EPA 903-R-01-003
CBP/TRS 251/01
January 2001
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fail tine Loadings of Metals
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Into Chesapeake Bay
Chesapeake Bay Program
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Printed for the Chesapeake Bay Program by ihe Environmental Protection Agency
Recycled/Recyclable - Primed with Vegetable Oil Based Inks on Recycled Paper )0% Pastconsumer
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Fall Line Loadings of Metals from the Potomac River Basin
into Chesapeake Bay
2001
Chesapeake Bay Program
A Watershed Partnership
Chesapeake Bay Program
410 Severn Avenue, Suite 109
Annapolis, Maryland 21403
1-800-YOUR-BAY
http://www.chesapeakebay.net
Printed by the L'.S. Environmental Protection Agency for the Chesapeake Bay Program
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EPA CHESAPEAKE BAY PROGRAM
TOXICS SUBCOMMITTEE FINAL REPORT
TlTLE-.Fall Line Loadings of Metals from the Potomac River Basin into Chesapeake Bay
AUTHORS:Thomas M. Church, Marine Studies, University of Delaware (302/831-2558)
Kathryn M. Conko, Marine Studies, University of Delaware (703/648-5799)
(Current address USGS; WRD, Reston VA)
Joseph R. Scudlark, Marine Studies, University of Delaware (302/645-4300)
DATES OF STUDY: 1996-2000
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ABSTRACT
The Potomac River and Estuary form the second largest tidal tributary of the Chesapeake
Bay, which includes at its mid-portion the large urban and suburban Washington DC area. The
Potomac River basin was sampled for trace metals near its fall line at Chain Bridge, Washington
DC, from October 1996 through August 1997, to determine its contribution to the metal loading
of Chesapeake Bay. To characterize the river loadings during various flow regimes, the river
was sampled (1) routinely, at base-flow, on monthly to bi-monthly intervals, and (2) intensively
during a spring-storm, high flow event. The upper Potomac watershed was sampled twice at
nine stations within the headwaters of the basin. In Washington DC, Rock Creek tributary was
sampled on a monthly or bi-monthly interval during base-flow conditions. For comparison, the
Potomac Estuary was sampled once each during the winter and summer of 1997.
The field sampling, preparation and analysis of the trace metals used ultra-clean sampling
methods. The samples were analyzed for both dissolved (<0.45 u) and paniculate fractions for
Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se (dissolved only), and Zn. The data are computed and
compiled for (1) dissolved/particulate concentration distribution, (2) loadings using USGS
discharge data, and (3) basin yields on an area specific basis for each watershed. The
concentrations are compared to similar results from other Potomac and Chesapeake Bay tributary
studies.
The concentrations and corresponding loads of trace metals at the fall line of the
Potomac River are dominated under average flow conditions by the particulate fraction, unlike
most of its upper tributaries, including Rock Creek. The metals which exhibited a significant (if
minor) dissolved component at base flow include As, Cd, Cu, Hg, Ni and Zn. However, on an
annual basis and dominated by storm flow, only As, Cd and Cu show any significant dissolved
fraction. This particulate dominance at the fall line is unlike other tributaries within either the
Potomac or Chesapeake basins, including the Potomac estuarine portion and the dominant
Susquehanna River. The dissolved concentrations are fairly consistent for the basin, with a
minimum at the Cotoctin and Monacacy tributaries. This reflects the atmospheric and
weathering inputs in the upper reaches, and equal input from urban runoff in the lower portions.
As expected, these concentrations are lower than the urban Anacostia tributary, but consistent
with the Susquehanna studied previously. Rock Creek has lower concentrations in spite of being
located within the urban watershed. This could reflect its protected status as a national park with
limited urban runoff. However, the dominant particulate burden at the Potomac fall- line shows
considerable spatial and temporal variation. While there is significant variability for some metals
such as Mn and Zn which is thought to be related to seasonal changes of vegetation within the
watershed, there is considerable increases in the metalloids As and Hg during the summer that
appear related to seasonal pollution activities within the basin. As a function of high discharge
flow, the concentrations of many metals show a peak early in the discharge, followed by
dissolved peaks either later in the hydrograph, or even at other seasonal times unrelated to
discharge.
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The trace metal concentrations in the Potomac sub-estuary are, unlike the Chain Bridge
fall line, characterized by a larger dissolved fraction, going through a minimum in winter and
generally increasing downstream during the summer. This appears to reflect the seasonal
changes in discharge, phytoplankton blooms, and riparian zones within the estuary. While the
concentrations are similar to that at the fall line, it is apparent that the estuarine portion is
processing the dominant paniculate load of the river into more dissolved components. For non-
crustal elements this could mean either eutrophic or toxic effects for metals within the Potomac
sub-estuary and larger dissolved contribution to the greater Chesapeake Bay.
I. INTRODUCTION
The Chesapeake Bay is an expansive estuarine system with a series of sub-estuaries
draining a large variety of lithologies and urban/industrial activities, including its largest sub-
estuary, the Potomac. Here, the land use varies from forested mountains, through an agricultural
plain, to the extended Washington DC urban corridor, and in the large sub-estuary of
Chesapeake Bay. Throughout the Potomac watershed, there are vastly different lithologies
ranging from low grade metamorphic green stones to well-weathered quartzite.
The central hypothesis of this study is that metal contaminant concentrations and
resulting loads are a function of both direct atmospheric deposition into and indirect throughput
from the tributary watershed. This includes (1) weathering within distinct geological provinces,
(2) various rural, suburban and urban runoff sources within the tributary basin, and (3) final
estuarine processing within the Potomac estuary before input to the main stem of the Chesapeake
Bay. Such a study allows a better understanding of how different subunits in a drainage basin
contribute or process these metal contaminant sources. The study also permits some resolution
of the contaminant metal sources fluxing across the fall line into the receiving coastal water, and
thus better management of contaminant abatement within the basin.
Annual estimates of contaminant loadings above the fall lines of the Susquehanna,
Potomac, and James rivers, the Bay's three largest tributaries, have been reported for various
years between 1990 and 1994 by the Chesapeake Bay Fall Line (Toxics Monitoring) Program
(CBFLP).
The CBFLP program is designed to:
1) Identify types and quantities of priority contaminants in fluvial transport
2) Characterize such contaminant concentration with respect to water discharge
3) Estimate annual contaminant loads of the major tributary sources to the Bay
Estimates of river fall line metal loads have proven to be useful in determining the overall
contribution of fluvial versus the atmospheric input fluxes of contaminants to Bay tidal waters.
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However, questions related to variables such as land use, basin lithology, hydrology, and modes
of transport from the watershed cannot be answered with the limited degree of temporal and
spatial coverage provided through the conventional CBFLP approach. The sources and behavior
of toxic metal substances in fluvial transport from stream headwaters to Chesapeake Bay have
not been previously characterized via the CBFLP. Better resolution of contaminant metal
sources and loading throughout the provinces of an entire basin would allow for a much better
understanding of not just the fluxes, but also processes responsible for net metal inputs to the
Bay. To this end, this project focused on metal sources, processing, and fate in the greater
Potomac River Basin, including some estuarine portions.
II. THE STUDY
A. Background
With the growing realization that the ecosystems of the Chesapeake Bay are potentially
affected by toxic chemical contaminants, the U.S. Environmental Protection Agency -
Chesapeake Bay Program (USEPA-CBP) has committed itself to defining the magnitude, timing,
and severity of contaminant loadings to the Bay. The USEPA-CBP has formulated a list of
primary and secondary "Toxics of Concern" which include trace elements (metals) that present a
potential risk to the main estuarine portion of the Bay. Inputs of these contaminants come from
point and non-point sources (e.g., atmospheric deposition, industrial emissions and effluents as
well as urban runoff). Measurements made at the fall lines of major Chesapeake Bay tributaries
have provided a combined estimate of loads from all these sources from the non-tidal portion of
the watershed.
Thus, this study was developed to enhance the understanding of the nature and transport
of potentially toxic metal contaminants through the Potomac River Basin to the Chesapeake Bay.
The study produced a database of metal inputs from the second largest tributary of the Bay
during periods of varying flow and season to produce load estimates for selected metal
contaminants. It also studied on occasion the sources of metals within riverine basin, and
contribution to and behavior within the estuarine portions of the Potomac.
To better define geologic and geochemical processes and other variables important in
fluvial trace metal transport through the Potomac River Basin, it is necessary to have greater
spatial coverage within specific basins than that employed in the 1994 CBFLP. Geochemical
factors include:
(1) the composition and concentrations of dissolved and suspended trace metal
particulate material crossing the Potomac River fall line under both baseline and
high flow periods,
and
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(2) the nature and composition of Potomac River surface runoff, particularly in urban
areas, and upper reaches represented during base flow.
Contaminant trace metal concentrations and fluxes in the physiographic provinces of the
Potomac River basin were proposed to provide information regarding the importance of sources
in fluvial transport. Streams discharging into the Potomac River contain both agricultural and
urban runoff and constitute the primary source of agrichemicals. Thus, the flux at the fall line
represents the sum of the Blue Ridge and Piedmont provinces, along with a substantial urban and
sub-urban contaminant flux from the Washington metropolitan region into the Potomac River.
The Blue Ridge Province section of the River receives runoff arising from atmospheric
deposition processes on land surfaces. In the absence of unique point sources, the origin of metal
contaminants in mountain streams of this province arises primarily from the atmosphere (Church,
et al., 1998; Scudlark, et al., 1999). As such, there are trace metal atmospheric deposition data
from related EPA (e.g., CBADS, AEOLOS) and MDPPRP (conducted at Bear Branch and
Frostburg MD) studies in the Chesapeake Basin. However, there is limited information on the
concentration and fate of metals once discharged into the Potomac sub-estuary for processing
before eventual contribution to the main stem of Chesapeake Bay. These processes likely
include phytoplanktpn blooms and tidal exchange with subtidal and intertidal salt marshes.
B. Objectives
Our overall objective was to determine how the concentration, distribution, and loads of
trace metal contaminants change within the Potomac basin. The study was designed to help
determine how the mode of trace metal loading is also likely to undergo dynamic changes during
fluvial transport from watersheds into the river basin and ultimately across the fall line.
Our specific research objectives included the following:
(1) Better define the concentrations of trace metal contaminants by fluvial transport
crossing the Potomac River fall line but extending, on occasion, from the headwaters in
Appalachian Mountains in West Virginia through to the fall line near Washington D.C.
Upstream watershed sources were focused on two of the three physiographic regions of
the river basin, the Blue Ridge and Piedmont provinces.
(2) Characterize the relative loadings of trace metals to aid in determining the
hydrologic pathways and basin yields at the physiographic level. It has been shown that
groundwater sources in streams (i.e., base flow) have relatively higher concentrations of
some trace metals relative to surface runoff. Pinpointing the mechanisms by which these
metal contaminants comprise fluvial transport can serve as specific tracers of the
hydrologic cycle (e.g., atmospheric runoff versus ground water inputs).
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(3) Determine the mode of transport via dissolved and particulate partitioning to
better define the total concentrations of metals, fluvial loading, and modes of transport
through each of the physiographic regions of the basin.
C. Project/Task Description
The approach to the project is described as follows:
(1) determine the ambient concentration, nature, and transport of selected metals for
various flow conditions sampled routinely at the Potomac River fall line, and the urban Rock
Creek tributary. These data were used for comparison to water-quality standards and in
calculating load estimates,
(2) improve the metal load estimates to the Chesapeake Bay by including the annual
metal loads from the second largest Bay tributary the Potomac River. Load estimates were
improved by the use of ultra-clean sampling methods and more sensitive analytical techniques.
In addition, the quantitative analysis of the particulate phase provided a more comprehensive
load estimate, which should improve the mass balance of the Chesapeake Bay. In the past, trace
elements were determined as the "total-recoverable" fraction of the sample, which was
quantitatively defined and thus difficult to interpret, and
(3) additionally measure twice yearly, the same suite of metal contaminants from the
Potomac River fall line at several headwater gaging stations and three major tributaries of the
Potomac River, as well as the lower estuarine portions Instantaneous contaminant loads and
corresponding basin yields are calculated for each of the tributary sites. This should provide a
more synoptic evaluation of non-point metal loads from the upper portion of the Potomac
watershed. Results of this synoptic study also identified regions contributing disproportionally
to the pollutant metal loading that may require further management.
III. SAMPLING DESIGN
Base flow samples near the fall line were collected once per month in January, July,
August, September, October, November and December, and twice per month in February,
March, April, May, and June of 1997. Discrete storm flow samples were collected for one storm
event; during both the rising and falling hydrograph, and during peak flow. Synoptic samples
were collected near the fall line at the USGS gaging on Rock Creek starting in December, 1997.
Two surveys of the tidal portion of the Potomac sub-estuary were taken at five sites along the
salinity gradient in February and July of 1997.
Sampling Sites (Figure 1)
1) The Potomac Watershed was proposed for intensive study because (1) it
contains contrasting sub-basin geologies and biogeochemistries, (2) it is the second largest fresh
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water source to the Bay, (2) there are relatively high contaminant yields were identified in the
previous 1994 CBFLP, and (4) varied land uses. The Potomac River basin drains a watershed of
11,560 mi2 above Chain Bridge, Washington, D.C., has an average annual discharge of about
10,000 fVVs, and is divided in land use between forested (56%), agricultural (38%), and urban
(6%) areas. The Potomac Basin has an airshed characterized by both remote fossil fuel
emissions and local non-industrial (e.g., motor vehicle) emissions which funnel into a watershed
with mountain forests, rural agricultural, suburban and urban run-off.
2) Potomac River was sampled near its fall line in Washington, D.C.,
(01646580) Arlington County, Virginia, latitude 38 55'46", longitude 77 07'02", hydrologic unit
02070010. This site was chosen at the fall line because it is before potential tidal influence,
including downstream areas of the river which drain the D.C. metropolitan area with a
contributing urban watershed. The river contributes approximately 16% of the total freshwater
discharge into Chesapeake Bay. Discharge measurements are made one and one half miles
upstream at the Little Falls Dam USGS gauging station (01646500), latitude 38 56'58", and
longitude 77 07'40".
3) Head Water and Tributary Survey was conducted during two intensive
phases during May and August 1997, throughout the upper reach of the river basin during a
high base flow and low base flow period. The headwaters of the River were sampled
synoptically at nine USGS gauging stations both at the primary tributaries and throughout the
basin. The location of these nine stations above the fall line were chosen to be representative of
the geographic and geologic provinces along the River. The goal was to understand sub-basin
processes related to fluvial transport and ultimately water quality of the Bay.
The headwater and tributary survey was done twice during the sampling year. It included
seven sites along the reach of the Potomac River from Kitzmiller, Maryland to Chain Bridge, as
well as three tributaries of the Potomac Riber, Catoctin Creek, the Monacacy River and Rock
Creek. The locations of the headwater sites are listed in Table la.
4) Potomac Estuary Survey was conducted twice during the winter (February)
and summer (July) of 1997 at five locations along the salinity gradient from near its terminus at
Piney Point up to confluence with the Anacostia River. Sampling included upper and lower
waters in the stratified regions. The locations of the tidal Potomac sites are listed in Table Ib.
IV. METHODOLOGY
All samples were collected using ultra-clean techniques. The analytical methods and
detection limits for the trace metal constituents are summarized in Table 2. Samples were
analyzed for selected metals, both dissolved, and particulate phases, for all constituents
(dissolved Se only).
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A. Field Methods
The sampling schedule for the study is outlined in Table 3. Trace metal samples were
collected with a fixed volume Teflon® bailer. At the fall-line, samples were collected as a cross
section to ensure that they would be representative of current river conditions. This was done by
integrating three individual samples at the center of flow, or using a similarly appropriate grab
sample integration at the basin stations. The unfiltered samples were stored on ice and returned
to the laboratory for filtration the same day. Briefly, all sample handling and analysis was
performed using ultra-clean trace metal procedures that included: sampling with pre-cleaned,
non-contaminating sampling apparatus, manipulation with polyethylene gloved hands and
multiple bagged sample storage. The samples were filtered through a pre-cleaned 0.45um
Nuclepore membrane filter which was retained for paniculate analysis. A complete description
of these methods was included in the QA/QC plan (Section C).
The Potomac River at the fall line was sampled from Chain Bridge, which is
approximately 70 feet above the water surface. Samples were collected at three cross-sectional
intervals including increments of equal flow using a Teflon® bailer. A 100-foot length Teflon®-
coated cable wound on a cordwheel was used to lower and raise the bailer to and from the point
of sample collection. At each section, as the sample was collected it was poured directly into a
single holding container to integrate the sample (except for replicates) via a Teflon®-spout
inserted into the bailer just before the moment of sample transfer. This process involved a
minimum of two people, a designated "clean" person and a designated "dirty" person. The clean
person, with a change of surgical gloves at each sample collection point along the cross-section,
handled the bailer and nozzle only. The "dirty" person handled the hand reel, passed the bailer
nozzle through its storage bag to the clean person, and uncovered the appropriate bottles for
sample collection. Equipment blanks were performed quarterly prior to sample collection at the
mid-point of the sample-collection using ultra-pure inorganic-free-water.
Trace metal samples were collected in pre-cleaned, tared low-density polyethylene
(LDPE) bottles. Samples for Hg were collected in pre-cleaned Teflon®-bottles. The LDPE
bottles were cleaned using a multi-step procedure involving three-day soaks in three different
strengths of both HNO3 and HC1, with several rinses of de-ionized (DI) water both during the
transfers and at the end of the procedure. After cleaning, the bottles were allowed to dry under a
class 1000 clean bench and weighed.
The sampling bottles were pre-treated at the site by rinsing the bottles three times with
river water prior to sample collection. Sampling for the headwater survey followed similar
protocols for ultra-clean sampling with the following modifications: At several upstream
locations, the Potomac River is too shallow for the Teflon®-bailer to function properly. In these
situations the River was sampled by submerged filling of a pre-cleaned and tared, LDPE bottle
directly by gloved hand from the approximate center-of-flow of the River. Similarly, the
estuarine samples were collected directly from a Zodiac rubber boat by gloved hand into the tidal
flow.
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After collection, the samples were kept on ice during transit to the University of
Delaware. Upon return to the laboratory, they were immediately filtered through pre-cleaned,
tared 0.4 urn Nuclepore® filters using a peristaltic pump and a cleaned polycarbonate support
apparatus. The filters were dried in a 40 C oven, allowed to cool in a desiccator, weighed and
retained for particulate analysis. This and all future steps were done in a Class 1000 clean
environment.
The dissolved portion was collected in pre-cleaned LDPE bottles and acidified with
doubly-(quartz) distilled HC1 to 0.4% volume/volume, as per our normal operating procedures.
Once acidified, the samples were frozen in a laboratory freezer dedicated to trace metals storage.
B. Trace Metal Analytical Methods
Sample analysis for the dissolved portion was done by GFAAS (Graphite Furnace
Atomic Absorption Spectrophotometry) for Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn, CVAAS
(Cold Vapor Atomic Absorption Spectroscopy) for As and Se, or CFAAS (Cold Vapor Atomic
Fluorescence Spectroscopy) for Hg. For saline samples in the tidal Potomac, a chelation/solvent
extraction procedure (APDC/DDC into chloroform) was used to pre-concentrate the samples for
GFAAS. The particulate phase was analyzed following a digestion and total dissolution with hot
HCL:HNO3:HF in the proportions of 1:3:0.5 respectively (Church, et al., 1998). The digest was
analyzed by ICP-OES (Inductively Coupled Plasma - Optical Emissions Spectroscopy),
GFAAS for Cd and Pb, CVAAS for As and Se and CVAFS for Hg.
1) Dissolved Metals. The dissolved fraction of the samples was analyzed for Al,
Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn using a Perkin-Elmer 3300 Atomic Absorption
Spectrophotometer equipped with a 600 HGA graphite furnace (GFAAS). This instrument is
also equipped with a deuterium background correction and a L'vov platform was used to
maximize temperature uniformity during the furnace cycle. Citric acid was used as a matrix
modifier for Al and Fe to increase analytical sensitivity. The standard analyte injection was 60
ul for all elements except for Zn (10 jil). Multiple injections were used for Ni and Pb increasing
the volume of analyte to 120-180 jil, thus, augmenting the sensitivity 2-3 times. For As and Se,
the samples were converted to the hydrides with sodium borohydride, the hydrides purged and
concentrated cryogenically on a chromatographic substrate, and determined by sweeping them
into a quartz cuvette for AAS analysis. For Hg, the samples were reduced by stannous chloride,
the resulting elemental Hg was purged and concentrated on two successive columns of gold
coated sand, and then heating the columns to sweep the elemental Hg vapor into a quartz cell for
determination by atomic fluorescence spectrometry.
2) Particulate Metals. The particulate fraction was operationally defined as that
portion of the sample which was retained on the 0.4 um Nuclepore® filter. The particles were
digested using a technique to completely breakdown the filter and sediment. Briefly, the
technique involved a cold-soak overnight in concentrated HNO3. followed by successive heating
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with concentrated HC1 and HF. The samples were brought to volume with a saturated solution of
boric acid and then analyzed.
Because of the higher concentrations of elements in the particulate phase, ICPOES
analysis was employed for the same suite of elements as in the dissolved analysis. The samples
were aspirated directly into the instrument without additional treatment.
For As and Se, alliquots of the digests were analyzed as for the dissolved fraction. For
Hg, the samples were treated both filtered and unfiltered, with the difference attributed to
particulate Hg which is still highly reactive under the analytical protocol.
C. Quality Control and Assurance
The quality assurance practices of field procedures included complete documentation of
sampling quality assurance of field personnel. Two very important essential elements of our
Laboratory QC were (1) conducting and evaluation of blanks, and (2) use of externally certified
reference materials. These quality assurance and control procedures are detailed in the separate
QA/QC document previously submitted.
1) Sampling Blanks. Most contamination associated with trace element
analysis is associated with field collection. Thus, conducting and evaluating field blanks was
considered to be the most important component to our quality assurance program. Two major
types of blanks were evaluated: Field Blanks and Filter Blanks. The Field Blank is a collection
bottle that is filled with DI water at the collection site, which is subsequently filtered and
acidified along with the samples. Data from this blank is evaluated to determine the amount of
contamination associated with field collection and subsequent processing, including filtering.
2) Filter Blanks Acid (10% HC1) cleaned Nuclepore® filters were used
to filter the Field Blank consisting of an average sample volume of distilled water. The filter was
dried, weighed, and processed in an identical manner to the particulate samples. This blank
quantifies the amount of contamination from the filter and filtering process. In addition to these
blanks several unused filters were also digested and analyzed to quantify the contaminate
contribution from the filter itself.
3) Reference Materials. Externally certified reference materials were
regularly analyzed to verify the accuracy of the methods. These reference materials were
obtained from the National Research Council of Canada, and chosen because they are
representative of the sample matrices encountered in this study. They were a natural river water
(SLRS-3) and natural river sediment (BCSS-1) that have been certified for the metals analyzed
for in this study. The results of the replicate analysis of the EPA standard for water are included
as Table A-1 in the Appendix.
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D. Blanks and Replicates
The comparison of the average field blanks to average river concentrations of the
Potomac at the fall line are presented in Figure 2. For all metals, the blanks are less than ten
percent of the average sample concentration, except for Ni (25%).
Replicate analyses for (a) dissolved and (b) particulate trace metals in duplicate grab
samples are listed in Table 4. They include three Potomac stream side samples just below the
Chain Bridge and two other main stem sites (Paw-Paw and Cumberland) upstream during each of
the two headwater surveys. The dissolved replicates range 10-20%, which from laboratory and
field replicates reflects about half analytical uncertainty and half field variation. The particulate
variation is greater, and in a few cases (Fe, Pb and Zn), as much as a factor of two at the fall line,
but less upstream where the lower range of concentration is encountered.
V. RESULTS AND DISCUSSION
The Potomac primary data sets for dissolved and particulate concentrations of metals are
presented in the Appendix as Table A-2 and those for mercury in Table A-3. These primary-data
spread-sheets are available in electronic form from the EPA-CBP office.
A. Potomac Fall Line Concentrations and Loads
A summary of the total concentrations at the fall line for (a) Chain Bridge and (b) Rock
Creek are presented in Table 5. As there was insufficient sample for analysis of particulate Se,
only dissolved Se concentrations are presented. However, our previous fall line studies around
Chesapeake Bay suggest particulate Se contributions to be small. Normally, all samples were
taken as cross sectional integration, at which time a Center Of Flow (COF) sample was also
taken at Chain Bridge. However, on the first sampling (23 October 1996), three grab samples
from stream side just below the bridge (a, b, c), and the normal integration of the COF sample at
three points on the bridge (X-sec) were also taken. These results suggest considerable spatial
variability in the Potomac at this wide portion of the fall line. Alternatively, there may be some
course particle fall-out during compositing containing much of the Al and some other trace
elements. However this would be partly compensated if occurring in all samples taken from the
same integrated volume and treated identically.
The percentage distribution between dissolved and particulate concentrations for base
flow samples at the Potomac fall line is presented in Figure 3 a. It shows that the particulate
concentration is totally dominant for crustal elements (Fe, Mn, and Cr), still more than eighty
percent for the pollutant metals As, Cu, Ni and Zn, but only fifty percent for Cd, which agrees
with the phase concentration measured in an earlier study at the fall line of the Delaware River
(Church and Scudlark, 1998). However, for the annual period including all flows, the particulate
burden is totally dominant (Fig. 3b). It is not known to what extent this is as much due to the
high energy of flow for the restricted portion of the Potomac River at the fall-line. This is unlike
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the Susquehanna in 1994 (Miller, et al., 1996) where most of the pollutant metals show about
half dissolved distribution, maybe explained by a greater proportion of particle fall-out behind a
higher density of larger dams. The Rock Creek tributary, downstream of the Potomac fall line,
was sampled routinely and synchronous with the Chain Bridge fall line. Here, the annual
average sample concentration (Fig. 3c) is particulate dominant for all but Mn and Ni, unlike the
other upstream Potomac tributaries discussed in the next section. The range of dissolved and
particulate concentrations for Chain Bridge at base flows is presented as a series of box plots in
Figure 4. While the dissolved concentrations are reasonably consistent for all but Al and Cd, the
particulate concentrations show appreciable temporal variation. This suggests that the process of
particle formation varies throughout the year, depending probably on the seasonal changes in
sources or biogeochemical processes (e.g. winter weathering vs. summer biota), as well as
discharge.
The dissolved concentrations of the Potomac fall line are compared to three other
Potomac basin systems studied by our group during recent years under previous programs. They
include another Potomac sampling during a fall line tributary survey in 1994, the pristine Bear
Branch watershed study (Church, et al., 1998), and the year long EPA-CPB Anacostia river study
during 1994-5. The results (Fig. 5) show that during an earlier study on the Potomac with only
two sample collections, the concentrations are fairly representative for the year. The exceptions
are Cd, Pb and perhaps Zn which were actually lower previously for Cd and Zn, but higher for
Pb. This is consistent with seasonal changes in presumably the soil biogeochemistry of the
watershed responsible for predominant Cd transmission and Pb retention from our previous
studies (Church and Scudlark, 1998; Church, et al., 1998). The Potomac dissolved
concentrations are more than forested Bear Branch, except for Zn where greater foliage density
contributes, and much less than the Anacostia where most of the pollutant metals are derived
from local urban sources.
Total Hg shows fairly consistent concentrations throughout the year (Fig. 6), with some
notable peaks in the winter and summer, which were unusually high. Whether this is typical of
urban airsheds in late summer, or an aberrant sample cannot be ascertained without further
sampling. However, the same peak was observed also in the Rock Creek tributary. The dissolved
and particulate proportions of Hg are about equivalent.
The concentration results were translated into a total annual loading as follows. The
volume weighed mean concentration (concentration times instantaneous discharge divided by
daily discharge) of the daily loads for the sixteen sampling days was multiplied by the annual
discharge as reported at the nearest gauging station (USGS Water Resources Data) during the
Water Years 1996 and 1997. Annual dissolved and particulate loadings are summarized in
Figure 7a, showing that the particulate load dominates the total load, which includes all flow
conditions. The Potomac annual load is then compared to the corresponding loads of the
Susquehanna River at the Conawingo Dam fall line during our previous CBP-MD DNR study in
1992-4 in Figure 7b. This comparison of the total loads for the two major watersheds of the
Chesapeake confirms the dominance of the Susquehanna loading to the Bay. This is
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commensurate with its higher flow and comparable total, if not participate, concentration of the
Susquehanna. This also reflects the equally polluted condition of both systems for non-crustal
elements, which in the case of the Susquehanna includes a series of upstream urban sites, and
acid mine drainage from the regional coal deposits. Also, for the Potomac, while there are some
upstream coal deposits and low grade metamorphic terrain, the main urbanized portion is the
urban/sub-urban corridor above Washington DC, and included at the fall line sampling station.
The annual loadings for the Rock Creek tributary are shown in Figure 7c and b. The
Rock Creek, even as an urban tributary, shows rather uniform dissolved (Fig. 7c) and particulate
(Fig. 7d) concentrations throughout the year. However, some maximum particulate
concentrations for both crustal and pollutant metals occur during the late spring, a period
presumably concurrent with local soil resuspension.
The dissolved and particulate As at the Potomac fall line shows unique seasonal behavior
with a very pronounced peak during the late spring and summer. This is presumably related to
the nutrient behavior of arsenate, which is known to resemble phosphate in its biogeochemistry.
In fact, As is a contaminant of phosphate fertilizer application which probably also reaches the
fall line late during the planting season, continuing to leach out, and like phosphate equilibrated
with the soil as a result of agricultural and general plant growing activity upstream.
B. Potomac Head Water and Tributary Concentrations, Loads and Basin Yields
The headwaters of the Potomac River were sampled twice (May and August 1997) in the
head waters of both the north and south branches. Included were three successive locations
downstream above Chain Bridge, plus two midstream tributaries, and Rock Creek downstream
below the fall line. The dissolved and particulate concentrations at the upstream sites are
summarized as totals in Table 7, along with the corresponding discharges and upstream
watershed areas. The percentage dissolved and particulate distribution upstream at Cumberland
(Fig. 8a), the northern mid-stream tributary Cotoctin (Fig. 8b), as well as the fall line (Fig. 8c)
and the Rock Creek tributary (Fig. 8d) are displayed to show an increasing, if minor, particulate
contribution downstream for most of the watershed. This means the predominant particulate
burden for the Potomac, dominant in May, is contributed mainly (but not only) during periods of
high flow and re-suspended yield within the lower urban watershed.
From the corresponding discharge and watershed area data in Table 7, the total
instantaneous loads and basin yields were calculated and reported in Tables 8 and 9, respectively.
The data are displayed in Figure 9 as a comparison of total metal concentrations during the (a)
May and (b) June head waters surveys. Going downstream, there is rather constant As,
increasing Cu, while Mn, Ni and Cd are maximum upstream at Cumberland and Kitzmiller.
Some metals such as Ni and Mn have higher concentrations during May early in the growing
season, while others such as As, Cd and Cu are higher in August later in the season. Presumably
this reflects seasonal biogeochemical processes, as well as the relative natural and anthropogenic
sources. When translated into a comparison of the instantaneous loads in Figure 10 for (a) May
14
-------
and (b) August 1997, one observes a greater load in the northern branches, including Rock
Creek, less in the northern tributaries, but a general decrease downstream until the major
contribution before the urban DC corridor. Within the urban corridor, Rock Creek is presumably
lower to hydrological protection from run-off as a National Park. Thus, both upstream and
downstream sources appear comparable, and this is confirmed when calculated as basin yields in
Figure 11 (a) May and (b) August, 1997.
C. Potomac Fall Line Concentrations and Discharge
The dissolved and particulate concentrations at the fall line are displayed in Figure 12,
along with the discharge, for (a) crustal element Al, (b) metalloid As, and c) pollutant metals
(represented by Zn). There are about 6-8 large discharge periods, primarily in the Fall, with the
main one during the March 1997 high flow storm event. Only when the discharge is
concentrated around December is there a large crustal particulate concentration from the
accumulative flushing of the watershed. However, for the metalloid and pollutant type metals,
there is a dissolved peak in the late spring not associated with discharge, presumably from the
accumulative effects of the natural and agricultural growing season.
Special attention was focused on a high discharge event in early March 1997 when there
was an intensive sampling over three successive days of high rain fall within the Potomac basin.
Again the data are displayed for the three characteristic metals (Fig. 13). It is apparent that for
Al, the leading hydrograph of discharge carries most of the particulate burden, followed by a
minor dissolved pulse, whereas for As, the two are comparable and peak later in the discharge
hydrograph. For Zn, the dissolved burden is sustained through the discharge hydrograph.
When displayed as a percentage, the particulate burden is totally dominant for all metals
during the first high discharge day, with only some minor dissolved As and Cd proportions
during the last two days (Fig. 14). On an annual basis, it is this high particulate burden which
apparently dominates the metal loading of the Potomac river basin, most of which originates in
its lower reaches. In this respect, contaminated ground water sources with particulate scavenging
or contaminated soils themselves cannot be ruled out.
D, Tidal Potomac Survey
Below the fall line near Georgetown and Rock Creek, and just below the routine Chain
Bridge sampling site, the Potomac River becomes tidal. The result is the greater Potomac
Estuary which extends some hundred kilometers further downstream before confluence with the
main stem of Chesapeake Bay near Piney Point. In fact, this portion of the Potomac comprises
the largest sub-estuary of the Chesapeake. Through its gradient of salinity and turbidity along
with intern'dal wetlands, it is likely to process some portion of those trace elements gaged to
cross the fall line during this study. The importance is that the trace element loading of the
Potomac to Chesapeake Bay proper at the main stem, is in fact determined ultimately by the fate
of these elements within the sub-estuary.
15
-------
The same trace elements were sampled synoptically with this study as part of the EPA
AEOLOS project, but reported here so as to compare to the concentrations upstream in the
watershed. This occurred on two seasonal occasions during the winter (Feb.) and summer (July)
of 1997. The five sampling sites ranged the full length of the estuary from the Anacostia river to
Piney Point. The exact locations and coordinates are listed in Table Ib. The raw dissolved and
particulate concentrations are listed in the appendix as Table A-5.
During February (Fig. 15), both the total (a) and particulate (b) concentrations of most
metals generally go through a minimum near Alexandria and then increase down to Piney Point.
This is most pronounced for the crustal elements Al and Fe, and Zn, and less so for the other
pollutant elements. This may indicate the fact that Alexandria coincides with the major Blue
Plains sewage plant for Washington DC. This plant presumably injects large quantities of
dissolved organic matter and nutrients which may lead to phytoplankton blooms and particle
distribution or removal. Alternatively, as one proceeds down the salinity gradient, the riparian
marshes which normally act as a sink for particulates maybe undergoing ice rafted tidal
resuspension during the winter. However, the dissolved concentrations (c), show little change,
except for Cd which goes through the same minimum, and Cr, Cu and Ni which increase down
estuary in more saline waters. This may reflect reflux to the tidal waters from the diagenetic
alteration in the riparian salt marshes which are more abundant in this portion of the estuary.
During July (Fig. 16), the total (a) and particulate (b) concentrations for the crustal
elements Al, Fe and Mn are quite uniform, while the pollutant trace elements Zn, Cd, Cr, Cu and
Ni increase generally down estuary to Quantico (there were no Piney Point samples in July).
Arsenic (not reported for February) was quite uniform, perhaps reflecting like phosphate a
buffered nutrient. The dissolved concentrations © reflect the same pattern as the total. Again,
this may reflect the diagenetic reflux from intertidal areas down estuary, which should reach a
maximum during the warm summer months of sulfate reduction and burying organisms.
The percentage distribution of dissolved and particulate trace elements (Fig. 17) show the
same pattern for three common sites, perhaps corresponding to the position of the turbidity
maximum. At Reagan National Airport (a) the particulate concentration dominates for crustal
Al, Fe and for Mn, Cr and Zn as well during July. At Quantico (b), the same general pattern
applies for both months. At both locations, the other pollutant elements (Cd, Cu, Ni) are
dominantly dissolved. Down estuary at Piney Point(c), the February particulate distribution is
dominated by crustal Fe and Mn (Al not available) plus Zn.
The overall impression is that the while the concentrations within the tidal Potomac
estuary are similar to those crossing the fall line at Chain Bridge, the redistribution from the
particulate to dissolved phase for the pollutant elements is significantly different. While the
reasons maybe several as noted above (estuarine blooms stimulated by sewage plants, riparian
diagenesis, etc.), the importance is that more of the pollutant trace loading in the Potomac River
may be available for estuarine biota downstream. Depending on the element, this could mean
16
-------
either eutrophic and/or toxic effects in the estuarine portions of both the Potomac and a greater
dissolved contribution to the lower Chesapeake Bay.
VI. SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
In summary; the results from this study of the Potomac river and estuary conclude:
- Upstream, trace element loadings are dominantly dissolved in primary watersheds and
tributaries.
- Downstream the loadings are dominantly particulate at the fall-line, unlike most tributaries.
- Comparison of dissolved tributary concentrations indicate some downstream retention.
- Instantaneous loadings show both mid-stream weathering and downstream urban sources.
- Basin yields show both sources to be important, equal for crustal and urban for pollutant
elements.
- Estuarine concentrations are comparable to that at the fall line, but dissolved processing from
biota or marshes is evident.
These observations lead to the following recommendations for future Potomac studies:
- Dissolved upstream atmospheric and weathering sources are later converted into particulate
loads.
The recommendation is for intra-watershed study of particulate processing.
- Particulate loads during high flow are theorized to include flushing of an historical legacy.
The recommendation is longer term monitoring as global warming escalate
biogeochemical transformations within the watershed.
- High basin yields are unique to the downstream urbanized portions of the river above the fall
line.
The recommendation is for detailed studies on urban runoff in the DC corridor.
- Dominant particulate loading during high flow leads to equivalent estuarine concentrations .
The recommendation is for estuarine studies on the tidal fate and cycling of metals.
17
-------
VII. ACKNOWLEDGMENTS
We wish to acknowledge Mrs. Marie Freeman for her assistance with the field sampling.
We also would like to acknowledge the analytical assistance of Mrs. Weiqi Chen and Ms. K.C.
Filippino. Mrs. Wendy Grot provided the clerical and Brian Norton the graphical assistance in
preparing this report.
VIII. REFERENCES
Castro, M. S., J. R. Scudlark, T. M. Church and R. P. Mason , 2000. "Input-Output budgets
of major ions, trace elements, and mercury for a forested watershed in Western
Maryland". Maryland Power Plant Research Program Report, 72 pp.
Church, T.M. and J.R. Scudlark. 1998. "Trace metals in estuaries: A Delaware Bay
synthesis. "(In:) Metal Speciation and Contamination of Surface Water (J. Baker, ed)
Ann Arbor Press,Inc., Chapt. 1, pp. 1-20.
Church, T.M., J.R. Scudlark, K.M. Conko, O.P. Bricker, K.C. Rice. 1998.
"Transmission of Atmospherically-deposited trace elements trough an undeveloped,
forested Maryland Watershed" Maryland Department of Natural Resources Chesapeake
Bay Research and Monitoring Division, CB93-005-002.
USEPA. 1996. Chesapeake Bay Program, Chesapeake Bay Fall Line Toxics Monitoring
Program Final Report 1994, CBPATRS-144/96,125 pp.
Water Resources Data. Maryland and Delaware Water 1996 and 1997. Volume 1
Surface-Water Data. U.S. Geological Survey Water Data Report MD-DE-96-1. 97-1.
IX. APPENDICES ( ATTACHED TABLES)
18
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Pennsylvania
I /^Maryland
VB A <&.—,
Chain Bridge
Rock Creek
Kitzmiller, MD
E! Cumberland, MD
52 Springfield, WV
|Q Paw-Paw, WV
E Handcock, MD
B Catoctin Creek
53 Monocacy River
HI Point-of-Rocks, MD
<3) Piney Point
@ Quantico
-------
D)
ID
C
O
'•«—•
03
•4—1
c
0)
O
c
O
O
0.0
Al
Fe
Mn
Zn
Blank
Potomac
Cd
Cr Cu
Ni
Pb As Se
Figure 2 Comparison of average field blanks with average Potomac River
concentrations. In most cases, the blank is a small percentage of the
sample.
20
-------
100%
80%
60%
40%
20%
0%
CH Dissolved
iParticulate
Al As Cd Cr Cu Fe Mn Ni Pb Zn
Figure 3a Percent dissolved and particulate distribution of average trace metal
concentrations at the Potomac River fall line during base flow conditions.
21
-------
100%
80%
60%
40%
20%
0%
Dissolved
Particulate
Al As Cd Cr Cu Fe Mn Ni Pb Zn
Figure 3b Percent dissolved and particulate distribution of average trace metal
concentrations at the Potomac River fall line during all flow conditions.
22
-------
Dissolved
Particulate
Al As Cd Cr Cu Fe Mn Ni Pb Zn
*Particulate As not available
Figure 3c Percent dissolved and participate distribution of average trace metal
concentrations at the Rock Creek terminus during base flow conditions.
23
-------
1.0e+2 -
i.oe+o H
c
0)
o
c
o
o
1.0e-2 -
1.0e-3
Dissolved Metals
o
o
o
I I I I I I I I I I I
Al As Cd Cr Cu Fe Mn Ni Pb Se Zn
Particulate Metals
le-^o -
1e+5 -
ro 1e+4 -
^
1 1e+3 '
I 1e+2 -
0
o
O 1e+1 -
1e+0 -
° 0
T T
n no
T S T
° M
oo ° o n
T n ° j_
Al As Cd Cr Cu Fe Mn Ni Pb Zn
Figure 4 Variations in trace metal concentrations at the Potomac fall line during
average base flow samples for dissolved and particulate samples. The
box defines the median, 10th, 25th, 75th and 90th percentiles, and the
circles the extremes of the entire sample distribution.
24
-------
TO
c
0)
o
c
o
o
0)
"o
-------
^ 35 ]
^) 30
c
dissolved
participate
Figure 6 Total dissolved and particulate mercury concentrations (ng/l) at the
Potomac fall line over time.
26
-------
1000 i
100 -
CO
0
0)
o
"i_
"53
E
Dissolved Load
Particulate Load
Al Fe Mn Zn Cr Ni Cu Pb Cd As
Figure 7 a Trace metal loading at the Potomac fall line over all flow conditions.
21
-------
106
05
CD
c
o
•4—«
o
-t—>
CD
E
105 -
104 -
103 -
102 -
10° -
10
-1
Potomac Chain Bridge
Susquehanna Fall Line
Al Fe Mn Zn Cr Ni Cu Pb Cd As
Figure 7b Comparison of the total trace metal loading at the Potomac and
Susquehanna fall lines over all flow conditions. As for the flow, the
Susquehanna dominates.
28
-------
O)
c
g
to
•4— •
C
CD
O
C
O
O
1000
100
10
0.1
IAI OFe SMn »Zn
12/101/15 2/11 2/25 4/15 4/25 5/7 6/11 6/25 7/28 8/14
10
O)
C
g
"Is
"c
CD
O
C
O
O
0.1
0.01
12/101/15 2/11 2/25 4/15 4/25 5/7 6/11 6/25 7/28 8/14
Figure 7c Comparison of the dissolved trace metal loading at the Rock Creek
terminus for each sampling period.
29
-------
D)
C
o
15
•4— »
C
0
o
C
o
o
D)
C
g
1000
100
10
1
0.1
0.01
0.001
IAI OFe
Zn
12/101/15 2/11 2/25 4/15 4/25 5/7 6/11 6/25 7/28 8/14
1
0.1
0.01
0.001
C
0
O
o 0.0001
o
0.00001
Cu OCr HNi MAs
12/101/15 2/11 2/25 4/15 4/25 5/7 6/11 6/25 7/28 8/14
Figure 7d Comparison of the particulate trace metal loading at the Rock Creek
terminus for each sampling period .
30
-------
1 UU70
80%
60%
40%
20%
no/
M
Dissolved
• Particulate
.
^•MH.
••••
Al As Cd Cr Cu Fe Mn Ni Zn
IUU/0
80%
60%
40%
20%
no/.
Dissolved
• Particulate
^amm
.
^^mamm
_
•^•B
Al As Cd Cr Cu Fe Mn Ni Zn
Figure 8a Percent dissolved and particulate trace metal concentrations an upper
tributary of the Potomac. The sampling occurred during the early (May)
and late (August) summer period. Cumberland, MD is on the north
branch of the Potomac.
31
-------
100%
80%
60%
40%
20%
0%
Dissolved
Particulate
Al As Cd Cr Cu Fe Mn Ni Zn
IUU /O
80%
60%
40%
20%
Dissolved
• Particulate
•I
.
mi
_
_
•IM
.
•••••
_
•^^^^•^^^H
_
••
Al As Cd Cr Cu Fe Mn Ni Zn
Figure 8b Percent dissolved and particulate trace metal concentrations a middle
tributary of the Potomac. The sampling occurred during the early (May)
and late (August) summer period. Cactoctin, MD is midway on the main
stem of the Potomac.
32
-------
Dissolved
Particulate
Al As Cd Cr Cu Fe Mn Ni Zn
100%
80%
60%
40%
20%
0%
EH Dissolved
• Particulate
Al As Cd Cr Cu Fe Mn Ni Zn
Figure 8c Percent dissolved and participate trace metal concentrations downstream
on the main stem of the Potomac. The sampling occurred during the
early (May) and late (August) summer period. Chain Bridge DC is near
the fall line.
33
-------
a Dissolved
• Particulate
Al As Cd Cr Cu Fe Mn Ni Zn
80%
60%
40%
20%
n%
•
.
a Dissolved
• Particulate
•MB^B
_
•^•^H^M^HH
Al As Cd Cr Cu Fe Mn Ni Zn
Figure 8d Percent dissolved and particulate trace metal concentrations for the
terminus of Rock Creek, a lower tributary of the Potomac. The sampling
occurred during the early (May) and late (August) summer period.
34
-------
O)
O
c
O
O
Kzm Spf Cmb Paw Hck Cac Mon PoR ChB RkC
20
15
10
5
0
Zn
CUMay
•August
Kzm Spf Cmb Paw Hck Cac Mon PoR ChB RkC
Kzm Spf Cmb Paw Hck Cac Mon PoR ChB RkC
Figure 9a Total Cu, Zn, and As concentrations during early (May) and late
(August) summer on the head waters and tributaries of the Potomac.
The sites are generally upstream to downstream going from left to right.
35
-------
Kzm Spf Cmb Paw Hck Cac Mon PoR ChB RkC
150
O) 100
o
c
o
o
50
Mn
CD May
•August
Kzm Spf Cmb Paw Hck Cac Mon PoR ChB RkC
Kzm Spf Cmb Paw Hck Cac Mon PoR ChB RkC
Figure 9b Total Ni, Mn, and Cd concentrations during early (May) and late
(August) summer on the head waters and tributaries of the Potomac. The
sites are generally upstream to downstream going from left to right.
36
-------
CO
CO
O
CO
CO
O
1000
100
10
1
0.1
0.01
0.1
0.01
0.001
Al QFe SMn MZn
Spf Cmb Paw Hck Cac Mon PoR RkC
Cu EDCr HNi «As
Spf Cmb Paw Hck Cac Mon PoR RkC
Figure 10a Instantaneous loads of trace metals during early (May) summer on the
head waters and tributaries of the Potomac. The sites are generally
upstream to downstream going from left to right.
37
-------
03
CO
O
s-
3
1000
100
10
0.1
0.01
10
0.1
0.01
0.001
0.0001
IAI OFe HMn HZn
Spf Cmb Paw Hck Cac Mon PoR RkC
iCu ElJCr HNi
lAs
Spf Cmb Paw Hck Cac Mon PoR RkC
Figure 10b Instantaneous loads of trace metals during the late (August) summer on
the head waters and tributaries of the Potomac. The sites are generally
upstream to downstream going from left to right.
38
-------
10000
C\J
E
.
c
'co
CO
00
Spf Cmb Paw Hck Cac Mon PoR ChB RcK
Spf Cmb Paw Hck Cac Mon PoR ChB RcK
Figure 11 a Basin yields of trace metals during early (May) summer on the head
waters and tributaries of the Potomac. The sites are generally upstream
to downstream going from left to right.
39
-------
32
0)
CO
00
(N
E
0)
CO
00
Spf Cmb Paw Hck Cac Mon PoR ChB RcK
Spf Cmb Paw Hck Cac Mon PoR ChB RcK
Figure 11b Basin yields of trace metals during the late (August) summer on the head
waters and tributaries of the Potomac. The sites are generally upstream
to downstream going from left to right.
40
-------
f
(D
S>
05
O
D)
D)
O
C
O
O
Discharge
Particulate Al
Dissolved Al
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jly Aug
Figure 12a Concentrations of dissolved and participate aluminum with annual
discharge at the Potomac fall line.
41
-------
t
0)
(0
o
(/>
b
o
c
o
O
Discharge
Participate As
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jly Aug
Figure 12b Concentrations of dissolved and participate arsenic with annual
discharge at the Potomac fall line.
42
-------
^
m
Jl
o
Q
/uuuu -
60000 -
50000 -
40000 -
30000 -
20000 -
T
| ? * • Discharge
* ! I . t It — • — Particulate Zn
;:; ? J s fT | •
;y | ? i^ i \\
^* - * JV^ i« ^
i? iji 4 ^1 iN* Mi t
•;•; M *i ^i:j« ;f*li !
H !i R*^ s ,i« *
•s s t N a^A'X •
10000
O)
O)
o
c
o
o
Dissolved Zn
Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jly Aug
Figure 12c Concentrations of dissolved and participate zinc with annual
discharge at the Potomac fall line.
43
-------
70000
60000 -
50000 -
o
c
o
O
10000 -
60 -
40 -
20 -
0
Discharge
Particulate Al
Dissolved Al
2/19
2/24
3/01
3/06
3/11
Figure 13a Concentrations of dissolved and participate aluminum during peak
discharge at the Potomac fall line.
44
-------
70000
Discharge
—•»— Particulate Al
Dissolved Al
2/19
2/24
3/01
3/06
3/11
Figure 13b Concentrations of dissolved and particulate arsenic during peak
discharge at the Potomac fall line.
45
-------
3, 60000 -
O) 50000 -
TO
.c 40000 H
o
CO
pj 30000 H
20000 -
10000 -
D)
O
c
o
O
Discharge
Particulate Zn
2/19
2/24
3/01
3/06
3/11
Figure 13c Concentrations of dissolved and participate zinc during peak
discharge at the Potomac fall line.
46
-------
EH Dissolved
• Particulate
Al As Cd Cr Cu Fe Mn Ni Pb Zn
Figure 14 Percent dissolved and particulate trace metal distribution at the Potomac
fall-line during the three days of peak flow corresponding to the storm
intensive during Spring 1997.
47
-------
O)
c
o
Is
•*-•
0)
o
c
o
o
O)
c
o
'2
•*-•
c
0)
o
c
o
o
Anacostia Natn'l Apt Alexandria Quantico Piney Pt
10
0.1
0.01
Cd aCr HCu
Anacostia Natn'l Apt Alexandria Quantico Piney Pt
Figure 15a Comparison of total concentrations for tidal Potomac River during
February 1997.
48
-------
100
D)
c
o
to
+-*
c
CD
O
c
o
O
O)
c
g
IS
^— •
c
CD
O
c
o
O
10
0.1
10
0.1
0.01
Anacostia Natn'l Apt Alexandria Quantico Piney Pt
Cd CUCr HCu HNi
Anacostia Natn'l Apt Alexandria Quantico Piney Pt
Figure 15b Comparison of dissolved concentrations for tidal Potomac river during
February 1997.
49
-------
O)
c
,o
03
"c
0)
O
c
O
O
Anacostia Natn'l Apt Alexandria Quantico Piney Pt
As
O)
c
CD
O
C
O
O
0.1
0.01
0.001
0.0001
Anacostia Natn'l Apt Alexandria Quantico Piney Pt
Figure 15c Comparison of particulate concentrations for tidal Potomac river during
February 1997.
50
-------
1000
O)
c
o
'•g
•t— •
c
CD
O
c
o
O
100
10
IAI OFe HMn
Natn'l Apt Alexandria Quantico
10
lOd OCr HCu HNi HAs
D)
C
o
c
o
O
0.1
0.01
Not
Available
Piney Pt
Not
Available
Natn'l Apt Alexandria Quantico
Piney Pt
Figure 16a Comparison of total concentrations for tidal Potomac river during July
1997.
51
-------
10
O)
c
g
'2
•+-«
o
o
c
o
O
0)
c
o
c
o
o
c
o
o
0.1
10
0.1
0.01
Natn'l Apt Alexandria Quantico
lOd OCr SCu HNi HAs
Not
Available
Piney Pt
Not
Available
Natn'l Apt Alexandria Quantico
Piney Pt
Figure 16b Comparison of dissolved concentrations for tidal Potomac river during July
1997.
52
-------
100
D)
c
o
to
•I— I
c
CD
O
c
o
o
O)
c
o
c
0
o
c
o
o
10
0.1
Not
Available
Natn'l Apt Alexandria Quantico
Piney Pt
Cd OCr mCu HNi HAs
0.001
0.01
Not
Available
Natn'l Apt Alexandria Quantico
Piney Pt
Figure 16c Comparison of particulate concentrations for tidal Potomac river during
July 1997.
53
-------
100%
80%
60%
40%
20%
0%
100%
80%
60%
40%
20%
0%
Potomac River at Natn'l Airport, 2/25/97
IMMJj
Al Cd Cr Cu Fe Mn Ni Zn
Potomac River at Natn'l Airport, 7/28/97
HID
Al Cd Cr Cu Fe Mn Ni Zn
n Dissolved
Particulate
Figure 17a Percent average sample concentration in tidal Potomac river at National
Airport during February and July 1997.
54
-------
100%
80%
60%
40%
20%
0%
100%
Potomac River at Quantico , 2/25/97
Al Cd Cr Cu Fe Mn Ni Zn
Potomac River at Quantico, 7/28/97
Cd Cr Cu Fe Mn Ni Zn
CU Dissolved
• Particulate
Figure 17b Percent average sample concentration in tidal Potomac river at Quantico
during February and July 1997.
55
-------
Al Cd Cr Cu Fe Mn Ni Zn
EU Dissolved
• Particulate
Figure 17c Percent average sample concentration in tidal Potomac river at Piney
Point during February and July 1997.
56
-------
Table 1a Locations of sites included in the Headwater and Tributary Survey, noted
as symbols in the Figures and USGS site identifications (numbers).
Kzm - Kitzmiller, MD (15955) north branch of the Potomac River. Samples were
collected about 3/10 of a mile upstream from the gauging station on the left bank
downstream from the bridge on State Highway 38.
Cmb - Cumberland -Wiley Ford, MD (1603) north branch of the Potomac River.
Samples were collected from the bridge next to the gauging station at the approximate
center-of-flow, on the downstream side of the Wiley-Ford Bridge 2.0 miles south of
Cumberland.
Spf - Springfield, WV (16085) south branch of the Potomac River. Samples were
collected 4/10 of a mile downstream from the bridge on State Highway 28, 2.0 miles east
of Springfield.
Paw - Paw-Paw, WV (1610) main-stem of the Potomac River. Samples were collected
about 250 feet upstream from the bridge on State Highway 51, 3.3 miles downstream from
the Little Capon River.
Hck - Hancock, MD (1613) main-stem of the Potomac River. Samples were collected
about 2/10 of a mile downstream from the bridge on highway 522, 1.2 miles upstream
from Tonoloway Creek.
Cac - Catoctin Creek (1637) tributary of the Potomac River above the fall line. Samples
were collected about 300 feet downstream from the bridge on State Route 17, 1.3 miles
south of Middletown.
Mon - Monacacy River (1639) tributary of the Potomac River above the fall line.
Samples were collected at Reich's Ford Bridge, 1.1 miles downstream from U.S. Route
40, 2.0 miles southeast of Frederick, MD.
PoR - Point-of-Rocks, MD (16385) main-stem of the Potomac River. Samples were
collected on left bank at the downstream side of the bridge on U.S. Route 15.
ChB - Chain Bridge, MD (16465) routine fall line sampling site on the Potomac River.
Samples were collected as integration of three samples near the center of flow
RoC - Rock Creek, DC (0164800) tributary of the Potomac River below the fall line.
Samples were collected near the National Park headquarters.
57
-------
Table 1b Tidal Potomac River sampling locations.
Piney Pt, at mouth of river into Chesapeake Bay. Samples collected near Piney Point,
MD.
Quantico, samples collected near Quantico, Virginia (77°16', 38°31').
Alexandria, samples taken near Alexandria, Virginia (77°02', 38°46').
National Airport, samples taken near Regan National Airport, across the river from
Geisboro Point, MD (77°01'30B 38°51'03").
Anacostia, samples were taken near the confluence of the Anacostia and Potomac
Rivers (77°01'01", 38°51'30").
58
-------
Table 2 Trace elements, analytical techniques and detection limits (ug/l). Detection
limits for participate analyses (ug/l) are calculated assuming 0.1 mg dry
weight particulate per 25 ml of sample.
Constituent
Method
Detection Limit
Al (Aluminum), particulate
Al, dissolved
As, (Arsenic), particulate
As, dissolved
Cd (Cadmium), particulate
Cd, dissolved
Cr (Chromium), particulate
Cr, dissolved
Cu (Copper), particulate
Cu, dissolved
Fe (Iron), particulate
Fe, dissolved
Hg (Mercury), particulate
Hg, dissolved
Pb, (Lead), particulate
Pb, dissolved
Mn (Manganese), particulate
Mn, dissolved
Ni (Nickel), particulate
Ni, dissolved
Zn (Zinc), particulate
Zn, dissolved
AA.HGA
AA.HGA
Hydride, AAS
Hydride, AAS
AA.HGA
AA.HGA
AA.HGA
AA.HGA
AA.HGA
AA.HGA
AA.HGA
AA.HGA
CVAFS
CVAFS
AA.HGA
AA.HGA
AA.HGA
AA.HGA
AA.HGA
AA.HGA
AA.HGA
AA.HGA
3.0
0.12
0.1
0.007
0.1
0.006
3.0
0.1
3.0
0.12
2.0
0.05
0.05
0.00002
3.0
0.12
3.0
0.10
3.0
0.12
3.0
0.14
59
-------
Table 3
Project schedule.
Activity
FalM 996
Spring 1997
Summer 1997
Fall 1997
Spring 1998
April 1999
July 2000
Description and Dates
Began Potomac River Basin sampling at the fall line
First synoptic sampling of Potomac headwaters
Second synoptic sampling of Potomac headwaters
Completed sampling for Potomac River at the fall line
Data submitted toCBPTLRI
Preliminary report submitted for review
Final report submitted to CBP
60
-------
Table 4 Replicate analyses of (a) dissolved and (b) particulate trace metals in the
Potomac River mainstem.
(a) Replicate analyses of dissolved trace metals in the Potomac River main stem
Sample ID
1 0/23/96
01/15/97
03/05/97
05/18/97
05/18/97
Potomac A
Potomac B
Potomac C
Mean
StdDev
Potomac A
Potomac B
Mean
Potomac A
Potomac B
Mean
Paw-Paw A
Paw-Paw B
Paw-Paw C
Mean
Std Dev
Springfield A
Springfield B
Springfield C
Mean
Std Dev
Al
ug/L
30.6
28.3
24.0
27.7
2.73
27.8
20.2
24.0
5.06
6.43
5.75
2.67
4.00
3.34
ND
3.35
3.14
2.74
3.08
0.25
As
ug/L
0.154
0.163
0.130
0.149
0.014
0.104
0.081
0.093
0.135
0.158
0.147
0.089
0.071
0.080
ND
0.101
0.098
0.106
0.102
0.003
Cd
ug/L
0.180
0.027
ND
0.069
ND
0.100
ND
ND
0.548
0.275
0.412
0.004
0.023
0.014
ND
0.044
0.127
0.028
0.066
0.043
Cr
ug/L
0.13
0.18
0.18
0.16
0.02
0.20
0.19
0.20
0.10
0.10
0.10
0.06
0.09
0.08
ND
0.06
0.06
0.06
0.06
0.00
Cu
ug/L
1.00
0.81
0.75
0.85
0.11
0.62
0.60
0.61
1.45
1.39
1.42
0.53
0.61
0.57
ND
0.50
0.55
0.47
0.51
0.03
Fe
ug/L
63.8
53.4
46.7
54.6
7.03
34.2
27.8
31.0
6.06
5.53
5.80
5.20
4.87
5.04
ND
5.81
5.97
5.14
5.64
0.36
Mn
ug/L
2.85
2.42
2.07
2.45
0.32
10.3
10.4
10.3
3.15
2.73
2.94
24.8
22.7
23.7
ND
5.28
5.51
4.79
5.19
0.30
Ni
ug/L
0.98
0.96
0.54
0.83
0.20
0.84
0.61
0.73
1.7
1.4
1.6
1.6
1.5
1.5
ND
0.85
0.93
0.73
0.84
0.08
Pb
ug/L
<0.05
<0.05
0.060
ND
ND
<0.05
<0.05
0.000
<0.05
<0.05
ND
<0.05
<0.05
ND
ND
<0.05
<0.05
<0.05
ND
ND
Se
ug/L
0.091
0.064
0.065
0.073
0.012
0.075
0.103
0.089
0.102
0.098
0.100
0.089
0.058
0.063
0.061
0.014
0.063
0.044
0.054
0.054
0.008
Zn
ug/L
1.21
1.90
1.14
1.42
0.34
0.81
0.62
0.72
1.68
1.65
1.67
ND
0.42
0.35
0.39
ND
0.69
0.72
0.40
0.60
0.14
ND = Not Determined
(b) Replicate analyses of particulate trace metals in the Potomac River main stem
Sample ID
10/23/96
10/23/96
10/23/96
05/18/97
05/18/97
05/18/97
08/03/97
08/03/97
Potomac A
Potomac B
Potomac C
Mean
StDev
Paw Paw A
Paw Paw B
Paw Paw C
Mean
StDev
Cumberland A
Cumberland B
Cumberland C
Mean
SLDev
Al
ug/g
123
122
121
122
0.8
3.0
ND
5.1
2.7
2.1
As
ug/g
0.092
0.086
0.076
0.085
0.007
0.0003
0.0004
0.0003
0.0003
0
Cd
ug/g
3.03
2.45
1.73
2.40
0.53
0.0001
0.0001
0.0001
0.0001
0
Cr
ug/g
4.3
3.3
3.3
3.6
0.5
0.003
0.004
0.002
0.003
0.001
Cu
ug/g
4.9
3.9
2.5
3.7
1.0
0.002
0.002
0.002
0.002
0.000
* Sample was lost when
1.5
1.6
1.5
0.05
0.0007
0.0002
0.0004
0.0002
0.003
0.001
0.002
0.001
0.003
0.002
0.002
0.001
0.003
0.001
0.002
0.001
Fe
ug/g
0.7
5.5
0.2
2.1
2.4
2.9
ND
4.1
2.3
1.7
Mn
ug/g
25.1
18.9
17.7
21
3
0.12
ND
0.17
0.10
0.07
Ni
ug/g
1.42
1.08
0.64
1.0
0.3
0.004
0.005
0.001
0.003
0.002
Pb
ug/g
3
7
5
5.1
1.3
0.000
0.001
0.001
0.001
0
Zn
ug/g
2.56
3.50
0.50
2.19
1.25
0.017
0.014
0.012
0.014
0.002
bottle cracked.
1.6
1.7
1.6
0
0.67
0.24
0.45
0.22
0.003
0.001
0.002
0.001
0.001
0.000
0.001
0
0.038
0.012
0.025
0.013
ND = Not Determined
61
-------
Table 5 Total (dissolved plus participate) metal concentrations at the
Potomac River fall line for the sixteen routine samplings.
Date
10/23/96
10/23/96
10/23/96
10/23/96
10/23/96
11/22/96
12/10/96
01/15/97
02/11/97
02/25/97
03/05/97
03/06/97
03/07/97
04/15/97
04/25/97
05/07/97
05/21/97
06/11/97
06/25/97
07/28/97
08/14/97
COF
grab a
grab b
grab c
Xsec
std
Al
(ug/L)
1730
560
6620
3500
38
780
60000
510
1200
1070
56600
14700
9500
1160
1570
4550
10400
1980
8180
240
25
16544
ND= Not Determined
As
(ug/L)
1.7
0.80
1.2
1.6
0.21
0.44
2.4
0.51
0.25
0.38
51
28
12
0.08
0.10
0.28
4.1
3.3
0.91
0.69
0.46
12
Cd
(ug/L)
0.08
0.10
0.09
0.27
0.01
0.06
0.16
0.16
0.06
0.46
23
320
1.31
0.44
0.34
0.32
1.45
1.30
0.12
0.07
0.04
68
Cr
(ug/L)
7.0
2.7
4.1
5.0
0.12
1.8
6.9
4.4
1.7
3.4
1300
340
130
1.0
0.92
6.1
47
20
6.6
4.5
0.12
281
'Missing the participate data for this sample.
Cu
(ug/L)
8.7
4.1
4.1
5.3
0.89
1.3
11
3.4
1.8
3.2
490
150
55
0.40
1.2
3.6
42
22
5.3
3.7
1.8
106
Fe
(ug/L)
1300
520
3540
2620
41
600
36000
1280
810
2160
28200
15700
4890
870
1400
3480
5860
1330
7200
410
15
9329
Mn
(ug/L)
800
2260
26
900
2
240
3100
93
150
36
6000
780
41
30
49
130
59
97
72
58
2.6
1419
Ni
(ug/L
)
2.0
1.2
6.0
1.7
0.9
1.1
4.1
4.7
3.4
4.7
670
210
77
1.1
0.9
3.5
68
26
4.8
5.3
1.2
146
Pb
(ug/L)
4.4
1.7
2.5
3.0
ND
0.71
5.3
1.4
0.44
1.2
380
170
34
0.14
0.09
1.3
15
20
1.7
2.1
>0.05
86
Se**
(ug/L)
0.09
0.06
0.07
0.09
0.10
0.07
0.09
0.18
0.08
0.08
ND
ND
0.07
ND
0.07
0.11
0.14
0.05
0.12
0.15
0.15
0.05
Zn
(ug/L)
28.0
19.6
20.0
26.3
3.7
4.6
40.2
10.7
6.3
12.4
3900
1730
570
2.9
2.5
12.4
220
160
25.3
27.7
2.7
883
** Se is dissolved only -no particulate data
62
-------
Table 6 Total (dissolved plus participate) metal loading at the Potomac River
fall line and downstream at Rock Creek.
kg/Year
Al
As
Cd
Cr
Cu
Fe
Mn
Ni
Pb
Se
Zn
Potomac
16000
220
70
120
1000
13000
2200
810
<5
80
1100
Dissolved Participate
Rock Creek Potomac Rock Creek
1300
NR
10
10
110
9000
4500
140
<5
NR
140
2570000
880
1800
13000
7100
1750000
110000
10000
5000
NR
51000
2000
NR
<5
6
7
1400
160
<5
<5
NR
30
Total
Potomac Rock
2600000
1100
1800
13000
8200
1800000
110000
11000
5000
80*
52000
Creek
3300
NR
10
20
120
10000
4700
140
<5
NR
170
NR = Not Reported
'Based on dissolved only
63
-------
Table 7 Total (dissolved plus a participate) metal concentrations at the head
water and tributary sites on the Potomac River shown in Fig. 1, with
the site symbols listed in Table 2.
Locations*
Kitzmiller
Kitzmiller
Springfield
Springfield
Cumberland
Cumberland
Paw Paw
Paw Paw
Hancock
Hancock
Catocin
Catoctin
Monocacy
Monocacy
Point of
Rocks
Point of
Rocks
Chain Bridge
Chain Bridge
Date
05/18/97
08/03/97
05/18/97
08/03/97
05/18/97
08/03/97
05/18/97
08/03/97
05/18/97
08/03/97
05/21/97
07/28/97
05/21/97
07/28/97
05/21/97
07/28/97
05/21/97
07/28/97
Discharge
cfs
NA
NA
938
207
976
336
2060
636
2510
747
29
7
32
14
5030
4850
5360
4500
'The site locations are listed on Table
2.
Watershed
sq miles
225
225
1486
1486
875
875
3109
3109
4073
4073
67
67
817
817
9651
9651
11570
11570
Al
ug/L
8.6
59
9.0
5.7
12
62
7.3
17
3.0
72
25
8.7
4.5
92
20
12
1040
240
As
ug/L
0.008
0.006
0.10
0.31
0.19
0.29
0.080
0.28
0.066
0.32
0.030
0.15
0.096
0.50
0.005
0.25
0.41
0.69
Cd
ug/L
0.05
0.4
0.07
0.3
0.04
0.4
0.01
0.04
0.06
1.4
0.05
0.02
0.04
0.05
0.003
0.03
0.14
0.07
Cr
ug/L
0.01
0.06
0.06
0.11
0.27
0.24
0.08
0.09
0.08
0.14
0.13
0.04
0.08
0.07
0.11
0.06
4.7
4.5
Cu
ug/L
0.59
0.42
0.51
0.63
0.61
0.82
0.57
0.72
0.62
1.0
1.0
1.4
0.93
2.0
0.09
0.70
4.2
3.7
Fe
ug/L
0.5
5.0
11
5.9
27
34
8.5
16
7.5
54
19
31
11
67
18
17
590
410
Mn
ug/L
120
73
5.4
5.2
140
40
24
5.5
1.5
3.5
26
3.3
7.9
9.1
1.6
4.6
59
58
Ni
ug/L
6.8
5.4
0.84
0.82
6.3
3.1
1.5
1.8
1.9
1.6
0.79
0.45
0.63
0.95
0.08
0.52
6.8
5.3
Pb
ug/L
0.0004
0.3
0.0007
0.004
0.002
0.09
0.001
0.0005
0.0002
0.02
0.002
0.001
0.003
0.02
0.04
0.001
1.5
2.1
Se"
ug/L
0.17
0.16
0.05
0.06
0.19
ND
0.06
0.11
0.09
0.09
0.08
0.08
0.09
0.17
0.07
0.05
0.14
0.15
Zn
ug/L
6.7
3.2
0.61
0.28
1.9
1.0
0.40
1.3
0.62
0.76
0.38
0.28
1.2
2.2
0.44
0.66
22
28
**Seis
dissolved
only
64
-------
Table 8 Total (dissolved plus participate) metal loadings at the head water and tributary sites on the Potomac River.
Location
Springfield
Springfield
Cumberland
Cumberland
Paw Paw
Paw Paw
Hancock
Hancock
Catocin
Catocin
Monocacy
Monocacy
Point of Rocks
Point of Rocks
Chain Bridge
Chain Bridge
Rock Creek
Rock Creek
Date
05/18/97
08/09/97
05/18/97
08/09/97
05/18/97
08/09/97
05/18/97
08/09/97
05/21/97
07/28/97
05/21/97
07/28/97
05/21/97
07/28/97
05/21/97
07/28/97
05/07/97
07/28/97
Discharge
cfs
938
207
976
336
2060
636
2510
747
29
7
32
14
5030
4850
5360
4500
46
27
Watershed
sq miles
1486
1486
875
875
3109
3109
4073
4073
67
67
817
817
9651
9651
11570
11570
62
62
Al
kg/day
21
2.9
29
51
37
27
19
130
1.8
0.1
0.4
3.2
240
140
13600
2600
16
0.35
As
kg/day
0.23
0.16
0.46
0.24
0.41
0.44
0.41
0.59
0.002
0.003
0.008
0.02
0.1
2.9
5.4
7.6
NR
NR
Cd
kg/day
0.15
0.17
0.1
0.3
0.07
0.07
0.34
2.6
0.004
< 0.001
0.003
0.002
0.04
0.33
1.8
0.8
0.01
< 0.001
Cr
kg/day
0.15
0.054
0.66
0.20
0.40
0.14
0.50
0.25
0.009
0.001
0.007
0.003
1.4
0.8
62
49
0.01
0.01
Cu
kg/day
1.2
0.3
1.5
0.7
2.9
1.1
3.8
1.9
0.07
0.02
0.07
0.07
1.1
8.3
55
40
0.2
0.15
Fe
kg/day
24
3.0
65
28
43
24
46
99
1.3
0.5
0.8
2.3
220
210
7700
4500
25
3.0
Mn
kg/day
12
2.6
340
33
120
8.6
9.2
6.3
1.8
0.06
0.6
0.3
20
54
770
640
3.2
3.6
Ni
kg/day
1.9
0.4
15
2.5
7.7
2.8
12
2.9
0.06
0.01
0.05
0.03
1.0
6.2
90
58
0.2
0.1
Pb
kg/day
0.002
0.002
0.005
0.08
0.005
0.001
0.001
0.04
< 0.001
< 0.001
< 0.001
0.001
0.44
0.01
19
23
< 0.001
< 0.001
Se*
kg/day
0.12
0.03
0.44
< 0.001
0.31
0.18
0.53
0.16
0.005
0.001
0.007
0.006
0.89
0.56
1.8
1.7
NR
NR
Zn
kg/day
1.4
0.14
4.5
0.83
2.0
2.1
3.8
1.4
0.03
<0.01
0.09
0.08
5.4
7.9
280
300
0.07
0.07
*Se loads based on dissolved only
65
-------
Table 9 Total (dissolved plus participate) metal basin yields at the head water and tributary sites on the PotomacRiver.
Location
Springfield
Springfield
Cumberland
Cumberland
Paw Paw
Paw Paw
Hancock
Hancock
Catocln
Catocln
Monocacy
Monocacy
Point of
Rocks
Point of
Rocks
Chain Bridge
Chain Bridge
Rock Creek
Rock Creek
Date
05/18/97
08/09/97
05/18/97
08/09/97
05/18/97
08/09/97
05/18/97
08/09/97
05/21/97
07/28/97
05/21/97
07/28/97
05/21/97
07/28/97
05/21/97
07/28/97
05/07/97
07/28/97
Discharg
e
cfs
938
207
976
336
2060
636
2510
747
29
7
32
14
5030
4850
5360
4500
46
27
Watershed
sq miles
1486
1486
875
875
3109
3109
4073
4073
67
67
817
817
9651
9651
11570
11570
62
62
Al
g/day/sq
ml
14
19
33
58
12
8.7
4.6
32
26
22
0.4
3.9
25
14
1200
22
260
6.0
As
g/day/sq mi
0.16
0.1
0.53
0.27
0.13
0.14
0.10
0.14
0.32
0.39
0.01
0.02
0.01
0.30
0.46
0.66
NR
NR
Cd
g/day/sq
ml
0.10
0.12
0.11
0.35
0.02
0.02
0.08
0.64
0.06
< 0.001
0.004
0.002
0.004
0.03
0.16
0.07
< 0.001
< 0.001
Cr
g/day/sq
mi
0.10
0.04
0.75
0.23
0.13
0.05
0.12
0.06
0.14
0.01
0.008
0.003
0.14
0.08
5.3
4.3
< 0.001
< 0.001
Cu
g/day/sq
ml
0.79
0.21
1.7
0.77
0.93
0.36
0.94
0.46
1.1
0.36
0.09
0.09
0.12
0.87
4.8
3.5
0.003
0.002
Fe
g/day/sq
mi
16
2.0
74
32
14
7.8
11
24
20
7.8
1.0
2.8
23
22
660
390
0.40
0.05
Mn
g/day/sq
mi
8.3
1.8
340
37
39
2.8
2.2
1.6
28
0.84
0.76
0.38
2.1
5.6
66
55
0.05
0.06
Ni
g/day/sq mi
1.3
0.28
17
2.9
2.5
0.9
2.9
0.71
0.83
0.12
0.06
0.04
0.1
0.64
7.7
5.0
0.003
0.002
Pb
g/day/sq
ml
0.001
0.001
0.06
0.09
0.002
< 0.001
< 0.001
0.01
< 0.001
< 0.001
< 0.001
0.001
0.05
0.001
1.7
2.0
< 0.001
< 0.001
Se*
g/day/sq mi
0.08
0.02
0.51
< 0.001
0.10
0.06
0.13
0.04
0.08
0.02
0.008
0.007
0.09
0.06
0.06
0.14
NR
NR
Zn
g/day/sq ml
0.95
0.10
5.1
0.95
0.65
0.67
0.93
0.34
0.40
<0.01
0.11
0.09
0.56
0.82
24
26
0.01
0.01
66
-------
Table A-1 Comparison of trace metal concentrations with EPA standard
reference materials; (1) natural river water standard water SLRS-3; (2)
natural river sediment standard (BCSS-1).
EPA Std.
Lab
Average
S.D.
Al
14.5
14.5
14.3
14.9
15.1
14.7
0.4
Cd
0.725
0.773
0.729
0.732
0.741
0.744
0.02
Fe
2.90
3.06
3.23
3.37
3.00
3.20
0.20
Cr
2.90
3.11
3.00
2.82
3.02
3.00
0.10
Cu
2.90
2.82
2.78
3.23
2.95
2.90
0.20
Ni
2.90
3.00
2.90
3.22
3.00
3.00
0.14
Mn
2.90
2.77
3.04
2.92
2.95
2.90
0.10
Zn
2.90
2.81
2.88
2.94
2.90
2.90
0.10
Pb
2.90
2.95
2.82
2.84
2.96
2.90
0.10
67
-------
Table A-2 Primary metal concentration data for (a) dissolved and (b)
paniculate fractions at the Potomac River fall line samples.
(a) Dissolved Concentrations
Date
10/23/96
11/22/96
12/10/96
01/15/97
02/11/97
02/25/97
03/05/97
03/06/97
03/07/97
04/25/97
05/07/97
06/11/97
06/25/97
07/28/97
08/14/97
Date
10/23/9&-o-f
10/23/9grabc
10/23/9§rabb
10/23/9§raba
11/22/96
12/10/96
01/15/97
02/11/97
02/25/97
03/05/97
03/06/97
03/07/97
04/15/97
04/25/97
05/07/97
05/21/97
06/11/97
06/25/97
07/29/97
08/14/97
Al
ug/L
38
ND
28
24
25
18
6.5
60
28
25
15
10
21
22
24
Al
ug/L
1700
3500
6600
530
780
60000
470
1200
1100
56600
14700
9500
1200
1500
4540
10400
1950
8160
220
9.20
As Cd
ug/L ug/L
0.210.014
0.13 ND
0.120.011
0.090.100
0.080.044
0.060.340
0.140.350
0.120.410
0.140.300
0.090.268
0.080.058
0.220.077
0.340.027
0.550.015
0.460.042
(b)
As Cd
ug/L ug/L
1.6 0.080
1.4 0.092
1.1 0.086
0.640.076
0.31 0.057
2.3 0.15
0.320.057
0.170.017
0.32 0.12
51 23
28 320
12 1.0
0.08 0.44
0.01 0.073
0.20 0.26
4.1 1.5
3.1 1.3
0.570.094
0.140.057
0.2000.040
Cr
ug/L
0.12
ND
0.15
0.20
0.17
0.13
0.10
0.10
0.12
0.12
0.18
0.10
0.13
0.40
0.12
Cu
ug/L
0.89
ND
0.64
0.61
0.69
0.62
1.4
1.5
1.8
0.94
1.2
0.83
1.4
2.1
1.8
Fe
ug/L
41
ND
21
30
30
21
6.0
43
22
36
18
10
10
17
14
Mn
ug/L
2.2
ND
6.5
10
7.0
5.5
3.0
2.1
2.4
4.5
1.8
1.9
1.6
3.1
2.2
Ni
ug/L
0.90
ND
0.70
0.70
1.2
1.0
1.7
0.51
1.4
0.74
1.3
0.61
1.0
1.8
1.2
Pb
ug/L
0.02
ND
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
0.02
<0.01
<0.01
<0.01
<0.01
Se
ug/L
0.099
0.067
0.088
0.080
0.077
0.076
0.10
0.082
0.074
0.067
0.11
0.047
0.12
0.15
0.15
Zn
ug/L
3.6
ND
0.47
0.70
1.1
0.80
1.6
1.2
2.1
0.68
0.37
0.47
0.46
1.5
2.7
Particulate Concentrations
Cr
ug/L
6.8
4.9
3.9
2.5
1.8
6.7
4.0
1.5
3.3
1300
340
130
1.0
0.8
5.9
47
20
6.5
4.1
0.10
Cu
ug/L
7.7
4.3
3.3
3.3
1.3
10.8
2.2
1.1
2.6
490
150
53
0.4
0.3
2.4
42
21
3.9
1.6
1.0
Fe
ug/L
1260
2560
3500
470
600
35900
1220
780
2140
28200
15700
4870
870
1360
3470
2560
1320
7220
390
6.9
Mn
ug/L
800
890
24
2260
240
3090
72
140
30
6000
780
38
30
45
131
59
95
70
55
4.4
Ni
ug/L
1.3
0.7
5.5
0.2
1.1
3.4
3.2
2.2
3.7
670
210
76
1.1
0.2
2.2
68
25
3.8
3.5
0.70
Pb
ug/L
4.4
3.0
2.4
1.7
0.71
5.3
1.4
0.44
1.2
380
160
34
0.14
0.09
1.3
15
20
1.4
2.1
0.60
Se
up/L
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
Zn
ug/L
27
25
19
18
4.6
40
9.3
5.2
12
3920
1730
570
2.9
1.8
12
220
150
25
26
4.0
ND = Not Determined
68
-------
Table A-3 Primary mercury concentrations (ng/l) for dissolved, participate and
total fractions at the Potomac River fall line.
Date
12/10/96
1/15/97
2/11/97
2/25/97
4/15/97
4/25/97
5/7/97
5/20/97
6/11/97
6/25/97
7/28/97
Dissolved
0.97
0.22
1.95
4.85
0.71
0.61
1.72
0.83
0.80
1.39
5.95
Participate
2.22
0.53
1.11
3.78
2.01
1.64
0.89
1.60
4.20
3.34
30.73
Total
3.19
0.75
3.05
8.63
2.72
2.25
2.61
2.43
5.00
4.73
36.70
69
-------
Table A-4 Primary metal concentrations for (a) dissolved and (b) participate fractions
at Rock Creek.
(a) Dissolved Metal Concentrations
Date
Al
Cd
ug/L ug/L
12/10/96
1/15/97
2/11/97
2/25/97
4/15/97
4/25/97
5/7/97
6/11/97
6/25/97
7/28/97
8/14/97
58
4.5
25
22
7.2
6.9
3.3
12
9
4.9
3.6
(b) Paniculate
0.024
0.032
0.062
0.066
0.729
0.15
0.078
0.026
0.032
0.022
0.029
Cr
ug/L
0.25
0.14
0.24
0.16
0.13
0.23
0.09
0.14
0.4
0.21
0.17
Cu
ug/L
1.7
0.85
1.3
1.1
1.6
2.4
1.4
1.1
1.8
2.3
2.8
Fc
ug/L
140
110
160
190
100
110
120
100
110
46
32
Mn
ug/L
47
140
95
80
42
27
25
51
46
54
48
Ni
ug/L
3.4
1.9
2.5
1.7
1.4
1.2
1.4
1.5
1.2
1.5
1.2
Pb
ug/L
<0.01
<0.01
<0.01
<0.01
<0.01
0.09
<0.01
<0.01
<0.01
<0.01
<0.01
Zn
ug/L
3.9
2.5
3.9
1.1
0.61
1.3
0.6
0.7
0.66
1.1
1.2
Concentrations
Particulate Metal Concentrations
Date
12/10/96
01/15/97
02/11/97
02/25/97
04/15/97
04/25/97
05/07/97
06/11/97
06/25/97
07/28/97
08/14/97
Al
ug/L
56
3.4
1.5
5.7
7.1
38
140
0.90
1.5
0.40
0.60
Cd
ug/L
0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
<0.01
Cr
ug/L
0.54
0.02
0.01
<0.01
0.01
0.01
0.04
<0.01
0.01
<0.01
<0.01
Cu
ug/L
0.69
<0.01
0.01
<0.01
0.01
0.01
0.02
<0.01
<0.01
<0.01
<0.01
Fe
ug/L
38
2.7
1.1
4.1
6.5
31
102
0.60
2.0
0.30
0.50
Mn
ug/L
11
0.55
0.15
0.12
0.67
0.44
3.8
0.04
0.12
0.05
0.16
Ni
ug/L
0.16
0.11
0.01
<0.01
0.01
0.01
0.01
<0.01
<0.01
<0.01
<0.01
Pb
ug/L
0.30
0.01
<0.01
<0.01
<0.01
<0.01
0.01
<0.01
<0.01
<0.01
<0.01
Zn
ug/L
2.5
0.06
0.03
0.02
0.02
0.03
0.11
0.01
0.01
<0.01
<0.01
70
-------
Table A-5 Primary metal concentrations for (a) dissolved and (b) participate
fractions during transect at the Potomac Estuary.
A. Dissolved Concentrations
Date
02/25/97
02/25/97
02/25/97
02/25/97
02/25/97
07/28/97
07/28/97
07/28/97
07/28/97
Location
Piney Pt
Quantico
Alexandria
Natn'l Airpt
Anacostia
Piney Pt
Quantico
Alexandria
Natn'l Airpt
Station ID
stn1
stn 2
stn3
stn 4
stn 5
stnl
stn 2
stn 3
stn 4
Al
(ug/L)
N/A
22
32
26
29
N/A
4.6
7.1
5.6
As Cd
(ug/LJug/L)
N/A 0.07
N/A 0.04
N/A 0.02
N/A 0.03
N/A 0.05
N/A N/A
0.22 0.06
0.28 0.02
0.29 0.03
Cr
(ug/L)
0.5
0.1
0.2
0.1
0.2
N/A
0.1
0.1
0.1
Cu
(ug/L)
0.64
0.33
0.60
0.62
0.64
N/A
1.8
1.5
1.1
Fe
(ug/L)
34
35
32
33
32
N/A •-
9.3
8.7
7.4
Mn
(ug/L)
1.0
1.6
15
9.2
6.9
WA
1.5
0.8
0.4
Ni
(ug/L)
2
0.8
0.8
1
1
N/A
2
2
0.8
Pb
(ug/L)
1>
1>
1>
1>
1>
N/A
1>
1>
1>
Zn
(ug/L)
0.46
0.79
0.56
0.49
0.54
N/A
0.45
1.1
0.52
B. Participate Concentrations
Date
02/25/97
02/25/97
02/25/97
02/25/97
02/25/97
07/28/97
07/28/97
07/28/97
07/28/97
09/09/95
09/09/95
09/09/95
09/09/95
05-Oct-95
05-Oct-95
Location
Piney Pt
Quantico
Alexandria
Natn'l Airpt
Anacostia
Piney Pt
Quantico
Alexandria
Natn'l Airpt
Dissolved
Natn'l Airport
Georgetown
3 -Sisters
Palisades
Paniculate
piney pt
quantico
Station ID
stnl
stn 2
stn 3
stn 4
stn 5
stnl
stn 2
stn 3
stn 4
stn 4
stn 5
stn 6
stn 7
stnl
stn 2
Al
(ug/L)
880
170
11
83
1200
N/A
52
40
50
14.36
80.76
83.67
83.1
133
244
As Cd
(ug/LIug/L)
0.0440.01
0.021 0.01
0.0110.002
0.0090.001
0.11 0.05
N/A N/A
0.10 0.01
0.0360.002
0.0240.003
0.127
0.119
0.082
0.091
0.2190.371
0.0050.115
Cr
(ug/L)
0.48
0.22
0.12
0.11
0.75
N/A
0.96
0.22
0.11
0.53
0.29
4.4
1
Cu
(ug/L)
0.27
0.12
0.076
0.044
0.78
N/A
0.81
0.18
0.11
1.78
1.68
1.55
1.67
2.3
0.45
Fe
(ug/L)
540
350
24
52
730
N/A
96
56
70
4.66
8.13
8.39
9.84
200
166
Mn
(ug/L)
37
0.04
1.3
1.8
51
N/A
4.2
3.2
4.0
5.968
0.925
1.107
1.436
1.89
5.73
Ni
(ug/L)
0.31
0.15
0.09
0.08
0.52
N/A
0.45
0.12
0.07
0.9
0.97
0.78
0.71
2.02
0.54
Pb
(ug/L)
0.26
0.10
0.05
0.03
0.75
N/A
0.47
0.10
0.08
0
0
0
0
1.56
0.003
Zn
(ug/L)
1.7
0.62
0.36
0.29
5.9
N/A
4.9
1.4
0.85
1.19
0.56
1.14
0.43
25.8
0.21
71
-------
Environmental Protection Agency
Chesapeake Bay Program
410 Severn Ave. Suite 109
Annapolis MD 21403
------- |