It',
SSriis, Nitrogen, Secchi Depth, and
pun Chesapeake Bay, 1984 "to 1992
Chesapeake Bay Program
on
Kecycled Paper
-------
Trends in Phosphorus, Nitrogen, Secehi Depth, and
Dissolved Oxygen in Chesapeake Bay, 1984 to 1992
Cooperative Agreement No. TCR0-93-08-01-000
CBP/TRS115/94
August 1994
Printed by the U.S. Environmental Protection Agency for the Chesapeake Bay Program
-------
. ENDORSEMENT
The Chesapeake Baj Monitoring Subcommittee has reviewed the assumptions and
methods of data analysis used in this repent and finds them apprtjpriace for the analysts
conducted.. The findings of ihis report ait consistent with and supported by the analytical
techniques employed. .
Trends in Phosphorus. Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
Trends in Phosphorus. Nitrogen, and Dissolved Oxygen. 1984 to 1992
-------
V-
r ,
ABSTRACT
The Chesapeake Bay Program (CBP) is a Fedcral~Siate partnership working to re-
store Chesapeake Bay. One of its primary goats is to improve wafer qualify and habitat
conditions for living resources. The CBP began monitoring water and habitat quality in
19$4 and continues to sample the main stem and tributaries far their physical and chemi-
cal makeup.
Nutrient enrichment is a major water quality problem in Chesapeake Bay. Nutrients
fiiel phytoplankton growth, which has an adverse (reduction) effect on dissolved oxygen
(DO) levels. Low DO levels threaten the existence of Chesapeake Bay's aquatic animals.
DO levels should increase if nutrient levels are reduced A computer model pre-
dicted that a 40-percent reduction in nitrogen and phosphorus would reduce nutrient
.levels and cause an increase in DO levels in the main stem to Chesapeake Bay. Nitrogen
and phosphorus control programs have been initiated. Trend analyses, involving various
criteria, were performed over an S-year period (from October 1984 through September
1992) to see how these programs affected water and habitat quality conditions in .Chesa-
peake Bay.
Results of seasonal Kendall test analysts indicate that phosphorus levels decreased
significantly baywide, especially in one. upper Chesapeake Bay segment and two tower
Chesapeake Bay segments. There were also marginally significant improvements in phos-
phorus levels in two upper Chesapeake Bay segments and in one tower Chesapeake Bay
segment. Nitrogen levels were somewhat increased (marginally significant) in one seg-
ment of Chesapeake Bay. Secchi depths showed no significant trends baywide; however,
there were marginally significant trends (improvements) in upper Chesapeake Bay. DO
trends were not statistically significant baywide; however, segments at the mouth of Ches-
apeake Bay showed marginally significant degradation.
Trends in Phosphows, Nitrogen, and Dissolved Oxygen, 1984 lo 1992
-------
Trends in Phosphorus, M/ogen. zr* Dissolved Oxygen, 1984 to 1992
•
4
-------
CONTENTS
• • ' . " . . Page
Endorsement , iii
Abstract - , - v
Acknowledgments - • ....,: ix
Abbreviations ;...., , ix
Executive Summary , 1
'Introduction ,......; '..' 5
Methods ...; .../. , 5
Parameters Analyzed and Date Preparation 5
: Trend Analysis Methods 6
Adjustments for Changing Detection Limits ; \:,.-W
Suwjuehanna River Bow i.. - - • • ." JO
Phosphorus . ". ;....,...... r, II
Nitrogen ..;,.. ; 11
Secchi Depth 12
Dissolved Oxygen 12
Results and Discussion .,..,..! , 13
Susquehanna River Row , 13
Phosphorus -, , 16
Tolal Phosphorus 16
Dissolved Inorganic Phosphonis (Onhophosphate) , 17
Nitrogen 26
TotalNitrogen 26
Dissolved Inorganic Nitrogen 27
Secchi Depih .'.... ,. 31
.Dissolved Oxygen 39
Plans for Future Trend Analyses , 46
Interpolating Above and Below Pycnocline Layers and Surface and Bottom
Layers Separately ,., 46
Accounting for Interannua! Changes in Flow 47
Adding Parametric Trend Tests '.. 47
Adding Trend Tests on Interpolated Tributary Data ...,.».. 47
Summary : 47
References 49
Appendix—Frequencies of Below Detection Limit Values for Dissolved
Inorganic Phosphorus and Dissolved Inorganic Nitrogen - 51
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
VII
-------
18
19
22
FIGURES
1. CBP main stem monitoring stations and segments 7
2. Total annual Susquehanna River flow (bars) and number of months above
median flow line (water years 1985 to 1992) 1 14
3. Total phosphorus trends in Chesapeake Bay main stem segments (October 1984
through September 1992). - -
4. Average monthly concentrations of total phosphorus and dissolved inorganic
phosphorus (1984 to 1992). ...,
5, Dissolved inorganic phosphorus trends in Chesapeake Bay main stem segments
(October 1984 through September 1992). '-
6. Average monthly concentrations of dissolved inorganic phosphorus (1984
to 1992) , 23
7. Total nitrogen trends in Chesapeake Bay main stern segments (October 1984
through September 1992). , ,-,-..; 28
8. Average monthly concentrations of total nitrogen and dissolved inorganic
nitrogen (1984 to 1992) A...... 29
9. Dissolved inorganic nitrogen trends in Chesapeake Bay main stem segments
(October 1984 through September 1992). 33
10. Average monthly concentrations of dissolved inorganic nitrogen (1984 to
1992) '...„ 34
11. SecChi depth trends in Chesapeake Bay main stem segments (October 1984
through September 1992). 36
12. Average monthly Secchi depths (1984 to 1992) 37
13. Dissolved oxygen delta and dissolved oxygen deficit trends in Chesapeake
Bay main stem segments (October 1984 through September 1992) 40
14. Average monthly concentrations of dissolved oxygen and dissolved oxygen
deha(1984 to 1992) , 42
15. Total volumes of water with dissolved oxygen concentrations below 0.2, I, 3,
and 5 mc/L (June through September, 1985 to 1992). 44
TABLES
Executive Summary Table. Summary of trend results (October 19S4 through
September 1992) 3
1, Correlations between log mean monthly Susquehanna River flow and mean
monthly concentrations of water quality parameters (with P values in
parentheses) ' H
2. Trend results for interpolated monthly mean total phosphorus by segment
(12 months) ~ 17
3. Trend results for interpolated monthly mean levels of dissolved inorganic
phosphorus by segment, using four different method detection limit
treatments 21
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
4. Trend results for interpolated moniMy mean dissolved inorganic phosphorus
by segment (12 months) • 25
5. Trend results for intwjiolated monthly mean dissolved inorganic phosphorus
by segment (7 months, April through October). .. 26
6. Trend results for interpolated monthly mean totaJ nitrogen by segment 27
T. Trend results for interpolated monthly mean levels of dissolved inorganic
nitrogen by segment using four different method detection limit treatments 32
8. Trend results for interpolated monthly mean Secchi depth by segment
(7 months, April through October) 39
9, Trend results for interpolated monthly mean dissolved oxygen delta by
segment (4 warm weather months, June through September) 41
10, .Trend results for interpolated monthly mean dissolved osy gen deficit by
• segment (4 warm weather months, June through September) -.-;••. 46 .
-11. Summary of trend results (October 1984 through September 1992) 48
A .1. Percent of observations with below detection limit .values for dissolved
inorganic phosphorus by segment, laboratory, and water year..,....." 52
A2. Percent of observations with below detection limit values for dissolved
inorganic nitrogen by segment, laboratory, constituent parameter, and
water year. ., 55
ACKNOWLEDGMENTS
The Mor»H0rhii Subcommittee would especially like to express its gratitude to Peter
Bergstrom and Marcia Olson for writing this report. The Monitoring Subcommittee
would also like to express their gratitude to the field and Jab crews that carefully and ex-
pertly collected and analyzed the water quality samples discussed in the report. A great
many other people provided both information insights and support that contributed to the
preparation of this report, and to all of them our heartfelt thanks.
ABBREVIATIONS
BDL Below detection limit(s)
CBL Chesapeake Biological Laboratory
CBP Chesapeake Bay Program
CRL (The U.S. Environmental Protection Agency's) Central Regional
Laboratory (in Annapolis, Md.)
DIN Dissolved inorganic nitrogen
DIP Dissolved inorganic phosphorus
DO Dissolved oxygen
KD Light attenuation
MDE Maryland Department of the Environment
MDL Meitad dwciion Vimit(s)
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
ODU
P
SAV
TN
TP
VIMS
wy
Old Dominion University
Probability that an observed trend, correlation, or difference was dae to
chance ,
Submerged aquatic vegetation
Total nitrogen
Total phosphorus
Virginia Institute of Marine Science
Water year(s)
Trends in Phosphorus, NHrogen, and Dissolved Oxygen. 1984 to 1992
-------
EXECUTIVE SUMMARY
Bay.
water quality conditions in Chesapeake
^
"
and
Secchi
1992).
and wcre classified as
provemems (/><0.01)
av
-------
based on the mean concentration for the first water year {October 1984 through Septem-
ber 1985) and a projection for the last water year based on .the seasonal Kendall slope.
Interannual chances in Susquehanna River now could produce «he appearance of
trends in water qualkylf there was a trend in How. ind water quality was correlated with
flow; however, there were no significant trends in mean monthly Susquehanna River
How over any time period. In contrast, there were significant positive and negative cor-
relations between the log mean monthly Sttsqoehanna River flow and upper Chesapeake
Bay water quality, but they did not follow a simple pattern.
Tf concentrations showed a statistically significant downward trend (/><0.01) bay-
wide, especially in one upper Chesapeake Bay segment and two tower Chesapeake Bay .
segments. There were also marginally significant improvements (J><0.05) in two upper
Chesapeake Bay segments and in one lower Chesapeake Bay segment. The median bay-
wide percent change (decline) in TP over 8 years (J984to 1992) was 16 percent, plus or
minus 8 percent (90 percent confidence interval). DIP showed significant downward
trends over 12 months at the mouth of Chesapeake Bay and over 7 months (April through
October) in central Chesapeake Bay, but the trend was not significant baywide*. *
TN concentrations showed a marginally significant increasing trend (degradation,
P=0.027) in Mobjack Bay, Including tht mouth of the York River, however, there was no
significant trend baywWe or in ar.v other segments. The possible increase in TN in Mob-
jack Bay was probably related 10 similar upward trerids in TN in the York River. DIN
showed no significant trends in any segments, although high detection limits made it im-
possibleto assess trends in nitrogen concentrations in several lower Chesapeake Bay
segments.
Secchi depths showed no significant trends baywide over a period of 7 or 12 months
or for any segment over 12 months. There were marginally significant upward trends
(improvements) in upper Chesapeake Bay over the 7-month SAV growing season (April
through October). These trends may be related to statistically significant inverse correla-
tions between the April-through-September Seccfii depth and the mean monthly
Susquehanna River How, although there were no significant trends in now. Secchi depth
is not measured in the Susquehanna River, so it is not known whether there were trends
in Secchi depth there.
DO concentration (rends as well as trends in several metrics calculated from the
. concentration were examined. These trends included oxygen delta (the difference be-
tween DO at saturation and the actual DO concentration) and DO deficit (converting the
delta concentration to the mass of DO thai would have to be added to bring all the water
in that segment to saturation). The volumes of water in each segment that were below
four benchmark DO concentrations (5, 3, 1, and 0,2 mg/L) were also analyzed for trends.
DO concentration and the four metrics for volumes below specific concentrations
had no statistically significant trends (P>0.05) in any segments in the June-to-September
period. The mouth of Chesapeake Bay showed marginally significant degradation in both
DO delta and DO deficit. However, DO concentrations are generally high in the mouth of
Chesapeake Bay arid DO delta is quite low, so these trends are unlikely to have any nega-
tive impact on aquatic animals living near the mouth of Chesapeake Bay.
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
...
"aranrjeter
_
?F : —
DIP
DIP
TN
DIN
DIN
SeccW Depth
Seechi Depth"
°O Concentration
DODefta
DO'Defteft .
DO<0,2
DO<1.0
D0<3.0
DO<5.0
Legend and note;
No, of
Months AH' CB1 C£
— ^**
12
.7 _
12 _ _
12 -
7 ~
12 - _ ' - _
7 - IM IM
4 - . --
4 - ' -
4 '_ _ . ' _
4 ' -
4
4 - . _ ' _
4
DM
- DM
- DM -
-, -
^S»iuiSS3? tfend (ft^s)
ingunll | jj fS* .lrt be asses^ in these seg
not analyzed in EE3
because detecdon limits did not stop deciin-
^^^
D0
Trends in Phosphorus. Ni.rogen, and Dissoived Oxygen.
1984 to t992
-------
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen. 1984 to 1992
-------
.V-
INTRODUCTION
Chesapeake Bay Program (CBP) is a Federal-
Bay. One of the main goals of the CBP is to
«apeake Bay Jiving resources. CBP's
grams were started in 1984 to characterize current vi
^ T1'* *"** time* *****"$* ™* 150 stations
analyzed for more than 20 physical and chemic
olxao
or w, a conditwn which Is potentially JeAal to Chesapeake Bay wroatic aiiiinals^rin
«d I summer pbytoplankton blooms, fueled by high aJSm fci3LTI« bTSo 2T*
£3 ^"T whea * pianiciondie «3*U<*. Tn»r^sS; TO£i
snoujd improve if nutrient levels are reduced.
«n .fd ^'^k1* "KXfcI bf C^P"*6 B*y «««r q^iity predicted that 40 percent ni'tm.
S-nt^^^
The 1987 rh^ V? deeper areas of the main stem of Chesapeake Bav
SS^d^'^r^^
of ftf iSf ^ *""*' "^ the ^^^ of Columbia to achieve » 40-percen^doS
«heteS^en^PhOSphOWl^
on ,«, ni
^ W
eb affect submerged aqu ceetario?? ^Ts^ WefC added ^^^ *•* lev-
phyioplankton growth vegeta«o» (SAV) grow.h5 and are also closely related to
METHODS
PARAMETERS ANALYZED AND DATA PREPARATION
is,ry^^^^^
parameters were analyzed^ !SS P™°$ rCP°m ^ followin« water •!•»
* TP concentration
Trends in Phosphorus. Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
« DIP concentration
• TN concentration
* DIN concentration
• Secchi depth
» DO concentration.
Jhc following calculated metrk$ derived from the water quality parameters were
also analyzed in this report:
* DO delta: the difference between DO saturation concentration and observed
DO concentration .
» DO deficit; the difference between DO mass at saturation and the observed
mass of DO
» Volume of water with DO concentrations below 5,3, l,and0.2mg/L.
A three-dimensional interpolator8 was used to estimate baywide main stem mean
concentrations and mean concentrations in each CBP main stem segment (CB,1 to CB8,
EE3, and WE4). (See Figure 1.) Data from all sampling depths were used, except for
Secchi depth, which has only on? measurement per station. The annual periods used were
water years (WY). from October trough September (which include a complete hydro-
logical cycle). The monitoring data from October 1984 through September 1992 were
osed: the previous reports included data through September 1990. The possible outliers
that were removed from nitrogen and phosphorus data in the two previous reports3-4
were checked by the data submitters and were either verified or corrected. The Maryland •
monitoring data used in this report were resubmitted in 1992, incorporating numerous
data corrections; there were also corrections made to .Virginia monitoring data in 1992.
Because the data had been verified or corrected, the analyses in this report used data as
currently stored in the CBP data base without deleting any possible outliers.
Duw were not adjusted for river flow. In the Chesapeake Bay monitoring program,
now is only measured at the fall line stations, and only the Susquehanna River fall line
station at Conowingo, Md. is close enough to the main stem to have a direct impact on
it.7 Trend tests were performed on mean monthly Susquehanna River flow, and correla-
tions between bg mean monthly flow and all parameters were calculated to estimate the
degree of association. However, a simple flow adjustment in the main stem of Chesa-
peake Bay is not possible because it would assume that How has either an immediate
effect on concentrations or an effect after a fixed time lag. The effects of Susquehanna
River How on main stem water quality must be highly variable because "Chesapeake
Bay's response to a freshet is a function of Chesapeake Bay's recent history and cannot
be linearized or easily predicted,"8
TREND ANALYSIS METHODS
Trend analyses of nitrogen, phosphorus, and DO were performed on monthly mean
concentrations, spatially interpolated in three dimensions. Trend analyses of Secchi depth
were performed on monthly mean depths interpolated in two dimensions. Flow data used
were monthly means of daily Susquehanna River Hows measured at Conowingo, Md.
•If
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to
-------
Retetfve Voftl"*« of Main Stern Segments
CBS WE4
CB7
CB6
CB2
MD/VA Line
of threc additional paramctcrs:
(a
els affect submc^ed aq
phytoplankton growth
M3*n werc «*Wbe«« .heir lev-
JSAV) growih' and ar* aiso closely related to
METHODS
WE4
Figure ,. CBP main Stem monitoring s.a.bn,aod segments.
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, t964 to
1992
-------
Nutrient and Secchi monthly means for segment EE3 were estimated without using data
from the Maryland tributary monitoring stations in this segment because the tributary
data were nqt'availabk for'the whole time period. DO data were not estimated for seg-
ment EE3 because it has hisher spatial variability than the other parameters. Some of the
metrics used for DO were slightly different from those used before. Trend analyses were
performed only on interpolator output, not on concentrations observed at individual sta-
tions (except for flow). Trend analyses were performed on DO, which was not done
previously.2 Trend analyses for some parameters were performed on data from either
April through October or June tbrough.September to correspond with the period of maxi-
mum effects on living resources. A nonparametric trend test was substituted for the
parametric test used in the previous analyses.3*4
The trend test used was the seasonal Kendall nonparametric test, which tesis for
monotonic trends. Monotonic trends need not be linear, but they are assumed to have a
slope that is consistently positive or negative.9 Trends that change from positive to nega-*
live slope (or vice versa) may not be detected. The previous nitrogen and phosphorus
reports used linear, quadratic, and cubic parametric regression to assess both monoionic
and nonmonotonic trends.3-4 The seasonal Kendall test was performed with ^custom
SAS program10 using the method described by Gilbert.9
The seasonal Kendall test assumes the successive monthly values are independent
or have no serial correlation. This is not often true of Chesapeake Bay water quality
data3-4; serial correlation tends to inflate the significance of the test.9 There are modifica-
tions to the seasonal Kendall test that account for serial correlation9; however, they
assume that the correlation has a fixed structure, while the actual correlations are quite
variable.3-4 Thus, the test was used without correcting for serial correlation. To account
for ine.possible inflation of significance levels that results from serial correlation, P val-
ues falling between 0.05 and 0.01 were termed "marginally significant" because their
actual P value might be more than 0,05. P values less than 0.01 were termed "significant"
because their actual P value was probably less than 0.05, A similar approach to determin-
ing significant trends with the seasonal Kendall test was ;" :d and reported as part of the
1991 re-evaluation of the Chesapeake Bay nutrient reduction strategy,* except that mar-
ginally significant trends were not identified.
The tables of seasonal Kendall test results list the sample size in months, the median
trend slope in mg/L per year, and the ?** score for significant trend. A large 1 score indi-
cates a statistically significant monotonic trend: Z beiw«n 1.96 and 2.58 was considered
"marginally significant," with F between 0.05 and 0.01; Z>2.58 was considered "signifi-
cant," with f<0.01. The y? value for seasonally tests whether the trend is homogeneous
over different months. A small £ value and a large P value (>0.05) indicates there were
no significant seasonal differences in the trend. (Trends were not upward in some seasons
and downward in others.) Almost all parameters in which significant trends were found
had homogeneous trends over different months. The results were corrected tor ties or
concentrations from the same month that are the same in : cr more successive years. The
results were also checked to see if ties affected more than 50 percent of the results for any
'••W;,,._.f Quality Characterization Report for the 1991 Ri-Evaluaiics o» -i ChewF«ke Bay Nutrient Re-
duction SiMtegy," tdruitj. CEP. Amwpoiii.'Md, (19?!,'.
**T«i statistic used to determine ? value.
.->
Trends in Phosphorus, Nitrccsr. and Dissolved Oxygen,
tO 1992
-------
UP n*>re
observations
IKS; ™nlwere *0 cases whcn
Percent Change
StegejPer Year) x 8 Years
1985 WY Mean
x 100,
J^rTTff-*» fc «—•' K™M *£>'» S£ tH<>H ™K"990 WY>-
"**"^^"IIfe'^fti».lcta|erata1S,S,T!™f. ovc""P"""ichMgc
^K^ftKisr "nu!uai" ^-^-Ss
r-Wj^S^SSS^-^-te
baywidechange (for TP), ' f°r lhe one l«™»aer wift'a significant
ional
Percent Change = £»d Point-Srart
DO deficit, and DO volumes
provements
Start Point x 10° •
^^^^
"" Improven*nts ** n^ients, DO delta,
- Inmasln% Ieve'^ are im-
goals set for Chesapeake fiLTuvLt ± d "^ Ihe habltat req«^™ms and CBP
and for species sensitive to low DO feSTSf" ^ ^ establish«d for SAV
does not currently meet one of the SAV hi ! * W imProvinf trend in ™ area lhat
aid » living resource restoration efforts "V**™** * DO'goals, .hat trend will
concentrations or the minimum Secchi «fe« ^h^ *™m KprCSMt 'he maxi™un!
based on -rowing season median vZ^SAV ^^ SAV gr°Mh The^ are
' the SAV growing season is April through Octo-
Trends in Phosphorus, Nitrogen, and Dissolved O
1984 to 1992
-------
ber in most of Chesapeake Bay-5 For this reason, trends in these three parameters were
evaluated over the whole yc;ir (12 months) and also over the April through October peri-
od (7 months). There are ats.) SAV habitat requirements for two parameters that were not
analyzed in this report5: toi.il ^ujpesTckd sorids and chlorophyll a.
The benchmarks for improvements in DO are based ori four target concentrations:
0.2,1,3, and 5 mg/L, The 0.2 mg/L benchmark is based on the anticipated effect of the
40 percent nutrient reduction strategy1: a reduction in the volume ofanoxre waters (de-
fined here as water with DO concentrations less than 0.2 mg/L). The last three
benchmarks (1,3, and 5 mg/L) were established by the Habitat Restoration Goal for
DO,11
ADJUSTMENTS FOR CHANGING DETECTION LIMITS
CBP monitoring data have method detection limits (MDL), which represent the
lowest detectable concentration of that parameter. Analytical results that are less than the
MDL are censored by setting them to the MDL and are identified with a separate vari-
able. Parameters with observations censored at the MDL pose two problems for trend
analysis: They may bias the slope, since'the detection limit values are greater than the
true values, and they may produce a statistically significant trend when none existed if
the MDL changed consistently over time. The first problem is avoided by the use of me-
dians in the seasonal Kendall test. Censored data have no effect on the slope as long as
the censored values make up less than half of the observations.9 Resolving the second
problem is more complex. Several of the parameters analyzed had reductions in MDL,
and the seasonal Kendall test results were apparently affected by these reductions.
Reductions in MDL occurred in all four of the nitrogen and phosphorus parameters,
but detection limits did not change for DO or Secchi depth. For nitrogen and phosphorus
parameters, below detection limit (BDL) values were set to one-half the MDL before in-
terpolation, as in the previous analyses. For one parameter (TN) the MDL reductions
were small enough to be negligible.4 The effects of moderate reductions in MDL, which
occurred in TP data, were checked by raising any lower values to the highest MDL dur-
ing the lime period. When the detection limits went down substantially over time, as they
did for DIN and DIP, the possible effects were checked with four separate analyses, using
two MDL adjustments and two time periods. These included setting BDL values to zero
and analyzing only data collected after October 1988, after the largest reductions in
detection limits had occurred. The appendix provides a listing of the frequencies of BDL
values for DIP and DIN.
SUSQUEHANNA RIVER FLOW
Correlations between upper Chesapeake Bay water quality and Susquehanna River
flow we.re analyzed to examine the strength of any relationships. The flow data used were.
tog-tramforrned monthly means of the daily flow at Conowingo. Md. Log transforma-
tions of How data made their distribution closer to a nonvtu! distribution. Because now
data and water quality data tend to show serial correlation, the P values listed are approx:
imate. The Pearson (parametric) correlation was performed '-vith the correlation
procedure in SAS.10
::£
10
Trer.cs in Phoscnorus. Ni;ro;er. =ntj Dissolved Oxygen, 1984 to 1992
-------
PHOSPHORUS.
The IWQ phosphorus parameters analyzed were TP *~A r\m L • t •
«** (001
•»' -Wear to T«,
«•)- nil* » tfe MDL change,
ing;
for DIP con-
I. Eghl years of data(1984 to 1992), wUh
for DIP.
^^
'' " ^ WC Ci
•cant trends that wcm caused by MDL c' WCrC C°mpared to climinate
eiWna^^
caused
wa
Tliis approach to identifying
>ppe«d ,0 be caus5d bv
DIP
BDL
»ny trads tha,
NITROGEN
The two nitrogen
shows Md enrichment
and D^- W was chosen because I,
DIN Includ« ">= forms most readily taken by
Trends «n Phosphor, Nitrogen, and Dissdved OXySeo.
,334 to 1952
-------
phytoplankton. TN is calculated from total KjeWahl nitrogen whole plus nitrite/nitrate
(NCKj) in early main stem data and from tolal dissolved nitrogen plus paniculate nitro-
gen in later data. DIM is calculated from nitrite/nitrate plus ammonium (NH^. As with
phosphorus, the total parameter had method changes, although it had minimal MDL re-
ductions, and the dissolved inorsank parameter had no method changes and large
reductions in MDL.12
The changes in TN MDL were small enough to have no effect on trends." The de-
clinin* MDL for DIN were dealt with using the same four treatments used for DIP,
except that trends could not be estimated for segments sampled by the Virginia Institute
of Marine Science (VIMS). This affected the four segments with a majority of VIMS sta-
tions: Tangier Sound (EE3), Mobjack Bay (WB4), and lower Chesapeake Bay segments
CB6 and CB7. VIMS detection limits for DIN had a series of large reductions that con-
tinued until July 1990, which left only 2 years of data after the reductions stopped. (See
Table A.2 in the appendix.) This was not enough time to evaluate whether any trends
were affected by declining MDL. •
SECCHI DEPTH ' - c '
Allhough Secchi depth has a lower MDL (0.1 meter), it did not change and it was
almost never encountered. Thus, There were no MDL problems for Secchi depth. There
were more ties in Secchi depth man in other parameters, but they still did not exceed 50
percent for any month.
DISSOLVED OXYGEN
Eight DO metrics were calculated and interpolated, and seven were analyzed statis-
tically for trend over «he whole main stem and for each of nine main stem segments. DO
saturation trends were not analyzed, and data from EE3 were not analyzed for DO trends.
All DO metrics were analyzed for trend over the 4 warm weather months {June through
September) when low DO is most frequent. This lime period is also used in the assess-
ment oflow DO levels in CBP time-variable model output. Other months were excluded
because they would tend lo obscure any trends that occurred during the warm weather
months. DO has no detection limits, since values of zero can occur. The following eight
metrics were calculated:
1. Monthly mean DO concentration: An upward trend shows improvement,
2. Monthly mean DO saturation concentration: This is calculated from water
temperature and salinity12 and expresses the potential DO concentration at
that temperature and salinity if the water was saturated with DO. Trends are
neither improvements nor degradation but represent changes in the amount
of oxygen that can be held in solution due to changes in water temperature
. and/orsalinity. For this reason, trends were not calculated for saturation; it
was used as an intermediate step in calculating the next two parameters.
3. Monthly mean DO delta concentration: This is calculated from DO satura-
tion minus DO concentration. To eliminate the streets of any supersaturated
conditions. DO delta was set to zero if less than zero. A downward trend
•jhows improvement. (The DO concentration is getting closer lo saturation.)
Trends in Phosphorus. Nitregsr. 2nd Dissolved Oxygen, 1984 to
-------
iow uu was from below the . *UUICW1U1
RESULTS AND DISCUSSION
SUSQUEHANNA RIVER aOW
*»*ould be 6
median. Annual
1991 and
total flow
?• « averageyear
with flow **lw the
(October
lowed by 7 months
'
2)' ^ WY w»h «he highest
UCCd the
5 momhs
flow,
er flows over eithe
seasonal Kendall tests.
^^ °f t£>lal "1°nfhly Susq«e^nna Riv-
***' finl a"d JaSt 4 ^ «i-«
or inoms o« 8 v-
ndall tests. K^'Z *£***' f ^ finl a"d JaSt 4 «i-« '"a
fer any ^
the water quality parameters probably werl S ft f^ °bsemd ^ levels rf«*« of
in a simple fashion. y CTe retated to mterannual changes in flow, but not
pic relationship between nutrients an JLw C°TOlatl0ns in Table ] • * *ere was-a sim-
with flow, with the strongest correlations ' "*"? WOu!d show P°siti ve ^relations
in surface sampJes. Correlations shouM EeneS!!' CB' (Su^uehanna Flats)- especially
phonis because nitrogen, especially nitrat- • 8Cf * nitr0gen than for Phos-
«he lagged correlations should be strong ' m°rC '" water lhan PhosPho™s, and
takes water from the fall In* longer to S l^"*™ (mh<:r from lhc fa" lim b«a«se it
Trends in Phosphorus, Ni.rogan, aod Dissolved Oxygen. 1984 to f 992
13
-------
1985 1986 1987
Cl Total Flow
1988 1989
Water Yeai-
1990 1991 1992
# Mbnths > median
Figure 2. Total annual Susquehanna River flow (bars) and number of months above median flow line
(water years 1985 to 1992).
Table 1. Correlations between log mean monthly Susquehanna River flow and mean monthly con-
centrations of water quality parameters (with P values inr parentheses).
Parameter Months With C81
CB2
CB3
CB4
C85
TP
TP
/DIP
DIP
DIP
DIP
TN
TN
DIN
12
12
12
12
7
7
12
12
12
Flow
Lag
Ftow
Lag
Flow
Lag
Flow
Lag
Flow .
NS
NS
NS
NS
NS
NS
0.394
(0,0001)
0.285
(0.0051)
0.432
(0.0001)
NS
NS
-0.290
(0.0042)
-0.310
(0.0022)
NS
-0.277
(0.0404)
0.651
(0.0001)
0,545
(0.0001)
0.660
(0.0001)
-0.294
(0.0037)
-0.260
(0.0109)
-0,361
(0.0003)
-O.484
(0.0001)
-0.372
(0.0048)
-0.463
(0.0004)
0.737
(0.0001)
0.672
(O.CC01)
0,775
(0.0001}
-0.426
(0.0001)
-0.314
(0.0019)
-0.485
(0.0001)
-0.359
(0.0004)
-0.468
(0.0003)
NS
- 0.618
(0.0001)
0.715
(0.0001)
0.737
(0.0001)
-0.538
(0.0001)
-0.394
(0.0001)
-0.554
(0.0001)
-0.360
(0.0003)
-0.540
(0.0001)
NS
0.547
(0.0001)
6.673
(0.0001)
0.678
(0.0001)
14
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
__ Parameter
DIN
DIN
Secchf Depth
Secchf Depth .
Secchl Depth
Secchl Depth
DO
i"\J"S *
DO .
DO Delta
DO Delta
DO Deficit
DO Deficit
sgend and note*
Months With CB1
12 Lag 0.310
(0.0022)
7 Flow 0.568
(0.0001)
7 Lag 0.333
(0.0130)
12 Flow -0.418
(O.OOQ1)
12 Lag -0.315
7 Ftow
7 Lag
4 Flow
4 . .Lag
(0.0019)
-0.736
(0.0001)
(0.0426)
0,398
(0.0242)
0.361
(0.0461)
4 Flow NS
4 Lag 0.368
(0.0418)
4 Flow . NS
4 Lag 0.368
' (0.0418)
CB2
0,561
(0.0001)
0,791
(0.0001)
0.476
(0.0002)
-0.382
(0.0001)
-0.404
(0.0001)
HJ.578
(0.0001)
-0.340
(0.0112)
0.448
(0.0102)
NS
NS
NS
NS
NS
.
CBS
(0.0001)
0.813
(0.0001)
0.360
(0.0070)
-0.222
(0.0300)
(0.0017)
-0.334
(0.0119)
NS
NS
NS
CB4
•
0.753
(0.0001)
0.772
(0.0001)
0.386
(0.0036)
NS
hie
I»O
NS
wo
liw
MC
I'*.*
MC
MO
NS NS
NS -0.361
(0.0461)
NS NS
NS -0.361
(0.0461)
"
CB5
0.690
(0.0001)
0.697
(0.0001)
0.384
(0.0038)
NS
NS
|L »n
NS
Mo
NS
HIT*
NS
NS
NS-
NS
NS
T—kr""K>"w"'y significant (jR>0 05)
t ,„_ i f-"'m- «-'ow—Log mean monthly flow (log of mean ' '
lagged) or CB4 (lagged) and
cormJations with flow in all of ,be
positive collation is expected
.ached to sediment,
^ negatlve
(or CB°2
for
°f PhOSph0™S had "egative
T C°'TeIa»ons- even ^»gh a
osPh«™s, part of IP, is often «-
per station, while the values for the other wa^! r* dtP'h h3S °nly °DC lneasu«nw
resulls from two or four dcDita T^, 7 q >y Paramct«" were averaged over
rour depths. 7T,e correlanons of flow with Secchi depth were nega-
Trendsin Phosphorus. Nitroge,, andDissoh^edOxygen, I984te.19«
15
-------
live, presumably because higher flow brings more sediment, which reduces water clarity.
Correlations wiih uniagged flow were stronger during April through October than during
the whole year.
Some of the DO metrics showed positive correlations with flow or lagged flow in
CB1 and CB2, but the conflicting nature of the correlations means they wens probably
not meaningful. The correlations suggest that higher flow is associated both with higher
DO concentrations in the current and following months (improvement), possibly due to
increased aeration, but also with higher DO delta and deficit a month later (degradation).
PHOSPHORUS
Total Phosphorus
Results show a statistically significant downward trend (improvement, P<0.01) bay-
wide, in upper Chesapeake Bay segment CB2, and in lower Chesapeake Bay segments
CB6 and CB8,(see Table 2 and Figure 3), There were also marginally significant im-
provements (/kO.QS) in upper Chesapeake Bay segments CB 1 and CB3 and loweY
Chesapeake Bay segment CB7 (see Table 2 and figure 3). One segment with a significant
trend "(CB2) had a barely significant seasonal heterogeneity: the %2 value was30.6, slight-
ly more than the critical value of 19.7. However, since only 3 months had increasing
trends (November, January, and February}, the overall decline in CB2 appeared to be val-
id.
Changes in TP detection limits had little effect on the trend results. An interpolator
run with any values below 0.01 mg/L raised to that value had significant trends in the
same segments, with very similar slopes.
Figure 4 shows average monthly TP and DBF concentrations for each segment, DIP
(thin line) is shown for comparison to TP levels; it was also graphed separately. Segments
with statistically significant or marginally significant TP trends have a trend line connect-
ing the 1984 to 1985 mean and the 1991 to 1992 projection based on the seasonal
Kendall slope.
The median baywide percent change in TP over 8 years (1984 to 1992), based on
the seasonal Kendall slope, was 16 percent plus or minus 8 percent (90 percent confi-
dence interval). This is slightly less than the previous baywide percent change estimate
for TP. which was 19 percent.3 One reason for the lower percent change is that March
" 1985 TP data, which were included in the previous analysis, were subsequently deleted
from the data base due lo quality assurance problems and were not used in.lhis analysis.
Percent change values for individual segments are listed in Table 2,
The,declines (improvements) in TPin upper Chesapeake Bay segments CB1, CB2.
and CB3 were probably related to declines in Susquehanna River fall line concentrations.
There were statistically significant (/*
-------
_
Trend r*su«s for interposed monthly mean to«a» phosphorus by segmen(
Segment
(CBP)
" *• r
CB1
CB2
CB3
CB4 .
085
CB6
CB7
CB8
WE4
EE3
Slope
mg/L/yr
-0.00067
-0.001
-0.002
-0.001
• - .
-
-0,00092
-0,0008
-0.0024
' ~ '
- '
/Trend
-2.72
-2.15
-2.87
-2.48
-
—
-3.33
-2.53
-4,86
-
-
P
O.OOeqr'
0.032
0.0042
0.013
NS
NS
.0.95
>0.1
-rf).05
>0.2
>0.5
>0.5
>0.7
%•
Change
~
16
16
29
17
21
19
* &
36
r
Legend and noter ; — : — — -• ~ __
i-cycifv eu HJ note: ' • _
^s^Ss^i1^
'.bodl rbe highest concern t
2) of these tbce segments,
Jated to changes in
with sig-
* ^ ™
*"•*" {$Ce Table
"
1985 and 1990, while
1991, teed on watered
34 percent of the watershed tota
ing atmospheric deposition).
wate.hed totaUoads and 58
Dissolved infante Phosphorus
Reductions in MDL
^ Wduced by 4° Percent
'° fc» 8
of
Trend, in
s. Wro^n. and
Oxygen. 1984 ,o ,992
-------
C81
'•fl
Upper Chesapeake Bay
CB7
Lower Chesapeake Bay
-CBS
Trend over ail
main stem segments
change
sgnGcam
ngrofiont
Figure 3. Total phosphorus trends in Chesapeake Bay main stem segments (October 1984 through
Sepiember 1992).
Trends in Phosphorus, Nilroge
.«. and Dissolved Oxygen, 1984 to 1992
-------
Nnes had signincannfeodg
Note: Segments
Total Bay
CB1
CB2
CB3
CB4
Trends in Phosphorus, Nitrogen, and Dissofved Oxygen>
1984101892
19
-------
COM Oats oat* 0*1? ecu OaU COB to'1
'
Figure 4. Average monthly concentrations
(1984 10 1992) (continued). .
of total phosphorus and dissolved inorganic phosphorus
Trends
in Phosphorus,-Nitrogen, and Dissolved Oxygen; 1984 to
1992
-------
No. of No. of
Table 3a. BOL data set to one-half.
Main Stem C8P Segments
£5^^LJ?iJE^_E!L_CB1_CB8 WE4 EE3
Table 3b. BDL data set to zero.
Main Stem CBP Segments
y^!^-^-^^^L3!L^L^L«>^ **
Legend and note:
'"'niffcant improvement (P
-------
Mouth of Chesapeake
E-c/{C£,*;-12 months
Middle Chesapeake Bay
(CB4J-7 months
Trend over all
main stem segments
nojjgiifkaiH
change
nmgiiufly
agraficsnl
dcgraJacn
Bgiificant
Figure 5. Dissolved inorganic phosphorus trends in Chesapeake Bay main stern segments (October
1984 through September 1992).
Trends in Phosphorus. Nitrogen, and Dissolved Oxygen. 1984 to 1992_
-------
0.04
Censored data set to haff of defection limit;
Censored data set to zero.
Note: Segments with trend fines had significant trends.
Total Bay
Od$4 Oet85 Od 86 Del 87 CW8S CW89 Od90 OdSf Oc*92
CB1
CB2
CB3
OflM CtaB MM 0917 OnM Dan Ot»«J Oall 009J
CB4
ct-w Dan can
OclK MM dan MIT OcM OoH OctM Mil
Figure 6. Average monthly concentrations of dissolved ii
inorganic phosphorus (1984 to 1992).
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1934 to
1992
23
-------
Censored data set to haH of
Censored data set to zero.
Note: Segments with trend lines had significant trends.
CBS
tit
ecu tew MIS oai? (tea OCB OQM Qzr. CcK
CB7
fcCJ-
1 ;
. , t\ fr\ R i A < in
OCS< ZcK Catt 0017 OaH
-------
Trend results for interpolated monthly mean dissolved inorganic phosphor
by segment (12
Segment
(CBP)
Afl
CB1
CB2
CB3
CB4
, CB5
CBS
CB7
CB8
CBS
WE4
EE3
flOAH Qr\H A,
BDL Slope
Treatment mg/Lfyr
•. •- • - .
- • . _ '
- -
..- -
1 ""*, »
-•
-
1/2 -0.00069
0 -0.00059
_
ZTrend P
- NS
NS
NS
NS
NS
- NS
NS
NS
-3.7S 0.00018
-2.36 0.018
Lltf*»
- NS
* ikm
- NS
X2
Seasonal P
7.62 >0.7
11.77 >0.3
, .
— — .
Change
•— --— — —~—^.
31
29
.-
"•"Vs' iu 01 iu rwie; . - •
menu CB6
achieved the
ntarby
* tha» had significgnt down trends had already
DIP (0-01 mg/L in raesohalinc
*-VValfr QualHv RC5loraiion Priori,i« for Living R«OUre« Report."
(draft), CBP. Annapolis, Md. f)993|.
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 lo 1992
25
-------
Table 5. Trend .esute for interpolated monthly mean dissolved inorganic phosphorus by segment
(7 months, April through October).
Segment
(CBP)
All
CB1
CB2
CBS
CB4
CB4
CBS
CB6
CB7
CB8
WE4
EE3
BOL Slope .
Treatment mg/Lfy." ZTrend
. - ' — • •
«w ~~f """'
_ . m — —
«. — *"
t/2 -O.0003 -2.81
0 -o:000267 -2.21
— — ~
*
_ _ ~
— — *""'
_ • -
— -• "~
- - • -
P
.BB,——.....!--*^^™*1
NS
NS
NS
NS
O.OOS
0.027
NS
I ^t^J
NS
ITIN.J
NS
n\^
NS
NS '
1 TlSJ
NS
* 7o
Seasonal P Change
" —
— — — ,
— , ™- _
_" — —
1.37 >0.95 31
2.33 >0.8 28
_ — ' —
„ — . • «,
^ -*/'-•
HHB1F ™™ ' '™~
-• '-*•««
""".',•
ThltotfSurrS^of months W tor all segments was 58 (AprtJ385^through SapMar
^3V a I deoths' resufts shown (or segments with significant (P<0.01, underlined) trends
0.05 Indicates the trends were homogeneous. Where there are two slopes for trie same sag
ment, they "bracket" the true slope.
NITROGEN
There was no significant trend baywide for TO (see Table 6 and inset, Figure 7).
There was a marginally significant increase (degradation, ?=0.027) in segment WE4,
which includes the mouth of the York River (see Figure 7).
Fi-ure S shows average monthly TN and DIN concentrations for each segment. DIN
(thin line) is shown for comparison to TN levels, it was also graphed separately. Seg-
ment with mar&inallv significant or statistically significant TN trends have a trend line
connecting the ?9S4 to 1985 mean and the 1991 to 1992 projection based on the seasonal
Kendall slope,
The lack of any TN trend in upper Chesapeake Bay is consistent with the How-ad-
justed TN loads at the Susquehanna River fall line. Data from this station showed no
significant changes in loads (F>0.1) between 1984 and 1990.*
Trends in.Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to
-------
Table 6. Trend
results for interpolated monthly mean total nitrogen by segment
SeasQ"a' P Change
Segment
(C8P)
— I,
AD
CB1
CB2
CB3
CB4
CBS
CB6
CB7
CB8
WE4
EE3
Slope
tng/Uyr ZTrend P
~
NS
~ ~ NS
NS
NS
NS
- . -. NS
NS
NS
- - NS
0.006 22\ 0,027
- •" - NS
5.74 >0.8
10-
percem
^
Dissolved Inorganic Nitrogen
watershed
reason,
1 Over all 8 years;
'"
^
and 54 percenrof the controJIable
:° have
were also analyzed four different ways-
Trends In Phosphorus. Nitrogen, and Dissolved Oxygen. 1984 to
1992
27
-------
Trend overall
main stem segments
noBgnslkam
change
mstrgiruBy
sgmJBoiM
degndaoon
Figure 7, Total nitrogen trends in Chesapeake Bay main stem segments (October 1964 through
September 1992),
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 199
-------
TN
.DIN
Note: Segments with trend lines had significant trends.
Total Bay
OdB6 Oct«7 Oct88 Oet89 OctW Od91 Oc«9Z
C81
CB2
OdN OdIT Caw oa'll M* tat, tx)
CUM OOB CUM OBW otiit can oaw MM
CB3
CB4
MM OoM (taw CHIT CttN Od» od» Oat! OaH
of total nitrogen and dissolved inorganic nitrogen {1984 to
Trends in Phosphorus. Nitrogen, and Dissolved Oxygen, 1984 to
T992
29
-------
Note: Segments with trend lines had significant trend
OSM Cc» CaM CsV «« »»» CWR Cell Can
del; Gets Csll OS 17 0=11 Oc» OcK Csl: CS
tan Den OctM Can can
Figure a. Average month!/concentrations cf total nitrogen and dissolved inorganic nitrogen (1984 o
15=2, (continued).
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to
-------
2. Over the last 4 years;
3. Starling in October 1988, when most detection limits were lowered;
4" of Rni0!* ** !° eltlier """^ "* MDL * ** '° zero lo asscss «*
01 BDL data on trends.
beie
average monthjy DIN ««tt««n«i«is for each segment with BDI
t0 ^ (thin Iine)-
v« ap, and the thin lineIs only visible in a few segments There i« a natt*™ ~r •
,
SECOHDEPTH
Trends in Phosphorus. Nitrogen, and Dissolved Oxygen. 1984 to
1992
31
-------
Table 7." Trend results tor interpolated monthly mean levels of dissolved inorganic nitrogen by
using four different method detection limit treatments.
Table 7a. Below detection limit data set to one-half.
Main Stem CBP Segments
No. of No. of
Months Years All CB1 CBS
CB3 CB4 . CBS C86 GB7 CBS WE4
12
12
7
7
8
4
8
4
_
IM
—
I
_ _
IM I
_ —
IM I
_ . - - U-
| I IM IM+
_ '- IM
| i IM IM
k IM
IM+
I
i _
1+ lM+"g
IM+ -^1
IM "1*
- "*I
Table 7b. Below detection limit data set to zero.
Main Stem CBP Segments
No. of
Months
12
12
7
7
No. of
Years
8
4
8
4
All
-
(M
-
I
CB1
• -
1
-
IM
CB2
•-
1
-
1
CB3
1 .
-
1
CB4
-
1
-
1
. CBS
- • '
IM '
-
IM
CB6
1+
1M+
-
IM
CB7
l+-
IM+-
—
1
CB8 WE4
IM*
- . • -
- —
„
EE3 '
1M+
-
—
IM
Legend and note:
J—Significant improvement (P<0.01).
IM—Marginally s^-^ant improvement (P<0.05).
Dash—No significant trend (P>0.05).
+These trends were not fdenlifed as real because detection limits in these segments continued to de-
cline until July 1990; therefore, the marginally significant 4-year trends could be caused by declining
detection limits.
7 months—April through October only, SAV growing season in tower salinity zones.
The annual pattern of attainment of the KD requirement suggests an inverse correla-
tion between Susquehanna River flow and Secchi depth in these segments, which was
found (see "iable I). However, the lack of a significant monotonic trend in flow over this
period means that the marginally significant trends in Secchi depth in upper Chesapeake
Bay wer.* n-x n simple consequence of a trend in flow.
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1
-------
Trend over aB
main stem segments
degradUKn
CSC.MN1D.7SS
Figure 9, Dissolved inorganic nitrogen trends in rn
through September 1992). ^nesapeake Bay main stem segments (October 1984
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to
1992
33
-------
Censored data set to hall ol detection limit
Censored data set to zero.
Note: Segments with trend lines had significant trends.
Total Bay
• "'•••*'••
OctS4 OclBS Oct86 CMS? Qc»88 X)ct89
CB1
Od91 Oct92
CD2
Oati Outs 03 « OSU CcSi Daw Oci» C3S1 Oc!»
CB3
CB4 .
M-a
Figure 10. Average monthly concentrations of dissolved inorganic nitrogen (1984 lo 1992),
J4'
. Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
Censored dala set to half of detection limit
Censored data set to zero
Note: Segments witfi trend Hnes had significant trends.
CB5
C86
CB7
CBS
Oaii
EE3
WE4
*»» te*> Cr.i
-------
CB1
ix> significant
Northern and Upper
Chesapeake Bay -?
months
marginally
Trend over all
main stem segments
smgtnallv
CSCAWIOJW
Figure 11. Secchi deprh trends in Chesapeake Bay main stem segments (October 1984 through
September 1992).
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to
-------
Note: Segments with trend lines had significant trends.
Total Bay
Oct84 odes CW86 octe? Odsa octes cwao oasi
CB1
Can
CB2
J. s
f M-
€
z t-
l-i
oaw OHM oaw OHM Can ai» con oas
C83
ten; oatf Oair OaM Octf cctj Or.»i
CB4
Figure 12. Average monthly Secchi depihs (1984 to 1992).
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
37
-------
Secchi depth
Note: Segments with trend Hues had significant trends
CB5
CBS
e=n DOB OCK ts&a caw ccii oc» doit Os»
MM OsM OcH Octll Oam daw on» Oesi ecu
CB7
CBS
O=!< cess CSB Oisir OEM oats O-JM Ccii OsH
EE3
WE4
OeSi Osli CsM Os f» Oail Oe!> Ca» 001: CsW
,
Oon OCSJ Osi! OaW OfiH OcIS OSM "ell
Fiaure 12. Average monthly Secchi depths (1984 tc 1992) (continued).
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 19841° 1992
-------
. Tfend "** for lnlc^ated monthly mean Secchi depth by segmen, {7 ^^
Apfj|
Segment
(CBP)
All
CB1
CB2
CBS
CB4
CBS
CB6 '
CB7 ' .'.
CB8
WE4
EE3
Legend and note?
"PI— t,^A_l __. .
Slope
mfyr
-
0.017
0.025
_
-
-
-
-
-
-
-
• .>i..ii.i,..
ZTrend p s
1 ~ ~—i n .,„.,.
NS
1-97 <0.05
2.38 <0.017
- NS
- NS
- NS
NS
NS
NS
NS
NS
X2
Seasonal
<0.7
>0.2
%
Change
18
34
over (he J984-to-1991 period
DISSOLVED OXYGEN
9
both ^
ccnmioo and
becausc no
.
Trend r^ufe for DO con-
° C°nCemrations arc "« '"own
*B. Dobler. MDE. unpublished analyses.
Trends in Phosphorus, Nilrogen. and Dissolved Oxygen, 1984 to
1992
39
-------
Mouth of Chesapeake
Bay (CB8)-4 months,
both parameters
00 delta is DO at saturation minus DO.
DO deficit ts mass at saturation minus
mass present
Trend over an
main stem segments
1 noagriScajtt
J change
sgmficant
significant
7771 narguiafly
",',':.. ajrtacant
*':. J dc^radiocn
Figure 13. Dissolved oxygen delta and dissolved oxygen deficit trends in Chesapeake Bay main stem
[October 1984 through September 1992).
4»
Trends in Phosphorus. Nilrogen, and Dissolved Oxygen, 1984 to 1
-------
oxysen deita
Segment
(CBP)
" AB
CB1
CB2
CB3
CB4
CBS
€86
CB7
CB8
WE4
Slope
mgFUyr
-
, -
-
' -
.- .
-
-•
-
' 0.038
-* *
2Trend P
NS
NS
NS
NS
NS
- NS
NS
NS
2.50 0.012
NS
legend and note: '~ ~~
0.57
0,9
77-
«fc. ^d on the ««JES3 te ^Al S^r" fcI99i l°1"2iw*!c-
declining trends b DO cwceS»T. t ? ^ ^^^ appear lahave
•W statistfcally *j££Z£!£^ 1 Seg>mntS Md SCfimoit CB8' these ««
Septrmber). . nca* **cn tested over «« waitnwea.hcr period only (June through
(June tough ^TmiLT^Tr ove- •" 4 """^ of thc wa™ wcather
summer in the ^^SSS^SS^i^^^^S^ *«
CB5). Reducing the volume of anox»c warer ifr\ * S"1^ SCgTOnlS CB4 and
em Auction strategies. Ut trend rwuhs f«r CheSap!ake ** is a maJ°r g°al of nutri-
ibe other target concentrations we« lo !i f M'C V°lume and the volumes of *««• *
CB5 (segmeL with rcSle" JJ Si 5SS ^ f8"** " "*«*»« CB4 «^
t»on categories were fairly consign, from ^T^ *??** Bt £he Wghcr concen{ra-
iess than 0.2 and 0.2-to-l m"/L cateLri^ r ^ *"* S0me $hiftin« betwee" the
CB7, also rehcively lar Xe SapCake ^ >1«menl« CB6 and
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen. t984 to 1992
41
-------
DO concentration
DO delta
Note: Segments with trend lines had significant Ire
Total Bay
OclSS OclS6 Octfr Oct88 OdS? OcSO Od91 OtiSZ
Sex OeflJ OcSi Ce»T COM OeSM CcS3 Oc»i
Figure 14, Average monthly cor,c=nlralions of disscivsd oxygen ard.dissolved oxygen delta (1984 to
1982,
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to
-------
-V.
OOconceolration
DOdefta
Note: Segments with trend lines had significant trends.
CBS
CBS
CONC
OQ.TA
**» oca* tan con
KWC
KLTA
CB7
ECITA
CB8
1— CCNC.
WE4
COMt
WLTA
of dissolved oxygen and dissolved oxygen delta (1984 to
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1904 to
1992
43
-------
DO Concentration Range
3.0-5.0 Q 0>2_1<0
Total Bay
1985 1986 1987 1988 1969 1SSO 1991
Figure 15. Total volumes of water with dissolved oxygen conesntrations below 0,2, 1, 3, and 5 mg
(June mrough September. 1385 to 1992).
&
4-!
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen. 1984 to 1
-------
DO Concentration Range
D 3.0-5.0
D 1.0-3.0
0,2-1.0
0.0-0.2
CB5
f!
L
CB6
CB7
f-
I
i
r
Figure 15. Total volumes of water with
(June Ihrough September. 1985 to 1992)
5>o
CB8
1«« 19W IMS IMS ' 19*, 1991 ,,„
WE4
concenlrat>ons below 0.2, 1. 3, and 5
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 »0
1992
45
-------
usually had the lowest total volume of water below 5 mg/L, This is probably due to re-
duced stratification in low flow years.
Table 10. Trend results for interpolated monthly mean dissolved oxygen deficit by segment (4 warm
weather months, June through September),
Segment
(CBP)
All
CB1
CB2
CB3
CB4
CB5
CB6
CB7
CB8
WE4
Slope
kg/yr* ZTrend
-
-
_
-
. -
-
. . -
- . -
143.4 2.04
P
NS
NS
NS
NS
NS
NS
NS
NS
0.041
NS
X2 • *
Seasonal P Change
_ — ._
-
- '
-
_
'•-'•:•
- ' - . _
_ '- ' = -
0,17 0.98 88
— — • —
*Uriitsarekgx1Q1
Legend and note:
Dissolved oxygen deficit is dissolved oxygen delta converted to a mass of oxy-
gen. The total number of months (/v) for all segments was 32 {June 1985
through September 1992); an depths; results shown for marginally significant
(P<0.05) trends only. A positive (up) trend shows a movement toward less de-
sirable conditions (degradation); NS—Not significant (fi»O.Q5). xz seasonal
and its P value (last two columns) are a test for homogeneity of the trend over
different months. A P value of more than 0.05 indicates the trends were homo-
geneous. DO data were not analyzed in EE3.
The marginally significant trends in two DO metrics at the mouth of Chesapeake
Bay (segment CBS) have no obvious potential causes. DO concentrations are generally
high in CBS (see Figure 14) and DO delta is quite low, so these trends are unlikely to
have any negative impact on living resources in CBS. The high percent change values (77
and 88 percent) appear to be partly due to abnormally low'values in the 1985 WY.
PLANS FOR FUTURE TREND ANALYSES
INTERPOLATING ABOVE AND BELOW PYCNOCUNE LAYERS AND SURFACE
AND BOTTOM LAYERS SEPARATELY
Several enhancements to the trend analysis methods are planned for the next trend
analysis update. The enhancements that may be implemented include interpolating above
and below pycnocline layers and surface and bottom layers separately. This will make it
possible 10 perform trend analyses of water quality in separate water layers. Trend analy-
ses of DO concentrations will focus on the bottom layer and the region below the
pycrtoclirK, where almost ajl of the low DO concentrations occur. Trends in nutrient pa-
-16
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen. J984 to 1992
-------
fOCUS °" the surfa« "H** layer
SAYS'8 SAV groWth> DIN' f WP Wi" fOCUS °" the surfa« "H
*ncc SAV habitat requirements are defined only for surface concentrations.
ACCOUNTING FOR INTER ANNUAL CHANGES IN FLOW
The seasonal Kendall test accounts for seasonal changes i
J* for changes in flow between ean.
ADDING PARAMETRIC TREND TESTS
ADDING TREND TESTS ON INTERPOLATED TRIBUTARY DATA
SUMMARY
Bay, «here shou,d be .-
nutrient levels. Improvtrends n DOTT ^ ™Provcmcnts
habita, in Chesapeake Bat Table 1]^^"^ 'he 2m°unt ofl™* reso
dines (improvements) in TP and Dml?! ' ^ ™K statisti«»y «W«ificam de-
impn>vtm;n,s in any o "uSS m^cs Sf.T?" ^ COfrC5P°ndinS
due to two factors- "CS-11"sIackofimProvi"g trends in DO could be
2. There has not been enough time for nn ~ ~
between nutrient leductiS^Sro^S0''*8' ^""^ ** 3 '^ kg
iments from rev ^P^6^"^. Nutrients siored in sed-
Itvtb .0 miuira reducSo'
any
are not currently met. This
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to
1992
47
-------
should promoic SAV restoration. Both of the segments ihai had improving trends in DIP
are already in attainment for those requirements, so these trends should have little impact
on SAV restoration. However, the improving trend in Secchi depth in one upper Chesa-
peake Bay segment (CB2) may lead to an increased frequency of attainment of the Secchi
depth requirement in thai segment in the future.
Table 11. Summary of trend results (October 1984 through September 1992).
Main Stem C8P Segments
Parameter
TP
DIP
DIP
TN
DIN
DIN
Secchi Depth
Secchi Depth
DO Concentration
DO Delta
DO Deficit
D0<0.2
DO<1.0
DO<3,0
DO<5,0
No. Of -fflgj
Months All C81 CB2 C83 CB4 CBS CB6 C87 C88 WE4 EElM
12 r IM I . IM - - I IM | - _ M
•^oi
12--------'!- ,:.•£•
i _-^£5BBl
-4m
* o «.•_—••• DM * ^St
•*O — 4. .*. _ • 4. t lit
7 -------- + + > + +||
12 - -• - - - "••'-." ~ ~ '-
7 - IM IM - - - - - - - - v
— ""* " ""
4 _ _ _ _ _'_._ _DM- - /
4 __.__--T-DM--'
4 '--.----. -----
4. _|__--------
4. ------ ----"
Legend and note:
I—Significant improvement (P<0.01).
IM—Marginally significant improvement (P<0.05).
DM—Marginally significant degradation,
Dash—No significant trend (P>0,05).
•i—DIN trends could not be assessed in these segments because detection limits did not stop declin-
ing untilJuly 1990.
7 months—April through October only, same as SAV growing season in lower salinity zones; 4
mon(hs_june ihrough September only, used as period of anoxia in three-dimensional model analy-
ses.
DO data were not analyzed in EE3,
See text (or explanation of DO delta, DO deficit, and DO volumes below the four concentrations.
Trends in Phosphorus. Nitrogen, snd Dissolved Oxygen, 1984 to 1
-------
. REFERENCES
1 • "Progress Report of the Baywide Nutrient Reduction Reevaluatioir 1991
uaiiOD Report No. 5 - CBPfTRS 92/93, CBP, Annapolis, Md. (1993).
2' Sf0^ Oxygcn Trcmb in Ihc Chcsap«>ke Bay (1 984-1 990)," CBPfTRS
66V91, CBP, Annapolis, Md. (1991).
3 Z^5 '" PhosPho™s w> *e Chesapeake Bay (1994-1990)," CBP/TRS 67/91
CBP, Annapolis, Md. (1991).
4" ™ends in Nitr°8ei» in *e Chesapeake Bay (1984-J990)," CBPOTS 68A>2
CBP, Annapolis, Md. (1992).
^
' ind R
A ' * ' ' ^peae ay S
merged Aquatic Tfegetation Habitat Requirements and RestoratiorTareets- A
Ttchiucal Synthesis,- CBPfTRS 83m, CBP, Annapolis, Md. (1992). '
6" ° S> " B3hnCr' "A '"^^'"ensional Interolator
ng
, n pon
hcauon to DISSolved Oxygen," Computer Science, Corp.,
S n1' f d °- ^iChwJ' "ResP°nscs rf UP^ Chesapeake Bay to Varia-
in p1Scharge of Ihe Susquehanna River," Kstoarits, 97235-249(1986)
6' '^ Edition- SAS Insliwte' Inc- c^ N.C
J I . Jordan, S C. Stenger, M. Olson, R, fiatiuk, and K. Moumford "Chesapeake Bav
D.SSO ved Oxygen Goal for Restoration of Living Resource ^Habifats S he
GuideJines
"
Sea Gran, Colege pak Md
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen. 1934 {o
1992 49
-------
50
Trends in Phosphorus, Nitrogen, gr,d Dissolved Oxygen, 1984 to 1992
-------
APPENDIX
DKSfW v^ °F BEL°W DETECTION LIMIT VALUES FOR
DISSOLVED INORGANIC PHOSPHORUS AND DISSOLVED INORGANIC NITROGEN
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992 51
-------
Table A.1. Percent of observations with below detection limit values tor dissolved inorganic phosphorus'
by' segment, laboratory, and water year.
Segment Laboratory Year %80L Mean MDL
CB1
CB1
CB1
C81
CB1
CB1
CB1
CB1
CB2
CB2
CB2
CB2
CB2
CB2
CB2
CB2
CB3
CBS
CB3
CB3
CB3
CBS
CB3
CBS
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CBS
CB5
CRUCBL
CRL/CBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CHUCBL
CHUCBL
CRUCBL
CRUCBL
CRUCBL-
CRUCB.L
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
as
86
87
88
89
90
91
92
85
86
87
88
89
90
91
92
85
86
87
88
89
90
91
9?
85
86
87
88
89
90
91
92
85
£6
19.4
0
7.9
0
0
0
0
0
3.8
0
0
0
0
0
0
0
8.6
1.3
2.5
0
. 0
0
0
0
22.2
6'.8
11.4
0.1
0
0
0.6
0
30.7
21.5
0.0055 ^3
.1
0.0016
"
— .:..«
- '
- ' -
-r;
0.007
-
r
-
-
-
- -
- -
0,007
0.0016
0.0016
-
-
-
-
-
0.006
0.0016
0.0016
0.0006
-
-
0.0006
-
0,0061
0.0016
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
^Segment Laboratory Year %BDL MeanMDL
CBS
.. CB5
CBS
CBS
CBS
CBS
— i .pBS.
.C85
-CB5
':;;,;;"-\'cB5 •
OB5
CBS
rv;' rCBS
. GB5
; CB6
CB6
CB6
CB6
CB6
CB6
CB6
CB6
CB7
CB7
CB7
CB7
CB7
CB7
. CB7
CB7
EE3
EE3
EE3
EE3
EE3
EE3
CBUCBL 87
CRUCBL 88
CRUCBL 09
CRUCBL 90
CRUCBL 91
CRL/CBL 92
VIMS 85
VIMS 06
VIMS 87
VIMS 88
VIMS 89
VIMS 90
• VIMS 91
VIMS 92
VIMS . 85
VIMS 86
VIMS ' 87
VIMS 88
VJMS 89
VIMS 90
VIMS 91
VIMS 92
VIMS 85
VIMS 86
VIMS 87
VIMS 88
VIMS 89
VIMS go
VIMS 91
VIMS 92
VIMS 85
VIMS 86
VIMS 87
VIMS 88
VIMS 89
VIMS 90
15.2 0.0016
0.9
0.6
0
0
0.3
81.8
89.4
75.6
37.6
27.4
62
18.1
7.8
.85.1
85.4
70.8
•37.8
30.5
62.5
18.1
10,5
83.5
83.8
75,8
34.2
25
55.6
19.5
10.6
100
100
94.9
36.1
47.4
69.4
0.0006
0.0006
_
0.0006
0.01
0.0105
0.0101
0.0016
0,002
0.0028
. 0.0006
0.0006
0.01
- 0.0105
0.0104
0.0016
0.002
0.0027
0.0006
0.0006
0.01
0.0105
0.01
0.0016
0.0022
0.0028
0.0006
0.0006
0.01
0.0105
0.0094
0.0019
0.0016
0.0024
-------
Segment
EE3
EE3
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
CB6 "
CB6
CB6 '
CB6
CBS
CB6
CB6
CBS
CB7
CB7
CB7
CB7
CB7
CB7
CB7
CB7
CB8
CB8
CB8
CB8
CB8
CBS
CBS
CBS
Laboratory
VIMS
VIMS
VIMS
VIMS
VJMS
VIMS
VIMS
VIMS
VIMS
VIMS
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
OOU
ODU
ODU
ODU
ODU
ODU
ODU
OOU
ODU
ODU
Year
91
92
85
86
87
88
89
90
91
92
85
86
87
88
89
90
91
92
85
86
87
88
89
90
91
92
85
86
87
88
89
90
91
92
%8DL
27.8
5.6
90.7
84.9
71.7
40.3
28.3
58.3
11.9
2,8
36.2
63.3
50
47.2
25.7
38.1
44.4
58.3
32.3
52.7
46.7
32.7
17.8
23.1
23.6
44.4
16.1
39.9
29.2
26.1
9
7.2
15
35.8
Mean MOL
0.0006
0.0006 •
0.0099
0.0105
0.0109
0.0016
0.0022
• 0.0028
0.0006
0.0006
0.01
0.01
0.0053
0.005
0.005
0.005
0.005
0,005
0.01
0.01
0.0052
0.005
0.005
0.005
0.005 '
0.005
0.01
0.01
0.0051
0.005
0.005
0.005
0.005
0.005
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 199
-------
~~ " "• • — — -^- —
If?!! *?', LPercent of observations with below detection limit values for dissolved inorganic nitroaen h
segment, laboratory, constituent parameter, and water year. y
Segment Laboratory Parameter Year %BDL MeanMDL % of DIN
Cil ~~
CB1
CB1
CB1
CB1
CB1
CB1
CB1
CB1
CB1
CB1
CB1
CB1
CB1
CB1
CB1
C.B1
CB1
CB1
CB1
CB1
CB1
CB1
CB1
CB2
CB2
CB2
CB2
CB2
CB2
CB2
CB2
CB2
CB2
CRUCBL
CRUCBL
CRUCBL
CRL/CBL
CRL/CBL
CRUCBL
CRL/CBL
CRL/CBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRL/CBL
CRL/CBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
' CRL/CBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
Both
NH4
NC*,
Both
NH4
- N023
Both
NH4
K023
.. Both
' . NH4
NQza
Both
NH4
N023
Both
NH4
N023
.Both
' NH4
NOz,
Both
NH4
NC-23
Both
NH4
N023
Both
NH4
NOaa
Both
NH4
N023
Both
85 0
85 13.& 0.0166
85 0 -
86 0 -
86 2.8 0.003
86 0 - .
87 0
.87 p
87 0
88 0
88 5.3 0,003
88 0
89 0 -
89 10.5 0.003
89 0
90 0 -
90 5 0,003
90 0 -
91 0
91 15.4 0.003
91 0
92 0
92 2.5 0.003
92 0
85 0 -
85 0
85 0
86 0 " -
86 0.9 '0.003
86 0
87 0
87 0
87 0
88 0
«.
1.3
—
_
0.3.
•mm
_
__
^^
'*_ J "
0.5
•— t
.
0.2
a.
_
0.3
,
_
0.3
^_
_
0.3
r~f
r_
_
_
_
1.4
• *_
_
_
"
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
55
-------
Segment
CB2
CB2
CB2
CB2
CB2
CB2
CB2
CB2
CB2
CB2
C82
CB2
CB2
CB2
CB3
CB3
CB3
CB3
CB3
CB3
CB3
CB3
C83
CBS
CB3
CB3
C83
CBS
CBS
CB3
CB3
C83
CB3
CB3
C83
CB3
Laboratory
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL "
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CHUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRL/CBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
Parameter
NH+
NOa
Both
NH4
NOa
Both
NH4
N023
Both
NH4
NC-23
Both
NH4
NC-23
Both
NH4
NO*,
Both
NH4
NC-23
Both
NH4
N023
Both
NH4
N023
Both
NH4
N023
Both
NH4
NC-23
Both
NH4
N023
Both
Year
88
88
89
89
89
90
90
90
91
91
91
92
92
92
85
85
85
.86
86
86
87
87
87
88
88
88
89
89
89
90
90
90
91
91
91
52
%BDL MeanMDL % of DIN ^1
OJ9 . 0.005 07 ^a
o - - ;'il
0 - ^
0,9 0.003 0.2 ~*M
0 - • - J5
° - M
5 0.003 0.3 -11
0 - _ J
0 - - • -
• •-•^
3.3 0.003 0.9 "^i
o - _ ':!
• , - • -^
0 - "-
1.7 0.003 0.3
0 _ _
^o . - : . . " :
2.9 0.0257 6.7
0
0 . -
0 - -
o - -
0
0 - -
0 - -
0 - -
0 ~- —
0 - -
0 - -
3.9 0.003 0.5
0
0 - -
4.4 0.003 0.7
0 -
0 - -
. 4.3 0 003 7.6
0
0
56
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
^Segment Laboratory
. . CB3
CB3
C84
CB4
CB4
C84
CB4
CB4
CB4
CB4
: CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CB4
CBS
CBS
CBS
CBS
C85
CBS
CB5
CBS
CBS
CB5
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRL/CBL
CRUCBL
CRUCBL
CRUCBL
' CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
CRUCBL
Parameter Year %BDL MeanMDL % of DIN
NK,
NQza
Both
NH4
N023
Both
NH4
NC-23
Both
NH4
" N023
Both
' NH4
NOzj
Both
NH4
NC^g
Both
NH4
NC-23
Both '
NH4
N023
Both
NH4
N023
Both
NH4
N0j3
Both
.NH4
N023
Both
NH4
NC-23
Both
'
92 2.5 0.0097 ~T;7
92 0 " _
85 0
85 7.5 0.0293 19.2
85 3.8 0.04 22
86 0 _ '
86 0.7 0.003 0,6
• 86 0.1 0.0009 0.3
87 0
87 0 - _
87 0.1 0.0009 0.3
ae o ,-'_'i
B8 5.7 0.0046 25.9
88 0 -
89 0 - _
89 7.8 0.003 2.3
89 0
90 0
90 10.3 0.003 4.8
90 0 - ' _ '
91 0 - _
91 13.9 0.003 13.1
91 0
92 0 - _ .
92 11 0.003 13.4
92 0 -
85 3.8 0.06
65 10 0.0242 30
85 14.1 0.04 34
86 0 ^
86 0.6 0.003 0.9
86 0
87 0 -
87 0 -
87 0
88 0
— — — — - '-
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
57
-------
Segment
CBS
CBS
C85
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
'CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CBS
CB5
Laboratory
CRL/CBL
' CRL/CBL
CRL/CBL
CRL/CBL
CRL/CBL
CRL/CBL
CRUC8L
CRL/CBL
CRL/CBL
CRL/CBL
CRL/CBL
CRL/CBL
CRL/CBL •
CRL/CBL
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
Parameter
NH*"
N023
Both
NH4
NOaa
Both '
NH4
NOzj
Both
NH4
NOaa
Both
NH4
NOM
Both
NH4
NOJ3
.Both
NH4
NC-23
Both
NH4
N023
Both
NH4
N023
Both
NH4
NOag
Both
NH4
N023
Both
NH4
N023
Both
Year
88
88
89
89
89
90
SO
90
91
91
91
92
92
92
85
85
as
83
86
86
87
87
87*
88
88
88
89
89
89
90
90
90
91
91
91
92
%BDL
14.7
0
0
15.9
0
0
13.8
0
0
20.6
0
0
14.7
0
22.3
25.9
33.1
18.1
35.7
16.6
8.1
12.1
31.8
4.2
12.2
9.5
6.5
28.8
1.6
5.6
36.3
6.1
7.9
9.6
14.7
5
Mean MDL
0.0043
-
-
0.003
-
— •
0.003
--
-
0.003
_
0.003
-
0.0397
0.0198
0.0199
0.0418
0.0215
0.0198
0.0254
0.0155
0.0104
0.0161
0.0133
0.0033
0.0121
0.012
0.0021
0.0075
0.0094
0.0024
0.0045
0.0038
0.0024
0,0046
% o» DIN .$1
22 ,£>
:!
•
• 1
5.2 •%
—
_
11.2
.-.
—
20.7
-
_ •
r 22.8
-
— .
19.1
.22.8
—
13
26.7
-
14.7
21.2
-
53.5
9.6
-
23
7.2
-
23.5
19.9
— "
8
24.5
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
• fc
I*
— —
^Segment Laboratory Parameter Year %BDL MeanMOL % of DIN
CBS
CBS
CBS
CB6
C86
CBS
. CB6
CB6
CB6
CB6
CBS
CBS
CB6
CB6
CB6
CB6
CB6
CB6
CB6
CB6
4 CB6
CB6
CBS
CB6
CB6
CB6
CB7
C87
CB?
CB7
CB7
CB7
CB7
CB7
CB7
CB7
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VJMS
VIMS
VIMS
VIMS
.VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
NH4
NOa
Both
NH4
NOss
Both
NH4
NOzg
Both
NH4
NO*,
. . Both
NH4
NO^
both
NH4
NOa
Both
NH4
N023
Bolh
NH4
H023
Both
NH4
N023
Both
NH4
N023
Both
NH4
N023
Bolh
NH4
N023
Both
_
92
92
85
85
85
86
86
86
87
87
• 87
88
88
88
89
89
89
90
90
90
91
91
91
92
92
92
85
85
85
86
86
86
87
87
87
88
16.7
6.7
28.9
24.5
29.6
16.8
33.5
19.2
8,8
11.3
36.8
6,3
10
- 14.3
9
28,1
2
19.6
28.4
3.5
8.7
11.1
11.8
7
25.5
8
28.4
23.3
31.5
16.3
32.9
20.8
10.8
9.2
39.6
6.8
•™™— •••*—__ _*„
0.0039
0.0023
0.04
0.0193
0.0199
0.042
0.0215
0.0198
0.0212
0.0119
0.0112
0.0162
0.0124
0.0047
0.0121
•0.0121
0.0021
0.0102
0.0096
0.0024
0.005
0.0038
0.0024
0.0046
0.0039
0.0023
0.0398
0.0197
0.02
0.0415
0.0215
0.0199
0,0202
0.0147
0.0106
0.0183
31J2 '
31.2
25
29
14.9
26.6
12.8
24.5
r. _i
56.1
16
26.2
8.1
36.2
22
9.6
28.7
43.6
34.6
27.4
25.2
18.5
30 "
25.5
21.5
Trends rn Phosphorus, Nitrogen, and Dissolved Oxygen. 1984 to 1992
59
-------
Segment
CB7
CB7
CB7
CB7
CB7
C87
C87
CB7
CB7
C87
C87
C87
CB7
CB7
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3
EE3 .
EE3
EE3
EE3 .
EE3
Laboratory
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VJMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
Parameter
NH4
NOag
Both
NH4
NOJ3
Both
NH4
N023
Both
NH4
N023
Both
NH4
NOja
ooth
NH4
N023
Both
NH4
NOjg
Both
NH4
NO*)
Both
NH4
NOa
Both
NH4
N023
Both
NH4
NOag
Both
NH4
N023
Both
Year
88
88
89
89
89
90
90
90
91
91
91
92
92
92
85
85
85
86
86
86
87
87
87
88
88
88
89
89
89
90
90
90
91
91
91
92
% BDL
10.5
16.4
7.2
31.4
0.9
14.4
28.2
4.2
9.3
7.4
9.3
7.4
25.9
8.3
37.1
5.7
25.7
21.1
44.7
2.6
7.7
2.6
43,6
2.8
13.9
19.4
13.5
27
0
19.4
36.1
5.6
11.1
11.1
25
13.9
Mean MDL
0.0129
0.0068
0.0122
0.0121
0.0021
0.0103
0.0092
0:0023
0,0053
0.0036
0.0024
0.0045
0.0039
0.0023
0.0398
0.02
0.02
0.0407
0.0214
0.021
0.02
0.021
0^0099
0.023
0.013
0.0054
0.0126
0.0121
.
0.0105
0.0095
0.0024
0.0049
0.004
0.0024
0.0045
% of DIN --.*r^
67.9 -$$8
20.4 - 'fl
' V
37.3 ^
8-1 --^
-
45 - $
12.9
,,£
9.1' • -J
.27,6
.-
r 48.2 •'
40.5
-
30.8
28
-
23.1
28
-
21.2
26.6
-
77.2
18.9
-
50.4
-
-
50.3
22.1
-
5
28.5
~"
60
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 19&4 to
-------
— ' .
Segment
EE3
EE3
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
WE4
CB6
CB6
CB6
CB6
CB6
CB6
CB6
CB6
CB6
CB6
Laboratory
VIMS
. VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS .
VIMS "
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
VIMS
• VIMS
VIMS
VIMS
VIMS
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
Parameter
NH4
N023
Bolh
NH4
NOjg
Both
NH4
. KOja
Both
NH4
MOgg
Both
NH4
NCfe
Both
NH4
NOjja
Bolh
NH4
NOz,
Both
NH4
NOra
Both
NH4
N023
Both
NH4
N023
Both
NH4
NOjg
Both
NH<
NOjg
Both
Year
92
92
85
85
85
86
86
86
87
87
87
88
88
88
89
89
89
90
90'
90
91 .
91
91
92
92
92
85
85
85
86
86
86
87
87
87
83
%BDL
11.1
11.1
5S.7
0.1
19.5
29.5
32.5
15.1
18.9
5
44
12.1
2.8
21.5
10.8
31.8
4.7
33.3
16.7
14.6
16.7
7.6
20.1
5.6
22.9
12.5
20.8
14.6
47.9
10
3.3
18.3
33.8
5.6
19.7
22.9
MeanMDL
0.004
0.0024
0.0397
0.02
0.02
0.0412
0.022
0.0198
0.0236
. 0.0124
0.01
0.0226
0.0129
0.0073
0.0124
0.0124
0.0021
0.0113
0.01
0.0023
0.0052
0.004
0.0024
0.0045
0.0039
0.0022
0.0174
0.01
0,01
.0.0106
0.0056
0.0064
0.0106
0.0056
0.005
0,0101
\
% Of DIN
62.6
40,5
' .
39.1
31.1
30
29.3
_
27.7
24.3
r. —
79.6
21
48.4
12:1
_
62.3
16.2
_
14.2
24.3
60.1
29.3
24.6
28.1
6
24.7"
_
36.8
17.2
—
aa^-rl^'-'-waJj*
ll
1
v
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen. 1984 to 1992
61
-------
\
v
Segment
CB6
CB6
C86
CB6
CB6
CB6
CB6
CB6
CBS
CBS
CB6
CB6
CB6
CB6
CB7
CB7
C87
CB7
CB7
CB7
C87
CB7
CB7
CB7
CB7
CB7
CB7
CB7
.CB7
CB7
CB7
CB7
CB7
CB7
CB7
CB7
Laboratory
ODU
ODU
ODU
ODU
OOU
OOU
ODU
ODU
OOU
ODU
ODU
ODU
ODU
ODU
OOU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
OOU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
Parameter
NH4
' N023
Both .
NH4
NOjjg
Both
NH4
NOjjjj
Both
NH4
N023
Both
"NH4
NOja
Both
NH4
N02a
Both
NH4
NO^
Both
NH4 .
NOsg
Both
NH4
N023
Both
NH4
N023
Both
NH4
N023
Both
NH
HC-,
Both
Year
88
88
89
89
89
90
90
90
91
91
91
92
92
92
85
85
85
86
86
86
87
87
87
88
88
88
89
39
89
90
90
90
91
91
91
92
% SDL
7.1
22.9
8
10.7
6.7
20.8
22.2
4.2
6.9
. 22.2
0
34.4
21.9
4.7
.35.4
10.8
36.9
20.4
4.1
30.6
45.4
4.6
23.7 .
29.1
4.1
37.2
18.4
10.5
18.4
31.3
23.6
14.6
16.7
22.2
6.3
44. 4
Mean MDL
0.0056
0.0039
0.0081
0.0056
0.0025
0.0081
0.0056
0.0025
0.0081
0.0056
*-
0.0081
0.0056
0.0025
0.0172
0.01
0.01
0.0118
0.0056
0.0062
0.0106
0.0056
0.005
0.01
0.0056
0.004
0.0081
0.0056
0.0025
0.0081
0.0056
0.0025
0.0081
0,0056
0.0025
0.0081
% of DIN ura 4|l3l
48.1 '^sir ^1H
23.3 V ^
«**
28.6 '-11
19.8 "S
„«**
38.1 , •,-iKjj£
26.8 {-f
. --T
*•' . ', -'"tgK
" • 'I ^££^™
' "^/jjw
. .- = •"•"«
;;f
" 38-3 :r.
17 -
. __ ' ' *„
26.6
33.3
—
6.9
28.1
33
24.8
_
56.1
21.8
_
46.1
15.3
_
48.6
17.1
_
26.4
19.7
•"
62
Trends in Phosphorus. Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
Segment Laboratory Parameter Year %BDL M^snMDL %oJDJN
CB7
CB7
C88
CBS
C88
CB8
CBS
CB8
CBS
CB8
CBB '
CBS
CBS
CBS
CB8-
CB8
CB8
CB8
CB8
CBB
CBS .
CB8
CB8
CB8
CB8
CB8
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU '
ODU
ODU
-ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
ODU
NH4
NOs
Bom
NH4
NOza
Both
NH4
N023
.Both
NH4
NOaa
• Both
NH4
N023
Both
NH4
NOjB
Both
. NH4
NOzj
Both
NH4
N023
Both
NH4
N0j,3
9?
S2
65
85
85
86
86
86
87
87
87
88
86
88
89
89
89
90
90
90
91
91
91
92
92
92
22.3
9
29.7
4.2
36.8
It, 3
4
26,8
29.8
3.7
28.6
.25.9
3,2
33
13.8
4.2
12.2
19.1
19.1
9.6
13.3
16.7
6.1
39.9
12.9
5.6
O.OC56
0.0025
0.018
0.0094
0.01
0.0113
0.0056
0.0059
0.0106
0.0056
•0.005
0.0103
0.0056
0.0042
0.0081
0.0056
0.0025
0.0081
0.0056
0.0025
0.0081
0.0056
0.0025
0.0081
0.0056
. 0.0025
55.3
19.6
—
33.6
37.9
-
13.8
23
-
38.5
28.3
—
r56.1
25.5'
_
40.4
15.7.
_
50
19
—
32.9 •
17.2
— .
53
18.6
Trends in Phosphorus, Nitrogen, and Dissolved Oxygen, 1984 to 1992
-------
------- |