TOXICITY IN A HEAVY METALS by yhz16267

VIEWS: 54 PAGES: 89

									            AN EXPERIMENTAL STUDY

I
          OF ACID VOLATILE SULFIDES

1
    PREDICTING TOXICITY I A HEAVY METALS
                         N
    CONTAMINATED WETLAND ENVIRONMENT



                     MASTER'S THESIS
                      AUGUST, 1993




    SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
     DEGREE OF MASTER'S OF SCIENCE IN ENVIRONMENTAL ENGINEERING
                MANHATTAN COLLEGE, RIVERDALE, NEW YORK




                          BY
                    BRADLEY L.SIMMONS




                      THESIS ADVISOR
                    DR.JOHN D.MAHONY
                      INTRODUCTION


    The   Environmental    Protection   Agency   (EPA)   is   currently

developing sediment quality criteria (SQC) for contaminants that
associate with both fresh and marine water sediments and are toxic

to those sediment dwelling and sediment dependent organisms.
    One basis for establishing SQC uses equilibrium partitioning
between the sediment and pore water phases in a sediment. This is
a viable approach because it deals with varying bioavailability and

toxicity affects of chemicals in sediments (Di Toro, 1991). It is
known that   the aqueous    free metal    (Cd2+, Cu2*, etc.)    is the

bioavailble species for heavy metals.
    12 has been noted (Di Toro, 1990) that there is a reactive pool

of solid phase sulfides available to sorb metals. The majority of

sulfides are in the form of iron sulfide. These iron sulfides

undergo equilibrium reactions with less soluble metal sulfides. The
initial reaction is driven by the equilibrium between iron sulfide

and the pore water sulfide ion:
    Acid volatile sulfide is this solid phase sulfide in the sediment
    which is soluble at room temperature in cold hydrochloric acid. As
    these sulfides are contaminated by heavy metals, non-toxic metal

    sulfides,      because   they   are    generally     less   soluble,    will

    precipitate:


                         Me2+ + FeS(s)       --->     MeS + Fe2+,



    where Me2+ is Cd2+, Ni2+, C ” .
                               u,     etc.



          Metals   extracted   during     the   AVS     procedure   are    termed
    simultaneously extracted metals (SEM). The AVS theory predicts that

    for a molar ratio of SEM/AVS < 1, no toxicity exists, and for

    SEM/AVS > 1, there is a potential for toxicity.
          In this study the AVS theory will be put to test using a heavy

    metal contaminated site, Foundry Cove, to exhibit how this unique
i
i
    AVS   -   SEM relationship is useful in determining if toxicity is
    potential.     Vertical sections of sediment core samples will be
1
    analysed to determine variability of AVS and the extent to which

    the potential for toxicity exists. It will be clearly understand
    how this theory is a functional tool for the determination of
    sediment quality criteria.




                                          1-2
                                             I1
                                HISTORY OF FOUNDRY COVE


             Foundry cove is located approximately fifty miles north of New
         York City on the eastern shore of the Hudson River in Cold Spring,
  ,
         New York. The cove is primarily fresh water supplied by Foundry
         Brook and contains a tidal marsh. An iron foundry from the Civil
         War era is how the name originated, and the structure still exists.
             From 1953 to 1978 Marathon Battery operated a nickel cadmium
         battery plant located a few hundred meters north of the cove (fig.
         3-1). The operation of this plant resulted in the contamination of

         the cove and marsh areas with nickel, cadmium, and cobalt. The
. 1.     plant was built by the U.S. Army Corps of Engineers for production
         of batteries for various uses for the armed services.
     i
             The process used in producing the batteries required the use of
     1   concentrated metal nitrate solutions and resulted in dilute waste
_.

         solutions   and   precipitates     of   the metals   involved.    caustic
         solutions containing cadmium, nickel, and cobalt were regularly
         discharged through an outlet pipe to the marsh. Equipment to remove
         solids was installed at the plant in 1970, and in 1971, the plant
         was required to meet the state standards for discharge of 0.2 mg
         cadmium/l. in 1972-73, partial dredging of the outfall area and
         channels    leading   to   the   cove was   completed   to   a   level of
         approximately 1500 mg Cd / kg dry sediments.
    Foundry Cove is presently a Superfund site where a cleanup

project was started in the spring of 1993. A railroad spur line in
being   constructed   to   haul   dredged   sediments,   which   will   be

partially treated at the site, to a hazardous material landfill.

Because of these circumstances the site was unaccessible at the

time of this study.


                              Figure 2-1




                                  2-2
                                      I11
                     ACID VOLATILE SULFIDE THEORY


         In order to quantify the toxicity of metals in sediments and
    the binding capacity for metals of these sediments in an aquatic
    environment and the subsequent bioavailability of those metals, the
    sulfide fraction of sulfides and metal concentrations which are
    removed from the sediment using cold hydrochloric acid is used and
    referred to as acid volatile sulfide (AVS). The metal fraction
    removed is referred to as simultaneously extracted metals (SEM). In
    this study, SEM and metals refer to cadmium, nickel, and cobalt.

    The use of total metal concentration to quantify and predict

    toxicity and bioavailability          is not reliable because different

    sediments exhibit different degrees of toxicity for the same total

    quantity of a metal.

         AVS is a reactive pool of solid phase sulfide           (umol S2-/gdry

    sediment) that is available to bind metals and render them nontoxic
    and unavailable to biota.        It    is this AVS   concentration of a

I
    sediment which establishes the boundary below which metals exhibit
i
    no   toxicity   in   aquatic   sediments.   Once   the AVS    and   SEM   are

    quantified on a umol/g dry basis, one can analyze the ratio of the
I

    two and state for (SEM)/ (AVS) .c 1, no toxicity will be present. For
    (SEM) / (AVS) > 1, the potential for toxicity may exist.



                                    3-1
    Chemically, the key to the AVS theory is solubility. Iron is
the most abundant metal in the earth, and the largest reservoir of
sulfides in sediments is solid phase iron sulfide. Iron sulfide is
more soluble than most all other metal sulfides, including those in

this study. Because of the worldwide abundance of iron and this
unique solubility relationship, iron sulfide has the ability to
sorb other metals and convert them to metal sulfides, rendering
them nontoxic. This can occur in the pore water of sediment layers
like those in         Foundry    Cove.      At    equilibrium,   the sulfide   ion
successfully competes with other dissolved or particle-associated
ligand   for    the    metal    ion    to    form    insoluble   metal   sulfides.

Following are the pertinent chemical equations:



Origination of sulfur:
           O-
          S:    + (CH20)   --->       S” + CO, + H20

Conversion to iron sulfide:

          S2-+ Fe2+ ---> FeS(s) <---> FeS,,             (pyrite)

Conversion to metal sulfide:
          Cd2+ + FeS(s)        --->   CdS + Fe2+




                                            3-2
        AVS is determined by the acid conversion of sediment sulfide to

    hydrogen sulfide and subsequent precipitation of silver sulfide as
    follows:
                FeS(s) + 2'
                          H   ---> H,S(g) + Fe2+

                 2Ag+ + S2- ---> Ag2S(s)

    The AVS (umol S2-/gsediment) is calculated on a dry sediment basis
    as follows:


      AVS   =       -       (Ag,S, 9) *       ug/g)
                    (247.8 ug Ag,S/umol)    * (dry sediment wt, g)



                               ROLE OF CARBON


        Carbon     (humic material)   plays    the role   of   an    additional

    sorption phase. Excess metal does not all go into pore water. A
    significant amount is bound to the humic material               in sediment

    particles.
        It has been found       ( ) that for copper, an additional 7-8
                u'
    micromoles C 2      can be sorbed per gram sediment for a percent

    organic carbon (7-8 umol Cu2+/g dry/ % OC) .

        Percent carbon is determined by carbon-hydrogen-nitrogen (CHN)
    analyses. The carbon from a dried sediment sample is heated and

I   converted to CO,,     then analyzed by infrared spectrometry.          This
1
    determination of carbon content as an additional sorption phase was
    beyond the scope of this study.
                                      3-3
                             IV
              AVS EXPERIMENTAL PROCEDURES


   The analytical objectives of the AVS experiments are to
determine the sulfide and total metal (cadmium, nickel, cobalt)
concentrations extracted from each sediment core slice by the use
of cold hydrochloric acid. The sulfide fraction (AVS) extracted
is quantified on a micro mole sulfur per gram dry sediment basis
(umol S2-/g dry). The simultaneously extracted metals   (SEM) is

quantified on a mg/L basis initially, then converted to umol/g dry

to set the SEM/AVS ratio.
    Sediment cores from 17 sites in Foundry Cove were obtained in

1989 (figure 4-1). The cores were extracted by pushing lengths of

clear plexiglass tubing of 3.5" diameter into the sediment to
depths varying from 5" to 18", depending on the nature of the

sediment or until a hard bottom was hit. The top of the tube was

then capped to create a vacuum and the tube was extracted from

the sediment. The bottom of the tube was then capped and the core
was properly marked and packed vertically in dry ice until it was

transported to a laboratory freezer.

    Upon initiation of analyses, a core was removed from the
freezer and placed under room temperature tap water for two
minutes or until it could be pushed partially out of the tube

surface top end first.


                                 4-1
    Since the AVS train is equipped to analyze 8 samples

simultaneously, 8 slices are made at a time. The tube is placed
horizontally on a lab bench and 8 slices of 6mm each are cut from
the core with the use of a coping saw with a blade of 16 teeth
per inch.
   Approximately 10 grams of each sample is dried in an oven for

at least four hours at 103O C to determine sediment solids

fraction. The percent solids is calculated. as follows:


            % Solids = 100 *   (dry wt, g)   -   (tare wt, g)
                               (wet wt, g)   -   (tare wt, g)


    Approximately 8 to 10 grams of each sample is placed in the

reaction vessel of the AVS train, which will be described next.
    The AVS train is headed by a tank of purified nitrogen gas
which is used to deaerate the entire system for one hour before

commencing the experiment.

    An oxygen stripping tower follows the nitrogen to strip
impurities. The oxygen stripping solution contains approximately

4 grams ammonium vanadate dissolved in 25-30 ml concentrated HC1

and diluted to 250 ml with deionized water. approximately 10

grams of granular zinc are amalgamated with 100 ml of a 0.01M
solution of Mercurous Chloride solution by swirling for 15
minutes. The liquid is decanted and the zinc is rinsed with water
and then added to the Vanadate solution. The mixture will be a
bright blue green until gas is bubbled through it, then it will

turn deep purple.
                               4-2
J
        Following the oxygen stripper is the AVS reaction vessel.
1
1   this is a 500 m l Erlenmeyer flask containing a stirring bar and
    200 ml deionized water placed on a magnetic stirrer. This is

    followed by three 250 ml Erlenmeyer flasks. The first contains
    200 ml of Ph 4 buffer solution of sodium phthalate (Fisher

    Scientific cat #B-79), a chloride trap to prevent chloride carry

    over. The second two contain 200 ml 0.1M Sodium Nitrate (from a

    crystaline form of 1M AgNO,,, to trap HIS as Ag,S precipitate.
        Figure 4-1 illustrates the primary AVS apparatus. All flasks
    were fitted with two holed rubber stoppers with proper glass

    tubing. The airtight system is fitted with Nalgene tubing to

    connect the glass tubing. Eight of these trains were set up in

    series. The gas line was fitted with a rcYeafter the 0 scrubber
                                                          ,

    such that two series of four trains were fed an even gas flow.
I
             Upon deaeration of the system by purging with nitrogen at a
I
         rate of 4 bubbles/s for 1 hour, the 8 reaction vessels
         are unstoppered and the 8-10 g sediment sample is emplaced and
         the stirrer is turned on. Five minutes later 40 ml of 6M HC1 is

         added to the reaction vessels. The time the reaction vessels are
         quickly unstoppered is negligent to the deaeration process. The

         reaction vessels are swirled occasionally during the 1-2 hour
 i

         reaction time when the following reaction occurs:


                          Fes(s) + HC1 ----> H2S + FeCl
                       (chloride trap prevents C1 carryover)




         Following completion of this reaction:




         the silver sulfide precipitates in the last two sulfide traps.
 1

-i           These precipitates are filtered through a Buchner funnel (5"
         diameter) fitted with glass fiber filters (Fisher Scientific #09-
         804-42C). These filters were rinsed with deionized water and oven

         dried on aluminum weighing pans to prevent the added weight of any

         residue. Their post drying weight was used as a tare weight.    Care

     i   was taken to rinse flask, funnel, and filter to insure all
         precipitate was filtered. the filtered precipitate was then oven
         dried at 103O C for 2 hours and weighed.


                                        4-4

     I
    The acid volatile sulfide (umol S/g sediment dry) is calculated as

    follows:



      AVS (umol/g)   =   (Ag,S, g) * (mol S2-/247.8g Ag,S)   *   (lo6 umol/mol)

                             (wet sediment wt, g) * (% solids/100)



        Deionized water for these procedures originated from tap water

    via treatment through a SYBRON-Barnstead megohm-cm system. This
    treatment, by filtration and deionization achieves a resistivity of
    18.3 Mohm-cm. A Denver Instruments model A-160 electronic scale was

    utilized for all weighing.




!




                                         4-5
                                          V
               ATOMIC ABSORPTION SPECTROPHOTOMETRY


i
        Upon    completion   of   each    experiment,   the   reaction   vessel
    discussed in chapter 4 contains the simultaneously extracted metals
    (SEM)     which   are     analyzed     by   flame    atomic       absorption

    spectrophotometry (AAS) for metal content on a part per million
    (
    ppm) bas is.
        Upon completion of the A V S reaction, the reaction vessel is
    covered    and placed    aside to settle overnight.        Upon   settling,

    approximately 40 ml of the supernatant is pipetted off into two

    glass vials. This supplies enough of each sample to check duplicity
    of analytical results obtained from AAS.

        A Perkin Elmer model 3030 atomic absorption spectrophotometer
    equipped with an acetylene and oxygen fueled flame head was used

    for analyses.
        The quantity of interest in atomic absorption analyses is the

    amount of light at the resonant wavelengths which is absorbed as
    the light passes through a cloud of atoms. As the number of atoms

    in the light path increases, the amount of light absorbed increases
    in a predictable way. By measuring the amount of light absorbed, a

    quantitative determination of the amount of analyte element present
    can be made. The use of different light sources in the form of
    hollow cathode lamps for each element to be analyzed, and selection
                                    5-1
of wavelength allow the specific quantitative determination of

individual elements in the presence of others (Beaty, 1978). The
wavelength, slit, energy, detection limits, and amperage used for
each element analyzed can be found in table 5-1.

        Samples drawn from the AVS reaction vessel are introduced into
a flame via a tube attached to the nebulizer.                  The sample is
atomized in the flame in the light path of the hollow cathode lamp
which    emits   light    at   the     element    specific   wavelength.   The

absorption is proportional to the number of atoms in the flame.
    Each sample was analyzed for cadmium, nickel, and cobalt. The
average of five readings for each duplicate sample was recorded in

ppm. Results of these analyses are discussed in a later chapter.
    Since the results of the AAS analyses are recorded in ppm, or

mg/l, they must be converted to umol/g dry in order to be properly
compared to the AVS quantities which are reported as ug/g dry.



                         Table 5-1      .




 Wavelength (nm)                228.8             233.7        242.4
    Slit (nm)                    0.7               0.2          0.2

 Linearity (mg/L)                5.0               6.0          4.0

  Amperage (Ma)                   8                30           25




                                            5-2
    The SEM is calculated as follows:


     SEM   =    (mg/l AAS) *(vol, L)* (1000 umo1/mmo1) * (mmol/molecularwt,mg)
                            (dry wt, g in AVS reaction vessel)



        SEM/AVS ratios can now be quantified in the proper units:
                 (umol metal/q dry) / (umol S/g dry)
    where if (SEM/AVS) > 1, toxicity may be present. Note that SEM's
    for each metal analyzed must be added in order to make the proper
    comparison.
        It is common to quantify the concentration of metals in
    sediments on a mg metals/kg sediment basis, and shall be presented
    this way in this study. Total metals in the sediment can be
    calculated:



i
4
            mg/kq   =   (mq/l*) * (vol, L@) * (1000g/kq) / (dry wt, 9)




    @ denotes total volume in AVS reaction vessel (240 ml water + wet

    wt, g   -   dry wt, 9)
    * denotes total ppm (mg/l) for all metals analyzed
                                          5-3
                                         VI
                          CONTROL EXPERIMENTS


7       In order to prove validity and reliability to the previously
I
    stated methods of experimentation, a series of control experiments
    were run. Results are in table 6-1.
        Initially, a blank experiment was run where no sediment was
    added to the reaction vessel. Residue remaining on the filters

    after   drying      ranged        from     0    to   0.0005g.    These   results   are
    negligible.
        Sediment        for the remaining control experiments was collected
    from Van Cortlandt pond in Van cortlandt Park. The park is located
    in Riverdale, N.Y.      At the time of analyses, the sediment was stored
    in a pickle jar and refrigerated for a number of weeks.


                       Table 6-1


      control
      Experiment
             1
                   I   Mixing
                       status
                        no sed.
                                  I   Avg . AVS
                                      umol/g dry

                                             48.0
                                                            Standard
                                                            Deviation
                                                              6.6

             2          5 min.               94.6             19.5
                        by hand
                        5 min.               75.7             11.9
j
                        by hand
                          not                75.4             11.1
                        mixed
                        IO min.              69.8              6.8
                       by hand
                       15 mi.                59.7              3.7
                       160 rpm
                                               6-1
i



          The second and third control experiments consisted of mixing
1
    the sediment by hand with a spatula for 5 minutes and placing the
    sediment in the same type of plastic tubing used for the Foundry
    Cove cores. The core was then frozen overnight (vertically) and an
    AVS    experiment   was    run    using   the   same   previously   described
1   procedures. The average AVS of 94.6 and 75.7 umol/g, and standard
    deviations of 19.5 and 11.9 indicate great variability (20%). This
    variability could be do to settling and lack of complete
    mixing before the core is actually frozen.             To see if this was the
    case, the remaining three control experiments were run without
    freezing the sediment in cores. The sediment was simply weighed and
    placed in the AVS reaction vessel.
          The fourth control experiment was run using sediment which was

    not well mixed. An average AVS of 75.4ug/g and standard deviation
i
    of    11.1   resulted.    These   are nearly    identical    results   as   the

    previous experiment.
1         The sediment was well mixed by hand for 15 minutes for the next
J   experiment. The resulting average and standard deviation of 69.8
    and 6.8 respectively indicate a better trend in reliability.

          The final control experiment consisted of mixing the sediment

    with an electric drill fitted with a paint mixer at 160 rpm’s for
    15 minutes. The slow speed was used so as to oxidize the sediment

    as little as possible. The sediment was also spiked with 80umol
    Cd/g dry sediment (see appendix for calculations). The results are

    shown in table 6-2. Note the lack of variability (std dev of 3.71)
    and good recovery of the cadmium.
                                       6-2
    These control experiments have illustrated that there can be
variability in AVS within a vertical sediment core. They have also

showed that with a well mixed non frozen homogenized sediment there
is very little variability in the results. It is these results that

give reliability to the methods of these experiments.




                    Table 6-2
             Van Cortlandt Pond control
             spiked w/ 80 umol Cd/g dry
             mixed @ 160 pm for 10 min
                                                                          (I
                                                            Cd recovery
 IrY wt, g     % Solids   Vol (L)   AVS    SEM ppm           SEM umol/g

  1.52           16.54      .248    62.5        52.6           75.9
  1.52           16.54      .249    57.9        52.7           76.1
  1.34           16.54      .247    59.7        47'.1          76.6
  1.33           16.54      .247    59.8        47.8           77.3
  1.40           16.54      .247    65.5        47.2           79.0
  1.50           16.54      .248    57.2        49.8           73.9
  1.21           16.54      -246    63.2        37.9           68.4
  1.38           16.54      .247    51.9        42.9           68.5


                                AVS Avg = 59.7 umol/g dry
                                AVS std. dev.    =   3.71




                             6-3
                                                                      I
                                                                     V1
                                                              RESULTS
           The results of the AVS experiments run on 17 Foundry Cove cores

      initially confirm what was noted from the control experiments.
     Generally speaking, there is no indication from data obtainedthat
     AVS      is vertically                         stratified or trends numerically.                                                 Five cores
      (2,3,6,19) exhibit some kind of a decreasing trend in AVS values

     with depth (fig.7-1) . Cores (1,8,9,11,15) exhibit an increasing
     trend in AVS values                                      (figure 7-2). Several other cores exhibit

     complete variability (4,5,7,10,13,14,16,18,fig.7-3).
                                                                         Figure 7-1

            FOUNDRY COVE CORE 26                                                           FOUNDRY COVE CORE 3B

E
-60   in
      I


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                                                                                                                                                                Figure 7-2
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                              FOUNDRY COVE CORE 1A                                                                                                                                       FOUNDRY COVE CORE 8B
                                                                   AVS w              DEp1B:                                                                                                           AYS w DEPTH




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                                                                                                                                                                  ..........................
                                                                      Figure 7-3



                    FI)uwRycOvE       cORe4B                              FOUNDRY COVE CORE 5B
                        At5   . IlepIB
                              I                                                      AVS n   DepIB
    Id

          ...--fi-.------




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                                                                       . . . . . . . . . . . . . ._                          I
                                                                 DE             I            54                  76
                                                                                          -bi
       In   order   to    make    a    proper   scientific hypothesis               on the
stratification       of    acid    volatile     sulfides within          the       vertical
sections of sediment cores, analyses to a deeper depth would be

necessary and is beyond the scope of this study. The cores examined
in this study were examined to an average depth of 196 mm or about

8 inches. Table 7-1 is a statistical analyses of the averages and
standard deviations for each of the cores in this study.




                                       Table 7-1


                                        Avg     Std D     e   v    p   Avg    lStd DevII
                                         22.5      10.3
                                                          1
                                                          14

            4.6     3.1
                                         95.8

                                         70.0

                                         24.1
                                                   79.2

                                                   81.3

                                                   14.3
                                                              .15

                                                              15

                                                              17
                                                                       =M
                                                                       32.2
                                                                              I
                                                                                  15.3
                                                                                          II




                                  11     45.1      21.5       18
   6        8.5     8.5
                            I]    13
                                          0.5       0.2       19       17.2   I    22.2   1
            The purpose of this experiment is to illustrate how AVS and
SEM can be used to predict the potential for toxicity in a wetland

environment. As earlier stated, the use of total metal concenration
(mg/kg) to predict          toxicity is not reliable because different
sediments exhibit different degrees of toxicity f o r t h e same amount
of metal present. Also, if SEM/AVS > 1, the potential for toxicity

is present. With these two factors in mind, a vertical

                                  7-4
i



    section of a sediment can be characterized by showing how the
    SEM/AVS ratios and the total metals concentrations vary with depth,

    Figure 7-4 is a good example of this process. The data is from core
    #2 which is on the outskirts of the tidal marsh (refer to figure 4-
i
    1 for core locations). The horizontal line (value of 1.0 on the y-

    axis) is the line above which there is potential for toxicity

    (SEM/AVS>l). At about 13 cm down into the sediment at this location
    the potential for toxicity ceases to exist. Notice the decreasing
    trend in SEM/AVS ratios. Although not all cores show such a clear

    trend in values, all cores except for those at the two hot spots
    (10&11, 16&18) were analyzed to the point where the ratio went
i
    below 1.0.

                                             Figure 7-4


I                              FOUNDRY COVE CORE 2B
                                   TOTAL METAls AND SEM/AVS
            100000 3
J
       3     10000
       -
       9
       J
              1000

       3
       j       100
                10
       !
       rl       1
       2         .
                01
       2
       *       D.01
       2
             0.OD 1
                           0.6 2.4 4.2   6   7.8 9.6 11.4 13.2 15 16.8 18.6
                                                twm (cm)
                       I       TOTAL METALS mg/kg    SEM/AVS RATIO      I
!                                             7-5
               Core #14 (figure #7-5) is located in the middle of the cove.
         Although it is apparent that there is no potential for toxicity,
         the total metals concentration remains constant at nearly 1000 ppm,
         Unfortunately, because of inaccessibilitytothe site, this was the

         only sediment sample located in the open area of the cove available
         for analyses. Core 14 is a good example of how the sulfide content
         and subsequent metal binding capacity of a sediment can take what
         appears to be a toxic sediment from purely a metals concentration

         value and render it non-toxic.
                                          Figure 7-5



                             FOUNDRY COVE CORE 14B
           b                    TOTAL METAL CONCENTRATION AND SEM/AVS
               10000~                                                         I
                    A                                                         I




-?
     i     I
           1




                 -. .
           I
                            0.6 2.4 4.2   6   7.8 9.6 11.4 13.2 15 16.8
                                               DEPTR (cm)

                        I      TOTAL METALS rng/kg     SEMIAVS RATIO      I

                                              7-6
        Figure 7-6 is a series of plots of cores extending through the
    outlet stream, from the discharge pipe of the battery plant (cores
    10 & 11) through the tidal marsh and into Foundry Cove. The outlet

i   pipe area is an obvious hot spot. Total metals concentration is
    upwards of 20000 ppm, and SEM/AVS ratios are well above one.
    Proceeding away from the outfall area to core #9, observe how
i
    SEM/AVS becomes less than one at the 10 cm depth. An analyses of
i
    the data reveals that the total metal concentrations are still very
!
    high and the AVS values are in the same range as cores 10 & 11. It

    is the percent solids value of -10% as opposed to -40% for cores 10
I
    & 11 that makes the difference. This is a clear example of how
    different sediments exhibit different degrees of toxicity for the
    same total quantity of a metal.
        The next core in this series is f8. Metals concentrations are
    stil1,high and the SEM/AVS values dip below 1 at -7 cm. The
    analyses on this core indicates a second peak toward possible
    toxicity at -16 cm, and then drops well below the critical Itl"
    value afterwards. The entire core from sites 8 & 9 were analyzed,
    making deeper analyses impossible.
        Core #3 was one of four sandy and rocky cores (3,5,13,15). All
    other cores were generally fine grained in texture, dark to black
    in color, and appeared high in organic content. What is interesting
    about core #3 is that one would not expect a sulfide content in
    sediments of this nature. To the contrary, there are
    sulfides   available   to   bind   metals.   Although   total   metals
    concentration is much lower than the previous cores, it is still of
                                7-7
                                                            Figure 7-6




            FOUNDRY COVE CORE 10A                                            FOUNDRY COVE NCORE 11A
                                                                         TJTAL MKlAL Om m AND W/AE
                 ~ y K M L ~ A N D s g y / b v s




            FOUNDRY COVE CORE 9A                                             FOUNDRY COVE CORE 8B
                 ToraiLvKllaLaKZNWUNANDWAVS                                  ZTAL UIXALONCEKIRAMN AND Serr/AVS
                                                               100000

10000

    I000

    too
      10

       1

      .
     01

    OD I
            .
           06    1
                 6   3    A¶ 5 4 6 6 78
                                  . .     9   103 11A 1 .
                                                       26               06
                                                                         .    2A     L1    6    7 6 9 6 11.L 133 15 166 1.
                                                                                                     .                   86




                FOUNDRY COVE CORE 38                                            FOUNDRY COVE CORE 2B
                 m YgIbLmKXHIRBalNAND sxu/AVS                                             ?UTbLbiEMSBM,WAVS




1i 1
Y




a
E     .
     01
            Ob       11        3      U        SA       .
                                                       66                06
                                                                          .    ?.A   A2     6   7.8   9.6 1 . 1 .
                                                                                                           11 32    Is   1. 1.
                                                                                                                          61 86
                                -0
    significant value and high enough to be considered potentially
I   toxic. Because of the nature of the core sight, there was only 7 cm
    of sediment available for analyses.
        Core #2     is the last in this series. Note how the metals
    concentration    starts   dropping    significantly      at   10   cm.   The
    corresponding SEM/AVS ratios also drop and go below 1 at -12 cm.
    It is at this point where SEM and AVS values get very low and the
    percent   solids goes above 50%.           This   is another example how
    different characteristics exhibit varying effects.
        This series of cores has illustrated through AVS analyses how
    the potential for toxicity not only decreases with depth, but also
I
I   with the physical characteristics a sediment may have.
        Figure 7-7 is a series of cores extending through a secondary
    stream headed at a hot spot and continuing onto the cove at core #2
    (core'#2 was described above and is omitted here). Cores 16 and 18
    confirm   the   existence of   a     hot    spot where   sediment metals
    concentration is well above 10,000 ppm.
        Core #19 still has high metals concentration, but because of

    its low percent solids (-20%), the sample appears to be mostly non-
    toxic. The metal concentration in the sediment of core #7 drops
    considerably (below 1000 ppm), as the site is downstream from the
    previously noted hot spot. The drop in metals concentration is the
    primary reason this core exhibits no potential for toxicity except
    at the surface.




                                   7-9
                                                                   Figure 7-7




100000 I

    10000

     1000
                  TUTAL HmL   -
                FOUNDRY COVE CORE 16B
                                             AND W A i a
                                                               1      100000

                                                                          10000

                                                                           1000
                                                                                   FOUNDRY COVE O E 18B
                                                                                                 R
                                                                                   ?OTdLYgfeL[nKZMRBT13N AND W A Y S




      loo                                                                   100

       IO                                                                    IO

           I                                                                  I

       .
      01
                                                                                  Ob        21
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                                                                                                                                     96




                FOUNDRY COVE CORE 19A
                  TUTAL YgUL U X R m AND SXY/AE
                              NMAN
RIOOOOs
8    1000                                                            5
f    100                                                             f     loOD




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                                                                             10


                                                                             1

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                                 .       9    02 I
                                             1 . I L 126 136
                                                                      2      .
                                                                            01
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                                                                                                              .        66
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            Figure 7-8 is a series of cores extending from where the outlet
        stream departs the tidal marsh           and enters the cove, to where
        Foundry Brook enters the cove from the northeast. Note the trend in
I
!       decreasing total metal concentration from west             (core 2) to east

        (core 1). There is a similar trend in the SEM/AVS ratios toward no
        toxicity. Only core #15, high in sand & gravel sized particles,
        exhibits a potential for toxicity according to the ratios. The fact
        that metal concentrations are below 6 ppm in the sediment indicates

        that regardless of the sulfide content, this is not a dangerously
I
        toxic sediment.
                 Core #l is located where Foundry Brook enters the tidal marsh
        and the cove. Although non-toxic according to the theories of this
        study, metal contamination has reached the mouth of the brook. This
i       is in contrast to core #13 which lies above a small dam upstream of
        core fl. Although core #13 had a low sulfide content due to its
        sandy     characteristics,    there     was   no   evidence     of   any    metal
        contamination and thereby serves as a point of reference in this

        study.
            Figure 7-9 is a contour map illustrating the extent of metal
        contamination     in   the   sediment    (mg/kg),   and   the    areas     which,

        according to AVS theory, may be considered potentially toxic.
                                                               Figure 7-8



           F O U N D R Y COVE CORE 28                                                   FOUNDRY COVE CORE 6A
                                                                                       Iuw.ETAL mKENlRdlMN AND SU/AVS
                 lauLvBTarsAFiDWAVS
                                                           I




     a6 24 4 2
            .    6   7.8 96 11.4 132   is   168 186
                          (s
                         -a

 I      TOTAL METALS       m SEMIAVSw n o                                               TOTAL METALS mykg         SEMIAVS wno

                                                                                                                                .
                                                                                                                                '




      F O U N D R Y COVE CORE 58                                                       FOUNDRY COVE CORE 15B
       XIW YEW ( K " W A V S
                D X AND                                                                TUTAL LU3ALCllK;EKIRA'IDN AND W A V S
                                                                    y '"I        --




                                                                    1E
                                                                    8
                                                                            lo
                                                                            1



                                                                    2 ".                .
                                                                                       06      12   18
                                                                                                     .
                                                                                                          =
                                                                                                          2.4     3   36   4.2      4.8


[a
 TOTALMETALB              =    SEWAVS wno          1                                       TOTAL METALS mykq
                                                                                                                 (d
                                                                                                               m SEMIAVSRATIO           I
      F O U N D R Y COVE CORE 46
       ~     ~       ~    A      N     D       W       A        t    S




                                                                            01

                                                                    4
                                                                         001
                                                                                      06      iE    3    42     54    66    .
                                                                                                                           78       9


I b ~TOTALMETALS
      ]                   =    SEWAVS wno          I                                  aTOTN METALS -9 m SEWAVS wno
                                       I1
                                      V1
                                   CONCLUSIONS
J
-?           This    study   has    been    successful   in   illustrating   how   Acid
        Volatile Sulfides can predict the potential for toxicity in heavy

        metal laden anoxic sediments. Foundry Cove is a known heavy metal
        contaminated site which has been used as an example to demonstrate
        how heavy metals displace the iron in iron sulfides to form non-

        toxic metal sulfides.
 i
             It has been described through the core slicing procedures how

        to: quantify AVS vertically in a sediment section; and by atomic

        adsorption spectrometry quantify the SEM. These two quantities can
        than be compared t o detect if there is          a potential for toxicity.

             Control experiments indicated little variability in AVS values
    i
        in a well homogenized sediment sample. This verifies reliability in
    i   lab procedures and confirms variability                 of AVS   in a vertical
_I
        sediment sample.
             Toxicity tests on Foundry Cove (Di Tor0 et al, 1992) revealed
        that metal concentrations of 0.1 to 28 umol SEM/g were not toxic in

        some sediments, while SEM values of 0.2 to 1000 umol/g were toxic
        in   other     sediments.      This      collaborates    previous    statements
        indicating different sediments with different qualities exhibit
        different degrees of toxicity and bioavaility of metals for the
        same quantity of a metal in those sediments.
                                           8-1
            Results of the study presented herein present data that clearly
,
        depict how toxicity decreases with distance fromthe discharge pipe
i
i
i       of the battery plant. If the ratio SEM/AVS      e   1 signifies no

        toxicity or bioavailibity of the toxic metal ion, an environmental
i       remediation point of view may indicate no need for dredging in the
t       cove, but only in the marsh areas containing the two creeks leading
i
i
        to the cove.




i
    i




                                   8-2
                                     REFERENCES

II       Beaty, R.D. 1978.   Concepts, Instrumentation, and Techniques in
         Atomic Absorption Spectrophometry. Perkin Elmer
r
         Chiou, C.T., et.al. 1976. Partition Coefficient and Bioaccumulation
         of Selected Organic Compounds
         Di Toro, D.M., Mahony, J.D., et.al., 1992. Acid Volatile Sulfides
         Predicts the Acute Toxicity of Cadmium and Nickel in Sediments.
         Environmental Science and Technology.
         Di Toro, D.M., et.a1.,1990. Toxicity of Cadmium in Sediments: the
         role of acid volatile sulfides. Environmental Toxicology and
         Chemistry.
         Di Toro, D.M., et.al., 1991. Technical basis for establishing
         Sediment Quality Criteria for nonionic organic chemicals by using
         equilibrium partitioning. Environmental Toxicology and Chemistry.

         Hazen, R.E.   1981. Cadmium in an Aquatic Ecosystem (in press).

         Gonzalez, A.M., 1992. Heavy metal sorption in anoxic sediments. An
         experimental study of sediment organic carbon as a metal-binding
         phase ‘under anoxic conditions (in press).



     i



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                         AVS vs DEPTH
40




0'I    I    1    1   I   I    I     1    1    I    I    I   I    I   I   1
 0.6       1.8       3       4.2        5.4       6.6        .
                                                            78       9
                                  DEPTH (cm)
           FOUNDRY COVE CORE 2B
                      A\7S       17s       DEPTH
      80

      70
n
i? 60
z
U
                I \
  ?
‘50
I
c\2
m
4     40
0

2 30
W




9 20
4
                                 A

            v
           ‘’                v
                             ’
                             ‘       \
                                     ‘
      10

      OIIIIIIIIIIIIIII                 1   1   1   1   1   I   I   I   1   1   1   1   1   1   1   I   I
           FOUNDRY COVE CORE 3B
                             AVS       17s       DEPTH
     3.5

      3




N'     2
m




     0.5

            I    I   I   I   I     I         I      I     I    I   I   I    I
           0.6               3                           5.4               7.8
                                       DEPTH (cm)
             FOUNDRY COVE CORE 4B
                                                     A\7S vs DEPTH
    14

    12
n
h
k
Q   10

    8

    6

    4

    2

    0    -     l   1   1       1   1   1    1    1   1   1   1   1   ~   11   1 ~   1   ~ 1    1   1   I   l   l    I   I   I    I   I   I
         0.6               3               5.4           7.8       10.2                       12.6             15               17.4
                                                             DEPTII (cm)
           FOUNDRY COVE CORE 5B
                            AYS vs DEPTH
 80

 70



?
'50
I




 10.

       I    1   I   I   I   I   I     I   1   I   I   I    I    I   I   I
      0.6               3                5.4              7.8
                                    DEPTH (cm)
1




J
                      FOUNDRY COVE CORE 6A
                                           A17S       1s
                                                       7    DEPTH
             25
i1
8

!       n20
'            h
        k
i
        d
I
' IY15
         -
        P4
        0




I
    !
                 0    I    I   I   I   I   I      I     I    I     1   I   I    I    I   1   1

                     0.6               3                   5.4                 7.8
                                                      DEPTH (cm)
                  FOUNDRY COVE CORE 7A
                                          AVS   1s
                                                 7   DEPTH
        AE;
        7 J
              .




        40

3 35
4
h~ 30
\
    I
n~ 25
n
i
+
P


        20                I   \       I

        15
                      I           V




                  I
          FOUNDRY COVE CORE 8A
    160

    140
n
h
a 120                                              I       \


?
‘ 100
    80

    60

    40

    20     I    I   1   1   1   I   1     I    I       I       1   I    1    I   I   I

          0.6               3                 5.4                      7.8
                                        DEPTH (cm)
      FOUNDRY COVE CORE 8B
450
          FOUNDRY COVE CORE 9A
                    A17S    1s
                             7   DEPTH
    300.


    250


hD 200
\
I




      0                                         1   1    I     1
          0.6   3     5.4          7.8   10.2           12.6
                             )mI
                            1EI(C11I)
      FOUNDRY COVE COR3E 1OA




0.6      24
          .    4.2    6       7.8       .
                                       96    14
                                            1.    13.2
                          DEPTH (em)

      TOTAL METALS rng/kg      SEM/AVSRATIO
                                                     I
           FOUNDRY COVE CORE 1-1A
                                 AVS       1s
                                            7       DEPTH
      90

      80




k
2 40
W


I/i
+ 30                             /
-4
      20    /




      10    I    I   1   I   I   I     1        I    I   1   I   I    1    I   1   I
           0.6               3                  5.4                  7.8
                                           DEPTH (cm)
I


i




                      FOUNDRY COVE CORE 1-3A
                               A\7S       17s   DEPTH
                0.9
    I

                0.8

    i       .i; 0.7

                0.6
            d



                0.5        \
                                                            /       \

                0.4

    i           0.3

                0.2    I   I          I                 I       I       1



                                          IIEPTII (CIl.1)

        I
         FOUNDRY COVE CORE 1 4
                            7B
                                                  AVS         1s
                                                               7       DEPTH
    80

    70
n
h




    20

    10    1   1   1   1   1   1   1   1   1   1   1   1   1    1   1   1   1   1   1   I    I   I   1   1   1    1   1   1    I   r
         0.6              3               5.4             7.8       10.2                   12.6             15               17.4
                                                              DEPTH (cm)
FOUNDRY COVE CORE 15B
       AVS   17s    DEPTH




             DEPTH ( m i )
i




        FOUNDRY COVE CORE 1-6B
               A\7S   1s
                       7   DEPTH




    ,
         FOUNDRY COVE CORE 1-8A
                               AVS vs DEPTH
    45

    40
n
335
5

?
'30
I




    10                                                     V




     5    1    1   1   1   1   1   1     1    1    1   1   1    1    1   1   I
         0.6               3                 5.4               7.8
                                       DEPTH (cm)
      FOUNDRY COVE CORE 19B
                  A\7S   1s
                          7   DEPTH
100 I   A
                                      I
 90     I\
 80
 70
 60
 50
 40          \
 30          \,
 20
 10                  \




                         DEPTH (em)
                FOUNDRY COVE CORF 1A
                TOTAL METAL CONCENTRATION AND SEM/AVS
    1oo-i




            I
                TOTAL METALS mg/kg   SEM/AVSRATIO   II
i
              FOUNDRY COVE CORE 2B
                       TOTAL METALS AND SEM/AVS

10000
1000




   !.
 - 01I
  .1
 00  4
     -I



0.0014-
                            DEPTH (em)

          I   TOTAL METALS mg/kg     SEM/AVS RATIO
         FOUNDRY COVE CORF 3B
r
2             TOTAL METAL CONCENTRATION -ANDSEM/A\!S:




                        I   I       I   I          I

        0.6       1.8           3       4.2            5.4   6.6
                                DEPTH (em)

    I     TOTAL METALS mg/kg                SEM/AVS RATIO
                                                               I
i




                   FOUNDRY COVE COR-E
                                    4B
.-Ii
   M               TOTAL METAL CONCENTRATION AND SEM/AIS   ,



       10003




                                  DEPTH (cm)

               I   TOTAL METALS mg/kg    SEM/AVSRATIO
-1




 i




 i

                 FOUNDRY COVE CORF.5B
                     TOTAL METAL CONCENTRATION AND SEM/AVS
 100000~




               0.6      .
                       18     3    4.2   5.4 6.6   7.8    9
                                    DEPTH (em)

           I         TOTAL METALS mg/kg   SEM/AVS RATIO   '   I
FOUNDRY COVE COR-E
                 6A
TOTAL METAL CONCENTRATIONAND SEM/AVS




               DEPTH (cm)

TOTAL METALS mg/kg    SEM/AVS RATIO
                                      I
                 FOUNDRY COVE CORF.7A
                 TOTAL METAL CONCENTRATION AND SEM/AVS
\   10000~




             I   TOTAL METALS mg/kg   SEM/AVS RATIO   I
     FOUNDRY COVE COR-E
                      8A
       TOTAL METAL CONCENTRATION AND SEM/AVS




    0.6. 1.8   3    4.2   5.4   6.6   7.8   9
                     DEPTH (cm)

I     TOTAL METALS mg/kg    SEM/AVS RATIO       I
                FOUNDRY COVE COR-E
                                 8B
                TOTAL METAL CONCENTRATION AND SEM/AVS




01
 .1
0.01t
            0
                               DEPTH (em)

        I       TOTAL METALS mg/kg    SEM/AVSRATIO
       FOUNDRY COVE CORE 9A
       TOTAL METAL CONCENTRATION AND SEM/AVS




00 t
 .1
                   DEPTH (cm)
                      1OA
     FOUNDRY COVE COR-E
       TOTAL METAL CONCENTRATION AND SEM/AVS




 L
 .
01

                      DEPTH (cm)

     TOTAL METALS mg/kg    SEM/AVSRATIO
                   FOUNDRY COVE COR?E 1
                                    1A
                    TOTAL METAL CONCENTRATION AND SEMIAVS
'q   100000,
jw
Id




        0.

                                  DEPTH (cm)

               I   TOTAL METALS mg/kg    SEM/AVS RATIO
                 FOUNDRY COVE C0R.E14B
5                       TOTAL METAL CONCENTRATIOK AND SEM/AVS
a 10000~
7




    0.1+        .   .

               0.6 2.4 4.2      6   7.8 9.6 11.4 13.2 15   16.8
                                     DEPTH (cm)

           I        TOTAL METALS mg/kg     SEM/AVSRATIO
                  FOUNDRY COVE COR-E
                                   15B
                   TOTAL METAL CONCENTRATION AND SEM/AVS
’?%        100,




     L ’
IO                06
                   .   12
                        .    .
                            18   2.4    3   3.6   42
                                                   .    .
                                                       48
iE-i
                                 DEPTH (em)

                  TOTAL METALS mg/kg   SEM/AVS RATIO
 i
  ,




              FOUNDRY COVE CORE 16B
               TOTAL METAL CONCENTRATION AND SEM/AVS
100000~




                            DEPTH (cm)

          I   TOTAL METALS mg/kg   SEM/AVS RATIO   I
          FOUNDRY COVE COR-E
                           18B
                TOTAL METAL CONCENTRATION AND SEM/AVS




_.
 ~




         0.6        2.4      4.2       6     7.8    9.6
                              DEPTH (em)

     I         TOTAL METALS mg/kg    SEM/AVSRATIO
1
    i
i
                    FOUNDRY COVE CORE 19A
                     TOTAL METAL CONCENTRATION AND SEM/AVS


         1004




         0.I
          ’~
        0.001
          .1
         00


1
                                   DEPTH (cm)

                I   TOTAL METALS mg/kg    SEM/AVSRATIO




    t

								
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