International Symposium on
      Gas Transfer at Water Surfaces
Cornell University
 Ithaca, New York
June 13-15,
    1983
      -•-.



                                               * .
                                              ^
                  SYTPOSIUri
                ABSTRACTS OF XIBiTIFIC PAPERS

              W,H, BRUTSAERT AND G,H, JIRKA (EDITORS)
            SCHOOL OF CIVIL AND ENVIRONT'ENTAL
                   CORNELL UNIVERSITY
                       1983

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                        International Symposium on
                   GAS TRANSFER AT WATER SURFACES
                                                i.-

                             Cornell University
                             Ithaca, New York
                             June 13-15, 1983
Presented by:
 School of Civil and Environmental Engineering
 and
 Tne Center for Environmental Research
Supported by:

U.S. Environmental Protection Agency


Sponsored by:

American Chemical Society
American Geophysical Union
American Meterological Society
American Society of Civil Engineers
International Association for Hydraulic Research
U.S. National Science Foundation
World Meteorological Organization
SCIENTIFIC ADVISORY COMMITTEE
S.A. Kitaigorodskii
J.L. Lumley
D. Mackay
K.O. Munnich
D.J. O'Connor
N. Yotsukura
        Johns Hopkins University, USA
        Cornell University, USA
        University of Toronto, Canada
        Universitat Heidelberg, Germany
        Manhattan College, USA
        U.S. Geological Survey, USA
ORGANIZING COMMITTEE

W.H. Brutsaert
G.H. Jirka
T.O. Barnwell, Jr.
E.H. Bryan
E.R. Holley
G. Levine
J. Nemec
        Cornell University (Symposium Co-Convener)
        Cornell University (Symposium Co-Convener)
        U.S. Environmental Protection Agency
        U.S. National Science Foundation
        University of Texas
        Cornell University
        World Meteorological Organization
Editors'  Notes:   1)

                     2)
Abstracts  are arranged in  alphabetical order by
name of first author.
This constitutes the  first part  of the Symposium
Proceedings.  The second part will consist  of
completed  manuscripts  that will  be referred prior
to  publication by D. Reidel Publishing Company.

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                                                   Barnhart
          THE IMPACT OF SURFACE ACTIVE AGENTS ON MASS TRANSFER

                                   By

                            .Edwin L. Barnhart
                      Southern Methodist University
                              Dallas, Texas



     The method in which surface active organic compounds interfere with

mass transfer  across the gas-liquid  interface  has long been  a concern

of practitioners in waste treatment.  The phenomena causes a significant

decrease in transfer efficiency in many systems and therefore, negatively

influences the economics  of waste treatment.  Engineers have,  over the

last  several  decades,  directed  many efforts  to  understanding  this

phenomena.  To-date, very little  progress  has been made in presenting a

satisfactory explanation of system behavior.



     The coefficient alpha,  a,  has been employed to define the relative

transfer  efficiency in water containing  impurities  as opposed  to the

transfer rate  in  pure  water.  Alpha have been shown  to vary from waste

to waste  and  even  with different  aeration devices  in  the  same waste.

Values of alpha from 0.35 to 1.6  have been reported by various investi-

gators.   Alpha  has  been  observed  to  change  during  treatment  and

generally  tends to  rise as treatment reactions  remove  organics  from

solution.



     In order  to better  understand  the phenomena,  it  is necessary to

examine the nature  of the mass transfer coefficient K..a.   K,a is equal

to the liquid  film coefficient  K..  multiplied by the  area/ p  through

which  transfer occursp>±divided  by the tank volume.   The  liquid film

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                                                       Barnhart

                                                       Page 2


 coefficient and the  surface area  available for  transfer are directly


 effected by the presence of surface  active agents.  The paper explores


 in detail the effect  of this relationship.





      The liquid film coefficient ^ has been expressed  in a variety  of


 manners  by  different  investigators.   The principal  phenomena which


 influence the coefficient appear to be  the diffusivlity  of the solution


 and the  thickness  of the  film at the  liquid-gas boundary.   The  film


 thickness is, of course, significantly  affected by the  accumulation  of


 molecules at  the  surface.  This phenomena being directly  related  to


 their surface activity.   The diffusive  properties of the solution may


 also be affected by the  presence of organic materials.  Surface  tension


 is one method of estimating the relative build up of materials in the


 surface layer.  Investigations  show,  that  the rate  at which material
                                    i<

 accumulates in  the  surface and their  tendency  to  be  surface active


 rather than be dispursed in the system is a function of the nature  of


 the  material, "{he  manner  in which  surfaces tension is  measured must


 reflect this  dynamic relationship to accurately relate to  the  system.





     The  presence of  surface active agents in  a  system  also affect the


 relative  area available for transfer.   This is accomplished in a bubble


 system by  decreasing the  average  size  of the  bubble  that  will  be


produced  at a given air  flow under fixed conditions  of  pressure.  In  an


aeration  system where surface  aeration  is the principle mechanism,  it


can  also  be shown that  the actual surface configuration  is altered  by


the  the presence of  surface active materials.   The degree to  which  a


given  surface active  material will affect the  surface configuration  of

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                                                      Barnhart
                                                      Page  3

an  aeration  system  is  a  function  of  the  aeration device  and  the

particular surface active material.  Furthermore, it can be demonstrated

that  the  same  surface  active  material  under  different  turbulence

conditions will  have a significantly different  effect on  the surface

generated.



     Combining the  two part impact  of surface active  materials,  it is

possible to  describe in a general fashion  the forces controlling alpha

in a dynamic situation.  This behavior model is useful in estimating the

type  of  aeration  system  which  will be   least impacted  by  various

materials.   The  model  does  not totally  define the phenomena  but does

provide  a  significant  additional insight  into  this complex surface

reaction.

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                                                Bilstad  &  Lightfoot

DETERMINATION OF NITROGEN AND OXYGEN MASS TRANSFER BY GAS CHROMATO-
GRAPHIC TECHNIQUES

Torleiv Bilstad and E.N. Lightfoot
Environmental Engineering Division,
Rogaland Research Institute, 4001 Stavanger, Norway and
Chemical Engineering Department, University of Wisconsin  , Madison
WI 53706, USA

The purpose of this study was to determine the reason for preferential
nitrogen absorption during aeration, and to determine what was needed
to prevent excessive nitrogen supersaturation.

This  problem was first approached by a theoretical analysis which
suggested that preferential nitrogen absorption results primarily
from  the lower nitrogen solubility in water as compared to oxygen,
and that it is aggravated by the use of small air-water ratios.

The remainder of the study was devoted to experimentally  testing this
hypothesis and consisted of two phases:  i) development of a rapid
assay method for simultaneous determination of dissolved  nitrogen
and oxygen, and ii) a study of aeration with mixed gases  in a U-tube.

Preferential  nitrogen absorption is prevented by employing high air-
water ratios  and low pressures during aeration.  The experiments
performed in  this research do much to clarify the situation investigated
and show that the U-tube aeration of clear liquids can be  explained
both  qualitatively and quantitatvely on the basis of available  transport
theory.

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                                                     Bilstad & Lightfoot
                                                     Page 2
An accurate in situ gas chromatographic technique was developed for
simultaneous determination of dissolved gases in water.  Samples
were prepared by exposing known volumes of helium carrier gas to
the water under analysis across a non-selective Silastic membrane in
tubular form.  The membrane diffusion cell was incorporated into the
sampling circuit of either a Carle 8515 or a Carle 2153 gas chromato-
graph.

Response of the system to dissolved gas partial pressure is linear
and interference between the gases is negligible.  The standard devia-
tion of individual measurements from the expected value is about
0.5 percent for both nitrogen and oxygen.

The average liquid phase mass transfer coefficients for oxygen and
nitrogen are not significantly different.  A 15 meter long U-tube
served as the experimental mass transfer device allowing photographic
techniques in the evaluation of gas-liquid two phase flow.

Experimental mass transfer efficiencies were in good agreement with
predictions based on observed flow patterns and the surface stretch
mass transfer model of Angelo and Lightfoot (1968).

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                                                                Bliven et al


                   VELOCITY  FIELD  BELOW SURFACE GRAVITY WAVES
                                  L. F- Bliven
                          Oceanic  Hydrodynamics,  Inc.
                              107  Meadow!ark Drive
                              Salisbury, MD  21801

                           N.  E. Huang and S. R.  Long
                        NASA  Goddard Space Flight Center
                           Wallops Flight Facility
                           Wallops Island, VA 23337
                                     USA
      Waves  are an  expression  of  surface energy and provide information con-

 cerning surface layer  dynamics.  Although in the upper mixed layer of the

 ocean turbulence can be  generated by many mechanisms, breaking surface wave

 is one of the  dominant mechanisms.  Because the turbulent energy is a con-

 trolling factor in  the determination of mixed layer depth, drift current,

 surface wave damping,  etc., it has become a central subject of investigation

 in the study of ocean  surface layer dynamics.  The purpose of this study is

 to measure  the  velocity  field beneath surface waves and define the statistical

 properties  of  the flow field as a means to understand the surface layer

 turbulent structure.

      Experiments are conducted at the NASA Wallops Island Wind Wave Research

 Facility.   The wind wave tank (Figure 1) has a test section 20 m in length

 and a  cross section 1 m in width by 1.25 m in depth.   Its operational  water

 depth  is 0.75 m with the remainder for airflow.   The wind is generated by a

 suction fan and recirculating ducts.   The tank is also equipped with a

 hydraulic powered,  servo-controlled paddle wave maker.  During these experi-

ments, both  paddle  and  wind generated waves  are studied.

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                                                                 Bliven et al.
                                                                 Page 2
      The water  surface  elevation  is measured by capacitance probes which pro-

 vide  a  linear response  with  surface elevation changes.  The water velocity

 field is measured  by  a  two channel backscatter laser Doppler anemometer

 system.  A  4-watt  argon laser  provides adequate signal to noise  ratio and

 allows  separate  light frequencies to be employed for the vertical and hori-

 zontal  (long channel) velocity measurements.  Because the wave flow field

 has reversing velocities, Bragg cells are employed to remove flow direction

 ambiguities.  The  tank  water is seeded with 2-micron silicon-carbine parti-

 cles  and typical data rates  are 200-800 samples/sec.

      Wind wave  velocity fields are complex systems that can be represented as

 the sum of  a mean  drift current,  wave orbital components and turbulence.   The

 turbulence  component  can  be  produced by the vertical shear of the mean  current,

 and surface wave breaking.   To quantify these various mechanisms, two experi-

 ment  series are  being conducted in which  (a) sinusoidal or random waves with

 a fixed frequency  distribution but varying amplitude are generated, and (b)

 fixed amplitude  random  waves with increasing wind stress.  Because a velocity

 measurement as  a function of time includes all the various components which

 can not be  individually measured, their quantification depends upon numerical

 data  reduction techniques.   The mean velocity is defined as the  record  time

 average.  We employ wave  theory and surface elevation data to decouple  the

wave component from the velocity  spectra such that the residual  spectra are

employed as estimates of  the turbulence spectra.   Cross spectra will be em-

ployed to examine  the phase  relationship between the horizontal  and vertical

velocities.  Preliminary  data  from the paddle wave and the wind wave study

which show  general trends which we intend to examine further are included

here.

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                                                                BTTven et al.
                                                                Page 3


      The  paddle wave study Is designed to investigate wave velocity fields

 in  which  horizontal mean currents are minimized as a turbulence generating

 mechanism.  A  series of random wvae experiments with increasing amplitude

 (Figure 2)  has been conducted.  Figures 3 and 4 show that while the mean

 horizontal  and vertical velocities are small, the surface waves exert a stress

 which  decays with depth and also increases as the wave slope increases.

 Figure 5  displays a typical comparison of a measured horizontal spectrum and

 velocity  spectra computed from the surface elevation spectrum and wave theory.

 Three  frequency ranges can be identified in Figure 5: (1) low frequency tail,

 (2) wave  dominated region, and (3) high frequency tail.   Review of velocity

 spectra data show that the low frequency tail grows in amplitude as the wave

 slope  increases and it decays slowly with depth.  The wave dominated region

 decays exponentially with depth and "reddens" with depth as shorter wavelengths

 decay  more  rapidly than the longer wavelengths.   Figure 6 shows a typical pro-

 file of turbulence spectra.  The vertical  scale on these turbulence spectra

 suggest that the velocity power spectrum prediction must be accurate to the

 order  of  0.1% if it is provide turbulence estimates with the precision observed

 in  the low  and high frequency tails.   The high frequency tails typically decay

with frequency at about -5/3 rate.   Integrals of the turbulence spectra have

 been employed to derive turbulence energy decay profiles as shown in Figure

 7.   Regression analysis of these  profiles  indicate that both power law and

exponential  decay  models  fit the  data  well  and more data would be necessary

to determine which  one  of  these  models provides  a better estimate.  Vertical

integration  of the  turbulence  energy  profiles provides an estimate of the

total turbulence  energy which  has  been compared  (Figure 8) to a wave turbu-

lence model  derived  from a  earlier  model  proposed by Longuet-Higgins  (1969).

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                                                                Bliven et al.
                                                                Page 4


This graph shows that the turbulence energy increases with wave steepness but

the total level is greater than predicted.  This difference may be due to

inaccuracies in turbulence energy levels in the wave dominated region of the

turbulence spectra and further work is. being conducted to validate the data.

Figure 9 displays a typical velocity probability density distribution.   These

distributions are very close to normal with neither high skewness  or kurtosis,

     The work done to date on the random paddle plus wind stress is very

limited, however, a few trends have been observed but not fully quantified.

We have seen that at maximum paddle drive with no wind, surface wave breaking

is not very active.  To achieve rolling and spilling waves, wind stress plays

a crucial part.  Although this may seem to be an obvious statement, its

importance lies in the fact that it suggests that accurate models  of wave

generated turbulence will probably require more than one independent variable

and two likely choices are wave slope and the ratio of wind shear  velocity  to

say wave phase speed or maximum orbital velocity-



Longuet-Higgins, M. S. , 1969: "On Wave Breaking and the Equilibrium Spectrum

of Wind-Generated Waves," Proc. Roy. Soc. , A310, 151-159.

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                                       H. Broecker and Si ems

The role of bubbles for gas  transfer  from water to air at higher
windspeeds. Experiments in  the wind wave facility in Hamburg.

H.Ch.Broecker, W.Siems
University of Hamburg
Department for Applied Chemistry
Martin Luther King-Platz  6
D 2000 Hamburg 13
Germany
Ab s t r a c t

Measurements of  the evasion  rate  of  CO-  and 0_ from fresh water
into the air which have been performed  in the wind wave facility
in Hamburg show  an increased slope of  the k vs.  u-curve at wind
speeds above 11-13 m/s  (  fig.l  ). In order to test the hypothe-
sis that this effect is caused  by the  additional transport of tho-
se gases to the  air-water  interface  by  means of  air bubbles re-
sulting from breaking waves, the  bubble  spectrum has been inves-
tigated as a function of  fetch  (  fig.2  ), windspeed ( fig.3 ) and
depth ( fig.4 ). A photographic method  was used  to analyse the
bubble distribution„
Bubbles are observed for  wind speeds as  low as 7 m/s. The bubble
density N(r) as  a function of radius r  is very similar to those
that have been observed by Kolovayev and Johnson and Cooke in ex-
                                  -3-4
periments in the open sea, N(r)/~ r     .  With no  wind-induced tur-
bulence being present,  the rise velocity of the  bubbles correspon-
ded to Stokes1  law. Turbulence  increased both the mean and the va-
riance of the rise time distribution.
For a quantitative mass balance the  following assumptions were
made :
- Uptake of gas  from supersaturated  water only during rise time
  of bubble.
- Transfer resistance to  the bubbles describable with the film
  model. No influence of  bubble motion  upon film thickness.
- All gases behaving ideally. No  enhancement of  the transfer rate
  of any gas component  due to the presence of others.

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                                            H. Broecker and Siems
                            - 2  -
- Only bubbles with  radii  20 yu < r < 2000 AI relevant for gas trans-
  port.
Agreement between  calculated  and observed enhancements of gas ex-
change of CO^ and  0«  from  fresh  water supersaturated with both
gases, as a function  of  windspeed,  is rather good ( fig.5 ).  The
fact that this enhancement is  more  pronounced for 09 than for C0_
is a consequence of  the  differences in solubility ( Merlivat  and
Memery 1982 ). On  the basis of the  laboratory results, some com-
ments are given concerning the possible role of air bubbles in
the gas transfer to  and  from  the open ocean.
Figures
1) Mass exchange  coefficient  k for the evasion of 0? (o) and C0_
   ( • and + )  as a function  of windspeed in the Hamburg wind wave
   facility.
2) Fetch dependence  of  number of  bubbles  per liter with diameter
   d = 300 u  at a depth of  20 cm.  Parameter:  windspeed.
3) Depth dependence  of  number of  bubbles  per liter with diameter
   d » 300 lu  as a function  of windspeed.  Fetch:  11.5 m. Parame-
   ter: depth  range.
4) Number of  bubbles  per liter as  a function of  bubble diameter
   ( 10~^ m )  at  a fetch of 11.5  m.  Parameters:  windspeed and
   dep th.
5) Calculated  enhancement of  mass  transfer coefficient k for 0
   (+) and CO- (•)  at  higher windspeeds.

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                                                W. Broecker  (Invited  Keynote Paper)
                                  ABSTRACT

                GAS EXCHANGE MEASUREMENTS IN NATURAL SYSTEMS

                            Wallace S. Broecker
                    Lamont-Doherty Geological Observatory
                            Columbia University
                            Palisades, New York

     Our direct knowledge of the rates of gas exchange in lakes and  the ocean
                                                         U   222n      ,  3U
is based almost entirely on measurements of the isotopes   C,    Kn, and  He.
The distribution of natural radiocarbon has yielded the average i.Tiate^dfYlCCL
exchange for the ocean and for several closed basin lakes-  That of  bomb  pro-
                                                          0 *7 0      *? *? f\
duced radiocarbon has been used in the same systems.  The    Rn to    Ra  ratio
in open ocean surface water has been used to give local short term gas exchange
rates.  This method generally cannot be used in lakes, rivers, estuaries  or  shelf
areas because of the input of radon from sediments.  A few attempts  have  been
                       3
made to use the excess  He produced by the decay of bomb produced tritium in
lakes to give gas transfer rates.  The uncertainty in the molecular  diffusi-
vity of helium and in the diffusivity dependence of the rate of gas  transfer
holds back the application of this method.  A few attempts have been ma'de to
                                              7 9 fa       o
enrich the surface waters of small lakes with    Ra and  H in order  to allow
               222       3
the use of the    Rn and  He methods.
     While these studies give broadly concordant results, many questions  remain
unanswered.  The wind velocity dependence of gas exchange rate has yet  to be
established in field studies.  The dependence of gas exchange rate on molecular
diffusivity also remains in limbo.  Finally, the degree of enhancement of
C02 exchange through chemical reactions has been only partially explored.

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                                                                    W.  Broecker
                                                                                2

     These remaining uncertainties have relevance to some of the key appli-

cations of our knowledge regarding gas exchange rates to environmental

problems.  For example, as our knowledge of the gain or loss of CC^ from

lake surfaces depends on He or Rn based gas exchange rates, the degree of

enhancement of CC>2 relative to these gases must be understood.  Another

example is the uptake of fossil fuel C02 by the sea.  Improvements of the

current 1-D models of the ocean require  a knowledge of the regional and

seasonal dependence  of  COn exchange rates.  Here the wind velocity dependence

becomes important.  These and  other examples will be discussed.

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                                                              Brurnley
           Turbulence Measurements Near the Free Surface
                   in Stirred Grid Experiments

                         Blair H.  Brumley
          School of Civil and Environmental Engineering
                        Cornell University
                      Ithaca, New York 14853

     The transfer of different gases across the surface of environ-
mental water bodies is of great ecological improtance.   For example,
the transfer of oxygen (reaeration) in rivers, lakes or reservoirs
determines their biological activity and allowable rates of waste
disposal, the volatilization and transfer of toxics (PCB's, freons)
is a critical pathway for the management of these pollutants, and
finally, several climate factors (carbon-dioxide, nitrous oxide)
are controlled by gas transfer across the ocean surface.

     It is generally recognized that interfacial gas transfer is
governed by an interaction of physico-chemical molecular phenomena
and of larger scale hydrodynamic processes, mostly the  near-surface
turbulance.  There are numerous models in the literature that attempt
to describe this interaction, however, always in a highly idealized
fashion.  These conceptual models range from film models, (liewis
and Whitman, 1924), film renewal models (Danckwerts, 1951), with
numerous schematizations of the turbulent flow structure (Dobbins,
1956; Fortescue and Pearson, 1967; Lament and Scott, 1970; Theofanus,
Houze and Brumfield, 1976), stagnation flow models (Chan and Scriven,
1970) and variable eddy diffusivity based models (King, 1966).
However, to date none of these model conceptualizations has been veri-
fied by direct detailed measurements of the near-surface turbulence
structure and the associated turbulent gas fluxes.  One reason for
this omission lies in the inadequacy of past turbulent  experimental
techniques in measuring sufficiently small scales.  Another reason
is the inherent difficulty of measuring close to a deformable and
fluctuating gas-liquid interface.

     Experiments have been conducted in a 50cm X 50cm X 40cm deep
mixing tank that is stirred by an oscillating grid (13mm bars at
64mm canters; 36% solidity).  A special cable control led-system was
developed to isolate the tank from any vibrations caused by the grid
motion and, thus, minimizing water surface ripples.  Variable grid stir-
ring intensities (stroke amplitude from 13mm to 152mm;  stroke frequency
from .5 Hz to 4 Hz and variable grid covers (distance between stroke top
and surface from 4cm to 20cm) were investigated.  Turbulence measure-
ments are made with a hot-film probe in a split-film arrangement that

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                                                               Brumley
                                                               Page 2
is mounted on a rotating  arm.  This  allows  measurement  of  one  horizon-
tal  and the vertical turbulence  components.   The  probe  speed  is  ad-
justed so as to meet the  Taylor  frozen-turbulence condition.   The probe
dimension (0.2mm)  and sampling rate  are  sufficient  to measure  close  to
the Kolmogorov length scale  for  the  given  turbulence  conditions.   The
concurrent gas transfer  (using oxygen  by starting with  an  initially
deaerated water sample)  is determined  by periodic bulk  oxygen  measure-
ments using an electronic sensor  or  the  Winkler titration  method.

     Results of the turbulence measurements  reveal  the  vertical  distri-
bution of several  turbulence properties  for  the finite  space  between
the^grid and the free surface.   In the bulk,  the  outer  vertical  and
horizontal velocity scales decay as  1/z, where  z  is the distance from
the virtual origin near  the  center of  the  grid  stroke.   This  agrees
well with the formula of  Hopfinger and Toly (1976)  (see Fig.  1).
Anisotropy is nearly constant with depth in  this  region, the  vertical
velocity scale about 30  percent  greater  than  the  horizontal  scale.
However, the velocity scales deviate from  the bulk  relationship  in  a
boundary layer comprising  a  depth of about  two  integral  length scales
below the surface.  Within this  region,  the  intensity of vertical
velocity fluctuations decays rapidly toward  the surface at all length
scales as shown by the  power spectra in  Fig.  2.   The  Kolmogorov  -5/3
power law holds  for scales smaller than  twice the distance from  the
surface.  The horizontal  velocity scales in  this  region, however, are
nearly constant  at all  scales sufficiently below  the  outer scale (Fig.
1), which increases toward the surface.   The  integral  length  scale  is
proportional to  z  in the  bulk, agreeing  with  the  results of  Thompson
and Turner (1975).  The  vertical  distributions  of dissipation  rate  and
Kolmogorov length  scale  can  also be  inferred  from the turbulence
measurements.  The results were  further  analysed  in two major  respects:
 1) Derived properties  (e.g. eddy diffusivities)  are  compared  to
theoretical values and  earlier data  (Dickinson  and  Long,  1978; Thompson
and Turner, 1975;  Hopfinger  and  Toly,  1975)  from  deep  stirred  grid
experiments in which the  surface constraint  did not exist.  2) Certain
dominant flow structures  near the surface  can be  inferred  from the
data.  These inferred structures can be  compared  to the assumed
schematizations  of the  different models  discussed further  above.   This
model validation  (or rejection)  is further  aided  by direct sensitivity
analysis of the  observed  gas transfer  rates  as  a  function  of  different
model parameters.

     Research supported  by U. S.  National  Science Foundation,  Grant
No. CEE-8004621.

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                                                 Caulliez & Ramamonjiarisoa
                       INTERFACTAL MOTIONS OBSERVED  DURING EXPERIMENTS

                                   ON AIR-WATER  GAS TRANSFER
                                             by

                               G.  CAULLIEZ  and  A.  RAMAMONJIARISOA
                       Institut de Mecanique  Statistique de la Turbulence
                       12,  Avenue  General Leclerc  - 13OO3 MARSEILLE.

                                           --—oo	
           A. number of recent observations have  shown that the rate of gas
transfer accross an air-water interface may be- significantly affected by the
interface motions.  A better determination of these motions is then needed to
understand the detailed mechanism of the gas exchange.

           This work first reports on experimental results about the water
surface wave statistical properties, especially for waves in the capillarity
gravity range. Then, preliminary results on the  motion of the underlying water
flow are reported.  These results were obtained during experiments in the
I.M.S.T. wind-water tanks, by using a number of quite sophisticated devices
such as precise capacitance wave gauges, a laser wave slope-meter and a laser
Doppler velocimeter.

           Various observational conditions were considered. Three types of
wave fields were then found to be typical :
           a/ random capillarity gravity waves in absence of gravity wave ;

           b/ random capillarity gravity waves over random dominant gravity
              waves ;

           c/ random capillarity gravity waves and gravity waves superposed to
              a deterministic  long gravity wave generated by a wavemaker-

           It was found that depending upon the conditions, the statistical
properties of the wave fields may largely differ from each other. In particular,
the space-time structure and the dispersion relation of the capillarity-gravity
wave field are strongly influenced by the presence of the random dominant
gravity wave and the swell. This suggests the existence of strong interactions
among the various fields. On the other hand, the results often depart quite
largely from the prediction of the classical potential theory for water waves.
Their analysis would in fact take into account the presence of a strong shear
layer in the top millimeter of the water flow. This suggests that the waves
are generated by an instability mechanism involving the coupled air and water
shear layers adjacent to the interface. They would then contribute more
efficiently to the mass transport accross the interface in a way which is shortly
discussed.

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                                             Chrostowski & Pearsall


 APPLICATIONS OF MOLECULAR DYNAMICS TO VOLATILIZATION STUDIES

 Paul c.  Chrostowski                  Environmental Chemistry- Program
                                      Vassar College Box 464
 Lorraine J.  Pearsall                 Poughkeepsie, NY     12601

      The primary purpose of the present research is to  develop a
 firm basis of physical chemistry toward the understanding of the
 interphase movement of pollutants both in the context of the natural
 environment  and in the unit operation of water treatment by diffused
 aeration.
      In  considering the movement of an anthropogenic pollutant between
 the  aqueous  and atmospheric phases,  recourse has been made to a treat-
 ment in  which the pollutant is taken to be a gas and various models  of
 gaseous  diffusion are applied (eg Mackay & Yuen,  1981;  Chiou et.al.,
 1980; Smith,et.al.,  1980).   Previous work by one of the authors (Chros-
 towski, et.al ., 1982)  in the study of mass transfer in the removal of
 pollutants from water by diffused aeration has indicated that the
 gaseous  models  may be divided into three general components  from
 a physicochemical standpoint: thermodynamic/equilibrium,  kinetic mass
 transfer,  and system controlled mass transfer.   In the  current research,
 concepts from physical chemistry such as scaled particle theory and
 the  solubility  parameter are applied to a better understanding of
 the  three  physicochemical components of volatilization.   Topics
 considered include structure-activity relationships to  solubility and
 volatility,  mass  transfer dynamics,  matrix effects such as salting in/
 out  and  surface action,  and the role of temperature.
     For   example,  the literature has indicated an ambiguous role for
 temperature  in  the volatilization process (Mackay & Leinonen,1975;
 Kavanaugh  &  Trussell,1980)  with different investigators varying as
 to whether temperature is directly or inversely related to the rate
 constant for  volatilization.   Experimentally,  it was  determined that
the  relationship  was  one of direct proportionality in a dynamic
diffused aeration system.   The etiology of this was investigated math-
ematically via  a  flow scheme  similar to that in Figure  1.   It  was
determined that temperature contributed to volatilization  primarily
through  the kinetic mass  transfer parameter rather than through a

-------
                                             Chrostowski & Pearsall
                                                       Page 2
shift in equilibrium or an effect on  the  system.   This type of infor-

mation will aid future investigators   in  understanding which properties

of a pollutant-water system, whether  chemical  or  hydraulic, will

ultimately determine the outcome of a volatilization situation.
                            Volatilization
temp
direct
  Equilibrium

   Henry's Law


vapor       solubility
pressure      /   I  \
       Mass Transfer

temp '
direct
           kinetic
                                                                 system
                                                                   viscosity.
                                                                   density
                                                                   surface
                                                                   tension
Figure 1—
Scheme for Analyzing Volatilization Components
( A G = free energy, A H = enthalpy, 
-------
      A LABORATORY TECHNIQUE FOR INVESTIGATING THE  RELATIONSHIP BETWEEN GAS
                        TRANSFER AND FLUID TURBULENCE


                 T. Dickey, B.  Hartman,  D. Hammond,  E.  Hurst
                      University of Southern California
      A technique has been developed to simultaneously measure fluid  turbulence


 and the exchange rate of gases across the air-water interface of a tank  under


 controlled laboratory conditions.   Turbulence is generated  with  a vertically


 oscillating grid whose stroke length, frequency, and distance from the


 interface may be varied.  Instantaneous fluid velocity vectors are determined


 using a streak photography method.   Tracks of neutrally buoyant  particles are


 recorded photographically, digitized, and the displacement  is determined.


 Exposure times are  controlled by a  light chopping wheel  and measured with a


 photo-diode and timer system.  Ensemble average  turbulent velocities and


 turbulent integral  length scales are then computed as  functions  of distance

 from  the grid.


      The gas  transfer rates  of five  gases (0  , N ,  CH  ,  CO  ,  and  Rn) are
                                            2242

 measured concurrently with the turbulence measurements  described  above.


 Before  each  run,  tank  water  concentrations  of 0   and N   are reduced to about
                                               2      2

 50% of  saturation by stripping the tank  water using  helium.   Concentrations of


 CO ,  CH  ,  and  Rn  are  elevated above  saturation by bubbling  CO and CH  through
  24                                                     24

 the water  and  by  adding  water with high  Rn  activity.   The water  is stirred to


 insure  homogeneous conditions  before  initiation  of the  experiment.  Small


 samples  of water are  taken at various  time  intervals to  determine the rate of


change in  gas concentrations.   The mass  transfer coefficient  for each gas is


computed from this data, assuming the  rate  of exchange is proportional  to the


deviation from atmospheric equilibrium.   Experiments have been conducted


utilizing three different  locations of the  grid  and two  oscillation


frequencies.  The turbulent velocity decreased nearly exponentially with


distance from the grid while the turbulent  integral length  scale increased

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                                                              Dickey et al.
                                                                Page 2
linearly with distance from the grid.  The mass transfer coefficients appear
to be proportional  to the square root of the molecular diffusivities and to
the square root of the ratio of the turbulent velocity to the turbulent
integral  length scale.  This is in accordance with the surface renewal concept
of gas exchange.

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                                                   Duran and Hemond









Duran,A.P.*, and H.F. Hemond.**




Dichlorodifluoromethane (Freon-12)  as a  Tracer  for  Nitrous Oxide  Release  from




a Polluted River








    A Freon-12  tracer  technique  has been  developed  to  measure  gas  exchange




coefficients for  nitrous  oxide  in  a  reach  of  the  Assabet  River  receiving




the effluent  of  the  Westborough,Mass.  sewage  treatment  plant.  Stirred-tank




experiments were  performed  to measure  the  relative  exchange  coefficients of




nitrous oxide  and Freon-12.   Nitrous oxide is  produced during  chlorination of




sewage and  by  microbial  metabolism and  is  highly  oversaturated  in  rivers




receiving treated  sewage  effluents.  Release  of  N20  to  the   atmosphere   can




contribute to significant  destruction of stratospheric  ozone and to "greenhouse"




warming. Magnitudes of the nitrous oxide  exchange  coefficient have been determined




with greater  precision than is  possible through  use  of  predictive  equations.




Preliminary results  also   suggest a  strong  wind effect  not  accounted   for by




predictions based on depth and velocity.  The Freon-12  tracer  technique facilitates




the determination of  the  respective  biogeochemical  roles of  sediment  and water




column with respect  to ^0  production.   The  required  sampling for  this  tracer




technique is logistically simple  and  the sample analysis is rapid.








     *  Division of Applied  Science,  Harvard University




     ** Department  of  Civil  Engineering,  Massachusetts Institute  of  Technology

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                                               Fabre et a1.
                           TURBULENCE STRUCTURE
                   OF WAVY STRATIFIED  AIR-WATER FLOW
         FABRE J. , MARODON D. , MASBERNAT L. , SUZANNE C.  (*)
             This work deals with experimental studies of near hrozontal
stratified gas-liquid flows. Experimental results on the local turbulent
structure presented here concern two phase flow modelization in pipes
and the prediction of interfacial exchanges in environmental air-water
flows.
             Indeed, two sorts of flow conditions were studied: one flow
is an internal fully developpedstratified flow where the turbulence is
controlled by fluid-wall and fluid-fluid interactions; the second is a
developping stratified flow where interfacial interactions have the main
role in turbulence production. These flows are realized in rectangular
channels with the following dimensions:
   -internal flow in a channel 12 m. long, O.lm.deep, 0.2m.large
   -developping flow in a channel 18m.long,0.6 m.large, 1. m. deep,
where the mean water depth is near 0.2 m.
             The kinematic analysis concerns the monophasic regions of
the flow and the interfacial two phase region.
             In the monophasic regions, longitudinal and vertical mean
velocity components, turbulence intensities and Reynolds shear stress
were measured ,by laser doppler anemometry in gas phase. In the two
phase region, a new measurement method, using LDA, was perfected to
obtain  1st and 2nd moments of the longitudinal velocity in liquid.
Capacitive probes were used to obtain  instantaneous  interfacial height
(*)  Institut de Mecanique des Fluides / 2,rue Camichel / 31 IOULDDSE

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                                                           Fabre et al.
                                                           Page 2

from which liquid time fraction and statistical wave characteristics were
determined.
             Main features of air and water flow are displayed by the
examination of dimensionless 1st and 2nd moments profiles. In the mono-
phasic regions near the walls and in the gas phase near the interface
the classical shear flow behaviour is shown off. On the other hand, the
liquid region under the waves exhibits particular features: turbulence
intensities and shear stress profiles are showing the important role
of turbulence transport from the wavy region; a consequence of this fact
is the failing of Boussinesq concept for shear stress in this region,
and the existence of secondary flow (which could be measured in internal
flow).
             A very crude scaling of Reynolds tensor component equations
allows to confirm the main role of transport under the wavy region and
suggests a. functional formulation for shear stress, linked with the
turbulent fluxes issued from the waves.
                    REFERENCES  for ABSTRACT
 (1) FABRE  J.  ,  MASBERNAT L.  ,  SUZANNE C.
    New  results on the  structure of  stratified gas  liquid  flow.
    Two-phase flow workshop  .  August 1982. Spitzingsee Germany
 (2) AISA L.  , CAUSSADE  B.  ,  GEORGE J. , MASBERNAT L.
    Echanges de gaz dissous  en ecoulements stratifies de gaz  et  de  liquide
    Int. J.  of  Heat and Mass transfer. Vol 24. N 6.  1981
 (3) GAYRAL B. ,  MASBERNAT L. ,  SUZANNE C.
    Mean velocities and Reynolds stresses in co-current gas-liquid
    stratified  channel  flow.
    Two-phase Momentum  Heat  and Mass Transfer in Chemical  Process and
    Energy Engineering  Systems. Vol  2. Edited by F.  DURST,  G.V.  TSIKLAURI
    and  N.H. AFGAN Hemisphere  Publishing Corporation.

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                                                Fain and Vigander
                    EFFECTS OF DIFFUSER SPACING AND
                 SUBMERGENCE DEPTH ON OXYGEN TRANSFER
                EFFICIENCY USING THE SMALL OXYGEN BUBBLE
                        REOXYGENATION TECHNIQUE

                                  by
                      T. G. Fain* & S. Vigandert
Both Research Engineers, TVA Engineering Laboratory, Norris, Tennessee
* Member, ASME
t Member, ASCE;  Member IAHR

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                                                          Fain and Vigander
                                ABSTRACT

      The turbine^of dams with deep reservoirs  and  low level  intakes  may
 discharge water with unacceptably low dissolved  oxygen concentration (DO)
 during the summer and fall  months of the year.   This  is caused  by  strati-
 fication of the reservoir and the subsequent natural  depletion  of  DO in  its
 hypolimnion.   Hence reoxygenation of the turbine discharges  may be necessary
 to maintain a healthy environment for fish  and other  acquatic organisms  in
 the tail race.  One reoxygenation technique  is  to inject small bubbles of
 gaseous oxygen into the reservoir with porous  diffusers.  The diffusers  are
 located on the bottom of the reservoir,  just upstream from the  turbine intake.
 Oxygen in the bubbles rising from the diffusers  dissolves and enriches the
 water entering the turbine.
      A pilot  scale study of the injection technique was  performed  by TVA to
 demonstrate feasability of  the method and to develop  design  criteria. An oxygen
 transfer efficiency was defined as  the ratio of  mass  of  oxygen  dissolved to the
 mass  of gaseous  oxygen injection.   The study included  field  tests  to determine
 the effects on oxygen transfer efficiency of diffuser  pore size, diffuser spacing,
 diffuser submergence depth,  and oxygen flux.  This paper presents  results of the
 field  tests.
      The test procedure consisted of  collecting  samples  of the  bubble plume
 gas at  the  water  surface and  analyzing them for  oxygen content.  Bubbles
 leaving  the diffusers  contained pure  oxygen, but when they reached the water
 surface,  they  contained both  oxygen and other gasses picked  up  from the
water--mostly  nitrogen.   The  fraction  of oxygen  not dissolved was  used as an
 indicator of oxygen  transfer  efficiency because  an accurate  oxygen balance
could not be obtained  in  the  field tests.  The oxygen fraction  in  the escaping

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                                   2                     Fain and Vigander

bubbles was correlated with the oxygen transfer efficiency on the basis of
laboratory test data for which a complete oxygen balance was possible.
     In these tests, diffuser pore sizes ranged from 1.2 to 20 microns.  The
diffuser spacing ranged from a single, isolated diffuser (hollow cylinder,
18 inches long by 3 inches OD) to a battery of 136 of the same, mounted about
5 inches apart.  Submergence depths ranged to 43 feet.   Oxygen fluxes ranges
to 0.8 acfm/ft2.
     Test results indicated that transfer efficiency decreased with increasing
pore size, increased with increasing spacing, and decreased with increasing
oxygen flux.   The transfer efficiency increased with increasing submergence
depth, but became independent of submergance depth at a point which depended
on oxygen flux and diffuser spacing.

-------
                                                              Faller
                         ABSTRACT
    International Symposium on Gas  Transfer at Water Surfaces
          Cornell University,  Ithaca , N.Y.,  13-15 June 1983

      Laboratory experiments  with small-amplitude O(0.1 cm)
monochromatic plane waves on water (wave  length  O(20 cm))
and weak shear ,  O(0.5 s  ), clearly demonstrate the generation
of convective longitudinal vortices as predicted by  the Craik-
Leibovich  (Craik,  1977;  Leibovich and Paolucci, 1981) mechanism for
the generation of Langmuir circulations.   The  shear may be produced
by wind,  a forced surface film motion,  or wave-driven shear as
predicted by Craik (1982).
      The  initial occurrence of longitudinal rolls   is  rapidly  followed
by deepening of the  shear layer,  the generation of larger-scale
rolls, and transition to  turbulence.   The experiments and theory  taken
together  show that  with almost any observable surface waves
there will be mechanically  generated convective overturning  with
longitudinal .rolls (the Langmuir circulations) and turbulence.   Gas
transfer will then be limited only by the thinnest  layer  at the surface
in which  diffusion may be pres; roed to dominate.   But even  there
the Langmuir  circulations will be important through their  tendency
to concentrate   surface  films  into lines  parallel to the shear ,
thus presenting  a significantly non-uniform surface layer .
                                  Alan  J.  Faller
                                  Research  Professor
                                  Institute  for  Physical Science  and
                                       Technology
                                  University of Maryland, College Park
                                  College  Park  ,  Maryland,  20742

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                                               Giorgetti and  Giansanti
               EVALUATION OP TURBULENCE LEVEL IN FLOWING WATEH
                       NEAR THE AIR-WA-JSR INTERFACE
   Marcitis P. Giorgetti, Professor of Hydraulics & Sanitary Engineering
   Antonio E. Giansanti, Graduate Student
               A general research program is being carried with the objective
of developing materials and methods for the inexpressive gross evaluation  of
turbulence intensity near air-water interface in flowing waters.
               It is thought that with one such additional parameter formulas
for the prediction of reaeration coefficients could be significantly improved.
The method is based on the dependence of the solubility of a solid immersed
in a liquid upon the level of turbulence of the liquid. A number of floating
probes of known weight dumped in a stream of water could be (partially)
recaptured downstream, dryed and weighted, thus giving a gross information on
the average rate of dissolution of the solid in water.
               A report is presented of a series of tests carried out  with
floating probes of salts and sugar compunds in a tank of water subjected to
convective turbulence. Turbulence is induced tj submerged jets; the geometry
of the apparatus and the flow were ;^sdG such that near the surface the
observed pattern duplicated that which is visualy observed in flovrinc streams
c.r -.T.tc.r. Probes made out of sugar compounds revealed sood sensibility to
changes of -turbulence levels. Turther tests will be conducted in a lone-
channel with bottom shear generated turbulence.

-------
                                                     Gulliver  and Stefan
                             ABSTRACT for
                      International Symposium on
                    Gas Transfer at Water Surfaces
               PREDICTION OF NON-REACTIVE WATER SURFACE
                   GAS EXCHANGE IN STREAMS AND LAKES
                by John S. Gulliver and Heinz G. Stefan
                   Assistant Professor and Professor and Associate Director,
                     respectively
                   St. Anthony Falls Hydraulic Laboratory
                   Department of Civil and Mineral Engineering
                   University of Minnesota
      A model is formulated for the water surface exchange of a non-reactive
 or  weakly reacting gas such as oxygen in streams and lakes.   The  model  in-
 corporates a molecular layer at the water surface, -vertical  turbulent
 diffusion due to bottom shear and  wind shear,  and the enhancement of surface
 exchange  by wind waves.
     The mathematical model gives an equation for the gas exchange coefficient,
     /s) which includes molecular transport in th
lent transport below.  The predictive equation is
K   (m/s) which  includes  molecular  transport  in  the  surface  layer and  turbu-
 5
                     Ks=
                           I m
where    6 = thickness of molecular surface  layer,
        D  = molecular diffusivity of dissolved gas  in water,
         m
         K = Von Karman's constant,
       U * = sum of bottom and water surface shear,
        c
        Pe = shear Peclet number = U * h/D ,
                                    c     m
and      h = water depth.
K /h = K_ is- the more commonly used "reaeration coefficient."
 S      ™

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                                                    Gulliver and Stefan
      A comparison of the predictive equation with flume observations reported
 in the literature indicates that the molecular surface layer does exist, con-
 trols surface  exchange in most cases, and may be described by the equation
                              6  = A.  v/U*                             (2)
 where  v  =  kinematic viscosity of water,
       D*  =  bottom shear velocity in flume,  and
       A.  -  a constant, -  10.
      Wind-wave flume  measurements of  K    available in the literature are
                                       s
 used  to expand Eq.  2  to incorporate wind shear  and the effect of wind waves.
 The surface  layer  thickness  is  then described by the equation

                                                     -1/2
                                                                      (3)
where    U * = wind shear velocity
          &
           $ = energy spectrum of wind waves,
           f = wave frequency,
          A_ = a constant - 14, and
                                    -8-1
          A  = a constant = 2.3 x 10   sec

The three terms in Eq. 3 represent the contributions of bottom shear, wind
shear, and the circulation under wind waves, respectively.  Under high winds,
i.e. 12 m/sec, the wave spectrum term in Eq. 3 will contribute only about
5 percent to  K .  If wind velocity is less than about 6 m/sec, however, the
               S
wave spectrum term can assume an importance equal to that of the wind shear
term in computing  K .  Separate consideration of wind effects on the surface
molecular layer and on waves in addition to bed induced shear improves the
predictive capabilities beyond available theories.
     The superposition form given in Eq.  3 is chosen because the theory is
adding the impact of various sources of turbulence, and turbulence character-
istics sum with the square of shear  velocity or velocity components.

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                                                         Hartman  et  a I.
       PREDICTION OF GAS EXCHANGE RATES  IN WIND-DOMINATED NATURAL  SYSTEMS

                    By B. Hartman,  D. Hammond, T. Dickey
                     University of  Southern California
      The results from laboratory and field investigations on the processes

 controlling gas exchange across the air-water interface are presented • and used

 to develop a predictive relationship for gas exchange rates in wind-dominated

 natural systems.  Recent laboratory measurements of the exchange rates of

 several gases and of parameters characteristic of the fluid turbulence suggest

 that gas transport can be adequately described by a surface renewal model

 based on fluid turbulent velocities and length scales.

      In the field, the rate of gas exchange in south San Francisco Bay is

 primarily controlled by wind speed.  However, application of published models,

 which characterize fluid turbulence based on the wind friction velocity and


 water depth,  predicts gas exchange rates which are 2-3 times lower than

 observed rates.   Furthermore,  they do not predict the observed functional

 dependence of gas exchange on  wind speed.

      The discrepancy between the success of the turbulence approach in the

 laboratory and its failure in  the field is probably due to the absence of

 adequate means to measure or predict from wind speed the necessary parameters



 of fluid turbulence.  Attempts to use salt dissolution rates as a technique

 to characterize fluid turbulence have proved unsuccessful to date.

      Compilation of our field  data with previous measurements of exchange

 rates in wind-dominated systems  suggests that average exchange rates can be

predicted to within 20* based on wind speed alone.   Until measurements of the


necessary turbulence parameters  can  be  accomplished these empirical

relationships based upon wind speed  must suffice.

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                                                    Holley and Yotsukura
                                                    (Invited Keynote Paper)
                                    ABSTRACT
               Field Experimental Techniques for Reaeration Studies
                   by  Edward R. Holley and Nobuhiro Yotsukura*5*"


      This  paper  is concerned primarily with gas exchange measurements in rivers
 with  secondary attention given  to estuaries, lakes, and reservoirs.  Also, the
 focus  is on  reaeration problems, with attention being given first to traditional
 DO  measurements  and then to tracer gas measurements.

      One of  the  first  approaches was based on the mass balance of oxygen with
 surface  reaeration being evaluated as the residual after measuring  DO distri-
 butions  and  then accounting for other sources and sinks of DO.  The accuracy
 of  reaeration  determination with this method is limited by the accuracy of eva-
 luation  of the other sources and sinks, some of which are unsteady and therefore
 prevent  testing  during steady-state periods.  A disturbed equilibrium method has
 also  been  used with DO measurements being taken first under natural conditions
 and then with  a  steady-state injection of catalized sodium sulfite, which lowers
 the DO concentration.  The change in DO concentration between the two conditions
 is  used  to determine the reaeration, assuming that all sources and sinks except
 the surface  transfer are unaffected by the sodium sulfite.  The method has been
 used  only  for  small streams where the sodium sulfite became mixed relatively
 quickly  across the full stream  width.

      Most  studies have assumed  that DO concentrations are uniform across the
 width  of a river and have used  ID representations.  The data of Churchill et al.
 shows  that the deficit may vary as much as 15% across the width under natural
 conditions (no BOD loads).  The importance of natural transverse variations in
 a given  river  can be estimated  using Holley's result that the amount of variation
 of  deficit across the width is  related to the ratio of a characteristic transverse
 mixing time  to a characteristic reaeration time.

      There have  been relatively few reaeration measurements in wide estuaries,
 lakes, and reservoirs where the flow pattern is highly two-dimensional and/or where
 a significant  part of  the reaeration is associated with wind induced turbulence.
 One method that has been used is a floating dome with surface gas transfer being
 determined by  the change of pressure in the gas trapped between the dome and the
 water  surface.   Problems with this method include heating of the dome by inci-
 dent  radiation, keeping the gas space under the dome sealed from the atmosphere
 when  surface waves are present, and possibly disturbing the natural turbulence
 structure  at the surface where  the gas transfer is taking place.

      Tracer  gas techniques were developed in an effort to measure gas transfer
 without  interferences from the  various natural sources and sinks of DO in rivers.
 In  Tsivoglu's method, a bottle  containing dissolved radioactive krypton, tritium,
 and Rhodamine WT is broken below the water surface.  Using the Rhodamine as a
 location tracer, the difference in measured concentrations of krypton and
 tritium, a conservative tracer, can be related to the surface desorption
 of  krypton.  In the USGS method, hydrocarbon gases are bubbled through the
 depth  of the river and Rhodamine WT is used as a conservative tracer.  The
 injection time may be short (15-30 minutes) to give a moving cloud of tracer
 gas.   The method is then similar to the krypton method.  In another technique,
 *  University of Texas,  Austin,  TX
**  U.S.  Geological  Survey,  Reston, VA

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                                        -2-          Holley and Yotsukura
the hydrocarbon tracer gas is injected long enough to give steady-state concen-
trations.  In small streams with complete transverse mixing, the difference in
tracer gas concentrations between cross sections can be related to the surface
exchange.

     The krypton method suffers from public concern about the introduction of
radioactive materials into the environment.  The hydrocarbon-gas methods
suffer from the inconvenience of setting up the bubbling apparatus in the river
and from needing to correct for loss of Rhodamine WT dye.  Both the krypton
and the hydrocarbon gas methods have been used primarily in small  streams where
transverse mixing could be achieved in the study reach.  Investigations are
currently underway on using the steady-state hydrocarbon gas method with an
unmixed plume in larger rivers.  The tracer gas methods appear to hold much promise
for future measurements.

     (For each of the methods, the practical aspects of actually executing the
tests under field conditions will be addressed.)

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                                                Hovis et al
                       ABSTRACT

        GAS TRANSFER RATE COEFFICIENT MEASUREMENT
          BY A STABLE ISOTOPE KRYPTON TECHNIQUE
               I.  TREATMENT PLANT STUDIES
               J.S. Hovis , J.J. McKeown ,
                          2                 't
             D. Krause,Jr. , and B.B. Benson"
1)   National Council of the Paper Industry for Air and Stream
    Improvement, Inc., Northeast Regional Center, Tufts
    University,  Medford, Massachusetts  02155
2)   Department of Physics, Amherst College, Amherst,
    Massachusetts 01002

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                                                       Hovis et al.

                                                       Page 2
     A new pair  of  tracers for gas  transfer measurement  have



been developed for  use in turbulent,  open  systems.   Stable



isotope krypton  (Kr),  with atmospheric  composition,  and  lithium

                                           g c        O

(Li) salts replace  the radioactive  tracers  Kr  and  H,  respectively,



as the gas and dispersion tracers in  the direct  tracer method



developed  by Tsivoglou,  et.  a_l (1965, 1967, 1968) .   The  primary



application of this technique  has been  in  the precise determination



of oxygen  transfer  rate coefficients  (a kTa ) in respiring wastewater
                                         LI


treatment  systems and  natural  water bodies.



     A complete  system of dosing, sampling and analysis  has



been developed to make this  new, non-radioactive tracer  method



a viable field testing procedure.   The  field equipment and techniques,



and the calculations,  will be  discussed in this  paper.   The



analytical methods  will be described  in Paper II.



     It is proposed that this  new pair  of  tracers can be used



under operating  conditions in  a wastewater treatment plant employing



any common form  of  oxygen transfer  equipment: coarse or  fine



bubble diffused  air, turbine or mechanical surface aeration.



Further, with the addition of  a fluorescent dye  to track the



tracer cloud, the method may be applied to large, surface water



bodies:  rivers, lakes and impoundments.   The technique  is also



applicable to the measurement  of transfer  rate coefficients



for other gases, once  appropriate relative transfer  rates have



been established.



     Two field tests of  the  stable  krypton/lithium tracer method



have been completed to date.   These tests  have measured:  the

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                                                        Hovis  et al.

                                                        Page 3



aKTa of  (1) a coarse bubble, diffused air  system  in  an  operating,
  L


municipal activated sludge plant and  (2) a fine bubble,  dome



diffused air system in a manufacturer's, clean water, testing



tank.  A third test is scheduled in an operating, municipal/paper



indusry, activated sludge plant, with mechanical  surface aeration.



     The precision of the rate coefficient measurements  has



been determined.  The precision of the Kr  measurement by isotope



dillution mass spectrometry  (+/- 0.05%, s.d.) and the precision



of the Li measurements by flame atomic absorption spectrophotometry



(+/- 3%, s.d.) are discussed in Paper II.  Based on  the  clean



water test data, where dispersion was not  a factor,  the  precision



of the krypton transfer rate coefficient (K a,.-Kr) was better
                                           Xj I


than +/- 0.5%, s.d.  The overall precision of the  aKTa.,-Kr
                                                     Li I


measurement for the wastewater treatment plant was better than



+/- 3%, s.d.  In calculating the oxygen transfer rate coefficient



(aK-a,) from these data, the precision proved to be  limited



by the precision (+/- 5%, s.d.) of the literature value  for



the krypton to oxygen transfer rate ratio  (0.83 +/-  0.04,  s.d.;



Tsivoglou,  1967).   Refinement of this ratio is required  to improve



the precision of the direct tracer measurement for oxygen.

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                                                                  Hsu et al.



                       BUBBLES PRODUCED BY BREAKING WAVES

                                       by

                   Y.-H. L. Hsu, Paul Anche Hwang, and Jin Wu

                College of Marine Studies, University of Delaware
                             Newark, Delaware 19711



                                    ABSTRACT

     Bubbles produced by breaking waves are involved in many processes at the

air-water interface.  In particular, bubbles are suggested to play an important

role in gas transfer across the interface, and in producing spray droplets.

However, this sequence of events — wave breaking, air entrainment,  and

droplet production — has not been systematically studied.  In the present

study, simultaneous measurements of breaking waves, bubbles, and spray at

different wind velocities were conducted.

     The size and velocity of bubbles and spray were measured with optical

sensors.  Their size spectra are found to be closely related.  This provides

further evidence of the bubble bursting production mechanism.

     Bubble population is found to increase drastically with wind stress; the

critical stress for bubble inception is also deduced.  A simple model including

mechanism of entrainment is proposed to predict the bubble distribution as a

function of depth.

     Time series of bubble flux shows intermittent property.  The intermittency

is closely related to the frequency of wave breaking; the latter in turn is

related to wind stress and wave groupiness.  Statistical and spectral analysis

on the bubble fluxes and waves are performed.  Cross spectral analysis shows

higher coherence between wave and bubble flux at higher wind velocities  (>_ 13

m/s).  For lower wind velocities the bubble flux is intermittent due to  only

occasional wave breaking.

-------
                                                                   Hsu et al
                                                                   Page 2

     The population distribution per breaking interval (between breaking

waves) shows gradual change from relatively uniform distribution for strong

breaking to a skewed distribution for weak breaking.  The spreading of the

distribution is also wider for lower wind velocities,  indicating that wave

grouping plays a significant role in the breaking processes.

-------
                                                Hunt
                                                 (Invited Keynote Paper)
Turbulent Structure and Mixing Near Gas Liquid Interfaces

                              J.C.R. Hunt

Department of Applied Mathematics and Theoretical Physics,
University of Cambridge, Silver Street, Cambridge CB3 9EW.



Summary

1.       Turbulence structure

         In boundary-layer flows of a fluid over another fluid much

denser  (or more viscous) than itself, or over a solid surface, the

production and dissipation of turbulent energy occurs very close to

the surface where the mean velocity gradients are greatest;

turbulent energy is transported away from the surface by the

turbulence itself (.one can think of pairs of vortices inducing

such motions, or think in terms of 'bursting1 motions).   Turbulence

can also be generated by many other means, by 'thermal convection,

by bubbling motions, by mechanical agitation or wave action on the

surface, or by breaking of internal waves.  In most of these cases

the production and dissipation of turbulence is more evenly

distributed through the fluid.  The differences and similarities

between these classes of turbulent flows will be discussed.

         Now at the liquid side of a gas-liquid interface, in the

absence of breaking waves or a downward heat flux, no turbulent

energy is produced because the mean velocity gradient is smaller.

However the turbulence which is produced by the flow field (e.g.

by shear), well below the surface is distorted near the surface

because the velocity fluctuations normal to the surface are zero,

and the scale of the fluctuations decreases toward the surface.

Horizontal fluctuations within a thin viscous sublayer may be

-------
                                                    Hunt
                                                    Page 2
affected by the resistance to surface straining motions by

surface tension.  The effect of wave and surface heat flux on

the turbulence structure will also be discussed.



2.       Turbulent mixing

         Mixing in a turbulent flow between a fluid and one or more

dispersed substances firstly depends on the scale and the intensity

of the turbulence, and secondly on the mean or slowly fluctuating

velocity gradients, (e.g. caused by shear or waves).  The

mixing also must depend on the mean and fluctuating distribution

of the dispersed substances (e.g. the air dissolved in water).

The presence of a second phase (e.g. in the form of spray in air

or gas bubbles in water)  can also have significant effect on the

turbulence and mixing.  Depending on how interfaces affect the

turbulence and the mean flow,  their effects on mixing vary.

These will be discussed Cas will the first part of this talk)  in

largely qualitative terms but with some reference to mathematical

arguments and to experiments.

-------
                                              Ilmberger et al,
         Parametriration  of  air/lake  gas exchange

         J.Ilmberger, P.Liebner,  B. Jaehne,  K.H. Fischer
         Institut fur Umueltphysik, Heidelberg  University

         W. Weiss. Bundesanstalt  fur  Zivilschutz - Messstelle
         Freiburg

         D. Imboden, U. Lemnin, EAWAG,  Swiss Federal  Instituts
         of Technology, Duebendorf
 Previous  field data on air/lake gas exchange clearly show a strong

 wind  speed dependence, despite the large  scatter of data. But

 nevertheless these data are not appropriate to parametrise the

 exchange  rates, mainly due to the following reasons. Firstly, the

 sampling  periods were too long, so that the gas exchange rates

 obtained  were a mean value over various conditions. Secondly, and more

 seriously, the parameters controlling gas exchange (windspeed,

 stability, waves) were measured only imperfectly. The only parameter

 known in  some experiments was the windspeed, mostly only measured on

 stations  ashore.




 Therefore in autumn 1982 we started an investigation on Lake Sempach,

 Switzerland, in order to try a parametrization of air/lake gas

 exchange. The gas exchange rate is measured with the Tritium/He3

 method,  furthermore oxygen profiles can be measured rapidly with a

 jojosonde. In the middle of the lake a boje is anchored, measuring

automatically all important meteorological and limnological

parameters,  and additionally the waves with three different optical

wave measuring systems.

-------
                                                Ilmberger et al.
                                                Page 2
We do not believe, that it will be possible to obtain a
parametrization of air/lake gas exchange during all the time with high
time resolution (a few days). Therefore the aim of our investigation
is twice: Firstly, to measure gas exchange under extreme conditions
(long period of low wind speeds, resp. short stormy period). Secondly,
to measure continuosly, all important parameters controlling the gas
exchange to compare them (espcially the waves) with wind tunnel
results and to test parametrizations predicted from lab results under
natural conditions.

-------
                                 Iverfeldt and Lindguist





 The  Transfer  of  Mercury at the air/water interface





            Ake  Iverfeldt and Oliver Lindgvist



 Department  of Inorganic Chemistry,  Chalmers  University  of



 Technology  and University of  Goteborg,  S-412 96  Goteborg,



 Sweden.
 The  geochemical  cycle  of mercury  have  been of major interest



 during many years.  However,  until recently only few basic data



 governing the exchange of mercury at the air/water interface



 has  been known.






 A large portion  of  the mercury in the  atmosphere is elemental.



 The  Henry's law  constant for elemental mercury  (Sanemasa, 1975)



 was  used by Fogg and Fitzgerald  (1979) to conclude that the



 rainwater concentration of mercury must consist of other species



 than Hg .






 In the last few  years, we have performed a series of determina-



 tions of the Henry's law constants for different Hg   species:
Compound
CH3HgCl
CH3HgCl
CH3HgCl
HgCl2
Hgci2
Hg(OH)2

Hg(OH)2
(Hg°
H =
: [HgX(g)] /[HgX(aq)] Temp
1.9-0.2-10"5
1 .6-0.2-10"5
0.9-
2.9-
1 .2-
3.2-

1.6-
0.3
TO'5
10'8
io-8
TO"6
-6
10

25°C
15
10
25
10
25

10
20
[Cl ]
0.7
1 .0
0.2-
0.2-
0.2-
0.2-

0.2-
0

M

ID'3
TO'3
TO'3
TO'3
-5
10'3

Ref
1
1
1
2
2
2

2
3 )
1.  Iverfeldt and Lindqvist (1982);  2.  Iverfeldt and Lindqvist  (1980)

-------
                                                              2.
                                 Iverfeldt and Lindquist
The table show that listed mercury  compounds  are  effectively


scavenged from air by rain. From  these  constants  and other


considerations, Brosset  (1981) proposed a  mercury cycle where


Hg° is emitted from ocean water to  the  atmosphere.  He further


proposed that the elementary mercury  is subjected to atmospheric

                                                        2 +
oxidation processes and transformed to  water  soluble Hg


species.



In a preliminary investigation, we  have shown that  Hg  may be


oxidized by ozone. (To be published). The  laboratory studies


show  that the ozone induced  oxidation is slow in  air, but


that the rate is increased by several orders  of magnitude having


a water phase present, cf „ cloud  and raindrops in the atmosphere,.



To get a more complete picture of the mercury cycle we have


also performed in situ experiments  using benthic  chambers to


investigate sediment/water exchanges in an unpolluted coastal


water (Iverfeldt et al.,to be published).   A  rather large part


of the total mercury in water above the sediment  was found to


be volatile, probably Hg°.  The pore water contained relatively


less volatile mercury.  We do not know,  if the volatile Hg  is


produced only in the sediment or/and at the sediment/water


interface by a change in redoxpotential or by -bacterial


degradation (cf.  Spangler et al,  1973).



The sediment/water interface could  be compared to the interface


between oxic surface water and anoxic subsurface  water in a


permanent anoxic fiord (Framvaren, Norway). A very  active


bacterial layer is found in the redox boundary (Skei,  1981).

-------
                                  Iverfeldt and Lindquist    3.







 Extremely high amounts of volatile mercury was also found  just




 above this boundary.  (To be published).






 Knowing that the ocean is covered with a surface layer with




 high bacterial activity, a hypothesis may be stated, that




 Hg  emitted from the ocean to the atmosphere is partly




 produced in the surface microlayer.








                   REFERENCES





Brosset C.(1981) Water, Air and Soil Pollut. 16, 253-255.





Fogg T.R. and Fitzgerald W.F.(1979) J. Geophys. Res. §4, 6987-6989





Iverfeldt A. and Lindqvist O.(1982) Atm.Environ. 1§ (in print).





Iverfeldt A. and Lindqvist O.(1980) The Coal, Health,  Environment




 Project, Report no 41 5 ( in Swedish with a summary in English),



 The Swedish State Power Board, S-162 87  Vallingby, Sweden.





Iverfeldt A.,Hall P-,Rutgers van der Loeff M.,Westerlund S.,




 Sundby B. and Andersson L.( To be published )





Sanemasa I. (1975)  Bull.Chem.Soc.Jpn. 4J, 1795-1798.





Skei J.(1981)  NIVA-Report F-80400(ISBN 82-577-0447-4)  Norsk



 institutt for vannforskning,  Oslo, Norway.





Spangler W.J.,Spigarelli J.L.,Rose J.M. and Miller H.M.(1973)



 Science 180,  192-193.

-------
                                                      Jaehne
        Optical  water waves measuring techniques

        B.  Jaehne,  Institut fuer Umweltphysik
        Heidelberg  University,  Western Germany
We focused our interest on optical  wave measuring techniques
because of the importances of capillary waves for gas exchange
and knowing the difficulties to measure them with wire gauges.

Any optical method obvisiously has  the advantage not to be in contact
with the water surface and therefore not to interact with the waves.
We developed a refraction technique similary to the ones already used
by other workers. The system measures the slope of the waves. A
He-Ne-laser beam pierces the water  surface vertically from above. The
optical reciever consists of a Fresnel lens and a focusing screen, one
focal length distant, so that the displacement on the screen only
depends on the slope and not the height of the waves. Finally the spot
on the screen is imaged on a dual axis position sensitive photo diode.
The resulting electric signal is slightly nonlinear due to the optical
geometry and non linearities of the photo diode. The cutoff frequency
of the detector together with the electronics is about 100 kHz, Thus
the frequency response of the system is limited only by the diameter
of the laser beam. Tests with different diameters show, that all wave
frecencies occuring can be measured without any damping.

The fast response of the detector enables us to measure correlations
with only one wave measuring unit in the following way: The laser beam
oscillates horizontally (0.5 to 30 mm) over the water surface at the

-------
                                                            Jaehne
                                                            Page 2
sampling frequency (about 1 kHz) of the time series. Two time series,

0.5 to 30 mm distant, are put on the computer simultaneously. Phase

velocities of capillary waves are thus determined.


Finally, the possiblities of visualisation techniques based on the

same optical geometry as the spot method with the laser are discussed.

The first step done  in this direction are photographs of a 20 cm

diameter area showing the slopes of waves indicated by different

colours. With this method it will perhaps be possible to calculate two

dimensional wave number spectras.

-------
                                                  Jaehne  et  al..

        Wind/wave-tunnel experiments nn + h» Schmidtnumber-  and
        wave field dependence of air/water gas exchange


        B. Jaehne, W. Huber, J, Ilmberger, T. Wais
        Institut fur Umweltphysik, Heidelberg University
        Western Germany


Gas exchange experiments have been carried out in order  to  study  the

influence of parameters controlling gas exchange  without  breaking

waves: friction velocity u,,  Schmidtnumber Sc=v/D for the gas

studied, and the wave field.



We use 3 different wind/wave tunnels for our experiments: Two  circular

ones of different sizes and the the large wind/wave  facility of

IsM.S.T Marseille, where the experiments have been carried  out in

cooperation with L. Merlivat and L. Memery from CEN  Saclay. The

circular tunnels have the advantage of a homogenous  wave  field of

unlimited fetch in contrast to the short fetch waves in all linear

tunnels.




Different tracers are used in order to study the dependence of the

exchange rate on the Schmidtnumber: C02 and heat  in  the small

circular tunnel, C02, He,  CH«, Kr and Xe in the large circular

facility and Rn and He in the I.M.S.T. tunnel. Wave  slope spectras are

obtained with an optical refraction method using a He-Ne-Laser and a

position sensitive photodiode.




With a smooth water surface the experimental results agree  well with

theories treating the water surface as a rigid wall:  The  Sc'273

dependence and correct absolute values of the exchange rate are

obtained.  When waves occure a strong increase in the  transfer velocity

is observed as well as a change of the Schmidtnumber  dependence to

Sc"1'2.

-------
                                                 Jaehne et al.
                                                 Page 2
Both results cannot be explained with existing theories (surface increase
and periodic dilation of the viscous sublayer by waves). The increase
of the gas exchange rates through the waves is different in the 3
tunnels due to their different wave fields. Several wave parameters
are discussed in order to parameterize the influence of waves on the
exchange process. Moreover, the windtunnel results are compared with
field data.

-------
                                                            Jirka and Brutsaert
                  MEASUREMENTS OF WIND EFFECTS  ON  WATER-SIDE
                  CONTROLLED GAS EXCHANGE  IN  RIVERINE SYSTEMS
                                      by
                    Gerhard H. Jirka  and Wilfried  Brutsaert

                 School of Civil and  Environmental Engineering
                              Cornell University
                            Ithaca, New York   14853
                                   ABSTRACT

     The traditional approach toward  the analysis  of  gas  transfer at the sur-
face of streams or rivers has been limited to  consideration of turbulence gen-
erated by bottom shear in the flowing water.   The  effect  of wind has been sim-
ply neglected.  However, for wider open rivers with moderate slopes and more
tranquil flows, including inflow into lakes or reservoirs  and approaches to
estuarine conditions the wind effect must be expected to  become increasingly
important and a transition to purely wind-controlled  conditions (as considered
in oceanographic work) will take place.
     A simple criterion on the relative importance of streamflow versus wind
generated gas exchange is developed on the basis of the respective near-sur-
face turbulent energy dissipation rates e in the water.   Open channel experi-
mental data by Nakagawa et al. (1975) are used for e  under pure streamflow
conditions, while e for wind conditions is computed on the basis of similarity
in the wall layer of the wind driven  turbulent boundary layer in the water
with estimates of the roughness height from Kondo  (1975).
     Data from two riverine gas exchange experiments  with concurrent detailed
wind measurements are analysed.  Correlations  between wind shear velocities
and observed exchange velocities (KL) appear to be consistent with the dissi-
pation based criterion.  The data also demonstrate the strong micro-meteoro-
logical sheltering effect of stream banks and  vegetation  on gas exchange in
small streams.

-------
                                                                Johnson

            PREDICTION OF DISSOLVED GAS TRANSFER IN SPILLWAY
                 AND OUTLET WORKS STILLING BASIN FLOWS
                                 by
    Perry L. Johnson, Hydraulic Engineer, U.S. Bureau of Reclamation

An empirical model is presented that predicts the oxygen and nitrogen
transfer to and from the flows through hydraulic structure stilling basins.
The model may be applied to a wide variety of structures ranging from open
chute hydraulic jump basins to flip buckets and plunge pools and from hollow-
jet valve to fixed cone valve to slide gate controlled outlet works basins.
The model may be used to evaluate both the structure's reaeration potential
and the structure's potential for nitrogen supersaturation development.
The present model is a refined and expanded version of a model  first developed
by the author in the mid-70's.  The present model is better suited to handle
low Froude number stilling basins and is analytically more direct.   The
model is based on data collected at over 24 different field structures.
Parameters considered include dissolved gas concentrations in the flow enter-
ing the structure; water temperature; barometric pressure; the velocity,  cross
sectional shape, and orientation of the flow entering the stilling basin;
stilling basin length, width, depth, and shape; and tailwater depth.   Included
is an example application.

-------
                                                       Jones  and Hannan
                    A New Way to Study CO /Water Equilibria
                                         
-------
                                                            Kerman I
             DISTRIBUTION OF BUBBLES NEAR THE OCEAN SURFACE
                             Bryan R. Kerman
                    Boundary Layer Research Division
                 Atmospheric Environment Service, Canada
Extended Abstract

     Crowther has recently offered an interesting hypothesis that the
number of bubbles near the air-sea interface is only a function of the
rate of work of the atmosphere on the surface, the surface tension and
the bubble radius.  Interestly, no consideration was given to the dynam-
ical significance of g, the acceleration due to gravity, which according
to Phillip's model of an equilibrium wind-wave field, including breaking
waves and extensive bubbling, uniquely defines the wave height spectrum..

     A simple model, not explicitly derived in terms of the statistical
transport equations utilized by Garrettson and Crowther, is formulated
for the generation and 'spectral' transport of bubble mass.  A subrange
in which there is no mass convergence due to coalescence or dissolution
is considered.  From mass continuity arguments, the change of radius due
to pressure, and the hydrostatic balance, it is readily deduced that the
mass (and volume) flux per radius increment is both distributed as a neg-
ative exponential with depth and as r~3 with radial size.  However the
model of Crowther, as demonstated, is not unique but is only one of a set
of possible similarity solutions.

     Based on arguments for the radial forces on a cavity, there exists
an outer scale, for bubble production by shattering comparable to the
wavelength associated with a minimum phase speed of gravity-capillary
waves.   A revised dimensional analysis including, g, and this outer
shattering scale, leads to a result, identical to Crowther's indicating
the similarity function,  associated with Crowther's model, is a constant
in the problem variables.

-------
                                - 2 -                      Kerman I
     An analysis of various data sets for bubble densities  and  distri-
butions, or deduced properties from acoustic resonance,  establishes  that
the wind dependence, vertical  distribution,  spectral  shape  and  tenta-
tively, the influence of surfactants agree with the model's predictions.
However, for agreement in order of magnitude,  it is necessary to  consider
the relatively sparse nature of active bubble  production in breaking
waves compared to the total surface area,  as well  as  the relatively
sparse nature of large shatterable cavities  within a  whitecap.  Intuitive
arguments for these characteristics result in  agreement  within  a  factor
of 10, but are considered weak due to lack of  detailed experimentation on
the structure and life cycle of breaking waves.

-------
,S                                                                  Kerman  II
             A MODEL OF INTERFACIAL GAS TRANSFER FOR A WELL-ROUGHENED SEA
                                    Bryan R. Kerman
                           Boundary Layer Research Division
                        Atmospheric Environment Service, Canada
       Extended Abstract

            Deacon has recently proposed a model for wind-driven gas transfer
       across a sea surface if the airflow is aerodynamically smooth.  In this
       case of transitional or fully rough flow, it is well-known, at least
       from laboratory measurements, that the gas flux significantly exceeds
       that predicted from an extension of smooth wall considerations.   At the
       same time, by analogy or direct comparison with the limited extent of
       bubbling in breaking waves or peaked small waves, the flow separation
       associated with rough wall flow is hypothesized to occur over a  small
       fraction of the total area.  A key question is whether moderate  local
       turbulence near sparse regions of flow separation can transfer gas more
       efficiently than weak, but global, turbulence for smooth wall  flux.

            A model is presented for the flux of a non-reactive, low solubility,
       low diffusivity gas, like 02» through this air-sea interface in  the
       presence of patches of waves over which the flow is separating.   The
       development is based in the work of Yaglom and Kader for rough wall  trans-
       fer of heat and mass, but is applied here to a compliant rather  than
       solid surface.  In order to estimate the surface (roughness) Reynolds
       number, it is  necessary to quantify the rms height of the roughness
       elements.   An  extension of the Charnock relationship for surface roughness
       is provided which accounts for the contributions from surface root mean
       square elevation and slope for waves whose phase speed exceeds the minimum
       phase speed of gravity-capillary waves.  The areal extent of the transfer
       is modelled in a manner similar to Cardone and Wu, but is normalized in
       terms of the threshold stress for flow separation.
                                                                          • • • • • C.

-------
                                      p
                                                            Kerman  II
     Comparison of the model  with various data sets, including the .stress
dependence of Charnock's constant,  the areal  coverage of whitecaps and
the gas flux in laboratory  and  recently reported field experiments,  con-
firms the genera]  validity of  the  formulation.   However, in  all  cases
there is considerable  experimental  scatter or limited representativeness
so that it is uncertain whether the model  is  correct in detail  or  only in
its general  trends.

-------
                                                                   Khudenko

                        Stationary  and  Self-Propelled
                               Weir  Aerators

                   Boris M. Khudenko,  Associate Professor
                        Georgia Institute of Technology
                             Atlanta,  GA  30332


      Several weir  types, sharp-crested, broad-crested, tooth-shaped, and tooth-

 shaped orifice have experimentally been tested in a hydraulic flume.  Sizes of

 weirs, the flume length and depth, and the water flow rate have been varied over

 a wide range.  The maximum capacity  of the test model is 10,000 m /d.  The

 efficiency of oxygen transfer has  been related to the geometric and hydraulic

 characteristics of the  studied systems.  The efficiency of oxygen transfer by

 the use of weirs reaches 3 kg/kW-L.

     A self-propelled modification of  weir aerators has been developed.  This

 aerator consists of a weir box with  a  weir or orifice, and a propeller type

 pump located on floats.  The floating  structure is connected by means of a

 hinged arm to a central pile.  When  the pump is activated a jet of water is

 discharged through the weir or orifice.  The jet aerates and mixes the water and

 propels the floating structure around  the central pile.  Rotation o.f the floating

 structure around the pile increases  the service area of the aerator.  The major

 parameters of this aerator type,  oxygen transfer, velocity of rotation, and

 mixing capacity have been evaluated.

     Weir aerators can be used for water and wastewater treatment, aeration of

 stagnant and stratified lakes,  rivers,  etc.   The advantages of stationary weirs

 are best utilized in high rate processes such as activated sludge process,

aerobic stabilization of sludge,  postaeration, and other.  An important feature

of self-propelled aerators is their ability to mix large volumes of water.

Such aerators can be used for biological ponds, lakes, etc.

-------
                                            Kitaigorodskii  and  Donelam
                                            (Invited Keynote Paper)
                                ABSTRACT
                  The Structure of Turbulence on Both
                    Sides of the Air-Water Interface

                          S. A. Kitaigorodskii
               Department of Earth,and Planetary Sciences
                      The Johns Hopkins University
                       Baltimore,Maryland  21218

                             M. A. Donelan
                   National Water Research Institute
                    Canada Centre for Inland Waters
                          Burlington, Ontario
     In  this  paper  we  discuss   the  structure  of  turbulence   in  the
vicinity  of an  air-water interface  as  it  relates  to  gas  transfer.
Because the molecular diffusion coefficient of  gas  in  the liquid phase
is  much  lower  than the  gaseous   coefficient,  the  transfer of gases
across  the  air-water  interface is dominated  by the resistance  of  the
boundary  layer in the water.   Even for hydrodynamically rough flow this
remains true because of  the  large Prandtl number  in the water.   That
is,  the  erosion of  the  viscous   boundary  layer implied  by  rough flow
does not  necessarily mean any  significant  commensurate  thinning  of  the
diffusive boundary layer.

     However,  in the presence  of  active  wind-wave  breaking the  analogy
between transfer across  the  air-water  interface  and heat  transfer  at
solid  srufaces  is  no longer valid  and  the structure  of  the turbulent
boundary  layers  on both sides of  the  interface becomes  important.

     Therefore in the first  part  of this paper we discuss the processes
responsible for  the variability of the molecular diffusion sub-layer in
the  presence  of  shear-generated  turbulence   near  solid  roughness
elements.   In the second part of  the  paper we  turn our  attention to gas
transfer processes  when there is  active  wind-wave breaking.

     Frequent  use   is  made  of   data  from  laboratories  and  natural
air-water interfaces to  illustrate the  variability  of  the structure of
turbulence as  it pertains to  gas  transfer.

-------
                                                   Krause et al,
                        ABSTRACT

        GAS TRANSFER RATE COEFFICIENT MEASUREMENT
         BY A STABLE ISOTOPE KRYPTON TECHNIQUE.
                II.  ANALYTICAL METHODS
            D. Krause, Jr. , B.B. Benson ,
                        2              2
              J.S. Hovis  , J.J. McKeown ,
                       3                  3
            R.P. Fisher , and M.N. Stryker
1)  Department of Physics, Amherst College, Amherst,
    Massachusetts  01002
2)  National Council of the Paper Industry for Air and Stream
    Improvement, Inc., Northeast Regional Center, Tufts
    University, Medford, Massachusetts  02155
3)  National Council of the Paper Industry for Air and
    Stream Improvement, Inc., Southern Regional Center,
    P.O. Box 14483, Gainesville, Florida  32604

-------
                                                       Krause et al.


                                                       Page 2






     We have developed equipment and techniques for measuring



the transfer rate of krypton gas in large bodies of water or



wastewater treatment plant mixed liquor.  The procedure  is criti-



cally dependent on the ability to measure precisely the  small



krypton content of liquid samples, which is accomplished by



a somewhat unusual isotope dilution technique.  Because  the



test is conducted under dynamic conditions, it is equally critical



to account for gas dispersion by using a lithium salt  as '.a .conserva-



tive tracer added with the krypton.


                78
    The isotope   Kr is used as the isotope dilution spike because


78
  Kr constitutes only 0.35% of normal krypton gas,,  The  new



technique involves spiking the liquid sample with an amount


               78
of nearly pure   Kr which is approximately equal to the  amount



to total krypton in the sample, and then measuring the abundance



ratio of 78Kr to "total krypton" (8°Kr, 82Kr, 83Kr, 84Kr, 86Kr)



with a specially designed dual collector mass spectrometer.  This


                                         78
ratio, combined with the known amount of   Kr spike, yields



a very precise measure of the krypton content.



     Five to thirty STP liters of krypton dissolved in twenty



to forty liters of lithium chloride brine  (40% w/w) are  quickly



injected into the system to be studied from two equilibrators,



each with a volume of ^85 liters and operable at pressures up



to 7 atm.  Subsequent to this dump, samples of the liquid are



collected at appropriate time in -^250 cc glass bottles and sealed



with Poly-Seal caps.  Exact liquid content is determined by differ-



ential weighing. An unsealing device has been designed and construct-



ed which allows the sample bottle to be opened inside  a  thoroughly

-------
                                                       Krause et al.

                                                       Page 3





                        78
evacuated chamber.  The   Kr spike is introduced  into  the  chamber



before opening the bottle.  The liquid is degased by violent



stirring, and the evolved gases are dried in dry  ice - acetone



and liquid nitrogen traps before they are cycled  over  hot  (950C)



titanium to remove all but the noble gases.  The  gas is then



put through a process gas chromatograph using helium as carrier



gas.  The sample stream gas is directed into a mechanical  vacuum



pump except during the time that the krypton is being  eluted,



when the flow is switched to pass the gas over a  molecular sieve



trap operated at 77K, which collects the krypton. After the



helium is pumped away, the sieve is warmed and the released krypton



is collected for the mass spectrometric analysis.  Because the



spiking material is added at the time that the bottle  is opened,



total quantitative recovery is not necessary because it is only



the isotopic ratio which must be measured.



     The concervative tracer (Li)  was determined  by flame  atomic



absorption spectrophotometry (AAS).  Experimental results  have



shown than among the standard procedures for sample preparation



and AAS analysis of lithium in mixed liquor, only one  protocol



gives satisfactory results.



     The precision and accuracy of the gas and conservative



tracer measurements are discussed.

-------
                                               Kuo and  Pilotte
Estimation of Volatilization of Toxics for  Multimedia Modeling
          Jan-Tai  Kuo,  Visiting Associate Professor,  Civil
          Engineering  Dept.,  National Taiwan University, Taipei,
          Taiwan,  Republic of China and James 0.  Pilotte. General
          Software  Corporation, Landover, Maryland, U.S.A.
Abstract

     Multimedia modeling for estimating the concentration of
toxic substances considers the transport,  transformation and
reactions of chemicals in air,  water and  soil,  and the rate of
chemical exchange between any two of these three  geospheres.  The
methods used to  estimate  the changes in concentrations due to the
volatilization processes between water and  air as well as between
soil and air can be of critical  importance in a multimedia model.

     Many multimedia models utilize  simplified  approaches  (e.g.
fugacity,  partitioning) in which  simple  and easy-to-use governing
equations  are  used  to estimate the exchange rates  of
volatilization processes (e.g. Henry's law or two-film theory for
the volatilization between water  and air and Pick's law  of
diffusion between soil  and water).

     This paper  discusses and compares  the  governing  equations
for modeling volatilization processes in  existing toxic substance
multimedia models such as UTM  (Unified Transport Model developed
by  Oak  Ridge   National  Laboratory),   ENPART  (Environmental
Partitioning Model  developed  by  U.S.  Environmental Protection
Agency  and  General  Software   Corporation),  TOX-SCREEN  (a
multimedia screening  model developed by  Oak  Ridge  National
Laboratory) and  others (e.g. Mackey's and Neely's  Partitioning
Models).

     Chemical,  physical and environmental  factors  which affect
the volatilization/evaporation processes of toxic substances are
discussed.   Appropriate models   for  estimating  volatilization/
evaporation  of toxics at the  water surface between  water and air
and the interface (containing water,  soil and  air)  between soil
and air are suggested  and their complexity,  accuracy and useful-
ness are discussed.

-------
                                                                      Ledwell
Abstract for a paper to be presented to the International Symposium on
Gas Transfer at Water Surfaces at Cornell University, June 13-15, 1983:
       The Schmidt Number Dependence of the Gas Transfer Coefficient
                           James Robert Ledwell
                   Lamont-Doherty Geological Observatory
                            Palisades  NY  10964
     Transfer coefficients for NpO, CH^, and He at the air water interface
,vere measured in an l8 meter wind wave tank at moderate wind speeds.  The
transfer coefficient was found to vary with D , with the exponent 'a1 equal
to 0.4? + O.Ik (90% confidence interval).  The diffusion coefficients used for
N_0, CH^, and He were 1.84, 2.32, and 6.12 X 10~5 cm2/s at 23.5°C.  This
result supports models in which the transfer coefficient is proportional
to the square root of the Schmidt number (the ratio of the diffusion
coefficient to the kinematic viscosity of water).  The result is contrasted
with that for transfer coefficients at solid boundaries, where the analog
of 'a' assumes a value of 2/3.  The difference is attributed to the
boundary constraints which allow tangential convergence of fluid at the
air-water interface, but not at the solid boundary.

-------
                                                       Lincoff and Gossett
                                   ABSTRACT


          The Determination of Henry's Constants of Volatile Organics

               by Equilibrium Partitioning in Closed Systems

                                      by


                            Andrew H. Lincoff

                        Graduate Research. Assistant
                 Department of Environmental Engineering
                            Cornell "University
                                      and
                              James J4, Gossett
                            Associate Professor
                 Department of Environmental Engineering
                            Cornell University
                          Ithaca, New York 14853
      An accurate knowledge of Henry's constant is necessary for modeling gas

transfer in a variety of situations.  Unfortunately, great accuracy is diffi-

cult to achieve using straightforward measurement of gas and aqueous phase con-

centrations from equilibrated, closed systems.   Many of the compounds of current

interest are so sparingly soluble — and of sufficient volatility — that it is

difficult to construct accurate calibration curves with which to assay equilib-

rium concentrations.  This is particularly true of aqueous phase assays.  As a

result, current methods for determining Henry's constants usually involve the

use of a batch, diffused-air stripping tower, wherein it must be assumed that

equilibrium is achieved between the gas which exits the tower and the aqueous

phase through which it has bubbled (_e_.g_, , see Mackay et_ al, , Envir. Sci. S

Technol. 13, -333, 11979]}.  In our paper, we demonstrate that for many compounds

of high volatility frequently found in contaminated surface and ground waters,

mass transfer limitations exist which invalidate the equilibrium assumption of

the batch air stripping method.
*
  To whom correspondence should be addressed.

-------
                                                     Lincoff  and Gossett
                                                                   Page  2
ABSTRACT;  Lincoff, A. a.,  and J. K, Gossett,  "The Determination of Henry's
       Constants of Volatile Organics by Equilibrium Partitioning in Closed
       Systems."


       A novel  technique  is  presented •— Equilibrium Partitioning in Closed

Systems — which allows  the calculation of Henry's constant from the mere

ratio  of gas-phase concentrations resulting after equilibration of two closed

systems which  have been  prepared differently.  The technique is extremely

simple and is  free of mass  transfer limitations which reduce the utility of

other  techniques.  Since this new method uses only the ratio between gas con-

centrations of two equilibrated systems, knowledge of the actual gas phase con-

centrations is unnecessary.  This eliminates a major problem associated with

the research of volatile compounds in dilute solutions namely, the preparation

of calibration curves.   Henry's constants can be determined with a mean co-

efficient of variation less than 5%, solely using peak height data obtained

through GC analyses of headspace samples from two equilibrated systems.

Knowledge of the actual  mass of volatile substance added to the two systems is

also unnecessary.

       Using both our proposed technique — and that of Mackay et al. •*•— Henry's

constants for five compounds were measured over a range of temperature CIO -

30 C)  and ionic strength (0  - 1 N KC1)  typical of natural bodies of water.  .Mix-

tures  of the five compounds in water were also investigated.  The compounds,

tetrachloroethylene,  1,1,1-trichloroethane, trichloroethylene, chloroform, and

methylene chloride,  encompass a wide range of volatility and are all EPA prior-

ity pollutants.  Results demonstrate that for the more volatile of the compounds,

the batch air stripping method significantly underestimates Henry's constants

due to apparent mass  transfer limitations preventing  equilibration of exit

bubbles.

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                                              Ljubisavljevic
             Carbondioxid Pesorbtion from the Activated.




             Sludge in the Waste Water Treatment Plants






             bys Dejan Ljubisayljevid





          Faculty of Civil Engineering, Belgrade, Yugoslavia








Abstracts




It is necessary to study more in detail the desorbtion of



carbondioxid from the activated sludge, in waste water



treatment plants where biological nitrification occurs



(sensitive on the decrease of the pH) , and where pure



oxygen is applied as an oxidant.






Experimental results obtained from the laboratory models of



the surface and diffused air aerator are presented in this



article. Desorbtion of carbondioxid was measured with the



help of the pH-meter. Experiments were done both with tap



water only, and with tap water and surface active agents.





Results from the models were compared with the existing



gas transfer theories, and the validity of certain theories



were estimated.






From the carbondioxid desorbtion point of view, the conside-



rations on the results obtained from the field measurements



made at the pilot waste water treatment plant in Buesnaw



(Sttutgart, Federal Republic of Germany) are presented. The



field measurements on the mentioned plant in which biological

-------
                                             Ljubisavljevic




                       - 2 -







nitrification - denitrification occurs were performed by




the author in June 1982.






Among else, alkalinity and pH were analysed on the end points



of the nitrification and of the denitrification parts.



(Different from the carbon oxidation, besides the increase



of the carbondioxid content, nitrification decreases the



alkalinity of the activated sludge).






On the base of the theoretical and experimental considerations



the conclusions were drawen about the efficiency of certain



aeration systems on the desorbtion of the carbondioxid from



the activated sludge.





Some recommendations are propoused about the choise of the



aeration systems for the waste water treatment plants, were



special care is to be taken of the problem of the carbondioxid



desorbtion from the activated sludge.

-------
                                                                 Maclntyre
CURRENT FLUCTUATIONS IN THE SURFACE WATERS OF SMALL LAKES
    Sally Maclntyre, Department of Mechanical and Environmental
    Engineering and Marine Science Institute, University of
    California, Santa Barbara,  California   93106

    The transfer of momentum from the wind to the surface of a lake
creates fluctuations in velocity which are an expression of turbulent
eddies, surface and internal waves.  To know the scaling from the wind
stress to the stress at the surface of a lake is important for budgets
of energy transfer and models of mixed layer dynamics.   An environment
in which these processes have not been examined is shallow, naturally
eutrophic lakes with small fetches.  I used an omnidirectional warm-
bead thermistor-flowmeter  to measure fluctuations in current speeds
throughout the upper mixed layer of three shallow lakes in equatorial
Africa with differing exposures to wind.  The flow sensor resolved
speeds of less than 0.1 cm/sec and frequencies of ca.  5 Hz.  The first
four statistical moments, probability density functions, autocorrelation
functions, and energy spectra have been computed from the current records,
the mean and rms speeds have been compared with wind speeds measured two
meters above the lakes' surfaces, and Richardson's numbers have been
calculated.
    Current speeds within 1.5 cm of the surface fluctuated rapidly from
0.3 to 16 cm/sec.  The mean speeds were ca. 5 cm/sec and the turbulent
intensities (ratio  of rms speed to mean speed) were greater than 0.4.
The data records showed a graded shift from high frequency, high amplitude
fluctuations to lower frequency (ca. 2.3 to 0.3 Hz), smaller amplitude
fluctuations from the surface to 10 cm depth.  This shift occurred in the
absence of thermal stratification.  At 10 cm the turbulent intensity was
still high (0.25).  In thermally stratified water, waves with a frequency
of 0.01 Hz were observed within 30cm of the surface. These data illustrate
the extreme activity and variety of responses in low energy lacustrine
environments.

-------
                                                      Mackay
                                                       (Invited Keynote Paper)

                              Abstract for
                    Physical-Chemical Phenomena and
             Molecular Properties (Keynote Paper Topic  1)

                    D. Mackay, University of  Toronto

     The transfer characteristics of solutes between water and air are con-

trolled by the solute's equilibrium and transport properties.

     The equilibrium properties of aqueous solubility, vapor pressure and

Henry's law constant determine the relative concentrations at equilibrium

and hence the direction of transfer in any given situation.  Partition co-

efficients to solid or liquid materials in both air and water phases near

or at the interface and interactions with dissolved material may also play

an important role.  Methods of measuring correlating and estimating these

properties for gaseous liquid and solid solutes are reviewed and discussed.

     Mass transfer rates are conventionally expressed using a "two resistance"

approach in which mass transfer coefficients are invoked for each phase.

These coefficients are primarily determined by the local hydrodynamic regime

but are also influenced by the solute's diffusivity.  It is suggested that

air and water phase Schmidt Numbers currently provide the best characterization.

of solute properties and of temperature, when raised to an appropriate power

reflecting the exchange conditions.  Methods of obtaining and testing such

data are discussed.

     In view of the large number of solutes of potential interest, it is

suggested that a strong case can be made for improving the capability of

correlating and estimating these physical chemical properties for compounds

which are members of similar chemical classes.

-------
                                                Martinelli and  Liss
          THE EFFECT OF INSOLUBLE AND  SOLUBLE MONOLAYERS ON GAS
                  EXCHANGE ACROSS AN AIR-WATER INTERFACE

                      F.N. Martinelli  and P.S. Liss
                    School of Environmental Sciences,
                 University of East Anglia,  Norwich, U.K.
                              ABSTRACT

     Two series of laboratory tank experiments are described in this paper.
In the first series the simultaneous transfer of H2O, SO2, C»2 and O2 was
monitored across clean and monolayer covered water surfaces under conditions
of low hydrodynamic turbulence.  It is known that under certain conditions
insoluble monolayers are able to present a specific or barrier resistance to
gas transfer, and results presented here for long chain fatty acids and
alcohols are in reasonable agreement with previous work for the transfer of
^O and SO-, which is under gas phase control in these experiments.  For 02
and CO-, which are under liquid phase control, the specific resistance of
the monolayer cannot be seen against the intrinsically high resistance of
the water itself.
     Soluble monolayers do not fulfil the stringent requirements necessary to
present a direct resistance to gas transfer, but can provide an indirect
effect under conditions of high hydrodynamic turbulence.  In the second series
of experiments, the effect of the surfactant Manoxol O.T. (sodium dioctyl
sulphosuccinate)  was measured on the transfer of 02 under high stirring regimes.
The results show that surfactant concentrations as low as O.O1 mg 1   are
capable of significantly reducing 02 transfer velocities, and that reduction of
nearly 6O% can be obtained when the concentration of the surfactant exceeds
1O mg 1
     The ability of sea surface microlayer material, collected using a Garrett
screen, to retard gas transfer was tested in both series of tank experiments *
In the quiescent experiments no reduction was evident but significant reductions
were noted in the turbulent experiments and the consequences of this finding
for air-sea gas transfer are discussed.

-------
                                                               Matteson
                   ABSORPTION OF GASES AT CONDENSING



                     AND EVAPORATING WATER SURFACES



     Michael J.  Matteson,  Georgia Institute of Technology




                                ABSTRACT



      Observations of water vapor condensing on both  large droplets (2 mm)



 and NaCl nuclei (1 pm)  in the presence of a trace gas Y, indicate an en-



 hancement in the concentration  of Y in the liquid phase during condensation



 and a depletion of Y during evaporation.   A model is proposed wherein



 homogeneous clusters of gas molecules of the type Y- CH90)  formed in the
                                                      £  XI


 gas phase may explain these departures from expected mass transfer be-



 havior.  When Y=S02:
                 [SO-1   + n[H-01  *  [S07-n(H70)l

                    " 6      "  S>        *•     "   6
                    [S02-n(H20)]  *  [S02-n(H2OJ]£
                    [S02-n(H20)]£ *  [S02]z + n[H20]£
                    [S02-nCH20)J£ *  H
      During  condensation or evaporation, a water vapor pressure gradient



•establishes  a gradient in the gas phase hydrate.  Mass transfer coeffi-



 cients,  equilibrium constants and heats of solution were calculated for



 the  above mechanism.  Further tests with oxygen and N02 reveal similar



 patterns during the condensation- evaporation cycle, and a general model is



 proposed for absorption water soluble gases.

-------
                                                           McCready and  Hanratty



                  A COMPARISON OF TURBULENT MASS TRANSFER AT
                    GAS-LIQUID AND SOLID-LIQUID INTERFACES

                                      by

                   Mark J. McCready and Thomas J. Hanratty
                      Department of 'Chemical Engineering
                            University of  Illinois
                            Urbana, Illinois 61801


     For a number of years we have been studying the details of a turbulent

flow close to a solid boundary and have been using this information to develop

a theory for turbulent mass transfer.   This work has led to a picture of tur-

bulent mass transfer to a solid boundary which is radically different from

theories currently available in the literature.  Only very low frequency velo-

city fluctuations and, therefore, only a small fraction of the turbulent ener-

gy is effective in transferring mass.   The fraction of this energy decreases

with increasing Schmidt number.  In recent years we have been applying in-

sights gained in this work to the problem  of defining the mechanism of tur-

bulent mass transfer at a gas-liquid boundary.  This paper summarizes our

progress.

     The system in which our experiments are conducted is a 2.54cm x 30.48cm x 9m

enclosed rectangular channel.  Liquid  flows along the bottom of the channel

and air flows concurrently.  The rate  of oxygen absorption is determined by

measuring the change of the oxygen concentration of the liquid film at dif-

ferent distances downstream.  The wave properties are measured by a parallel

wire conductance probe.  The shear stress  fluctuations at the wall are

measured by a flush mounted thermal probe.  The film varies in height from  .05

to .55cm.  Air velocities from 4 m/s to 14 m/s have been used.  The viscosity

of the liquid can be varied using water-glycerine solutions.

-------
                                       MoCready and Hanratty
O
                      Re
                   Sc = 440
                    6900
                                 ILLINOIS
11500
                    25000
                    35000
                                TOULOUSE
                    45000
                    55000
                          00° o
                                   SOLID WALL
                             10
                              m
                        Figure 1.

-------
                                                           McCready and Hanratty









     Measurements of the mass transfer coefficient obtained with water are



shown in Fig. 1.  Here the friction velocity is defined in terms of the




interfacial stress, vi* = (t^/P>i)1 ^2 and the height of the liquid layer has



been made dimensionless using the friction velocity and the kinematic viscos-



ity, m+ = m v-*/v.  It is noted that for m+ > 45 the dimensionless mass trans-


                                               1/9   A
fer coefficient is approximately constant, k Sc1'  /v-_  =0.1.  For comparison,



measurements obtained in a 10cm x 20cm x 6m channel at the University of Tou-



louse (Tsacoyannis, 1976) with flowing liquid layers much thicker than ours



(1cm to 3.5cm) are also shown.  It is of considerable interest that such good



agreement is obtained in widely different systems, provided the results are



plotted in the manner shown in Fig. 1.  These results suggest that the velo-



city fluctuations controlling mass transfer are independent of the liquid



depth for thick films and are caused by interfacial shear.  Three mechanisms



are being explored as being responsible for these velocity fluctuations close



to an interface:  turbulence generated at the interface, turbulent velocity



fluctuations transmitted by gas flow shear stress fluctuations, and waves.



     From extensive experiments we have found that turbulent mass transfer at



a solid boundary is given by the equation



                            k/v *  =  0.8 Sc~'704 .
                               w


It is noted that this relation is similar to what is found for a gas-liquid



interface in that the mass transfer coefficient is related to flow variables



through the friction velocity.  This suggests that the shear at a gas-liquid



interface is producing turbulence by processes similar to what occur at a



solid-liquid interface.  Support for this is obtained from the measurements of



Suzanne (1977) which indicate a maximum in the turbulence intensity in the



liquid near a gas-liquid interface.

-------
                                                           McCready and Hanratty
     However, as shown in Fig. 1, the magnitude of the mass transfer coeffi-




cient is smaller for the solid-liquid interface.  A possible explanation for




this can be obtained from an analysis of the relation between the concen-




tration fluctuations and velocity fluctuations close to a boundary.  This




relationship for a clean gas-liquid interface, where the normal velocity var-




ies linearly with distance from the interface, is quite different from the




case of a solid-liquid boundary where the normal velocity varies quadratically




in y.  For a gas-liquid interface the concentration boundary layer does not




act as a filter; this means that mass transfer at a clean gas-liquid interface




is being affected by velocity fluctuations of all frequencies, and not just by




very low frequencies, as is true for a solid-liquid interface.




     The sharp drop off in k Sc ' /v^  noted for m  < 40 can be explained if




for small film heights, turbulence generation at the interface can be inhibit-




ed by the nearness of the solid boundary.  In this region the inflexible




boundary distorts the flow field and influences the scales of the turbulence



                                              1/2   *
produced at the interface.  Consequently, k Sc   /v.  is a function of the




gross flow parameters film height and gas Reynolds number for small m .




     For very thin films measurements from our wall shear stress probes indi-




cate that fluctuations in the gas flow are causing fluctuations in the shear




stress transmitted to the liquid film by the gas flow.  This provides another




source of velocity fluctuations in the liquid near the interface.  By using




measurements on turbulent shear stress fluctuations of air at a solid bound-




ary, we have carried out an analysis to estimate their influence in gas-liquid




mass transfer.  We find that the velocities scale with v. .  This suggests




that these fluctuations should give a contribution to k which increases




linearly with v  .

-------
                                                          McCready  and Hanratty
                                                                      5
     A tentative explanation of the results in Fig. 1 is that mass transfer  is

controlled by an additive effect of gas shear stress fluctuations being  trans-

mitted to the liquid and of turbulence being created in the liquid by  the

shear field interface.  As m+ increases the creation of turbulence in  the

liquid becomes relatively more important.

     It is well known that surface waves on freely falling films can cause an

increase of mass transfer over predictions for laminar flow.  A simple analy-

sis of the influence of waves on velocity fluctuations in gas-liquid flows

indicates a different scaling for k than what is given in Fig. 1.  This, in

addition to the observation that the same results are obtained in systems with

widely different wave properties (our data and the data of Tsacoyannis), would

indicate that the results in Fig. 1 are not explained by a simple wave

mechanism.

     Nevertheless, we have not ruled this out as a possibility^  Consequentlys

we are currently carrying out experiments which relate mass transfer rates to

wave properties.  We hope to be able to give a report on these at the

Conference,



References:



Suzanne, Christian, These du Grade de Docteur-Ingenieur, L'Universite Paul-

    Sabatier de Toulouse, 1977.



Tsacoyannis, Jean, These du Grade de Docteur-Ingdnieur, L'Universite Paul-

    Sabatier de Toulouse, 1976.



10/19/82

-------
                                                             Memery and  Merlivat

     GAS EXCHANGE ACROSS AW AIR-WATER INTERFACE  : RESULTS Of EXPERIMENTS
            ANP MODELING Of BUBBLE CONTRIBUTION  TO GAS  TRANSFER
                      LouAent MEMERV and LLLLan 9 m/4).  a  dtidden
/amp 0;$ -the  valued o^ fe.  -cd ofa^eAved. Thx^d ob^eAvatton -cd -cnteApAeted ad  bexng
the Aedatt   ojj the ondet ojj faAeafccng waved wh-tch cAeate babbled thAough whxch
mad4 ttand^eA  tafeed p^ace.  No dt^eAence ^OA gad exchange extheA ^.n ^edh wateA
OA xLn dea wateA had been  >cdent££ted ^Aom the who£e 4et o^  expeA-cmentd .
          A ^Asit theoAetcca£ appAoach to gad t^and^eA fai/  babbled ^d  andeAtafeen.
CeAtacn poAameteAd wh^,ch  aAe neglected bt/ dmooth  axA-wateA -oateA^ace mode£x.ngd
aAe dtadoed. It- -td iJoand  that tAond^eA ve^occttf -cncAeaded  when boiubJUiify decAeaded
FuAtheA, babble oveApAed^aAe £eadd  to wateA dapeAdatoAatcoKi at eqa-ctcbAuun,  thxd
dupeAdatuAotton bex.ng moAe d-cgnt^cant ^OA ^.ed-d io^ub£e gaded. 1^ the
veioccti/ AemaxLnd Aough£t/  condtant ^OA a vaAcafo£e concenttatton gAa
ec.tu£cbAtum, ^ctd Aange  0|J vaAcatton becomed -on^nxte neaA  eqtuZcbAiam.
an e^oAt ^d made to xJtcoApoAate doA^actantd -cnto the modeling.

-------
                                        -  2 -
                                                              Memery and Merlivat
           Beotu&e the, notion o£ tsuw&fieA v&tocity   tuAne.d cLuie.ctty to the. ££ux ^t&ii^ : the. ££ux JLt>  a. tineast function
o£ firm conc.&ntnatLon giadiznt* At tzabt  ^on. &ia.c,zni>, the,  c.oe.6&Lci&ntt> o$ thL&
function OJUL  e,ntuie£y  de^otecf by the. phy&i,co-diemLc&t ptwp&LtizA o£ the. g&&
and by the. bubble, dL&tru,bution. Re^atts  o&  YUMUU.CJOJL apptlcjation& cme.
foti kuLLum, siadon,  angon and cmbon dioxyde..

-------
                                                                  Metcalf
 Iii Situ pH Measurements as an Indicator of C07 Gas Transfer in
 GTaciaT Melt Waters                          L

 by

 Richard C. Metcalf
 Department of Geography
 University of Manchester
 MANCHESTER      M13 9PL
 England,  United Kingdom
      In situ pH measurements in glacial melt waters  from glaciers in

 Washington,  Alaska,  and Switzerland,  during 1977-1981 have firmly

 established  that CC^ gas transfer across the air-^water interface is the

 dominant process controlling hydrogen ion activity in these dilute waters.

 Detailed understanding of this  phenomenon is critical to : 1) evaluating

 "acid-rain"  pH observations  from snow in the high Arctic, 2) understanding

 the roles  of regelation and  subglacial precipitation in  controlling the

 basal sliding of glaciers, 3) correctly evaluating thermodynamic mineral

 stability  diagrams for rock  weathering in glacier  hydrologic systems, and

 4)  understanding the nature  and kinetics of CO- cycling  in the high alpine

 environment  in an effort to  further knowledge of the global C09 budget.
                                                              ^

      During  initial  spring snow melt,  melt waters  in the stream exitting

 the glacier  terminus  were often oversaturated with respect to PCQ , and
                                            _                    ^
 rapidly  increased pH during  outgassing at 0 C and  ambient atmospheric

 pressure.  This  appears  to be a result of CCL purification within the

 glacier by a presently undetermined process.  Not  surprisingly, after years

 of purification,  summer melt waters from "old" glacier ice in the ablation

 zone of a temperate glacier  are usually undersaturated by 10 to 100 times

with respect to atmospheric  PCQ , and  rapidly lower  their pH values to

achieve equilibrium upon encountering  the atmosphere.  Especially during

summer, proglacial stream waters sometimes  show pH increases from rock

weathering with the rate limited by the transfer of  0)2  across the air-water

interface to  drive the weathering, reactions.

-------
                                                           Metcalf     L






     dpH/dt experiments demonstrate that glacial waters achieve equilibrium



without agitation within 2 to 3 hours in 0.25 dm  polythene beakers at



in situ pressures and temperatures.  The change in pH is exponential with



time, driven by the Pm  gradient between the sample and the atmosphere.



By comparison,  melt waters in the shallow,  wide proglacial streams generally



achieve pH equilibrium in 10 to 15 minutes, primarily hastened by enhanced



gas transfer across the often turbulent  stream surface.

-------
                                                  Mines and  Sherrard
   THEORETICAL AND EXPERIMENTAL EVALUATION OF OXYGEN TRANSFER AND
    TOTAL OXYGEN REQUIREMENTS  IN BIOLOGICAL WASTEWATER TREATMENT

                                 by

                         Richard 0. Mines, Jr.
                                 and
                          Joseph H. Sherrard
                   Graduate  Student and  Professor
                      Dept. of  Civil Engineering
                               VPI&SU
                         Blacksburg, VA   24061


     A year long  study was conducted to  investigate the  ability  of  the
two film theory to accurately predict  oxygen  transfer  in  the  activated
sludge process and to evaluate  the  hypothesis  that  the efficiency of
aeration devices  installed in activated  sludge systems are not fixed  but
increase with an  increase in  the  oxygen  uptake rate as purposed  by
Albertson and DiGregorio [1].  Biochemical  stoichiometric equations are
developed as a function of wastewater  composition and  the mean cell
residence time to theoretically predict  oxygen requirements.  The
theoretical valves are compared with  actual  valves  obtained from an
extensive laboratory investigation.

     Two laboratory scale activated sludge reactors were operated over
a 3 to 20 day mean cell residence time.   Various  analytical tests were
conducted on samples taken from the influent,  effluent,  and mixed liquor
so that complete materials balances could be written.  The oxygenation
capacity and the overall oxygen transfer coefficient (K-,a) of the diffuser
stones (utilized for aeration)  was  determined in  tap water and  the  waste-
water effluent from each of the reactors under steady state and  nonsteady
state conditions.  Presently, data  are being obtained and evaluated.
Preliminary results indicate that the theoretical valves agree  with actual
valves and that activated sludge systems operating under a dissolved
oxygen limitation yield an effluent with a high nitrite-nitrogen
concentration in the range of 200 to 300 mg/1  if  the influent has  a
total kjeldahl nitrogen of approximately 450 mg/1.
    Albertson, 0. E. and DiGregorio, D., "Biological Mediated Inconsistences
    in Aeration Equipment Performance," Jour. Water Poll. Control Fed.,
    47_, 976-988 (1975).

-------
                                             Monahan and Spillane
THE ROLE OF OCEANIC WHITECAPS  IN AIR-SEA GAS EXCHANGE
                      BY
       Edward C. Monahan & Michael  C.  Splllane
            University College, Galway,
                      I re 1 and
     The wind dependence of the air-sea  gas exchange rate, as
expressed by the gas transfer  coefficient or piston velocity,
k8, has variously been described as  being linear (k'acU? Broecker,
1979), quadratic (k'
-------
                                                       Munz and Roberts
    The Ratio of Gas-Phase to Liquid-Phase Mass Transfer Coefficients
                    in Gas-Liquid Contacting  Processes

                    Christoph Munz and Paul Roberts,
                          Stanford University
 The objective  of the work   reported  herein   uas  to  assess   the relative

 importance  of  gas-   and liquid-phase   mass  transfer   coefficients  in

 diffused aeration,  surface  aeration and  packed columns.   Recently,  each

 of these  processes has been  considered as   a possible method   to strip

 volatile halogenated   organic  compounds   from solution   (1,2,3,4).   When

 modelling these systems,  previous workers (1,3,5,8,14)  consistently  have

 assumed a ratio  of gas phase  mass transfer  coefficient   to  liquid phase

 mass transfer coefficient (kg/ki)  of  150 as  the  criterion to assess the

 relative  importance  of  gas  and liquid  side  resistances.  The  value

 kg/ki-150 was inferred  from  average estimates for kg(H20) and ki(C02)  at

 the air-sea  interface  by Liss  and Slater(6)   and  thereafter applied  to

 volati1 nation/absorption   at    air-uater   interfaces    for    treatment

 processes(1,3,4,5,8,14)   as   well  as    natural  processes(8,9,10,11).

 However,   it  is likely  that  this ratio depends  significantly on  the  type

 of  system or   process and possibly also  within  a  given  system  depending

 on  the  flow conditions.



 Laboratory  experiments wore  carried out  modelling  diffused   aeration,

 surface aeration,   and  packed  columns in  which   the  following  compounds

 were stripped   out  of   solution while oxygen  was absorbed   (stripped  in

 packed column)  simultaneously:  CC12F2,  CHC13,  CH3-CC13,  CClt,,  CHC1=CC12

 and  CClj=CCl2-   The  surface  aeration   device consisted  of a  baffled

 cylindrical glass vessel  with  a liquid  volume  of 7.3  liters;   a ring-

guarded stirrer with  three pitched blades  uas used.   The  bubble  aeration

-------
                                                   Munz and Roberts
                                                            Page 2
 device  consisted of a glass column 22.5cm in diameter;  the diffuser was

 a ceramic  perforated plate and the liquid volume was 18 liters.   Packed

 column  experiments  were carried  out in  the same  glass column.    The

 packing material was 1/2-inch ceramic berl  saddles with a packed height

 of  40cm.    In all experiments non-adsorbing materials uere used:  glass,

 teflon,  stainless steel and ceramic.    Organic compounds were determined

 by  gas   chromatography,  and  oxygen  was  monitored continuously  with a

 probe.   The  procedure for surface  and diffused aeration  consisted of

 analyzing  the change in organics concentration with time.   In the packed

 column  experiments  five replicate  influent and  effluent samples  were

 analyzed after  reaching steady state.     In each experiment  an overall

 mass  transfer coefficient,  Kn*a, for each of the compounds was obtained

 by  using   an  appropriate   model  (accounting  for  partial  gas  phase

 saturation  in bubble aeration( 12)).    Linear  regressions of 1/Kn»a vs.

 1/He  were carried out to estimate kg«a  and ki*a according to the concept

 of  additivity of resistances:

      1      1        1
                                                                     (1)
                   Hc»kg»a

Although both kg and ki depend somewhat on diffusivity.   the approach is

reasonable because the diffusivities of  the halogenated organics differ

little  (Table 1).  Oxygen  data   were not  included  in the  regression

analysis.   Henry's Constants,    Hc,   were also measured(IS)   except for

CC12F2 and 02 (Table 1).



Fourteen  surface  aeration  experiments were  carried  out  at  varying

stirring rates from  131  to 376 rpm(13).  The results  of the regression
                                 - 3 -

-------
                                                  Munz and. Roberts
                                                          Page 3
 analysis  are  presented   in Table 2.  It is evident that  the ratio kg/ki

 decreases with  increased stirring.  At lou agitator speeds kia increases

 faster  than   kga.  At higher  speeds both values  increase approximately

 proportionally!   reaching what  appears a limiting value  of kg/ki « 20;

 the  correlation coefficients  are in general >0.95 in  the latter range.

 Also,   the  validity of  the  regression can  be judged by  comparing the

 measured  Kia(CCl2Fz) values with the predicted kia'ss these should agree

 closely>  which  indeed is the case.


 Fourteen  packed column experiments were  carried out(7)  varying the gas

 flow rates from 2  to 16  lit/min.   The results are presented in Table 3.

 The   ratio  kg/ki  increases  with  increasing  gas  flow rate,   but  is

 substantially smaller than  in surface aeration.  While  all correlation

 coefficients  exceed 0.92,  the predicted k ia's differ substantially from

 the  measured  KiaCCCl 2^2)  values at low gas flows.   This is because the

 gas  phase resistance is more important than the liquid phase resistance,

 i.e.  the slope of the regression  (1/kga)  is large and the Kia(CCl2F2>

 contributes little to  the regression.    To account for  this,  the data

 will be reanalyzed to obtain Kga values instead of Kia values.
Six preliminary  bubble aeration  experiments have  been carried  out at

varying gas flow  rates from 1.7 to  7-7 lit/min.   Results are  shown in

Table 4,  and  in this  case the  ratio kg/ki  appears to  decrease with

increasing gas flows. Negative predicted kga values can be attributed to

insufficient mixing.  An additional set of experiments will be conducted

to resolve this difficulty before the Symposium.

-------
                                                  Munz and Roberts
                                                         Page U
 In summary.  the data presented indicate strongly that kg/ki ratios vary

 from  system to  system and  also with  flow conditions  within a  given

 system.  It  is dangerous to assess  the relative importance of  gas and

 liquid  side  resistances  based  on   a  generally  accepted  value  of

 kg/ki = 150.



 REFERENCES
1.  Matter-Mueller,  C.,  W.   Gujer,   W.  Giger,  Transfer  of Volatile
    Substances from Mater to the  Atmosphere,  Uater Research,  15:1271,
    1981.

2.  Roberts, P. V., c. Munz, P.Daendl iker, Removal  of Volatile Halogena_
    ted Solutes by  Gas Transfer in Surface and  Bubble Aeration,   Paper
    presented at the 55th WPCF Annual  Conference, St.Louis, 1982.

3.  Mumford, R. L., J. L. Schnoor,  Air Stripping of Volatile Organics in
    Water, Paper presented at the AWMA Annual Conference, Miami, 1982.

4.  Kavanaugh, M. C., R. R.  Trussell,  Design of Aeration Towers to Strip
    Volatile Contaminants  from Drinking Water,  J.   AWWA,  72(12) :G34,
    1980.

5.  Rathbun, R. E., D. Y. Tai, Technique for Determining the Volatiliza_
    tion Coefficients of Priority Pollutants in Streams, Water Research,
    15:243, 1981.

6.  Liss,  P.    S.,  P.  G.   Slater,    Flux of Gases Across  the Air-Sea
    Interface, Nature, 247:181, 1974.

7.  Riojas,  A.  H.,  Trace  Contaminant Volatilization in Packed Columns
    with Two-Phase,  Countercurrent Flow,  Engineers Thesis,  Civil Eng.
    Dept., Stanford University, Stanford, CA., 1982.

8.  Smith, J.   H.,  D.  C.  Bomberger,  D.  L.  Haynes,  Prediction of the
    Volatilization  Rates of  High-Volatility Chemicals from Natural Water
    Bodies, Env.  Sci. Tech., 14(11):1332, 1980.

9.  Mackay, D., P.   J.  Leinonen,  Rate of Evaporation of Low Solubility
    Contaminants from Water  Bodies  to  the Atmosphere, Env.  Sci.  Tech.,
    9(13):1178, 1975.

10.  Smith, J.  H., D.  C.  Bomberger,  Jr., D.  L.  Haynes, Volatilisation
    Rates  of  Intermediate  and  Low   Volatility Chemicals  from  Water,
    Chemosphere,  10(35:281,  1981.
                                 - 5 -

-------
                                                  Munz and Roberts
                                                        Page 5
11.  Dilling,   W.   L.,   Interphase Transport  Processes.   II.   Evaporation
    Rates Rates of Chioromethanes,   Ethanes,   Ethylenes,   Propanes,  and
    Propylenes  from   Dilute   Aqueous    Solutions.    Comparisons   with
    Theoretical  Predictions.   Env.  Sci.  Tech.,  1K4):405,  1977.

12.  Munz, C.,   P.   V.   Roberts,   Mass Transfer  and  Phase  Equilibria in a
    Bubble Column, Paper  presented  at the AUWA  Annual  Conference, Miami *
    1982.

13.  Roberts,  P.  V.,  P.  Daendliker,  C. Hatter,  C.  Munz,  Volatilization of
    Trace Organic  Contaminants During   Surface  Aeration:   Model  Studies,
    Technical  Report No.   257,   Civil Eng.   Dept.,   Stanford University-
    Stanford,  CA., 1981.

14.  Albin, G.   W., G.   C.   Holdren,  Removal  of  Organics from Water in an
    Aeration  Basin:  A Mathematical  Model,  in press,  1982.

15.  Munz, C.,  P.   V.  Roberts,  Transfer  of Volatile  Organic  Contaminants
    into a Gas Phase During Bubble  Aeration,   Technical  Report No.  262,
    Civil Eng. Dept,,  Stanford University, Stanford,  CA.,  1982.
                                 -  6  -

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                                                            Neal
           REAERATION MEASUREMENT IN SWAMP STREAMS
                  RADIOTRACER CASE STUDIES

                       Larry A. Neal
               Law Engineering Testing Company
    Reaeration in swamp-like streams is particularly  difficult

to characterize due to the unusual variability of  swamp  stream

hydraulics and the difficult access for field survey  crews.  The

normal regulatory tendency is to use "conservative"  (low)  estimates

of reaeration rates when confronted with a swamp stream  situation.

Probably due to the difficulty in studying swamp streams,  there

is little published data on swamp stream reaeration.

    This paper presents the results of radio-tracer  (krypton - 85

and tritium)  studies of reaeration in several different  swamp

streams.  These swamp streams are located in Georgia, Louisiana,

North Carolina, and South Carolina with flows ranging from a few

cubic-feet per second (cfs) up to about two-hundred cfs.   Flow

velocities in the study segments range from less than 0.05 feet

per second (fps)  up to about one fps with measured reaeration rates

from about 0.05 to over 1.0 (per day, base e, 20°C).

    In addition to the tracer-measured reaeration  rates,   some

energy dissipation data are presented indicating that these swamp

streams are relatively efficient in utilizing available  head for

mixing and resulting reaeration.  Interim recommendations

are provided concerning reaeration predictions for swamp-like

streams and' further study needs are identified.

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                                                      Nguyen  et al.
EXCHANGE RATES OF GASEOUS SULFUR COMPOUNDS BETWEEN OCEAN AND ATMOSPHERE
        Ba Cuong NGUYEN, Christian RFRGFRFT and Gerard LAMBERT
                   Centre des Foibles Radioact-ivites
                      Laboratoire Mixte CNRS CEA
                                BP n°l
                    91190 - Gif-sur-Ivette,, France
        Biological activity plays an important role in the gaseous sulfur
compound exchanges between ocean and atmosphere. Indeed, this activity
evolves organic sulfur compounds, one of which is dimethyl sulfide (DMS).
This gas is rather insoluble and volatile, it escapes from the water,
oxidizes in the atmosphere to give S02 and then sulfates.

        Two cruises, in the Indian and Pacific Oceans, were undertaken
to measure DMS at the ocean-atmosphere interface. Measurements were taken
in the water and in the air at heights of 1, 10, and 17 m above the ocean
surface.  The results obtained during these voyages show a good correlation
between surface water and atmospheric concentrations. These concentration
gradients from surface water layer to atmosphere enable us to determine the
diffusion coefficent in the first 17 meters altitude over ocean, and conse-
quently the ocean-to-atmsophere transfer coefficient (or piston velocity).
These parameters depend mostly on meteorological factors (wind scale and
sea state, etc,..).

        From these parameters, gaseous sulfur compound oceanic production
in the atmosphere could be estimated to be about 30 x 106 tons of sulfur per
year.

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                                                          0'Connor
                                                          (Invited Keynote Jr'aper)
                     THE SIGNIFICANCE  OF  GAS-LIQUID  EXCHANGE
                     IN  WATER  QUALITY  MODELING &  ASSESSMENT

                               Donald  J.  O'Connor
                        Manhattan College,  New  York
    Environmental  probleus,  in  which gas-liquid  exchange plays  a  major role,
concern  aesthetics,   eutrophication   and  toxicity.     These   are not   only  of
environmental importance,  but also are of economic significance,  in view of the
costs of treatment and control methods which are invariably required to  address
such problems.

    Rational water quality management requires  the  application of mathematical
models  which  describe the  spatial  and  temporal  distribution of the   relevant
water  quality  constituents.    These  models  contain  transport, transfer  and
kinetic components.   While the  transport  factors  are  fairly well  established for
many  natural  water  systems,  little   fundamental  basis   exists  for  the
quantification of   the  kinetic  interactions  and transfer routes.   These
coefficients are either  assigned empirically or calculated from observations in
the  prototype  systems.    The  one  notable exception  is  the  gas-liquid   transfer
process, for which at least some theoretical basis exists for  the determination
of  the  relevant coefficient.   An objective element  is-thereby provided in the
important process  of the validity  of  the  water  quality model.   Furthermore, the
fundamental nature of the gas  transfer  relationships  permits extrapolation to
other  environmental  conditions,  an  element which  is an  integral part of the
planning process.   The  coefficient,  which quantifies the  process, is one which
may  be  determined   without  recourse  to  water  quality  measurements   in  the
prototype and  thereby,  provide  for  the validation  of  water  quality models and
the subsequent application in  water resources management.

    The  specific  constituents  considered are  oxygen,  carbon  dioxide,   ammonia,
sulfur  dioxide and  volatile  organic  chemicals, whose  concentration  in  natural
waters  is effected by the discharges  of  numicipal,  agricultural  and industrial
wastewaters, as well  as  been  natural  runoff  and  drainage.  The  first three gases
are important because of their  roles  in chemical  and  biological cycles.   Ammonia
is toxic to aquatic  organisms,  as  are  many volatile  synthetic  chemicals.  Carbon
dioxide, an  integral  element  in the  pH-acidity-alkalinity balance of a  natural
water  systems, is  important  in acid  mine drainage  and dry  and   wet deposition
from teh atmosphere.

    A brief description  of general  elements  of water quality models   is  first
presented.    A review of  the gas transfer  relationships  relating to dissolved
oxygen,  carbon dioxide, ammonia,  sulfur  dioxide and volatile  organic  chemicals
follows.   The  various viological, chemical  and physical  factors which  affect
these constituents are  discussed, including the significance  of  the gas-liquid
exchange.   The types of models,  commonly employed in the analysis of dissolved
oxygen  and  reactive  toxics,  are  reviewed.   For  the analyses of pH  and  inert
toxics, the  general   structure of  the models   are  suggested.   For  each
constituent, a practical  methodology  of  environmental  analysis and  examples of
practical applications are presented.

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                                               O'Connor
                               ABSTRACT
       Transfer Coefficients of Smooth Transitional and Rough Flows
                             D.J. O'Connor
                           Manhattan College

     Many constituents, which are susceptible to transfer through the
air-water interface, are of environmental importance.  Factors which
affect the exchange rate across this boundary are the air and water
velocities, the relative smoothness-roughness of the surface, and the
physio-chemical characteristics of the interface and of the transferable
constituents.  Fluid motion exerts a shear at the interface, which
establishes the structure of the boundary layers in both media.  The
dynamic features of these interfacial regions, defined the viscous
sublayer and roughness height, influence the transfer between air and
water.  Velocity functions are developed for both smooth and rough
surfaces.  Relationships between the transfer coefficient and these
hydrodynamic parameters are established for each regime.  A transition
function is also proposed for the momentum transfer which is used as a
basis to formulate the mass transfer relations.  The overall transfer
coefficient is expressed in the usual manner of resistances in series,
involving both the film and surface renewal concepts.  The latter is
predominant for smooth flow and the former for rough flow.  In the
transition, the viscous sublayer and thus the diffusional sublayer are
eroded with a simultaneous growth of roughness effects and cavities, the
latter imparting an additional resilience to transfer.  A constituent is
characterized by the solubility and partial pressure (Henry's Constant)
and by its diffusivity and viscosity of air and water (Schmidt Numbers).
Both liquid and gas film control are included in the applications.  The
proposed model yields reasonable and consistent correlation with
transfer data from a number of laboratory systems.  Extrapolation of the
relationships to prototype conditions are considered.

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                                                               Pankow et  al.
     INTERNATIONAL SYMPOSIUM ON GAS  TRANSFER AT WATER SURFACES
                        Cornell University
                         Ithaca,  New York
                         June 13-15,  1983

               James F.  Pankow and William E.  Asher
                Department of Environmental Science
                      Oregon Graduate Center
                      19600 N.W.  Walker  Road
                       Beaverton, OR.  97006
                                and
                           E. John List
          Department of  Environmental Engineering  Science
                              138-78
                California Institute  of  Technology
                        Pasadena, CA.  91125
 CARBON DIOXIDE GAS TRANSFER AT GAS/WATER AND  OIL/WATER  INTERFACES
                AS A FUNCTION OF SYSTEM TURBULENCE

       For processes which are not rate limited  by  chemical  reactions,
interfacial mass transfer will be controlled by  the fluid  mixing.   This
applies to transfer across both the gas/water  and the  oil/water  (e.g., pe-
troleum spill)  interfaces.  As they involve environmental  water  bodies,  such
processes are therefore often controlled by the  degree and nature of  the
turbulence underlying the interface.   Efforts  in our laboratories have been
directed towards the use of the pH-dependent laser-induced fluorescence  (LIF)
of fluores.cein compounds to characterize the mass transfer of C02  (an acid)

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                                                              Pankow et al



                                -2-









across both the gas/water interface and the oil/water Interface.   The photo-




diode monitoring of the LIF intensity in dilute fluorescein solutions




(vLCT8 - 10~7 M) as a function of depth allows the calculation of the C02




flux across the interface as well as across any internal solution surface.




Fine structure superimposed on the average signal has been found  to  be




caused by the mixing of turbulent eddies of fluid particles of dissimilar




net CC>2 content.  Turbulence has been generated by means of an oscillating




grid.  Mass transfer measurements have been made under conditions of varying




turbulence intensity, length scale, and distance to either the gas/water  or




the oil/water interface.  (In the latter case, the oil phase is maintained




saturated at a constant CC>2 level.) Experimental data will be presented and




conclusions will be drawn for gas transfer at the air/sea and oil slick/sea




interfaces.

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                                                              Papadimitrakis  et al,

    MEASUREMENTS OF THE FLUCTUATING PRESSURE  IN THE TURBULENT BOUNDARY LAYER
              OVER PROGRESSIVE, MECHANICALLY GENERATED WATER  WAVES
         By YIANNIS ALEX. PAPADIMITRAKIS, EN YUN HSU, and ROBERT STREET
                         Department  of Civil  Engineering
                     Stanford University, California  94305

      The structure of the  pressure and  velocity  fields  in the air above mech-
 anically generated  water waves was  investigated in  order  to  evaluate their
 contribution to the transfer of momentum and energy  from wind to water waves.
      Two wave-height gauges,  an  array of two  X  hot-film  probes,  a  specially
 designed high-sensitivity pressure instrument, and  five piezocrystal  pressure
 transducers  mounted on  the roof of the Stanford  wind-water wave facility were
 used  to monitor the water-wave height and the  velocity  and pressure fields in
 the air.
      The pressure  and  velocity measurements  in  the  air  boundary  layer  were
 performed  in  a  transformed Eulerian wave-following frame of  reference at  pre-
 selected distances from  the  wave  surface.   Seven  different  wind  speeds  were
 examined in  the range   140.59-402.04 cm/sec, with 1  Hz,  2.54 cm   amplitude,
 mechanically  generated water  waves.
      Measured  acoustic  and other pressure waves associated  with  the  traveling
 upstream-reflected  water wave  were  found to alter  the  wave-induced  pressure
 behavior.   These components  are an order of magnitude  greater  than,  and  com-
 parable  to. the actual wave-induced pressure.
      The nonlinearities  of the  propagating  water wave  and the drift  current
 seem  to  introduce  pressure components  at frequencies other than that of  the
main  wave.    Wave-wave  resonant interactions  and  wave-turbulence  nonlinear
 interactions  are  also responsible  for the  strong wave-induced pressure  har-
monics.

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                                                          Papadimitrakis et al.

                                                                          Page 2



     The wave-induced composite pressure coefficient, at the fundamental  mode,


shows in general  an  exponential  decay behavior, but the rate of decay is  dif-


ferent from that predicted by potential flow theory.


     The relative wave-induced pressure phase remains fairly constant through-

                                      »
out the  boundary  layer,  except at   c/Ufi  =  0.780  and  0.677.   This phase  dif-


ference  was  found to  be  about  130° during active  wave  generation,  pressure


lagging waves.


     The momentum and energy  transfer rates  supported  by the waves were  found


to be dominated by the wave-induced  pressure,  but  the  transfer of the corres-


ponding total quantities to both  waves and  currents may or may not, depending
on     c
       °o
     The contribution  of the  wave-induced  Reynolds stresses to  the transfer


processes is negligible.

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                                                                     Peng
                 INVASION OF FOSSIL FUEL  C02  TO THE  SEA
                              T.-H. Peng
                    Oak Ridge National Laboratory1
                      Oak Ridge, Tennessee  37830
                               ABSTRACT
     Our knowledge of gas transfer  at water surfaces can  be  applied to
environmental problems  such  as the  uptake of  fossil fuel  CO^ by  the
ocean.   CO-  exchange  rates  across  the  sea-air  interface  have  been
successfully estimated  from radon  profiles  in  the  upper few  hundred
meters  of  the  ocean  measured  during  6EOSECS cruises.   The  amount  of
anthropogenic  C02  uptake  is  estimated  by  the  one-dimensional   box-
diffusion model  of Oeschger et  al.  (1975).   The  zonal   variations  of
COp exchange rates  and vertical mixing  rates  as  derived from  6EOSECS
tritium  measurements  are included  in these  model  calculations.    The
results  of   these  calculations  and  the  amount  of  fossil   fuel  C0?
reaching major  active  carbon  reservoirs will be  discussed.
^Research  sponsored  jointly by  the  National  Science  Foundation's
 Ecosystem Studies Program  under  Interagency Agreement  No.  DEB 8115316
 and  the Carbon  Dioxide  Research  Division, Office  of Energy Research,
 U.S.  Department of  Energy,  under contract W-7405-eng-26  with  Union
 Carbide Corporation.

-------
  n™ I? u?T?ne^ented at:  iNTERNATIONAL SYMPOSIUM ON GAS TRANSFER
 TRANSFER AT WATER SURFACES to be held from June 13-15. 1983

    REAERATION    OF    TURBULENT    WATER

                    E.J. Plate and R. Friedrich

The reaeration of oxygen depleted turbulent water through the water-
atmosphere interface has been studied extensively, but the phenomenon
has not been fully explained. The most logical qualitative explanation
is the surface renewal theory according to which the water layer very
nearest the interface is enriched by molecular processes and then
swept into the interior of the water by turbulent eddies which pene-
trate the surface and remove the enriched layer. In the interior of
the water body, the oxygen rich water is mixed with its surroundings.
The process of surface renewal is diffuclt to be quantified, and even
more difficult to investigate experimentally, because it is non-stationary
and involves measurements near the surface which cannot be conducted
by standard transducers, such as hot wire anemometers.

It has been our belief that in order to solve the reaeration problem one
has to rely on circumstantial evidence, in particular on the action of
turbulence. Therefore we set up a program of studying reaeration on inter-
faces at which the turbulence has been generated by many different mecha-
nisms. From these experiments we hope to amass a body of experimental data
against which theories can be checkedj_The following experimental set ups
have been used: a stirred tank, with turbulence generated by an arrangement
of parallel horizontal rods located near the bottom of the tank, which could
be rotated about their axis; a wind wave tank with standing water, in which
the surface turbulence was generated by the shear of the wind and the wind
waves, and a wind wave tank with flowing water, in which waves and currents
acted as turbulence generators. Quantities which were measured included velo-
cities, turbulence intensities and spectra, wind waves, and optically visible
turbulent  cells.

Whereas the tank experiments lend support to the surface renewal theory
in the form given by Fortescue and Pearson (1967), one finds that the
wind wave results require a different explanation. Theoretical and experi-
mental arguments will  be presented which we hope will help towards establish-
ing  a unified surface renewal  theory without conflict between experimental
data and theory. The importance that this theory may have in evaluating
reaeration  in environmental  and chemical  engineering problems justifies
extension and continuing experimental and theoretical efforts.

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                                                         Rathbun and Tai
       VOLATILIZATION OF CHLORINATED HYDROCARBONS FROM WATER




                                 By




                    R. E. Rathbun and D.  Y. Tai




          U.S. Geological Survey, NSTL Station, MS  39529







                              ABSTRACT




     The distribution and the fate of organic compounds in the




waters of our environment are determined by the interactions of




a number of complex chemical, physical, and biological processes<,




One of the most important physical processes for many compounds




is volatilization which is the transport of the compound from the




water across the water-air interface into the air.




     This report considers two aspects of volatilization: (1) the




concentration dependence of the volatilization coefficient;  and




(2) laboratory measurements that permit estimation of the




volatilization coefficients of organic compounds in streams  without




actual introduction of the compounds into the stream,.  The discussion




of these two aspects is based on laboratory measurements of  the




volatilization characteristics of 1,1,1-trichloroethane and




1,2-dichloroethane.  Both these compounds are on the U.S. Environmental




Protection Agency list of priority pollutants, and both are significant




contaminants in surface and ground waters.

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                                                    Rathbun and Tai
                                                             Page 2
     Volatilization coefficients for the chlorinated hydrocarbons

and absorption coefficients for oxygen were measured in a stirred

tank in the laboratory.  The general procedure consisted of stripping

the water with nitrogen gas to reduce the dissolved oxygen concentration,

adding water containing sufficient dissolved chlorinated hydrocarbon

to give the desired concentration, stirring the water at a constant rate,

and measuring concentration as a function of time.  Hydrocarbon

concentrations were determined by a strip-and-trap procedure followed

by gas chromatographic analysis with a flame ionization detector.

Oxygen concentrations were determined using the Winkler technique.

     Experiments for each of the compounds at constant mixing

conditions over a wide concentration range showed that the volatilization

coefficient was independent of concentration.  This result confirms

the assumption that the volatilization process follows first-order

kinetics analogous to the kinetics for the absorption of gases such

as oxygen.

     Simultaneous measurements of the volatilization coefficient

for each of the compounds and the oxygen absorption coefficient

over a wide range of mixing conditions showed that the ratios of

the chlorinated hydrocarbon and the oxygen coefficients were independent

of mixing conditions.  The fact that these ratios are constant

makes it possible to estimate the volatilization coefficients for

these compounds for a given stream from estimates of the oxygen

absorption coefficient.

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                                           Arturo Riojas and Paul Kruger
VOLATILIZATION OF FISSION PRODUCTS          Civil Engineering Department
                                                Stanford University
   IN NUCLEAR REACTOR BUILDINGS                 Stanford, CA  94043

        Fission products released from a nuclear reactor core are distributed

   throughout the containment vessel:   in the reactor building atmosphere,  in

   the cooling system,  on building surfaces,  and in pooled waters that may

   form in the building.  Of particular concern are the volatile radionuclides,

   especially the short- and long-lived radioisotopes of iodine, which influ-

   ence markedly the cost and methods  of cleanup.   The potential for volatili-

   zation following a specific accident depends on the conditions under which

   a contaminated pool  of water formed and the thermo- and hydrodynamic condi-

   tions for volatilization from the pool.  The potential for volatilization

   also is dependent on the competing  processes, such as adsorption, pre-

   cipitation, and rainout in sealed buildings.  A study to identify and

   model competing processes that influence volatilization of fission products

   in pooled waters is  underway.  The  model is designed to incorporate these

   competing processes  into a prediction of volatilization as a function of

   water quality parameters, reactor building conditions, introduction

   of abatement agents  and time.

        Input to the model is the likely distribution of fission products in

   a reactor accident of given severity.  The model compiles a data base of

   pertinent literature data for the several  processes included in the numerical

   model.  Laboratory experiments are  underway to acquire necessary data not

   in the literature and a scale model of the TMI-2 containment vessel has

   been constructed for feedback and verification experiments to improve the

   model.

        Processes under study include:  volatilization from liquid- and solid-gas

   interfaces, rainfall in the saturated-humidity enclosed vessel, precipitation

   of solids from the pooled water,  adsorption from the liquid phase on

                                           1

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Abstract (Continued)                                  A. Riojas and P. Kruger






building surfaces, gas-phase adsorption on building surfaces, liquid-phase




adsorption onto suspended solids, gas and aerosol absorption by sprays and




condensation, and gas absorption by falling films.

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                                                                   Roberts

                       DEPENDENCE OF MASS TRANSFER
              ON ENERGY DISSIPATION DURING SURFACE AERATION

                            Paul V. Roberts
                     Department of Civil Engineering
                           Stanford University
                           Stanford, CA 94305

     It has been reported previously that the oxygen mass transfer rate
constant (IL. a) is proportional approximately to the specific energy dis-
sipation (P/V(W/m ) in streams (1) , large-scale surface aeration as practiced
in wastewater treatment (2), and in laboratory studies of surface aeration  (3).
The objectives of this paper are three-fold: to compare the proportionality
coefficients relating IL a to P/V in several kinds of systems observed; to
present experimental evidence that the values of !L a for volatile organic
solutes are approximately proportional to that of oxygen; and to assess
whether the values of the proportionality coefficients are consistent with
mass transfer models such as the surface renewal theory.  Significant
relations between the value of IL a for oxygen and the value of P/V have
been reported for streams (1), large-scale surface aerators (2), and a
laboratory-scale surface  aerator (3).  The dependence of IL. a on (P/V) dem-
onstrates a near-linear proportionality for each of the several systems.
Differences between the systems can be explained qualitatively in terms of
the method of energy dissipation.   In large-scale surface aerators the
energy dissipation is concentrated at the air-water interface; therefore,
the value of IL a is relatively large compared to the other contacting
systems, for a given specific energy input.   Conversely, the value of K_a
for a given energy input  is relatively low in streams because energy dis-
sipation occurs largely at or near the stream bed.  The laboratory experi-
ments reported here represent an intermediate case because the agitator used
was conceived as a combination surface aerator and mixer, with energy input
to mix the bulk liquid as well as  to promote air-water contact.
     The value of ILa for volatile organic solutes (CCl^, CCl^, CCl^CCl™,
CHC1=CC12,  CH-CCl-, and CHC1-) was found to be proportional to that of
oxygen over a wide range  of power  inputs.  The coefficient of proportionality,
3i = (ILa)./(tL a)   was in the range of 0.55 to 0.65 for the organic solutes

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                                                                   Roberts
                                                                      Page 2

studied.  The proportionality coefficient 3 was found to depend on the
ratio of diffusivities to the 2/3 power, in accordance with the boundary
layer and film-penetration models.  Nonetheless, the observation that K.a
is proportional to specific energy input seems inconsistent with mass
transfer theory as applied to a plane air-water interface.  The surface
renewal theory predicts a significantly weaker dependence of IL. a on P/V,
                 03
e.g., ILa <* (P/V) *  if the surface renewal rate is estimated as suggested
by Davies and Khan (4).  Similarly, boundary layer analogy approaches
predict 1C a.proportional to (P/V) raised to an exponent in the range
0.2 to 0.3, when the characteristic average velocity is evaluated using
either the Blasius Relation or Kolmogoroff-Turbulence Theory (5).
     It appears that specific energy input is a useful predictor of mass
transfer at the air-water interface in natural systems as well as engineered
surface aeration contactors.

References
1.  Tsivoglou, E. C., and L. A. Neal (1976).  J. Water Pollution Control
    Federation,  48, 2669-2689.
2.  Tchobanoglous, G. (1979).   Wastewater Engineering:  Treatment, Disposal,
    Reuse,  2nd edition, Mc-Graw-Hill Book Co, p. 497
3.  Roberts,  P., P. Dandliker, C, Matter, and C. Munz (1981).   Volatilization
    of Trace Organic Contaminants during Surface Aeration: Model Studies.
    Technical Report No. 257,  Stanford University,  Department of Civil
    Engineering, Stanford, CA. 92 pp.
4.  Davies, J. T., and W. Khan (1965).  Chem. Eng.  Sci.,  20,  713-715.
5.  Davies, J. T. (1972).  Turbulence Phenomena, Academic Press, New York
    and London,   p. 64

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                                              Roether and Kromer


 (Submitted to "International  Symposium on Gas Transfer at

 Water Surfaces"  Cornell  University,  June 1983)



 OPTIMUM APPLICATION  OF THE  RADON  DEFICIT METHOD TO OBTAIN


 AIR-SEA GAS EXCHANGE RATES



           Wolfgang Roether  and Bernd Kromer


     Institut fiir Umweltphysik der UniversitMt Heidelberg,


               Heidelberg, W.  Germany




                     72?
      The deficit of    Rn relative to radioactive equilibrium

                   226
 with the dissolved    Ra in the ocean's  mixed layer is caused



 by 2  Rn escape  into the atmosphere  and  allows  to determine


 gas exchange rates at sea.  The extensive spot  observations of



 radon deficits by W.  S. Broecker  and coworkers  (see Peng et al.,



 J.  Geophys.  Res.  8!4_  (1979) 2471)  give  averages  of this rate.



 We  persue  a  different approach, in which momentary gas exchange


 rates are  obtained in intensive and  carefully controlled field



 observations  and  are  used to  adapt gas exchange parameteriza-



 tions resulting  from  laboratory and/or theoretical investigations



 to  field conditions.



      We  made  222Rn-deficit observations  during  JASIN 1978 (^59°N,


 12.5°W)  and FGGE  1979  (^2°S,  22°W) ,  employing a precise and fast-


 acquisition,  automatic radon measuring system  (B.  Kromer and



W.  Roether,  "Meteor" Forsch.-Ergebnisse  A,  in press) .   The  FGGE


 gas  transfer  velocities average considerably  lower than those



 for  JASIN, despite little difference in  average wind velocity,


while  the range is  similar to  that observed  in laboratory experi-


ments.   The JASIN/FGGE difference is ascribed to considerably


steadier winds met during FGGE.  On  the  other hand,  our 222Rn-



deficit  time  series showed a  surprising  degree  of variability,

                                 OO O
which we believe to be caused by "  Rn redistribution in the


mixed  layer during the period between generation and escape


into  the atmosphere,  i.e.,     a few days.

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                                           Roether and Kromer
                      -  2  -


     At present we  are  preparing  the  next generation of field


observations.   The  most important requirements are anticipated

                                                  O 9 ^
to be  (i)  careful bookkeeping  of  the  mixed-layer    Rn deficit;


and  (ii)  adequate monitoring of the external  variables.


Ingredients  for (i)  are
                  • v

  - Obtaining repeated  222Rn deficit  observations MO min


    repetition) over periods of days  or longer,  the short-term


       Ra variability being monitored by salinity and  silica


    concentration,  with, continuous control of  system performance

    and" with on-line evaluation.


  - The observations are  preferably to  be carried out while


    drifting with the horizontal mixed-layer  flow.   The  local


    structure of the mixed layer and thernocline  is  to be moni-


    tored by temperature  and salinity profiling  and vertical


    current  shear is to be assessed.  Verification  of the


    absence of mixed-layer fronts in  the  observation area is


    desirable.


  - A suitable observation area is to be  selected.


As for (ii), meteorological variables have to  be  measured, but


furthermore also waves, and perhaps surface slicks, which play


an added  role;      improved understanding of the  effects of


waves would help in  outlaying the necessary measurements.


     On the basis of our  JASIN and FGGE results,  we  estimate


the achievable precision  in gas transfer  velocities  in such an


observational program as  ±20% under favourable conditions, and


the temporal resolution as 1Oh.  The necessary measurements and


their precisions can be  outlined, and  criteria  can be given  for


the selection of an  observation area.

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                                                                 Seaward, ex
                   EFFECTS OF EVAPORATION AND CONDENSATION

                            ON AN ABSORPTION PROCESS


                                          by
                                 David O. Seaward, PJE.
                                  Dr. Burton A. Segall
                                 Dr., Alfred A. Donatelll
                                   Dr. Charles R. Ott
                                      ABSTRACT

      Research was conducted to investigate the effects of evaporation and condensation on
a gas phase controlled absorption process. Individual  droplets of distilled water  of known
weight and temperature were dropped through a counter-flowing gas mixture that contained
a  known  concentration of ammonia  and  water  vapor.   The rates of evaporation  and
condensation of water vapor were varied by modifying droplet temperature and the water
vapor content of the air/ammonia gas mixture.  The droplets were collected after passing
through the gas mixture for each set of  conditions and the collected  solution  was analyzed
for ammonia concentration.  The resulting concentrations were then compared. Theoretical
Diffusion  Prediction Equations were  also derived to  predict the  effects  of  increased
evaporation and condensation rates on absorption.

      The  experimental results  indicate  that  absorption rates increase with  increases in
condensation rate and decrease with increases in evaporation rate.  The experimental trends
showed  good  similarity with  the  trends projected by  the derived Diffusion Prediction
Equations.

      The  intent of this paper is to present an overview of the test methods used, the results
obtained,  and the conclusions drawn.  Potential applications and implications of the results
are also discussed.

      The  theoretical  Diffusion Prediction Equations  are presented  along with  the simil-
arities between the experimental  absorption trends and those  projected by the Prediction
Equations  discussed. Due to assumed time constraints, detailed derivation of the Prediction
Equations  is presently considered outside the scope of this presentation.

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                                                                        Simpson


        ON THE EXCHANGE OF OXYGEN AND CARBON DIOXIDE BETWEEN OCEAN AND ATMOSPHERE
        IN AN EASTERN BOUNDARY CURRENT.  J. J. Simpson, Marine Life Research Group,
        Scripps Institution of Oceanography, La Jolla, California 92093.

      Simultaneous measurements of temperature, salinity, dissolved oxygen, pH, nitrate,
phosphate, silicate and chlorophyll-a were made continuously while underway from R.V.
New Horizon during July 1979.  The observations were made over a region of the northern
California shelf bounded by Pt. Arena to the north and Pt. Reyes to the south, off the
southern California coast near Pt. Conception and enroute between these two areas.  In
addition, discrete titration alkalinity and total carbon dioxide determinations were
made with the GEOSECS titrators approximately every 15 minutes during the underway
survey.  Water for these measurements was drawn from a depth of 3 meters via the un-
contaminated seawater system of R.V. New Horizon.  From these data the spatial distribu-
tions of dissolved oxygen, percent saturation of dissolved oxygen, partial pressure of
carbon dioxide and the PCQ? departure from atmospheric equilibrium were calculated.
These measurements show that the oceanic concentrations of dissolved oxygen and the
partial pressure of carbon dioxide in a coastal regime depart radically from equilibrium
values.  The spatial coherence and phase between these distributions cannot be explained
solely by physical dynamics.  The data support the hypothesis that the dynamics of gas
exchange in an eastern boundary current are largely controlled by biological processes.
The latter are clearly influenced by the physical dynamics associated with such features
as offshore jets, upwelling fronts and intrusions of warm Central Pacific water onto the
shelf.  The spatial distributions of chlorophyll-a and nutrients independently support  .
this conclusion.  The global distribution of biological productivity and its significant
impact on the air-sea exchange of oxygen and carbon dioxide demonstrate the need to
develop reliable remote sensing techniques to monitor synoptically global gas exchange
processes and their possible effects on climate.

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                                                           Sivakumar


            REAERATICN AND WIND INDUCED TURBULENCE SHEAR

                      IN A CONTAINED WATER BODY
    M.  Sivakumar,  B.Sc.(Eng),  M.Eng.,  Ph.D.,

    Department of Civil  and Systems Engineering,

    James Cook University of North Queensland,

    Townsville, Queensland,  Australia, 4811.
Reaeration in  contained bodies of water (such as lakes and ponds) is mainly

achieved by the oxygen transfer at the air-water interface and its subsequent

transport into bulk fluid.  The action of wind induces shear and causes

turbulence at the air-water interface which can significantly enhance the

reaeration process.



The process of atmospheric reaeration (it is, in fact, reoxygenation) can be

simply defined as the physical absorption of atmospheric oxygen in water.

However, the primary resistance to oxygen absorption in water takes place

at the water side of the air-water interface.  Detailed experiments were

conducted to study the relationship between reaeration and wind induced

turbulence in a laboratory size wind-water tank facility-  In this paper,

the results of the turbulence measurements and their correlation to reaeration

coefficient will be presented.



The reaeration and turbulence measurements were made simultaneously-  Hot-

film anemometer and surface floats were used to measure fluctuating and mean

components of the water drift.  Spectral analyses were made on the fluctuating

components.  These results indicate that there is a definite similarity

existing- between the wind induced water drift below the water surface and

flow past 'solid walls'.  This is indeed interesting in so far as the

transfer theories developed for the 'solid walls' may be applied to mass

transfer occurring at the water side of the air-water interface.

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                                 2.                     Sivakumar








Using the observed similarity and starting from the eddy cell theory of



mass transfer proposed by Lament (1970) for gas transfer in pipe flows,



an expression  is derived relating reaeration coefficient and wind shear



velocity.  Laboratory data seems to agree well with the derived expression.

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                                                    St. John et al.
                 THE SIGNIFICANCE OF GAS TRANSFER
                 ON THE DISSOLVED OXYGEN BALANCE

By:   John  P.  St.  John,  Thomas  W.  Gallagher,  and  Donald  J.
     O'Connor

    Dissolved  oxygen   is  widely  used   as  both  a  specific  and
general  measure of  water  quality conditions  in  the  streams,
rivers, lakes and estuaries of the country.   Sufficient levels of
dissolved  oxygen   are  necessary  to  support  fish   life  and
reproduction, and  to  maintain  a  balanced  biological  community.
Each state is  obligated  by the law to develop and  enforce  water
quality  standards,  and  all  such standards  contain specific
numerical requirements for  dissolved  oxygen.   The  vast majority
of  municipal  and industrial wastewater  treatment  plants in  the
United  States  were  built  primarily  to  protect  the  dissolved
oxygen resources of the nation's waterways.

    In many critical cases,  calculations are performed  to relate
the effect of specific wastewater  discharges to  dissolved oxygen
conditions   in  the  receiving  waters.    The   purpose  of   such
calculations   is to determine  the  specific  level   of  wastewater
treatment which is necessary  to  achieve or maintain   the  local
disolved oxygen standard.  The calculation procedure consists of
the  application of  a  water  quality  model  which  incorporates
relevant transport, transfer,  and  kinetic  terms associated  with
the dissolved oxygen balance.  Several  of the  kinetic  factors are
associated with the  utilization of oxygen  for  stabilization of
carbonaceous   and nitrogenous materials  present in  the  receiving
waters.  A particularly important factor, however,  characteristic
of  such  models  is  the  atmospheric reaeration coefficient  which
defines  the   rate  at  which  atmospheric  oxygen  is  transferred
through  the   air-water  interface   to  replenish  that  which  is
utilized in the stabilizaton of waste  materials.

    Many of the transport and kinetic  factors  incorporated in the
mathematical modeling framework are measured or empirically
determined  from  field  water   quality  data.    The  atmospheric
reaeration coefficient, however, is generally estimated  from one
of  a  number  of  formulations  which  have been developed  over  the
years by a variety  of  theoretical  and/or empirical means.   Many
of  the more  empirically  based  equations  were developed  from data
collected  for   specific  ranges  of  those  hydraulic and  physical
characteristics which  have a bearing on  the  gas  transfer process.
Such  formulations  often  give widely different  estimates of  the
atmospheric  reaeration  coefficient  when  applied   in  a  problem
context.  Their  differences  can  seriously affect  the  calculation
of  the oxygen balance, lead  to  a  misinterpretation  of  the effect
of  the  wastewater  discharge  on  the  oxygen  resources  of  the
waterway, and"  result  in  an  improper determination  (too great or

-------
small)   of  the  required  degree  of  waste  treatment.     Hence,
accurate  knowledge  of  the  reaeration  coefficient as represent-
ative  of  the  gas  transfer  process  is  required  for  proper
environmental and  economic decision  making.

    The  proposed  paper  will  illustrate  the  importance  and
significance of the gas  transfer  process,  as represented by the
atmospheric reaeration  coefficient,  on the  oxygen balance and on
the decision making  process, that  is,  on the  proper determination
of the  degree  of  required  waste  treatment.    An example  stream
situation will  be presented and described.  Wastewater  inputs to
the stream  will  be  described,  and  characteristic water  quality
profiles,  particularly  dissolved  oxygen  will  be  shown.   The
mathematical water quality  model  used  for  analysis  of data will
be described  as  well  as  procedures  for  evaluation  of  kinetic
coefficients.   It will  be  demonstrated that it  is  possible to
correlate a  particular  set of  water  quality (dissolved  oxygen)
data with different estimates of the reaeration coefficient.  It
will then  be shown that  the  different  reaeration coefficients,
when modified for and  used to  project  water  quality impacts at
critically  low  stream  flows, yield  markedly different results.
The  degree  of  waste  treatment  necessary  to maintain  the
equivalent level  of dissolved oxygen  in  the stream as calculated
with the different reaeration estimates will  be indicated.  The
practical  significance  of  gas  transfer  and  the  importance  of
atmospheric reaeration  in the  specifications  and design  of
wastewater treatment facilities  will  be  discussed.

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                                                                 Su  and Green
                           Experimental  Studies  of
                    Surface Wave Breaking  and  Air Entrainment
                          by M.Y.  Su  and A.W.  Green
                Naval  Ocean Research  and Development  Activity
                           NSTL Station, MS  39529
                         Tel.  (601)688-4733  or 5241

     Physical  processes of air entrainment and subsequent air bubble  generation
from breaking  of steep surface gravity waves under controlled situations  will
be described and discussed in  this  paper.
     It is generally known from actual field measurements that wind-wave
breaking in lakes and  oceans  contributes by  far  the most  significant  portion
of air/gas/particle transfers  cross the  water  surface;  and yet, the underlying
physio-chemical  processes are  only  poorly  understood.   To a large extent, this
slow progress  made so  far might be  attributed  to the  highly nonlinear complex
wave breaking  process  itself,  which has  defied full understanding of  physicists
and applied mathematicians despite  a  long  history of  both theoretical  and
experimental investigations.
     Recently, a close interplay between experimental  and theoretical  studies  has
lead to an important breakthrough  on  the physics of deep-water wave  breaking
as a consequence of a  new type of  three-dimensional wave  instability  and
subsequent bifurcation (for details see  Su (1982), Su et  al. (1982),  McLean (1982),
Saffman & Yuen (1980,  1982)).   This breakthrough now  provides, in turn, a sounder
foundation for us to study the gas  transfer  resulted  from such wave  breaking
processes.
     In this paper, we shall  present  some  preliminary experimental  results conducted
in a large-scale wave  tank, which  exhibits clearly the three-dimensional  wave
plunging and spilling  that cause air  entrainment and  bubble generation/transport
in the deep water.  The rapid and  complex  physical processes involved are recorded

-------
                                                                 Su and  Green
                                                                     .Eage_2  _


by photographic techniques.   These  experimental  results are then  used to delineate

general  characteristics  of the  physical mechanisms  involved.

     Finally,  we discuss the  relationship  of our results with previously published

results  and oceanic  observations.
References:

1.  Su, M.Y., (1982), J.F.M. 124, 73-108.

2.  Su, M.Y., et al., (1982), J.F.M., 124, 45-72.

3.  McLean, J., (1982), J.F.M., 114; 315-330.

4.  Saffman, P.G. and H.C. Yuen, (1980), J.F.M.,  101,  797-808.

5.  Saffman, P.G. and H.C. Yuen, (1982), J.F.M.,  124,  109-121.

-------
                                                           Theofanous
                                                           (Invited Keynote Paper)
                                                   *
                  Conceptual Models on Gas Exchange
     The characteristically high  Sc  number process of mass transfer at
free, turbulent gas/liquid interfaces  implies complicating as well as
simplifying factors in the development of general predictive methods.
The simplifications arise due  to  the thinness of the concentration bound-
ary layer that often occupies  only a minute fraction of even the smallest
turbulent eddies present.   The convective field can therefore be con-
siderably simplified into elementary flows, hence convective diffusion
solutions become readily  available.  The difficulties arise in relating
the characteristic parameters  of  these flows to the turbulence state in
the bulk (i.e., to measurable  turbulence properties).  Since these flows
within the concentration  boundary layer are not directly observable their
nature must be deduced by the  mass transfer response of the interface
(i.e., through conceptual  mass transfer models).  This process is often
further complicated by the need to crudely estimate the bulk turbulence
(lack of simultaneous  turbulence  and mass transfer measurements).
Although considerable  progress has been achieved along these lines during
the past fifteen years or so certain controversial aspects remain, primarily
due to the incomplete  definition  of mass transfer "regimes" within the
broad context  in which such turbulent interfaces are encountered.  A
critical, comparative  evaluation  of available conceptual models will be
presented in an effort to  identify strengths, weaknesses, and possible
additional  research needs.

*T.G.  Theofanous,  School  of  Nuclear Engineering, Purdue  University,
 West Lafayette, IN

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                                                Thomas  et al





Abstract for International  Symposium  on  Gas Transfer at Water




Surfaces,   Cornell,  June 1983
 ENTRAPMENT AND  TEANSPOHT OF BUBBLES BY PLUNGING WATER




          N.H. Thomas,  T.E. Anton, K. Sene, J.C.E. Hunt




              DAMTP, University of Cambridge
        Free  surface  penetration by plunging vater gives rise to




gas entrainment  and transport of bubbles in the submerged flows.




The phenomenon is  found in a variety of practical circumstances.




In chemical engineering it is exploited as a convenient method of




dissolving gases in liquids.  In environmental engineering,weir




flows provide for  reoxygenation of rivers and waste-waters.  In




oceanography  there is much interest in the transport of bubbles




from breaking waves (which appear as spilling or plunging flows




depending on  wind  conditions and water depth) . Factors affecting




the efficiency of  gas transfer into the liquid include entrainment




flux, sizes of bubbles, their ntsid«/ice,  times and dispersion




throughout the liquid.  Our studies, outlined below, e^m. particular/y




relevant to the  last of these.









        Using still photographs and high speed movie film, we




have observed that submerged plunging flovs transport bubbles in




discrete clusters.  We attribute this behaviour to bubble




entrapment by large transient vortices travelling in ihe free




shear layer between the submerged flow and surrounding bubbly




         The  existence of such vortices is HfeM-documented  —




they are often referred to as large eddies or 'coherent structures'.




        their inhibjtlnr 1'nfluSWe on bubble dispersion has^not

-------
                                                 Thomas et al.
                                                      Page  2

 been videly appreciated and our paper will help  to fill  this gap

 in understanding.



        We  shall describe elements of a recently developed

 general theory of bubble motion in unsteady, non-uniform^high

 Reynolds number flow.  The theory is based on inviscid analyses

 of the forces arising from pressure gradient, acceleration and

 vorticity-lift, together with a simple drag law.   Errors in

 previous formulae for interfacial forces will be identified.

 Having introduced "the general theory, we shall concentrate on the

 practically  relevant special case of bubble motion in line vortex

 flow.  A laboratoratory experiment will be described which

 quantitatively confirms the theoretical predictions of bubble

 entrapment:.



        We shall report on recent progress towards a   computer

 simulation of the bubbly free shear layer.  Our simulation

makes use of a discrete vortex method to model the fluctuating

 large eddy structure;  bubble trajectories are calculated using the

new general theory.   Exploratory tests  to date show indications

of bubble entrapment by transient vorticity concentrations.   We

wo^/ld Kofe. to present results of more  detailed calculations  now in

progress.   Also measurements of local gas and liquid  flows  in a

controlled experiment on the bubbly downflowing free  shear  layer.

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                                                       Top and  Clarke
                      ANOMALOUS NEON-HELIUM RATIOS
                            IN THE ARCTIC OCEAN
Zafer Top, Tritium  Laboratory, University of Miami, Miami, Florida
W. Brian Clarke, Physics  Department, McMaster University, Hamiltoni Ontario

Abstract;  Dissolved rare-gas studies in the ocean have become increasingly
important in the last decade.  The subjects of the present study, oceanic
helium and neo^have the  atmosphere as their major source.  The heavier
and more abundant helium  isotope "He, is sometimes augmented at the
sea-floor due to the injection of a sedimentary-crustal (radiogenic)
component.  Both helium and neon are often found in the ocean in excess
of their solubility equilibrium values due to the forced dissolution of
air bubbles in wave action (air injection) in the upper layers.  Because
there is apparently no mechanism to alter the neon concentrations in the
ocean, neon can be  used to strip off the air injected helium component.  In
a recent study of the Baffin Bay (Top et al., 1980) however, this procedure
gave rise to negative helium excesses!  What seemed to be a suspicion then,
of the constancy of the neon concentration became a certainty in the later
studies at two Arctic locations.  The data confirming the anomalous  He/Ne
ratios are presented.  The source of the anomaly appears to be at the
surface.  The ice formation is thought to be primarily responsible for
the relative enrichment of neon.  As well, differential diffusion of neon
and helium in ice,  and ice melting are discussed as potential contributors
to the observed effect.  The great potential of Ne/He ratios in the
Arctic Regions (and probably Antarctic) as a tracer for the newly formed
bottom water is proposed.
Ref:   Z. Top, W.B.   Clarke, W. Eismont and E.P. Jones. (1980) Radiogenic
Helium in Baffin Bay bottom water.   J. Mar. Res., 38, 435-452.

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                                                        Topalian  et al
                    On the Exchange Rate of Organic Gases
                     Between Air and Falling Water Drops
                 J. H. Topalian, S. Mitra, and H.  R. Pruppacher
            Cloud Physics Laboratory, Dept. of Atmospheric Sciences
                    University of California,  Los  Angeles
                                 Abstract


     The exchange rate of organic gases  between  falling  water  drops  and

air has been studied as a function of drop size  and  concentration  in the

gas phase.  The study was carried out using the  UCLA Rain-Shaft, a unique

facility consisting of a 35 meter high and 50  cm diameter  shaft which

allows a quantitative determination of the amount of gas scavenged by

water drops after reaching their terminal  velocity.   Following a success-

ful study on the exchange rate of SO- between  air and  falling  water  drops

(Walcek et al., 1981: J. Atmos.  Sci., 38,  871-876) using the same  facility,

we determined the rate of absorption of  the organic  gases: acetaldehyde,

formaldehyde, methylene chloride and chloroform  by water drops of  300 to

2500 ym equivalent radius, falling at terminal velocity  in air as  a  function

of gas concentration.  The concentration of the  organic  gas in the gas phase

and in the water were determined using gas chromatographic techniques.  The

results of our experimental  study are compared with  and  discussed  in

light  of the results  derived  from our theoretical  model  for forced   convec-

tive gas absorption by falling water drops which exhibit internal  circulation,

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        A New Optical Bubble Measuring Device
                                                          Wais et al,

        T.  Wais,  M. Barabas, B. Jaehne
        Institut  fur Umweltphysik, Heidelberg University
        Western Germany
Encouraged by the good experience with optical wave measuring systems
we developed an optical method to measure bubbles in the water.
                                                         t
A He-Ne-Laser beam pierces the water surface vertically from below.
The light scattered by bubbles crossing the beam is collected in 4
detectors at different depths ranging from 0.1 - 0.5 m. Two sets of
this arrangement are used with differnt laser beam diameters (1 and 5
mm) for the following reasons. Firstly, the dynamics in bubble size
and even more in intensity detected beeing proportional to the square
of the bubble radius is too large for only one detector. Secondly, the
large bubbles are rare if compared with small ones, and a larger
sampling volume is therefore necessary to obtain good statistics.

The first measurements with this device are carried out in the large
wind/wave facility of the I.M.S.T Marseille, simultaneously with He-
and Rn gas exchange experiments. We obtained bubble spectra at four
water dephts in the wind speed range from 11 to 13.8 m/s. First
bubbles are observed at 12 m/s. The spectras are compared with other
wind tunnel results. The total number of bubbles is about a factor 3
smaller than in the wind tunnel of the Sonderforschungsbereich
Meeresforschung, Hamburg.

With a simple model we estimated that even at the highest possible
wind speed of the large facility (13.8 m/s) no noticeable enhancement
« 10t) even of the He gas exchange is possible.

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                                                                   Waldichuk









          LABORATORY OBSERVATIONS ON TRANSFER OF ATMOSPHERIC OXYGEN




                          INTO STRATIFIED SEA WATER




                             By Michael Waldichuk




                          West Vancouver Laboratory




                      Department of Fisheries and Oceans




                              4160 Marine Drive




                    West Vancouver, B.C., Canada, V7V 1N6









                                   ABSTRACT




     Laboratory sea later las stripped of most of its dissolved oxygen by




bubbling nitrogen through it in a column filled  vath marbles.  The sea vater,




starting lath dissolved oxygen concentrations of 0.5 to 1.0 mg/L,  las held in




a round plastic container, 56 cm high and 34 cm in diameter at the top, in a




later table vith sea later 14 cm deep at a temperature of 12~18°C.  Water




samples rare taken at the surface, 10, 25, 40 cm and at the bottom of the




container periodically for dissolved oxygen determinations.  Within 4 days,




dissolved oxygen concentrations reached 7 mg/L at all depths,  tfien only sea




rater las present; but then a 2-cm layer of fresh later covered  the  sea




later, dissolved oxygen in the bottom half of the container, starting at 1.0




mg/L, ranged from 0.3 to 0.6 mg/L after 5 days.  In deoxygenated sea  later




(0.5 mg/L), covered lith a 1-mm layer of South Louisiana crude oil, dissolved




oxygen las near 1 mg/L at the bottom of the container, 3 mg/L at 25 cm depth




and 5 mg/L at 10 cm and at the surface after 5 days.  Results suggest that




stratification  ilth fresh later can be at least as effective as a  thin layer




of oil in retarding the transfer of atmospheric oxygen dowivard in sea




later.  They are in line also  lith observations of vertical  dissolved oxygen




distributions found in deep, partially-restricted marine inlets receiving




substantial fresh  later runoff.

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                                                       Warhaft  and Bolgiano
                    Moisture and Heat Transport in a Stably
                Stratified Boundary Layer Over a Water Surface
                        Z. Warhaft and R. Bolgiano Jr.
                              Cornell University
                                Ithaca, NY  14850

     A  laboratory  experiment  in which a stably stratified  boundary layer was
formed  by blowing warm, dry air over a water surface is described.  The exper-
iment was carried  out in the  air-sea  interaction facility  of  d'Institute de
Mechanique Statistique de la Turbulence  (I.M.S.T.), Marseille.  Velocity, tem-
perature and  humidity fluctuations were measured  by  means  of hot  (and cold)
wires and a microwave refractometer.   In order to obtain high bulk Richardson
numbers,  Ri'b,   [ = (g/PQ) (ApL/U2)   where   Ap  is   the  density   difference
across  the depth L  of the boundary layer,  U is the free stream velocity, g is
the  gravitational   acceleration  and  p   is  a reference   density] low  wind
speeds  (£ 0.7 m/s) were used.  Under these  conditions,  the water surface re-
mained  smooth.   Particular attention was  given to a  situation  in which  the
Ri.   was  so   strong(~0.4)  that  the  boundary  layer  turbulence,   tripped  by
means of vortex generators at the entrance to the tunnel, was rapidly suppres-
sed.  However as the  flow evolved  downstream  and  the  boundary layer thickened
 (and  hence   Ri.  diminished),  bursts  of  turbulence  occurred  close   to  the
water surface,  causing  rippling of  the  water.   Most  of the momentum, heat and
moisture transport occurred during these bursts.   Classified averaging of the
momentum, heat  and  moisture flux  formed  from  the  time series of the velocity,
temperature  and humidity  fluctuations   showed  remarkable  similarity   to  the
intermittency  observed in the neutral boundary layer (at a much smaller scale)
by  previous  workers.  The results  also  have  similarities  to bursting observed
in  river estuaries and in the sea.

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                                                  Whittemore
        An Assessment of Tracer Techniques for
            Measuring Reaeration Rates in
                  Large River Systems


             By:  Raymond C. Whittemore, PhD
              National Council of the Paper
      Industry for Air and Stream Improvement, Inc.
         Tufts University, Medford, MA  01890

     NCASI had the opportunity to investigate tracer techniques
for the estimation of stream reaeration rates during its study
of mathematical water quality modeling on the Quachita River
basin.  Data was first collected which allowed for the exam-
ination of the variablity of measurements of stream reaeration
rates which were subsequently used to assess uncertainty
in the calibration and verification of four water quality
models.  This study was followed by a comparison of hydrocarbon
and radiotracer techniques on the same river reach„

     The major conclusions from these studies were two fold:

      (a)  The precision of the radiotracer measurement was
directly related to the amount of gas lost during the experi-
ment. Thus, the precision of the measurement is ultimately
limited by an ability to follow the dye and conservative
tracer, the precision of the krypton to oxygen transfer ratio,
and the temperature correction factor.

      (b)  The hydrocarbon tracer techniques produced reaeration
rates higher than that obtained by the radiotracer technique
and selected empirical equations.  This difference was two
large to be accounted for by variability in the radiotracer
method.

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                                                               Wilcock
                   METHYL CHLORIDE  AS  A GAS-TRACER IN REAERATION



                         STUDIES  ON  SOME NEW ZEALAND RIVERS







                                 Robert J. Wilcock



                           Water and Soil Science Centre,



                           Ministry  of  Works and Development,



                           Private Bag, Hamilton, New Zealand.
Many New  Zealand  rivers  receive waste  inputs with  significant  oxygen demands



from sources  such as  dairy  factories and wood-pulp mills.   In  order to have



effective models  of dissolved oxygen profiles  in these  rivers  it is necessary



to have accurate  estimates  of the reaeration coefficient, K_.  This paper



describes a gas-tracer technique using methyl  chloride,  that has been



developed and successfully  tested in several rivers  and streams.  Methyl



chloride  is a stable  substance not found in significant background concentrations


                                                          -12
in New Zealand waters, that can be detected down to  1 x 10   g by a gas-



chromatographic technique.  In this study, values  of K« and an analagous



gas transfer  coefficient for methyl chloride,  K „  _.., were  measured simultaneously



in laboratory experiments over the temperature range 5  - 35 C.  The results



indicated a temperature dependence for the transfer  coefficient ratio, K    _/K_,
                                                                        Cn_ul  /


which was fitted  empirically to an expression  based  on  the  absolute rate model
for diffusion, giving
                     KCH Cl

                     — == —  =  4.323 exp(-530.97/T)

                       K2
where T is the absolute temperature.

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                                                          Wilcock

                                                          Page 2




Results are given of applications of the methyl chloride  technique in several


rivers, in which rhodamine-WT was used as a conservative  tracer to correct


for dispersion and dilution.  The measured reaeration coefficients range from


0.2 to 16.6 day"  (base e) and are compared with values calculated using the


O'Connor-Dobbins formula.  The experimental results correlate well with the


calculated values but are generally about 50% greater than the predicted

                                                                          — 1
values of K .  It is concluded that for K  values greater than about 1 day


the methyl chloride method gives values having a much better precision than


those calculated from empirical expressions, and provide estimates of K«


with an uncertainty of about + 10%.  The major source of error in the tracer


technique appears to be associated with estimating peak concentrations of


the dissolved methyl chloride.   Empirical expressions can give rise to


errors of + 50% in their estimates of K_ in streams having irregular cross-


sections, or where estimating mean depths is difficult.   Rivers in which K


was 1 day   or less had comparable uncertainties between measured and


calculated values of the reaeration coefficient, because of the small


change in the ratio of methyl chloride : rhodamine-WT peak concentrations,


with distance downstream.

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                                                                         Yu
                   WIND EFFECT ON AIR-WATER OXYGEN TRANSFER
                                   IN A LAKE

                                      by

                                  Shaw L. Yu
                            University of Virginia
                           Charlottesville, Virginia


     The  paper  will report results  obtained  from field experiments conducted

in  a lake in Northern New Jersey  to  investigate the  effect  of wind  on the

air-water  oxygen  transfer  process.   Mass  transfer and boundary layer theories

were utilized  to formulate theoretical  prediction models for  the reaeration

coefficient, K_.

     Parameters  considered in model  formulation  include wind  velocity,  wind

shear  velocity, effective mass  diffusivity, and water depth.   Equations of

linear, nonlinear, and dimensionless forms were examined.  Statistical methods

such as analysis  of  variance  and residual analysis were employed to determine

model adequacy-

     Results indicate  that wind speed is a  limiting  factor  in affecting lake

reaeration.  Below  a "critical" wind  speed  (4.2  m/s at  10  m) , there  is no

significant wind  effect  on K_.  Above another  "critical"  wind speed (6.5 m/s

at  10 m), K9 varies nonlinearly with wind speed.  Between these two limits, K

assumes  a  fairly  linear  relationship  with  wind  speed,  as  shown  in  the

following dimensionless equation:

                  K9H2             . /UH \ 1.136
                  —	1.63 x 10   f —y
                    v                   v '

where K_  = reaeration coefficient  in sec  , H = water depth  in meters, v =
                    2
water viscosity in m /s, and U = wind velocity at 10 meters in m/s.

     An investigation was  made later to test some  of the proposed reaeration

equations  using  data  collected  for  the  Occoquan  Reservoir  in  Northern

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                                                                        Yu
                                                                        Page 2
Virginia.  Two years  of  water  temperature and dissolved oxygen data  taken  at

various depths and at six stations throughout the lake were available  for  the

analysis.  Wind recorders were obtained from two locations in  the vicinity  of

the lake.

     The  Occoquan  data  indicate  that  the  wind  is responsible  for  keeping

dissolved oxygen levels near or above  saturation  for  the upper 1  to 3  meters

of the lake  even  though  the lake  is strongly stratified and dissolved  oxygen

levels dip to zero near the bottom of the lake.  The proposed  lake  reaeration

equation  was also  found  to  be  adequate in  predicting  surface   reaeration

coefficient.

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