United States
                    Environmental Protection
                     Off ice of Water
EPA 503/6-90-003
September 1990
The Green Bay Mass
Balance Project
An Advanced Analytical  Model
For Environmental Management
                    GREAT LAKE^NATIONAL ESTpA^gROGTW^
                                       The Green Bay System
                                     Compartments and Fluxes of Contaminants
                                                           ry  :.:..
                                                       ;.Deposition .;.;.;.;.;
                                           Green Bay System
    Green Bay Mass Balance Study is a pilot project to
 .evaluate the feasibility of mass balance modeling for
 toxic substances as a basic planning and management
 ^tool in restoring Great Lakes Water Quality. If proven, the
 Irnethodologies employed in the Green Bay Model offer
 ^n accurate process for pollution control and remedial
 action plans. Engineers and policy makers will be able to
 temploy lake- and basin-wide simulations to test the costs
                  and benefits of alternative policies with greater confi-
                  dence than any current process.
                    The Green Bay Mas's Balance Study will be of most
                  interest to National Esl:uary Program participants in-
                  volved in scientific applications, to the Technical Advi-
                  sory Committees, and to those managers and staff who
                  are designing long-term monitoring strategies.
                                                          Printed on Recycled Paper


Since the first Great Lakes Water Quality Agreement was
signed in 1978, the Great Lakes National Program Office
has worked to restore proper functioning of the Great
Lakes ecosystem.   While early  work focused almost
exclusively on reducing eutrophication by controlling
nutrient inputs, more recent efforts have expanded to try
to understand and control inputs  of toxic contaminants.
Techniques used early in the program that resulted in
effective nutrient control methods may, with modification,
be useful in managing toxic contamination.
    When scientists began to focus on the major causes
of eutrophication in the 1960s, they constructed basic
input-output models of the Great Lakes to determine the
most immediate (and cost-effective) measures  to ad-
dress the problem. Those analyses highlighted the need
to control phosphorus discharges to the Lakes.   Re-
sulting control actions  included  banning phosphorus-
based  detergents, modifying industrial and  municipal
sewage treatment plant operations, and improving soil
conservation practices by farmers in the watershed, all of
which  reduced phosphorus  discharges. Such controls
have already resulted in marked improvements in the
Great Lakes' ecological health, especially in Lake Erie.
Signs of improvement include, for example, revitalized
fish communities.
    Further studies  have shown that a similar input-
output methodology may be applicable to toxic pollut-
ants, although the analytical and modelling processes
are more  complex.   When studying  pollution control
technologies, a model  or series of models  would
accountforthe flows of the most important toxics through
the Great Lakes, from when they enter the lakes to when
they leave.  This input-output scheme, based on the
principle of conservation of mass, is referred to as Mass
Balance Modelling.
    Scientists and policy-makers hope to use the tech-
nique to evaluate alternative strategies for controlling
toxic contamination in the Great Lakes. This fact sheet,
prepared by EPA's Office of Marine and Estuarine Pro-
tection and the Great Lakes National Program  Office,
describes the Green  Bay Mass Balance study. Other fact
sheets in this series address the overall management
framework for the Great Lakes  Water Quality Agree-
ment, and the multi-state (and international) fish  moni-
toring  program for  measuring the presence of toxic
chemicals in commercial and recreational fish species.
An earlier fact sheet covers the Great Lakes National
Program Office load management strategy for phospho-

 Study Objectives

The Green Bay Mass Balance Study was begun to test
the feasibility of using a mass balance approach to
assess the sources and effects of toxic pollutants which
are spreading throughout the Great Lakes food chain.
Specific objectives include:

   Assessing the technical and economic feasibility of
    the Mass Balance approach for use in the manage-
    ment of pollutant  loading and  impacts on Great
    Lakes ecosystems;

   Calibrating the Mass Balance model for sources,
    transport routes and fates of pollutants in the Great
    Lakes ecosystems in general;

   Identifying the major sources of pollutants entering
    the Green Bay ecosystem and ranking their relative
    significance; and

   Demonstrating  methods and priorities  for  further
    studies of toxic pollutants in the Great Lakes.

    Four chemicals and chemical groups representative
of major classes of toxic compounds were selected for
the Mass Balance Study. They are: PCBs (and related
compounds), dieldrin (a pesticide), cadmium, and lead.
By including the entire  family of PCB chemicals, the
study will actually measure 209 chemicals, over 80 of
which are currently found in detectable quantities.
    Inputs of these chemicals have been measured in all
of the major surface water tributaries flowing into Green





Field and


Field and
Biota Analytical

Bay, in point sources, in wet and dry precipitation and in
groundwater. The goal of the Green Bay Mass Balance
Study  is to predict the concentrations of  these four
chemicals in walleye pike, brown trout, and carp (the
defined end points of the study's food chain) to  an
acceptable level of accuracy, at an affordable cost. Once
a mass balance budget has been established for each
pollutant of concern, it should be possible to simulate the
long-term effects  on  Great Lakes  water  quality  by
mathematical modeling.

     The basic mass balance model can be reduced to the following formula:

        Input  +  Generation - Accumulation - Consumption = Output
Transformed or
 within system
To meet the study goal for accurate prediction of toxic
pollutants in the fish at the end of the food chain, study
planners estimate that data collection and analysis
procedures must be accurate to within 20% of actual
mean values for major sources and "compartments" of
pollutants. In the world of ecological research, these
are very stringent requirements.
   The study began in 1986, with preliminary monitor-
ing and planning, and is scheduled to be completed in
1991. The bulk of the data sampling was performed
during 1989 and 1990.
   The Study's annual funding in Fiscal Years 1989
and 1990, provided by GLNPO, was $1.1 million, with
minor additional contributions from the other participat-
ing agencies.

Lessons Learned

If successful, the Green Bay Mass Balance Study can
provide the International Joint Commission with a new
range of scientifically validated analysis and planning
tools for managing pollutant loads throughout the Great
Lakes. While the scope and cost of the Green Bay Study
are beyond the means of other areas just getting involved
in the National Estuary Program, there are important
lessons to be learned from the Green Bay Mass Balance

 There are major advantages to be gained from
   organizing a method for coordinating a variety of
   individual scientific projects (most  of which will be
   carried out by academic interests, whether there is
                                               an estuary program or not). By working with local
                                               academic, scientific, and environmental consulting
                                               groups to identify major ecosystem issues in the
                                               estuary, by  defining  basic data standards for all
                                               interested researchers, and by establishing a com-
                                               mon  database,  accessible to all interested re-
                                               searchers, a Management Conference can encour-
                                               age  the development of a considerable body of
                                               scientific and technical  information with long-term
                                               potential utility for policy research and estuary man-

                                               There are a variety of new environmental manage-
                                               ment tools like the Green Bay Mass Balance Model
                                               which are being developed and assessed. Technical
                                               Advisory Committees need to monitorthese projects
                                               to identify those new  technologies that could make
                                               contributions to the local management program on
                                               two different levels:

                                                 the discovery of important new estuary manage-
                                                   ment "facts" that need to be incorporated in
                                                   planning and management strategies (e.g., hy-
                                                   drilla promotes the rapid restoration of many
                                                   estuarine areas1,); or

                                                 new models or simulations that can be adapted
                                                   at low cost to the management needs of the local
                                              For further information fen the Green Bay Mass Balance
                                              Study, contact the Great Lakes National Program Office
                                              (312/353-3503) or the 'Office of Marine and Estuarine
                                              Protection, Technical Sijpport Division (202/475-7102).