United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
Research and Development
EPA-600/S3-84-050  May 1984
Project  Summary
Physico-Chemical   Model  of
Toxic  Substances  in  the
Great  Lakes
Robert V. Thomann and Dominic M. Di Toro
  A physico-chemical model of the fate
of toxic substances in the Great Lakes
is constructed from mass balance prin-
ciples and  incorporates  principal
mechanisms of particulate sorption-
desorption, sediment-water and atmo-
sphere-water interactions, and chemical
and biochemical decay. Calibration of
the toxic model is through comparison
to plutonium-239 data collected in the
1970's  using a 23-year time variable
calculation and indicates that in general,
the sediments are interactive with the
water  column in the Great  Lakes
through resuspension and/or horizontal
transport. Fifty percent response times
of 239Pu following a cessation of load ex-
tend beyond 10 years with sediment
resuspension.
  The calibrated model was applied to
polychlorinated biphenyl (PCB) using a
high and low estimate of contemporary
external load and with and without vola-
tilization. The results of the application
using a 20-year calculation indicate that
a load level ranging  from 640 to 1390
kg/yr with volatilization (at an exchange
rate of 0.1 m/d) appears to be represen-
tative of observed surface sediment
data for the open lake waters. Fifty per-
cent response times for PCB following
cessation of load and including vola-
tilization varied from  less  than 5 years
to 10-20 years for the other lakes without
volatilization. Comparison of these re-
sponse times to decline of concentra-
tions of PCB in Lake Michigan indicates
that at least for that lake volatilization
is occurring at an exchange  rate of
about 0.1 m/d.
  Calculation using a  solids-dependent
partition coefficient for PCB indicate
that the total and dissolved PCB concen-
tration in the water column and sedi-
ment PCB concentration are affected to
less than an order of magnitude. In-
terstitial PCB concentration however in-
creases by about  two  orders  of
magnitude over the case with a solids-
independent  partition coefficient.
Higher exposure concentrations to ben-
thic organisms may then result with a
potential  route of PCBs to the top
predators in the food chain.

  Calibration of the model  to data on
benzo(a) pyrene confirms that on a lake-
wide scale the principal external source
in the atmosphere and for the larger
lakes such as Michigan the response
time of the lake  to external loads is
about 6-10 years  while for  Lake Erie
response time is about 2 years.

  Application of the model is cadmium
in the lakes, using a  solids-dependent
partition coefficient, indicates that the
lakes do not reach equilibrium over a
100-year period. For constant partition-
ing,  cadmium  concentrations  reach
steady state in about 10-25 years. An
estimate of the preceding 50-year aver-
age cadmium input ranges from 200-600
g Cd/km2-yr for  the upper  lakes to
2000-10,000 g Cd/km2-yr for Lake Erie.
Calculated high concentrations of cad-
mium in interstitial water (e.g. 10/ig/l)
indicate the importance of measuring in-
terstitial cadmium concentrations.

  This Project Summary was developed
by EPA's Environmental Research Labo-
ratory, Duluth, MN,  to announce key
findings of the research project that is
fully documented in a separate report of
the same title (see Project Report order-
ing information at back).

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Introduction
  There is an intense contemporary interest
in  the  impact of  toxic  substances  on
legitimate water uses in the Great Lakes.
Chemicals such as the PCBs and mirex in
Lakes Michigan and Ontario, have resulted
in the curtailment of recreational fishing ac-
tivities. Furthermore, there is a growing con-
cern  for the  effect of the  presence  of
potentially  toxic chemicals on  the  public
health of the Great Lakes basin population.
Because of these  concerns,  a variety of
questions are raised regarding the possible
recovery times of the Great Lakes following
the reduction or elimination of external  in-
puts.  In addition, interest in the fate of new
chemicals that may be  discharged to the
lakes  indicates a need to develop a model-
ing framework that can provide a basis  for
projecting the fate of such chemicals in the
water and sediment of Great  Lakes.
  This report  presents the results of the
development and  calibration of a physico-
chemical model for the Great Lakes. The
report begins with the basic theory  of the
model, the associated model equations and
useful simplifications of the model. A steady
state version of the model is then applied to
a two-dimensional representation of Sagi-
naw Bay PCB distribution. Plutonium-239 is
used as a calibrating variable for the Great
Lakes time variable model. Further applica-
tion is then  made to the PCBs in the Lake
system and the importance of solids depen-
dent partition coefficient and resulting sedi-
ment  diffusion is  then  explored.  Finally,
application of the model is also made to ben-
zoia)  pyrene and  cadmium in the Great
Lakes.

Theory

Suspended Solids Model
  Since  many chemicals, such as  PCBs,
sorb to suspended  particulate matter,  the
first step in  the development of the overall
model is the mass balance of  suspended
solids. In this work, a single class of solids
is considered and is intended to incorporate
inorganic solids and organic particulates. The
solids are considered at  steady state in  the
water column and sediment. The model does
not directly include horizontal transport of
the bed sediment. At steady state, the water
column solids  for a completely  mixed lake
is given by
                     WMa
             Wn =
                   Wa Ws
               m =
                    q +wn
                                     (1)
where m is solids concentration (mg/£), WMo
is the areai loading rate of solids (g/m2-yr),
q is the ratio of lake flow Q(m3/s) to volume
V(m3) (m/yr), and wn is the net loss of solids
from the water column  (m/yr) given by
                  Wrs+Ws
where wa is the settling velocity (m/yr), wrs
is the resuspension velocity (cm/yr) which
parametizes sediment/water  interactions,
and ws is the net effective sedimentation
velocity (m/yr), given by
                    wn M
             ws =   	           ,„,
                  PS (1-0)            (3)
forf, as the density of the solids (g/cm3) and
 the porosity of the sediment. All of the
above relationships apply in principle to a
multi-dimensional model where additional
terms for dispersion and advection must be
included.  The model  incorporates these
terms.

Toxic  Substances Model
  The theoretical construct for the physical-
chemical fate of a toxic substance in the
Great Lakes includes the following features:
  1. sorption-desorption mechanism of the
chemical with the suspended particulates in
the water column and sediment,
  2. loss of the chemical due to mechanisms
such  as  biodegradation,  volatilization,
chemical and biochemical  reactions, and
photolysis,
  3. transport of the toxicant due to advec-
tive flow transport, dispersion and  mixing,
  4. settling and resuspension of particulates
and diffusive exchange between sediment
and water column, and
  5. direct inclusion of external inputs that
may  be subject to environmental control.
  Although the computational framework is
multi-dimensional, the basic equations can
be readily seen for a single completely mixed
lake, where the mass balance for the total
toxicant is given by
     V dc-r/dt = WT - Q CT - Wa fp CT
  + wrs fps CTS + KLA (fds CTS/^S - fd CT/)
    -KVcr+k,, A(cg/He-fdCT/)    (4)
This equation is derived on the assumption
that  all  sorption-desorption  kinetics are
"fast," linear and reversible. In Equation (4),
the subscript "s" indicates the sediment, the
total toxicant is CT (^g/^(bulk)) given by
             cT = Cp + cd              (5)
where cd is the porosity corrected dissolved
concentration (^g/C(bulk)) and cp is the par-
ticulate form of the toxicant (jug/Hbulk)) and
is given  by
                cp= rm               (6)
for r as the toxicant sorbed to the solids
(^g/g(d); g(d) = grams dry weight).
  Also in  Equation (4), WT is the external
input of the chemical (kg/yr), A is the sur-
face  (sediment) area  (km2), KL is the  sedi-
ment  water  diffusive transfer  coefficient
(m/d), k(  is the volatilization transfer coef-
ficient (m/d), cg is the toxicant concentra-
tion in the atmosphere overlying the water
(ng/m3), H« is the Henry's constant, i.e., the
partitioning  between  the  gaseous  and
aqueous phase, K is an overall loss rate (d"1)
given by
            K = Kd fd + Kp fp          (7)
and fd and fp are the fraction of the total in
the dissolved and particulate forms respec-
tively and are determined from
            fd = (1  - TT-'Mf          (8a)
                   TT'M
              fp -
                  1+TT'M
                                    (8b)
In these latter equations, n' is the porosity
corrected partition coefficient (I /kg) given
by
               IT' = r/cd .            (9)
The equation for the total toxicant in the sur-
face sediment segment is

       dcrs       . ,          . ,
     Vs ^—  = Wa A fp CT - Wrs A fps CTs

               + KLA(fd CT/0 - fds CTs/*s)
             - Ws A CTS - Ks Vs CTs
                                    (10)
where
           KS = Kds fds "*" Kps fps-       (11)
Similar equations are written for sediment
segments below the surface sediment layer.
  The report explores these equations and
also the simplifying case of the steady state
condition where basic relationships between
external chemical  loading  and  resulting
chemical concentrations in the lake can be
derived as a basis for allocation of chemical
loading.

Model Calibration
  The time scale of the model is considered
to  be long  term,  i.e., year to  year. The
physical segmentation of the model con-
siders the Lakes to be completely mixed with
the exception of Lake Erie (Figure 1). This
Lake  is divided into three basins; west, cen-
tral, and east to reflect varying  regions of
solids deposition  and water column  solids
concentrations. In addition, Saginaw Bay is
included as a separate embayment from Lake
Huron to represent a more local region in-
teracting with a large lake. Three sediment
segments of 2 cm each in depth are included
under each  of the lakes or region  of lake.
This results in a model with eight water col-
umn  segments and 24 sediment segments
totaling 32 segments.
  The calibration procedure was as follows:
(a)  From a review of data on fine grain solids
loading to the Lakes, net  depositional flux
of  solids, and water  column  suspended
solids concentrations. Equation (1) was used
to provide first estimates of wn, the net loss

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                                                               N
  Sediment
Segmentation
Lake Michigan
                                   Lake Erie
                                                                   0    50  100

                                                                   Statute Miles


 Figure  1.    Great Lakes and Sagmaw Bay and sediment segmentation used in model.
 rate of solids from the water column. From
 assigned porosity in the surface sediment
 layer, particle density and net flux of solids
 to the sediment, the net sedimentation rate
 is computed from Equation (3); (b) With the
 estimate of the net loss of solids, wn, a range
 of particle settling velocities were assigned
 and the  resuspension velocity necessary to
 maintain the solids balance was computed
 from Equation (2) as

           wr, =  w. ( — - 1) .
                     Wn

 (c) Since  there are an  infinite number of
 combinations of settling and resuspension
 velocities that will result in the same solids
 balance,  the  time variable plutonium-239
 model was numerically solved to provide the
 tracer calibration. All decay mechanisms and
 sediment diffusion were assumed to be zero
 and a sensitivity analysis using three values
 of plutonium solids partitioning was con-
 ducted.
   Figure 2 shows the  results of the plu-
 tonium calibration under different conditions
 on  particulate settling  (for w0  =  w,«,,
 resuspension  is zero). The calibration is not
 favorable for  the case of no resuspension
 and is improved by including the resuspen-
 sion parameter. No significant difference was
 noted between 2.5 and 5 m/d. Additional
 sensitivity analysis discussed in the full report
 supported the conclusion that some interac-
 tion of the sediment with the water column
 is occurring in the Lake system.
                        PCB Mass Balance
                          The range of contemporary (i.e., approxi-
                        mately within the past 5-10 years) external
                        total PCB loads to the Great Lakes was
                        estimated at a high and low load level. The
                        estimated ranges of PCB loads incorporate
                        three components: the atmospheric input,
                        tributary loads and direct point source inputs
                        from  municipal and  industrial   sources.
                        Rather than attempt to describe each of
                        these components in detail and recognizing
                        the wide variability in some of the reported
                        data, a range of concentrations or loading
                        rates was applied. The computations were
                        then made at two load levels (high and low)
                        and with and without volatilization. A con-
                        stant partition coefficient of 100,000 t /kg
                        was used throughout and a volatilization ex-
                        change  coefficient  of  0.1  m/d was
                        estimated.
                          The results of the four conditions (high
                        and  low load  levels,  with and without
                        volatilization) after running the preceding
                        calibrated model with zero initial conditions
                        for 20 years to approximate steady state, are
                        shown in Figures 3 and 4. Comparison to the
                        limited water column and sediment data in-
                        dicates  that the upper load level without
                        volatilization overestimates the data in the
                        open lake waters. The effect of volatilization
                        of PCB as indicated in Figure 3 is to reduce
                        the steady state water column concentration
                        by 50-70%  except for Lake Erie where the
                        reduction due to volatilization is about 30%.
                        This reflects the higher fraction of PCB in the
                                                                   particulate phase for Lake Erie due to the
                                                                   higher solids concentration. The inclusion of
                                                                   volatilization also has a significant effect on
                                                                   the time to reach equilibrium. For example,
                                                                   for Lake  Michigan  at  the  upper level of
                                                                   loading without volatilization, the  time to
                                                                   equilibrium in the water column is greater
                                                                   than 20 years in contrast to less than 10 years
                                                                   when volatilization is included.
Plutonium and  PCB
Response Times
  Simulations were made of the response of
the Great Lakes system to an instantaneous
elimination of the external load  using the
preceding model.  For plutonium, the results
indicated that the time to  reduce the con-
centration by 50% is less than 5 years when
resuspension is not included but increase by
about an order of magnitude under resus-
pension is incorporated. For PCB, the effect
of volatilization in the 50% response time (in-
cluding resuspension) was investigated and,
as an example, it was calculated that for
Lake Michigan the response time varies from
15-20 years without volatilization to 1-2 years
with volatilization.


Effect of Solids Dependent
Partitioning and Sediment
Diffusion
  An evaluation was made of the sensitivi-
ty of the model to a hypothesized depen-
dence  of  the partition coefficient  on the
solids  concentration. For  plutonium, the
results showed that settling velocities of
2.5-5.0 m/d with or  without solids-depen-
dent partitioning  provide an approximately
equal representation  of the observed data.
For PCB, a compilation of published data in-
dicated that the PCB partition coefficient did
exhibit a marked dependence on  the solids
concentration at levels of less than 1  ng/£
to sediment solids concentrations.
  Two cases of solids dependent partition-
ing of PCBs were therefore examined:
  a) 7i  = 73,990  M- 435,  and
  b) n = 25,120 M-'  2 for solids < 10 ng/f
     n = 73,900 M- 435 for solids > 10 ng/f.
  The calculations indicated that the total
and dissolved water PCB concentrations are
not sensitive in a significant way to the
assumption on partitioning. The principal ef-
fect  on the  dissolved  component is in
Western Lake Erie where the dissolved con-
centration increases by a factor of three. In
all other lakes, however, for practical pur-
poses, the total and dissolved concentrations
are unaffected by the partitioning assump-
tion including the  case of a constant solids-
independent partition coefficient. The sur-

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is
<3
3
f
1 0.5
n
\ Superior
\
\
\ ?
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\
_ \
\

^^"M^ AT ii 'jj* ^
T T T T
III

1 1 1 1 1 1
      1971  72   73   74   75  76   77      1971  72    73  74   75   76   77
                      Year                                  Year
                         1.0
                         0.5
                                       Huron
	 M
-*-
^ = IVne,
-2.5 m/d
= 5.0 m/rf
                                          _J	I	1	1
                          1971  72  73   74  75   76   77
                                         Year
                                                           Ontario
                                                                  s = Sept.
                                                                  A = Aug.
       1971  72   73   74   75   76  77      1971  72   73   74  75  76   77
Figure 2.    Comparison of calculated 239'240pt/ concentration {fC, /I) in the water column for all
            lakes to  1971-1977 data for three conditions of the paniculate settling velocity.
            n = 400,000 I/kg.
face sediment concentration was also not
markedly affected (to order of magnitude)
by the partitioning assumption, although a
decline of about 50% is evident in the lake
sediment and a decline of about  70%  is
calculated  for  the  surface  sediment  of
Saginaw Bay.
   These reductions  in sediment PCB par-
ticulate concentration reflect the assumed
reduced partitioning  at the high solids con-
centrations and are, therefore, subsequently
reflected in the PCB concentration of the in-
terstitial water of the surface sediment. It is
in the interstitial water that the effect of the
solids-dependent partitioning was most pro-
nounced. Increases  in the dissolved  PCB
concentration of about two orders of magni-
tude were calculated.
   For Lake Michigan, as an example, the in-
terstitial concentration of PCB as calculated
for a constant partition coefficient is about
0.25 ng/l. For a variable  partition coefficient
(Relationship (b) above), the concentration
increases to about 30 r\g/(. Values of pore
water PCB at three stations in southern Lake
Michigan have been reported at levels of 159,
214, and 342 ng/l which is about one order
of magnitude higher than that calculated.
However, the estimate of 30 ng/7 represents
a  lake-wide average including  regions of
nondeposition. One would, therefore, expect
an observed lake-wide average to  be less
than individual core  samples.
   The calculation on the sensitivity of the
PCB distribution  in  the Great Lakes to a
sediment-dependent partition coefficient in-
dicated that since the increased interstitial
PCB concentration in the sediment is about
two orders of magnitude higher than the
overlying water dissolved PCB concentra-
tion, one would expect  benthic organisms
to carry a significantly higher body burden
than organisms exposed solely to the water
column and as a result would be a potential
significant source of PCBs to top predators
in the food chain.
   Since the interstitial PCB component  is
potentially significant and since the issue of
solids-dependent partitioning is of contem-
porary  interest   on  constructing   mass
balances of PCB, it is  recommended that ad-
ditional sampling of  pore water PCB and
PCB concentration in benthic organisms be
conducted  in various Great Lakes regions.

Application of Model to
Benzo(a) Pyrene and Cadmium
   The physico-chemical  model was further
applied to two other chemicals: (a) benzo(a)
pyrene, a polycyclic aromatic hydrocarbon
and b) cadmium,  a  representative metal.
Figure 5 summarizes the results for the BaP

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                      (4J

            Superior
Huron
 5  10\
             fflm
                       1(2}
External Load
Condition
Upper Level
Lower Level
Volatilization Rate
(m/d)
0.0
1
fl
0.1
n
0
                                                                                               I ) = Ret. No.
            Michigan                 Saginaw Bay                 Ontario

figure 3.    Calculated water column total PCB concentration (ng/lj for conditions on external load and volatilization rate.
calculations and indicates  that  a more
 avorable  (but not totally desirable) com-
parison to observed data is obtained at the
higher BaP partition coefficient of 100,000
7 /kg. On the basis of this application of the
physico-chemical model to BaP in the Great
Lakes, it was concluded that the estimate of
the BaP partition coefficient obtained from
published empirical relationships is probably
low by about an  order of magnitude for the
Great Lakes system, and with an increased
BaP partition coefficient and assuming loss
due to volatilization, the physico-chemical
toxic substances model of the Great Lakes
approximate observed BaP water column
and sediment data to order of magnitude.
  The application of the model to cadmium
in the Great Lakes indicated that the degree
of any dependence of the cadmium partition
coefficient with solids has a marked effect
on time to steady state and interstitial cad-
mium concentration. Under a solids-depen-
dent  cadmium  partition  assumption,  the
Great Lakes, especially the upper Lakes, do
  t reach a steady state condition after 100
    years of constant loading while under a con-
    stant partition coefficient for cadmium, the
    Lakes  do reach an  equilibrium  condition
    varying from about  25 years  for  Lake
    Michigan to 10 years for Lake Erie. Also the
    concentration of cadmium  in the  Lakes
    would be expected to increase by about 60%
    over the next 50 years if the average cad-
    mium  loading for the preceding 50 years
    continues.
      Based on assumed sediment  cadmium
    concentrations for Lake Erie, it is estimated
    that the cadmium concentration in the water
    column is  about an order  of magnitude
    higher  than the other  Lakes.  Finally,  the
    results indicate that if loads are projected to
    increase, then cadmium concentrations in
    the Lake system may increase  to levels of
    concern.
    References
     1. Swain, W.R. 1978. Chlorinated organic
       residues in fish, water and precipita-
       tion from the  visinit of Isle  Royale,
   Lake Superior. J. Great Lakes Res.
   4(3-4):398-407.
2. Rice, C.P., B.J. Eadie and K.M. Erstfeld,
   1982.  Enrichment  of  PCBs  in  Lake
   Michigan surface films. J. Great Lakes
   Res. 8(2):265-270.
3. Richardson, W.L., V.E. Smith, and R.
   Wethington, 1983.  Dynamic mass bal-
   ance of PCB and suspended solids in
   Saginaw  Bay —  A case study. In D.
   Mackay, S. Paterson, S.J. Eisenreich,
   M.S. Simmons (Eds.). Proc.  Physical
   Behavior  of PCBs in the Great Lakes.
   Ann Arbor, Mich. pp. 329-366.
4. Eisenreich,  S.J.,   P.O.  Capel,  B.B.
   Looney, 1983. PCB dynamics in Lake
   Superior water.  In D.  Mackay, et al.
   (Eds.) Physical Behavior of PCBs in the
   Great Lakes, Ann Arbor Science Press,
   Ann Arbor, Michigan, pp. 181-211.
5. Frank, R., R.L. Thomas, H.E. Braun, J.
   Rasper and R. Dawson, 1980. Organo-
   chlorine insecticides and PCB in the sur-
   ficial sediments of Lake Superior (1973).
   J. Great Lakes Res. 6(21:113-120.

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   Eisenreich, S.J., G.J. Hollod, and T.C.
   Johnson. 1979. Accumulation of poly-
   chlorinated biphenyls (PCBs) in Surficial
   Lake Superior Sediments. Atmospheric
   Deposition - Em. Sci. & Tech., Vol. 13,
   pp. 569-573.
   Frank, R., R.L. Thomas, H.E. Braun,
   D.L. Gross, and T.T. Davies, 1981. Or-
   ganochlorine insecticides and PCB in
   surficial  sediments  of  Lake Michigan
   (1975). J. Great Lakes Res.  7(1):42-50.
   Eadie, B.J., M.J. McCormick, C. Rice,
   P. Le Von and M. Simmons, 1981. An
   equilibrium model for the partitioning of
   synthetic organic compounds  incor-
   porating  first-order  decomposition.
   NOAA, Great Lakes Environmental Re-
   search Lab., NOAA Tech. Memo. ERL,
   GLERL-37, 34 pp.
   Armstrong, D.E. and D.L. Swackhamer,
   1983. PCB accumulation in southern
   Lake Michigan sediments:  Evaluation
   from core analysis. In D. Mackay, et al.
   (Eds.), Physical Behavior of PCBs in the
   Great Lakes, Ann Arbor Science Press,
   Ann Arbor, Michigan, pp. 229-244.
     10. Frank, R., R.L. Thomas, M. Holdrinet,
        A.L.W. Kemp, N.E. Braun, and R. Dow-
        son, 1979a. Organochlorine insecticides
        and PCB in the sediments of Lake Huron
        (1969) and Georgian Bay and North
        Chennel (1973). Science of Tot. Env.,
        13:101-117.
     11. Richardson,  W.L. (Personal  com-
        munication).
     12. Frank,  R.  1977.   Anthropogenic in-
        fluences of sediment quality at a source.
        Particles and PCBs. In  Shear,  H. and
        A.E.P. Watson (Eds.), Proc. Workshop
        on the Fluvial Transport of Sediment-
        Associated Nutrients and Contaminants.
        International Joint Commission, Wind-
        sor, Ontario, 309 pp.
     13. Frank, R., R.L. Thomas, M. Holdrinet,
        A.L.W. Kemp, and H.E. Braun. 1979b.
        Organochlorine insecticides and PCB in
        surficial sediments (1968) and sediment
        cores (1976) from Lake Ontario. J. Great
        Lakes Res.  5(1):18-27.
     14. Eadie, B.J., 1983.  Polycyclic aromatic
        hydrocarbons in the Great Lakes. GLERL
Cont. No. XX. NOAA, GLERL, Ann Ar-
bor,  Mich., 23 pp.
   8001-
                             800 I
                 SOOp
Extended Load
Condition
Upper Level
Lower Level
Volatilization Rate
(m/d)
0,0
1
R
0.1
n
0
                                                                                        - Mean & Range; ( ) = Ref. No.
            Michigan
Saginaw Bay
                                                                 Ontario
Figure 4.    Calculated surface sediment PCB concentration (ng/g) for conditions on external load and volatilization rate and comparison to observed
            data

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  woo

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     R.  V. Thomann and D.  M. DiToro are with Manhattan College, Environmental
       Engineering and Science, Bronx, NY.
     W. L. Richardson is the EPA Project Officer (see below).
     The complete report, entitled "Physico-Chemical Model of Toxic Substances in
       the Great Lakes," {Order No. PB 84-170 828; Cost: $17.50, subject to change)
       will be available only from:
             National Technical Information Service
             5285 Port Royal Road
             Springfield, VA 22161
             Telephone: 703-487-4650
     The EPA Project Officer can be contacted at:
             Large Lakes Research Station
             Environmental Research Laboratory—Du/uth
             U.S. Environmental Protection Agency
             Grosselle, Ml 48138
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
                "
                                                                                 
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