Umted. States
ETwTfonmental Protection
Agency
Research and Development
.ital Research
Laboratory ,
GaiV Breeze.,Ft 32661
.Middle Atlantic Region 3
6th and Walnut Sts
Philadelphia PA 19106
Chesapeake Bay Program
Nutrient Work Paper
A NUTRIENT BALANCE OF THE CHESAPEAKE BAY:
WITH APPLICATIONS TO MONITORING OF NUTRIENTS
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Nutrient Work Paper #1
A NUTRIENT BALANCE OF THE CHESAPEAKE BAY:
WITH APPLICATIONS TO MONITORING OF NUTRIENTS
by
Gerard F. Laniak
University of North Carolina
School of Public Health
Department of Environmental Sciences and Engineering
U.S. ENVIRONMENTAL PROTECTION AGENCY
CHESAPEAKE BAY PROGRAM
MIDDLE ATLANTIC REGION 3
6TH AND WALNUT STREETS
PHILADELPHIA, PA 19106
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DISCLAIMER
This report has been reviewed by the Office of Research and Develop-
ment, U.S. Environmental Protection Agency, and approved for publication.
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 recommenda-
tion for use.
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CONTENTS
TABLES iv
FIGURES v
Introduction 1
The Study Area 2
Data Base 5
Procedure for Nutrient Budget 7
External Loadings and Outputs 8
Summary of Longitudinal Concentration Distributions 9
Seasonal Instream Molar Ratios 17
Monthly Mass-Loading-Net Sink Curves 17
Molar Ratios 24
Ramifications for Nutrient Monitoring 26
Summary 30
REFERENCES . 31
iii
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TABLES
Number Page
1 Statistical Summary of Chesapeake Bay Segments 3
2 Yearly TN/TP Loadings to Chesapeake Bay .10
iv
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FIGURES
Number Page
1 Chesapeake Bay Study Area 4
2 Longitudinal Concentration Distributions: Winter 11
3 Longitudinal Concentration Distributions: Spring 12
4 Longitudinal Concentration Distributions: Summer 13
5 Longitudinal Concentration Distributions: Fall 14
6 Seasonal Molar Ratios (RN/RP) Along Chesapeake Bay ...... 17
7 Monthly Measures of Nutrient Budget Components—Nitrogen . . 18
8 Monthly Measures of Nutrient Budget Components—Nitrogen . . 19
9 Monthly Measures of Nutrient Budget Components—Phosphorus . 20
10 Monthly Measures of Nutrient Budget Components—Phosphorus . 21
11 Monthly Molar Ratios of Nutrient Budget Components 25
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INTRODUCTION
The study of nutrients in the Chesapeake Bay is of growing concern.
Algal blooms, resulting primarily from increased nitrogen and phosphorus
loadings, are appearing with greater frequency and abundance in the Upper Bay.
These blooms can cause many undesirable effects such as producing anoxic
conditions in the bottom wastes after decay and settling take place. There
are many necessary analyses to be performed before the efficient management of
nutrients is possible.
The first step in resolving this problem is to gain a knowledge of the
sources and the major transport mechanisms associated with nutrients within
the system. A general mass balance approach, that is, one which assimilates
"first cut" data, illustrates the essential features of the nutrients and
their movement in the Bay. A mass balance shows the relationship between
inputs and outputs. As such, the sensitive areas of the Bay, those which
would show most immediate and desirable results from control, can be
determined.
The scale, or the combination-of study area size and time increment, is
important in performing a mass balance. This study considers a nutrient
budget (i.e., mass balance) for the entire Chesapeake Bay area on a monthly
basis. Of course, finer detail would yield more information, but because of
*
the character of available data this is not presently possible. Indeed, it is
the purpose of this "first cut" approach to yield information necessary to
future nutrient monitoring efforts. Data resulting from these monitoring
efforts will provide for the refinement of scale in mass balance studies and
the ultimate management of nutrients in the Chesapeake Bay.
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The primary objectives of this study are:
1) To develop a nutrient budget for the Chesapeake Bay. This budget
is to include total nitrogen, reactive nitrogen, total phosphorus,
and reactive phosphorus..
2) To assess the temporal and spatial variations of nutrients in the
Chesapeake Bay.
3) ... To make recommendations for future monitoring of nutrients in the
Bay.
The study consists of the following tasks:
1) Review the literature to obtain pertinent existing data.
2) Using these data estimate both nutrient loadings to and outputs
from the Bay. This analysis considers a mass balance of nutrients
with respect to the water column.
3) Examine data on Bay quality to establish cause and effect rela-
tionships.
4) Assimilate results from above tasks and make recommendations
concerning future monitoring of the Chesapeake Bay.
THE STUDY AREA
The study area includes the main body of the Chesapeake Bay from its
mouth at the Virginia Capes to the Susquehanna River. Also included are the
tidal segments of all connecting tributaries, the most notable being tne Sus-
quehanna, Patuxent, Potomac, Rappahannock, York, and the James Rivers.
To facilitate analysis, the study area was sectioned into seven seg-
ments as shown in Figure 1. Sections are assumed to be uniform with respect
to water quality. Pertinent physical characteristics of the segments are
listed in Table'1. The study area is approximately 250 kilometers long with
2
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TABLE 1. STATISTICAL SUMMARY OF CHESAPEAKE" BAY SEGMENTS
SECTION LENGTH
(N. Mi.)
1 26
2 20
3 20
4 . 25
5 25
6 30
7 10
VOLUME
(106 M3)
3100
5800
7300
9300
24200
17800
6400
SURFACE AREA
(106 M2)
900
900
1000
1100
3800
2500
1200
AVERAGE DEPTH
(M)
3.4
6.4
7.3
8.5
6.4
7.1
5.3
TOTAL
156
73900
11400
6.5
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CW- SUSOUEHANA RIVER AT
CONOWINCO, MARYLAND
JR - JAMES RIVER AT RICHMOND,
VIRGINIA
GF - POTOMAC RIVER AT GREAT
FAILS, MARYLAND
fj - PUTUXENT RIVER AT OOUTE JO
(JOHN HANSON HlGHY.'AY)
MB - MATTAPONI RIVER AT
IEUIAHVIUE, VIRGIN!A
PH - PAMUNKET RIVER AT
HANOVER, VIRGINIA
'RF- RAPPAHANNOCK RIVER AT
FREOERICKSBUKG, VIRGINIA
kCH-CHICAHOMINY RIVER AT
^PROVIDENCE FORGE, VIRGINIA
cw
SUSOUEHANNA
RIVER
\WASHINGTON
o.c.
°-\<
3CAL1I IN WILES
*-b~
Figure 1, Chesapeake Bay Study Area
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an overall volume of nearly 74xl(P cubic meters, a surface area of
11.4x10^ square meters, and has an average depth of 6.5 meters.
In addition to the segmentation, a computer program was constructed
to manipulate all raw data into a form suitable for the analysis of both
individual sections and the entire Bay with respect to time.
DATA BASE
A literature search was conducted to locate a period of time in which
the four major types of nutrient data: tributary loadings, instream concen-
trations, point source loadings, and air loadings were simultaneously
collected.
Within the period 1969 to 1971 two extensive monitoring programs were
conducted. The EPA (3) monitored fresh water inflows from major tributaries
for flow and the following species: total phosphorus, inorganic phosphorus,
TKN, N02+NC-3, ammonia, and total organic carbon. This study consisted of
several samples per tributary per month extending from June 1969 to August
1970.
Concurrently, the Chesapeake Bay Institute (CBI) (2) carried out monthly
sampling at seven stations along the length of the Bay. CBI reported the
following concentration data at various depths for each station: N02» N03,
ammonium, ortho-phosphate, dissolved organic phosphorus, particulate phos-
phorus, inorganic carbon, dissolved organic carbon, and various chlorophyll-a
pigments. This study extended from April 1969 to June 1971.
EPA tributary sampling stations as well as CBI instream stations are
shown on Figure 1.
Point source loadings are represented by data collected in 1974 (6) and
later by EPA. These loadings include all municipal and industrial discharges
5
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occurring within the study area.
Air loadings are based upon a study of the Rhode River Watershed (7)
performed from 1974 through 1976. In this study seasonal loadings of reactive
nitrogen and reactive phosphorus were determined on the basis of continuous
monitoring of selected sites.
On the basis of these data the time frame of this analysis is from June
1969 to August 1970. The following assumptions are made concerning the
various data:
1) Point source loadings and air loadings, although obtained at later
dates, are assumed to apply directly to the study period.
2) Point source data do not vary with time.
3) Air loadings vary by season only.
4) Monthly values for loadings and concentrations represent an average
of all data reported for a particular month.
a. With respect to tributary data as many as fifteen and as
few as two samples were reported per month.
b. In the case of instream concentrations reported by CBI
samples at various depths were averaged and applied
uniformly to the entire section. One such average is
computed per month per station.
5) Point source loading and air loading data are reported as total
nitrogen and total phosphorus. It is assumed that total nitrogen
equals reactive nitrogen and total phosphorus equals reactive
phosphorus for these data.
6) Instream concentrations of total nitrogen are not reported by CBI
due to sample analysis difficulties. To compute this quantity the
following procedure was used.
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An independent study (9) of the Upper Chesapeake Bay does report
total nitrogen at eleven stations periodically between 1969 and
1971. All results were plotted against concurrent reactive
nitrogen data. A regression analysis was run and the resulting
linear relationship applied to CBI data throughout the study area.
PROCEDURE. FOR NUTRIENT BUDGET
The nutrient budget represents a mass balance performed on each segment
with respect to time. In words, the mass balance expression in section i is
as follows: ACCUMULATION - NET INPUTS-t - NET SINl^
The accumulation term is computed as the difference between the mass of the
quality constituent within the water column at t+At and t (i.e., accumulation
* Mt+ t - M^, where M represents the product of section volume and average
section concentration, t represents time and At represents a time increment of
one month.). Net inputs is the difference between the sum of all external
loadings (i.e., tributaries, point sources, air loadings, and transport in by
advection and dispersion) and outputs (i.e., advection and disperson out of a
section). The net sink term represents that mass which is removed from the
water column by internal mechanisms such as decay, biological uptake, or
sedimentation.
In terms of the mass balance expression data is available for both the
accumulation and net input terms. No such data is available to describe the
net sink term. For purposes of this analysis the mass balance is performed to
determine the magnitude and significance of the net sink term.
The results of this study are discussed in the following order:
1) Annual external loadings of nutrients to and outputs from the
study area.
7
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2) System response to these loadings. This is shown as average
seasonal concentration plots of nutrients along the length of
the Bay.
3) Average seasonal molar ratios (reactive nitrogen/reactive
phosphorus and total nitrogen/total phosphorus) of instream
concentrations.
... 4) Monthly plots of total system mass, loadings, and net sink
terms. This is a direct result of the budget and includes
total and reactive nitrogen and total and reactive
phosphorus.
5) Monthly molar ratios of mass balance components (i.e., water
column masses, loadings, and the net sink term).
EXTERNAL LOADINGS AND OUTPUTS
Table 2 shows annual total nitrogen and total phosphorus loadings to the
Chesapeake Bay by section. The following observations concerning this data
are made:
1. Air loadings of nitrogen and phosphorus are generally in the order
of 5% of the total and therefore insignificant.
2. Of the total nitrogen loadings 70% enters via tributaries and 25%
via point source discharges.
3. Total phosphorus loading figures are: 65% from point sources and
approximately 30% from tributaries.
4. There are three significant regions of the study area through which
nutrients enter. Section 1, which includes the Susquehanna River
and Baltimore Harbor, receives 55% and 35% of the total nitrogen
and total phosphorus loadings, respectively. Section 5, which
8
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includes the Potomac River, receives 25% and 35% of the nitrogen
and phosphorus loadings, respectively. Section 7, which includes
the James River, receives 10% of the nitrogen loading and 20% of
the phosphorus loading. In all, these sections receive
approximately 90% of both the total nitrogen and total phosphorus
loadings.
5. Total annual loadings to the Chesapeake Bay are 1212 x 10^ kg/yr
total nitrogen and 164 x 10-* kg/yr total phosphorus. Outputs, via
advection and dispersion to the ocean are 390 x 10^ kg/yr total
nitrogen and 2 x 10^ kg/yr total phosphorus. This shows that 70%
of the total nitrogen and essentially all of the total phosphorus
(99%) loadings remain in the Bay.
SUMMARY OF LONGITUDINAL CONCENTRATION DISTRIBUTIONS (FIGURES 2 THROUGH 5)
1. Reactive nitrogen concentrations vary widely both with respect to
season and location.
0 In all seasons the highest concentrations are located in the
upper Bay near Baltimore Harbor. Concentrations are highest
here during the winter and spring, 1.0 mg/1 as N and 0.65mg/l
as N, respectively.
0 During the summer reactive nitrogen in the headwaters is 0.2
mg/1 as N. This decrease is believed primarily due to lower
river flows and is reflected in the general loading curves
(Figure ).
0 While during winter and spring reactive nitrogen decreases
significantly along the entire length of the Bay, the summer
concentrations reduce from 0.2 mg/1 as N in the upper Bay to
9
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TABLE 2. YEARLY TN/TP LOADINGS TO CHESAPEAKE BAY
SECTION
1
2
3
4
5
6
7
POINT SOURCES
TN TP
(105 KG/HR)
126 32.3
3.7 .3
0 0
12.1 3.8
97.9 40.7
3*6 1.3
79.3 26.8
TRIBUTARIES
TN TP
(105 KG/YR)
523
0
0
9,9
214
27.7
61. .4
23.5
0
0
2.8
17.2
2.2
4.1
AIR
TN TP
(105 KG/YR)
4.1
4.2
4.7
5.3
17.8
11.6
5.7
.70
.7
.8
.9
3.1
2.0
1.0
TOTAL
322.6
105.2
836
49.8
53.4
9.3
10
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approximately Oi04 mg/1 as N at mid-Bay and remain
essentially constant with a low point of 0.03 mb/1 as N at
the ocean interface. •
2. Reactive phosphorus concentrations during all seasons lie between
0.01 mg/1 as P and 0.02 mg/1 as P. Typically, upper and lower Bay
experience slightly higher concentrations than does the middle
" region. This tendency is altered during the summer where
concentrations fall from 0.02 mg/1 as P in the upper Bay to 0.015
mg/1 as P in the middle region and then remain constant.
3. The spatial variation in total phosphorus is not significant.
Summer concentrations are highest and average 0.05 mg/1 as P
throughout the Bay. During the remainder of the year concentra-
tions generally vary between 0.03 mg/1 as P and 0.04 mg/1 as P.
4. Particulate phosphorus in the upper Bay varies between 0.01 mg/1
as P and 0.02 mg/1 as P during winter-fall and summer-spring
respectively. Spatial variation is most significant during the
summer where a low of 0.007 mg/1 as P is seen just above the
Fatuxent River and a high of 0.02 mg/1 as F is seen in both the
upper and lower Bay.
5. In all seasons but summer chlorophyll-a is lowest in the upper Bay,
rises in the middle region, and remains essentially constant to
the ocean. This range is from 0.003 mg/1 to 0.01 mg/1. During the
summer, however, concentrations are greater than 0.015 mg/1, more
than double other seasons, in the upper Bay. This is followed by
a steady decrease toward the lower Bay to a value less than 0.003
mg/l«
15
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SEASONAL INSTREAM MOLAR RATIOS (FIGURE 6)
1. RN/RP ratios are generally highest in the upper Bay, and
steadily decrease downstream.
2. Spring and winter show ratios greater than 100 in the upper end.
These values decrease to approximately 50-75 in the middle regions
and further decrease to a low of 10 at the extreme lower boundary.
3. ., During the summer, molar ratios in the upper end range between 15
and 20. These ratios are near those measured in algae and there-
fore suggest that either nitrogen or phosphorus could be limiting
algal growth.
4. Middle and lower Bay values for the summer are well below 15 which
suggests that nitrogen only would limit algal growth.
MONTHLY MASS-LOADING-NET SINK CURVES (FIGURES 7 through 10)
Loadings
1. Nutrient loadings in general are highest during winter and spring.
Because point source discharages are essentially constant and air
loadings are insignificant, the variation of loadings is a function
of tributary flow.
2. During the summer and fall, the reactive phosphorus loading remains
essentially constant at 10° kg/mo. Loadings are then increased by
an average factor of 1.3 during the winter. The winter loadings,
and thus flows, show more variation than do summer loadings.
3. Total phosphorus loadings are similar to reactive phosphorus except
the winter increase factor is approximately 1.6. This shows an
increased organic fraction.
4. Nitrogen loadings show identical temporal characteristics as do
16
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the phosphorus loadings. During the summer, reactive nitrogen
loadings are approximately 5x10^ kg/mo and constant. Total
nitrogen is slightly higher.
5» During the winter both total and reactive nitrogen increase by a
factor of approximately 2.4. The increased organic fraction, as
seen in the phosphorus loadings, is not evident with nitrogen.
Water Column Mass
If total mass is divided by a loading rate, the result represents
an average retention time.
1. The total mass of reactive phosphorus in the Bay fluctuates little
during the year. The average value is approximtely 10° kg.
Coupled with the average reactive phosphorus loadings, it is
concluded that there is a residence time of one month during the
summer and slightly less than a month in the winter for reactive
phosphorus in the water column.
2. Total phosphorus undergoes large seasonal variation. Average
summer values of water column mass lie between 3.0x10" and A.Ox
kg. Winter values are noticeably lower and range from 2. Ox
kg and 2.5x10^ kg. Residence times for total phosphorus
appears to be three months during the summer and fall and as little
as one month during the winter and spring.
3. 'Because water column concentrations of total nitrogen is a direct
function of reactive nitrogen temporal variations are identical.
Nitrogen masses, unlike phosphorus, increase dramatically during
the winter. This is because the major portion of the total
nitrogen loading enters via tributaries.
22
-------
4. Residence times for reactive nitrogen are approximately one month
during the summer. This is identical to reactive phosphorus and
approximately two months during the winter, compared to less than a
month for reactive phosphorus. Tentative explanations for these
results are:
a. The removal of both reactive species during the summer is
by the same mechanism, possibly algal consumption.
b. Removal of the reactive species during the winter is by a
different mechanism which does not seem common to both
reactive nitrogen and reactive phosphorus.
5. Total nitrogen residence times appear highest, more than four
months, during the summer and decrease to approximately three
months during winter and spring.
6. It should be noted that these residence times are related to the
water column only and therefore do not represent flushing times
from the Bay. Indeed, the greatest portion of the nutrients seem
to be accumulated within the Bay region.
Net Sink
1. "Net sink" is a terra for describing all the processes by which
constituents leave the water column. This removal can be via
/
sedimentation, biological uptake, etc. For purposes of discussion
this will be referred to as losses or removal.
2. Total phosphorus losses undergo large fluctuations throughout the
year. Summer and fall see as much as 10" kg/mo and as little as
zero kg/mo removed. Winter and spring values are higher with
average removal of approximately 20x10^ kg/mo. This high winter
23
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loss coincides with the dramatic reduction of total phosphorus
in the water column.
3. Reactive phosphorus also disappears at a higher rate during the
winter. The increased removal during winter months may be due
to increased sediment loading associated with high flows and
resulting in adsorption of nutrients to suspended sediments and
subsequent settling.
4. The decreased removal rate during the summer months may simply
reflect a lessening sediment load accompanied by a relatively
low algal uptake rate.
5. The removal of both total and reactive nitrogen is temporally
similar. Highest removal, approximately 20x10" kg/mo, occurs
during the spring. For the remainder of the year both total
and reactive nitrogen losses vary between zero and 8x10"
kg/mo.
6. As was reported earlier, relatively small amounts of nitrogen
and especially phosphorus are flushed into the ocean. This
suggests that the inverse correlation betweeen water column
mass and removal mass should be strong. From the curves shown
this is true.
MOLAR RATIOS (FIGURE 11)
1. .RN/RP is essentially the same for the water column and loadings
during the summer and early fall and measure approximtely 10. This
would seem to say that, on the whole, the Chesapeake Bay may be
nitrogen limiting during the .summer. However, as was seen earlier,
the upper Bay experiences higher molar ratios than the remainder of
24
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100
WATER
COLUMN-*-/
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60
Q.
WATER COLUMN-/
r &
\ — — — 10
10
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12
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2
4
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. 6 fc
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Figure 11. Monthly Molar Ratios of Nutrient Budget Components
25
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the Bay.
2. During the winter months the RN/RP ratio increases to as much as 80
in the water column while an increase to approximtely 20 is seen in
the loadings. The sharp increases in water column ratios is
suggested by the longer residence time of nitrogen during the winter
coupled with the relatively shorter holding time for phosphrous.
3. Total nitrogen/total phosphorus for loadings is similar to RN/RP
in all respects.
4. TN/TP in the water column is approximately 35 during the summer and
reaches a peak of 60 during the spring. Again, this variation is
suggested by increased total nitrogen and decreased total phosphorus
in the water column during the winter.
5. The RN/RP ratios for the net sink term lies between 15 and 30 during
the late spring and summer and is widely variant during winter and
early spring. This may describe the major removal mechanisms as
being adsorption to suspended sediments during the high flow months
and algal uptake during the summer. The widely variant nature of
the winter RN/RP ratios suggests multiconditional removal
mechanisms.
RAMIFICATIONS FOR NUTRIENT MONITORING
When considering a monitoring program the two primary decisions are where
to sample and how often are samples to be taken. Some of the major factors
affecting these decisions are as follows:
26
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Location of Sampling Stations
1. Point source, upstream and downstream
2. Segments with high variability of water quality parameters
3. Critical points with respect to a parameter
4. Substantial flow changes
5. Changes in regional classification
6. Freshwater limits of estuaries
7. Interstate borders
8. Location of sensitive receptors
9. Areas of environmental concern
10. Areas of potential development
11. Areas susceptible to storm flows
12. Locations that can provide baseline information.
Frequency of Sampling
1. The response time of the system
2. Expected variability of the parameter
3. Half-life and response time of constituents
4. Seasonal fluctuations and random effects
5. Representiveness under different conditions of flow
6. Short term pollution events
7. The magnitude of response
8. Variability of the inputs
Of these many factors this report concentrates on only the variability of
nutrient conditions with respect to space and time within the Chesapeake Bay
region. With the background provided by the data the following observations
and recommendations are made:
27
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1. Air loadings are shown to be an insignificant factor in determining
nutrient loadings to the Chesapeake Bay. However, this conclusion
reflects a uniform extrapolation of conditions representative of a
single watershed located within the Bay region. Because of possible
heightened local effects, it is felt that air loadings should be
studied for additional regions of the study area.
2. Nutrient loadings to the Bay vary significantly during winter and
spring months and remain relatively constant during summer and fall.
This is due to the temporal variations associated with freshwater
flows entering the Bay. Because of these facts, monitoring efforts -
aimed at determining nutrient loadings need not be as temporally
extensive during low flow months.
3. Spatially, these loadings enter the Bay region primarily at three
locations: the upper Bay from the Susquehanna River and Baltimore
Harbor, the mid-Bay region from the Potomac River, and the lower
Bay from the James River. All other contributions total
approximatley 10%. This fact suggests that conclusions concerning
Bay-wide loadings may be made on the basis of data from these three
regions.
4. Flushing of nutrients from the Bay shows only fractional overall
removal, approximately 30% and 1% annually for total nitrogen and
total phosphorus, respectively. These numbers are dependent upon
.limited concentrations data at the Bay-ocean interface area.
Further monitoring of this area is necessary to verify results.
5. Of the water quality constituents studied, only nitrogen and
particulate phosphorus show significant spatial variation in waste
column concentrations. Only nitrogen shows significant seasonal
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variation throughout the Bay. These tendencies suggest that not all
constituents need be monitored on the same basis. Interparameter
correlations would also help in determining constituent preference
in monitoring.
6. Chlorophyll-a concentrations vary seasonal only in the upper Bay
regions where algal growths are most common. Continued monitoring
_of this parameter is particularly important in this region.
7. Nutrient molar ratios are helpful in determining the potential for
algal growth. Based on the analysis instream molar ratios, it is
concluded that nitrogen limits algal growth in the middle and lower
regions of the Bay. In the upper regions of the Bay reactive
nitrogen to reactive phosphorus ratios fluctuate about a mean
representative of ratios found in the biomass. This suggests that
»
either nitrogen or phosphorus-t:ould limit algal growth depending
upon local conditions. These comments are directed to the low flow
summer months only.
8. Perhaps the most important monitoring consideration is the further
definition and quantification of nutrient removal mechanisms. As is
reported, the ma jority .of the nitrogen and phosphorus loadings to
the Bay are not flushed to the ocean, rather they are removed from
the water column by various internal mechanisms. On the basis of
this analysis the removal mechanisms are varied with respect to both
season and the particular nutrient. It is postulated that the major
mechanisms are adsorption to suspended sediments during the high
flow months and uptake by the algal cells during the low flow summer
months.
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SUMMARY
Using the approach of elementary raw data manipulation, a nutrient budget
for the Chesapeake Bay is performed. Results of this budget analysis show
that major portions of the nitrogen and phosphorus loadings to the Bay are
removed from the water column internally; that is, they are not discharged to
the ocean. Further, removal mechanisms seem to vary from season to season and
among the various nutrient species. On the basis of this analysis it is
necessary to construct appropriate monitoring programs to enable a more
complete understanding of these mechanisms.
Coupled with this budget analysis the data from tributary loadings, air
loadings, point source loadings, and instrearn concentrations of nutrients, are
studied with respect to spatial and temporal variation within the Chesapeake
Bay. Results are then utilized in forwarding recommendations concerning the
future monitoring of nutrient conditions iri the Chesapeake Bay region.
Obviously, the appropriate management of Chesapeake Bay resources depends
heavily upon the effectiveness of data collected through monitoring.
Monitoring, while its main product is data, is also constrained in efficiency
by previously collected data. It is therefore necessary to apply exhaustive
measures to the analysis of all previously collected data to discern its
usefulness as a component in future decision-making processes.
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REFERENCES
I. Chesapeake Bay Institute, The Johns Hopkins University, Special Report
20, "Volumetric, Areal, and Tidal Statistics of the Chesapeake Bay
Estuary and its Tributaries," Cronin, W. B., March 1971.
2. Chesapeake Bay Institute, The Johns Hopkins University, Special Report
"61, "Plankton Ecology Project: Nutrient and Chlorophyll Data: Aesop
Cruises: April 1969 to April 1971," Taylor, W. R., August 1977.
3. Guide, V. and 0. Villa, "Chesapeake Bay Nutrient Input Study," Technical
Report No. 47, EPA-Annapqlis, September 1971.
4. Clark, L. J., V. Guide and T. H. Pheiffer, "Summary and Conclusions:
Nutrient Transport and Accountability in the Lower Susquehanna River
Basin," EPA-Annapolis, October, 1974.
5. Clark, L, J., D. K. Donnelly, and 0. Villa, "Nutrient Enrichment and
Control Requirements in the Upper Chesapeake Bay," EPA-Annapolis,
August 1972.
6. VIMS, Final Report to National Commission on Water Quality, "The Chesa-
peake Bay: A Study of Present and Future Water Quality and its
Ecological Effects," Vol. 1, Kuo, A. Y., A. Rosenbaum, J. P.
Jacobson, and C. S. Fang, June 1975.
7. Chesapeake Bay Center for Environmental Studies, Smithsonian Institution,
"Nutrient Loading of the Rhode River Watershed via Land Use Practice
and Precipitation," Miklas, J., Vol. 1, February, 1977.
8. Hydroscience, Inc., "The Chesapeake Bay Waste Load Allocation Study,"
April 1975.
9. Marks, J. W., and 0. Villa, "Water Quality Survey of the Upper Chesapeake
Bay," EPA-Annapolis, 1971.
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