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Lake Michigan Mass Balance
LAKE MICHIGAN MASS BUDGET/
MASS BALANCE WORK PLAN
U.S. Environmental Protection Agency
Great Lakes National Program Office
(EPA-905-R-97-018, 1997, 155 pp.)
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INPUTS:
Appendix 1. List of Workshop Participants
Appendix 2. Parameters and Measurements Proposed for
EMP
Appendix 3. Atmospheric Loading Calculations
Appendix 4. Number of Biology Samples for Collection
and Analysis
Appendix 5. Format for Reporting Analytical Results
Appendix 6. Modeling Requirements and Studies
Appendix 7.Sampling Locations
Figure 1. Overall Mass Balance Model Design
Figure 2. Schematic of Contaminant Transport and Fate
Model
Figure 3. Simplified Lake Michigan Lake Trout Food Web
Figure 4. Spatial Segmentation of Mass Balance Model
Figure 5. Tributary Sampling Locations for Loading
Estimates
Figure 6. Land-based and Intensive Atmospheric
Sampling Locations
Figure 7. Sediment and Sediment Trap Sampling Location
Figure 8. Open-Lake Sampling Station Locations
Figure 9. Lake Michigan Sampling Locations-Biota
Table 1. Contaminant Transport and Fate Model Linkages
Table 2. Tributaries to be Monitored for Loadings
Table 3 Estimated sample volumes, sample sizes and
sampling frequency
Table 4. Atmospheric Monitoring Sites and Sampling
Frequency
Table 5. Atmospheric Monitoring Sampling Frequency
Table 6. Sensor Array Information
Table 7. Variables to be Measured
Table 8. Biology Data Requirements
Table 9. Biology Measurements and Data Groups
This study builds upon the Green Bay Mass Balance Study for toxic contaminants. That
is, this study utilizes, as much as possible, the monitoring and modeling approaches and
technology developed during the Green Bay Mass Balance Study. The Green Bay Mass
Balance Study was supported by a large number of researchers, academic as well as
governmental, and was termed an "unqualified success" by the portion of the
scientific
community involved in its review. Among their recommendations was that the approach
now be attempted on a larger scale, namely one of the Great Lakes. For several reasons
which will be elaborated in the text, we have chosen Lake Michigan.
Scientists from many state and federal agencies contributed to this workplan during and
subsequent to a workshop held September 16 and 17, 1993. These scientists
represented: the Illinois Department of Conservation, Indiana Department of Environmental
Management, Michigan Department of Natural Resources, Wisconsin Department of
Natural Resources, National Oceanic and Atmospheric Administration, U.S. Fish and
Wildlife Service, U.S. Geological Survey, and several groups within the U.S. Environmental
Protection Agency. We gratefully acknowledge the time and effort of the participants in
the
Workshop (see Appendix 1).
This document is the Workplan for conducting a Mass Balance Study for selected toxic
contaminants in Lake Michigan. The mass balance effort is a part of the "Lake
Michigan
Enhanced Monitoring Program", which includes tributary and atmospheric load
monitoring,
source inventories, and fate and effects evaluations. We describe elements necessary to
conduct a Mass Balance Study based upon the efforts of many Federal and State
scientists and staff (see Appendix 1 for
Participants) who participated in the initial planning
workshop, as well as descriptions of components of the work modified from documents
provided by principal investigators. The initial draft of the Plan was developed by
Messrs.
David DeVault of the EPA Great Lakes National Program Office (GLNPO) and Alan
Hoffman of AREAL.
This Mass Balance Workplan, part of a larger enhanced monitoring program for Lake
Michigan, results from the convergence of a number of activities which address reductions
in the release of toxic substances, particularly persistent, bioaccumulative substances,
to
the Great Lakes system. These activities provide information necessary for
implementation of a Lakewide Management Plan (LaMP) for Lake Michigan. Development
of LaMPs for all five of the Great Lakes were agreed to by the U.S. and Canada under the
1987 amendments to the Great Lakes Water Quality Agreement (GLWQA). The Lake
Michigan LaMP has been developed by U.S. entities since the lake lies entirely within the
boundaries of this country. Section 118 of the Clean Water Act (CWA) mandated its
development and established deadlines regarding its completion. An example of the type
of the activity supporting the LaMP is a study for the Great Waters Program mandated by
Title III, Section 112(m) of the 1992 Clean Air Act Amendments (CAAA). The primary goal
of this enhanced monitoring program is to develop a sound, scientific base of information
to guide future toxic load reduction efforts at the Federal, State, Tribal, and local
levels. In
particular, the following specific objectives have been identified through various forums:
- to identify relative loading rates of critical pollutants from major tributaries to the
Lake Michigan basin in order to better target future load reduction efforts;
- to evaluate relative loading rates by media (tributaries, atmospheric deposition,
contaminated sediments) in order to better target future load reduction efforts and to
establish a baseline loading estimate to gauge future progress;
- to develop the predictive ability to determine the environmental benefits of
specific load reduction scenarios for toxic substances and the time required
to realize those benefits. This includes evaluation of benefits of load
reductions from existing environmental statutes and regulations as required
under Section 112(m) of the CAA, and Section 303 of the Clean Water Act
(CWA), and;
- to improve our understanding of key environmental processes which govern the
cycling and bioavailability of contaminants within relatively closed
ecosystems.
The Lake Michigan LaMP assesses the status of the Lake Michigan watershed
and
identifies pollutants impacting the system on a lakewide scale. The goal of the LaMP is to
restore and protect beneficial uses (as defined by the GLWQA) of the Lake by prioritizing
prevention, reduction, and remediation activities. By developing the predictive ability to
determine the environmental benefits of specific load reduction options, the mass balance
will allow Federal, State, and Tribal agencies to make more informed load reduction
decisions.
USEPA intends the Lake Michigan LaMP to serve as the basis for development and
submission of State Water Quality Management Plans (WQMPs) developed in accordance
with Sections 208 and 303(b) of the CWA, as implemented through the requirements of 40
CFR 130.6. These WQMPs establish a process for continuous water quality planning which
focuses on priority issues and geographic areas, and on the development of water quality
controls leading to implementation measures. USEPA expects any new loadings data
obtained during the development of LaMPs to be incorporated by the States when
establishing or revising Total Maximum Daily Loads (TMDLs) and Wasteload Allocations
(WLAs) for waters of the Great Lakes system. These new TMDLs and WLAs will then be
appropriately reflected in subsequent revisions to NPDES permits. In this way, USEPA and
the States will ensure reasonable progress in the overall improvement of the Great Lakes
water quality and attainment of beneficial uses and water quality standards.
Pursuant to the Great Lakes Critical Programs Act of 1990 (GLCPA), USEPA published
final Water Quality Guidance for the Great Lakes System (58 Federal Register 20802).
The Guidance consists fo water quality criteria for 29 pollutants to protect aquatic life,
wildlife, and human health, and detailed methodologies to develop criteria for additional
pollutants; implementation procedures to develop more consistent, enforceable
water-quality-based effluent limits in discharge permits, as well as total maximum daily
loads of pollutants that can be allowed to reach the Lakes and their tributaries from all
sources; and antidegradation policies and procedures. A key part the Guidance is the
extensive documentation in support of the selection of 29 toxic pollutants for special
focus.
Included in the 29 contaminants are PCBs, chlordane, and mercury, three of the
substances for which we will develop mass balances.
The water quality criteria and values proposed in the Guidance apply to all the ambient
waters of the Great Lakes System, regardless of the source of pollutants to those waters.
In this manner, the proposed water quality criteria and values provide the basis for
integrating actions carried out under the range of environmental programs available to
both
Federal, State and Tribal regulators to protect and restore the Great Lakes ecosystem. The
mass balance approach will facilitate this integration by evaluating multi-media load
reduction actions required to ensure that Lake Michigan water quality meets the water
quality criteria and values established in the final Guidance.
The CAAA specifically require EPA and NOAA to, among other things:
- Conduct atmospheric monitoring for Hazardous Air Pollutants (HAPs)
- Conduct research on monitoring methods
- Determine the relative contribution of air deposition to total loadings
- Evaluate the adverse effects from deposition, including the direct effect to health and
the environment
- Assess the contribution of such deposition to violations of water quality standards
- Conduct biological sampling to identify the presence of HAPs that deposit from the air.
It is not possible, given the current state of the science and available resources, to
meet
these requirements or the specific objectives stated above, through a "brute
force"
monitoring approach. The CAAA and CWA requirements will best be met through a
coordinated effort to quantify and understand the loadings, transport and fate of selected
HAPs (hazardous air pollutants/contaminants) in a defined ecosystem and then transferring
that knowledge to other ecosystems. A Mass Balance approach will allow the above
requirements to be met in the most cost effective manner.
In a mass balance approach, the law of conservation of mass is applied in the evaluation
of
the sources, transport and fate of contaminants. This allows prioritization and allocation
of
research, remedial and regulatory actions for water quality management. The approach
requires that the quantities of contaminants entering the system, less quantities stored
or
transformed within the system, must equal the quantities leaving the system. Once a mass
budget for selected contaminants has been established and a mass balance model
calibrated, additional contaminants can be modeled with limited data.
A mass balance study for hydrophobic organics was piloted on Green Bay, WI in
1988-1992 by USEPA and the Wisconsin Department of Natural Resources. The
monitoring, analytical and modeling tools required by this approach on a whole lake basis
were developed during the Green Bay Study. These techniques may now be applied to the
Great Lakes, Lake Champlain and coastal estuaries. Lake Michigan will be the first full
scale
application and will serve as the basis of any future mass balance efforts.
A mass budget and mass balance model will be constructed for a limited group of
hazardous air pollutants (HAPs)/contaminants which are present in Lake Michigan at
concentrations which pose a risk to aquatic and terrestrial organisms (including humans)
within the ecosystem, or which may accumulate to problematic concentrations in the future.
The chemicals chosen cover a wide range of chemical and physical properties and are
representative of other classes of compounds which pose current or potential problems.
This approach will allow other chemicals to be modeled with limited data. The chemicals
selected are:
- PCB congeners
- Trans-nonachlor
- Atrazine and major breakdown products
(de-ethyl atrazine, de-isopropylatrazine)
- Total Mercury
PCBs are present in some Lake Michigan fish species at concentrations which exceed US
Food and Drug Administration tolerances, and have resulted in closure of commercial
fisheries and the issuing of consumption advisories for sports fishermen. They also
contribute to fish and wildlife reproductive problems and deformities (Mac 1988,
Gilbertson
1988). PCB congeners cover a wide range of physical and chemical properties, are
relatively resistant to degradation, and are ubiquitous. These properties make them ideal
surrogates for a wide range of organic compounds from anthropogenic sources
(Eisenreich 1987).
Trans-nonachlor is the most bioaccumulative of the chlordanes present in fish at
concentrations which exceed human health guidelines. As a technical chlordane
constituent, it is also one of the chemicals addressed by the Great Lakes Initiative.
Trans-nonachlor will serve as a model for the cyclodiene pesticides.
Unlike PCBs and trans-nonachlor, the manufacture and use of which have been
banned or
strictly controlled, atrazine is a commonly used herbicide in the Great Lakes basin and
elsewhere in the United States. It has been reported at elevated concentrations in Lake
Erie tributaries (Baker et al, 1988), in the open waters of the Great Lakes, and the
atmosphere over the lakes (Steven Eisenreich, personal communication 1990). It's
inclusion will provide a model for the more reactive, biodegradable compounds in current
use. The model will not include a food chain component since atrazine does not
bioaccumulate appreciably.
There is increasing concern about mercury in aquatic systems. It bioaccumulates, leading
to increasing tissue concentrations up the food chain. Evidence from inland lakes
indicates
a trend of increasing fish tissue concentration (Sorensen et al. 1990), and increases
through time in sediment cores. An understanding of the sources and fate of mercury and
its potential as a problem in the Great Lakes is in keeping with the specific objectives
of the
study. Current sampling and analysis of mercury, however, present difficulties that are
being addressed only at the research level. This is particularly true for analysis of the
several chemical forms in which mercury appears in the environment. The estimation of
transfer and process coefficients upon which much of mass balance modeling is based will
require considerably more research than is possible through this study. Sampling and
modeling, though less intensive than for organic contaminants, will provide new
information
on loads and fate of total mercury.
In addition, the Lake Michigan LaMP identifies each of these four contaminants as
impacting, or having the potential to impact, the Lake Michigan watershed. Developing a
mass balance for these substances will therefore assist the LaMP program by assessing
the expected environmental benefits of load reduction options.
Resource limitations, quality assurance requirements, and analytical and data handling
limitations preclude intensive monitoring and model calibration for more than the above
described target chemicals. While the mass balance modeling will focus on the above
parameters, determination of loadings and concentrations for other contaminants and
compounds useful for source apportionment and deposition modeling will be undertaken
as part of the Enhanced Monitoring Program (see
Appendix
2 for list of analytes). The
development of calibrated models will allow the listed CAAA requirements for other
HAPs/contaminants to be met with limited monitoring data and future resources to be
directed to other areas such as emission inventories and dispersion modeling.
Components of the mass balance model will be designed to predict contaminant
concentrations in the water column and target fish species over a 25 year period, relative
to
loadings from significant sources. Predictions of concentrations of HAPs in three species
of fish are desired as the final output from the models. The target fish species include:
lake trout (Salvelinus namaycush)
coho salmon (Oncorhynchus kisutch)
bloater chub (Coregonus hoyi)
These fish species represent a variety of life histories, food web dynamics, trophic
levels,
and contaminant exposure histories. Lake trout are native, top predators in Lake Michigan
(despite the lack of sustained reproductive success) with a life span of greater than 8
years. Their food web is complex, including to varying degrees bloater chub, rainbow smelt
(Osmerus mordax), alewife (Alosa pseudoharengus), slimy and deepwater
sculpins
(Cottus cognatus, Myoxocephalus thompsoni), benthic invertebrates (Diporeia
spp.) and
pelagic zooplankton (Mysis relicta), depending on life stage, season and geographic
location (Miller & Holey, 1992). Lake trout provide an important recreational and
commercial fishery. However, consumption advisories exist for certain size classes.
Coho salmon are non-indigenous, but are enjoyed by a vigorous sport fishery. They are
hatchery reared for approximately one year (varying by state from 5 months to 17 months),
live in Lake Michigan for two more years, then return to the tributaries to spawn and die.
Their diet is largely alewife.
Bloater chub have had historical importance in the commercial fishery, and are an
important
component of the lake trout diet. Young chubs feed on zooplankton, but older age classes
feed on benthic invertebrates (Diporeia spp.).
The calibration of the food web model(s) for these target species requires data on
contaminant concentrations and fluxes not only in these species, but also in the
supporting
trophic levels. The forage fish feed largely on benthic invertebrates and on zooplankton.
Alewife, in particular, feed heavily on pelagic Cladocera. At the base of the food webs
being modeled is the mixed assemblage of phytoplankton.
Fish-eating birds represent another trophic level in the Lake Michigan ecosystem that is
clearly impacted by toxic organic chemicals. However, the modeling of contaminant fluxes
through aquatic birds is beyond scope and available resources for this study. Similarly, a
clear understanding of the role of the microbial food web in the transport of organic
contaminants to higher trophic levels would be highly desirable, but it is beyond the
means
of this study to undertake the research. The mass balance model for Lake Michigan could
be modified or expanded at some future time to accommodate these other trophic levels
when the ecological relationships are more clearly understood.
The level of accuracy in a mass budget and model required to make sound environmental
management decisions is a subject of debate. For the Lake Michigan Mass Balance study,
we propose that model output should be within a factor of 2 of the observed concentrations
in the water column and target fish species. This level of accuracy is based on the likely
use of risk assessment in making management decisions. As risk assessment methods
are accurate, at best, to one order of magnitude, a factor of two, or one half order of
magnitude is sufficient. This will require a vertically and horizontally segmented water
quality
model coupled with a food chain model. The water quality model should be capable of
differentiating between the nearshore and open waters of the lake on a seasonal time
scale. The food chain model should be designed to predict peak contaminant
concentrations in multiple age classes of the targeted fish species. From the Green Bay
Mass Balance Study, it is estimated that the required level of model accuracy can be
achieved if loadings and contaminant mass in significant environmental compartments are
determined to within +/- 20 to 30 percent of the actual value.
Field data collection activities for the various parts of the Mass Balance Study are
described further in the following sections. However, a brief description of these
activities
will provide perspective on the scope of the study. Field data collection activities were
initially envisioned as a one year effort. However, it became evident early into the
project
that a longer collection period would be necessary to provide a full year of concurrent
information on contaminant loads and ambient concentrations for modeling purposes.
Therefore, field sampling will cover the period from April, 1994 through October, 1995.
Loading Information:
Tributaries - eleven Lake Michigan tributaries are being monitored intensively to
determine
the loads of the subject compounds to the lake. Sampling frequency varies from 12 to 45
samples per tributary in a year long period.
Atmosphere - nine sites are being monitored to determine atmospheric loads to Lake
Michigan. Additional field activities, part of the Great Waters Study, will provide data
to help
determine the net atmospheric load. Additional atmospheric samples are taken during
each Lake Guardian survey.
Sediment - one hundred and thirty-one sediment sampling sites will be visited, with the
majority in sediment depositional zones. Surface sediment segments from box core
samples will be analyzed for contaminants to determine the sediment contaminant inventory
(available for resuspension and contaminant release to the water column). Additional
studies will determine contaminants in sediment trap materials, and erodibility of
sediment
(resuspension).
Ambient Concentration Information:
Water - Five full (44 Station) and two abbreviated (15 Station) surveys will take place
over
the extended field season. In addition, a January, 1995 winter survey will visit 5
stations.
Samples for analysis of contaminants in water and water-borne particulates will be
collected
at each of the stations. In addition, water quality and biological information required
for
modeling purposes is collected at each station.
Upper Food Chain - The National Biological Service will collect fish during five surveys
over
the extended season. These will concentrate on the top predator fish (lake trout), and
also
forage fish which comprise the predators’ diet. Coho salmon are collected separately,
and
on a different schedule based on migratory patterns.
Lower Food Chain - As part of the seven lakewide surveys (see Water) samples of lower
food chain organisms will be collected for contaminant analysis. The lower food chain is
defined here as phytoplankton, zooplankton, Mysis relicta and Diporiea spp.
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