EPA Report Number
March, 1981
903R81008
SIGNIFICANCE OF SUSPENDED TRACE METALS
AND FLUID MUD IN CHESAPEAKE BAY
by
Maynard Nichols, Richard Harris, and Galen Thompson
Virginia Institute of Marine Science
School of Marine Science
College of William and Mary
Gloucester Point, Virginia 23062
and
Bruce Nelson
U.S. Environmental Protection Agency
TD Annapolis, Maryland 21401
225
.C54
S43
1981
.
University of Virginia ".- '"-;i,PA
Charlottesville , Virginia
Grant R806002-01-1
Duane Wilding, Project Manager
U.S. Environmental Protection Agency
Chesapeake Bay Program
2083 West Street - Suite 5G
Annapolis, Maryland 21401
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EPA Report Number
March, 1981
SIGNIFICANCE OF SUSPENDED TRACE METALS
AND FLUID MUD IN CHESAPEAKE BAY
by
Maynard Nichols, Richard Harris, and Galen Thompson
Virginia Institute of Marine Science
School of Marine Science
College of William and Mary
Gloucester Point, Virginia 23062
and
Bruce Nelson
University of Virginia
Charlottesville, Virginia
Grant R806002-01-1
Duane Wilding, Project Manager
U.S. Environmental Protection Agency
Chesapeake Bay Program
2083 West Street - Suite SG
Annapolis, Maryland 21401
U.S. Environmental Protection Agency
Annapolis, Maryland 21401
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DISCLAIMER
This report has been reviewed by the Chesapeake Bay Program,
U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products
constitute endorsement or recommendation for use.
11
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FOREWORD
Every year a substantial quantity of toxic substances enter
the drainage, water and floor of the Chesapeake Bay. The threat
of toxic metal contamination lies in the fact that regional pro-
duction is increasing with an increase in industrial activity and
an increase in sewage discharge. Reportedly, thousands of new
potentially toxic compounds are developed every year. Although
toxic effects and mortalities in the Bay environment have not been
demonstrated, disturbing changes have been observed over the past
decade, e.g. a decrease in abundance of striped bass and oysters,
a lack of shad runs in the upper Bay, the disappearance of grass
and declining crab and clam catches. Toxic effects may be subtle
and alter the Bay's ecosystem over long time periods. The signifi-
cance of the problem is evident in widespread and long-term Kepone
contamination of the James Estuary. By transfer to all components
of the environment and along the food chain, Kepone threatened the
health and seafood resources of man. Such accidents and continued
threats led to the Toxic Substances Control Act of 1976. To manage
toxics and protect the Bay requires an expanded knowledge of con-
centration levels, transport routes and reservoirs of potential
contaminates. This report aims to provide new data on the
occurrence and concentration of heavy metals for more effective
planning and use of the Bay.
111
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EXECUTIVE SUMMARY
This report aims to provide new information that meets
selected objectives of the EPA-States Toxics Plan of Action;
i.e. (1) to determine the state of the Bay with respect to the
distribution and concentration of selected metals in suspended
material and fluid mud; (2) to establish the temporal variations
of sediment and metal loading; (3) to identify potential zones
of metal accumulation and trace their transport routes, and
(4) to provide recommendations for monitoring and control of
contaminated sediment.
Field observations provide longitudinal coverage of the
Bay with transects into Baltimore Harbor and Hampton Roads.
They include contrasting conditions of seasonal high-low river
discharge and sediment influx, as well as neap-spring tide
range and oxygenated-anoxic water. Suspended material collected
on Nuclepore filters, was analyzed by flame AA for Fe, Mn and
Zn and by flameless AA for As, Cd, Cu, Hg, Ni, Pb and Sn.
Laboratory procedures followed EPA quality control standards
using USGS Standards. The survey occupied 122 stations,
accomplished 5,576 measurements including 633 analyses of
6 to 11 metals in suspended material and fluid mud.
Physical, chemical and sedimentological conditions for
transport and accumulation of toxics in the Bay are variable
with time and distance seaward. Bay water is partly-mixed,
well-buffered against pH change and well-oxygenated except in
summer when near-bottom water of the axial basin is anoxic.
Salinity and sediment influx vary seasonally with river dis-
charge and form steep seaward gradients near the inner limit
of salty water. Characteristics of suspended material define
three broad zones: (1) the turbidity maximum (stations 12-18)
with high suspended loads, fine particle size and low organic
percentages; (2) the central Bay (stations 8-11) with low
suspended loads, coarse particle size and high organic per-
centages; (3) the near-entrance reaches (stations 1-7) with
intermediate suspended loads, moderate particle size and
organic percentages. Sediment in deeper parts of the central
Bay is fine-grained, moderately organic and depositing
relatively fast. These conditions favor accumulation of
metals and fluid mud.
IV
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Mean concentrations of As, Cd, Cu, Pb, Hg, Ni, Sn and Zn
are maximal in surface suspended material from the central Bay.
The concentrations are higher than farther landward near major
potential sources, the Susquehanna River and Baltimore Harbor.
They are also 2 to 80 times greater than maximal concentrations
in fluid mud of the northern Bay and Baltimore Harbor. Cd, Cu
and Pb of surface and mid-depth water are 3 to 12 times higher
in summer than in spring. This trend, together with high percent-
ages of organic matter, suggests bio-accumulation is responsible
for the marked central Bay anomalies.
Mean concentrations of As, Cu, Mn, Ni, Pb, Sn and Zn in
fluid mud and bed sediment decrease with distance seaward from
a maximum in the Baltimore-Susquehanna River area. This
accumulation is close to major sources of contamination and
it may form by entrapment of suspended material from the
Susquehanna in the turbidity maximum.
Concentrations of Cd, Cu and Pb (we./we.) in suspended
material vary more than 2-fold over a tidal cycle. These
fluctuations are partly associated with tidal variations of
current, suspended load, particle size and organic content.
Together with seasonal changes in source input and bio-
sedimentologic processes, they make Bay metal content
highly variable.
Significant correlation coefficients for suspended material
are scant. Of note are Mn-Fe, Cu-Zn, and Cu-Pb correlations
in the northern Bay. In bed sediments, significant correlations
occur between all metals except Hg, but metals generally lack
relationships to organic content and particle size.
Metal-Fe ratios of bed sediment decrease with distance
seaward from the Susquehanna River indicating the river is a
major source of Mn, Ni and Zn. Metal-Fe ratios of suspended
material from the northern Bay are similar to those in fluid
mud because the material is derived from the mud by repetitive
resuspension.
Enrichment factors, derived from metal-Fe ratios normalized
to average shale, show Pb and Zn are abnormally high in northern
and central Bay bed sediment. They indicate the Susquehanna
River is the major anthropogenic source and its impact extends
seaward to the Potomac River mouth. Abnormally high factors
of Cd, Cu, Ni, Pb and Zn in surface suspended material of the
central Bay relate to high organic loads. This enrichment
is not natural with respect to either natural shale or plankton;
it is most likely created by bio-accumulation of wastes from
v
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distant sources. Enrichment factors for Cd, Pb and Zn from
central Bay suspended material exceed those for Baltimore Harbor
and the Rhine Estuary.
Hydrodynamic pathways of particle associated metals from a
Susquehanna source follow the estuarine circulation, mainly:
(1) seaward through freshwater reaches off the Susquehanna mouth;
(2) partial entrapment in the turbidity maximum; (3) partial
seaward escape through the upper estuarine layer, particularly
along the western shore; (4) landward transport through the
lower estuarine layer, particularly along the eastern shore of
the lower Bay; and (5) downward settling into sinks of the
central and northern Bay. Bio-ecological pathways include:
(1) ingestion by benthic filter feeders; (2) uptake by bacteria,
phytoplankton, zooplankton and fish; and (3) decomposition and
settling of particulate material.
Potentially toxic metals can be managed by: (1) dealing with
the Bay as an entity integrated with its watershed and margins,
(2) control at metal sources, (3) evaluating long-term subtle
changes and "far-field" effects, (4) evaluating metals according
to their speciation, amount in the system and toxicity, and
(5) monitoring with a scientific data base.
Research is needed to determine the character of bioaccumu-
lation in plankton, the chemical significance of sediment
resuspension, the importance of episodic events, the cause
of large metal variations and how the tributaries interact
with the Bay as a source or sink for metals and sediment.
These findings fill a gap in our knowledge of the Bay
where little has been known about metal content in two
important reservoirs, fluid mud and suspended material.
VI
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ABSTRACT
This research aimed to determine the distribution of selected
metals in suspended material and fluid mud, to identify potential
zones of toxic accumulation and trace their transport routes.
Observations of flow, salinity, suspended material, pH and
dissolved oxygen were accomplished in Bay-wide longitudinal
sections and at four anchor stations in the northern Bay between
March, 1979 and April, 1980. The observations cover a range of
conditions including seasonal high-low river discharge and
sediment influx as well as neap-spring tide range and oxygenated-
anoxic water. Samples of suspended material, fluid mud and bed
sediment were analyzed for their particle size, organic matter,
and metal content.
Metal concentrations of As, Cu, Mn, Ni, Pb, Sn and Zn in
fluid mud and bed sediment decrease seaward from a maximum in
the Baltimore-Susquehanna River area. The metals Mn, Pb arid
Zn are 4 to 6 times greater than Fe-corrected average shale
indicating major human input and good accumulation in this zone.
Metal concentrations of Cd, Cu, Pb, Ni and Zn are maximal in
surface suspended material from the central Bay. They are higher
than landward near potential sources and they exceed maximal con-
centrations in bed sediment 2 to 80 times. The enrichment is not
natural compared to average shale or plankton; it is most likely
created by bio-accumulation of man's input from distant sources.
Transport of particle-associated metals from major sources
follows either hydrodynamic pathways leading to particle
accumulation by the estuarine circulation, or bio-ecological
routes leading to bio-accumulation.
Management and monitoring strategies are provided to reduce
potentially toxic metals to acceptable levels and warn management
agencies of toxic hazards.
This report is submitted in fulfillment of Grant R806002-01-1
by the Virginia Institute of Marine Science, School of Marine
Science, College of William and Mary under sponsorship of the
U.S. Environmental Protection Agency. This report covers the
period 1 July 1978 - 30 September 1980.
Vll
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CONTENTS
Page
Foreword iii
Executive Summary iv
Abstract vii
Contents viii
Figures x
Tables xiii
Appendices xiv
Acknowledgements xv
1. Introduction 1
2. Conclusions 6
3. Recommendations 8
4. Methods and Procedures 9
Sampling locations and approach 9
Field observations 12
Laboratory procedures 13
Water and sediment analyses 13
Metal analyses 15
Quality control of metal analysis 16
Metal-sediment calculations
5. Scientific Results 18
Data acquired 18
Physical, chemical and sedimentological
conditions 18
River discharge and suspended sediment influx . 18
Temperature 21
Salinity 21
Dissolved oxygen 22
pH 24
Suspended material (solids) 24
Bed sediment properties 28
vnx
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CONTENTS, continued
Page
Heavy metal distributions 31
Suspended material 31
Bed sediment 40
Harbor distributions 42
Tidal time series 46
Dynamic features 46
Time variations of metals 51
6. Integration of Results 62
Metal interactions and correlations 62
Suspended material 62
Bed sediment 66
Metal-Fe ratios 66
Enrichment factors 69
Temporal variations and long-term changes .... 80
7. Implications of Results 87
Significance of fluid mud and suspended
material 87
Pathways of transport 89
Management strategies 95
Monitoring strategies 98
Research needs 102
8. References 104
Appendix 1 109
Appendix 2 110
Appendix 3 Ill
Appendix 4 116
Appendix 5 117
Appendix 6 120
Appendix 7 124
Appendix 8 128
IX
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FIGURES
Number Page
1. Location of stations occupied for hydrographic obser-
vations and sediment sampling. 10
2. Temporal variations of: (A) Susquehanna River inflow
at Conowingo in relation to annual average (983 m3/s)
and observation periods; (B) sediment concentrations
during the discharge period. Data from U.S.G.S. (21). 20
3. Longitudinal distribution of: (A) mean salinity,
upper; (B) mean total suspended solids, middle;
(C) mean percent organic matter, lower. Means from
all available cruise observations. 23
4. Longitudinal distribution of near-bottom, suspended
material between stations 11 and 19, northern Bay;
total suspended material, particle size, percent
organic material. 27
5. Seaward change in bed sediment properties at stations
along the Bay axis from the Susquehanna River mouth
(station 19) to the ocean (station 1). Data based on
an average of 2 to 6 measurements of surficial sedi-
ment for each station. A. Percent water content and
thickness of fluid mud. B. Percent organic carbon
content and sediment density, zone of fluid mud less
than 1.3 g/cc shaded. C. Mean particle size of non-
dispersed samples, solid, and dispersed samples,
dashed. D. Rate of fill from different data of
associated projects, Pb2 : ° from Setlock, et al. (30)
bathymetric changes from Caron (31). 29
6. Distribution of metal content in surface suspended
material with distance along the Bay axis. Median
values and range of concentrations from all avail-
able observations of this project. Shaded zone
indicates magnitude of departure between median
values and mean values for Fe-corrected average
shale, open circles. 32
x
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Number Page
7. Distribution of metal content in near-bottom sus-
pended material with distance along the Bay axis.
Median values and range of concentrations from all
available observations of this project. Shaded
zone indicates magnitude of departure between
median values and mean values for Fe-corrected
average shale, open circles. 33
8. Variation of metal content with total suspended
sediment material through a range of conditions
from Susquehanna River water through the turbidity
maximum zone and partly saline reaches of the
northern Bay: A. Iron; B. Zinc; dotted line
shows the trend of iron for comparison. Data from
near-bottom samples of cruises 5 and 6, April-
May, 1980. 39
9. Temporal variation of current velocity and total
suspended material at 30 cm above the bed,
anchor station 17, April 30, 1980. 48
10. Temporal variation of total suspended material
(solids) and percent organic content with depth
above the bed; anchor station 17, April 30, 1980. 49
11. Temporal variation of Fe, Mn and Zn over a tidal
cycle at station 11, northern Bay, May 2, 1980. 56
12. Temporal variation of Cu, Fe, Mn and Zn over a
tidal cycle at station 15, northern Bay,
May 1, 1980. 57
13. Temporal variation of Fe, Mn and Zn over a tidal
cycle at station 17, northern Bay, April 30, 1980. 58
14. Temporal variation of Pb and Cu over a tidal cycle
at station 17, April 30, 1980. 59
15. Temporal variation of Cu, Pb and Fe over a tidal
cycle at station 19, April 29, 1980. 60
16. Temporal variation of Zn and Mn over a tidal cycle
at station 19, April 29, 1980. 61
17. Metal-metal plots for near-bottom suspended mate-
rial from cruises 1-4; (A) Cu-Fe, (B) Mn-Fe,
(C) Ni-Zn. 64
XI
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Number Page
18. Metal-metal relationships for bottom sediment samples
including fluid mud for cruises 1-4; (A) Zn-Fe;
(B) Pb-Fe. 67
19. Metal-Fe ratios of bed sediment along the Bay length;
(A) Mn/Fe; (B) Zn/Fe; (C) Ni/Fe. 68
20. Metal-Fe ratios of near-bottom suspended matter along
the Bay length; (A) Cu/Fe; (B) Pb/Fe; (C) Zn/Fe. 70
21. Metal-Fe ratios of mid-depth suspended matter along
the Bay length; (A) Pb/Fe; (B) Zn/Fe. 71
22. Metal-Fe ratios of surface suspended matter along the
Bay length; (A) Cu/Fe; (B) Ni/Fe; (C) Pb/Fe. 72
23. Variation of enrichment factors: (A) For Cd, Pb and
Zn in bed sediment and fluid mud along the Bay
length; (B) Lead enrichment factors versus percent
organic matter for surface suspended material;
(C) Copper enrichment factors versus percent
organic matter for surface suspended material.
Numbers represent station numbers. 75
24. Temporal variations of: (A) Susquehanna River inflow
at Conowingo; (B) Iron concentrations; and (C) Mn
concentration during 1979-80. Data from U.S.G.S. (21). 81
25. Vertical profiles of Pb (upper) and Cu (lower) con-
tent illustrating changes in near-surface water of
the central Bay from late spring to summer. June 4-6,
CBI station 843F; Aug. 6-11, VIMS station 12, cruise
3; Aug. 27-30, VIMS station 12, cruise 4. 84
26. Distribution of total suspended material along the
Bay axis from August, 1978 through August, 1979:
(A) surface; (B) mid-depth. Zone of the turbidity
maximum, shaded. 85
27. Schematic diagram showing primary and secondary zones
of metal accumulation in fluid mud, bed sediment and
suspended material. Arrows represent likely trans-
port routes. 92
28. Schematic diagram illustrating the likely pathways
of metal cycling in the Bay. 93
Xll
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TABLES
Number Page
1. Parameters and conditions for atomic absorption
analysis. 17
2. Inventory of hydrographic and sedimentologic data
acquired. 19
3. Summary of mean metal concentrations and range in
suspended material throughout Chesapeake Bay from
all available data of this project. 40
4. Summary of mean metal concentrations and range of
Bay-wide values in fluid mud and bed sediment. 43
5. Mean metal concentrations for stations in Hampton
Roads and vicinity. 44
6. Mean metal concentrations for stations in Baltimore
and its entrance reaches in Chesapeake Bay. 45
7. Examples of metal concentrations per gram suspended
matter-time series study, over 13 hours. 51
8. Metal concentrations normalized to Fe. 54
9. Correlation coefficients (r > 0.70) for metals and
suspended sediment characteristics; cruise 4,
stations 11-19, 24; cruises 5 and 6, stations 13-18,
northern Chesapeake Bay. 65
10. Metal content of average marine plankton on a dry
weight basis, yg/g. 77
11. Comparison of enrichment factor in different coastal
areas. Factors derived from Fe corrected average
shale. 79
Kill
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APPENDICES
Number Page
1. Data for blank chemical analysis. 109
2. Recovery of metals added to HN03 during digestion. 110
3. Data for analysis of U.S.G.S. standards and National
Bureau of Standards Borine Liver. Ill
4. Data for the E.P.A. Water Pollution Study. 116
5. Data for suspended sediment, fluid mud and bed sedi-
ment replicates. 117
6. Longitudinal-depth distributions of mean metal con-
centration in suspended material, weight per weight,
for all available observations of this project along
the axis of Chesapeake Bay. Anomalous high zones,
shaded. 120
7. Longitudinal distributions of mean metal concentra-
tion in fluid mud and bed sediment for all available
samples from this project along the axis of
Chesapeake Bay. 124
8. Distribution of metal content, weight per volume, in
surface and near-bottom suspended material with dis-
tance along the Bay axis. Median values and range
of concentrations from all available observations
of this project. 128
xiv
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ACKNOWLEDGEMENTS
The authors acknowledge the helpful discussions and construc-
tive criticism of colleagues at VIMS and the EPA Chesapeake Bay
Program. Laboratory analysis was accomplished by George Vadas and
John Banacki. Graduate students Craig Lukin and Pam Peebles con-
tributed to both lab and field work.
Field observations for cruises 5, 6, 9 and T were accomplished
from the R/V Warfield of the Chesapeake Bay Institute, M. Grant
Gross and R.W. Taylor, Directors, as part of'a cooperative effort
coordinated by the Chesapeake Bay Program. William Cronin of CBI
performed many of the field observations and reduced the data.
Computer processing and analysis was expedited by G. Shaw
and drafting was accomplished by K. Stubblefield and P. Peoples.
C. Gaskins converted rough drafts into a typed report.
xv
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SECTION 1
INTRODUCTION
Every year about 2 million tons of sediment and a substantial
load of trace metals enter Chesapeake Bay (1). The metals are
derived from either natural sources or from man's activities.
Helz (2) established that at least one-half of the total input of
cadmium (Cd), lead (Pb), copper (Cu) and chronium (Cr) to the
northern Bay is derived from human sources. However, no single
source predominates for all metals. The most important human
source is sewage and industrial wastes (3). Additionally, metals
are supplied by harbor activities including shipping, spills and
disposal of dredged material by fallout of atmospheric material
enriched in lead, and by mining and industrial activities in the
watershed. Metal content of suspended sediment from the
Susquehanna River reportedly (4) is higher than most U.S. East
and Gulf coast rivers.
The threat of toxic metal contamination lies in the fact
that regional production is believed to be increasing with an
increase in industrial activity and with an increase in sewage
treatment plants (5). Reportedly, thousands of new potentially
toxic compounds are developed every year (5). Although trace
metals are required in low concentrations to maintain a healthy
biota, they can be toxic if present in excess concentrations.
_ -i _
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The tragic accidents caused by mercury (Hg) and cadmium (Cd)
poisioning in Japan, like Kepone in the James River, amplify the
fact that contamination extends to seafood resources leading to
man. Examples of specific toxic effects or mortality of
Chesapeake biota to individual metals are lacking, but disturbing
changes have been observed over the past decade (3). Among the
changes are: a decrease in abundance striped bass and oysters,
a lack of shad runs in the upper Bay, the virtual disappearance
of rooted aquatic plants, and declining crab and clam catches.
Toxic effects may be subtle and alter the Bay's ecosystem over
long time periods (6).
Until now, the information needed to assess the impact of
metals on the Bay is scant. Data for predicting "hot spots" and
monitoring toxic metals are inadequate. In particular, the dis-
tribution and metal content of suspended material and fluid mud
is poorly known.
This report aims to provide new information that meets
selected objectives of the EPA-States Toxics Plan of Action (6):
1. To determine the existing distribution and con-
centration of selected metals in suspended
material and fluid mud of the Bay.
2. To establish the magnitude of temporal variation
associated with tidal flow, freshwater discharge
and sediment loading, and other processes.
3. To identify major zones of metal accumulation in
suspensions and trace their sedimentological trans-
port routes. Additionally, to demonstrate the
significance of suspended material and fluid mud
in the fate of toxic metals.
- 2 -
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4. To provide strategies for monitoring and control of
contaminated sediment.
This report provides a data base describing the state of the
Bay relative to the content of selected metals in suspended mate-
rial and fluid mud. It touches on processes of accumulation and
transport that can produce the observed distributions. Manage-
ment implications are drawn but major management questions are
addressed in a companion synthesis report (7).
Suspended material and metals are studied together because
metals are adsorbed, bound and precipitated on suspended mate-
rial (8). They can be picked-up by filter-feeding organisms or
metabolized by plankton and reach high concentrations. Once
metals are tied up in suspended form, they behave like natural
sediment. They are subject to transport by waves and currents
from their source or sites of erosion to their sink or sites of
deposition. As suspended material settles, it transfers metals
from the water to the bed and can remove metals from dynamic
segments of the Bay. Generally, the residence time for metals
in suspended form is much longer than in dissolved form. In
brief, suspended material deserves attention because it can play
a major role in the transport and accumulation of potentially
toxic metals.
The term "fluid mud" describes dense suspensions of sediment
with concentrations of 10 to 480 g/1 equivalent to densities of
1.005 to 1.30 g/cm3. The mud can be generated either naturally,
e.g. by storm wave agitation of the bed, floods and strong cur-
- 3 -
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rents, or artifically, e.g. by dredging, disposal or propeller
wash on the bed. Commonly, it is derived from less dense suspen-
sions that settled from the water to the bed. Therefore, fluid
mud is an intermediate stage between mobile suspended material
and the quasi-static mud that settles and consolidates to form
a permanent bed.
Fluid mud is chemically important because it contains a
higher metal content, expressed in weight per volume, than sus-
pended material by virtue of its high concentrations (> 10 g/1).
Because the mud accumulates as loose watery masses near the bed,
it can create a high vertical gradient of suspended concentrations
and associated metals. When the mud becomes anaerobic, this
chemical gradient is enhanced by pH and Eh changes and the poten-
tial flux between mud and overlying water can become great. In
summary, fluid mud deserves attention because it serves both as
a reservoir for potentially toxic metals and as a medium for
chemical transfer.
Prior data on the occurrence of metals in suspended material
of the Bay is scant. Carpenter, et al. (9) revealed marked
variability of metals discharged by the Susquehanna River into
Chesapeake Bay. Carpenter, et al. (9) suggested that the metal
content of fine suspended sediment in the northern Bay forms a
longitudinal gradient. They revealed marked temporal variations
of metals discharged from the Susquehanna River. Analysis of
weekly samples for 18 months in 1965-1966 showed the river is
— 4 —
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enriched in iron (Fe), manganese (Mn), zinc (Zn), copper (Cu)
and nickel (Ni) during short periods in winter (9). Monthly
sampling at 3 stations in the northern Bay during 1971 (9),
showed that fluctuations of particulate Zn may be affected by
inflow as well as by biogenic cycling. From observations of Fe
and Zn, Eaton, et al. (10) showed that Susquehanna sediment
extends 60 to 80 km downstream in surface water. Loss of parti-
culate Fe was attributed to particle coagulation rather than
mixing and dilution (10). The sources, dynamic behavior and
Bay-wide distribution of suspended material is partly known from
studies of Schubel (17) and Biggs (12).
- 5 -
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SECTION 2
CONCLUSIONS
The main findings of this study are:
1.) Hydrographic observations indicate Bay water is partly-mixed,
well-buffered against pH change and oxygenated, except in
summer when near-bottom water of the central Bay below 10 m
depth is anoxic. Physical and chemical conditions for trans-
port and accumulation of toxics are highly variable with
time, depth and distance seaward from the Susquehanna River.
2.) Mean concentrations of As, Cu, Mn, Ni, Pb, Sn and Zn in
fluid mud and bed sediment decrease with distance seaward
from a maximum in the Baltimore-Susquehanna River zone.
This accumulation is close to major sources of contamination
and it may form by entrapment of river-borne suspended
material from the Susquehanna in the turbidity maximum.
3.) Concentrations of Cd, Cu, Pb, Ni and Zn are maximal in sur-
face suspended material from the central Bay. Enrichment
is not natural compared to average shale and plankton. It
is associated with high organic loads and most likely
created by bio-accumulation of wastes from distant sources.
- 6 -
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4.) Transport of particle-associated metals from the Susquehanna
follows both hydrodynamic pathways leading to particle
accumulation by the estuarine circulation, or bio-ecological
routes leading to bio-accumulation.
5.) Potentially toxic metals can be managed by: (1) dealing with
the Bay as an entity, integrated with its watershed and
margins, (2) control at metal sources, (3) evaluating long-
term subtle changes and "far-field" effects, (4) evaluating
metals according to their speciation, amount in the system
and toxicity, and (5) monitoring with a scientific data base.
6.) Research is needed to determine: the character of bio-
accumulation in plankton, the chemical significance of
sediment resuspension, the importance of episodic events,
the cause of wide metal variations, how the tributaries
interact with the Bay as a source or sink for metals and
sediment.
7.) These findings fill a gap in our knowledge of the Bay where
little has been known about metal content in two important
reservoirs, fluid mud and suspended material.
- 7 -
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SECTION 3
RECOMMENDATIONS
1. The state of the Bay should be improved with respect to
water quality by reducing source input of potentially
toxic metals, Cd, Cu, Ni, Pb, and Zn from Bay-wide
wastewater and industrial discharges. Additionally, the
turbidity, or suspended solids load, which contains more
than 60 percent organic matter in the central Bay, should
be alleviated by reducing input of nutrients that stimulate
organic production. The turbidity maximum can be reduced
by any means that will stabilize the bed and deter
entrapment of river-borne sediment. Entrapment can be
reduced by regulating inflows during periods of high
sediment influx and by enhancing salt mixing in the zone
of the maximum.
2. Potentially toxic metals should be managed with regard to:
(1) the Bay as a single entity, integrated with its water-
shed and margins; (2) control at the metal source; (3)
long-term subtle changes and "far-field" effects in zones
of accumulation; (4) metal speciation or chemical form,
its toxicity, amount in the system above natural levels
and metal associations with sediment characteristics;
(5) monitoring with a scientific data base.
3. Develop and implement a monitoring system for the Bay and
its tributaries that will warn management agencies of
encroaching toxic hazards.
4. Institute further research to determine: (1) the rate,
route, seasonality, and amount of bioaccumulation in
plankton; (2) the chemical significance of repetitive
sediment resuspensions; (3) the importance of episodic
events in release of metals from bed sediment; (4) why
metal content varies over a wide range; (5) how the
tributaries interact with the Bay as a source or sink
for metals and sediments; (6) the effects of future
changes in metal-sediment transport routes and rates
through numerical and hydrodynamic modeling.
- 8 -
-------
SECTION 4
METHODS AND PROCEDURES
SAMPLING LOCATIONS AND APPROACH
In the absence of definitive data on metal content of sus-
pended material and fluid mud, sampling stations were located to
provide general coverage of the Bay axis from the Susquehanna
River entrance to the ocean. A greater density of stations was
established across the turbidity maximum of the northern Bay
where gradients of salinity and suspended material are greater
than elsewhere. Stations were also established seaward of
potential contamination sources at Baltimore Harbor and Hampton
Roads.
Observations were planned to cover two annual cycles of
water and sediment discharge including contrasting high and low
river inflow, i.e. between March, 1979 and September, 1979.
Several cruise observations were planned to meet contrasting
conditions of spring and neap tide range, i.e. August 6-12 and
August 28-30, 1979. All observations and sampling were scheduled
close to slack water ( + 1 hour) to permit comparison of data from
station to station without the effects of sediment resuspension
from the bed. Generally, two to five stations were occupied
during each slack water for a total of 18 to 23 stations along
the Bay axis (Fig. 1). On each cruise the same stations were
-------
STATION
LOCATIONS
Figure 1. Location of stations occupied for hydrographic obser-
vations and sediment sampling.
- 10 -
-------
occupied and they were positioned by shipboard radar, or Loran C
fixes, on charted bouys or landmarks.
Our approach to sampling and selection of observational para-
meters followed three lines: (1) to collect suspended material
for analysis of toxic metals, (2) to characterize the water in
which the metals occur, i.e. the water quality and chemical
regime, (3) to characterize the sediments with which the metals
associate.
The selected metals include those that are: (1) potentially
toxic and accessible, including As, Cd, Cu, Hg, Ni, Sn, and Zn
(13); (2) poisonous having created toxic crises elsewhere,
including Cd, Cu, Hg, and Pb (13) ; (3) enriched in Chesapeake
bed sediments including Cd, Cu, Pb, and Ni (2, 14); (4) relatively
widespread and potentially useful as surrogates for geochemical
analysis including Mn and Fe. Water quality and chemical para-
meters were selected to include commonly measured parameters used
to define water quality and water masses in estuaries including
temperature, salinity, dissolved oxygen, pH and total suspended
material (solids). Additionally, the suspended concentration
provides a means to express metal concentrations per weight of
dry sediment. Attention focused on particle size and organic
(carbon) content because metal content often varies with these
parameters (13). Water content of bed sediment defines the
concentration of dense suspensions and in turn the sediment
density and thickness of fluid mud.
- 11 -
-------
FIELD OBSERVATIONS
We sampled the water by hydrographic casts using either a
2-liter plastic van Dorn bottle or a vacuum pump with polyethylene
tubing. To sample near-bottom water, the water bottle was
deployed in a tripod frame set at 30 cm above the bed. In the
water column, we sampled at standard depth intervals: i.e.
(1) for total water depths greater than 12 m, at the surface,
8 m below the surface, 3 m and 1 m above the'bed; (2) for water
depths less than 12 m, at the surface, 6 m below the surface,
2 m and 1 m above the bed. Water depths were determined either
with a standard meter wheel or a differential Bell and Howell
pressure transducer, type 4-351 zeroed at the surface. Addition-
ally, the hydrographic casts included in situ measurements of
temperature and dissolved oxygen using probes of a Yellow-Springs
meter, model 54ARC, calibrated according to standard practice
specified by the manufacturer.
We obtained bed sediment and fluid mud with either a stain-
less steel Smith-Maclntyre grab or a Bouma box core. To avoid
metal contamination, the units were coated with plastic Gulvit
compound and we obtained subsamples from inner parts of the
grabs or boxes. Additionally, we fitted the box core with a
special acrylic liner, Lukin and Nichols (4a), to prevent metal
contamination and to retain a portion of relatively undisturbed
sediment for X-ray radiography in the laboratory. Once retrieved
on deck, a plastic spatula was used to remove the top 2-3 cm of
sediment, and sub-portions from various depth intervals. Sub-
- 12 -
-------
portions were stored frozen in plastic bags for metal analysis
and in tarred aluminum containers for water content determination.
The rim of each container lid was sealed with plastic tape to
deter evaporation.
LABORATORY PROCEDURES
Water and Sediment Analyses
After recovery of water samples on deck, we measured aliquots
of water for pH using an Orion model 399A meter. The unit was
calibrated according to the manufacturer's instructions and stand-
ardized at each station with two buffers, pH 4.0 and pH 7.0.
Additionally, salinity was determined in the laboratory on a
Beckman RS-7A salinometer calibrated according to the manufac-
turer's procedures. For total suspended solids, we followed
procedures of Strickland and Parsons (15) which utilize 0.45y
Millipore membrane filters after leaching of soluble material
and tarring in a dehumidified room. Water samples were vacuum
filtered fresh, within 3 hours after recovery. The filters were
stored frozen and reweighed after drying at 85 C for 12 hours.
The 0.45ypore size is an accepted cutoff size for differenti-
ating dissolved and particulate substances (16).
Water content of bed sediments and fluid mud was determined
gravimetrically by weight loss. Approximately 20 ml of sample,
which was stored in tarred aluminum containers, was oven-dried
at 105°C for 24 hours and reweighed after cooling to room temper-
ature in a dehumidified room. The weight loss was taken as the
- 13 -
-------
weight of water in the sample and the percent water content was
calculated according to the equation:
CO
co = — X 100
C CO
Water content, co , is the ratio in percent of the weight of
\^
water in a given sediment mass, co , to the weight of the oven-
dried solid particles, co . Bulk density of the sediment, defined
as the weight per unit volume of the total sediment mass, was
derived from the water content data assuming a grain density of
2.70 using the relation:
2.70 cot
CO , + CO
d w
where co is the total wet sediment weight, co, is the dry sediment
weight and co is the weight of water.
Organic content of bed and suspended sediment was determined
gravimetrically by weight loss after combustion. For suspended
sediment the Millipore filters used for determination of total
concentration were combusted in a tarred ceramic crucible at 385 C
for 8 hours. After cooling in a dehumidified room to ambient
temperature, the remaining ash was reweighed. For control, empty
crucibles were processed with the sample crucibles including
cleaning, drying, weighing, combustion and reweighing. The
analysis gives an estimate of the organic content based on per-
cent of total dry weight.
- 14 -
-------
Particle size of suspended material was analysed in a Coulter
Counter, Model TAIL Samples were run in two ways: (1) fresh,
immediately after recovery, mainly with a 14Op tube, and (2) after
storage in a refrigerator and dispersion in Calgon and ultrasonic
treatment (1 min.) using Coulter Counter tubes of 30 and 140y
aperture diameters (equivalent to volume-size diameters of 0.6-12y
and 2.8-56y. This technique permitted distinguishing size differ-
ences between samples run fresh and dispersed in a common tube.
The differences give an indication of the degree of particle
aggregation. Resulting size data were compiled into cumulative
curves from which the statistical parameters, mean, median and
standard deviation were derived.
Metal Analyses
For trace metal analysis of suspended material, we initially
vacuum-filtered a measured volume of fresh Bay water temporarily
stored in carboy reservoirs, through a 0.45y pore size, 47 mm
diameter Nuclepore membrane filter until they clogged. The
filters were prefiltered with methanol to open air-clogged pores.
After filtering sediment, each filter was rinsed with distilled
and de-ionized water to remove sea salts. Filters were then
transferred with teflon coated tweezers to plastic petri dishes,
and kept at less than 0°C for transport and additional analysis.
Suspended matter collected on Nuclepore filters was digested
with concentrated HNC° and HC1 (17) , with the final volume
adjusted to 50 ml volumetrically. By this means we determined
- 15 -
-------
"suspended metal concentrations". Stock solutions were prepared
according to EPA Standards (17) with calibration standards made up
in HC1 to match sample acid concentrations. Fluid mud, dried at
65 C, was similarly digested (0.25 g) and prepared for analysis.
Flame atomic absorption was used to determine Fe, Mn, and
Zn. Graphite furnace (flameless) atomic absorption was used to
obtain concentrations of As, Cd, Cu, Hg, Ni, Pb and Sn. Para-
meters and conditions for these analyses are shown in Table 1.
Background correction, with either a hydrogen or deuterium lamp,
was always applied.
An indication of the need for standard addition analyses
was obtained by measuring the recovery of known metal additions
to digested suspended sediment and fluid mud samples. This
method revealed the matrix suppression of the absorption signals.
Recoveries were > 93% for all metals except Hg in suspended
sediment and Hg, Pb in fluid mud, which required standard addi-
tion corrections.
Quality Control of Metal Analysis
The following precautions were routinely observed in an
effort to keep metal contamination from various sources as low
as possible: (1) Acids were distilled at sub-boiling tempera-
tures in a fused silica still (Quartz Products Corporation,
Plainfield, N.J.). (2) Water was softened and passed through
25 ym filters and reverse osmosis membranes prior to sub-boiling
distillation. (3) All reagents and water were quantitatively
- 16 -
-------
analyzed for the metals of interest by flameless atomic absorp-
tion. (4) Labware was leached in 1:1 (v/v) HN03 and thoroughly
rinsed with high purity water. (5) Procedural blank levels were
continuously monitored for low metal levels during each atomic
absorption run.
TABLE 1
PARAMETERS AND CONDITIONS FOR ATOMIC ABSORPTION ANALYSIS
Flame AA - Varlan AA.5
Specifications
wavelength, nm
lamp current, ma
slit, u
air flow, meter
units
CM.n flow, meter
units
Fe
248.3,
373.7
5
50
7
2
Flameless AA -
Specifications
wavelength, nm
slit width, nm
lamp current, ma
N2 gas flow
sample size, ul
dry T, °C
dry t , sec
char T, °C
char 1 5 sec
atomize T, °C
atomize t , sec
signal mode
1
193.7
0.7
18
stop 3
20
105
20
1100
15
2700
8
peak
Cd
228.8
0.7
4
norm 3
20
105
20
300
10
2000
8
peak
Mn
279.5
5
50
7
2
Zn
213.9
5
100
8
2
Perkin Elmer 703, HGA 2200
Cu
324.7
0.7
10
norm 3
20
105
20
500
10
2100(mp)
8
peak
2
Ma
253.7
0.7
6
stop 3
50
105
35
200
15
2300
8 (ramp)
peak
Ni
232.0
0.2
20
norni 3
50
105
35
500
15
2700
8
peak
Pb
283.3
0.7
10
stop 3
20
105
20
500
10
2700
8
peak
Sn
286.3
0.7
30
stop 3
50
105
35
800
15
2200 (mp)
8
peak
(mp=max power)
1 one ml sample + 10 ul 1000 ppm Ni
one ml sample + 20 vd 50% H202 + 50 14! cone. HC1 (34, 35)
- 17 -
-------
SECTION 5
SCIENTIFIC RESULTS
DATA ACQUIRED
The new data inventory consists of hydrographic and sedimen-
tologic measurements and observations acquired from eight cruises.
Table 2 summarizes the data acquired. Altogether the field obser-
vations resulted in 122 stations occupied and 5,576 measurements.
In the laboratory, 560 samples of suspended material and 73 samples
of fluid mud or bed sediment were analyzed for 6 to 11 different
metals. These observations and analyses provide a larger volume
of data than acquired by previous studies. The data are provided
to the EPA Chesapeake Bay Program on computer tape, as computerized
printouts and in special scientific reports (20)(21)(22).
PHYSICAL, CHEMICAL AND SEDIMENTOLOGICAL CONDITIONS
River Discharge and Suspended Sediment Influx
The discharge rate of the Susquehanna River at Conowingo
between January, 1979 and April, 1980 varied from a daily average
peak on March 7, 1979 of 12,544 m3/s to a minimum on November 3,
1979 of 25 m3/s (23) . Figure 2A shows the variations of discharge
prior to, and during, the observation period. Corresponding
sediment concentrations (Fig. 2B) range 470 mg/1 to 13 mg/1
equivalent to about 278,000 and 2,190 tons/day. The Susquehanna
- 18 -
-------
0 -P
H C
B (U
OS 4^
U
&
g
to £
C H
0 D.
i
SS
XI
I
- 19 -
-------
10-i
3, 10
m /s
200-1
0
A. RIVER DISCHARGE
SUSQUEHANNA RIVER
TIME
SERIES
BAY-WIDE
OBSERVATIONS
470
B. SUSPENDED
SEDIMENT
iii i r 11 i i i i i i i i i i
JJFMAMJ JASONDJJFMAMj
1979
I960
Figure 2. Temporal variations of: (A) Susquehanna River inflow
at Conowingo in relation to annual average (983 m3/s)
and observation periods; (B) sediment concentrations
during the discharge period. Data from U.S.G.S. (21).
- 20 -
-------
contributes about 50 percent of the total freshwater input to the
Bay (22). Observations of the first Bay-wide cruise and the time
series were made two to four weeks after periods of peak inflow
and sediment influx.
Temperature
The longitudinal distribution of temperature in March-April,
1979, cruise 1, varied from 10.8 C in near-surface river water to
1.8 C in deeper parts of the central Bay (20). The 5.0 C isotherm,
which defines the boundary of the cold bottom water, extends
across the central basin from station 7 to 13 at the 6 to 8 m
depth. The cool pool represents residual winter-formed water
that is incompletely mixed and warmed. Stability of the water is
strengthened by freshened near-surface salinity. In contrast to
spring distributions, the summer distributions are isothermal.
Temperature measured August 28-30 varied less than 5 C from the
Susquehanna River to the ocean, and less than 2 C from the surface
to the bottom in deeper parts (20) (21). The temperature distri-
butions are similar to those presented by Stroup and Lynn (25)
and Seitz (26) for comparable seasons. Temperature affects
oxygen solubility, water density and viscosity which in turn,
affects settling rates of suspended material.
Salinity profiles during the observation period were charac-
teristic of a partly-mixed estuary. Salinity increases with depth
at all stations (Fig. 3A). Greatest change occurs at 10 to 15 m
depth where the vertical gradient reaches 5 /oo salinity per 2 m.
- 21 -
-------
This feature defines a halocline that represents a boundary
between a freshened upper layer and a salty lower layer (24).
As shown in Figure 3A, mean salinity ranges from nearly fresh
(1 /oo) near the river entrance to more than 30°/oo off the Bay
entrance. The transition from fresh to salty water is gradual;
however, slight longitudinal gradients form near the l-5°/oo and
the 25-30 /oo isohalines. The inner gradient is more pronounced
(5 /oo per 12 km) during high river inflow, e.g. March-April,
1979 than during low inflow, e.g. August 28-30, 1979 (20)(21).
With subsiding river inflow from April 1-2, 1979 to August 27-30,
1979, the 5% surface isohaline moved landward 42 km and the
vertical gradient weakened. The range of salinity values,
patterns and vertical structure are similar to those reported
by Stroup and Lynn (25) and Seitz (26) for comparable times of
the year.
Dissolved Oxygen
During spring, March 27-April 2, 1979, dissolved oxygen
concentrations varied within narrow limits (8.1 to 12.9 ppm).
By May, at higher water temperatures, concentrations values
were lower, less than 5 ppm, especially in near-bottom water
below 12 m. By early June 4-6, oxygen content was nearly
depleted in the axial basin below the 8-12 m depth (21). Such
a change is an annual event in the Bay (24). It is mainly
caused by increased oxygen utilization as temperature increases
seasonally. It can be intensified by die-off of plankton and by
- 22 -
-------
RIVER
MEAN SALINITY % ft-
0
10
E
jff 20
Q.
LU ,n
O 30
40
B
i i i i i iii i i i i
' S
8-4^
>5
•r
•«<5 '
Slfiijxv'i: MEAN TOTAL jixSi:!:!:!:::!
SUSPENDED SOLIDS mg/l
i » *\ < t i \
ORGANIC MATTER. °/00V
CLt^JJJt
320
280 240 200 I60 I20 80 40 0
-DISTANCE LANDWARD, km.
Figure 3. Longitudinal distribution of: (A) mean salinity,
upper; (B) mean total suspended solids, middle;
(C) mean percent organic matter, lower. Means
from all available slack water cruise observations
- 23 -
-------
freshening of near-surface water which increases haline stratifi-
cation and thereby decreases vertical mixing.
The pH or hydrogen ion concentration, varies within narrow
limits throughout most of the Bay. Most values range from 7.2 to
8.3 pH with relatively low values (< 7.5 pH) in the northern Bay
between stations 12 and 18 and high values (7.5-8.3 pH) in the
Southern Bay. Measurements from the June 4-6 cruise in the middle
Bay reveal a decrease in pH values with depth, from 8.2 pH at the
surface to 7.5 pH at 32 m depth. The range and magnitude of pH
is comparable to previous values recorded by Stroup and Lynn (63)
and by Seitz (71).
Suspended Material (solids)
The concentrations of total suspended material, which
include both organic and inorganic constituents, exhibit three
major distributional features (Fig. 3B): (1) a zone of inter-
mediate values, 5 to 9 mg/1, near the Bay entrance between
stations 2 and 6. This is a zone where sediment resuspension
from the bed. (2) a downward increase with high concentrations
just above the bed. Such a vertical gradient in instantaneous
profiles can be produced both by downward settling and by
resuspension of bed sediment. (3) a zone of relatively high
values, greater than 30 mg/1 near the inner limit of salty water
at l°/oo salinity, stations 15 to 18. This zone is called the
turbidity maximum (11). Concentrations in the maximum (Fig. 3B)
are higher than farther seaward in the Bay or landward in river
- 24 -
-------
water. With time the concentrations are higher in March-April,
1979, i.e. over 150 mg/1, a time of high Susquehanna inflow and
sediment influx, than in August 6-11 at similar conditions of
tide, when they were less than 90 mg/1. When longitudinal sec-
tions of suspended material obtained at contrasting spring and
neap tide conditions are compared, e.g. August 6-11 and August
27-30, it is evident that concentrations in the maximum are 1.5
to more than 2 times greater during spring than during neap tide
range. This trend suggests that resuspension from the bed plays
an important role in supplying the turbidity maximum.
The mean organic content of suspended material ranges from
less than 15 percent by weight in the turbidity maximum to more
than 60 percent in near-surface water of the southern Bay (sta-
tions 6 to 8)(Fig. 3C). The low percentages most likely form
because the total suspended material is "diluted" by inorganic
material from the bed. The high near-surface percentages are
most likely supported by plankton and their products plus
organic detritus (27). Near-surface percentages throughout the
Bay are higher in August, 1979, e.g. up to 86 percent, than in
March-April, 1979, e.g. up to 47 percent. Relatively low values
in near-bottom water of the turbidity maximum persist in measure-
ments from May through August, 1979 (20)(21).
Particle size by volume of non-dispersed suspended material
from August, cruise 4, is finest (3.2y mean) in the zone of the
turbidity maximum (stations 12-17) and coarsest (15.5y mean) in
- 25 -
-------
the mid-Bay (stations 8-10). Farther seaward the mean size grad-
ually diminishes to 5.6y in the ocean. With depth at slack water,
mean size varies within narrow limits, largely less than 0.20\i.
However, over a tidal cycle at one fixed station and depth, e.g.
station 17 at 4 m above the bed, mean size varies from 8.1y near
slack water to 14. Oy near maximum current. Therefore, the
particles are a mixture of relatively fine material that resides
in suspension for a long time, and coarse material that is inter-
mittently resuspended from the bed. Mean particle size of slack
water samples analyzed dispersed is as much as 8y finer than
non-dispersed material. Greatest change occurs in the turbidity
maximum near the 0.5 /oo isohaline (Fig. 4). This suggests a
portion of the suspended material consists of agglomerates.
These particles can be created by organic fecal pelletization
or by electrochemical cohesive forces (28) or chemical precipi-
tation. When mean size values of dispersed samples from the
northern Bay, August, 1979, are compared with samples from the
same area, April, 1980, the April samples are coarser by a
factor of 2 or more. Also, in near-surface water they exhibit
a seaward decrease in mean size from station 19 to 13. The
coarse values occur when input of river-borne sediment is
relatively high.
In summary, the physical, chemical and sedimentological
conditions for transport and accumulation of toxics in Chesapeake
Bay are variable with time and distance seaward. Bay water is
- 26 -
-------
SEAWARD CHANGE
50
30
10
15
10
I.
5
0
Observed
SUSPENDED
SEDIMENT
.•rrrT'l .0.5%o
!'••••.. I Solinity
Expected -^ " ' ' • -,
I*-TURBIDITY MAXIMUM ZONE^'l
Dispersed
PARTICLE SIZE
40
o/
/o
20
L 22
% ORGANIC
STATIONS
19 18 17 16 15 14 13 II
40
20
0
Fe
:o.5%0
'. Salinity
4.2 X Mean
•
Zn
6.6 X Mean
40
1.8 X Mean
60 km
RIVER
DISTANCE SEAWARD
BAY
Figure 4. Longitudinal distribution of near-bottom suspended
material between stations 11 and 19, northern Bay;
total suspended material, particle size, percent
organic material.
- 27 -
-------
partly-mixed, well-buffered against pH change and oxygenated except
in summer when near-bottom water of the axial basin is anoxic.
Salinity and sediment influx vary seasonally with river discharge
and form steep seaward gradients near the inner limit of salty
water. Characteristics of suspended material define three broad
zones: (1) the turbidity maximum (stations 12-18) with'high
suspended loads, fine particle size and low organic percentages;
(2) the central Bay (stations 8-11) with low suspended loads,
coarse particle size and high organic percentages; (3) the near-
entrance reaches (stations 1-7) with intermediate suspended
loads, moderate particle size and organic percentages.
Bed Sediment Properties
The Bay is floored by an admixture of sediments from varied
sources, the river, shores, sea and organic production in the Bay
itself. Despite varied sources the sediment properties change
systematically along the Bay axis. As shown in Figure 5A, water
content (wet weight) of the top 1 cm of sediment mainly increases
from 181% to 440% with distance away from the Susquehanna River
mouth (stations 11-16). Except for a slight reduction at
station 16 to 18, this trend of water content is accompanied
by decreasing bulk density (Fig. 5B), increasing rate of fill
(Fig. 5D) and increasing thickness of fluid mud (Fig. 5A).
That is, the depth of the density at 1.3 g/cc, equivalent to
480 g/1, increases seaward as the surficial water content
increases. In the central Bay basin (stations 8-11), water
- 28 -
-------
SEAWARD CHANGE OF SEDIMENT PROPERTIES
19 18 16 15 14 13 12
STATION NUMBER
98
2 I
500
THICKNESS OF
FLUID MUD
8
4
2
B SEDIMENT DENSITY *
\ .-•*••-.. . .A.--'
A .-' -A- *
. +.„. n i im MI in — — *l \ •
•'. . • • \ 13 ' -• ^ BED SEDIMENT—*1"
\J N*--'' \fr — -*-- ORGANIC CARBON
"~ — • ^
2.0
1 ^
n
1.0 °
200
100
80
60
o. 40
o
20
10
6
PARTICLE SIZE
MEAN.ju
-IO%SAND-
>*
\.
E
E
\
-------
content is more than 300% and fluid mud exceeds the penetration
depth of the box core (44 cm) at most stations. Rate of fill is
higher than elsewhere. Farther seaward in partly sandy sediment
(stations 1-7) and shoaler depths, the water content diminishes
to less than 70%, the bulk density increases to 1.91 g/cc and
rate of fill is relatively low. In summary, sediment properties
in deeper parts of the central Bay are favorable for accumulation
of metals and fluid mud. The sediment is fine-grained, organic
carbon percentage is substantial and the rate of fill is greater
than elsewhere.
- 30 -
-------
HEAVY METAL DISTRIBUTIONS
Suspended Material
The longitudinal Bay-wide distributions of metal concentra-
tions in this section are expressed either as dry weight per
gram of suspended material (e.g. yg/g),or as weight per liter of
Bay water (e.g. mg/1). The latter units reflect both the metal
content and the concentration of suspended material. All metal
concentrations are derived from analysis of bulk samples,
unfractionated for particle size. However, the mean particle
size of suspended material is relatively small, less than 16u.
The distributions are presented in graphs, Figures 6 and 7
displaying median values and ranges for all available data at
each station. Additionally, longitudinal-depth sections of
mean values for all available data are provided in Appendix 6.
Mean and median values reported as "less than" were derived
by halving the less than values and incorporating them with
averages for regular values. Graphs of longitudinal-depth
distributions for each cruise and each metal are given in
special reports (20) (21) (22). The distinctive features of
the distributions for each metal are given below.
Arsenic--
This metal varies within relatively narrow limits, from
5.85 to 62 ug/g. Locally a few hot spots of high values occur
in the central Bay at the surface or at mid-depth, stations 6-9,
but many values seaward of station 13 are necessarily reported
- 31 -
-------
METALS IN SUSPENDED MATERIAL
SURFACE
221318 16 14 312 II 10 9 8 76521
STATION
22 I9IB 16 14 1312 II 10 9 8 76 5 21
100
5
4
3
2
I
0
400
300
200
100
CADMIUM,
IRON
LEAD i48'
/V
\
280 240 200 160 120 80 40 0
•« DISTANCE, km
8
7
6
f:
3
2
I
0
10
9
8
7
? 6
' 5
4
3
2
400
300
n
200
MERCURY
MANGANESE
Jio B 9j.ee1
I 120
NICKEL 420 480 770
TIN
\
ZINC
N
280 240 200 160 120 80 40 0
•< DISTANCE, km
Figure 6.
Distribution of metal content in surface suspended
material with distance along the Bay axis. Median
values and range of concentrations from all available
observations of this project. Shaded zone indicates
magnitude of departure between median values and
mean values for Fe-corrected average shale, open
circles.
- 32 -
-------
METALS IN SUSPENDED MATERIAL
NEAR-BOTTOM
STATION
221918 16 14 1312 II 10 9 8
7652
STATION
221918 16 H 13 12 II 10 9 8
76521
280 240 200 160 120 80 40
< DISTANCE,km
9 MANGANESE
I
-?3oo
o»
3
200
100
0
60
DEPARTURE
FROM Av.
SHALE
NICKEL
TIN
ZINC
280 240 200 160 120 80 40 0
i DISTANCE, km
Figure 7.
Distribution of metal content in near-bottom suspended
material with distance along the Bay axis. Median
values and range of concentrations from all available
observations of this project. Shaded zone indicates
magnitude of departure between median values and mean
values for Fe-corrected average shale, open circles.
- 33 -
-------
as "less than". Arsenic in surface suspended material from the
central and lower Bay is generally higher than near-bottom sus-
pended material.
Cadmium—
Of the 11 metals analyzed, cadmium is the most variable.
It ranges 0.12-790 yg/g with hot spots at different depths
between stations 9 and 14 and at station 2. A secondary surface
maximum at station 12 reflects potential sources in Baltimore
Harbor. Median values of surface cadmium are distinctly higher
in the central Bay than elsewhere except for station one (Fig. 6),
The central zone has a higher percentage of organic matter than
elsewhere.
Copper—
The trend for copper resembles the trend for cadmium. It
reaches a maximum of 410 yg/g (median value) in surface sus-
pended material of the central Bay, station 8. This is higher
than farther landward or seaward. The copper maximum occurs
at the same station as the cadmium and lead maxima. Surface
and mid-depth values from the central Bay are higher than near-
bottom values by a factor of 2 or more. Stratification is
common to most longitudinal copper distributions except in
early June (cruise 9) and late August (cruise 4). There is
a moderate gradient of decreasing concentrations with distance
away from the Susquehanna River mouth, stations 22 to 17.
Copper concentrations in the central Bay are 6 to 10 times
greater in early August (cruise 3) than in March-April (cruise 1)
- 34 -
-------
Iron—
This metal varies within narrow limits. The extreme range
is 0.29 to 17.0%; however, most values are within the range 2
to 5% and the mean is 3.11%. As shown in Figures 6 and 7, iron
generally decreases with distance seaward from the river. The
greatest reduction in surface suspended material takes place at
station 11. With depth, however, iron distributions are rela-
tively constant.
Lead—
This element exhibits a maximum of 320 yg/g (median value)
in surface suspended material at station 8. Like cadmium a
secondary maximum occurs at stations 12-13 off Baltimore Harbor,
There is also an increase toward the Susquehanna River mouth,
especially in near-bottom suspended material, which reaches a
maximum of 190 yg/g at station 22. Lead ranges from 21 to 730
yg/g with local hot spots greater than 600 yg/g at the surface
and mid-depths of the central Bay. Most anomalies occur in the
June 4-6 (cruise 9) observations.
Manganese—
This element decreases irregularly from the northern to the
lower Bay. It reaches a peak of 4.20 mg/g (median value) at
station 12. The greatest seaward change takes place in near-
bottom suspended material between stations 13 and 11, where
median values drop from 4.20 to 0.31 mg/g (Fig. 7). In June
4-6 and August 6-11, 1979 observations, manganese in the
- 35 -
-------
central Bay is lower in near-bottom water than in surface and
mid-depth water by factors of 5 to 50 (21). At this time near-
bottom water is depleted in dissolved oxygen (21). By contrast,
vertical distributions of manganese in March-April, 1979 are
relatively uniform and concentrations are reduced to less than
4.8 mg/g.
Mercury—
This metal ranges 0.05-59 yg/g and reaches a maximum
(median) concentration of 9.75 yg/g in surface suspended mate-
rial of the central Bay, station 7 (Fig. 6). Although near-
bottom concentrations are lower and less variable than surface
concentrations, a median peak of 4.55 yg/g occurs at station 12
(Fig. 7). Mean surface concentrations of the central Bay are
4 times higher than near-bottom concentrations. The large
number of less than values in individual observations precludes
distinct longitudinal and temporal trends.
Nickel—
The trend for nickel in surface suspended material resembles
lead and zinc. Median values reach a maximum of 280 yg/g at
station 9 and a secondary maximum of 170 yg/g at station 12
(Fig. 6). Surface values are more than 2 times higher than
near-bottom values and mean vertical distributions are strati-
fied in the central Bay. Except for an anomaly of high values,
greater than 400 yg/g, at mid-depth between stations 10 and 12
in June, 1979 (21), temporal changes from cruise to cruise are
relatively small.
- 36 -
-------
Tin—
This element exhibits two maxima in surface suspended mate-
rial, stations 7 and 12 with median concentrations of 44 and 39
yg/9rrespectively. This metal exhibits a large range of values,
0.25 to 290.0 ug/g. Mean surface values are generally 2 to 3
times greater than near-bottom values in the central Bay, a trend
resulting in vertically stratified distributions.
Zinc—
This metal is very abundant throughout the Bay. Concentra-
tions reach a median peak of 1.90 mg/g in surface suspended mate-
rial of the central Bay (Fig. 6). Secondary maxima occur at
stations 5 and 12. Similar trends are found in near-bottom sus-
pended material, but the peaks are flatter and the median values
are about half of those at the surface (Fig. 7). Values range
0.10 to 7.10 ug/g. Local hot spots occur in the central Bay at
mid-depth in June 4-6, 1979 distributions, near the bottom
August 28-30, 1979 and at the surface March-April, 1979 (20)(21).
In most distributions zinc is lower in the turbidity maximum zone
than elsewhere. Zinc is generally higher throughout the Bay in
March-April, 1979 than at other times observed.
When the metal distributions, reported as weight per volume,
e.g. ug/lf are examined, it is evident the metal concentrations
vary with the distribution of total suspended material. That is,
where the suspended concentrations are high, most metal concentra-
tions are also high. For example, in the zone of the turbidity
maximum, concentrations of As, Fe, Mn, Ni, Sn and Zn reach a
prominent maxima (Fig. 4, Appendix 8).
- 37 -
-------
Figure 8A shows a linear trend of iron with total suspended mate-
rial despite a change of water types from the Susquehanna River
through the turbidity maximum and partly saline reaches of
northern Chesapeake Bay. By contrast, metals like Cd, As, and
Hg with wide ranges and anomalous hot spots, locally depart
from the trend. Then too, near-bottom manganese from the central
Bay in summer is lower than expected from its concentration of
suspended material. Figure 8B shows how zinc, from near-bottom
samples in river water, the turbidity maximum and partly saline
water of the northern Bay, departs from the linear trend of
iron.
In summary, the longitudinal distributions of mean and
median metal content by weight are marked by relatively high
values of As, Cd, Cu, Pb, Hg, Ni, Sn and Zn in surface suspended
material of the central Bay, stations 5-9. Metal concentrations
in this zone are higher than farther landward or seaward. Mean
surface and mid-depth concentrations are higher than near-bottom
concentrations resulting in vertically stratified distributions.
Secondary maxima occur at Bay stations 12 and 13 off
Baltimore Harbor for surface concentrations of Cd, Mn, Ni,
Pb, Sn and Zn, and for near-bottom concentrations of Cu, Hg,
Mn, Pb and Zn. Concentrations of Hg, Pb, Zn and to a lesser
degree As, Cu and Sn decrease with distance away from the
Susquehanna River mouth, stations 22-16. Seasonal changes are
marked by a 10-fold increase in surface copper concentrations
- 38 -
-------
2.0-
Fe
mg/l
1.0
A IRON-SUSPENDED
SEDIMENT
30
rz=.86
20-
Zn
''.>,'
'TURBIDITY MAX.
10-
( *\ BAY
rz=.26
B ZINC-SUSPENDED
SEDIMENTS
20 40
SUSPENDED SEDIMENT, mg/l
60
TURBIDITY
i
•»*/•> i
SUS'Q; . • \
..;l\.i.\'''
BAY
20 40
SUSPENDED SEDIMENT, mg/l
60
Figure 8. Variation of metal content with total suspended sedi-
ment material through a range of conditions from
Susquehanna River water through the turbidity maximum
zone and partly saline reaches of the northern Bay:
A. Iron; B. Zinc; dotted line shows the trend of
iron for comparison. Data from near-bottom samples
of cruises 5 and 6, April-May, 1980.
- 39 -
-------
in summer, May-August relative to March-April. Lead is higher
in June observations than at other times whereas zinc is higher
in March-April than in early August observations.
Table 3 summarizes the mean metal concentrations and range
of values throughout the Bay for all available data of this
project.
TABLE 3. SUMMARY OF MEAN METAL CONCENTRATIONS AND
RANGE OF BAY-WIDE VALUES IN SUSPENDED
MATERIAL: EXPRESSED WEIGHT PER WEIGHT,
LEFT; WEIGHT PER VOLUME, RIGHT.
Range
0.006-5.00
0.003-3.80
0.068-17.00
0.01-12.00
0.10-15.00
0.48-1000.00
0.01-0.47
0.03-34.00
0.01-4.80
0.55-94.00
Metal
As yg/g
Cd yg/g
Cu yg/g
Fe %
Pb yg/g
Mn mg/g
Hg yg/g
Ni yg/g
Sn yg/g
Zn mg/g
Fluid Mud
Mean
13.00
14.16
127.96
3.11
160.30
2.88
3.89
95.80
17.97
0.75
and Bed
Range
0.55-100.00
0.12-790.00
9.90-570.00
0.29-17.00
21.00-730.00
0.08-46.00
0.05-59,00
4.80-770.00
0.25-290.00
0.10-7.10
Sediments
Metal
As yg/1
Cd yg/1
Cu yg/1
Fe mg/1
Pb yg/1
Mn yg/1
Hg yg/1
Ni yg/1
Sn yg/1
Zn yg/1
Mean
0.32
0.14
1.84
0.88
2.27
65.13
0.035
2.00
0.20
11. 02
The longitudinal Bay-wide distributions of mean metal con-
centrations in fluid mud and bed sediment along the axis of
Chesapeake Bay are illustrated graphically in Appendix 7. The
data were obtained from bulk, unfractionated samples. Distinc-
tive features of the distributions are given below.
- 40 -
-------
Arsenic, Lead, Tin, Zinc—
These metals exhibit similar distributions consisting of
maximum concentrations at stations 13-16. Landward toward the
Susquehanna mouth, mean concentrations drop irregularly to less
than 25 percent of their maximum value. Seaward concentrations
decrease irregularly in a broad gradient to the ocean. The
maximal values lie off potential metal sources, Baltimore Harbor
and Gunpowder River. Station 13 lies near the Kent Island
dredged material disposal area, and a zone of high clay con-
tent (33).
Copper, Nickel—
These metals exhibit similar Bay-wide trends. Copper
reaches a maximum of 44.5 yg/g (mean) at station 19. It remains
relatively high,above 25 yg/g, seaward to station 11. Potential
human sources of copper are Baltimore Harbor, Kent Island dis-
posal area and the Susquehanna River (2). In fluid mud of the
central Bay basin, mean copper values are nearly constant at
17 yg/g but concentrations drop farther seaward in sandy sedi-
ment of the lower Bay (Fig. 5C).
Cadmium—
The distribution of cadmium is irregular and values have
a wide range. There are three peak concentrations at stations
8, 11 and 15, but the Susquehanna mouth and near-ocean sediment
are low.
- 41 -
-------
Iron—
Iron varies within narrow limits. Concentrations are slightly
higher at stations 12-15 off Baltimore Harbor, a potential human
source. However, iron is an abundant element common to natural
sediments.
Mercury—
Since most concentrations of this metal are reported as less
than values, distinct trends are not evident in the distributions.
Manganese—
This element exhibits elevated concentrations between stations
13 and 19 with a maximum of 3.9 mg/g (mean) at station 14, seaward
concentrations drop rapidly at station 12 and remain low to the
ocean except for station 6.
Table 4 summarizes the mean metal concentration and range of
values in fluid mud and bed sediment throughout the Bay.
In summary, most Bay-wide metal distributions in fluid mud
and bed sediment, except Cd, Fe and Hg, generally decrease seaward
from a maximum in the Baltimore-Susquehanna mouth zone, stations
13-19, a potential source of major contamination. Alternately,
the seaward decrease is produced by mixing of metal impoverished
sediment derived from shore erosion of the central and lower Bay.
Moreover, low metal concentrations in the lower Bay are from a
zone of coarse-grained sediment.
Harbor Distributions
The distribution of mean metal concentrations in Hampton
Roads and Baltimore Harbor is presented in Tables 5 and 6.
- 42 -
-------
TABLE 4. SUMMARY OF MEAN METAL CONCENTRATIONS AND RANGE OF BAY-
WIDE VALUES IN FLUID MUD AND BED SEDIMENT EXPRESSED AS
DRY WEIGHT PER WEIGHT.
Metal Mean Range
As, yg/g 3.90 0.67-11.00
Cd, yg/g 0.33 0.02-1.40
Cu, yg/g 19.60 0.40-50.00
Fe 2.40 0.45-4.10
Pb yg/g 32.00 2.80-99.00
Mn, mg/g 1.30 0.05-6.10
Ni, yg/g 28.50 1.90-64.00
Sn, yg/g 0.52 0.05-2.10
Zn, mg/g 0.15 0.02-0.71
The stations are located in transects at 5 to 10 mile intervals
extending from the central Harbor seaward to, and partly in-
cluding, the Bay-wide longitudinal section (Fig. 1).
When metal distributions in suspended material and fluid
mud from Hampton Roads are compared along transects, the
metals Fe, Mn, and Zn exhibit little change (Table 5). However,
fluid mud and bed sediment from Hampton Roads (station 4) has
higher concentrations of Cu, Pb, Zn, Hg and As than farther
seaward, stations 1-3. In particular, copper concentrations in
the harbor exceed those in the ocean sediments by more than
eight times. Similar gradient are found for near-bottom sus-
pended material. By contrast, surface suspended material from
the lower Bay and ocean has higher concentrations of As, Cd,
Cu, Pb, Sn and Ni than the Roads. Concentrations in the Bay
- 43 -
-------
TABLE 5. MEAN METAL CONCENTRATIONS FOR STATIONS IN HAMPTON
ROADS AND VICINITY; EXPRESSED WEIGHT PER WEIGHT.
FOR STATION LOCATIONS, SEE FIGURE 1.
Station
Metal
Arsenic, yg/g
surface
bottom
bed
Cadmium, ug/g
surface
bottom
bed
Copper, yg/g
surface
bottom
bed
Iron, %
surface
bottom
bed
Lead, yg/g
surface
bottom
bed
Manganese, mg/g
surface
bottom
bed
Mercury, yg/g
surface
bottom
bed
Nickel, yg/g
surface
bottom
bed
Tin, yg/g
surface
bottom
bed
Zinc, mg/g
surface
bottom
bed
4
Harbor
5.4
15.5
3.0
8.2
4.1
0.06
57.0
80.5
8.4
3.1
4.9
1.5
98.5
132.2
15.2
1.0
1.8
0.3
2.9
3.9
0.07
62.6
108.2
9.0
10.0
10.9
0.5
0.9
0.8
0.07
3
Bay
12.7
12.8
2.9
144.7
2.1
0.15
62.7
292.0
3.8
3.3
2.9
1.3
131.5
53.7
9.1
1.2
1.1
0.3
2.9
1.3
0.03
71.5
70.2
8.4
9.9
15.6
0.3
1.0
0.8
0.05
2
Bay
7.6
10.7
1.5
21.3
23.2
0.03
62.7
59.4
1.0
1.4
2.1
0.6
146.0
95.8
3.7
0.6
0.7
0.1
3.7
2.1
0.03
38.5
121.5
2.8
15.4
5.9
0.2
7
7
0.02
1
Ocean
12.7
5.9
1.5
49.0
11.4
0.03
132.5
36.0
0.65
0.3
1.2
0.7
225.0
149.5
5.1
0.4
1.1
0.1
6.5
3.3
0.04
210.5
24.5
3.2
34.8
22.0
0.1
0.9
0.4
0.02
44 _
-------
TABLE 6. MEAN METAL CONCENTRATIONS FOR STATIONS IN BALTIMORE
HARBOR AND ITS ENTRANCE REACHES IN CHESAPEAKE BAY,
EXPRESSED WEIGHT PER WEIGHT. FOR STATION LOCATIONS,
SEE FIGURE 1.
STATION
23* 21 20 13 12
Harbor Harbor Entrance Bay Bay
Metal
Arsenic, yg/g
surface
bottom
bed
Cadmium, yg/g
surface
bottom
bed
Copper, yg/g
surface
bottom
bed
Iron, %
surface
bottom
bed
Lead, yg/g
surface
bottom
bed
Manganese/ mg/g
surface
bottom
bed
Mercury, yg/g
surface
bottom
bed
Nickel, yg/g
surface
bottom
bed
Tin, yg/g
surface
bottom
bed
Zinc , mg/g
surface
bottom
bed
*Values for cruise 4, August 28-30 only.
13.0
63. 0
1.1
<5.5
<6.3
0.5
110.0
320.0
120.0
1.9
5.4
4.8
87.0
240.0
62.0
4.6
3.3
1.0
1.7
1.7
0. 05
28.0
49.0
46.0
8.7
37.0
1.8
0.6
0.8
0.3
16.4
21.6
4.0
17.8
2.9
0.4
111.5
47.5
44.5
4.3
4.9
185.0
60.5
164.0
7.0
5.8
2.8
2.8
0.4
0.12
70.2
61.8
49.5
17.4
10.6
1.8
1.0
0.3
0.4
8.8
25.5
3.9
8.6
1.0
0.5
86.0
60.3
45.0
3.9
3.6
119.5
60.7
65.5
4.5
9.9
3.2
2.0
0.4
0.03
57.5
87.0
37.2
9.2
18.8
1.6
0.7
0.5
0.3
7.4
15.9
5.3
11.4
11.4
0.4
162.6
104.1
26.5
3.0
4.0
3.2
267.2
162.0
59.8
3.5
4.7
3. 0
3. 5
1.4
0.04
103.4
86.2
50.8
11.9
5.7
1.2
0.6
0.8
0.2
7.8
11.1
5.8
27.3
5.2
0.4
158.0
83. 8
27.8
3.4
3.5
3.3
208.6
122.1
48.0
5.1
10.5
1.2
3.6
4.9
0.04
174.9
94.0
28. 2
33.9
12.0
0.5
0.9
0.6
0.2
- 45 -
-------
exceed those in the harbor by 2 to 3 times but they are less than
the elevated concentrations in the central Bay.
Fluid mud and bed sediment from Baltimore Harbor (stations
20-21) has higher concentrations of Cu, Hg, Pb and Ni than sta-
tions in the adjacent Bay (12 and 13), Table 6. In particular,
copper concentrations in the harbor exceed those in the Bay by
5-fold. Arsenic, however, is more than 5 times greater in the
Bay than in the harbor. Similarly, Cd, Ni, Hg and Mn in near-
bottom suspended material of the Bay exceed those of the harbor
by more than 2 times. In surface suspended material relatively
steep gradients form whereby Sn, Ni, Hg and Pb are higher in
the Bay than in the harbor (Table 6). Thus, the distributions
are complicated and gradients shift for different metals and
different depths.
Comparison of harbor values, Tables 5 and 6, indicates bed
sediment concentrations from Baltimore are 3 times higher for
Fe, 9 times for Mn, 5 times for Ni and 14 times higher for Cu,
than Hampton Roads. Near-bottom suspended material from
Baltimore is 4 times higher in As and Cu than Hampton Roads.
On the other hand, cadmium and mercury are generally higher in
suspended material from Hampton Roads than from Baltimore.
TIDAL TIME SERIES
Dynamic Features
Observations over a 13-hour tidal cycle at four anchor
stations in the northern Bay, define short-term hydrodynamic
- 46 -
-------
and sedimentologic fluctuations affecting temporal variations
of metal concentrations. The most prominent feature of the time
series is the large fluctuation of total suspended material.
For example, as the tidal current increases after slack water,
either flood or ebb, the suspended material increases and reaches
a peak just after maximum current (Fig. 9). Concentrations
increase mainly when the current reaches about 20 to 30 cm per
sec. Therefore, the concentration increase lags the increase
of current by about one to two hours. Similarly, peak concentra-
tions lag peak current velocity. Subsequently, as current
diminishes, suspended material drops to a minimum near slack
water. Over an entire tidal cycle, suspended concentrations
repeat a cyclic pattern that go up and down with the strength
of the current as material is alternatively resuspended and
settled to the bed.
The temporal fluctuations of suspended concentrations are
greater near the bed than near the surface (Fig. 10). Conse-
quently, the bed is the likely source of suspended material.
By contrast, near-surface loads representing a background load
remain in suspension for a long time.
The fluctuations of suspended load are accompanied by
fluctuations of particle size and organic content. For example,
at 30 cm above the bed, station 17, mean size increased from
about 11 y near slack water to 15 y near maximum current while
corresponding surface size ranged 7.5 to 10.5 y. The background
- 47 -
-------
40-
20-
cm/s
0-
-20-
-40-
TOTAL
SUSPENDED
MATERIAL
CURRENT
TIME-
NEAR-BOTTOM
14 MRS.
TIME
Figure 9. Temporal variation of current velocity and total sus-
pended material at 30 cm above the bed, anchor
station 17, April 30, 1980.
- 48 -
-------
40n
. CURRENT
NEAR-BOTTOM
A.
TOTAL
SUSPENDED
MATERIAL
B.
10 -i
1 I
14 MRS.
TIME —»-
TOTAL SUSPENDED SOLIDS mg/l
STATION 17
0
0200 0400 0600 0800 1000 1200 1400 1600
TIME(EST)
PERCENT ORGANIC %
10 n
0200 0400 0600 0800 1000 1200 1400 1600
TIME(EST)
Figure 10.
Temporal variation of total suspended material (solids)(B)
and percent organic content with depth above the bed (C) ;
anchor station 17, April 30, 1980.
- 49 -
-------
load,which remains in the water column at slack water,consists
of very fine-grained particles with a narrow size range. Its
temporal and spatial variability of mean size is relatively
small compared to the intermittently suspended load. With depth
toward the bed the resuspended load becomes coarser and more
poorly sorted. As shown in Figure 10, percent organic matter
is higher at slack water (23%) than at maximum current (14%).
Because metal content can vary with suspended load, particle
size and organic matter, it is subject to marked tidal
variation.
- 50 -
-------
TIME VARIATIONS OF METALS
As noted during earlier studies (Cruises 1-4) of this pro-
ject (20(21), metal concentrations per liter of Bay water followed
patterns set by mg/1 suspended sediment — especially in the
region of the northern Bay turbidity maximum (Stations 15-18).
Per gram of suspended matter, metal trends over the 13-hour tidal
cycles varied with station, depth, and with the particular metal
of interest (see Figures 11-16). However, as noted in Table 7,
suspended Fe, Mn and Zn remained uniform in the northern Bay
both vertically (at the surface, mid-depth, and near-bottom) and
between stations (as shown at 17 and 19) throughout the tidal
cycle. Cu and Pb were more variable, as noted for Station 17,
as was Fe at Station 11. Cd values were usually less than
3.5 yg/g at all stations and depths.
TABLE 7. EXAMPLES OF METAL CONCENTRATIONS PER GRAM SUSPENDED
MATTER-TIME SERIES STUDY (mean + standard deviation),
OVER 13 HOURS.
Metal Station Surface Mid-Depth Bottom
Fe
Zn
Mn
Fe
Zn
Mn
Cu
Pb
Fe
(%)
(mg/g)
(mg/g)
(%}
(mg/g)
(mg/g)
(yg/g)
(yg/g)
/ Q, \
I "O /
19
19
19
17
17
17
17
17
11
4.4
.26
3.6
4.3
.32
3.3
71
91
1.8
+ 0.8
+ .05
+ 1.1
+ 0.4
+ .06
+ 0.6
± 26
± 33
+ 0.8
4.0
.27
3.3
4.4
.32
3.4
66
91
0.5
+ 0.8
± -11
+ 1.0
+ 0.3
+ .06
+ 0.6
+ 13
+ 30
+ 0.2 (8m)
4.0
.27
3.5
4.2
.27
3.6
49
59
1.4
+ 0.5
+ .08
+ 0.8
+ 0.4
+ .05
+ 0.5
± 13
+ 23
+ 0.6
0.9 + 0.3 (16m)
- 51 -
-------
For the tidal cycles, specifically at Station 11, surface
suspended Fe concentrations (Fig. 11) decreased from 3.0% to
1.2% as the tides progressed from slack to ebb. At the 8 m
depth, Fe concentrations varied little. For the 16 m depth, Fe
concentrations peaked at 0500-0800 and 1100-1400 as the flood
and ebb currents decreased below 0.6 m/sec. Near the bottom,
sediment peaks in suspended Fe concentrations occurred at
0400-0700 and 1300-1500 as peak flood and ebb currents decreased
to less than 0.2 m/sec. For Mn though (Fig. 11), surface sus-
pended concentrations decreased from 4.1 mg/g to 1.7 mg/g at
0700-1000 corresponding to tidal currents changing from flood
to slack. Yet, 8 m, 16 m, and near-bottom concentrations
remained < 0.5 mg/g as flood and ebb currents dropped below
0.4 m/sec. Zn concentrations (Fig. 11), although showing more
variability than either Fe or Mn, remained constant at 8 m,
16 m, and near-bottom depths during flood current velocities
< 0.4 m/sec.
At Station 15, near-bottom Cu, Fe, Mn, and Zn (Fig. 12)
concentrations (per gram) showed little variation during flood
or ebb tidal current < 0.2 m/sec. Fe and Mn, though, produced
more cyclic characteristics depending on tidal phase — i.e.
flood, slack, or ebb.
As shown in Figures 13 and 14 for Station 17, Fe (mean-4.3%),
Mn (3.4 mg/g), and Zn (0.30 mg/g) varied within narrow limits
for all depths during flood and ebb surface currents up to
1 m/sec. As flood reached maximum at 0600, surface and mid-depth
- 52 -
-------
Pb concentrations (Fig. 13) decreased. From 0900-1100, surface
and mid-depth Cu (Fig. 14) and Pb increased as maximum ebb was
reached, decreasing afterwards.
For Station 19 (Figs. 15 and 16), suspended Cu and Pb (Fig.
15) concentrations varied considerably, though Fe (mean - 4.1%)
in Figure 15 and Zn (mean - 0.26 mg/g) in Figure 16 were constant
from slack to ebb.
Several factors could be affecting suspended matter metal
concentrations during a tidal cycle. Duinker and Nolting (34)
noted the affect of salinity changes on metal concentrations
during flood and ebb. Suspended Pb, Zn, and Fe concentrations
increased with decreasing salinity, although Mn concentrations
decreased and were least affected by particulate sedimentation
processes. Schubel (35) discussed the affects of critical
erosion speeds (35-50 cm/sec) on fine-grained sediments and the
role of vertical mixing in spreading fluctuations in suspended
sediment concentrations throughout the water column. Tidal
currents in the northern Chesapeake Bay were found to also
produce changes in particle size distribution near the bottom
(35)/ (36)/ ranging from < 3 y near slack water to > 20 y at
maximum flood and ebb, with coarsest particles nearest the
bottom. Schubel, et al. (37) divided the suspended sediment
population of the upper Chesapeake Bay into sub-groups — those
particles continually suspended and those alternately suspended
and deposited. Their analyses did not indicate any differences
in size distributions of suspended sediment at similar current
- 53 -
-------
speeds and particulate concentrations during either ebb or flood,
which of course, could affect observed metal distributions.
Metal concentrations were normalized to Fe since it is an
indicator of mineral and oxyhydroxide components of suspended
matter which can act as adsorbers. As noted in Table 8, Station
11, metal to Fe ratios were consistently higher than the other
stations sampled, except for Mn/Fe near the bottom. Similar
increased ratios in the mid-Bay had been observed during Cruises
1-4 in 1979, as noted during earlier discussions. Pb/Fe ratios
at Stations 15 and 19, surface and mid-depth, were higher and
more variable than observed at the other northern Bay station
(17) sampled. Bottom suspended matter ratios in this region were
comparable to those earlier observed for fluid mud, reflecting
TABLE 8 . METAL CONCENTRATIONS NORMALIZED TO FE
(mean + standard deviation of ratios).
Zn/Fe
.010 + .006
.011 + .004
.009 + .002
.007 + .001
.007 + .001
.006 + .001
.006 + .002
.007 + .003
.007 + .002
.026 + .019
.018 + .008
.on - Depth (m) Cu/Fe
15-0
15-4
15-bottom
17-0
17-6
17-bottom
19-0
19-4
19-bottom
11-0
11-bottom
Mn/Fe
(x 10~4)
16
17
11
16
15
12
19
19
15
45
48
± 3
± 6
+ 2
± 6
± 3
± 3
+ 7
± 9
+ 4
± 23
+ 22
.054 +
.057 +
.070 +
.079 +
.078 +
.087 +
.085 _+
.084 +
.089 +
.14 + .
.031 +
.015
.013
.008
.014
.013
.010
.034
.029
.018
,02
.011
Pb/Fe
(x 10~
54 +
43 +
24 +
21 +
21 +
14 +
39 +
32 +
28 +
110 +
82 +
•M
19
21
5
7
6
6
21
10
7
40
45
- 54 -
-------
the potential source of bed sediment resuspension and metal loads
from the Susquehanna River (37). In the upper Bay (Stations 15,
17 and 19), Cu/Fe and Zn/Fe ratios were similar among stations.
The Mn/Fe ratio at Station 11 bottom was quite low (.031 + .011)
compared to the enhanced surface suspended value (.14 + .02)
which varied little throughout the tidal cycle.
In summary, fluctuations of current strength over a tidal
cycle produce large fluctuations in suspended loads and moderate
fluctuations in particle size and percent organic content.
Associated fluctuations of Fe, Mn and Zn (we./we.) vary within
narrow limits whereas Cd, Cu and Pb vary widely, more than
2-fold. These short-term fluctuations combined with seasonal
fluctuations of processes and source input make temporal trends
of metals in the Bay highly variable.
- 55 -
-------
STATION II
METAL = Fe
3.0-1
2 0-
1.0-
SURFACE
8 m
16 m.
BOTTOM
I
0400
1 1 1 1 1 1 1 1 1
0800 1200 1600
METAL = Mn
40-|
3.0-
20H
0400
0800
1200
1600
METAL = Zn
080-i
0 70-
060-
0.50-
040-
0 30-
020-
1
0400
0800
1
1200
TIME
FLOOD
- FLOOD -
'—Slack
Water
EBB
- EBB-
1600
>Surfoce
-H Bottom
Figure 11.
Temporal variation of Fe, Mn and Zn over a tidal
cycle at station 11, northern Bay, May 2, 1980.
- 56 -
-------
100-i
ao-
60-
40-
ao-
50-
4.5-
40-
35-
30-
STATION 15
METAL = Cu
0400
METAL = Fe
0800
1200
1600
0400
METAL=Mn
0800
- 1 - '
1200
4 O-i
30-
20-
I 0-
I 10-
100-
090-
080-
o. 070-
Ot
E 060-
050-
040-
030-
020-
0400
METAL = Zn
0800
1200
1600
1600
1
0400
I
0800
1200
TIME
l Surface
— » Bottom
Figure 12.
Temporal variation of Cu, Fe, Mn and Zn over a tidal
cycle at station 15, northern Bay, May 1, 1980.
- 57 -
-------
STATION 17
METAL = Fe
5.0-
* 4-l< • EBB
l< FLOOD-
!—Slack
Water
-EBB-
1600
- > Surface
—*• Bottom
Figure 13.
Temporal variation 'of Fe, Mn and Zn over a tidal cycle
at station 17, northern Bay, April 30, 1980.
- 58 -
-------
STATION 17
METAL = Pb
160-
140-
120-
100-
80-
60-
40-
20-
SURFACE
6 m
BOTTOM
0400
0800
1200
1600
METAL = Cu
140-
120-
100-
CT<
c" 80-
60-
40
0400
K FLOOD
l< FLOOD-
0800
TIME
1200
EBB
-EBB-
- Slack
Water
- 1 - 1
1600
Surface
• Bottom
Figure 14.
Temporal variation of Pb and Cu over a tidal cycle
at station 17, April 30, 1980.
- 59 -
-------
STATION 19
METAL = Cu
160-
140-
120-
100-
80-
60-
40-
—i 1 1
0400
METAL = Pb
. 380
1
0800
1200
440 •
1600
220-
200-
180-
160-
140 •
120-
100-
80-
60-
70-i
60-
50-
40-1
0400
METAL = re
0800
1200
1600
I
0400
1 1 1 1 1 1 1 1 1
0800 1200 1600
TIME
-EBB-W*-
- FLOOD-
*- Slock
Water
-EBB-
—>! Bottom
Figure 15.
Temporal variation of Cu, Pb and Fe over a tidal
cycle at station 19, April 29, 1980.
- 60 -
-------
0.60-
040-
020-
STAT ION 19
METAL = Zn
0400
0800
1200
1600
5 0-
4 0-
30-
20-
I 0-
METAL = Mn
0400
-EBB -»K-
0800 1200
TIME
-EBB
L— Slock
Water
1600
~*\ Bottom
Figure 16.
Temporal variation of Zn and Mn over a tidal cycle
at station 19, April 29, 1980.
- 61 -
-------
SECTION 6
INTEGRATION OF RESULTS
METAL INTERACTIONS AND CORRELATIONS
To account for spatial and temporal variations of the metal
distributions and to predict the fate of metals that associate
with each other or with sediment properties, a number of com-
puterized statistical correlations were performed. Correlation
coefficients (r) of 0.70 or larger are considered significant
since these account for at least 50 percent of the covariations
at the > 95% level (18) (19), and thus define metal associations.
The correlations treat data for suspended material (1) at differ-
ent depths and (2) for time series observations and all depths.
Suspended Material
For surface suspended material most correlations varied
over wide limits. However, in data of cruises 1 and 2, March-
April and May, 1980, Mn-Fe correlate (r=0.80) except for north-
ern Bay stations of cruise 2 (20). Additionally, Cu-Zn and
Ni-Zn correlate (r=0.80; r=0.74) respectively, except for mid-
Bay and near-ocean stations of cruise 2 (i.e. numbers 1, 8, 9,
11, 12 and 13)(20).
In near-bottom suspended material from Bay-wide cruises 1
and 2, Mn and Fe correlated (r=0.81; r=0.80) but Cu is not
- 62 -
-------
highly correlated with Fe for different sampling cruises (Fig.
17A, 17B). However, Cu-Zn correlated (r=0.85; r=0.81, for cruises 1
and 2); Ni-Zn correlated (r=.83; r=0.82 for cruises 1 and 2),
Figures 17B and 17C. For selected stations from the northern
Bay, stations 12-21, Ni-Fe correlated (r=0.77) and Zn-Fe cor-
related (r=0.79; r=0.87).
In the time series observations of suspended material,
coefficients are significant for metal to metal correlations,
e.g. Fe-Mn (r=0.71) at station 15; Cu-Pb (r=0.70) at station 17;
and Fe-Mn-Pb (r > 0.80) and Cu-Zn (r=0.92) at station 11.
Additionally, pb partly correlates with mean size (r=0.67).
When correlation coefficients are calculated for eleven
different metals in relation to percent organic content, organic
concentration and mean particle size (dispersed) of suspended
material for all depths at selected longitudinal stations (11-19,
24) in the northern Bay, a few significant coefficients are
revealed (Table 9). Most of the metals, however, did not
correlate with suspended sediment characteristics. In general,
the number of significant metal-metal, and metal-sediment
characteristic correlations for suspended material is limited.
Their persistence with time, e.g. season to season, is uncertain.
The scant correlations may reflect varied sources of suspended
material and selective metal utilization by different organisms
in suspension. They support the contention that suspended mate-
rial is non-conservative and unstable (38).
- 63 -
-------
METAL INTERACTIONS
500-,
400-
300-
200 -
100-
NEAR-BOTTOM SUSPENDED MATTER
D CRUISE I
• CRUISE 2
A CRUISE 3
OCRUISE 4
V
B
a CRUISE i
• CRUISE 'i
* CBI CRUISE 9
a • **P.»a*
234
Fe(%)
250-
i 1 ^ 200-
A
+ ' ° 5 '50-
1 . D 3
DO Z
a 100
D n a
D
50
c 0
•
D
• •
A •
. a
* a •
j» % Dn
rfF »* A c
^» % °
»•
*
567 0511
Zn ( 1713/3)
Figure 17.
Metal-metal plots for near-bottom suspended material
from cruises 1-4; (A) Cu-Fe, (B) Mn-Fe, (C) Ni-Zn.
- 64 -
-------
TABLE 9. CORRELATION COEFFICIENTS (r > 0.70) FOR METALS
AND SUSPENDED SEDIMENT CHARACTERISTICS; CRUISE 4;
STATIONS 11-19, 24; CRUISES 5 and 6, STATIONS 13-18,
NORTHERN CHESAPEAKE BAY.
Organic Organic Mean
Metal Percent Concen. Size,
mg/1 y
CRUISE 4
Fe mg/1 0.73 0.76
Ni yg/1 0.70
Pb yg/1 0.74
Fe % 0.81
Hg yg/g 0.81 0.71
CRUISES 5 and 6
Fe % -0.73
Cu -0.86
Pb yg/g 0.76 0.84
0.70
Zn mg/g 0.80
*Cu/Pb/Zn > 0.75
*Fe/Mn >-0.80 -0.71
**Cu/Pb/Zn -0.96
*For stations 13-19, 22, cruise 6.
**For stations 11-18, 22, cruise 5.
- 65 -
-------
Bed Sediment
In Bay-wide bed sediments and fluid mud significant metal-
metal correlations occur between all metals except Hg, especially
As-Fe, Cu-Fe, Ni-Fe, Pb-Fe and Zn-Fe. As shown in Figures ISA,
18B, Zn and Pb follow a near-linear trend in relation to Fe with
the coefficients (r) recorded in the figures.
Fluid mud from anchor stations in the northern Bay, 15, 17
and 19, which contained metal concentrations within narrow
limits (Table 9)/showed significant correlations for Fe-Cu-Mn-
Pb-Zn (r > 0.80) .
METAL-FE RATIOS
Iron is a good element for normalizing unknown variables
associated with other metals because it is abundant and human
sources are small compared to natural sources. Additionally,
iron concentrations vary within narrow limits along the Bay
length and it has low solubility in the pH 7-8 range. Soluble
Fe in the Bay is a very small fraction of the total load (10).
Moreover, iron exhibits a significant correlation with aluminum
(32), a relatively inactive element in Bay suspended material.
Mn/Fe and Zn/Fe ratios in bed sediment decrease with dis-
tance seaward (Fig. 19) away from the Susquehanna River, a major
metal source. These trends are broadly similar to trends for
mean Mn, Zn and Ni concentrations, Appendix 7. Of note are the
elevated Mn-Fe ratios at stations 20, 21, near Baltimore Harbor,
and at stations 3, 4, Hampton Roads.
- 66 -
-------
METAL INTERACTIONS
BOTTOM SEDIMENT
D CRUISE 1 r= 92
• CRUISE 2 r= 96 I 30 -
A CRUISE 3 r- 91
O CRUISE 4 r = 97 120 -
110-
100-
. 90-
D . — ,
A "^
DI 70 ~
A 05
I-D ^ 60 -
D Al** °"
B VA
D 03* ' 40-
°QO 3Q^
•nas J
0 t) o 20-
°Jt!£*' A
n r00 R !
a
CRUISE 1 D r = 92
CRUISE 2 • r= 73
CRUISE 3 A r = 83
CRUISE 4 O r = 94 ^
•
A D
n D A o
• n.
.
n * * o
« Z o
* c&
S? A
B A0
o • « ^
wj *o?
10 20 30 40 50
Fe
10 20 30
Figure 18.
Metal-metal relationships for bottom sediment samples
including fluid mud for cruises 1-4; (A) Zn-Fe;
(B) Pb-Fe.
- 67 -
-------
SEAWARD CHANGE IN METAL/Fe RATIOS
BED SEDIMENT
o
D O
D •
^O A
D 8
320 280 240 200 160
I I I FT I M I I 1 1 1 T
D CRUISE I
• CRUISE 2
A CRUISE 3
O CRUISE 4
g
80
""©"
40 0 km
~i m—i
© ®@© ©
a A
o .Oo"
B
t • • o
oa»« a
D CRUISE I
• CRUISE 2
A CRUISE 3
O CRUISE 4
O H . Afl
o ro H S>
D
280 240 200 180 120 80 40
©»
D CRUISE 1
• CRUISE 2
A CRUISE 3
O CRUISE4
0 km
5®© 3
io-
5-
C.
"3;
nDJ o
D • 0 0 •
. D •
A DO 0
A ^
|_ -, ., |
10 280 240 200
\ o
O
D
160 120 80
1 1 1 1 1 irm — 1 III ' (?)
®® STATION NUMBERS
-«- UPSTREAM (km)
n f
¥ D
o
40 Ok
Figure 19.
Metal-Fe ratios of bed sediment along the Bay length;
(A) Mn/Fe; (B) Zn/Fe; (C) Ni/Fe.
68 -
-------
Metal-Fe ratios in near-bottom suspended material, e.g. Cu-
Fe, Pb-Fe and Zn-Fe for northern Bay stations 13-19, vary within
narrow limits (Fig. 20). The ratios, Cu-Fe, Mn-Fe and Zn-Fe
are comparable to those in fluid mud, a trend that can develop
as the bed mud is repeatedly resuspended. This is confirmed by
time series variations of ratios whereby Cu-Fe ratios are lower
near maximum current than slack water. On the other hand, Pb-Fe
ratios are higher in suspended material than the bed suggesting
Pb is either released from the sediment or actively accumulating
on suspended material. Elsewhere metal-Fe ratios of the central
and lower Bay are much larger than in the northern Bay (Figs. 20,
21 and 22). With distance along the Bay length and from cruise
to cruise, the ratios are highly variable. It is no wonder metal-
metal correlations in suspended material from this zone are scant.
Because organic content of suspended material is relatively high
in the zone (Fig. 3C), it seems likely the high variations relate
organic detritus or plankton and their degradation products.
ENRICHMENT FACTORS
To organize the metal data for use as indicators of contami-
nation, enrichment factors are derived by establishing baseline
levels from standard crustal values of Turekian and Wedepohl (39),
Both crustal values and observed values were normalized to Fe.
Iron was used for the same reasons as noted earlier for Fe ratios,
By ratioing Fe in shale to Fe in Bay sediment, and also the
concentration of metal in shale, an "expected" value for Bay sedi-
- 69 -
-------
SEAWARD CHANGE IN METAL/Fe RATIOS
NEAR-BOTTOM SUSPENDED MATTER
240 200 ISO 120 80 Of) 0 K
n CRUISE i
• CRUISE 2
A CRUISE 3
O CRUISE 4
a
B
C
® ® © ©
STATION NUMBER
-*- UPSTREAM (km)
Figure 20.
Metal-Fe ratios of near-bottom suspended matter along
the Bay length; (A) Cu/Fe; (B) Pb/Fe; (C) Zn/Fe.
- 70 -
-------
SEAWARD CHANGE IN METAL/Fe RATIOS
MID-DEPTH SUSPENDED MATTER
320 280 240 200 160 120 80 40 0 krr
B
DCRUISE 1
A CRUISE 3
O CRUISE 4
320 280 240 200 ISO 120 30 40 0 km
©@
STATION NUMBER
UPSTREAM (km)
Figure 21.
Metal-Fe ratios of mid-depth suspended matter along
the Bay length; (A) Pb/Fe; (B) Zn/Fe.
- 71 -
-------
SEAWARD CHANGE IN METAL/Fe RATIOS
SURFACE SUSPENDED MATTER
320 280 240 200 160 120 80 40 0 kir
C5©® -5
048 n
| D CRUISE !
• CRUISE 2
A CRUISE 5
040-j O CRUISE •!
Figure 22.
D CRUISE
• CRUISE 2
A CRUISE 3
O CRUISE 4
320 280 240 200 160 120 80 40 0 Km
®© STATION NUMBER
-•-UPSTREAM (km)
Metal-Fe ratios of surface suspended matter along
the Bay length; (A) Cu/Fe; (B) Ni/Fe; (C) Pb/Fe,
- 72 -
-------
ment is derived. A metal is taken as enriched if the observed
concentration exceeds the expected value. A factor of one implies
no enrichment relative to crustal values. The relation is sum-
marized as:
sediment
ex/Fe) shale
where */Fe is the ratio of concentrations of metal * to Fe in the
sediment and in the shale.
The advantage of a geochemical baseline level is that it pro-
vides a standard for comparing data throughout the Bay, and the
Bay to other systems. It assumes a uniform crustal average
throughout the region and that the Chesapeake drainage basin is
representative of average crust. Consequently, it does not
account for local metal variations. When different systems are
compared, it assumes the metal analysis are of comparable
analytical quality. Because the method is chemical, it is
independent of sediment physical properties like particle size.
It is affected, however, by compositional changes such as
varying organic content. Therefore, interpretation of "excess"
metal as anthropogenic in organic rich suspended material is of
limited validity since organisms are often naturally enriched.
For fluid mud and bed sediment, the expected metal content
of Bay sediments, derived from Fe corrected average shale, is
illustrated for each metal and station in Appendix 7. Of note,
observed values of mean As, Hg and Sn are less than expected,
- 73 -
-------
or deficient, throughout the Bay while Cu and Ni are normal in
the northern Bay but deficient in the central and lower Bay. By
contrast, observed Pb departs from baseline values seaward to
station 8 with distinctly higher enrichment factors in the
northern Bay reaching 4.6 at station 14 (Fig. 23A). A similar
trend is evident for Zn which reaches a peak of 6.3 at station
16. Factors for Cd are variable but Mn is distinctly enriched
in the northern Bay, stations (12-19). Therefore, Mn, Pb and
Zn reflect major human sources in the Baltimore-Susquehanna River
area. Enrichment factors for the Susquehanna suspended load are
Mn, 7; Pb, 7; and Zn, Tables 8 and 11, (9) which are about the
same as in the northern Bay. Therefore, northern Bay fluid mud
and bed sediment, which is primarily supplied from the Susquehanna
(12), is not notably enriched in Mn, Pb and Zn from additional
sources as Baltimore Harbor.
For suspended material, the expected metal content of Fe
corrected average shale is illustrated for each metal and
station in Figures 6 and 7. In near-bottom suspended material,
from the central Bay, stations 8-11, Cd, Cu, Pb and Zn depart
substantially from Fe corrected average shale. Factors for
mean concentrations range 8 to 33 for Cd, 6 to 9 for Cu, 6 to
13 for Pb, and 9-13 for Zn. Factors are higher in the central
Bay than farther seaward or landward except for Mn and Pb that
are slightly greater in the northern Bay than in the central Bay.
- 74 -
-------
ENRICHMENT FACTORS
UJ
STATION
c 19181716 1413 12 II 10 9 8 7 6 5 21
5
4
3
2
1
0
i >ii-.,''i i >i i i i 1 1 1 — i
o.o
1 \
l\ A BED SEDIMENT AND
/ 1 Q A. FLUID MUD
I 1 / (•)
e\ ^°\J' \
\\ It Vs*^ * • rtj P |\
\lj A-*^_© -^.f\ ^^^
0 v. t3 — -©
J^ ~ ft — N y*.
--^V / N *******cd ------
%_---• • "*'•-•
T 1 1 1 r 1 1 1 1 | 1 | 1 1 1 1
t,
V)
UJ
0
x. i-
Uj Z
UJ
o
u_
UJ
i
320 280 240 200 160 120 80 40 0
DISTANCE, km.
LEAD - f /
. 5.' . «e /
1 / •
2
' ' 10
/ ' I-
'/ II, . '
/ • Central and
/ '• .I2. Lower Bay
./
..• / /
.-.-' /'/''Northern
/„ / . .••' Bay
•/..••
, i i i i i...
30
20
OL
O ?
H —
O
U^ I0
H 8
Z
UJ e
•5
X 5
— 4
o: H
^^
UJ 3
2
. • ' -8
r
•^ COPPER :9 '*'-.
r
Central and';5 />10'.
Lower Bay z •" '
*
/ '
13 *
/ *I2'..|
/
••/••
.15.' / V
22;' / .-•'
.-\*,/.n/ Northern
*-/..••' Bay
i " i i i i i i
10
20 30 40 50 60 70
ORGANIC MATTER, %
80
10 20 30 40 50 60 70
ORGANIC MATTER, %
Figure 23.
Variation of enrichment factors: (A) For Cd, Pb and
Zn in bed sediment and fluid mud along the Bay length;
(B) Lead enrichment factors versus percent organic
matter for surface suspended material; (C) Copper
enrichment factors versus percent organic matter for
surface suspended material. Numbers represent station
numbers.
80
- 75 -
-------
Departures from Fe corrected average shale for surface sus-
pended material are much higher than in near-bottom suspended
material (Figs. 6 and 7). In particular, Cd, Cu, Pb and Zn are
higher in the central Bay, stations 5-10, than elsewhere. These
compare with near-baseline values for As, Ni and Sn in the
northern Bay. The high central Bay departures are indicative
of high enrichment. Factors range 10-118 for Cd, 12 to 27 for
Cu, 37 to 51 for Pb and 16 to 74 for Zn. The large departures,
high factors and variability relate to the high percentages of
organic matter in the central Bay, especially in surface water,
Figure 3. This trend is confirmed by graphs, Figures 23B and
23C, whereby enrichment factors for Pb and Cu increase with an
increase of percent organic matter. The trend is linear for
northern Bay stations 13-22, suggesting a detrital source of
both metals and organic matter. Values for the central and lower
Bay (stations 1-12) with relatively high factors, high organic
content and substantial scatter, can be produced by metabolism
of plankton. Whatever the cause, the relationship differentiates
two distinct sub-groups of factors throughout the Bay, those
from a northern zone and those from the central-lower zone.
Although high organic content of central and lower Bay
surface samples precludes use of a Fe-corrected average shale
baseline as an indicator of anthropogenic sources, it is useful
to gain an estimate of relative enrichment by comparing observed
metal concentrations with those of oceanic plankton from
- 76 -
-------
uncontaminated areas. Table 10 shows that metal content of Bay
water exceeds the content of both phytoplankton and zooplankton
more than 9 times for Cd and Zn, more than 19 times for Ni, Cu
and Pb. Therefore, the impact of human metal input, whatever
its source, is affecting Bay suspended material on a regional
scale.
TABLE 10. METAL CONTENT OF AVERAGE MARINE PLANKTON
ON A DRY WEIGHT BASIS, yg/g
Chesapeake Bay
Central & Lower
Stations 6-11, Oceanic Oceanic
Metal mean surface Phytoplankton Zooplankton
Cd 26.8 2.I3 1.9-2.9"
Cu 225 7.I3 7.5-8.9"
Mn 2300 8.51 1.1-7.82
Ni 150 3.03 2.8-7.8"
Pb 210 4.03 1.2-8.5"
Zn 1300 383 86-135"
^rom Bostrom, et al. (40).
2From Forstner and Whitmann (13).
3From Forstner (41).
"From Trefy and Presley (42).
When enrichment factors of Bay bed sediment are compared
to other coastal systems, Table 11, it is noted that northern
Bay sediment is enriched with Mn, Pb and Zn to a lesser degree
than the Hudson and Delaware Estuaries but mainly more than
- 77 -
-------
San Antonio Bay and Galveston Bay. Mn is higher in the Chesapeake
than elsewhere. In suspended material, enrichment factors for
Cd, Pb and Zn are higher than the Rhine and all other areas com-
pared, despite greater industrialization of other areas. This
trend probably reflects greater planktonic production of the
Chesapeake Bay.
- 78- -
-------
c
N
kO ^ VO 00
• • t •
oo H oo H ^r o
co oo co
co
o m r~ r-
• • • •
rH O O O CN
oo
oo oo
rH 00
EH
co
rH O\
rH H ro
oo
a a
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- 79 -
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TEMPORAL VARIATIONS AND LONG-TERM CHANGES
Samples collected approximately bi-weekly by the U.S.
Geological Survey at Conowingo dam on the Susquehanna River
during 1979-1980 show that concentrations of Fe and Mn (weight
per volume) generally vary with variations of total suspended
material and with river inflow. As shown in Figures 2 and 24,
concentrations of suspended Fe at high inflow are more than
20 times the concentrations at low inflow while corresponding
suspended Mn is more than 15 times. Similar data obtained by
Carpenter (9) in 1966 suggest that other metals may follow
these trends, however, there are exceptions. The metal Mn
for example, exhibits marked seasonal changes in partitioning.
Suspended Mn is more dominate than soluble Mn in spring, summer
and fall, a trend associated with influx of decaying organic
matter in winter (9). It seems likely that seasonal changes
in metal content (weight per volume) occur in the turbidity
maximum zone seaward to Tolchester (station 14). The reason
for this is that the metal-sediment concentration relation,
e.g. for Fe, Figures 8A, 8B, for Susquehanna samples persists
in the turbidity maximum zone (e.g. Fig. 8A). By contrast, Zn-
suspended sediment values (Fig. 8B) display substantial scatter
in the turbidity maximum and depart from the linear trend of
Fe, a trend suggesting chemical or biological changes in the
Bay. Eaton (10) shows relatively constant Fe concentrations in
surface water and similarity to Susquehanna concentrations
- 80 -
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A.
iO-i
X!03
mVs
4
2-
RIVER DISCHARGE
l2-8 SUSQUEHANNA
TIME
SERIES
LONGITUDINAL SECTIONS
IRON,
SUSPENDED
4700
TOTAL
800-
#g/i '
600-
400:
200 :
MANGANESE
—Y—T^TT
i—r™i
iJFMAMJJASOND'JF
i 1979 I 1980
r~ i i
A Mi
Figure 24.
Temporal variations of: (A) Susquehanna River inflow
at Conowingo; (B) Iron concentrations; and (C) Mn
concentration during 1979-80. Data from U.S.G.S. (21)
- 81 -
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extending 60-80 km seaward from the river (vicinity station 13
of this study). Farther seaward, however, changes relating to
fluctuations of river inflow were not observed in this study.
When metal content (weight per volume) of samples collected
at contrasting conditions of neap and spring tides is compared
(21), e.g. cruise 3, August 6-11 (spring) and cruise 4, August
27-30 (neap), differences are evident in the zone of the tur-
bidity maximum. River inflow during these periods was low and
relatively constant. For example, Cd, Pb, Mn and Zn are more
than 3 times greater at spring tide than at neap tide. This
increase relates to the greater amount of suspended material
at spring tide created by high bed resuspension. Elsewhere,
the differences are very small or indeterminate because metal
content varies widely.
Metal concentration differences associated with contrasting
oxygenated and anoxic water are exemplified by data from cruise
2, May 2-10 and CBI cruise 9, June 4-6, 1979. When near-bottom
waters changed from oxygenated (2-5 ppm dissolved oxygen) to
nearly anoxic (less than 1 ppm), the Cd, Cu and Pb content
(we. per we.) increased more than 2-fold whereas the Mn content
diminished by more than 3-fold. The latter change is partly
confirmed by lower Fe/Mn ratios that diminish 2 to 8 times
suggesting a loss of particular manganese relative to iron.
Presumably the manganese is reduced and released into its
dissolved state.
- 82 -
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Seasonal differences from late spring (cruise 9) to summer
(cruises 3 and 4) are revealed by vertical profiles for Cu and
Pb, Figure 25. In late spring, a time of plankton blooms and
relatively high chlorophyll a content in near-surface water,
the concentrations of Pb and Cu (we. per we.) are about 2 times
greater than in early August, cruise 3. A further reduction is
noted near the surface in late August, cruise 4.
By integrating the monthly data for total suspended material
collected and analyzed by CBI with those collected by VIMS using
similar techniques during 1979-80, an annual cycle of changing
suspended concentrations is revealed. As shown in Figure 26,
greatest concentrations occur in the northern Bay landward of
stations 858C or 12, during Jan.-April, a period of high river
inflow (Fig. 2). Mid-depth concentrations in this zone, i.e.
greater than 40 mg/1, persist throughout the year. Note that
these concentrations are largely greater than farther landward
near the river source. Concentrations in the central Bay are
relatively low throughout the year. Surface values ranged 1.0
to 6.7 mg/1 and mid-depth, 1.0 to 7.0, with higher concentra-
tions in early May than at other times. Most of this material
consists of organic matter produced by plankton. Near the Bay
mouth, a localized aureole of 40-100 mg/1 is noted, Oct.-Nov.,
1978, as also a zone greater than 10 mg/1 between Dec. and May.
Organic matter is low to moderate and there are no other
sources of fine sediment except from the Bay floor. It is
likely that these concentrations result from bed resuspension.
- 83 -
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SEASONAL CHANGES
20-
30 -
20-
30-
500 1000
J_
JUNE 4-6
500 1000
200 400
I I
0 200 400
JUNE 4-6
0 200 400 600
I j i
AUGUST 6-11 .
AUGUST 27-30
C". M.g/g
AUGUST 6-11 _
AUGUST 27-30
25. Vertical profiles of Pb (upper) and Cu (lower) content
illustrating changes in near-surface water of the central
Bay from late spring to summer. June 4-6, CBI station 843F;
Aug. 6-11, VIMS station 12, cruise 3; Aug. 27-30, VIMS
station 12, cruise 4.
- 84 -
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TOTAL SUSPENDED MATERIAL, mg/l
CBI
CRUISE NO. I
SUS F
12 _ _
40
80
120
160
200
240
280
320
UJ
X
I
o
a.
o
-------
When these distributions are compared with a similar set of
data for 1969-70, reported by Schubel and Carter (1), it is evident
that the turbidity maximum has an increased load and is more per-
sistence in 1978-79. Additionally, the 10 and 20 mg/1 isopleths
extend about 80 km farther seaward between the months of September
and March. River inflow during the 1969-70 period averaged 1020
m3 per sec while during the 1978-79 period it averaged 1280 m3 per
6
sec. Sediment influx for 1969-70 averaged 1.0710 metric tons
however, comparable data for the complete 1978-79 period are not
available, at least from U.S.G.S. It can be inferred from the
inflow data that 1978-79 was not an unusual year for sediment
influx and probably followed inflow levels for 1978-79 which were
close to the long term average, 985 m3 per sec.
In summary, the largest temporal variations are produced by
seasonal changes in river inflow and organic accumulation in
near-surface water. River inflow produces variations mainly in
near-river reaches and together with spring-neap tidal resuspen-
sion, it secondarily affects the turbidity maximum zone. Summer
anoxic of near-bottom water in the central Bay produces chemical
conditions favoring release of Mn, while late spring plankton
blooms in near-surface water favor bioaccumulation of Cu and Pb.
- 86 -
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SECTION 7
IMPLICATIONS OF RESULTS
SIGNIFICANCE OF FLUID MUD AND SUSPENDED MATERIAL
Suspended material does not settle directly to the bed but
undergoes repeated cycles of resuspension and settling. Over the
long-term, net downward movement leads to a loose watery structure
of dense suspensions with high concentrations in the range 10-480
g/1. Vertical concentration profiles display a sharp change at
about 5-20 g/1 and form a high vertical gradient or interface.
This is commonly taken as the mud-water interface. Although the
concentration gradient is stratified, turbulent stresses of
currents and waves can make the interface unstable, especially
during storms. As a result surface mud is mixed with overlying
water, affording an opportunity for chemical exchange and
migration of constituents. Examples of fluctuating sediment
concentration and metal content relating to resuspension and
settling are provided in the section, tidal time series. These
data show that fluid mud and suspended material are interrelated
through dynamic processes.
Sediments that accumulate in the form of fluid mud are
important for a number of reasons. First, they tend to
accumulate in less energetic parts of the Bay, the axial basin,
- 87 _
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harbors, backwater embayments and the shipping channel floor.
These zones are also favorable for accumulation of metals because
they tend to have high clay content, substantial organic content
and they are fine-grained. Additionally, they are zones of
relatively fast deposition. High water content is maintained
in the mud when the rate of deposition exceeds the rate of
consolidation, a process that results in dewatering of the
sediment. Because the mud accumulates at relatively high rates,
it is more sensitive to metal inputs than non-fluid mud sediment.
As shown for Kepone contaminated sediment (43), fluid mud'was
contaminated first, and it was also decontaminated first after
input was arrested.
Fluid mud is important from the physical viewpoint because
it fills shipping channels and harbors, and thus necessitates
frequent dredging. In turn, disposal sites are required for
placement of material in a watery state. This state is conducive
to dispersal of large masses of material as mud flows and it is
a poor substrate for benthic organisms. Commonly, more than 95
percent of the sediment mass discharged from an open water dredge
pipe is in the form of fluid mud; only a small percent is released
as suspended sediment into the water.
From the geochemical viewpoint fluid mud is important because
its metal content (we. per vol.) is much greater than in suspended
material. For example, at station 13 with a mean water content
of 369% wet weight and mean bulk density (dry weight) of 1.19 g/cc,
- 88 -
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the equivalent sediment concentration is 300 g/1. The mean metal
content of Pb in the mud is 59.8 yg/g which exceeds that in over-
lying water (30 cm above the mud-water interface) averaging
3.46 ug/1 by 5,200 times.
Natural accumulations of fluid mud can move either by erosion
of the surface and resuspension as suspended material in the water
column or as sheets and mud flows along the bottom. Although our
multi-frequency acoustical equipment (at 22.5 and 200 kHz) defined
numerous fluid mud layers, its possible movement as sheet flows
less than 10 cm thick could not be detected within limits of
equipment resolution. Additionally, movement could not be measured
by Marsh-McBirney electromagnetic current meters within 6 cm of
the mud-water interface because of interference produced by
vertical stratification of the mud and suspended material. None-
theless, X-ray radiographs of fluid mud box cores often display
a fine structure of flaser-like bedding indicative of deposition
from very high suspended loads. Because fluid mud bears a very
high metal content (we. per vol.) the proportion of metals
transported by the mud could be significant. The long-term
stability and possible episodic movement during storms remains
to be observed and understood.
PATHWAYS
Metals can be transported from their source to their sink
along two principal pathways: (1) a hydrodynamic route; (2) a
bioecological route. The probable hydrodynamic routes are
- 89 -
-------
sketched from: (1) direct current measurements with suspended
material and metal content at four anchor stations in the turbidity
maximum zone; (2) dispersion patterns of metal content in sus-
pended material, fluid mud and bed sediment.
When metals enter the Bay with suspended sediment, which is
released by natural soil erosion or discharged directly into the
Susquehanna River in contaminated effluents, it is transported
seaward through the freshwater reach of the Bay head. In this
zone, it is diluted, dispersed by diffusion and advection and
%
mixed with less contaminated suspended material. These processes
act to reduce the initial metal concentrations. Transport in
this reach is probably a transit process whereby much sediment
and metals are moved quickly during short periods of high inflow
and very slowly during long periods of moderate to low inflow.
As suspended material is flushed seaward into the fresh-salt
transition, its seaward movement slows and much suspended material
is trapped near the bottom in the null zone or convergence of
seaward flowing river water and landward flowing salty Bay water.
Some material, the clay size material and less dense organic material
that stays in suspension in upper parts of the water column, can
move farther seaward through the upper layer of the estuarine
circulation. However, in seaward areas some of this material may
settle, aided by particle agglomeration, and become entrained in
the landward moving lower layer. When this material approaches
the inner limit of salty water, transport is retarded because the
- 90 -
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net flow in this zone approaches zero. For material that settles
faster than it is mixed upward by turbulence and salt exchange,
there is net accumulation on the bed. But material that remains
in suspension for long periods can be mixed upward and recycled
seaward in the upper layer. Chemical changes are superimposed on
physical transport whereby Fe and Al for example can precipitate
while metals in solution can be adsorbed. In contrast, if river-
borne metals remain in solution or are desorbed, they likely flush
through the convergence zone in the upper layer. They can escape
the Bay through the upper layer or be taken up by plankton and
then consumed by fish.
Seaward transport routes through the central Bay is revealed
from metal patterns (44) showing transport is more effective
along the west side of the Bay. This is also a greater potential
source of contaminates compared to the east side, but the route
is compatible with the salinity regime and the path expected from
the estuarine circulation.
Landward transport through the lower Bay is indicated from
metal distributions of chromium (44) which extend landward from
the Bay mouth along the eastern side. It seems likely that this
transport extends farther landward through the lower estuarine
layer of the central Bay. Figure 27 summarizes schematically
probable hydrodynamic transport routes in relation to accumulation
zones.
Relationships between sources of metals and accumulation
zones are clearly complex. Not only are the sources unknown
- 91 -
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BALTIMORE :'•
/ • ^
ACCUMULATION TRANSPORT
ZONES ROUTES
Primary 1*^ Upper Layer
Secondary *^^ Lower Layer
B Bed
S Surface
ACCUMULATION
AND
TRANSPORT PATTERNS
NORFOLK
27.
Schematic diagram showing primary and secondary zones of
metal accumulation in fluid mud, bed sediment and
suspended material. Arrows represent likely transport
routes.
- 92 -
-------
according to metal species or metal ratios, but the extent to which
a measured concentration reflects natural and human sources in
runoff as distinct from metal fluxes produced in the water by bio-
accumulation or by resuspension from the bed (recycled) is unknown.
Figure 28 provides a schematic and over-simplified representation
of likely paths of a metal supplied from a major fluvial source
like the Susquehanna.
METAL PATHWAYS
SOURCE
SOLIDS
COLLOIDS
^SOLUTION
11111 ii 11 ((111 ii r i f (n i s it 11111 it t nn i
FRESH-*-SALf
illllmiiiiiiiiiimiiiiimimiuill
DESORPTION
DILUTION
DISPERSION
PLANKTON
SEA
SUSPENSION
FEEDERS
SEDIMENT
SINK
Figure 28. Schematic diagram illustrating the likely pathways of
metal cycling in the Bay.
Metals adsorbed to suspended material can enter the bio-
ecological paths via suspension feeders, bacteria, plankton and
- 93 -
-------
fish. Once settled to the bed, sediment can be consumed by deposit
feeders and their excretion products can be resuspended. The bio-
ecological paths are complicated because organisms can extract
metals from both dissolved and particulate states, either natural
or anthropogenic. Consequently, it is difficult to predict a
metal's ultimate destination.
- 94 -
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MANAGEMENT STRATEGIES
Since the initial aim of the Chesapeake Bay Program was to
provide a scientific basis for managing the Bay, strategies are
offered for control of potentially toxic metals and associated
fine-grained sediment. It is assumed that effective management
aims to regulate the input of toxics from all sources in order
to keep concentrations in the Bay below the level at which
adverse impacts occur (3). This effort is designed to protect
the Bay and to maintain it in its best achievable condition.
The chief strategies are:
1. Manage the Bay as a single entity. This project views
the Bay like a great reaction vessel in which water,
sediment and metals from different sources are mixed,
exchanged and cycled along different pathways. These
features, together with the physical, chemical and
sedimentological continuity of the Bay,foretell that
piecemeal management or treatment of single components,
cannot succeed. The Bay must be managed as a whole
system. Because metals, sediment and organic matter
are interrelated, they need to be managed together.
Therefore, effective management should treat the Bay
in terms of the whole problem rather than piecemeal
subportions.
2. Manage the Bay together with its watershed and margins.
This requires a region-wide managerial network
embracing drainage basins, shorelines and the Bay
itself. Natural geochemical processes do not
recognize political or jurisdictional boundaries.
Most toxic problems begin on land and in upstream
areas, so any management structure for the Bay
should be integrated with upland and shoreland
counterparts.
3. Manage metals and sediments at their source. Dis-
charge of metals via industry and sewage are assumed
detrimental and should be controlled pursuant to
Federal and State policy. Priority should be given
given to those metals that (1) accumulate in the Bay
at levels above natural occurrence like Cd, Cu, Pb
and Zn; (2) pose an unacceptable risk. For
_ 95 -
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contaminated sediment already in the drainage system,
focus attention on sediment accumulated behind dams.
This is subject to catastrophic release by floods.
For nonpoint sources, the appropriate approach is
through control of land use, agricultural, residential
and commercial. A current inventory of metal input
locations,composition of effluents and rates of
discharge, including airborne and seaborne (via spills)
inputs, would greatly assist in assessing metal loading
in the Bay.
4. Manage for long-term control, subtle changes and far-
field effects. Most control measures have focused
on near-field discharges and immediate effects. This
study points to the importance of "far-field" effects
and to the significance of Bay processes in accumu-
lating metal concentrations higher than near the
sources. Processes of bioaccumulation and particle
concentration in the turbidity maximum, should be
included in any effective management plan. For
example, since the turbidity maximum is controlled
by hydrodynamics and resuspension, its position and
intensity could be manipulated by controlling river
inflow and by stabilizing the bed.
Because sediment has a relatively long residence time
in the Bay, a feature that can lead to long-term
ecological exposure, management plans should include
long-term effects of metals at sublethal concentra-
tions, especially with regard to cumulative effects
of many contaminants.
5. Manage with a fix on the metal speciation or chemical
form, its toxicity and association with sediment
characteristics. For example, dissolved metals and
organic bound metals as released in sewage, are
subject to widespread dispersal and a short residence
time in the Bay. Organic matter not only settles
slowly, but is subject to mobilizing metals (into
solution) when it decomposes. Dissolved metals might
be better discharged into rapidly flushed surface
water where they could be swept to sea rather than
discharged into sluggish bottom water with a muddy
bed where they can be adsorbed onto fine sediment
and migrate landward. Dissolved fractions are
readily taken up by plankton whereas particulate
fractions are likely to be consumed by benthic filter
feeders.
- 96 -
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6. Manage with a scientific data base. Because the Bay
system is complex,it requires a fairly sophisticated
input of technical information about the system being
managed. It requires detailed information about the
nature of processes, the norms and symptoms of loadings,
perturbations and carrying capacities. Consequently,
any effective management structure should be coupled
with monitoring and basic science.
- 97 -
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MONITORING STRATEGIES
The purpose of monitoring is to provide a systematic way to
detect the input of potentially toxic metals before they build up
to hazardous levels. Monitoring should serve as an early warning
of danger to man or to a specific resource so that protective
actions can be taken. Additionally, monitoring should enhance
our quantitative knowledge of the Bay environment, including the
ecological balance, as a basis for managing marine resources.
The chief questions for toxic metals are: What are the input
concentrations and rates? What concentrations accumulate in the
sediments relative to natural concentrations? Are these accumu-
lations a function of input rates? At present the quantitative
relationship of metal concentrations in sediments to accumulation
in particular organisms, communities or resources and their
toxicity, is unknown. Until this information is available, it
may be possible to rank the metals according to their relative
risks or potential hazards following procedures of Hakanson (45)
and O'Connor and Stanford (46). Alternately, the monitoring
effort can be keyed to meeting some water quality standard yet
to be defined. In brief, the initial strategy is to key the
monitoring to specific objectives or problems.
To translate the objectives into quantitative terms, it is
necessary to measure the concentrations of target metal(s) pre-
sent in a particular state (dissolved or particulate) and in a
- 98 -
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particular area(s) of interest that relates to their sources or
sinks. Moreover, it is necessary to detect changes in metal
loading with time.
Time-series observations are an important approach because
toxic inputs are highly variable. They vary with runoff, with
sediment influx and with varying discharge of contaminate
effluents. As shown in previous sections, metal concentrations
of the Bay can vary with the tide, with dispersion or accumulation
rates and with seasonal changes in organic loading. Consequently,
monitoring should cover a wide range of time scales. These
should be sufficient to establish long-term trends, determine
norms and differentiate perturbations as well as a gradual
build-up.
Monitoring can be organized into source and sink modes.
Spatial and temporal design of each mode should be compatible
to allow mutual manipulation and interpretation of data. Source
areas of the watershed can be monitored effectively from several
key stations on,or near,the fall line. This is demonstrated by
water quality stations occupied by U.S.G.S. (23) at Conowingo,
Chain Bridge and Cartersville, which monitored over 75 percent
of the watershed area. The data include important metals in
several chemical forms, together with important hydrologic data,
water quality and suspended sediment concentrations. However,
the frequency and number of metal samples is generally limited
to less than six per year. They include samples during periods
- 99 -
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of high inflow and high sediment influx and high metal loading,
but they are too sparse to determine the annual mean, minimal
values, seasonal trends and response in the Bay. By monitoring
point sources of effluent discharges, it may be possible to
identify a problem early, or before large amounts of toxics
are discharged into the Bay. Monitoring design for point source
effluents should follow results of the forthcoming toxic source
assessment research. Monitoring of direct discharges, however,
may not detect low concentrations of metals that can build up
to high levels in the Bay if accumulated by sedimentary processes
or by organisms.
For monitoring sediments, a simple strategy is to sample the
upper \ cm of fluid mud from sinks or zones of fast deposition.
These zones, especially those having clay size sediment, are
more sensitive to contamination than other zones and thus pro-
vide an early warning of increasing loads from multiple sources.
Experience with Kepone contamination (43) showed zones of fast
deposition were contaminated first; they also decontaminated
first after discharge stopped. Such zones can be located
from the history of bathymetric changes and may include deeper
parts of tributary mouths, the turbidity maximum, sides of deep
basins and dead-end reentrants of shipping channels or anchorages.
Freshwater areas near rivers should be avoided because they are
subject to flooding and alternate scour and fill. Temporal changes
- 100 -
-------
can be revealed by sampling surface fluid mud 2 to 6 times per
year depending on deposition rates. Changes in surface sediment
can be confirmed by analyzing sediments with depth in cores. A
change in concentration as a function of depth implies a change
in the rate of cumulative loading, though the sources may not
be known. The advantage of this strategy is that it provides
maximum data integrated over a time scale of days or months,
from relatively few samples. As with any monitoring effort,
the replication and representativeness of sampling procedures
must be established. Particle size effects should be normalized
by analyzing sediment fractions less than 16y. Because metals
associate with one another, as shown in the section "Metal
interactions and correlations", key metals can be selected and
used as surrogates. After samples are analyzed, they should be
stored frozen for reference or used as future needs dictate or
as instrumentation improves.
- 101 -
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RESEARCH NEEDS
The Chesapeake Bay is a very complex estuarine system and
our knowledge of hydrodynamic sedimentological and bioecological
processes is limited. The knowledge gained in this study can be
valuable for predicting some effects of toxic introductions, but
it is not sufficient. This study uncovered a number of problems
that deserve future research.
1. Since results show maximal concentrations of abnormally
high Cd, Cu, Pb and Zn in surface water of the central
Bay, a location far from major sources, it remains to
determine how they get there. The distribution of
metal in various states must be determined together,
i.e. dissolved, colloidal, particulate; organic or
inorganic; to demonstrate how are the metals
partitioned. It remains to learn if metals stimulate
production of organic matter like plankton, or by
contrast, affect the health of organisms in the central
Bay. And, does bio-accumulation and turnover make the
metals more, or less, mobile?
2. Metal-organism interactions (suspended) need to be
observed seasonally together with nutrients. Further-
more, laboratory experiments utilizing stable and
radioisotope tracers are needed to trace changes in
metal distributions between water, suspended sediment
and organic material with and without certain bacteria,
organic chelators, etc. Additionally, what is the
bio-availability of sediment-bound metals?
3. Although the bed is generally assumed to represent
a sink for metals and suspended material, this study
shows that the bed is dynamic and can also be an
important source of suspended material. By repeti-
tive resuspension, metals can be mixed and exchanged
with overlying water and suspended material. It
remains to discover what metal-sediment interactions
take place as resuspension exposes sediment to alter-
nate chemical conditions between the bed and water,
e.g. from anoxic to aerobic conditions. What metals
are mobilized, or stabilized, by long-continued
resuspension? An understanding of these affects is
important to evaluating chemical changes induced by
dredging.
- 102 -
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4. Whereas this study has dealt mainly with metals supplied
to the Bay continuously or periodically, episodic events
may control their distribution. Floods, hurricanes and
storms can produce exceptional conditions for massive
resuspension and dispersal of sediment-borne metals.
Observations are needed to study the impact of short-
term events with respect to: How much sediment and
metal is released or mobilized by an event compared to
average conditions? What are the corresponding effects
on marine resources? What is the sediment and chemical
composition of material supplied in different propor-
tions, i.e. river input versus local resuspension? How
long does it take to recover, decontaminate or come to
a new chemical equilibrium?
5. Since this study reveals that the metal content of Bay
suspended material is highly variable to ascertain the
validity data acquired, future efforts should account
for variability in a rigorous statistical sampling plan.
In particular, long-term monitoring is needed to dis-
tinguish short-term period (tidal) variations and
nonperiodic events (storms) from fortnightly, seasonal
and yearly changes. Monitoring is needed of source
inputs and key points in the Bay at the same time.
6. Much work needs to be done on the transport link between
sources of suspended material and toxics in the tribu-
taries and major zones of accumulation in the central
Bay. In particular are the tributaries acting as a
source of metals or, by contrast, are they primarily
a sink for material supplied from the Bay via landward
flow through the lower layer? It is necessary to
establish the source "end-members", or compositional
tracers in the Bay and the tributaries, and then to
determine their mixing ratios that affect the concen-
tration of particle-associated metals.
7. A basic goal of estuary studies is to develop practical
models, either numerical or hydrodynamic, of circulation
and sediment transport that can be used for predicting
effects of introducing metals, their routes and rates
of transport, their discharges at different locations,
and effects of river diversions, and varying geometry
as channel deepening on transport routes.
- 103 -
-------
SECTION 8
REFERENCES
1. Schubel, J.R., and H.H. Carter. Suspended Sediment Budget
for Chesapeake Bay. In: Estuarine Processes, M. Wiley,
ed. Academic Press, New York, 1976. Vol. 11:48-62.
2. Helz, G.R. Trace Element Inventory for the Northern
Chesapeake Bay with Emphasis on the Influence of Man.
Geochimea et Cosmochimica Acta, 40:573-580, 1975.
3. Bricker, 0. Toxic Substances in the Chesapeake Bay
Estuary. Unpublished Manuscript. U.S. Environmental
Protection Agency, Chesapeake Bay Program, Annapolis,
Md., 1981. 16 pp.
4. Turekian, K., and M. Scott. Concentrations of Cr, Ag,
Mo, Ni, Co and Mn in Suspended Material in Streams.
Environmental Science and Technology, vol. 1:940-942,
1967.
5. Huggett, R.J., R.M. Block, 0. Bricker, T. Felvey, and
G.R. Helz. Workshop Report on Toxic Substances. In:
Proceedings of Bi-State Conference on Chesapeake Bay,
Chesapeake Research Consortium, 1977. Publication No.
61:121-127.
6. Toxic Work Group. Plan of Action for Accumulation in
the Food Chain. Unpublished Manuscript. U.S. Environ-
mental Protection Agency, Chesapeake Bay Program,
Annapolis, Md., 1978. 23 pp.
7. U.S. Environmental Protection Agency. Synthesis Report
for Toxics, Forthcoming.
8. Troup, B.N., and O.P. Bricker. Processes Affecting the
Transport of Materials from Continents to Oceans. In:
Marine Chemistry in the Coastal Environment, T.M. Church,
ed. ACS Symposium Series 18, American Chemical Society,
Washington, D.C., 1975. pp. 133-151.
9. Carpenter, J., W.L. Bradford, and V. Grant. Processes
Affecting the Composition of Estuarine Waters. In:
Estuarine Research, L.E. Cronin, ed. Academic Press,
New York, 1975. Vol. 1:188-214.
- 104 -
-------
10. Eaton, A., V. Grant, and M.G. Gross. Chemical Tracers for
Particle Transport in the Chesapeake Bay. Estuarine and
Coastal Marine Science, 10:75-83, 1980.
11. Schubel, R.J. Distribution and Transportation of Suspended
Sediment in Upper Chesapeake Bay. In: Environmental
Framework of Coastal Plain Estuaries, B.W. Nelson, ed.,
Geological Society of America Memoirs No 133, 1972,
pp. 151-167.
12. Biggs, R.B. Sources and Distribution of Suspended Sediment
in Northern Chesapeake Bay. Marine Geology, 9:187-201,
1970.
13. Forstner, V., and G.T.W. Wittmann. Metal Pollution in the
Aquatic Environment. Springer-Verlag, Berlin, Heidelberg,
New York, 1979. 488 pp.
14. Sommer, S.E., and A.J. Pyzik. Geochemistry of Middle
Chesapeake Bay Sediments from Upper Cretaceous to Present.
Chesapeake Science, 15(l):39-44, 1974.
15. Strickland, J.D.H., and T.R. Parsons. A Practical Handbook
of Seawater Analysis. Bulletin 167. Fisheries Research
Board Canada, Ottawa, Canada, 1972. pp. 1-4.
16. Goldberg, E.D., M. Baker, and D.L. Fox. Microfiltration
in Oceanographic Research Marine Sampling with the
Molecular Filter. Journal of Marine Science, 11(2):194-
204, 1952.
17. U.S. Environmental Protection Agency. Methods for Chemical
Analysis of Water and Wastes. EPA-625/6-74-003, Washington,
D.C., 1974. 82 pp.
18. Bennett, C.A., and N.L. Franklin. Statistical Analysis
in Chemistry and the Chemical Industry. John Wiley and
Sons, Inc., New York, 1954. 724 pp.
19. Ostle, B. Statistics in Research (2nd ed.). Iowa State
University Press, Ames, Iowa, 1963. 584 pp.
20. Harris, R., M. Nichols, and G. Thompson. Heavy Metal
Inventory of Suspended Sediment and Fluid Mud in
Chesapeake Bay. VIMS, Special Scientific Report 99,
Virginia Institute of Marine Science, Gloucester Point,
Va., 1980. 113 pp.
- 105 -
-------
21. Nichols/ M., W. Cronin, and R. Harris. Water, Metals and
Suspended Material in Chesapeake Bay, June-August, 1979.
VIMS, Special Scientific Report 105, Virginia Institute of
Marine Science, Gloucester Point, Va., Forthcoming.
22. Nichols, M., G. Thompson, and R. Harris. Time Series
Observations of Suspended Material and Heavy Metals in
Northern Chesapeake Bay. VIMS Special Scientific Report
106, Virginia Institute of Marine Science, Gloucester
Point, Va., Forthcoming.
23. Lang, D.J., and D. Grason. Water Quality Monitoring of
Three Major Tributaries of the Chesapeake Bay - Interim
Data Report. USGS/WRI-80-78, U.S. Geological Survey,
Towson, Maryland, 1980. 66 pp.
24. Pritchard, D.W. Chemical and Physical Oceanography of the
Bay. In: Proceeding of the Governor's Conference on
Chesapeake Bay, Wye Institute, Md., 1968. pp. 11-49 -
11-74.
25. Stroup, E.D., and R.J. Lynn. Atlas of Salinity Distri-
butions in Chesapeake Bay 1952-1961, and Temperature and
Seasonal Averages 1949-1961. Graphical Summary Report
No. 2, Reference 63-1, Chesapeake Bay Institute of the
Johns Hopkins University, 1963. 410 pp.
26. Seitz, R.C. Temperature and Salinity Distributions in
Vertical Sections Along the Longitudinal Axis and Across
the Entrance of the Chesapeake Bay (April 1968 to March
1969). Graphical Summary Report No. 5, Reference 71-7,
Chesapeake Bay Institute of the Johns Hopkins University,
1971. 99 pp.
27. Van Valkenburg, S.D., J.K. Jones, and D.R. Heinle. A
Comparison by Size, Class and Volume of Detritus versus
Phytoplankton in Chesapeake Bay. Estuarine and Coastal
Marine Science 6:569-582, 1978.
28. Zabawa, C.F. Microstructure of Agglomerated Suspended
Sediments in Northern Chesapeake Bay Estuary. Science,
vol. 202:49-51, 1978.
29. Hires, R.I., E.D. Stroup, and R.C. Seitz. Atlas of the
Distribution of Dissolved Oxygen and pH in Chesapeake
Bay 1949-1961. Graphical Summary Report 3, Ref. 63-4,
Chesapeake Bay Institute of the Johns Hopkins University,
1963. 12 pp.
- 106 -
-------
30. Setlock, G.H., W.S. Moore, S.A. Sinex, and G.R. Helz. Pb-
210 Geochronology of Chesapeake Bay Sediments (in prep.).
31. Carron, M.J. The Virginia Chesapeake Bay: Recent Sedimenta-
tion and Paleodrainage. Ph.D. Dissertation, Virginia
Institute of Marine Science of the College of William an
Mary, Williamsburg, Virginia, 1979.
32. Taylor, W.R., A.D. Eaton, and W.B. Cronin. EPA Chesapeake
Bay Program Trimester Report. Chesapeake Bay Institute,
Shady Side, Maryland, 1979, pp. 7.2-8.1.
33. The Westinghouse Electric Corp. Oceanic Division. Vol. II.
Annapolis, Maryland, 1975. 256 pp.
34. Duinker, J.C., and R.F. Nolting. Distribution Model for
Particulate Trace Metals in the Rhine Estuary, Southern
Bight and Dutch Wadden Sea. Netherlands Journal of Sea
Research, 10 (I):71-102, 1976.
35. Schubel, J.R. Effects of Tropical Storm Agnes on the
Suspended Solids of the Northern Chesapeake Bay. In:
Suspended Solids in Water, R.J. Gibbs, ed. Plenum, 1974,
pp."113-132.
36. Dyer, K.R. Sedimentation in Estuaries. In: The Estuarine
Environment, R.S.K. Barnes, ed. Applied Science Publishers,
Ltd., 1972, pp. 10-45.
37. Schubel, J.R., R.E. Wilson, and A. Okubo. Vertical Trans-
port of Suspended Sediment in Upper Chesapeake Bay. In:
Estuarine Transport Processes, B. Kjerfve, ed. University
of South Carolina Press, 1978, 331 pp.
38. Kranck, K. Particulate Matter Grain Size Characteristics
and Flocculation in a Partially Mixed Estuary. Sedimentology,
Vol. 28:107-114, 1981.
39. Turekian, K.K., and K.H. Wedepohl. Distribution of the
Elements in Some Major Units of the Earth's Crust. Bull.
Geol. Soc. Am. 72, 1961, pp. 175-192.
40. Bostrom, K., 0. Jensuu, and I. Brohm. Plankton: Its
Chemical Composition and Its Significance as a Source of
Pelagic Sediments. Chem. Geol. 14:255-271, 1974.
41. Forstner, U. Inorganic Pollutants, Particularly Heavy
Metals in Estuaries. In: Chemistry and Biogeochemistry
of Estuaries, E. Olausson and I. Cato, eds. John Wiley
and Sons, Ltd., New York, 1980, pp. 307-348.
- 107 -
-------
42. Trefry, J.H., and B.J. Presley. Heavy Metals in Sediments
From San Antonio Bay and the Northwest Gulf of Mexico.
Environ, Geol. 1:283-294, 1976.
43. Nichols, M. Tracing Kepone Contamination in James Estuary
Sediments, International Council for Exploration of the Sea,
Workshop Proceedings, No. 8, 1981, 8 pp.
44. Sinex, A.S. Trace Element Geochemistry of Modern Sediments
from Chesapeake Bay. University of Maryland, Ph.D. Thesis,
1981, 190 pp.
45. Hakanson, L. An Ecological Risk Index for Aquatic Pollution
Control. A Sedimentological Approach, Water Research 14:
975-1001, 1980.
46. O'Connor, J.S., and H.M. Stanford. Chemical Pollutants of the
New York Bight. NOAA-MESA Rept., 217 pp., 1979.
- 108 -
-------
APPENDIX 1
DATA FOR BLANK CHEMICAL ANALYSIS
AS
yg/i
HN03 (n=5) <0.2
HC1 (n=5) <0.7
Distilled, <0.5
deionized
water (n=5)
Run Blanks <. 53
(50 ml vol. ,
n=20)
Cd Cu Fe
yg/1 yg/1 mg/1
<0.2 <1.5 <.014
<0. 1 <1. 0 <. 009
<0.1 <0.8 <.005
<.29 <1.8 <.56
Shipboard <.044 <. 032 <. 090 <.0021
filter
collection
blanks
(1 liter
vol. , n=13)
Hg Mn Ni Pb
yg/1 mg/1 yg/1 yg/1
<0.7 <.001 <1.6 <0.7
<0.5 <.001 <1.0 <0.7
<0.5 <.0006 <0.8 <0.8
<.37 <.025 <.83 <2.8
<.022 <.001 <.040 <.14
Sn Zn
yg/1 mg/1
<1.3 <.001
<1.0 <.001
<0.3 <.001
<.83 <.0087
<.028 <.0038
Metal
As (iAg/1)
Cd (Ag/1)
Cu (mg/1)
Fe (mg/1)
Hg (Wg/l)
Mn (mg/1)
Ni (mg/1)
Pb (mg/1)
Sn (wg/1)
Zn (mg/1)
Run Blanks
(50 ml. vol. , n=61)
<.73
<.24
<.0017
<.40
<.40
<.023
<.002
<.005
<1.0
<.009
Shipboard filter collection
blanks (1 liter vol., n=17)
<.040
<.031
<.0001
<.020
<.022
<.001
<.0001
<.0002
<.050
<.003
- 109 -
-------
APPENDIX 2
RECOVERY OF METALS ADDED TO HNO3 - DURING DIGESTION
(yg/1 concentrations)
Sample
A
B
C
(a)
(b)
(a)
(b)
(a)
(b)
As
7.9
8.3
8.0
11
12
12
17
18
20
Cd
1.
1.
1.
2.
2.
2.
3.
3.
3.
4
5
4
2
0
1
2
2
5
Cu
2.2
2.4
2.2
3.3
3.2
3.4
5.5
5.3
5.6
Fe
18
19
18
25
29
27
42
47
45
Hg
2.2
2.0
2.0
3.0
3.5
3.0
5.0
5.2
5.0
Mn
7.0
7.6
7.5
11
10
11
17
18
19
Ni
7.8
8.2
8.3
12
12
12
20
21
21
Pb
7.7
7.9
8.0
12
11
12
19
19
20
Sn
8.0
8.1
8.0
12
13
12
21
22
20
Zn
6.5
6.6
6.8
9.4
9.8
10
17
17
17
(a) values obtained (b) known additions
- 110 -
-------
APPENDIX 3
USGS STANDARD PCC-1 (n=3)
Metal
CA
Cu
Fe (%)
Mn
Pb
Zn
Metal
Cd
Cu
Fe (%)
Mn
Pb
Zn
Concentration (Mg/g)
x s .d.
<(0.1
12 2
6.2 0.1
980 30
13 1
32 1
USGS STANDARD AGV-1
Concentration (ug/g)
x s . d.
< 0.1
54 3
4.4 0.3
710 10
32 4
74 3
Standard Values
(.10)
11
5.8
960
13
36
(n=3)
Standard Values
(.09)
60
4.7
730
35
84
x = mean
s.d. = standard deviation
- Ill -
-------
APPENDIX 3
USGS STANDARD G-2 (n=4)
Metal
As
Cd
Cu
Fe (%)
Hg
Mn
Ni
Pb
Zn
Concentration
X
< 0.2
< 0.1
10.0
1.8
< 0.2
210
5.5
31
85
Olg/g)
s.d.
-
-
0.8
0.1
-
20
0,4
2
4
USGS STANDARD GSP-1
Metal
As
Cd
Cu
Fe (7.)
Hg
Mn
Ni
Pb
Zn
Concentration
X
< 0.2
< 0.08
30
2.5
< 0.2
221
12.6
50
98
(W8/8)
s.d.
-
-
2
0.3
-
26
1.9
4
10
Standard Values*
(0.2)
.04
11
1.8
«0.1)
212
5.1
31
85
(n=5)
Standard Values*
( 0.1)
.06
33
2.6
«0.1)
264
12.5
51
98
*References (5) thru (7)
- 112 -
-------
APPENDIX 3
USGS STANDARD MAG-1 (n=4)
Metal
Cd
Cu
Fe (%)
Hg
Mn
Ni
Pb
Zn
Concentration (wg/g)
X
.16
25.4
4.3
< 0.4
695
52
22
117
s.d.
.03
0.8
0.4
-
35
4
1
5
Standard Values*
.14
26
4.4
-
-
51
23
120
*References (5) thru(7)
USGS STANDARD MAG-1 (n=10)
Metal
Cd
Cu
Fe (%)
Mn
Pb
Zn
Concentration (ug/g)
X
.16
24
4.1
660
22
120
s.d.
.02
2
0.3
40
1.5
10
Standard Values
.14
26
4.4
-
23
120
x = mean s.d. = standard deviation
- 113 -
-------
APPENDIX 3
BOVINE LIVER (n=4)
NBS SRM 1577
Metal
As
Cd
Cu
Fe
Hg
Mn
Ni
Pb
Sn
Zn
Metal
As
Cd
Cu
Fe
Hg
Mn
Pb
Zn
Concentration (»g/g)
x s.d.
. 054 . 005
.28 .02
186 9
265 15
<.033
10.2 .6
2.8 .4
.37 .05
.093 .007
128 6
BOVINE LIVER
NBS SRM
(n*10)
1577
Concentration (,wg/g)
X
<.07
.27
190
266
<.07
10.5
.33
128
s.d.
.02
7
10
.6
.05
5
NBS
(.055)
.27
193
270
.016
10.3
.34
130
NBS
(.055)
.27
193
270
.016
10.3
.34
130
Values
s.d.
.04
10
20
.002
1.0
.08
10
Values
s.d.
.04
10
20
.002
1.0
.08
10
x = mean
s.d. = standard deviation
- 114 -
-------
APPENDIX 3
USGS STANDARD G-2 (n=10)
Metal
Cd
Cu
Fe (%)
Mn
Pb
Zn
Metal
Cd
Cu
Fe (%)
Mn
Pb
Zn
Concentration (ng/g)
x s .d.
< 0.1
9.3 1.0
1.7 0.1
195 20
30 2
87 5
USGS STANDARD GSP-1
Concentration (^g/g)
x s.d
<0.08
29 2
2.4 0.3
210 26
50 3
95 8
Standard Values
.04
11
1.8
212
31
85
(n-8)
Standard Values
.06
33
2.6
264
51
98
x = mean
s.d. = standard deviation
- 115 -
-------
APPENDIX 4
EPA WATER POLLUTION STUDY WP005
Metal
As
Gd
Cu
Fe
Hg
Mn
Ni
Pb
Zn
Sample No.
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
Reported
(MR/1)
313
25
67
3.2
384
12
938
25
4.9
.43
521
15
323
36
404
26
438
16
True Value
(MR/D
300
22
70
2.5
350
11
900
20
8
,75
500
15
300
30
400
24
400
16
Warning
(w
163
11.3
52.0
0
262
2.50
751
0
1.49
.146
438
1.77
226
7.44
298
7.97
336
.665
Limits
8/1)
- 437
31.7
- 81.0
- 6.78
- 428
- 23.5
- 1054
- 58.1
12.7
1.55
- 554
- 29.7
- 377
- 56.3
- 491
- 46.0
- 468
- 36.6
- 116 -
-------
APPENDIX 5
SUSPENDED SEDIMENT REPLICATE .ANALYSES FOR CRUISE 1
(metal/1 Bay water filtered)
Station/
Depth (m)
17/6
X
s.d.
19/0
X
s.d.
19/5.1
X
s.d.
15/9.5
X
s.d.
As
Wg/l
.39
.50
.60
.60
.52
.10
.18
.30
.20
.20
.22
.05
.26
.30
.20
.25
.05
1.4
2.0
2.1
1.8
0.4
Cd
Wg/l
-------
APPENDIX 5
SUSPENDED SEDIMENT REPLICATE ANALYSES FOR CRUISE 2
(metal/1 Bay water filtered, n=3)
Station/
Depth (m)
4/7.3
x
s.d.
6/11
s.d.
14/10
x
s.d
As
«.g/l
.31
.05
5.0
0.7
1.1
0.1
Cd
HB/1
.071
.010
.24
.06
.043
.008
Cu
Mg/1
1.5
0.2
8.5
1.3
4.3
0.5
Fe
mg/1
.93
.16
14
1
3.8 <
0.5
x =
s.d.-
Mg/1
.23
.02
.56
.12
.060
mean
Mn
HK/1
23
4
160
4
270
20
• Ni
ug/1
2.2
1.1
13
2
5.7
0.6
Pb
ug/1
1.3
0.1
3.0
0.4
6.1
0.6
Sn
Ug/1
<.29
<.88
.33
.11
Zn
15
1
67
11
35
6
standard deviation
Cruise 4
Suspended
Station/
Depth (m)
3/0
x
s.d.
5/8
x
s.d.
11/0
x
s.d.
24/16
x
s.d.
As
Mg/1
-------
APPENDIX 5
SUSPENDED SEDIMENT REPLICATE ANALYSES FOR CRUISES 5 AND 6
APRIL-MAY, 1980 (metal/1 Bay water filtered)
Station/
Depth (m)
19/6
.2
Time
1200
x(n=4)
• s
17/9
X
s
15/6
x
s
11/0
X
s
.d.
.8
(n=3)
.d.
.4
(n=3)
.d.
(n=3)
.d.
1000
1000
1600
Cd Cu Fe
Ug/1 us/1 mg/1
.071
.016
<.032
-
<.021
'
.050
.010
1.8
0.2
3.7
0.2
.98
.04
1.0
.05
1.5
0.1
2.8
0.1
.82
.02
.19
-
Mn
Hg/1
110
5
200
15
58
1
21
1
Pb
Hg/1
4.3
0.3
3.8
0.1
2.0
0.1
2.6
0.4
Zn
MR/1
11
1
18
1
7.4
1.0
9.1
1.7
13/13.1
x
s
SURFACE
(n=4)
.d.
FLUID MUD
.33
.07
APPENDIX
4.4
0.7
5
REPLICATES FOR
(dry weight
Station
(Cruise)
19 (3)
x
s.d.
20_(3)
x
s.d.
x
s.d
6 (4)
x
s.d
17 (4)
x
s.d
As
JAg/g
1.4
0.1
2.2
0.1
.89
.09
2.3
0.2
1.1
0.1
Cd
Ug/g
.42
.05
.29
.03
<.064
-
.057
.005
.51
.01
Cu Fe
ug/g °L
36 2.9
3 0.1
35 3.3
5 0.1
.45 .78
.04 .04
5.9 1.5
0.7 0.1
35 2.8
2 0.1
, n=3)
Hg
Hg/g
<.094
-
<.095
~
<.096
-
<.078
-
<.089
~
1.7
0.2
180
20
CRUISES 3
Mn
mg/g
1.9
0.1
1.9
0.1
.17
.01
.18
.01
1.4
0.1
Ni
Hg/g
44
3
21
3
3.0
0.2
11
1
43
2
4.9
0.5
AND 4
Pb
Hg/g
40
4
79
7
3.1
0.3
7.9
0.7
34
2
14
2
. .
Sn Zn
Hg/g mg/g
<.22 .23
.02
<.22 .32
.01
<.22 .020
.001
<.20 .043
.003
.45 .17
.04 .01
x = mean
s.d. = standard deviation
- 119 -
-------
APPENDIX 6
LONGITUDINAL-DEPTH DISTRIBUTIONS OF MEAN METAL CONCENTRATION IN
PER WEIGHT' FOR AL^ AVAILABLE OBSER-
221918 16 I4I3(|2 II 10
i i i i i i I i ii •
::;i;i MEAN ARSENIC ug/g '&
49.0
v:MEAN CADMIUM jug/g
0
10
20
30
40
.'^'
-------
APPENDIX 6, continued
RIVER
221918 16 1413112 II 10
JMEAN IRON % (by weight);
xixH:;:: MEAN LEADjjg/g
MEAN MANGANESE mg/g:-
320 280
240 200 160 120
— DISTANCE LANDWARD, km.
40
- 121 -
-------
APPENDIX 6, continued
X
RIVER
v<*
MEAN MERCURY ^ig/g *A
221918 16 I4l3(l2 II 10
OiJtfi Mill I ''—L~~L
. I >2 I
^o / .1 • • • "\ „• •
10'
iii ' ii '—i . i
/ • • • • • r • • •v?
MEAN NICKEL ug/g :::::i
:xi:::i:i:::::::: MEAN TIN jug/g :
320 280
240 200 160 120 80 40
——• DISTANCE LANDWARD, km.
- 122 -
-------
APPENDIX 6, continued
RIVER
221918 16 I4l3(l2ll 10 9 8 7(65 2X|
-o—i—i i i i—i i li—i—• * • 'III 1—i
_°OCEAN
- 123 -
-------
X
H
Q
25
W
CM
PM
- 124 -
-------
«
•3-
0»
E
Cvl
O
CD
0.8
^
o»
3
O
s
Q
CO
,
•
0
n
-
_
"R
1
1
1
1
^*vl a
•^N/V
E
|
1
"I
c
;
- it
1
,1
:
I
•it
:
s.
S IT
V ^
N ^
S ^
S V f
s v ""•
S ^ -
\ * »
s s S v
N ^^ s
s ^ x-
////A'/////,
-0 ? r. V) 0
.— C C 01
3 o.o « S.
U. W^ go
— •o c"" o> S «5°
— 3 o*^ c >a>
U-5 Z5 OQ Qx -NN SX . <
S X> OvS OvN VO 6
j ^ ^ ^ i m
w
3
i MANGANES
* MEAN
Qz
u|
1 m r^l
Ti
0)
O
u
X
H
Q
2
W
PM
CM
- 125 -
-------
q
OJ
JO.
So
3> o
c to
OQ
«
o1
< U.
a
o
o
0)
-P
C
O
O
X
H
P
a
s
o
(O
0>
o
*
UJ z
X <
O UJ
n
n
- 126 -
-------
TJ ».
n O
-s_ s-
'.Si <>> »-
7 CO o
Ct3 »'>
O => CO)
- 00
> a)
T)
(U
3
C
-H
-P
c
0
o
X
H
Q
— LJ
- 127 -
-------
APPENDIX 8
DISTRIBUTION OF METAL CONTENT, WEIGHT PER VOLUME, IN SURFACE AND
NEAR-BOTTOM SUSPENDED MATERIAL WITH DISTANCE ALONG THE BAY AXIS.
MEDIAN VALUES AND RANGE OF CONCENTRATIONS FROM ALL AVAILABLE
OBSERVATIONS OF THIS PROJECT.
METALS IN SUSPENDED MATERIAL
SURFACE
321918 16 1413 12 II 10
STATION
9 8
21
CADMIUM
•RANGE
ARSENIC
+~±
COPPER
IRON
LEAD
280 240 200
160 120 80
DISTANCE, km
221918 16 14 1312 II 10
STATION
9 8
2 I
100
80
i, so
I
40
20
0
18
16
14
12
; I0
1 08
06
04
02
0
7
6
5
i *
J
3
2
I
0
4
3
>
' 2
25
20
15
10'
5
\l"\
MANGANESE
MERCURY
24 I 26
NICKEL
TIN
ZINC
280 240 200
160 120 80
DISTANCE,km
- 128 -
-------
APPENDIX 8, continued
METALS IN SUSPENDED MATERIAL
NEAR-BOTTOM
STATION
9 B
160 120 80
-DISTANCE, km
280 240 200 160 120 80 40 0
« DISTANCE
- 129 -
------- |