions reached using the wind data. 4.1.2 Urban Airshed Model The Urban AirshedModel makes use of a wide variety

. of meteorological and air quality data. These are described in Morris et al. (1990b) and inUSEPA (1991a). The discussionherein dwells solely on data useful to characterize boundary conditions. It is desirable to have air quality data collected at the surface and aloft (especiallyduring periods of atmospheric stratification like nighttime). However, collection of data aloft is a resource intensive operation which needs to be designed on a case-by-case basis. The following discussion addresses minimum surface data neededto avoid havingto rely entirelyonthe largedomain/default assumption methodology described in Section 3.3.3. Figure 4 is a conceptual picture of a minimal ozone monitoring network suitable for use with UAM. For purposes of illustration, conditions conducive to high ozone most frequently
occur with winds from U 1 • Second most conducive conditions occur with winds from U 2 • The following presents rough guidance for the siting of monitors in the network shown in Figure 4. Site 1: 15-50 km in the predominantly upwind direction from the city limits. Minimum distance upwind should be determined on a case-by-case basis,

33

### U2



# ® (1) 

# /

U1 

# ® (3)



### @ (5)

CENTRALCITY 

### LIMITS 

### (§) (4)



## FIGURE4. MINIMALOZONEMONITORINGNETWORK

34Site 2:

Site 3:

site 4:

Site 5: depending on city size and surroundings. Data from thismonitor are to beusedprimarily to estimate 03 transported to the model domain from upwind
sources. Near the predominantly downwind edge of the city limits. 15-35 km from the city limits in the predominantly downwind direction. 30+ km from the city limits in the predominantly downwind direction. 15-50 km in the second most prominent downwind direction. Under the first set of meteorological conditions (U1 ), Site 1 isuseful for estimatingboundary conditions. Data from Site 5 may also be useful if, like Site 1, it measures ozone on a regional scale as defined in 40 CPR 58, Appendix D. Data from Site 4 may supplement those from·Site 1 in establishing boundary values under the set of conditions depicted by U 2 , providing the data are regional in scale (40 CPR, Part 58, Appendix D). Data from sites not used for specifying boundary conditions may be used to assess model performance in predicting observed ozone concentrations. Care must be taken in interpreting surface ozone data for establishingtransportduringperiodsofhighatmospheric stability (e.g., night). During such periods, surface data are unlikely to be representative of concentrations aloft. In the absence of more

35direct measurements or indicators of ozone aloft, the following approximation of ozone aloft may be used: Use thehighervalue of the observedsurface concentrationfor the hour in question, or the surface**o~one** concentration averaged
over 9-11 a.m. LCT on the following morning. Precursors For purposes of characterizing boundary conditions for NMOC, NOx, and CO, sampling may be performed at sites {1), {5) and (4) in that order of preference. Care should be taken to ensure that the sampling sites are well-exposed. Sampling for NMOC within a vegetative canopy is unacceptable for purposes of characterizing regional boundary conditions. As with 03 , there is a concern that nighttime surface precursordata are unrepresentative of precursors aloft. Unlike 03 however, the concern isthat surfaceobservationswill overestimate concentrations aloft. In the absence of more direct information regarding concentrations aloft, during nighttime, the lower of the observed hourly surface measurement and the surface measurement averaged over 9-11 a.m., LCT, on the following morning may be used to approximate nighttime NMOC, NOx and CO aloft at regional sites intended to measure transport. During daylight hours, ozone and precursor data should be used as described in Section 3.3.2. 4.1.3 Empirical Kinetics Modeling Approach Unlike UAM, EKMA only requires one assessment of boundary values for 03 , NMOC, NOx, and

### co per day. As described in
36USEPA 1989c, the period chosen is the first full hour occurring after breakup of the nocturnal inversion. If this is not known, a 10 a.m. - 12 noon LCT average surface concentration observed at upwind, regional sites may be used. For ozone, a minimal monitoring network similar to that in Figure 4 is suggested. The discussion in Section 4.1.2 also applies. Sampling of transported NMOC, analysis of speciated NMOC data and sampling/analysis of transportedNOx and CO, though desirable, has a lower prioritywith EKMA than with UAM applications. 4.1.4 Regional Oxidant Model Because of the spatial scales involved with this model, specification of its boundary conditions is likely to be less critical than is the case for urban models. However, measurementsofregionalozone/precursorsconcentrationswithinthe regional domainmaybeuseful for evaluatingROM modelperformance. Monitored ozone data may be used to establish boundary values for
ozone in ROM using applicable guidance described in Sections 3.3.2 and 4.1.2 for UAM. Use of a natural background default value for
ozone (Morris, et al. 1990c) is an acceptable alternative in the absence of suitable monitored data. Once boundary values are specified for ozone, a routine in the ROM establishes chemical equilibration with the specified ozone concentrations to derive concentrations for other chemical species. Hence, it is unnecessary for the user to specify these values.

374.2 Instrumentation/Deployment 4.2.1 Winds, Other Meteorological Data GuidanceprovidedinUSEPA (1987) shouldbe followed with respect to instrumentation and deployment at surface wind monitoring sites. Meteorological data aloft will be derived from sounding information collected twice daily at sites approximately 500 km apart. These data are archived and may be obtained from theNational ClimaticData Center inAsheville, NC. Data collected in special field studies such as the Lake Michigan Ozone study and the Southern Oxidant Study should also be used if available for periods of interest. 4.2.2 Ozone
ozone shouldbe measured as described in Appendix D to 40 CFR, Part 50. For characterizing transport with UAM and EKMA, these measurements should be on a regional scale (40 CFR, Part 58, Appendix D). 4.2.3 NOX UAM and EKMA require measurement of both nitric oxide (NO) and nitrogen dioxide (N02 ). TransportedNO, NOx, and N02 should be measured using alternative A (gas phase titration) described inAppendix F to 40 CFR, Part 50. Measurements shouldbe collocated with the regional scale ozone measurements used to characterize ozone boundary conditions.

38

### 4.2.4 

## co Carbon monoxide should be measured as described in Appendix 

## c to 40 CFR, Part 50. Measurements should be collocated with regional scale ozone measurements. 4.2.5 NMOC Procedures for sampling and analyzing ambient organiccompounds arerapidlyevolving. Itisno longersufficient to use procedures outlined in Appendix E to 40 CFR, Part 50. Instead, it is recommended that sampling be done remotely using canisters. Contents of the canistersmay be analyzed in a central laboratory. Sampling procedures and care of the canisters is describedbyMcAllisteretal. (1990). Collectionofcanisterdata to provide hourlyboundary conditions for use inUAM would present verydifficultlogisticalproblems. Therefore, if itisdecidedto sampleboundaryconditionsforNMOC usingcanisters, thiswillmost likelyhave tobe done on a discontinuous, sporadicbasis. Threehour samples collectedmid-morning (9-12), early afternoon (12-3), lateafternoon (3-6), andatnight (8-11) at 6-dayintervalsduring the ozone season, may provide a sufficient basis for establishing representativeboundaryconditions anddiurnal patternsneeded for the UAM. Whether an NMOC sampling program for. UAM boundary .conditions should be undertaken is a decision most appropriately made by those responsible for derivingthe modeling protocol for a CMSA/MSA's attainment demonstration (USEPA 1991a). If performed, sampling shouldbe done at regional scalemonitoring locations (40 CFR, Part 58, Appendix D). Due to large concentration gradients
39likely near vegetation, sampling should be out in the open, not within a canopy of vegetation. Sampling needs for estimatingboundary NMOC for use with EKMA are.somewhat less demanding. Consistent with the discussion in Section 4.1.3, sampling needs to be performed over a single 3-hour period from 10-12 LCT as frequently as feasible. As with UAM, one ofthe issues addressedbythose constructingthemodelingprotocol should be whether such sampling is necessary. Two approaches are possible for analyzing NMOC samples. The first approach is throughuse of gas chromatography and analysis of peaks on resulting chromatograms. Appropriate procedures for analyzing NMOC samples are described in Seila, et al. (1989). The principal advantage of this approach is that·it enables retention of data which allow one to develop NMOC species profiles for boundary conditions. The major drawback is that it requires availability of a highly trained analyst and is, therefore, expensive. The second analytical approach is the cryogenic preconcentration approach (often abbreviated PDFID) (McElroy et al. 1985). This approach is considerably less expensive than the first, but itdoes not allowone to examine speciateddata. Choice of analytical approach is d.ictated by pri9rities in a particular study area and by available resources. 4.3 Quality Assurance of Monitored Data The same scrutiny given all monitored data used to support UAM and EKMA analyses applies to data being considered to

40derive boundaryconditions. AppendixAto 40 CFR 1 Part 58 outlines
a series of mandatory features for an acceptable quality assurance program. These are listed below. (1) Documented selection

**~ocedures** for methods1 analyzers or samplers. (2) Provisions for training of personnel. (3) Installation of equipment. (4) Selection and control of calibration standards. (5) Adherence to calibration procedures. (6) Procedures for zerojspan checks and adjustments of automated analyzers. (7) Procedures for control checks and their frequency. (8) Control limits for zero1 span and other control checks and commitment to respective corrective actions when such limits are surpassed. (9) Calibration procedures and zero/span checks for any multiple range analyzers. (10) Provisions for preventive andremedialmaintenance. (11) Quality control procedures for air pollution episode monitoring. (12) Recording and validating data. (13) Data quality.assessment (precision and accuracy). (14) Documentation of quality control information.

41

### This page intentionally left blank

425.0 SUMMARY A series of modeling analyses has been identified for characterizingtransport into nonattainment areas. These analyses enable one to: (a) determine the most likely principal cause of an observed exceedance (transport or local emissions); (b) identifyupwindCMSA/MSA 1s most likelyto contribute to an exceedance if overwhelming transport is determined likely in (a); (c) quantifytransport intoCMSA/MSA1s identifiedin (b)
so that such transport may be considered in estimating whether contemplated control strategies will be sufficientto eliminate an exceedance observed downwind. (d) estimate the cumulative effect of emissions in several CMSA/MSA1s on interstate transport. The discussion next focused on meteorological and air quality monitoringdata neededto supportthe analyses noted above. Needed measurements, considerations instrumentation, operating provisions were identified. in monitoring network procedures and quality design,
assurance

To implement the procedure for characterizing transport into nonattainment areas, use of the following modeling and monitoring criteria are suggested. (1) Use of trajectorymodels is ordinarily recommended: (a) toestablishwhetheranexceedance isprimarily due to local emissions or overwhelming transport (Section 3.1);

43(b) to identify contributing CMSA/MSA(s) if overwhelming transport is identified in (a) (Section 3.2); (2) The US EPA TRAJECTORY model is appropriate for qualitatively estimating the prime cause (transport or local emissions) of most exceedances. To support use of the TRAJECTORY model, the following monitoring data are needed or desirable: ' (a) Surface wind data at NWS sites within 160 km (Sections 3.1 and 4.1.1); (b) other surface wind data, as appropriate (Section 4.1.1); (c) surfaceozonedata (desirable) (Section4.1.1); (d) upper airwind data.(desirable for TRAJECTORY, required for other trajectory models)(Section 4.1.1). (3) Trajectorymodelsmay alsobeusedto identifyrural transport areas. Several additional procedures are suggested for this purpose if it is determined that available data or models are inadequate for use in a particular application (Section 3.1). (4) For extreme, severe, serious, and some moderate 03 nonattainment areas, the Urban Airshed Model (or other approved urban scale photochemical grid models) should be used to estimate controls needed in upwind CMSA/MSA's to eliminate a downwind exceedance. Transport into a modeled CMSA/MSA ( i .e., boundary conditions) may be considered using one of several approaches. (a) The preferred approach is use of the EPA ROM (Section 3.3.1).
44(b) Use ofotherregional models isencouragedwhen it is not feasible to use ROM. Modeling procedures are subject to 

## us EPA approval on a case-by-case basis (Section 3.3.1). (c) In the absence of regional modeling data, boundary conditions may be derived from monitored data (Section 3.3.2). (d) Inthe absenceof regionalmodelingresults and sufficientmonitoring data, expand the upwind dimension of the UAM modeling domain and use recommended default assumptions for boundary conditions (Section 3.3.3). (5) For some moderate 03 nonattainment areas, the Empirical KineticModelingApproach (EKMA) may be used to estimate controls needed in a contributing CMSA/MSA to eliminate a downwind exceedance. Consider transport into a modeled CMSA/MSA (i.e., boundary conditions) using one of several approaches. (a) The preferred approach is use of the EPA ROM (Section 3.3.1). (b) Useof otherregionalmodels is encouragedwhen it is not feasible to use ROM. Modeling procedures are subject to 

## us EPA approval on a case-by-case basis (Section 3.3.1). (c) In the**~bsence** of regional modeling data, boundary conditions may be derived from monitored data (Section 3.3.2). (d) In the absence of regional modeling data and sufficient monitoring data, use recommended default values for boundary conditions (Section 3.3.3).

45

### (6) Regionalozonemodels, suchasROM, arerecommended, when available, as the most appropriate procedures for estimating cumulative effects of emissions from many CMSA/MSA's on interstate transport of ozone. (Sections 3.2.2, 3.3.1) (7) To estimate boundary conditions for UAM based on monitored data, the following measurements are minimal requirements: (a) surface ozone at regional site(s) (Sections 4.1.2, 4.2.2); (b) surface NO, N02 , 

### co, at regional sites (Sections 4.1.2, 4.2.3, 4.2.4); (c) NMOC may be sampled using canisters during several 3-hour periods at intervals ·of no more than six days (desirable) (Sections 4.1.2, 4.2.5); (d) NMOC may be analyzed from chromatographs (desirable) or using the PDFID approach. The former approach is necessary to obtain speciated data (Section 4.2.5). (8) To estimate boundary conditions for EKMA based on monitored data, the following measurements are minimal requirements: (a) use of late**m~rning** 

### surface ozone data at regional sites (Sections 4.1.3, 4.2.2); (b) surface NO, N02 , 

### and 

### co observed late morning at regional sites (Sections 4.1.3, 4.2.3, 4.2.4).

46

### (c) NMOC may be sampled during a 3-hour period in late morning using canisters at intervals of no more than six days (desirable) (Sections 4.1.3, 4.2.5); (d) NMOC may be analyzed from chromatographs. However, use of the PDFID approach and default recommendations for NMOC speciation is recommended (Sections 3.3.3, 4.2.5). (9) Monitored ozone data are ordinarily used to establish boundary conditions for regional scale models, but default natural background levels can also suffice. In ROM, boundary values for other chemical species are derived from specified ozone values. Data collected at regional scale monitoring sites forurban scalemodelinganalyses maybeuseful in evaluating performance of regional models (Section 4.1.4). (10) To be used as suggested herein, air quality data should be collected and analyzed consistently with mandatory quality assurance procedures (Section 4.3).

47

# . '

This page intentionally left blank

48

# .

# . REFERENCES CITED BAUGUES, K. A., (1987), Support Document for Selection of Default Upper Air Parameters for EKMA, Unpublished report. CAUSLEY, M. c., 1990, User's Guide for the Urban Airshed Model. Volume IV: User's Manual for the Emissions Preprocessor System, EPA-450/4-90-007D. COMPUTER SCIENCES CORPORATION, (1991), Gridded Model Information Support System (GMISS). UAM Subsystem, User's Guide, Volume II: (UAM Subsystem, EPA-450/4-91-009. DOUGLAS, S. G., R. C. KESSLER and E. L. CARR (1990), User's Guide for the Urban Airshed Model. Volume III: User's Manual for the Diagnostic Wind Model, EPA- 450/4-90-007C. HEFFTER, J. L., (1980), Air Resources Laboratories Atmospheric Transport and Dispersion Model (ARL-ATAD) NOAA Technical Memorandum ERL ARL-81, Air Resources Laboratories, Silver Spring, MD. HEFFTER, J

.. L., (1983), Branching Atmospheric Trajectory (BAT) Model, NOAA Technical Memorandum ERL ARL-121, Air Resources Laboratory, Rockville, MD. LAMB, R. G., (1983), A Regional Scale (1000km) Model of PhotochemicalAirPollution, Part 1 - TheoreticalFormulation, EPA -600/3-03-035. MEYER, E. L. and K. A. Transported ozone and EPA-450-4-89-010. BAUGUES, (1989), Consideration of Precursors and Their Use in EKMA, MORRIS, R. E. and T. C. MYERS, (1990), User's Guide for the Urban Airshed Model. Volume I: User's Manual for UAM (CB-IV), EPA-450/4-90-007A. MORRIS, R. E., T. C. MYERS, E. L. CARR, M. C. CAUSLEY and S. G. DOUGLAS, (1990b), User's Guide for the Urban Airshed Model. Volume II: User'sManual for the

### UAM (CB-IV) Modeling System, EPA-450/4-90-007B. MORRIS, R. E., T. C. MYERS, H. HOGO, L. R. CHINKIN, L.A. GARDNER and R. G. JOHNSON, (1990), Urban Airshed Model Study of Five cities, a Low-cost Application for the Urban AirshedModel to the New YorkMetropolitanArea andthe Cityof St. Louis, EPA450/4-90-006E.

49REFERENCES (CONTINUED) McELROY, F. F., V. L. THOMPSON and H. G. RICHTER, (1985), A Cryogenic Preconcentration

- Direct FID CPDFIDl Method for Measurement of NMOC in Ambient Air, NTIS Publication Number PB-120631. McALLISTER, R. A., P. L. O'HARA, D. DAYTON, 

### J. E. ROBBINS, R. F. JONGLEUX, R. G. MERRILL, JR., JO RICE and E. G. BOWLES, (1990), 1990 Nonmethane Organic Compound and Three-Hour Air Taxies Monitoring Program, Draft Final Report, N. F. Berg, USEPA Project Manager. SEILA, R. L., W. A. LONNEMAN and S. A. MEEKS, (1989), Determination of C2 to C,2 Ambient Hydrocarbons in 39 U.S. Cities from 1984 to 1986, EPA/600/3-89/058 (Appendix B). SYSTEMS APPLICATIONS, INC., (1988), A PC Based System for Generating EKMA Input Files, EPA-450/4-88-016. TANG, R. T., S.C. GERRY, J. S. NEWSOME, A. R. VAN METER, R. A. WAYLAND, J. M. GODOWITCH and K. L. SCHERE, (1990), User's Guide for the Urban Airshed Model. Volume V: Description and Operation of the ROM-UAM Interface Program System, EPA-450/4-90-007E. USEPA, (1978), ozone Isopleth Plotting Package COZIPP), EPA-600/8-78-014b. USEPA, (1987), on-site Meteorological Program Guidance for Regulatory Modeling Applications, EPA-450/4-87-013. USEPA, (1989a), User's Manual for OZIPM4 (Ozone Isopleth Plotting With Optional Mechanisms) Volume 1, EPA 450/4-89-009a. USEPA, (1989b), User's Manual for OZIPM4 (Ozone Isopleth Plotting With and Optional Mechanisms). Volume 2- Computer Code, EPA450/4-89-009b. USEPA, (1989c), Procedures for Applying City-Specific EKMA, EPA-450/4-89-012. USEPA, (1989d), Aerometric Information Retrieval System (AIRS), Volume I; Office of Air Quality Planning and standards, Research Triangle Park, NC 27711.

50 

# . 'TECHNICALREPORTDATA 

# ... {PleasereDdInstructionsonthereversebeforecompleting) 1.REPORTNO. 

# ,2. 3. RECIPIE!'IT"SACCESSIONNO.



### EPA-450/4-91-015 ' 4.TITLEANOSUBTITLE 5.REPORT DATE



### Criteriafor Assessing the Role ofTransportedOzone/ May 1991 Date ofIssue Precursors in Ozone NonattainmentAreas 6.PERFORMINGORGANIZATIONCODE

7.AUTHOR(S) 8.PERFORMINGORGANIZATION REPORTNO.

E. 

### L. Meyer
I i 9.PERFORMINGORGANIZATIONNAMEANDADDRESS 10.PROGRAM ELEMENTNO.



### U.S. Environmental ProtectionAgency (MD-14) A24A2F OfficeofAir Quality Planning and Standards 11.CONTRACT/GRANTNO. 

### Technical SupportDivision 1 i 

### Research Triangle Park, NC 27711 None ! 12.SPONSORINGAGENCY NAMEANDADDRESS 13.TYPEOF REPORTANDPERIODCOVERED 

### Final 14.SPONSORINGAGENCY CODE 

### Same I 

### I
15.SUPPLEMENTARY NOTES



# . 1 16.ABSTRACT



### Aseries ofmodeling analyses appropriate forcharacterizingtransportofozone and itsprecursors intononattainment areas is discussed. Airqualityand meteorological measurements needed to characterizetransport in identifiedmodeling techniques are also identified. The report fulfills requirements in Section 184(d) ofthe Clean AirActAmendments of 1990, in which the U.S. Environmental ProtectionAgency is directedto identifycriteriafor estimating transportofpollutants intoozone nonattainment areas.

17. KEYWORDSANDDOCUMENTANALYSJS a. DESCRIPTORS b.IDENTIFIERS/OPEN ENDEDTERMS c. COSATlField/Group



### ozone ozone models ozone/precursormonitoring pollutanttransport

• 18. DISTRIBUTIONSTATEMENT 19.SECURITY CLASS (ThisReport) 21. NO.OF PAGES 

### 51 Unlimited 20.SECURITYCLASS (TIJispage) 22.PRICE

EPA form2220-1 (Rev.4-77) PREVIOUS EDITION IS OBSOLETE