Sensitivity Analysis and Preliminary Evaluation of RELMAP Involving Fine and Coarse Particulate Matter: Project Report


            United States           Atmospheric Sciences
            Environmental Protection    Research Laboratory
            Agency	Research Triangle Park, NC 27711
            Research and Development   August, 1987
  EPA    PROJECT REPORT
            A SENSITIVITY ANALYSIS AND
PRELIMINARY EVALUATION OF RELMAP INVOLVING
      FINE AND COARSE PARTICULATE MATTER

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A SENSITIVITY ANALYSIS AND PRELIMINARY EVALUATION OF RZLMAP

       INVOLVING FINE AND COARSE PARTICULATE MATTER
                            by
                       Brian K. Eder

            Meteorology and Assessment Division
         Atmospheric Sciences Research Laboratory
           U.S. Environmental.Protection Agency
       Research Triangle Park, North Carolina  27711
         ATMOSPHERIC SCIENCES RESEARCH LABORATORY
            OFFICE OF RESEARCH AND DEVELOPMENT
           U.S. ENVIRONMENTAL PROTECTION AGENCY
       RESEARCH TRIANGLE PARK, NORTH CAROLINA  27711

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                          DISCLAIMER


     The information contained within this document has been
 funded  by  the United States Environmental  Protection Agency.
 It has  been  subjected to  the Agency's peer and administrative
 review  and  it  has been  approved for publication  as  an EPA
 document.   Mention  of trade names or commercial products does not
 constitute  an endorsement or recommendation for use.
                         AFFILIATION
     Mr.  Eder  is currently  on  assignment  from the  National
Oceanic and Atmospheric Administration, United States Department
of Commerce.

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                           ABSTRACT
     In response to the  new,  size discriminate federal  standards
for Inhalable Particule  Matter, the REgional Lagrangian Model of
Air Pollution  (RELMAP) has  been modified  to  include simple,
linear parameterizations which simulate the chemical and physical
processes of fine and  coarse particulate matter.

     Because these new,  simplified parameters  are  only accurate
to a limited degree,  they may be  upgraded or replaced in the
future with more sophisticated parameters as further research is
conducted.   As an  initial  step  in this possible refinement,
RELMAP has been subjected  to  a sensitivity analysis in which the
effect of  inducing  a +/- 50%  change  in the  three major
parameterizations (transformation rate  and wet and dry deposition
rates) involving the simulation  of fine and coarse particulate
matter has  been examined.   Simulated concentrations  of fine and
coarse particulate  matter  proved to be most sensitive to the wet
deposition of fine  and coarse particulate  matter,  respectively;
fine concentrations  were somewhat sensitive to the transformation
rate  of  sulfur  dioxide  (S02) into  sulfate  (S04~) ,  and  less
sensitive to the wet deposition of S02,  and the dry  deposition of
fine  particulate matter  and S02;  and  finally  coarse
particulate concentrations were somewhat sensitive to the dry
deposition of coarse particulate matter.

     In order to assess the model's abilities, and to determine
just how  accurately these new parameters  simulate the actual
physical and chemical processes of the atmosphere, RELMAP was
evaluated for the summer of 1980, using emissions  data from the
NAPAP Version 5.0 emissions inventory,  monitoring   data from the
Inhalable Particulate  Network and meteorological  data  from the
National  Climatic Data Center.  Unfortunately,  several  obstacles
limited  the scope of this evaluation; the  two most important
being  the omission of open source emissions from the NAPAP
inventory, and the  spatial and temporal incompatibility of the
IPN data.   Given the  nature of these  deficiencies, it is not
surprising  that RELMAP   significantly underpredicted the
concentrations  of fine and coarse particulate matter. The model
did, however,   exhibit  some skill  in its  simulation  of   the
concentrations, producing correlation coefficients of 0.53 and
0.33  for  fine and coarse particulate matter,  respectively.

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                           CONTENTS
Abstract	iii
Figures	vi
Tables	ix
Acronyms and Symbols	•	x
Acknowledgments	xi
     1.  Introduction	1

     2 .  Model Background	5

              Transport and Diffusion	8
              Transformation	10
              Dry Deposition	14
              Wet Deposition	18

     3 .  Sensitivity Analysis	22

              Coarse Particulate Matter	26
              Fine Particulate Matter	30

     4 .  Preliminary Model Performance Evaluation	39

              Deficiencies in the NAPAP Emissions Inventory....40
              Deficiencies in the IPN Data Set	46
              Model Evaluation for the Summer of 1980	54

     5.  Conclusions and Recommendations	60
References	67
Appendices

     A.  Fine Particulate Matter Concentrations	70
     B.  Coarse Particulate Matter Concentrations	74

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                             FIGURES
Figure                      Caption
 2.1     RELMAP's 45° x 30° longitude-latitude domain ..... ......6

 2.2     Depiction of RELMAP parameterizations ..... . ........ ... .7

 2.3     Three layer vertical profile with nighttime
         allocation of emissions ......... . ............ ......... .9

 2.4     Bimodal probability distribution  of particle size..... 11

 2.5     Latitudinal variation in the composite transformation
         rate of S02 to S04~. ....... ....................... .... 13

 2.6     Diurnal variation in the composite transformation
         rate of S02 to S04~ ................................... 13

 2.7     Land use categories used for dry  deposition  and
         corresponding surface roughness lengths (ZQ) .......... 15

 3.1     RELMAP domain with sensitivity analysis transect ...... 24

 3. 2. a   Absolute sensitivity of coarse particulate matter
         concentration to changes in  the wet deposition
         rate of coarse particulate matter. .... ........ . ....... 27

 3.2.b   Relative sensitivity of coarse particulate matter
         concentration to changes in  the wet deposition
         rate of coarse particulate matter ..................... 27

 3. 3. a   Absolute sensitivity of coarse particulate matter
         concentration to changes in  the dry deposition
         rate of coarse particulate matter ..................... 28

 3.3.b   Relative sensitivity of coarse particulate matter
         concentration to changes in' the dry deposition
         rate of coarse particulate matter ................... . . 28

 3. 4. a   Absolute sensitivity of fine particulate matter
         concentration to changes in  the wet deposition
         rate of S02 ° ...... . ................................... 31

 3.4.b   Relative sensitivity of fine particulate matter
         concentration to changes in  the wet deposition
         rate of S02 ........................................... 31

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3.5.a   Absolute sensitivity of fine particulate matter
        concentration to changes in the wet deposition
        rate of fine particulate matter	32

3.5.b   Relative sensitivity of fine particulate matter
        concentration to changes in the wet deposition
        rate of fine particulate matter	32

3.6.a   Absolute sensitivity of fine particulate matter
        concentration to changes in the dry deposition
        rate of S02	33

3.6.b   Relative sensitivity of fine particulate matter
        concentration to changes in the dry deposition
        rate of S02	33

3.7.a   Absolute sensitivity of fine particulate matter
        concentration to changes in the dry deposition
        rate of fine particulate matter	34

3.7.b   Relative sensitivity of fine particulate matter
        concentration to changes in the dry deposition
        rate of fine particulate	34
3.8.a   Absolute sensitivity of fine particulate matter
        concentration to changes in the transformation
        rate- of S02 to S04~	35

3.8.b   Relative sensitivity of fine particulate matter
        concentration to changes in the transformation
        rate of S02 to S04"
J Zi
4.1     Area and point source emissions of TSP emitted
        within the RELMAP domain	41

4.2.a   Point source fractionalization of TSP emitted
        within the RELMAP domain	43

4.2.b   Area source fractionalization of TSP emitted
        within the RELMAP domain	43

4.3     Inhalable particulate network sites used in the
        preliminary model evaluation	43

4.4     Temporal depiction of the observed and simulated
        fine particulate matter concentrations for
        Hartford, Conn., for the summer of 1980	52

4.5     Temporal depiction of the observed and simulated
        coarse particulate matter concentrations for
        Hartford, Conn. , for the summer of 1980	53

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4.6     Scatter diagram of the observed vs.  simulated
        fine particulate matter concentrations for the
        summer of 1980	5"

4.7     Scatter diagram of the observed vs.  simulated
        coarse particulate matter concentrations for the
        summer of 1980. „. . .. . .. »»..<,*......<..<,...	»...„..57

4.8     Standardized residuals ((0-P)/0)  of  the fine
        particulate matter concentrations for the
        summer of 1980	59

4.9     Standardized residuals ((0-P)/0)  of  the coarse
        particulate matter concentrations for the
        summer of 1980	59
                            vm

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                             TABLES
Table                        Title                            Page
 2.1       Typical, seasonal wet deposition rates for S02,
           S04~, fine and coarse particulate matter
           for a constant precipitation rate (5mm/h)	21

 4.1       Estimates of omitted open source emissions of TSP
           for states located within the RELMAP domain	45

 4.2       Inhalable particulate network sites used in the
           preliminary model evaluation	49

 4. 3       Statistical evaluation involving fine
           particulate matter concentrations	55

 4 . 4       Statistical evaluation involving coarse
           particulate matter concentrations	56

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                 LIST OF ACRONYMS AND SYMBOLS
Acronyms


EMSL    -   Environmental Monitoring Systems Laboratory
ENAMAP  -   Eastern North American Model of Air Pollution
EURMAP  -   European Model of Air Pollution
IP      -   Inhalable Particulate
NAPAP   -   National Acid Precipitation Assessment Program
NAAQS   -   National Ambient Air Quality Standards
OAQPS   -   Office of Air Quality Planning and Standards
RELMAP  -   REgional Lagrangian Model of Air Pollution
SCC     -   Source Classification Code
SSI     -   Size Selective Inlet
TSP     -   Total Suspended Particulate
Symbols
a
b
CO
HCl
HF
k
Kd
K
M
NH
NO
Pb
R
so
so
  2=
VOC
empirical factor used to calculate wet deposition
empirical exponent used to calculate wet deposition
carbon monoxide
hydrogen chloride
hydrogen fluoride
von Karman constant  (0.4)
dry deposition rates
transformation rates
wet deposition rates
Monin-Obukhov length (cm)
mass
ammonia
nitrogen oxides
lead
rainfall rate used to calculate wet deposition  (mm/h)
surface resistance to deposition  (1.0 s/cm)
Stability category
Sulfur dioxide
Sulfate
friction velocity (cm/s)
dry deposition velocity  (cm/s)
volatile organic carbon
stability factor
height above surface (cm)
surface roughness scaling length  (cm)

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                       ACKNOWLEDGMENTS










     The author would  like  to  express his appreciation to the



many people who have assisted in the  preparation of this report.



Specifically Dale H. Coventry of the Data Management Branch, ASRL



and Terry L. Clark  of the Atmospheric Modeling Branch, ASRL, who



helped in the development of this publication and also to Thomas



E.  Pierce and C. Bruce Baker,  of the Environmental Operations



Branch,  ASRL whose  comments and  recommendations  proved



invaluable.

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                         SECTION
                        INTRODUCTION










     The primary National Ambient Air Quality Standard (NAAQS)



for particulate matter was established in 1970 with the enactment



of the Clean Air Act.   The values of the standard were based  upon



state-of-the-art  information  concerning the health effects of



ambient  concentrations  of  Total  Suspended Particulate  (TSP)



matter and other environmental factors. In 1977,  the Claan Air



Requirement Act   called for a  reappraisal of this  NAAQS.  One



reason for this reappraisal was a  shift  in emphasis from  TSP,



which  ranged  in size from  0.0 to   50.0  urn,  to smaller,  size



discriminate  Inhalable  Particulate  (IP)  matter,  which ranged in



size  from  0.0  to  15.0 urn.  The  IP  was  comprised  of  fine



particulate matter (FINE-10), which included particles less  than



2.5 urn in diameter, and coarse particulate matter (COARSE-15),



which initially  included particles greater than or equal to 2.5,



but less than  or equal to 15.0 urn.



     Emphasis was placed on the smaller size  particles for two



reasons.  First, additional  research into the health effects of



particulate matter revealed  that the smaller particles were not



only able to penetrate deeper into the respiratory  system, but



their expulsion rate was also lower than the  larger particles.



Secondly, naturally  occurring dust particles with diameters

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greater than 10.0  -  15.0 um often made up a large percentage of
the TSP  mass collected by high volume  samplers.  This  large
natural contribution,  when  combined with  anthropogenic sources,
often resulted in TSP concentrations exceeding either the 75.0
ug/m3  annual geometric mean,  or the 260.0 ug/m3  daily  mean
(Hinton et al., 1984).
     In 1981, after  reviewing EPA's Clean Air Science Advisory
Committee's  recommendation and the  concurrent  International
Standards Organization Task Group recommendations, the Office of
Air Quality  Planning and  Standards  (OAQPS)  decided that  the
revised standard  for ambient  air concentrations  of IP should be
based upon a 10 um rather than a 15 um criteria  (Hinton et al.,
1984). Therefore, COARSE-15  was  replaced by COARSE-10,  which
included particles greater  than  or equal to 2.5 um, but less than
or equal  to   10.0   um. The proposed  new  standard would  allow
ambient air  concentrations  of  IP to  reach an annual arithmetic
average   between  50 and 65 ug/m3 and a daily maximum  between
150.0  and 250.0 ug/m3  (Federal  Register, 1984).
     As a result of  the revised NAAQS standards for ambient air
concentrations of primary particulate matter,  OAQPS has expressed
the need  for size discriminate particulate  models in order to
assist in regulatory planning. Shifting the emphasis onto the
smaller  particles increases  the  importance of  regional  scale
models.   Much of  the mass  of  the smaller particles results from
gas to aerosol conversion  which is a slow process  that occurs
over  regional spatial scales as opposed to  urban scales.
Therefore, in response to the promulgation of the new  size
discriminate federal  standards for IP, the REgional Lagrangian

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Model of Air Pollution (RELMAP)   has been modified to include



simple,  linear  parameterizations which simulate the  chemical and



physical processes of FINE-10 (including the conversion  of S02 to



S04=) and COARSE-10.    Because  the  contribution  of  nitrogen



chemistry in the formation of particulate matter is thought to be



negligible  at  this time,  it  is  ignored by the  model.   It is



important  to remember that this  modified version of  RELMAP



represents  an initial step in the linear,  regional modeling of



particulate matter and  therefore must  be looked upon  as an



interim model.



     The origin of RELMAP dates back to the mid-1970's,  when SRI



International   developed a Lagrangian puff air pollution model



called  the  European Model  of Air Pollution  (EURMAP)  for the



Federal Environment Office of the Federal Republic of Germany



(Johnson et  al.,  (1978).  This original version  of  the model  only



simulated monthly concentrations  and  wet  and dry  depositions of



S02  and SO4~,   for  thirteen countries in central  and western



Europe.   During the  late  1970's,  the U.S. EPA  sponsored SRI



International  to modify EURMAP so that it could be applied to



eastern North America.   This  modified  version of the model,  now



called the Eastern North American Model of  Air Pollution (ENAMAP)



was also capable  of  simulating monthly concentrations as well as



wet  and dry depositions of S02 and S04= (Bhumralkar et al.,  1980;



Johnson, 1983).



     During  the early  and middle  1980's,  EPA continued  to modify



and  improve the model  to  increase  its  flexibility  and its



scientific  credibility.  Now,  at the request  of OAQPS,  simple

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parameterizations involving  fine  and coarse particulate matter



have been  incorporated into the model.



     This report  examines  the  incorporation of  these  new



parameterizations, first through an abbreviated discussion of



their theoretical aspects as  presented in Chapter 2. For a more



in-depth discussion of these parameterizations, the reader is



referred to the RELMAP User's  Guide  (Eder  et al.,  1986).  In



order  to  determine  the sensitivity  of  the model to  these



parameterizations, a sensitivity analysis of   RELMAP  has been



provided in Chapter 3.  Chapter 4 provides a preliminary model



performance evaluation  to help assess the model's abilities  and



to determine  how accurately  the  parameters  simulate  the actual



physical  and chemical processes  of the  atmosphere.   Conclusions



and recommendations for future work are provided in Chapter 5.

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                          SECTION  2
                       MODEL BACKGROUND





     RELMAP is  a mass-conserving,  regional-scale Lagrangian model

that performs simulations over 1° by 1°  grid  cells  covering the

eastern two-thirds of the United States  and southeastern Canada

as  depicted in  Figure  2.1.   The  north-south and  east-west

boundaries  of  the model's domain extend from  25° N to 55° N

latitude and from 60° W to 105° W longitude.   Discrete puffs of

SO2, S04=,  fine and  coarse particulate matter are released at

twelve  hour intervals from  each of the  1350  grid cells that

contain sources.   As illustrated in Figure 2.2, the puffs are

then subjected  to  linear  chemical transformation and wet and dry

deposition processes  as they are transported  across the model's

domain.   The suspended  mass and deposition  for  each puff is

apportioned into  the  appropriate  grid  cell  based  upon  the

percentage  of  puff over  that grid cell.  The rate  of change in

the pollutant mass resulting  from the transformation and wet and

dry deposition  process is directly proportional to the total mass

and is defined  through the following linear equations:
  S02:                dMl  =  -M^Kt + Kdl + K^) ;      (2.1)
                      dt

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Figure 2.1  RELMAP's  45°  x  30°  longitude-latitude  domain.

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        Figure 2.2  Depiction of RELMAP parameterizations.
  S04~:
                       dt
  Fine Particulate:     dM3  =  -M3(Kd3 +
  Coarse Particulate:
                       dt
dM,
dt
=  -M4(Kd4
                              ;  (2.2)
                                 (2.3)
(2.4)
where Mj_ is  the mass  of the respective pollutants (expressed in

ktons), t is the time (h),  and Kt is the transformation  rate of

S02 into SO4 = , Kdi is the dry deposition rate and Kwi is  the  wet

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deposition  rate,of  the  respective  pollutants.   The 3/2 factor



used in Equation 2.2 represents the ratio of molecular  weights




between SO4= and SO2.










Transport and Diffusion









     Dispersion generated by  small-scale turbulence  is not nearly



as significant as long term  transport and deposition processes



for regional-scale models such as RELMAP.  Because of this, the



model  simulates both  horizontal  and vertical diffusion through



simple parameterizations.   RELMAP  divides  the  atmospheric



boundary  layer  into three layers as  seen  in Figure 2.3.   The



first  layer  is between the surface and 200  m,  while the second



layer  is between 200 and 700 m.  The depth of the third layer is



variable,  depending  upon  the  seasonal-mean  maximum  mixing



height, and  is assumed to be 1150  m  during the winter, 1300 m



during the spring and fall, and 1450  m during the summer (Endlich



et al., 1983).



     During the unstable regimes of midday  periods,  pollutants



from both  area and point sources become well mixed up to  the



mixing height long  before  they  are  transported  a distance equal



to the spatial resolution of  the  grid.   Therefore,  it is assumed



that instantaneous and complete mixing occurs within the three



layers  of the model during the unstable daylight hours.  However,



after sunset, when mixing is prohibited by stable conditions,



point and area source   emissions are  confined  to  the separate

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       1450 -
       1300	
Figure 2.3   Three layer vertical profile with nighttime
             allocation of emissions.
layers  into which they are emitted.   As  again illustrated    in

Figure 2.3,  all area source emissions remain in Layer 1,  within

200  m  of the surface,  while emissions from point  sources  are

allocated into Layer 2,  accounting for typical plume rise, which

averages several hundred meters  (Briggs, 1984).

     RELMAP assumes that horizontal diffusion of the puffs occurs

                                 9

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 at a constant rate so that the size of  the puff  increases at a
 rate of  339  km2/h,  and that the distribution  of the mass  of
 pollutant in  the puff remains homogeneous at all times.  The puff
 expansion rate  is  based upon  work by  Pack  et  al.  (1978), who
 performed calculations on  long range trajectories.   Each  of the
 puffs is  transported using  vertically  weighted  and horizontally
 and temporally interpolated wind  fields  until the puff is either
 transported off  the grid, or the amount of mass in the puff falls
 below  a  predetermined  minimum  value.  The puff  remains  an
 indivisible entity.  Vertical  shear of the puff is not directly
 considered as the mass of  pollutant in each of the three  layers
 is transported in the  same direction and at the same speed. The
 transport  velocity of the puffs is determined by  integrating the
 mass-weighted u  and v  components of the  three layers, which are
 derived from the wind  velocities  from the grid cell containing
 the centroid of  the puff.  Surface winds are  used in the lowest
 layer,  850 mb winds are used in the  third  layer, and a weighted
 average of (0.2)  surface and (0.8) 850  mb wind  velocities are
 used  for the second  layer.


 Transformation
     RELMAP  treats  fine and  coarse  particulate  matter as
independent non-evolving pollutants, that is physical  and/or
chemical transformation of fine particulate matter to  coarse
particulate matter are considered negligible-  This premise is
                             10

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supported by particle size distributions obtained from monitoring

data (Suggs et al., 1981). As seen in Figure 2.4 the size

distribution of particulate matter generally indicates a bimodal

distribution with peaks in the fine and coarse particle size

ranges and a deep oscillating gap between 1 and 5 um.
-i 1.0
0.8
CO
Z
UJ
Q

3 0.6
O 30.4

w.r
w-SO.2
<
-------
homogeneous component simulates transformation that occurs under
dry conditions.
Seasonal variation in the transformation rates were examined
by Meagher et al., (1983) who determined that average morning
rates ranged from a low of 0.15%/h during the winter to a high
of 1.30%/h during the summer. In a similar study, Altshuller
(1979) concluded that noontime winter transformation rates
averaged about five times less than noontime summer
transformation rates.
Diurnal fluctuations were found to be much larger during the
summer months than during the winter months. Husar et al.,
(1978) found summer diurnal transformation rates that ranged from
a minimum of 0.5%/h during the night to a maximum of between 2.0
to 8.0%/h at solar noon. Conversely, Meagher and Olszyna (1985)
could only detect slight diurnal variation in the transformation
rates during the winter months.
More recent field studies have indicated that in-cloud
processes are also very important in the transformation of
pollutants. The rate of transformation can be increased by an
order of magnitude in saturated conditions, depending upon the
cloud height, precipitation efficiency and mass of SO-> in the
£t
mixed layer (Isaac et al., 1983). Based upon a theoretical
algorithm developed by Scott (1982), the magnitude of this
heterogeneous component was set to 7.0%/h during the winter,
11.0%/h during the spring and fall, and 15.0%/h during the
summer.
Figures 2.5 and 2.6 illustrate the relationship between the
composite transformation rate (heterogeneous and homogeneous

12
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20 25 30 35 40 45 50 55 60

NORTH LATITUDE, degrees

Figure 2.5. Latitudinal variation in the composite transformation rate

of S02 to S04=.
I
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