United States
Environmental Protection
Agency
Chesapeake Bay
Program
Annapolis MD 21403
Research and Development
EPA-600/S3-83-012 June 1983
&EPA Project Summary
Chesapeake Bay Sediment
Trace Elements
G. R. Helz, S. A. Sinex, G. H. Setlock, and A. Y. Cantillo
This report contains the results of
analyses of bottom surface sediment
samples and sediment vertical core
samples from Chesapeake Bay.
Baltimore Harbor, and the Elizabeth
River. For the surface samples in the
Bay, both the fine fraction and the
unf ractionated sediment were analyzed
for chromium (Cr), manganese (Mn),
iron (Fe), cobalt (Co), nickel (Ni), copper
(Cu), zinc (Zn), cadmium (Cd), and lead
(Pb), by atomic adsorption spectrom-
etry. For the Bay cores, water content,
210Pb, carbon (C). nitrogen (N),
aluminum (Al), silicon (Si), titanium (Ti),
vanadium (V), chromium (Cr),
manganese (Mn), iron (Fe), cobalt (Co),
nickel (Ni), copper (Cu), zinc (Zn), and
zirconium (Zr) were determined at
various depths. Alpha spectrometry
was used for 210Pb, and DC plasma
emission spectrometry was used for all
elements except C and N, which were
determined by a CHN analyzer. More
than 8,000 individual analyses are
reported in Chesapeake Bay, making
this the first comprehensive survey of
trace element chemistry in the Bay.
Baltimore Harbor and the Elizabeth
River were sampled to represent areas
of high contamination. Samples of the
bottom surface sediments and vertical
sediment samples were also taken to
provide comparison of these
contaminated areas with those of the
Bay.
This Project Summary was developed
by EPA's Chesapeake Bay Program.
Annapolis, Maryland to announce key
findings of the research project that is
fully documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
A number of previous investigations of
toxic substances have been made in
various parts of Chesapeake Bay. In all
cases, however, the analytical work was
conducted as part of isolated projects,
and the methods used were generally not
comparable from one project to another.
Thus, it has not been possible to make a
regional synthesis that would allow
different parts of the Bay to be compared
and changes with time in the condition of
the Bay to be convincingly documented.
The Environmental Protection Agency's
Chesapeake Bay Program provided the
first opportunity to examine the question
of contamination in the Bay on a regional
scale. Samples were collected
throughout the Bay and were analyzed for
a particular class of toxic substances by a
single laboratory using consistent, clearly
described procedures.
This report is about trace elements in
the sediments of Chesapeake Bay. In high
concentrations, certain of the trace
elements studied a re known to be toxic to
a large variety of organisms. In low
concentrations, however, they may be
essential micro-nutrients. Knowledge of
the distribution of trace metals is
important not only because of their
potential impact on the ecosystem but
also because they might serve as tracers
for other anthropogenic substances
which are themselves much more
difficult to detect in the environment.
This study consisted of three
components The concentration of nine
elements was determined in 246 surface
sediment samples in order to establish
the current geographic distribution of
these elements. Vertical profiles were
determined in 45 cores to investigate the
-------
possibility of historical changes. Finally,
the 210Pb and 226Ra activity in certain
cores was measured in order to
determine deposition rates and provide a
scale for any historical changes observed.
Procedure/Methodology
Both surface grab samples and vertical
core samples were collected. All surface
samples were collected between April,
1977 and June, 1981. The sampling
stations were located along 25 transects
running roughly in an east-west direction
and extending from the mouth of Chesa-
peake Bay to the Susquehanna River as
well as along two special transects into
Baltimore Harbor and the Elizabeth River.
A Ponar grab was used for sampling, and
variable-range radar triangulation was
used for navigating. An unfractionated
suo-sample and a <63 urn sub-sample
were measured in most cases. Whereas
the unfractionated sediment samples
were found to be reasonably reproducible
in muddy terrain, the data obtained from
sandy environments are limited by the
chemical heterogeneities inherent in
sands.
Most of the core samples were obtained
during the November, 1978, May to
June, 1979, and May to June, 1981
cruises. Sampling reducibility studies
were not attempted with the core
samples.
Surface sediments from the main stem
of Chesapeake Bay were extracted with
nitric and hydrochloric acids. Sample
extracts were analyzed by atomic
absorption spectroscopy under
conditions recommended by the manu-
facturers. In order to determine a larger
group of elements in the core samples
and in the surface samples from Balti-
more Harbor and the Elizabeth River and
to have an independent method with
which to check the atomic absorption
data, another method was developed
which involved fusing the samples with
lithium metaborate, dissolving the
resulting glass in nitric acid, and using
direct current argon plasma emission
spectroscopy (DCP) to determine the
metal content of the solutions. Deposition
rates in the cores were determined by
210Pb assays using the alpha-spectro-
photometric measurement of daughter
polonium-210.
Results/Conclusions
The frequency distributions for all
elements in the unfractionated samples
were approximately log-normal. Some
elements displayed a bimodel
distribution. Factor analysis of Bay
samples showed that either one factor
was involved in the control of trace
elements in the sediments, or, more
likely, there were coalescent multiple
factors.
Analysis of the data indicates that the
elements in the <63 iim fraction
decrease seaward, probably reflecting
the distance from the Susquehanna
River, which delivers relatively metal-rich
sediment to the Bay. In some places, the
metals also decrease eastward across the
Bay, suggesting that either seaward
transport of Susquehanna-derived
sediments is more effective on the
western side due to the Coriolis effect or
that the western side is enriched due to
sediment derived from the Piedmont
tributaries. The results for the
unfractionated sediments are similar to
those for the <63//m fraction but contain
additional variation due to grain size.
Chromium concentrations tend to
decrease down the Bay with high
concentrations (up to 135 ppm) in both
the unfractionated and <63 yum fraction-
ated samples occurring in and around
Baltimore Harbor and the Elizabeth River.
Manganese concentrations range from
74 to 6900 ppm in the <63 /urn fraction
and also decrease seaward. Elevated
levels have been found just north of
Baltimore Harbor in the area of the Gun-
powder River, as well as in the Harbor
itself. Elevated levels are also found in the
Elizabeth River.
The distribution of iron shows the
typical decrease seaward, with elevated
levels occurring around Baltimore Harbor
and Annapolis. The Baltimore
enrichment is thought to be due more to
local accumulation of fine-grained, iron-
rich particles than to industrial activity,
because the Fe/AI ratio is not particularly
anomolous in this region. However, large
discharges of iron-rich waste have histor-
ically occurred in the Harbor. Slightly
elevated levels at the mouth of the
Rappahannock River also may be caused
by the high clay content in this area.
Cobalt and nickel closely resemble
manganese in distribution. In addition to
the causes of enrichment already
mentioned, the discharge of Back River,
which contains both industrial and
municipal wastewater from Baltimore,
may contribute to the enrichment.
Copper, lead and zinc also display the
typical southward decrease, with each
showing a strong source from Baltimore
Harbor. Copper and zinc levels are ele-
vated just north of the Harbor, and all
three are enriched at the mouth of th
Rappahannock. These elements at
generally enriched in the upper rathi
than the lower parts of cores, suggestir
regional contamination that is presume
to be increasing with time.
Sedimentation rates were als
calculated and rangefrom0.7to42.6 m
per year. The highest rates wei
calculated for Susquehanna River cor«
and several cores collected near tr
mouth of the Potomac River. Most of tr
core samples from the upper and lowi
portions of the Bay were in the range i
several millimeters per yee
accumulation rate.
The levels of metals in the sediments i
Baltimore Harbor and the Elizabeth Riv<
area are high compared to those in th
surrounding Bay sediments. Howeve
both areas are composed of fine-graine
sediment and part of the elevated lev<
may be due to this fine fraction. Tr
Elizabeth River area shows consistei
anthropogenic enrichment only for Zi
whereas Baltimore Harbor is enriched i
Co, Cr, and Zn with minimal Venrichmen
Baltimore Harbor is working as a
effective trap for fine-grained sedimen
Most of the deposition is occurring in th
inner reaches of the Harbor. The zone i
contamination is over three meters in th
area. The zone wedges out in a seawai
direction and seems to show only mini
signs of appearing in the Bay proper.
-------
G. R. Helz, S. A. Sine*. G. H. Setlock, and A. Y. Cantillo are with the University of
Maryland, College Park, MD 20742.
Duane Wilding is the EPA Project Officer (see below).
The complete report, entitled "Chesapeake Bay Sediment Trace Elements,"
(Order No. PB 83-207 621; Cost: $19.00, subject to change) will be available
only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Chesapeake Bay Program
U.S. Environmental Protection Agency
2083 West Street, Suite 5G
Annapolis, MD 21403
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
S
AGENCY
CHICAGO IL 60604
------- |