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Sediment core chemistry data summary from the MQR Mound, August and December 1991 online

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MQR PAH results were compared with recently analyzed data from three other
capped CLIS mounds (Section 4.3). Except for the two specific samples mentioned above,
all PAH concentrations are within the range of samples identified in other CLIS mounds as
remnant capped material (from Stamford and Black Rock Harbors). These results are
discussed further below (Section 4.3).

3.3.4 Volatile Organic Results

The only detected VOCs were acetone, methylene chloride, carbon disulfide, 2-
butanone, and 2-hexanone (Table 3-5). Several of these detections were actually below the
practical quantitation limit and reported as estimated, including all detections of 2-butanone
and 2-hexanone. The relative detections of acetone, carbon disulfide, and methylene chloride
in each of the five samples are similar (volatile ratios). All of these are common laboratory
reagents, yet the method blank contained no detections of these compounds, suggesting that
laboratory contamination was not a factor.

The possibility of field contamination for these three compounds is remote as the
solvents used for cleaning sampling tools were methanol and isopropanol. The remaining
possibility is that the detections of these compounds are indicative of actual sediment
concentrations. Considering the volatile nature of these organic compounds, and the
variation in concentration in the five adjacent surface sediments, this possibility also seems
unlikely.



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



42



Table 3-5



Volatile Organic Results



Compound


mqri-ctr~mT


JR2-CTR Mi


2R3-CTR ]


v!QR4-CTR


MQR5-CTR




(ppb)


(ppb)


(ppb)


(ppb)


(ppb)


Chloromethane


<15


<16


<14


10


<3J


Vinyl chloride


<15


<16


<14


<12


<22


Bromomethane


<15


<16


<14


<12


<22


Chloroethane


<15


<16


<14


<12


<22


1,1-Dichloroethene


<6.1


<6.6


<5.5


<4.8


<8.9


Acetone


751 U


203 J


1144 U


908 U


254 J


Carbon disulfide


16


<6.6


119


53


<8.9


Methylene chloride


44


6.6 J


25


20


12 J


trans- 1 ,2-Dichloroethene


<6.1


<6.6


<5.5


<4.8


<8.9


1,1-Dichloroethane


<6.1


<6.6


<5.5


<4.8


<8.9


cis- 1 ,2-Dichloroethene


<6.1


<6.6


<5.5


<4.8


<8.9


2-Butanone


<92


99 J


163 J


<73


<134


Chloroform


<6.1


<6.6


<5.5


<4.8


<8.9


1,1, 1-Trichloroethane


<6.1


<6.6


<5.5


<4.8


<8.9


Carbon tetrachloride


<6.1


<6.6


<5.5


<4.8


<8.9


Benzene


<6.1


<6.6


<5.5


<4.8


<8.9


1 ,2-Dichloroethane


<6.1


<6.6


<5.5


<4.8


<8.9


Trichloroethene


<6.1


<6.6


<5.5


<4.8


<8.9


1 ,2-Dichloropropane


<6.1


<6.6


<5.5


<4.8


<8.9


Bromodichloromethane


<6.1


<6.6


<5.5


<4.8


<8.9


4-Methyl-2-pentanone


<61


<66


<55


<48


<89


cis- 1 , 3-Dichloropropene


<6.1


<6.6


<5.5


<4.8


<8.9


Toluene


<6.1


<6.6


<5.5


<4.8


<8.9


trans- 1 , 3-Dichloropropene


<6.1


<6.6


<5.5


<4.8


<8.9


1,1,2-Trichloroethane


<6.1


<6.6


<5.5


<4.8


<8.9


Tetrachloroethene


<6.1


<6.6


<5.5


<4.8


<8.9


2-Hexanone


<61


66 J


<55


<48


<89


Dibromochloromethane


<6.1


<6.6


<5.5


<4.8


<8.9


Chlorobenzene


<6.1


<6.6


<5.5


<4.8


<8.9


Ethylbenzene


<6.1


<6.6


<5.5


<4.8


<8.9


m/p Xylene


<6.1


<6.6


<5.5


<4.8


<8.9


o-xylene


<6.1


<6.6


<5.5


<4.8


<8.9


Styrene


<6.1


<6.6


<5.5


<4.8


<8.9


Bromoform


<6.1


<6.6


<5.5


<4.8


<8.9


1 , 1 ,2,2-Tetrachloroethane


<6.1


<6.6


<5.5


<4.8


<8.9



Samples were collected from surface grabs on 12/17/91.

Qualifier codes:

J = Estimated value; analyte detected at < the practical quantitation limit.

U = Above the upper calibration limit.



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



43

4.0 DISCUSSION

The original hypothesis of this study was that the slow recolonization rates
documented by REMOTS® photographs, and the bioassay results, were due to a surface layer
remnant of the 3,000 m 3 of Black Rock material which was disposed of last in the MQR
depositional sequence. The coring data were used to construct a stratigraphic sequence to
test this hypothesis by identifying New Haven, Black Rock, Mill River, and Quinnipiac River
materials. These stratigraphic units were identified by (1) estimating the thickness of each
material disposed; (2) comparing the core sample metals data with historical metals data
collected from each source area; and (3) evaluating the organic contaminant data on the basis
of more recent sediments also collected from capped mounds at CLIS.

Core descriptions indicated that the top 1-1.5 meters of each core recovered relatively
homogenous material. In order to identify whether a thickness of over 1 meter of a similar
material was realistic, the thicknesses of each dredged material unit were estimated using the
DAMOS Capping Model. Results of the model also were compared with bathymetric depth-
difference volume maps between successive depositional intervals. These volume estimates
were used as a first-order prediction of thicknesses of individual units recovered in the cores
(Section 4.1).

Historical metals data from the source areas (Mill and Quinnipiac Rivers, Black Rock
and New Haven Harbors), and from the MQR mound itself, were compared with the MQR
core data in order to identify the origin of individual samples in the MQR cores (Section
4.2). If successful, these comparisons would allow a stratigraphic correlation of the cores,
and potentially allow identification of the source of the surficial sediments causing the
retrograde benthic faunal conditions at MQR.

Finally, chemistry results indicated that several samples, specifically MQR-3F, and
MQR-5E, contained distinctively elevated levels of organic contaminants. The suite of
organic contaminant data from the MQR cores was compared with recent coring results from
other CLIS capped mounds to further elucidate the source areas for each MQR sample
(Section 4.3). These data were also analyzed in light of the current knowledge of
bioaccumulation potential and resulting negative effects.

4.1 Volume Estimates of MQR Source Materials

The DAMOS Capping Model, a computer program developed for NED that predicts
the thicknesses of disposed dredged material, was used to estimate the volumes of each of the
different source materials at MQR. These estimates do not consider postdepositional settling
of the mound sediments. The model allows for a dual-phase depositional scenario; since
MQR was actually completed in at least 4 phases, several runs were completed. Thicknesses
were estimated over a predicted 150 m radius of operations, unless otherwise stated. The

Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



44

value used for the volume of a single barge load was 2000 m 3 , and the grain size distribution
was kept constant at 20% sand, 40% silt, and 40% clay, with a density of 1.45 g/cc.

The Capping Model predicted that 1-3 m of Quinnipiac River material (190,000 m 3 )
would overlie a base of 0.5-2 m of Mill River material (70,000 m 3 ). Bathymetric analyses
following deposition of Mill River sediments (April 1982) generally agreed with the modelled
results. Two bathymetric surveys were conducted following deposition of Quinnipiac River
sediments and before New Haven/Black Rock Harbor deposition, in June 1982 and
December 1982. Bathymetric results from the June 1982 survey indicated that the
Quinnipiac sediment layer was thinner ( < 1 m) than predicted by the Capping Model,
assuming no consolidation of Mill River sediments. The December survey, however,
indicated that both Mill and Quinnipiac River sediments had settled approximately 0.5 m in
the period between June and December, suggesting a maximum total consolidation of Mill
and Quinnipiac River sediments from bathymetric estimates of approximately 2 m.

Modelling the disposal of point-dumped (operational radius of 50 m) Black Rock
Harbor sediments (67,000 m 3 ) following the combined disposal of Mill and Quinnipiac River
sediments (260,000 m 3 ) resulted in a thickness of Black Rock sediments of 2-4 m. No
bathymetric survey was conducted following deposition of Black Rock Harbor material. In
addition, the Capping Model was used to predict the thickness of a 3,000 m 3 layer of Black
Rock material deposited following final capping of New Haven material. The result was that
the hypothetical thin layer of Black Rock was indistinguishable from the huge mound of
material below it.

New Haven Harbor sediments were disposed not as a taut-wired point-dumping
operation, but rather as a widely distributed LORAN-C controlled disposal operation for
more comprehensive coverage of cap material. Ten disposal points were concentrically
arranged, one in the center, three at 80 m, and six at 120 m from the center. The Capping
Model predicted a thickness range of 1.5-3.5 m of New Haven sediments (400,000 m 3 )
overlying the cumulative sum of the other units within a 300 m radius of operations.
Bathymetric observations, obtained after deposition of both Black Rock and New Haven
sediments (June 1983), resulted in a minimum total post-Mill and Quinnipiac River sediment
thickness of 1-2 m (again assuming no postdepositional settling). These results are consistent
with a New Haven cap of 1.5 meters recovered in the cores. The recovery of ambient
material below this interval in MQR-6, however, indicates that at least this core was
recovered from the mound flanks, where the total thickness of dredged material is thinner
than at the center of the mound.

The differences in the modelled thicknesses and those measured by bathymetric
volume-difference analyses are a function of sediment consolidation and the diameter of
disposal operations. Much of the material is dispersed in the flanks around the mound and is



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



45_

not detectable by use of bathymetric methods. The use of different types of methods to
calculate dredged material volumes are currently under investigation (Murray 1994).

4.2 Metal Ratios of MQR Source Materials

Trace metal data from the four sources of dredged material present at the MQR
mound, in addition to historical CLIS reference station data, were compiled. Zinc, Cu, and
Cd concentrations were plotted for each source (Figure 4-1). The few samples from the Mill
and Quinnipiac Rivers (n=10 and 6, respectively) reduce the statistical significance of the
frequency distributions; however, some trends are worth noting. In general, higher Zn and
Cu concentrations were present in Mill River sediments, while higher Cd concentrations were
measured in Quinnipiac River sediments (Figure 4-1). Black Rock Harbor sediments had,
overall, the highest concentrations of all three metals (Figure 4-2). New Haven Harbor
sediments were generally low in all three metals relative to the other source areas; however,
some of the New Haven samples still had 10 times the trace metal concentrations of CLIS
reference station samples (Figure 4-3).

Sediment samples were taken and analyzed for trace metals at the completion of each
phase of formation of the MQR mound (Morton et al. 1984b). Results confirmed that Cd
concentrations of Quinnipiac River sediments were higher than those of Mill River (Figure 4-
4). Chemistry samples taken at the surface of the MQR mound following deposition of
Black Rock/New Haven Harbor sediments have indicated fairly stable and relatively low
trace metal concentrations since final cap deposition (Figure 4-4).

Most of the trace metal concentrations of the MQR core samples fell within upper
New Haven/lower Quinnipiac Zn and Cu concentration ranges (Figure 4-5, A, B). The
distribution of New Haven Harbor, Mill River, and Quinnipiac River Zn and Cu
concentrations overlapped, probably since some of the sediment from the two rivers are
transported to, and settle into, the New Haven Harbor. Two theoretical "mixing lines"
established the separation of Black Rock Harbor from the other sources, primarily due to the
excess of Cu in Black Rock Harbor sediments (Figure 4-5, A).

The high Cu concentration in Black Rock sediments has been noted since the original
Black Rock Harbor results were reported, and were confirmed in the recent coring operations
at three other CLIS capped mounds (SAIC 1994). The three mounds cored were Stamford-
New Haven North (STNH-N), Stamford-New Haven South (STNH-S), and Cap Site 2 (CS-
2). Results from these cores showed that many of the samples taken from the mounds fell
into New Haven Harbor concentration ranges and were classified as being capping material
(Figure 4-6). STNH-N and STNH-S received contaminated material to be capped from
Stamford Harbor, whereas CS-2 received material from Black Rock Harbor at the same time
as MQR. Samples from these three capped mounds reflected these two source areas when
compared with the original data collected at the time of disposal (Figure 4-6).



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



46



Mill River



c
d)
o
c
o
O



>3000
2500-3000
2000-2500
1500-2000
1000-1500


N=10




i


800-1000






600-800




400-600


i ■ i








<400




1 1 1 1 —



20 40 60 80

Percent of Samples



100



□ Zn



iCu



□ Cd(x100)



E

Q.

a.

c
o



c

0)

o

c
o

o



Quinnipiac River



>3000
2500-3000 "
2000-2500


N=6




i


1500-2000






!


1000-1500






> -.' •;- ' &.»,:.(


800-1 000








600-800






I


400-600






<400




i i



20 40 60 80

Percent of Samples



100



□ Zn



iCu



OCd(x100)



Figure 4-1. Trace metal (Zn, Cu, Cd) concentration frequency distributions of samples
from the Mill and Quinnipiac Rivers



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



47



Black Rock Harbor



>3000
2500-3000




20 40 60 80

Percent of Samples



100



□ Zn



jCu



|Cd(x100)



New Haven Harbor



E

Q.

tz
o



c
CD
O

c
o
O



>3000
2500-3000 "
2000-2500
1500-2000 '
1000-1500 '
800-1000




N=20 (Zn.Cu)
N=5 (Cd)


600-800


~n






400-600


m ~n


<400






i



20 40 60 80

Percent of Samples



100



□ Zn



iCu



|Cd(x100)



Figure 4-2. Trace metal (Zn, Cu, Cd) concentration frequency distributions of samples
from the Black Rock and New Haven Harbors



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



48



CLIS REF: 1979-1985



>300

§. 250-300

Q.

^ 200-250

o

'■JS 150-200


]
3

P




N=94 (Zn, Cu)
N=52 (Cd)


tZ


'


§j 100-150


a










i


§ 50-100


g||i










wmw


^/////////////////M


<50







20 40 60 80

Percent of Samples



100



□ Zn



iCu



|Cd(x100)



Figure 4-3. Trace metal (Zn, Cu, Cd) concentration frequency distribution of samples
from the CLIS Reference Station (CLIS REF), cumulated over the years
1979-1985



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



49



(aidd) po
in o




o oo



<



CD
00



CO



O

c
N



CD



^ <o


3





E


«L >»


"D


£ 0)


CD




O


CO


<




l_


CO
00




Q.
Q.


~3


O

o



D



00
i

O ©



(wdd) uz pue no



■a

3
O

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C 1/3



s

00



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



50



3500 -























3000












2500 -






Zm u







|2000 -

Q.

3 1500 -
O

1000 -
500

n „




|es^i


m

.•' -

■ ■""■■










200


400


600 800 1000
Zn (ppm)


1200



B



1000
800

£ 600

Q.

a.
200



d- nc ?t>



\m :



200



400 600 800

Zn (ppm)



1000



1200



Black Rock + New Haven
Quinnipiac □ MQR Cores



Mill River



Figure 4-5. Zinc and Cu concentrations of MQR sources and core samples: (A) Two lines
are estimated slopes for Black Rock (top) and New Haven/Mill/Quinnipiac
(bottom) materials; (B) Enlargement of above showing distribution of lower
copper values.



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



51



Black Rock Harbor









Stamford Harbor^.'cj]
x



x A.



x



New Haven Harbor
Capping Material
(approximate region)



400 600 800
Zn (ppm)



1000 1200



+ New Haven ■ Black Rock
x STNH-N Cores * CS-2 Cores



a Stamford

n STNH-S Cores



Figure 4-6. Results from the first CLIS coring operations as compared to historical data.
Capping material for all mounds was derived from New Haven Harbor.
Capped material was derived from Stamford Harbor (STNH-N, STNH-S) and
Black Rock Harbor (CS-2).



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



52

Metal ratios were compared by normalizing both Cd and Zn data to Cu, resulting in
relatively discrete fields for each of the MQR source areas (Figure 4-7, A). Cd/Cu and
Zn/Cu Black Rock Harbor metal ratios were minimized and concentrated in a field due to
high Cu concentrations. Quinnipiac and Mill River sediments were separated because of the
relatively higher Cd concentration of Quinnipiac sediments. New Haven sediments fell in a
field between Mill River and Quinnipiac sediments, as predicted according to the discussion
above (Figure 4-7, A).

All of the MQR core samples fell within a field dominated by New Haven and Mill
River sediments (Figure 4-7, B). Considering trace metal concentrations alone, the results
indicated that no samples representative of remnant Black Rock Harbor sediments were taken
from the MQR cores. If any Black Rock Harbor material was sampled, it was either not
representative of average Black Rock Harbor material, or in such a thin layer that it was
diluted by sediment originating from somewhere else. These results also suggested that most
of the MQR core samples could be remnant New Haven Harbor capping material. These
results do not exclude the possibility that unmeasured contaminants (e.g., PAHs) contributed
to the biological disturbance.

4.3 Organic Contamination of MQR Sediments

Core descriptions and grain size data were available for all six cores recovered.
These data indicated that only MQR1 and MQR6 recovered potential ambient material. PAH
results from MQR6-E were consistent with this conclusion as the base sample decreases to
low PAH levels relative to the sample above (Figures 3-8 and 3-9). Interpreting organic
contaminant results from the MQR mound was hampered by the paucity of historical data.
Analytical methods have been modified, and detection limits improved, over the past ten
years. Due to the lack of historical organic data, MQR core samples were compared with
the more recent CLIS coring results.

Two PAH compounds were plotted against each other from the four CLIS mounds
(Figure 4-8). These results indicated that most of the MQR samples have PAH
concentrations comparable to sediments classified as remnant Black Rock and Stamford
Harbor, except for MQR-3F and MQR-5E. These two samples had exponentially higher
PAH concentrations relative to the rest of the samples (Figure 4-8). MQR-5E was also the
sample with the excessively high PCB value (31 ppm).

Most significantly, all of the MQR PAH concentrations were higher than the majority
of samples classified as capping material in the other CLIS mounds. Plotting pyrene at the
same scale in the three cored capped mounds, concentrations approached zero in the top 50-
100 cm of STNH-N and CS-2, while the average of the MQR pyrene concentrations was
approximately 2 ppm in the same depth interval of MQR cores (Figure 4-9). The decrease



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



53



0.07
0.06-
0.05
g 0.04
8 0.03-
0.02-
0.01




0.5



MQR Con Data Region
(below)



1 1.5

Zn/Cu



Z5



A. Black Rock * New Haven
° Mill River ■ Quinnipiac



B



y aoi6-



■CJuinrepnc flVof" FiaU






-to mH mnntMxkigUn*



IMRtafFMd



1.2 1.4 1.6 li 2 22 24 26

Zti/Cu

a MQR2 A. MQR3 * MQR5 ■ MQR6



Figure 4-7. Zinc and Cd concentrations normalized to Cu for (A) MQR source areas and
(B) MQR core samples. Dashed line separates Mill and Quinnipiac River
fields, and follows the range of New Haven samples. MQR samples are
clustered along this New Haven axis.



Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



54



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Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



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Sediment Core Chemistry Data Summary from the MQR Mound, August and December 1991



56

of PAH in the base sample of MQR6 was consistent with the visual interpretation of the
recovery of basement material.

PAH concentrations in MQR core samples were compared with previously measured
PAH data. The average value of pyrene of 2 ppm was lower than the recently measured
average value in New Bedford Harbor sediments (3.5 ppm; Pruell et al. 1990), and higher
than the average measured at the surface of the Mud Dump Site in New York (0.98 ppm;
Charles and Muramoto 1991).

Because of the lack of historical organic contaminant data, a "contaminant stratigraphy"
of the MQR cores cannot be assembled. However, the PAH data do indicate that much of the
entire dredged material mound at MQR has relatively high PAH concentrations, and discrete
intervals of very high PCB concentrations. Because of the estimated thicknesses of New
Haven sediment, the cores should consist of at least one meter of New Haven material.
Organic data suggest two alternative conclusions: (1) PAH concentrations are indicative of the
original concentrations of New Haven Harbor capping material at the time of disposal, or (2)
PAHs have remobilized from the capped materials and infiltrated the capping material.

Two points are important to note in order to draw the most reasonable conclusion.
Although PAHs are readily adsorbed onto particulate matter, biodegradation and oxidation
may occur in the sediment column (e.g., Kennish 1992). There is no current evidence,
however, to support the organic contaminant flux scenario, and in previous CLIS cores,
capping material remained relatively low in contaminant constituents (SAIC 1994). Secondly,
the samples with high PAH and PCB concentrations lie in the Mill and Quinnipiac River
fields, as defined by metals ratios. Considering that both the Mill and the Quinnipiac Rivers


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