TOXIC  SUBSTANCES IN THE CHESAPEAKE BAY ESTUARY


                              OWEN P. BRICKER*


                       ENVIRONMENTAL PROTECTION AGENCY


                            CHESAPEAKE BAY PROGRAM


                             ANNAPOLIS,  MARYLAND
                                  i




                                INTRODUCTION





    The Chesapeake Bay"i~s "a "geologically young estuarine system, born less


than 10,000 years ago when the Atlantic Ocean, rising in response to  •  •>
                                                                   r

meltwaters from receding Pleistocene glaciers, began to flood the valleys


of the rivers draining the east coast of the'. North American continent. ' By


approximately"3,000 years ago, ?tidal waters were beginning to encroach on


the present mouth of the Susquehanna'River at Havre de Grace, and the
                                *

estuarine geometry was probably quite similar to that which we observe

        <          t > . ,       *           ""                       '
today.  The flooding process did not -stop then,  but the rate of sea level

                                   ' ''r      '-"    '  '
rise decreased.  Even to'day, the flooding continues at approximately 1.6


mm/yr. in the Chesapeake Bay area (Nichols,  1972).   This rate of sea level


rise is larger than the world-wide average and reflects a local tectonic


component in addition to that caused by the increase in volume of sea


waters from melting ice caps.


    Estuaries form a buffer zone between fresh water rivers and the sea.


They behave as very efficient sediment traps for particulate material


carried by the rivers  and by the inflow  of saline marine bottom waters


through their mouths.   The sediment  that accumulates in estuaries  is


commonly a mixture of  river bourne terrestial  debris derived from


*Current address:   United States Department  of the  Interior, Geological

 Survey, Water Resources Division, Reston, Va.  22092

-------
                                    - 2 -




weathering and erosion of the tributary watersheds and coastal marine




sediment derived from the continental shelf (Mead, 1969; Hathaway, 1972).




From a geologic perspective, estuaries are very ephemeral features, quickly




filling with sediment from these sources.  The lifespan of an estuary is a




function of the rate of  change in sea level vs. the rate of accumulation of




sediment.  In  the Chesapeake Bay, the continuing rise of sea level




partially compensates for the rate of accumulation of sediments and the net




"effect  is a prolongation cTf "the~ lifespan of the system.  The estuary,




however, is a  dynamic system, undergoing continuous evolutionary changes




which will ultimately lead to its destruction  through infilling with




sediment.




    The Chesapeake  Bay began to experience impacts, in addition to those




caused by natural processes, from the time of  first European settlement




along its shores.   Clearing of land for agriculture and development has




greatly accelerated the  rate of erosion in the adjacent land areas and




 increased the  amount of  sediment delivered to  the estuary by its tributary




rivers.  Perhaps an even more serious impact is related to the tremendous




 technological  advances  that have been made through the years.  Man has been




 exceedingly  ingenious in synthesizing and producing a miriad of new




 chemical  compounds, and  in  finding uses  for an increasing variety of metals




 and, more recently, radionuclides.  These substances enter the environment




 through waste  discharges and other disposal practices,  (e.g., industrial




 discharges,  sewage  effluents, land fills), by  direct applications for




 specific  purposes  (e.g., herbicides,  pesticides,  fertilizers) and via




 atmospheric  pathways (e.g., automotive  exhausts,  combustion of oil, coal




 and wood,  incineration  of refuse,  fugitive dusts  from storage or disposal




 sites,  bomb  testing).   It is now clear  that many  of the substances that




were either  purposely or inadvertently  released to the environment are

-------
                                    - 3 -




displaying unanticipated adverse affects on the biosphere.   Historically,




estuaries have been favored localities for siting industries, power plants




and sewage treatment facilities.  They provide an abundant  supply of water




for industrial processes and for cooling power plants, they are a




convenient conduit for the disposal of a broad spectrum of  wastes, and they




provide direct accessibility to marine transportation of raw materials and




finished products.  As a consequence, estuaries have bourne the brunt of




man's activities." The"Chesapeake Bay is no exception.




    Two classes of materials, toxic substances and sediment, pose the




greatest threat to the environmental well being of.the estuarine system.




These materials are intimately related in that many toxic substances,




inorganic and organic, associate strongly with sediment via




physico-chemical mechanisms.  As a consequence, the sediment accumulating




on the bottom is the largest reservoir of toxic materials in the estuary




(Bricker and Troup, 1975).




                                  Sediments




    The sediments that accumulate in Chesapeake Bay are important for a




number of reasons.  From a physical standpoint, sediments tend to fill in




channels and harbours and thus create a need for periodic dredging in order




to maintain these facilities for their intended purpose.  Dredging, in




turn, requires disposal sites for placement of the material removed.




Appropriate handling techniques and disposal site characteristics depend




upon  the chemical components and physical properties of the spoil.




Suspended sediment creates turbidity which decreases the depth of light




penetration and may also affect its spectral distribution.   The decrease in




intensity and shift in spectral qualities may adversely affect aquatic




plants.  Large concentrations of suspended sediment tend to clog the gills

-------
                                    - 4 -



and  filtering apparatus of filter feeders causing impairment or death.




Rapid  sedimentation may cause burial and smothering of benthic fauna and




flora.




     In the  absence of sediments, however, the estuary would not be the




fertile and productive environment  that it is.  Sediments form a substrate




upon which  rooted aquatic plants grow; they provide a habitat for burrowing




benthic organisms; they are  a source of nutrients for benthic flora and




fauna.  Sediments also carry with them metals derived from natural




weathering  and  erosional processes  and those introduced by man.  Many of




these  metals are essential to maintain a healthy biota, 4>ut if present in




excess are  toxic.  In addition, sediments are a vehicle for the transport




and localization of a large  number  of the anthropogenic organic compounds




that enter  the  aquatic environment  (Olsen, 1979).  Both inorganic and




organic toxic  substances have a great affinity for particulate matter of




small  size  and  large surface area.  Sites of accumulation of sediments




possessing  these physical characteristics usually contain significantly




higher concentration of metals and  organic compounds than sites of




accumulation of sediments of sand size or larger.  Sediments thus play a




major  role  in  the  transport  and distribution of toxic materials in the




 estuary.




     No systematic  study of toxic materials in the Chesapeake Bay had been




attempted until the Environmental Protection Agency Chesapeake Bay Program




•was initiated  in 1975.  In planning that program, it was concluded that any




 toxic  substances discharged  into  the Bay and its tributaries could have




 direct impact  during  their residence time dissolved in  the water, however,




because of  the  rapid water movement and concomitant dilution, these effects




would  be short  lived.  The most serious potential problems were identified




 as those associated with  toxic substances that accumulate in the sediment




 and/or biota.   These  substances have a much longer residence time in the

-------
                                    - 5 -




system and may also build up to very high concentrations  through sediment




sorption mechanisms or bioaccumulation.  For these reasons,  knowledge of




the distribution, amount, and physical characteristics  of the recent




sediments in the Bay is fundamental to understanding the  behavior and fate




of toxic substances in the estuary.  In addition to the physical




characteristics, the content of organic carbon and sulphur play an




important role in determining the oxidation/reduction state of the




sediments after deposition.  The water content correlates with the




stability and ease of resuspension of the bottom and with the rate at which




dissolved substances diffuse through the sediment.  The mineralogy of the




sediment provides information on the reactivity of the inorganic




particulate constituents.  These parameters together form the framework




into which the chemical and biological pieces of the system fit.




    The most basic data concerning sediments in the estuary are:




    1.  location in the system




    2.  morphology of deposits




    3.  physical characteristics




    4.  rate of addition to the system




    5.  sources




    6.  sites and rates of present accumulation




    In Chesapeake Bay, geophysical methods have been used to examine the




thickness and morphology of the bottom sediment (Maryland Geological




Survey, Virginia Institute of Marine Science open file reports).  These




methods also provide information on some other sediment properties in that




sand and shell layers can be differentiated from finer silty and muddy




sediments.




    The physical characteristics of the surface sediments (particle size

-------
                                    - 6  -




distribution, water content) have been determined for the entire Bay;  on a




1 km grid in Maryland waters and on a 1.4  km grid in Virginia waters.   In




addition, these same properties have been  determined on a selected suite of




meter length cores collected between the Susquehanna River and the Virginia




capes.  Sediment, on the basis of particle size,  displays a relatively




systematic distribution pattern with sand  occurring in the shallow




shoreline areas and mud in the deeper mid-Bay regions.  Between, there




occurs a zone of mixing "of"these"two sediment types (Byrne, 1980; Kerhin,




1980).  This sediment work provides a description of the state of the




system relative to sediments at the present time in history and it will




serve as a valuable baseline against which future changes can be measured.




    Three major sources contribute sediment to Chesapeake Bay; tributary




rivers, shoreline erosion and marine inflow.  The northern part of the Bay




is dominated by sediment carried via the Susquehanna River; the southern




Bay, by sediments transported by inflowing coastal marine waters; and  the




mid-Bay region, by sediments derived from  shoreline erosion.




    Each of  the tributary rivers, with exception of the Susquehanna, is




characterized by an estuarine segment in its lower reaches.  A large part




of the sedimenf carried by these rivers is trapped in their lower estuarine




portions and never reaches the main Bay.  As a consequence, infilling  of




the middle portion of the Bay is occurring at a slower rate than to the




north or the south, with fine particle size sediment that escapes the




tributary estuaries collecting in the deeper areas and coarse sediment




derived from shoreline erosion accumulating in the shallow waters adjacent




to the shorelines.  The Susquehanna River  debouches directly into the  upper




Bay and the bulk of the sediment it carries is deposited there.  Sediments




from the continental shelf, carried into the Bay in the saline bottom




waters, dominate the southern segment of the Chesapeake Bay.

-------
                                    - 7 -
    It is important to know what changes have occurred in the system in the
past so that predictions can be made concerning future trends.  In order to
understand how  the system has changed from past to present, and to identify
•impacts related to man's activities, we must rely on information recorded
in  the sediment.  To interpret this record, we must first know the time
interval represented by the record.  Three independent methods for
deciphering the time (rate) of sedimentation have been employed in the
.Chesapeake Bay:  .._!.)..comparison ofhistorical bathymetric charts, 2) pollen
                          710
biostratigraphy,  and 3) Pb    geochronology.  Parts of the Bay have been
surveyed bathytnetrically at irregular time intervals beginning in 1846.
Where  these surveys overlap, the change in depth represents the amount of 	
deposition  (or  erosion) that has occurred during the time between surveys
(Maryland Geological Survey, Virginia Institute of Marine Science, open
file reports).   A second technique  is based on pollen biostratigraphy, that
is, the  identification of specific  time horizons in the sediment recognized
by  pollen distribution.  For instance, the time of disappearance of
American chestnut in the 1930's, in response to the chestnut blight, is
recorded by the absence of chestnut pollen in sediments deposited after
that  time.  Other identifiable horizons, both older and younger, have been
recognized in Chesapeake Bay sediments and are valuable time markers in
this system (Brush, 1980).  A third technique employs the decay of a
                                210                   238
radioactive isotope of lead.  Pb    , a member of the U    series, is
continuously being added to the earth's surface environment.  It adsorbs
strongly onto sediment particles and is deposited with them wherever they
accumulate.  Once buried beneath the sediment-water interface, no
             210
additional Pb     can be added, and  that contained in the sediment

-------
                                    - 8 -


continues to decay at a constant rate (half life =  22.5  years).   This


permits the dating of sediments back to approximately  100-125  years  B.P.

 A?
(5 x half life) (Setlock and Helz, 1980).  Each of  these methods provides


an estimate of the rate at which sediment has accumulated at the site


sampled.  In areas of the Bay where sedimentation rates  have been


determined by either two or all three of the above  techniques, the


correspondence is usually quite good.  Using this information the age  of a


particular layer or bed-of-sediraent can-be dated by its  depth beneath  the


surface.  If a change in the concentration of any toxic  substance is


observed as a function of depth, the rate of loading of  that substance can


be inferred and projections made about future concentration trends.  The


time of  introduction of various substances into the system can also be


documented.  Data about sedimentation rates are directy  useful in planning


dredge disposal sites, locating channels to provide minimum maintenance,


and estimating the frequency and volumes of material that will have to be


dredged  in order to maintain harbours and channels  in various parts of the


system.


                               Toxic Substances


    Along with knowledge of the distribution and physical characteristics


of bottom sediments in the estuary, it is necessary to know the


concentrations of the toxic substances they contain if these materials are


to be effectively managed.


    Two major classes of toxic materials are particularly important to the


estuarine environment; metals and anthropogenic organic  compounds.  Metals


are derived from natural weathering and erosion of  the metalliferous


Piedmont rocks underlying the watersheds of many of the  Bay tributaries,


and from man's activities.  Most of the organic compounds of environmental


concern are strictly the product of man's chemical  ingenuity.  These sub-

-------
                                    _ 9 -




stances enter the system via direct discharges,  in input from the




tributaries, in non point source runoff,  and through atmospheric pathways.




The distribution of these materials in surface sediments (upper few




centimeters) is a result of recent deposition and accumulation in the




estuary.  Dated cores provide information on how the concentrations of




these materials have changed with time in the sediment.   Because metal




behavior is better understood and analytical methods for metals are more




straightforward and less expensive than"those for organic compounds,  the




data for metals in the estuarine environment is  much more detailed than




that for organic compounds.  Emerging evidence over the  past decade




suggests, however, that synthetic organic compounds may  be of greater




concern than metals from the standpoint of environmental degradation of




aquatic systems.




    The similarity in behavior between metals and many organic pollutants




with respect to sorption behavior on fine particle size  sediment suggest




that metals may be used as surrogates for predicting the transport and




accumulation of many organic pollutants.   A limited number of samples of




surface sediment from the main stem of the Chesapeake Bay have been




analyzed for organic compounds using glass capillary gas chromatography/




mass spectrometry and corroborate this hypothesis.   Preliminary inspection




of both the metals data and the organics  data show that  the highest




concentrations of these substances occur  in samples from tributary mouths,




suggesting that the tributaries act as sources of these  materials  to  the




main Bay (Huggett, 1980).  Not surprisingly, the highest concentrations




were observed at the mouths of the Susquehanna,  Patapsco, and James Rivers.




    The technical complexity and expense  of analyzing estuarine samples for




organic compounds led to the development  of a strategy for maximizing the

-------
                                   - 10 -



output of data of the type that would be most useful  to identify  potential




problems with these compounds.   Instead of trying  to  identify  each  peak




(compound) on GC/MS traces, the complete GC/MS output from each sample  is




stored on the computer.  Subsequent sampling at the same localities using




the same analytical procedures  disclose changes in peak height



(concentration) for the organic compounds.  If there  has been  a significant



increase in any peak from one sampling  period to the  next, the compound




represented by that peak-can be-identified and evaluated with  respect to




its toxicity and potential impact on the system.  Possible sources  of the




compound can be identified by concentration gradients provided by a more




detailed sampling grid in that particular  area of  the Bay, and appropriate




regulatory measure instituted.   The chances of associating a particular



compound with its source are increased  by  performing  identical analytical




work on industrial, municipal sewage treatment plant  and power plant




discharges into the Bay (Monsanto Research Corporation, 1980). By



periodically analyzing effluent discharges, it may be possible to stop  a




potential toxic problem at a very early stage before  the substance  has  been




discharged into the environment in large quantities.   The frequency of



sampling, however, must be appropriate  to correspond  to changes in  process




or treatment in the plants.  One serious drawback is  that the  direct




discharge analysis may not detect some  toxic substances present in  very
                   v.


small concentrations, yet if these substances are strongly sorbed by




sediment or bioaccumulated by organisms, they may build up to  dangerously




high levels in the environment.  By emphasizing the sediment and  biota




sampling in the estuary, and supplementing this with  periodic  sampling  of




effluent discharges, it may be possible to manage toxic substances  from




point sources in a much more effective  manner than is presently being done.

-------
                                   - 11 -




An up-to-date inventory of raw materials,  processes and finished products




from all dischargers into the estuary would aid greatly in assessing the




loading of toxic materials in the Bay system.




    Coupling the data on toxic subtances  in the sediment with  the




compositions and volumes of industrial  discharges  and the type of inventory




data described above, it will be possible  to identify those substances  that




accumulate in the environment and permit  estimates of mass-balance budgets




for specific toxic sub's tarices" of "concern.   Combining this information with




the distribution and physical characteristics  of the sediment  will disclose




specific toxic substance-sediment associations.  Extending this type of




work to dated core samples will provide estimates  of changes in loading of




toxic substances with time.




    Perhaps as important as knowledge of  the identities and spatial




distribution of toxic substances in the estuary is an understanding of  how




these substances behave in the environment. After deposition  and burial in




the bottom, sediments and associated  toxic substances are exposed to an




anoxic reducing environment.  This leads  to changes in speciation,




desorption, dissolution and remobilization of  many elements (Elderfield and




Hepworth, 1975).  Three major mechanisms  lead to the re-introduction of




these materials at the sediment surface and to the water column:  1)




transport in the dissolved state in the interstitial water via diffusion




and/or advection, 2) physical transport of sediment and interstitial water




by benthic infauna (bioturbation, irrigation,  ventilation), and 3) physical




disturbance of the sediment by storms and  by man's activities  (dredging,




propeller wash, etc.).  Investigation of  the metal and organic content  of




the sediment areally and with depth provides information which permits




prediction of the chemical impacts of re-exposure  of sediments at the




surface.  Sampling and analysis of interstitial  waters provides a data  base

-------
                                   - 12 -




from which flux of metals and nutrients  into the water  column can be




calculated.  Available data disclose that  the sediment  behaves as an




important source of nutrients to the estuary (Maryland  Geological Survey,




open file reports).  At certain times of the year,  a significant flux of




dissolved manganese and iron into the deep bottom waters  is  also observed.




Data for other metals is not yet available.  In addition  to  nutrient and




metals flux calculations, the interstitial water chemistry provides




critical information on the reactions that occur within the  sediment and




the composition of the aqueous environment in which the benthic infauna




live.




    Examination of the benthic fauna, particularly the  infauna, is ~




providing a picture of the distribution of organisms in the  estuary as a




function of salinity, sediment type, and depth beneath  the sediment-water




interface (Maryland Geological Survey, Virginia Institute of Marine




Science, open file reports).  These studies document the  effects of the




benthic communities on the disturbance and mixing of the  sediment




(bioturbation), the stabilization-destabilization of the  bottom sediments




relative to erosion and resuspension, and the role of burrows and other




biogenic structures on physical and-chemical processes  occurring in the




sediments.  Benthic organisms are restricted in their mobility and




therefore must adapt  to any changes that occur in the local environment.




For  this reason, benthic organisms may be good early warning indicators of




environmental degradation.  Investigations in the main Bay have disclosed




cycles of colonization and extermination of benthic fauna in the deep




trough along the Eastern Shore, apparently in response  to the yearly summer




development of anoxia in the bottom waters (Reinharz and  Diaz, 1980).




Systematic examination of benthic communities Baywide,  and particularly in




the  tributaries, may  identify areas subject to environmental stress.  These

-------
                                   - 13 -

areas would be prime targets for  detailed  investigations  of  the  causes  of

the stress.  The response of organisms;  distribution,  abundance,  species

diversity, histopathologic features,  genetic effects  and  other biologic

effects could be used as indicators  of  the state of health of  the

particular segment of the system  in  which  the organisms live.  The

foundation for developing an assessment  strategy based on biologic  criteria

is a thorough description of the  estuarine benthic organism  communities in"

conjunction with the physical and chemical characteristics of  the

environment in which they live.

                Present  Status of Toxics in  the Chesapeake Bay

    The past decade has  witnessed disturbing changes  in the  ecosystem of

the Chesapeake Bay.  Among the more  widely publicized  of  these have been

the decline and virtual  disappearance of rooted  aquatic plants from much  of

the Bay, the steady decrease in the  abundance of striped  bass and oysters,

the cessation of the spring shad  runs in the upper Bay, poor yields of

clams and fluctuating, but generally  declining catches of crabs.

Individually, any one of these could  be  attributed to  a biological  cycle  or

some other natural phenomenon. Taken together,  however,  the implications

are more ominous.  It has been strongly  suggested that toxic substances are

responsible for the observed changes.  Over the  years, however,  the Bay has

been under increasing pressures  from a variety of man's activities. The

harvesting of shellfish and finfish  by  commercial watermen and sports

fishermen has not been effectively regulated from the standpoint of

preserving the resource.  An expanding  population on  the  shores  of  the  Bay

and in  the watersheds of the Bay  tributaries, has tremendously increased

the volume of sewage effluent delivered  to the estuary.   Increasing need
                    <•
for energy has led to the siting  of  conventional and  nuclear power  plants

on the  shores of the Bay and along its  tributary rivers.  Continued indus-

-------
                                   - 14 -




trial development in the Bay area has burdened the estuary with increased




volumes of chemically complex discharges.   Clearing land for agriculture




and for development has greatly increased  the loads of suspended sediment




carried to the estuary.  Chemicals in runoff from agricultural areas and in




storm drainage from city streets, parking  lots and highways ultimately end




up in the Bay.  Only recently has it been  recognized that many toxic




substances, including metals and organic compounds, are transported




atmospherically and enter ~the~ surface environment via precipitation and by




dry fallout.  The sources of these pollutants are often far removed from




where they impact the earth's surface.  Each of these insults takes its




toll on the finite assimilative capacity and resiliance of the estuarine




environment.  Cumulatively, they appear to have reached the stage at which




they exceed the regenerative capacity of certain parts of the resource.  In




turn, this has led to the decline and/or disappearance of some of the more




sensitive biota.




    What can be done to halt the degradation and reverse these trends?  The




tendency in the past has been to look for  a single cause of the problem,




such as toxic substances or excess nutrients and, thus far, the search has




been less than successful.  The estuarine  sys.tem is very complex and each




of the diverse activities mentioned1above  has an impact on the system; some




greater than others.  We observe the net integrated effect of all of these




factors acting in concert, and it is thus  not surprising that no simple




answers have been found.  Only two areas of the Bay, the Elizabeth River




and Baltimore Harbor, show serious environmental degradation that can be




directly attributed to toxic substances (Villa and Johnson, 1974; Johnson




and Villa 1976; Chu-fa Tsai et al, 1979).   Even in these localities it is

-------
                                   -  15 -




not possible, at present, to identify the specific effects of individual




toxic elements or compounds.  Over most of the Bay the effects are much




more subtle and no direct cause and effect relationships have yet been




demonstrated.




    Effective management of toxic substances in the estuarine environment




requires regulation of the amount of each toxic substance delivered to the




system from all sources in order to keep environmental concentrations below




the level at which adverse—impacts occur.  This regulation must be based on




a firm understanding of the behavior and fate of natural and anthropogenic




toxic substances introduced into the system; the effects of these toxic




substances on estuarine biota; the identification of the sources




contributing toxic substances; and quantification of the load of each




substance delivered by each source.  At the present time, there is no




comprehensive inventory of loadings to the system and there is only




fragmentary information concerning the types and concentrations of toxic




substances already in the environment.  There is a moderate body of




information relative to the behavior and fate of metals in the estuarine




environment; however, similar information about toxic organic compounds is




difficult or impossible to-find.  Perhaps the largest gap is in our




understanding of the effects of toxic substances, both metals and organic




compounds, on the estuarine biota.




    The Environmental Protection Agency Chesapeake Bay Program has




initiated a research effort to begin to address these questions; however,




this research must be intensified and expanded if it is to provide the data




necessary to develop an effective program for the management of toxic




substances in the estuarine environment.

-------
                                 REFERENCES

BRICKER, O.P., TROUP, B.N. (1975)  Sediment-water  exchange  in Chesapeake  Bay.
   In Estuarine Research, Croniri,  L.E.,  ed,  Academic Press, N.Y.,  1,  3-27

BRUSH, G. (1980) Report on Pollen  Biostratigraphy to EPA/Chesapeake Bay
   Program

BYRNE, R. (1980) Report on Sediment Distribution  in Virginia Waters to EPA/
   Chesapeake Bay Program

CHU-FA TSAI, Welch, J., KWEI-YANG  CHANG, SHAEFFER, J.,  CRONIN,  L.E.,  (1979)
   Bioassay of Baltimore Harbor Sediments/   Estuaries 2_, 141 -  153.

ELDERFIELD, H., HEPWORTH, A. (1975) Diagenesis, Metals  and Pollution  in
   Estuaries.  Marine Pollutions Bull.  6,  85 - 87.

HATHAWAY, J.C., 1972, Regional Clay-Mineral Facies in  the  Estuaries and
   Continental Margin of the United States  East Coast,  in  Nelson,  B.W.,  ed.,
   Symposium on estuaries:  Geol;  Soc. Am.  Mem. 133, p  293 - 316.

HUGGETT, R. (1980) Report on Organic Compounds to EPA/Chesapeake Bay
   Program.

JOHNSON, P.G., VILLA, 0. (1976) Distribution of Metals  in  Elizabeth River
   Sediments.  EPA Technical Report No.  61, Annapolis Field Office

KERHIN, R. (1980) Report on Sediment Distribution in Maryland Waters  to
   EPA/Chesapeake Bay Program.

MGS - MARYLAND GEOLOGICAL SURVEY Open file  reports on Chesapeake Bay.

MEADE, R.H. (1969) Landward Transport of Bottom Sediments  in Estuaries of
   the Atlantic Coastal Plain.  Jour. Sed.  Ret. 39, 224 -  234.

MONSANTO RESEARCH CORPORATION (1980) Report on Industrial  Effluents  to
   EPA/Chesapeake Bay Program.

NICHOLS, M.N. (1972) Sediments of the James River Estuary, Virginia.  In
   Nelson, B.W., ed, Symposium on estuaries:  Geol. Soc. Am. Mem.  133,
   p  169 - 212.

OLSEN, C.R. (1979) Radionuclides,  Sedimentation and the Accumulation  of
   Pollutants in the Hudson Estuary.  Ph.D. thesis, Columbia University,
   N.Y., 343 pp.

REINHARZ, E., DIAZ, R. (1980) Report on Benthic Fauna  to EPAAChesapeake
   Bay Program.

SETLOCK, G.; HELZ, G. (1980) Report on Pb210 Dating of  Sediment to EPA/
   Chesapeake Bay Program.

VILLA, 0., JOHNSON, P.G. (1974) Distribution of Metals  in  Baltimore Harbor
   Sediments.  EPA Tech. Rept. No. 59, Annapolis  Field  Office.

VIMS  - VIRGINIA INSTITUTE OF MARINE SCIENCE open  file  reports on Chesapeake
   Bay.

-------