EPA-821-R-51-100
United States
Eayuwnmentii Protection Agency
OfEiee of Science and Technology
Health tad Ecological Criteri* Div.
Wuhingun. DC 20460
EPA
Draft Analytical Method
for Determination of Acid
Volatile Sulfide in Sediment
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DETERMINATION OF ACID VOLATILE SULFIDE AND
SELECTED SIMULTANEOUSLY EXTRACTABLE METALS IN
SEDIMENT
December 1991
H. E. Allen and G. Fu
University of Delaware
Newark, Delaware
W. Boothman
Environmental Research Laboratory - Narragansett
U. S. Environmental Protection Agency
Narragansett, Rhode Island
and!
D.M. DiToro and J.D. Mahony
Manhattan College
Bronx, New York
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1. SCOPE AND APPLICATION
1.1 " ^ describes procedures for the
salfide
SEM). As a precipitant of toxic heavy
sulfidc is
portant
wita sninde.
2. SUMMARY OF METHOD
one, de .ode b«vy n«ab in ft*
ditiOI1S f0r ^^ °f
. useful means of as^sing the mourn of meal
±^Ie"to^VG^tohy^«sn^^s)byac^^
^ «d«nx» tempoatum The H,S b Aca purged fiom Ac an^
u» aqueous solutkm. TTw amoont of salfide ttut lus been trapped is tfaea
The SEM an: selected »** libcn^ed &«„ ftc sedinmding the
Hiesearedetenmnedaftafflimioiiofthes.inplc.
2.2 Two types of apparatus for sample purging and trapping of I^S are described. One
uses a senes of Erlenmeyer flasks while the other uses flasks and traps with ground
Elass stonnerc TK-fnrm^ ,v !..,.„ _~.,.i-. •»- _,._.. . ^ ^ ^^
lo^recoveiyof AVS The latter is recoriimended when higher degrees of precisions
aesmd and for samples containing low fcsvels of AVS.
2.3 Three means of quantifying the H2S released by tcidifying the sample are provided
The^cokninetricmetn<)disgenefiinyprcfen^ In the gravimetric procedure, the H*S
is trapped m silver nitrate. The silver sulfide that is formed is determined by weighing
(1. 2). This procedure can be used for samples with moderate or high AVS
concentrations. Below 10 umolcs AVS/gram dry sediment, accuracy may be affected
by incomplete recovery of precipitate and by weighing enors. In the colorimetric
method, the H2S is trapped in sodium hydroxide. The sulfide reacts with N-N-
dimethy-p-phenylenediamine to form methylene blue that is measured (3) This
procedure is capable of determining AVS concentrations as tew as 0.01 jimoles/gram
dry waght of sediment By appropriate simple dilution, the maximum concentration of
AVS and SEM Procedure December 2,1991 „*„ i
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AVS which can be determined is at leat 1000 nmoles/gram dry sediment. In an
alternative procedure the H^S is trapped in an antioxidant buffer before using an ion-
selective electrode (4,5).
2.4 After release of the H2S, the acidified sediment sample is membrane fihered before
determination of the SEM by atomic absorption or inductive coupled plasma
spectrometic methods (6,7).
3. DEFINITIONS
3.1 ACID VOLATILE SULFIDE (AVS) -AVS is operationally defined as sulfides that form
hydrogen sulfide under the conditions of this test. This includes amorphous,
moderately crystalline moDosulfides, and other sulfides (8).
3.2 SIMULTANEOUSLY EXTRACTED METALS (SEM) - SEM are operationally defined
as metals, commonly cadmium, copper, lead, mercury, nickel and zinc, that form less
soluble sulfides than do iron or manganese, and which are at least partially soluble
qn
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analy^ex^yunea sample. Its purpose is to determine whether the staple matrix
coombuies bias to the analytical results. "*««*
4. INTERFERENCES
4.1 Contact with oxygen must be avoided in all stage, from sampling to analysis
Consequently, the samples and standards should be protected from air from the time of
sampling through the analytical procedure. This can be achieved by deaeratin* and
mamtaiiirngtltesannjlesiirMfa «™
5. SAFETY
5.1 The toxicity or carcinogemcity of reagents used in mis method have not been fully
established Each chemical and environmental sample should be regarded as a potential
health hazard and exposure should be raninnad. Each laboratory is responsible for
maintaining a current awareness file of OSHA regdtficw rcganfing the safe handling
of the (Aemicds specified* this nwhod A referee fik of material safety daashem
should be available to all personnel involved in the chemical analysis.
5.2 Hydrogen sulfide is a highly poisonous, gaseous compoiiirf having a diatacteristic
odor of rotten eggs. It is detectable in air by humans at a concentration of
approximately 0.002 ppm. Handling of acid saaiples shouki l« perfonned in a hood or
well ventilated area. If aWghconcentmiooofhydrofensuffideisdetectedintte
the laboratory staff, sample handling procedures most be corrected According to Sax
(9) an air concentration of 10 ppm of H2S is pemritted for an 8 hour shift for 40 hours
per week.
5.3 If samples originate from a highly contanmused aica, appio^
pnxeduies to rmnitTrire worker exposure must be followed.
6. APPARATUS AND EQUIPMENT
6.1 Glassware
6.1.1 AVS evolution and H^S trapping - Glassware in Section 6.1.1.1 is
recommended Glassware in Section 6.1.1 3. may be used, but will not provide
as high precision or accuracy for samples.
6.1.1.1 For highest precision and tow AVS levels - For each analytical train
500 mL gas washing bottles or oxygen trap, one 250 mL round
bottom flask with a septum (Ace Glass 6934 or equivalent), 100 or
AVS and SEM Procedure December 2, 1991 naae3
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250 mL impiogen with non-fritted outlets. The round bottom
contains the sediment and acid is introduced to it by a syringe inserted
through the septum. The flasks are connected by tubing. Because
sulfide may react with tubing and other surfaces, minimum lengths of
tubing should be used as slieves to connect the glass tubing. The
analyst should pay particular attention to the recovery of sulfide from
standards in evaluating the apparatus. In all cases the inlets are below
the liquid level and the outlets are above the liquid leveliu The
apparatus is assembled as shown in Figure 1 and more than one
analytical train can be connected to a single cylinder of nitrojea or
argon if flow controllers are installed in the line. Different amounts of
glassware are required for each of the three means of snlfide
Figure 1. Apparatus far AYS ddrrmrnafinn- 1. Nj or AT cylinder, 2, On washing bottles: (a)
oxygen scrubbing solution or an oxygen trap may be used in replacement of this gas washing
bottle, (b) deionized water; 3. Three-way stopcock; 4. Flow controller; 5. Reaction flask; 6.
Magnetic surer; 7. Impingers with non-fritted outlets.
6.1.1.2 For routine analysis - Erlenmeyer flasks, 250 mL, are substituted for
the gas washing bottle, the round bottom flask and the impingers.
The flask size should be consistent with sample size and reagent
volumes. A thistle tube fitted with a stopcock or a separatory funnel is
provided to introduce acid to the flask containing the sediment sample.
This flask is fitted with a three bofe stopper. One hole is for the thistle
tube or sepanuory funnel and the odwr two are for the gas inlet and
AVS and SEM Procedure
December 2,1991
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outlet Tneotherflasks are fitted wim t^ fade stopper* one
by tubing. Beau* suttfc
stoppen „«, o«her
be o«i u .Beve, » «»«, „«
5.1.2 Ev^oraring dishes, poroUdn, 100 mL.
6.1.3 Assorted cthTjnuediapcttesaiiclv
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oxygen from the deionized water by vigorously bubbling with oxygen-free nitrogen or
argon for approximately one hour. Deaerate reagents immediately before use by
deaeraring with oxygen-free nitrogen or argon.
7.2 Sodium sulfide standard - Required for quality assurance and calibration.
7.2.1 Sulfide stock standard solution, approximately O.Q5M or 50 nmolesymL.
7.2.1.1 Weigh about 12 gram of NifeS-SHjO and dissolve it in 1,000 mL of
deionized water. Store in a brown bottle. To prevent air oxidation,
the sulfide solution should be maintained under oxygen-free nitrogen
or argon.
7.2.1.2 Standardize against thiosulfate solution.
7.2.1.2.1 Pipette 10.00 mL of 0.025N standard iodine solution
(SeetioQ 7.2.2) into each of two 125-mL Erlenmeyer
flasks.
7.2.1.2.2 Pipette 2.00 mL of sulfide stock standard solution into one
flask. Pipette 2.00 mL of deionized water, as a laboratory
reagent blank, into the other flask.
7.2.1.2.3 Add 5.00 mL of 6M Hd into each flask, swirl slightly,
then cover and place in the dark for 5 minutes.
7.2.1.2.4 Titrate each with 0.025N thiosulfate (Section 7.2.3) until
the yellow iodine color fades to a pale straw. Just before
all the iodine has been titrated, add starch indicator
(Section 7.2.4) dropwise to form a pale blue color.
Coptifiue Jfcs dJratioo with the thiosulfate. The end point is
reached when the bine color first disappears.
7.2.1.2 J Calculate the sulfide concentration as follows:
Sulfide Oimol/mL) . (T*-*-T-i*)x*W x 1 mole S*J x 1000 umoles
V^pfc 2equrvS Immole
where T * volume of titrant used for the blank and sample (ml.)
N * concentration of SjOf* titrant
V = volume of sample used (mL), 2.00 mL recommended
7.2.2 Standard iodine solution, 0.025N - Dissolve 20 to 25 gram potassium iodide,
H, in a small volume of «vintii»»d water, add 33 gram iodine, and dilute to
1,000 mL. Standardize against 0.025N sodium thiosulfate (Section 7.2.3)
AVS and SEM Procedure December 3,1991 page 6
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7.2.3 Standard sodium thiosulfate solution, 0.025N. May be purchased
= • comMdafly or prepared in the laboratory. Standardize against potassium *
1 ••'' - -. .*V;-V.[ .' - --••-uj' -"V'j •.
7.2.3.1 Weigh approximately 6.2 g of sodium thiosulfate, Na,S2O,.5 H,O
into a 500 mL beaker. Add 0.1 g sodium carbonate/N^CO, and
dissolve in 400 mL cleionized water. Pbur into a 1.0 L vduLric
flask and dilute to volume with deionized water.
7.2.3.2 StanrimttiTntion against potassium bi-i
7.2.3.2.1 Prepare 0.00208M potasrinm bi-iodate by dissolving
0.8123 g KBOOife. previously dried 2 hr at 103-105-Q
in distilled water. Pour into a 1.0 L volumetric flask and
dilute to volume with deionized water.
7.2.3.2.2 Dissolve approximately 2 g KI, free from iodate, in an
erlenmeyer flask with 100 to 150 mL deionized water
Add 1 mL of 6N HjSO4 or a few drops of concentrated
HjS04 and 20.00 mL of standard bi-iodate solution
Dilute to 200 mL and titrate me liberated iodine with the
thiosulfate solution until the yeUow color fades to a pale
straw color. Tlwi add a coupfe drops of starch indicator to
form a pale blue color and continue the titration with the
thiosulfate untfl the blue color first dasappears..
7.2.3.2.3 20.00 mL of 0.00208M KHaQj^ requires exactly 20.00
mL of 0.025N sodium thiosulfate. For an calculation of
the thiosulfate concentration use the following equation:
ImoteKHdO,), 12 eqnhr KO(l^\ 100oIBL
389.9fKH(IQ,)2X ~"
--•P * ***
7.2.4 Starch indicator - Diswrve LO gnm solubte stai^
water.
7.2.3 Solfide working standards -Preparesulfide woddngstano^rds UMg the snlflde
stock standard solution in Section 7.2.1. Tlic concemrations of the following
standards wffl depend on the exact concentration of the sulfide stock standard
determined in Section 7.2.1.2.5. Correct concentrations of the the standards in
the following part of this section iind the amount of sulfide in standards used in
the cokrimetric method in Section 12.2J by multiplying by a factor of the
concentration determined in Section 7.2.1.2.5 drvided by 50 nmoles/mL.
A VS and SEM Procedure December 2.1991
page 7
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7.2.5.1 Prepare sulfide working standard A by diluting 1.00 mL of sulfide
stock standard to 100.0 mL. This solution contains 0.5 jimole
sulfide/ml., if the concentradon of the sulfide stock standard is exactly
0.05M.
7.2.5.2 Prepare sulfide working standard B by diluting 10.00 mL of snlfide
stock standard to 100.0 mL. This solution contains 5.0 umote
concentration of the mlfirif fttyfr «f»nHarr}
0.05M.
7.3 AYS evolution
7.3.1 Hydrochloric acid 6M - Dflnte 500 mL of concentrated hydrochloric acid (sp.
gr. 1.19) to 1L with deiomzed water. Dearation of this solution as described in
Sections 7.1 and 11. 4 is most important
7.3.2 Nitrogen or argon gas, oxygen free, with regulator and flow controller. An
oxygen gas scrubber may be required and is available commercially or
deoxygenating solutions may be placed in the first flask or gas washing bottle in
the analytical train.
7.3.3 Plastic hvpodenmc syringe, 30 mL, and needle.
7.4 Gravimetric method
7.4. 1 Potassium acid phthalate, 0.05M - Dissolve 10-2 g of potassium acid pbihalate,
KHCjH4O4, in deionized water and dilute to 1L.
7.4.2 Silver nitrate, 0. 1M - Dissolve 17 g of silver nitrate, AgNOj, in deionized water
and dilute to 1L. Store in a dark bottle.
7.4.3 Glass fiber filters, 1.2 micron - Rinse with deionized water, then predry filters
atl03-105*C
7.5 Cokximetric method
Sodium hydroxide solution, 1M - Dissolve 40 g sodium hydroxide in 1000 mL
7.5.2 Sodium hydroxide solution, 0.5M - Dissolve 20 g sodium hydroxide in 1000
mL deionized water.
7.5.3 Mixed diamine reagent, MDR
7.5.3.1 Component A - Add 660 mL concentrated sulfuric acid to 340 mL of
deionized water. After the solution cools, dissolve 2.25 g N-N-
dimethy -p-pheny lenediamine oxidate in it.
AVS and SEM Procedure December 2, 1991 page 8
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7.5.3.2 Component B -Dissolve 5.4 g fenic chloride hexahydnie CRCV6
HjO) in 100 mL concentrated hydrochloric acid and dilute to 200mL
with deionized water.
7.5.3.3 MKcddiaminereagcait,MDR.MixcoinpooentsAandB.
7.5.4 Sulfuric acid solution. l.OM - Dilute 56 mL coocentmed sulfuric acid (H,SO )
to 1L with deionized wiser.
7.6 Ion-selective electrode method
7.6.1 Sodimnhydroridesolutkn-IXssolve 80 gof sodium hydroxide in 700 mL of
daonized waier with caution. Ccoi to mom temperature.
7.6.2 Sulfide antwxidant buffer (SAOB) - To the sodium hydroxide solutk. in
Section 7.6.1 add and dissolve 74.45 g of disodrum ethylenedianrinetetraacedc
acid and 35231 of ascorbic acid Dilute to 1L with deionized water.
8. SAMPLE COLLECTION, PRESERVATION AND STORAGE
8.1 Sulfide ion is unstable in the presence of oxygen. Protect sediment samples from
exposure to oxygen during sample collection and storage.
8.2 I^gstorajF sulfide can be foraed a-k»
k^byvolatifauioooroxidarion. Metsaspeciation can ch«ige as a result of changes m
sulfide conceotratka and as aresult of other changes in the sample.
8.3 Samples should be collected in wide mouth jars with a mnimum of air space above the
sediment If possible, the beadspace should be filled with oxygen fire nitroge. or
argon. The jar fids must have Teflon or polyethylene liners.
8.4 Samples should be cooled to 4"C as soon as possible after collection. Samples
maintained at 4*C have been found to have no significant loss of AVS for sttnge
periods up to 2 weeks (3). Holding time for samples should not exceed 14 days.
9. CALIBRATION AND STANDARDIZATION
9.1 Calibrate the photometer with a nrinimim of few standanb aiid a blank that cover n^
expected range of the samples. Prepare a calibration graph relating absorbance k> the
umoles of sulfide taken.
9.2 Calibrate the sulfide electrode system with a imnimumrf thro staadaris that cw
expected range of the samples. Standards must be made op in SAOB diluted 1+1 with
deionized water. Follow the manufactiner's instructions foruse of the electrode.
AVS and SEM Procedure December 2,1991
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9.3 Overall sulfide recovery is determined by analysis of a known amount of sodium
sulfide standard added to deionized water from which the sulfide is tiberated in the
analysis train (LFB). Recoveries of 95% ± 10% are expected.
10. QUALITY CONTROL
10.1 Each laboratory using this method is required to operate a formal quality control (QQ
program. The minimum requirement of this program consists of an initial
demonstration of laboratory capability, and the analysis of laboratory reagent blanks,
fortified blanks and fortified samples as a continuing check on performance. The
laboratory is required to maintain performance records that define the quality of data
thus generated.
10.2 INITIAL DEMONSTRATION OF PERFORMANCE
10.2.1 The initial demonstration of performance is used to characterize instrument
performance, method detection omits, and linear calibration ranges.
10.2.2 Method detection limit (MDL) - The method detection limit should be
established for the analyte, using deionized water (blank) fortified at a
concentration two to five times the estimated detection hmit (10X Todetermine
MDL values, take seven replicate ahqnots of me fortified reagent water and
process through the entire analytical method. Perform aU calculations and
report the concentration values in the appropriate mm-? r?*imia«» the MDL as
follows:
MDL-t x s
where, t * students' t value for a 99% confidence level and a standard deviation
estimate with n-1 degrees of freedom (t» 3.14 for seven repticatesX and
s » standard deviation of the replicate analyses.
Method detection limits should be determined every six months or whenever a
significant change in background or instrument response is expected.
10.2.3 Linear calibration ranges - The upper limit of the linear caHbratico range should
be established by determining the signal responses from a minin^r. off four
different concentration standards covering the expected range, one of which is
close to the upper limit The linear calibration range that may be used for the
analysis of samples should be judged by the analyst from resulting data, linear
calibration ranges should be determined every six months or whenever a
significant change in instrument response may be expected.
AVS and SEM Procedure December 2,1991 page 10
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10.3 ASS^NO MORATORY PEWORMANCE - REAGENT AND FORTIFIED
la
oratory reagent blank (Section 3.4) with e*± set
10.3.1 laboratory reageniblank (LfiB) - The laboratory must analya at least one
laboratory or reagent OTtanrin«ion should be
fa the recent blank exceeds its detennincd
should be c^
f the problem should b* Identified
10.3.3 Until sufficient d«a become a^ulabie fiom within tbeir
to
against recoveor limits (s) of the mean recovery. These
trol limits as follows:
UPPER CONTROL LIMIT »x + 3i
LOWER CONTROL LIMIT - x - 3s
Aftereach five to ten new recovery measurements, new control limits should be
calculated using only the most recent twenty to thirty data points.
«T™ .„„ „ RECOVERY - LABORATORY FORTIFIED SAMPLE
10.4.1 The laboratory must fortify a minimum of 10% of the routine samples or one
fortified[sample per set of 20 samples, whichever is greater. Atletstooe
sample from each source should be fortified. Idealry, the co«entration should
•t least double the background concentration. Over time, samples from afl
routine sample sources should be fortified.
10.4.2 Calculate the percent recovery for the analyte, corrected for background
concentrations measured in the uirfotffied sample, aiid con^are these values 10
the control Emits established in Section 103.3 for the analyses of LFBs. Spike
recovery calculations are not required if tte spike coooatration is less than 10^
A VS and SEM Procedure December 2,1991 „,....
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of the sample background concentration. Percent recovery may be calculated in
units appropriate to the matrix, using the following equation:
x 100
where
R * percent recovery,
C, -fortified sample cofxxatration,
Cb « sample background concentration, and
S » concentration equivalent of the fortified sample.
10.4.3 If the recovery of the analyte in the fortified sample Ms outside the designated
range, and the laboratory performance on the LFB for the analyte is shown to
be in control (Section 10.3) the recovery problem encountered with the fortified
sample is judged to be matrix related, not system related.
11. GENERATION OF HjS
11.1 Assemble glassware according to the detection method to be used. The setup in Figure
1 should be followed as a general guide. In an cases a flask or gas washing bottle
containing a deoxygenating solution may be placed in the sample train between die
nitrogen or argon tank and the first flask. Glassware is specified in Section 6. 1.1. bis
recommended that nitrogen or argon be controlled by a flow controller, but an
equivalent flow rate may be regulated by a damp and bobble rate determined, hi ifl
cases the glassware wfll minimally consist of a H2S generating flask and a series of
traps.
11.1.1 Gravimetric method - The first flask contains the •^""fqf sample or standard.
The second flask contains 175-200 mL of potassium hydrogen phthalate reagent
7.4.1 as an HQ trap. The third and fourth flasks contain 175-200 mL of sflvtr
nitrate reagent 7.4.2, If glassware specified in Section 6.1.1.1 is used. the
second flask is a gas washing bottle and the third and fourth flasks are
impingers.
1 1.1.2 CoJorimetric method - The first flask contains the sediment sample or standard.
The second and third flask contain an absorbant of 80 mL 0.5M NaOH reagent
7.5.2. If glassware specified in Section 6.1.1.1 is used, the second and third
flasks are impingers.
AVS and SEM Procedure December2,1991 page 12
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11.1.3 toa-selectivc ekctrode method -The firetfl..i, _ •
,
*~~* by bub** nfce^™ £ SS£. fl^T
Reduce flow to 40 cat/aon. ™«e* ««oowraie of
through *•
imgKdc^ly air the Mmpte « Ae
12. ANALYSIS OF SULFTOE
12.1 Gnvimetric method
12.1.1 Insure that thefin^^ap, the second silver nidate tnp, contains no precipitate
1Wid,deiooi«dw«« . Dry
AVSandSEMPtocedure December? 1991
"* page 13
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12.1.3 Calculate the amount of silver sulfide as the difference between the weight of
silver sulfide and the filter and the weight of the predried filter.
12.1.4 Calculate the amount of sulfide in the sample:
Sulfide in wet sediment (umoles)
12.2 Cokjrimetric method
12.2.1 If the AYS concentration is low so thai the solfide contained in the tube trap is
kss than 15 umoles, add 10 mL of the mixed diamine reagert (MDR) directly to
the NaOH solution in each trap tube to develop the color. Transfer this solution
tot ^nnmT.vrJimv-jrigfl«
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' *' ' DOcs '« «*P«*vely. Add 10 0
of MpR to each and dilute » 100.00 at^STdltafa
*« absocbance«670nm.
12.2.5.2 High range cafibration curve - 0.0 - 20.0 nmoles S2-
(0.0 - 640 jig S2-)
Add 80 mL O5M sodium hydroxide in 100 mL ffcsks and add (LOO
~
flasks. These samples contain 0.0, 5.00. 10.00, 15.00, and 20.00
Mn»l« S2-, respectively. Add 10.0 mL of MDR and dflute to 10000
ml , wuh deiomzad w«er. After 30 mmutes, dfluie the solutio. 10-
fold with 1.0MH2»34. and measure the absorbance at CTOmn.
12.2.6 Obdtt ite amount of solfiidc Oimoles) in the san^k fiom the
e cao,
curve. ffthetotalvotoofNaOHinthetr^wasnocusedinthean^
account for the potion tested. «w anaiyas,
12.3 loo-selective electrode method
12.3.1 Calibrate « the sulfide decnode ud meter .ccordinj to nunufacturer's
" SAOB
12.3.2 T«»fcr the contents of each ssdfkk tnq> into 1 100-mL volumetric flast Rinse
the a-ap with deiooized water, Bidding the rinses to the volumetric flask. Dflnie
to volume with deicmized water. ^^
12.3.3 Pbur contents of volumetric flask into a 150-mL beaker, add a stirring bar and
place on saner. Begin stining with mmimum agitation to avoid entiainnxnt of
•n- into the solution and minimize oxidation of the sample during the
12.3.4 Rinse sulfide and reference electrodes into waste container and blot dry with
absorbent tissue. Immerse electrodes in sample solution.
12.3.5 ABow electrode response to stabilize (8-10 iiMutes). then take measurement of
suffice concentration. Depending on the meter used, the reading may be
(fctcflym concent^
poutt calibration has been performed. If the readings are in millivolts, convert
mdhvolts to concentration using the calibration curve obtained from standard
solutions.
12.3.6 Calculate the amount of sulfide (nmoles) in the sample.
A VS and SEM Procedure December 2.1991 page 15
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13. CALCULATION OF AVS CONCENTRATION IN SEDIMENTS
13.1 The sediment dry weight/wet weight ratio (R) most be determined separately. Add
volatile sulfide can be oxidized or altered to non-volatile forms during drying.
13.2 Transfer an aliquot of the sediment to a tared 100-mL tared evaporating dish. Weigh
the dish plus the wet sediment. Calculate the wet weight of the sample. Dry the
sediment at 103- 105"C and weigh. Catenate
13.3 Determine the ratio of dry weight to wet weight for the sediment sample:
where R = ratio of dry weight to wet weight,
Wd » dry weight of sediment sample (g), and
Ww s wet weight of sediment sample (g).
Also, the weight of water, W^^, taken in a sample for AVS analysis can be calculated.
If the weight of the wet sediment sample taken for the AVS analysis is W^.^, the
g^ght of water c*y»t*in«»H in the sediment sample would be
Ww-w - W^ - (R x W^)
The volume of water in the sample equals the weight of water, assuming the density is
near unity.
13.4 Compute the sulfidc concentration per gram dry weight of tBdimrnr
where S » the amount of AVS m sediment |unoles) finxn Section 12.1.4,
112.6, or 12.3.6, as appropriate,
R * ratio of dry weight to wet weight from Section 13.3, and
Ww m wet weight of sediment (g) taken for AVS analysis.
13 J The QC data obtained during the analysis provides an indication of die quality of die
sample data and should be provided with the sample results.
14. DETERMINATION OF SIMULTANEOUSLY EXTRACTED METALS (SEM)
14.1 After the generation of sulfide has been completed, filter the sediment suspension
remaining in die I^S generation flask (Section 11.4) through a 0.2 H membrane filter
AVS and SEM Procedure December 2, 1991 page 16
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resistant to attack by acid. The filtering apparatus should be soaked in 0.1M HNO,
then rinsed with deiooized water prior to use.
14.2 Transfer the filtrate to a 250-mL volumetric flask. Rinse the filtering flask with distilled
water, adding the rinses to the volumetric flask. Dilute to volume with deionized water
The volumetric flasks should be soaked in 0.1M HNO,. then rinsed with deionized
water prior to use. Samples should be analyzed within 2 weeks,
14.3 Detennine the concentrations of soffidebiiidmg metals of interest and tho^
molar basis, are present at more than 1 percent of the AVS concentration. Do not
include iron and manganese whose snliides are less stable than are the sulfides of many
trace metals. Metals which may typicafly be included in SEM are cadmium, copper
lead, mercury, nickel and zinc. In addition, antimony, bismuth and chromium, among
others, form insoluble sulfides. If significant concentrations of these or other metals
forming insoluble sulfides are present, their coix^tnitions shoiikl be taken into account
in the computation of SEM. However,, if these or other metals which are not divalent
are present in significant concentrations, the computation in Section 14.5 must be
modified to account for the stoichiometry. Metal concentrations may be determined by
by atomic absorption, inductive coupled plasma spectrometK, or another approved
method (6, 7). Calibration may be by the method of standard additions or by a
calibration curve. If a calibration curve is used. IMIT« maich standards to simples by
inctoding20mLrf6MHaperlCOinLfbreadiof^ Coo^
o
concentration values to umofes/L. Multiply the jimoles/L by the solution volume
to obtain the pmoles of metal
14.4 Report the concentrations of each of the metals in the sediment on a umole per gram dry
s**tim*tir basis.
14.5 CalculatetheratioofSEMtoAVS:
SEM m £[metal]
AVS * AVS
where SEM is me sum of the concentrations of metals, £ [metal], for the meals
(e.g., cad mi urn. copper, lead, mercury, nickel and zinc) in Section 14.4 and
AVS is the acid volatile sulfide concentration determined in S«ctionl3.4.
BoA SEM and AVS are expressed on a^mofe per gram dry sediment (jimol/g) basis.
Because metals present in the pore will be included in the analysis, the ratio could be
less than that if correction were made for this contribution. This win lead to a
conservative estimation of potential bioavaOabfliry (1).
AVS and SEM Procedure Decembers, 1991 page 17
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15. REFERENCES
1. DiToro, D.M., J.D. Mahony, DJ. Hansen, KJ. Scott, MB. Hicks, S.M. Mayr and
M.S. Redmond, Toxicity of Cadmium in Sediments: The Role of Acid Volatile
Sulfide", Environmental Toxicology and Chemistry, 1990,9, 1487-1502.
2. Morse, J.W., FJ. Millero, J.C CornweU and D. Rickard, "The Chemistry of the
Hydrogen Sulfide and Iron Sulfide System in Natural Waters", Earth Science Review,
1987,24,1-42.
3. ABen, HE., G. Fu and B. Deng, "Determination of Acid Volatile Sulfide (AVS) in
Sediment", Report to Environmental Protection Agency Office of Water Regulations
and Standards, Washington, December 1990, 26 pages; Allen, K&, G. Fu and B.
Deng. "Determination of Acid Volatile Sulfide (AVS) and Simultaneously Extracted
Metals (SEM) in Sediments", presented at the 12th Annual Meeting of (he Society of
Environmental Toxicology and Chemistry", Seattle, 1991.
4. Boothman, W.S., "Acid-volatile Sulfide Determination in Sediments Using Sulfide-
specific Electrode Detection", U.S. Environmental Protection Agency Environmental
Research Laboratory, Narragansett, R.L, anrfft^ft 8 pages.
5. Raiiminn, EW.. "Determination of Parts Per Billion Sulfide in Water with fee Sulfide -
Selective Electrode", Analytical Chemistry, 1974,46,1345-1347.
6. U.S. Environmental Protection Agency. "Methods for Chenxkad Analysis of Waisrtnd
Wastes", EPA-600/4-79-020, revised March 1983.
7. "Standard Methods for the Examination of Water and Wastewater", 17th edition,
APHA, AWWA, WPCF, 1989.
8. Comwell, J.C. and J.W. Morse, 'The Characterization of Iron Sulfide Minerals in
Anoxic Marine Sediments", Marine Chemistry* 1987.22,193-206.
9. Sax, NJ. and RJ. Lewis, Sr. "Dangerous Properties of Industrial Materials, 5th. ed..
Van Nostrand Reinhold, New York, 1989.
10. Code of Federal Regulations 40, Ck 1. PL 136, Appendix B.
AVS and SEM Procedure December 2,1991 page 18
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