UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, DC. 20460

OCT I5 1993 OFFICE OF WATER Dear Environmental Advocate:

On October 1, 1993, I signed a memorandum regarding the Office of Water’s Policy
and Technical Guidance on Interpretation and Implementation of Aquatic Life Metals
Criteria. This memorandum covers a number of areas including the expression of aquatic
life criteria, total maximum daily loads, National Pollution Discharge Elimination System permits and enforcement, effluent monitoring, and ambient monitoring. The policy and guidance in this document considers comments received from the US. Environmental
Protection Agency (EPA) Regional Offices, recommendations made to EPA by the participants in a meeting held in January 1993 in Annapolis, Maryland, and public comments
in the June 8, 1993, Federal Register notice requesting general public comments on the Annapolis meeting recommendations. As stated in the enclosed memorandum, we will
continue to issue guidance as more information becomes available.

Sincerely yours,

Martha G. Prothro Acting Assistant Administrator
EnclosureUNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

OCT 1 1995 OFFICE OF MEMORANDUM WATER

SUBJECT: Office of Water Policy and Technical Guidance on Interpretation and

Implementation of Aquatic Life Metals Criteria
FROM: Martha G. Prothro

Acting Assistant Administrator for Water
TO: Water Management Division Directors

Environmental Services Division Directors Regions I-X
Introduction
The implementation of metals criteria is complex due to the site-specific nature of metals toxicity. We have undertaken a number of activities to develop guidance in this area, notably the Interim Metals Guidance, published May 1992, and a public meeting of experts held in Annapolis, MD, in January 1993. This memorandum transmits Office of Water (OW) policy and guidance on the interpretation and implementation of aquatic life criteria for the management of metals and supplements my April 1, 1993, memorandum on the same subject. The issue covers a number of areas including the expression of aquatic life criteria; total maximum daily loads (TMDLs), permits, effluent monitoring, and compliance; and ambient monitoring. The memorandum covers each in turn. Attached to this policy memorandum are three guidance documents with additional technical details. They are: Guidance Document on Expression of Aquatic Life Criteria as Dissolved Criteria (Attachment #2), Guidance Document on Dynamic Modeling and Translators (Attachment #3), and Guidance Document on Monitoring (Attachment #4). These will be supplemented as additional data become available. (See the schedule in Attachment #1.)
Since metals toxicity is significantly affected by site-specific factors, it presents a number of programmatic challenges. Factors that must be considered in the management of metals in the aquatic environment include: toxicity specific to effluent chemistry; toxicity specific to ambient water chemistry; different patterns of toxicity for different metals; evolution of the state of the science of metals toxicity, fate, and transport; resource limitations for monitoring, analysis, implementation, and research functions; concerns regarding some of the analytical data currently on record due to possible sampling and analytical contamination; and lack of standardized protocols for clean and ultra&an metals analysis. The States have the key role in the risk management process of balancing these factors in the management of water programs. The site-specific nature of this issue could be perceived as requiring a permit-by-permit approach to implementation. However, we believe2

that this guidance

canbe effectively implemented on a broaderlevel, acrossanywaterswith roughly the same

physicalandchemicalcharacteristics, and recommend

thatwe work with the States with that perspective

in mind. wssion of Aauatic Life Criteria 0 Dissolvedvs. Total Recoverable Metal A major issueis whether,andhow, to usedissolvedmetalconcentrations (“dissolved metal’) or total recoverable metalconcentrations

(“total recoverable

metal”) in settingState waterquality standards. In the past,States haveusedboth approaches

whenapplying the sameEnvironmentalProtectionAgency(EPA) criteria numbers. Someolder criteria documents

mayhavefacilitatedthese

different approaches

to interpretationof the criteria because thedocuments

were somewhat

equivocalwith regards

to analytical methods. The May 1992interim guidance continuedthe policy that eitherapproach wasacceptable. It is now the policy of the Office of Waterthatthe useof dissolvedmetalto setand measure compliance

with waterquality standards is the recommended

approach,because dissolvedmetalmorecloselyapproximates the bioavailablefraction of metal in the water columnthandoestotal recoverable metal. This conclusionregardingmetalsbioavailability is supported by a majority of the scientific communitywithin andoutsidethe Agency. One reason is that a primary mechanism for watercolumntoxicity is adsorptionat the gill surface which requiresmetals

to be in the dissolved

form. The positionthat the dissolvedmetals approachis moreaccurate

hasbeenquestioned because it neglects the possible

toxicity of particulatemetal. It is truethat somestudieshave indicatedthat particulatemetalsappear to contributeto thetoxicity of metals,perhaps because of factorssuchasdesorption of metals at the gill surface,but thesesame studies indicatetie toxicity of particulatemetalis substantially lessthanthatof dissoivcd metal. Furthermore,any error incurredfrom excludingthecontributionof particulatemetal will generallybecompauatedby other factors which makecriteria coamtive. For example,metalsin toxicity testsare added assimplesaltsto relatively cleanwater. Due to the likely v of a significantconcentration of metals binding agents

in manydischarges andambientwaters,metalsin toxicity testswould generallybe expected to be more bioavailabilethanmetalsin discharges or in ambientwaters. If total ncoverable metalis used for the purpose

of waterquality stand&s, compounding

of factorsdueto the lower bioavailability of partioulatemetal andlower bioavailability of metals

asthey aredischarged

may resultin a ‘&nserWive water quality standard. The useof dissolvedmetalin waterquality standards givesa more accura&result. However,the majority of the participants at theAnnapolismeetingfelt that total recoverable measurements

in ambientwater hadsome value, andthatexceedences of criteria on a total recoverable

basiswere an indicationthat metalloadingscould be a stress to theecosystem, particularly in locationsotherthanthewatercolumn.3

The reasons

for thepotentialconsideration of total recoverable

measurements

include risk management

considerations

not coveredby evaluation

of watercolumntoxicity. The ambientwaterquality criteria are neitherdesigned nor intended

to protectsediments,

or to preventeffectsdueto foodwebscontainingsediment dwelling organisms. A risk manager, however,mayconsidersediments andfood chaineffectsand maydecideto takea conservative

approachfor metals,considering that metals

arevery persistent

chemicals. This conservative

approachcould includethe useof total recoverable metal in waterquality standards. However, sinceconsideration of sediment

impactsis not incorporatedinto the criteria methodology,thedegree of conservatism

inherentin thetotal recoverable apprach is unknown. The uncertaintyof metalimpactsin sediments stemfrom the lack of sediment criteria andan impreciseunde&andingof the fateandtransport of metals. EPA will continueto pursueresearch andotheractivitiesto closetheseknowledgegaps. Until the scientific uncertainties are betterresolved,a rangeof different risk management

decisionscanbejustified. EPA recommends that Statewaterquality standards be based on dissolvedmetal. (Seethe paragraph below andthe attached guidance for technicaldetailson developingdissolved criteria.) WA will alsoapprovea Staterisk management

decisionto adoptstandards based on total recoverable

metal, if thosestandards areotherwiseapprovable

asa matterof law. 0 DissolvedCriteria In thetoxicity testsusedto developEPA metalscriteria for aquaticlife, somefraction of the metal is dissolved

while somefraction is boundto particulatema=. The present criteria were developedusingtotal recoverable metalmeasurements

or measures

expected to give equivalentresultsin toxicity tests,andarearticulatedastotal recoverable. Therefore, in order to express

the EPA criteria asdissolved, a total recoverable

to dissolvedcorrection factor mustbe used. Attachment #2 providesguidance

for aMating EPA dissolvedcriteria from the publishedtotal recoverable criteria. Thedataexpressed aspercentage

metal dissolved are presented

as recommended

values and ranges. However,the choicewithin rangesis a Staterisk management decision. We havencently suppiernaM the datafor copperandare proc&ing to further supplement hedatafor copperandother metals. As testingis completed,we will makethis informationavailableandthis is expected to rake the magnitude

of the ranges

for some of the conversion

f&ctors provided. We also strongly encourage the applicationof dissolved criteria across

a water&d or watehody, as tcchnicalIysoundandthe bestuseof resources. 0 Site-SpecificCriteria Modifications While the abovemethods

will correctsome

site-specific

factorsaffecting metals toxicity, further refinements arepossible. EPA hasissued guidance(WaterQuality Standards Handbook, 1983;Guidelines for Deriving NumericalAquatic Site-Specific Water Quality Criteria by Modifying National Criteria, EPAd00;3-He099, October 1984)for three site-specificcriteria development methodologies:recalculation procedure,indicator species procedure(alsoknown asthewater-effectratio (WER))andresidentspecies procedure. Only the first two of thesehavebeenwidely used.4

In the NationalToxics Rule (57 FR 60848, December 22, 1992),EPA identified the WER a~anoptional methodfor site-specific criteria development

for certain metals. EPA committedin the NTR preamble to provideguidance

on determiningtheWER. A draft of this guidance

haJbeencirculatedto theStates and Regions

for reviewandcomment. As justified by watercharacteristics andasrecommended

by theWER guidance,we strongly encourage the applicationof theWER across awatershed

or waterbodyasopposed

to applicationon a discharger by discharger

basis,astechnicallysoundandan efficient useof ESOUrcts.In order to meetcurrent needs, but allow for changes

suggested by protocol users, EPA will issuethe guidance as ‘interim.’ EPA will accept WERsdeveloped

usingthis guidance,aswell asby usingother scientificallydefensible protocols. OW expects

the interim WER guidance

will be issuedin the nexttwo months.

. . . . . . 

### TotalMaxlmumM~LoadsOandn System DES) Peru&

0 DynamicWaterQuality Modeling Although not specificallypart of the reassessment of waterquality criteria for metals, dynamicor probabilistic modelsare anotherusefultool for implementing waterquality criteria, espaziallyfor thosecriteria protectingaquaticlife. Thesemodelsprovide another way to incorporatesite-specific data. The 1991

TechnicalSupportDocumentfor Water Quality-based

Toxics Control (TSD) (EPA/505/2-90401)describes dynamic,aswell asstatic (steady-state)

models. Dynamic modelsmakethe bestuseof the specifiedmagnitude, duration, and ikaquency

of waterquality criteria and, therefore,providea moreaccurate representation

of the probability that a waterquality standard exccedence

will occur. In contrast,steady-state

modelsmakea numberof simplifying, worst case assumptions

which makes them lesscomplexand less accuratethan dynamicmodels. Dynamic modelshavereceivedincrcaxd attentionoverthe lastfew yearsasa result of thewidespread

belief that steady-state

modelingis over~servative dueto environmentally

consuvativedilution assumptions.ntir belief hasled to the misconception that dynamicmodels

will alwaysleadto lessstringentngulatoiy controls(e.g., NPDES effluent limit@than steady-state models,which is not true in evq applications of dynamic models. EPA considers

dynamicmodels

to bea m~fe accu approach to implementing waterquality criteria andcontinues to recommend

their use. Dynamicmodelingdoesrequire commitment

of resources

to developappropriate

data. (See

Attachment

#3 andtheTSD for detailson the useof dynamicmodels.)

0 Dissolved-Total

Metal Translators Expressing

waterquality criteria asthedissolved form of a metalposes

a needto be ableto translate

from dissolvedmetalto total recoverable metalfor TMDLt and NPDES permits. TMDLs for metalsmustbe ableto calculate: (1) dissolvedmetalin order to ascertain attainment of waterquality standards, and (2) total recoverable

metalin order to achievemass

balance necessary for permittingpurposes.5

EPA’s NPDESregulationsrequirethat limits of metalsin permitsbe stated astoa recoverable

in mostcases

(see 40 CFR $122.45(c))exceptwhenan effluent guideline specifies the limitation in another

form of the metal,theapproved analytical methods measure only dissolvedmetal,or the permit writer expresses a metalslimit in anotherform (e.g., dissolved,valent,or total) when rqclired to carry out provisionsof the CleanWater Act. This is because

thechemicalconditionsin ambientwatersfrequentlydiffer substantially from thosein the effluent, andthere is no assurance thateffluent particulatemetalwould not dissolve after discharge. The NPDESrule doesnot requirethat Statewater quality standards be expressed

astotal recoverable;

rather, the rule requirespermit writers to translate between different metalforms in thecalculationof the permit limit sothat a tota! recoverable limit canbe established. BoththeTMDL and NPDESuses of waterquality criteria requirethe ability to translatebetween dissolvedmetalandtotal recoverable metal. Attachment#3 providesmethods

for this translation.

. . Guidance on Monttonng 0 Useof CleanSamplingandAnalytical Techniques In assessing

waterbodies

to determine

the potentialfor toxicity problemsdueto metals,the quality of thedatausedis an importantissue. Metalsdataarc usedto determine attainmentstatus

for waterquality standards, discerntrendsin waterquality, estimate backgroundloadsfor TMDLs, calibratefateandtransportmodels,estimate effluent concentrations

(including effluent variability), assess permit compliance,and conduct research. The quality of tracelevel metaldata,especially below 1 ppb, may be compromised

dueto contamination

of sampies

during collection, preparation,storage,and analysis. Depending

on the level of metalpresent,the useof ‘clean” and ‘ultraclean’ techniques

for samplingandanalysismaybe critical to accurate datafor implementation

of aquaticlife criteria for metals. The magnitude

of thecontamination

problemincreases

asthe ambientandeffluent metalconcentration

decreases and, therefore,problems

arc morelikely in ambient measurements.“Clean” techniques refer to thoserequirements (or practicesfor sample collection and handling)nv to producereliableanalyticaldatain the part per billion (ppb) range. “Ultraclean’ techniques refer to thoserequinmentsor practicesnecessary to producereliable analyticaldatain the part per trillion (ppt) range. Because typical concentrations

of metalsin surface

watersandeffluentsvary from one metalto another,the effect of contamination

on thequality of metalsmonitoring&a variesappreciably. We plan to developprotocolson the useof cleanandultra-cleantechniques andare coordinatingwith the United States GeologicalSurvey(USGS)on this project, because USGS hasbeendoing work on these techniques

for some time, e-s-y the samplingprocedures. We anticipatethat our draft protocolsfor cleantechniques will be availablein late calendar year 1993. The development of comparable

protocolsfor ultra-cleantechniques is underway andwill be availablein 1995. In developingthese protocols,we will considerthe COSTS of thesetechniques

andwill give guidance

asto thesituations

wheretheir useis necessary. Appendix B to theWER guidance documentprovidessome

generalguidance

on the useof6

cleananalyticaltechniques. (SeeAttachment #4.) We recommend

that this guidancebe used by Stausand Regionsasan interim step,while the clean andultra-cleanprotocolsare being developed.

0 Useof Historical Data The concerns

aboutmetalssamplingandanalysisdiscussed aboveraisecorresponding concerns aboutthe validity of historicaldata. Dataon effluent andambientmetal concentrations

are collectedby a varietyof organizations including Federalagencies (e.g., EPA, USGS),Statepollution control agencies andhealthdepartments,

local government agencies, municipalities,industrialdischargers, researchers,

and others. The data are collectedfor a variety of purposes asdiscussed

above. Concernaboutthe reliability of the sample collectionandanalysisprocedures is greatest wherethey havebeenusedto monitorvery low level metalconcentrations. Specifically,studieshaveshowndatasetswith contamination problemsduring sample collectionand laboratoryanalysis,that haveresultedin inaccurate measurements.For example,in developinga TMDL for New York Harbor, somehistorical ambientdatashowed extensive metalsproblemsin the harbor,while other historicalambientdatashowedonly limited metalsproblems. Careful resampling andanalysisin 199Zl993 showed the latter view wascorrect. The key to producingaccurate datais appropriatequality assurance (QA) and quality control (QC) procedures. We believethat mosthistoricaldatafor metals, collectedandanalyzedwith appropriateQA andQC at levelsof 1 ppb or higher, are reliable. The data usedin development of EPA criteria arealsoconsideredreliable, both because they meetthe abovetestandbecause thetoxicity testsolutionsare createdby adding knownamounts

of metals. With respect

to effluent monitoring reportedby an NPDESpermit&e, the permitteeis responsible

for collectingand reportingquality dataon a DischargeMonitoring Report (DMR). Permittingauthorities shouldcontinueto considerthe information reportedto be true, accurate,

and complete

ascertified by thepermittee. Wherethe permitteebecomes awareof new information specificto theeffluentdischarge thatquestions

thequality of previouslysubmittedDMR data,the permitteemustpromptly submitthat information to the permittingauthority. The permitting authority will considerall information submitted by the permitteein detamSng appropriateenforcement responses to monitoring/reporting and effIuentviolatia~. (SeeAttachment X4for additionald&is.)

The management

of metalsin theaquaticenvironmentis complex. The science supporting

our technicaland regulatoryprogramsis amtinuing to evolve, hereasin ail areas. The policy and guidance outlinedaboverepresent

the position of OW and shouldbe incorporated

into ongoingprogramoperations. We do not expectthat ongoingoperations would bedelayedor deferredbecause of this guidance.7

If you havequestions

concerning

this guidance,please

contactJim Hanlon, Acting Director, Office of Science andTechnology,at 202-260-5400. If you havequestions on specificdetailsof theguidance,please contacttheappropriateOW BranchChief. The BranchChiefs responsible

for thevariousareas

of the waterquality program are: Bob April (202-260-6322,

waterquality criteria), ElizabethFellows (202-260-7046,monitoring anddata issues),RussKinerson(202-260-1330,modelingandtranslators),Don Brady (202-260-7074, Total Maximum Daily Loads), SheilaFrace(202-260-9537, permits), Dave Sabock (202-260-1315,

waterquality standards),

Bill Telliard (202-260-7134, analytical methods) and DaveLyons (202-260-8310, enforcement).

AttachmentsATTACHMENT #1
TECHNICAL GUIDANCE FOR METALS
Schedule of Upcoming Guidance

Water-effect Ratio Guidance - September 1993

Draft “Clean” Analytical Methods - Spring 1994

Dissolved Criteria - currently being done; as testing is completed, we will release the updated percent dissolved data

Draft Sediment Criteria for Metals - 1994

Final Sediment Criteria for Metals - 1995ATTACHMENT #2

GUIDANCE DOCUMENT ON DISSOLVED CRITERIA Expression of Aquatic Life Criteria

October 199310-1-93

Percent Dissolved in Aquatic Toxicity Tests on Metals

The attached table contains all the data that were found concerning the percent of the total recoverable metal that wag dissolved in aquatic toxicity tests. This table is intended to contain the available data that are relevant to the conversion of EPA's aquatic life criteria for metals from a total recoverable basis to a dissolved basis. (A factor of 1.0 is used to convert aquatic life criteria for metals that are expressed on the basis of the acid-soluble measurement to criteria expressed on the basis of the total recoverable measurement.) Reports by Grunwald (1992) and Brungs et al. (1992) provided references to many of the documents in which pertinent data were found. Each document was obtained and examined to determine whether it contained useful data. "Dissolved" is defined as metal that passes through a 0.45 -μm membrane filter. If otherwise acceptable, data that were obtained using 0.30 -μm glass fiber filters and 0.1 -μm membrane filters were used, and are identified in the table; these data did not seem to be outliers. Data were used only if the metal was in a dissolved inorganic form when it was added to the dilution water. In addition, data were used only if they were generated in water that would have been acceptable for use as a dilution water in tests used in the derivation of water quality criteria for aquatic life; in particular, the pH had to be between 6.5 and 9.0, and the concentrations of total organic carbon (TOC) and total suspended solids (TSS) had to be below 5 mg/L. Thus most data generated using river water would not be used. Some data were not used for other reasons. Data presented by Carroll et al. (1979) for cadmium were not used because 9 of the 36 values were above 150%. Data presented by Davies et al. (1976) for lead and Holcombe and Andrew (1978) for zinc were not used because "dissolved" was defined on the basis of polarography, rather than filtration. Beyond this, the data were not reviewed for quality. Horowitz et al. (1992) reported that a number of aspects of the filtration procedure might affect the results. In addition, there might be concern about use of "clean techniques" and adequate QA/QC. Each line in the table is intended to represent a separate piece of information. All of the data in the table were determined in fresh water, because no saltwater data were found. Data are becoming available for copper in salt water from the New York 1Harbor study; based on the first set of tests, Hansen (1993)

suggested that the average percent of the copper that is dissolved in sensitive saltwater tests is in the range of 76 to 82 percent. A thorough investigation of the percent of total recoverable metal that is dissolved in toxicity tests might attempt to determine if the percentage is affected by test technique (static, renewal, flow-through), feeding (were the test animals fed and, if so, what food and how much), water quality characteristics (hardness, alkalinity, pH, salinity), test organisms (species, loading), etc. The attached table also gives the freshwater criteria concentrations (CMC and CCC) because percentage8 for total recoverable concentrations much (e.g., more than 

### a factor 

### of 3) above or below the CMCand CCC are likely to be less relevant. When a criterion is expressed as a hardness equation, the range given extends from a hardness of 50 mg/L to a hardness of 200v/LThe following is a summary of the available information for each metal:

The data available indicate that the percent dissolved is about 100, but all the available data are 

### for concentrations that are much higher than the CMCand CCC.
Cadmium Schuytema et al. (1984) reported that "there were no real differences" between measurements of total and dissolved cadmium at concentrations of 10 to 80 ug/L (pH - 6.7 to 7.8, hardness - 25 mg/L, and alkalinity - 33 mg/L); total and dissolved concentrations wsre 

### said to be "virtually equivalent". The CMCand CCC are close together and only range from 0.66 to 8.6 ug/L. The only available data that are known to be in the range of 

### the CMCand CCC were determined with 

### a glass fiber filter. The percentages that are probably most relevant are 75, 92, 89, 78, and 80.

The percent dissolved decreased as the total recoverable concentration increased, even though the highest concentrations reduced the pH substantially. The percentages that are probably 2most relevant to the CMC are 50-75, whereas the percentages that

are probably most relevant to the CCC are 86 and 61. Chromium(VIl The data available indicate that the percent dissolved is about 100, but all the available data are for concentrations that are much higher than the CMCand CCC.

CODDeq Howarth and Sprague (1978) reported that the total and dissolved concentrations of copper were "little different" except when the total copper concentration was above 500 ug/L at hardness - 360 mg/L and pH = 8 or 9. Chakoumakos et al. (1979) found that the percent dissolved depended more on alkalinity than on hardness, PH, or the total recoverable concentration of copper. Chapman (1993) and Lazorchak (1987) both found that the addition of daphnid food affected the percent dissolved very little, even though Chapman used yeast-trout chow-alfalfa whereas Lazorchak used algae in most tests, but yeast-trout chow-alfalfa in some tests. Chapman (1993) found a low percent dissolved with and without food, whereas Lazorchak (1987) found a high percent dissolved with and without food. All of Lazorchak's values were in high hardness water; Chapman's one value in high hardness water was much higher than his other values. Chapman (1993) and Lazorchak (1987) both compared the effect of food on the total recoverable LCSO with the effect of food on the dissolved LC50. Both authors found that food raised both the dissolved LCSO and the total recoverable LCSO in about the same proportion, indicating that food did not raise the total recoverable LCSO by sorbing metal onto food particles; possibly the food raised both LCSOs by (a) decreasing the toxicity of dissolved metal, (b) forming nontoxic dissolved complexes with the metal, or (c) reducing uptake. The CMCand CCC are close together and only range from 6.5 to 34 w/L. The percentages that are probably most relevant are 74, 95, 95, 73, 57, 53, 52, 64, and 91.

The data presented jn Spehar et al. (1978) were from Holcombe et al. (1976). Both Chapman (1993) and Holcombe et al. (1976) found that the percent dissolved increased as tha total recoverable concentration increased. It would seem reasonable to expect more precipitate at higher total recoverable concentrations and 3therefore a lower percent dissolved at higher concentrations.

The increase in percent dissolved with increasing concentration might be due to a lowering of the pH as more metal is added if the stock solution was acidic. The percentages that are probably most relevant to the CMCare 9, 18, 25, 10, 62, 68, 71, 75, 81, and 95, whereas the percentages that are probably most relevant to the CCC are 9 and 10.

The only percentage that is available is 73, but it is for a concentration that is much higher than the CMC.


### Nickel The percentages that are probably most relevant to the CMCare 88, 93, 92, and 100, whereas the only percentage that is probably relevant to the CCC is 76.
Seleniun No data are available.
Silver There is a CX, but not a CCC. The percentage dissolved seems to be greatly reduced by the food used to feed daphnids, but not by the food used to feed fathead minnows. The percentages that are probably most relevant to the CMCare 41, 79, 79, 73, 91, 90, and 93.


### Zinc The CMCand CCC are close together and only range from 59 to 210 v/L* The percentages that are probably most relevant are 31, 77, 77, 99, 94, 100, 103, and 96.

4Recommended'Values (%)A and Ranges of Measured Percent Dissolved Considered Most Relevant in Fresh Water
Metal

Arsenic(II1) Cadmium Chromium(II1) Chromium(V1) Copper Lead Mercury Nickel Selenium Silver Zinc QE ccc

Recommended Recommended Value f%1 [Ranae $1 Value f%1 (Ranae %L 95 1oo-104B 95 1oo-104B 85 75-92 85 75-92 85 50-75 85 61-86

- 95 100' 95 loo* 85 52-95 85 52-95 50 9-95 25 9-10 85 73B NAE NAE 85 88-100 85 76 NAE NAC NAE NAc 85 41-93 YYD YP 85 31-103 85 31-103

A The recommended values are based on current knowledge and are subject to change as more data becomes available. * All available data are for concentrations that are much higher than the CMC.

= NA = No data aro available. D YY = A CCC is not available, and therefore cannot be adjusted. E NA = Bioaccumulative chemical and not appropriate to adjust to percent dissolved.Concn. A Percent

lYaL.l I2ia.2 g t+eciesD $RFe FOOC$ Hard. AUL EH Ref.

B (Freshwater: CCC = 190 Ug/L; CMC = 360 W/L) 600-15000 104 5 ? ? ? 48 41 7.6 Lima et al. 1984 12600 100 3 I94 F No 44 43 7.4 Spehar and Fiandt 1986

QiDW 0.16 0.28 0.4-4.0 13 15-21 42 10 35 51 6-80 3-232 450-6400 (Freshwater: CCC = 0.66 to 2.0 ug/L; CMC

41 3 DM R Yes 53 75 ? Dkl R Yes 103 92O ? cs F No 21 89 3 FM F No 44 96 8 Fn S No 42 84 4 Fn S No 45 78 3 DIY S No 51 77 ? DH S No 105 59 3 Df4 S No 209 ' 80 8 ? S No 47 90" 5 ? F ? 46 70 5 FM F No 202 = 1.8 to 8.6 WL) p 46 7.6 83 7.9 19 7.1 43 7.4 Chapman 1993

Chapman 1993 Finlayeon and Verrue 1982 Spehar and Fiandt 1986 31 41 7.5 7.4 38 7.5 88 8.0 167 8.4 Spehar and Carbon 1984

Spehar and Zarlson 1984 Chapman 1993 Chapman 1993 Chapman 1993 44 7.5 Call et al. 1982 42 7.4 Spehar eti al. 1978 157 7.7 Pickering and Cast 1972CHROHIUH(IXI) (Freshwater: ccc = 120 to 370 q/L; CMC = 980 to 3100 ug/L)F

5-13 19-495 >llOO 94 ?

86 50-75 SG F ? 25 24

SG F ? 25 24 SG F No 25 24 Stevens and Chapman 1984 Stevens and Chapman 1984 Stevens and Chapman 1984 7.3 7.2 7.0 8.2 7.4 6.3' 6.7 6.0' 6.2' Chapman 1993 Chapman 1993 Chapman 1993 Chapman 1993 Chapman 1993 Chapman 1993

7.6 Adelnan and Smith 1976 7.4 Spehar and Fiandt 1986 42 54 3 DH R Yes 206 166 114 61 ? DN R Yes 52 45 16840 26 3 DM S No <51 9 26267 32 ? OH S No 110 9 27416 27 7 DH S No 96 10 58665 23 ? Dl4 S No 190 25

CHROMIlJM(VI~ (Freshwater: CCC = 11 Ug/L; CMC = 16 ug/L) >25,000 100 1 FH,GF F Yes 220 214 43,300 99.5 4 Fn F No 44 43

CQPPEB (Freshwater: 10-30 40-200 30-100 100-200 20-200 40-300 lo-80 74 3

78 ? 79 ? 02 ? 06 3 87 ? 89 ? ccc = 6.5 to 21 ug/L; CHC = 9.2 to 34 ug/L)'

CT F No 27 20 7.0 Chakoumakos et al. 1979 CT F No 154 20 6.8 Chakoumakos et al. 1979 CT F No 74 23 7.6 Chakourakos et al. 1979 CT F No 192 72 7.0 Chakoumakos et al. 1979 CT F No 31 78 8.3 Chakounakos et al. 1979 CT F No 83 70 7.4 Chakoumakos et al. 1979 CT F No 25 169 8.5 Chakoumakds et al. 1979

7300-1300

100-400 92 ?

94 ? 125-167 2 CT

CT 3-4J 12-91' 18-19 20’ 50 175’ 79-84 3

95 2 95 1 96 2 91 2 CD CD DA DA FBI F?l
5-52 >82’ ? Fn 6-80 83O ? cs
6.7 57 3 Dn 35 43 ? D?l 13 73 3 DM 16 57 ? DH 51 39 ? Dl4 32 53 ? DI4 33 52 3 Dn 39 64 ? DH
25-84 96 14 El4,GM 17 91 6 DM 120 88 14 SC 15-90 74 19
12-162 80’ 3
28-58 85 6 26-59 79 7 56,101 86 2 ? BG DBl Dn DM F

F R R S R S R F F S S R R R S S S S S S S F R R R No 195 160 7.0 Chakoumakos et al. 1979 No 70 174 8.5 Chakoumakos et al. 1979 Yes 31 38 7.2 Carlson et al. 1986a,b Yes 31 38 7.2 Carlson et al. 1986a,b No 52 55 7.7 Carlson et al. 1986b No 31 38 7.2 Carlson et al. 1986b No 52 55 7.7 Carlson et al. 1986b No 31 38 7.2 Carlson et al. 1986b Ye& 47 43 8.0 Lind et al. 1978 No 21 19 7.1 Finlayson and Verrue 1982 No 49 37 7.7 Chapman 1993 Yes 48 39 7.4 Chapman 1993 Yes 211 169 8.1 Chapman 1993 Yes 51 44 7.6 Chapman 1993 Yes 104 83 7.8 Chapman 1993 No 52 45 7.8 Chapman 1993 No 105 79 7.9 Chapman 1993 No 106 82 8.1 Chapman 1993 No 50 No 52 No 48 No 48 7.7 Call et al. 1982 Ye& 45

168 168 168 40

43 47 47 43 117 117 117 7.0 Hammermeister et al. 1983 7.3 Hauermeister et al. 1983 7.3 Hamermeister et al. 1983

7-8 Benoit 1975 No Ye&’ YesN 8.0 Lazorchak 1987 8.0 Lazorchak 1987 8.0 Lazorchak 1987

896 86 4

160 94 1 230-3000 >69->79 3

17 181 193 612 952 1907 7-29
34 58 119 235 474 4100
2100 (Freshwater: CCC = 1.3 to

9 ? 18 ? 25 ?
29 ?
33 -38 I
10 3
62’ 3 68H ? 71H 75n 9 81” ? 82’ 3
79 7 DM DM DM DM DH D?4 EZ BT BT BT BT BT BT Fn
220-2700 96 14 Fn,GM,DH 580 95 14 SG FM FH CR

m (Freshwater: C&K = 2.4 ug/L) F No S No F No
7.7 ug/L; CMC R Yes R Yes R Yes S No S No S No R No F Yes F Yes F Yes F Yes F Yes F No F- No S No S No

172 73 1 FM F No 44 203 17

= 34 43 7.4 Spehar and Fiandt 1986 171 8.2 Geckler et al. 1976 13 7.6 Rice and Harrison 1983 to 200 ug/L)F
52 47 7.6 Chapman 1993 102 86 7.8 Chapman 1993 151 126 8.1 Chapman 1993
50 100 150
22
44 44 44 44 44 44
44
49 51

44 -- -w- Chapman 1993

-- --- Chapman 1993

-- --- Chapman 1993

a- --s JRB Associates 1983
43 7.2 43 7.2 43 7.2 43 7.2 43 7.2 43 7.2
43 7.4
44 7.2 48 7.2 Holcombe et al. 1976

Holcombe et al. 1976 Holcombe et al. 1976 Holconbe et al. 1976 Holcombe et al. 1976 Holcombe et al. 1976 Spehar and Fiandt 1986 Hammermeister et al. 1983 Hamermeister et al. 1983

43 7.4 Spehar and Fiandt 1986(Freshwater: CCC = 88 to 280 ug/L; CMC = 790 to 2500 ug/L)'
DH R Yes 51 49 7.4 Chapman 1993 on R Yes 107 87 7.8 Chapman 1993 DH R Yes 205 161 8.1 Chapman 1993 21 150 578 81

76 87 ?
645 88 DM 1809 93 9 DM 1940 92 3 Dl4 2344 100 DH S No 54 43 7.7 Chapman 1993 S No 51 44 7.7 Chapman 1993 S No 104 04 8.2 Chapman 1993 S No 100 84 7.9 Chapman 1993
4000 90 3 PK R No 21 -- --- JRB Associates 1983

m (FRESHWATER: CCC = 5 ug/L; cwc = 20 ug/L) No data are available.

sILvER (Freshwater: CK = 1.2 t0 13 ug/L; a CCC is not available) 0.19 74 ? DM S No 9.98 13 3 DU S Yes
4.0 4.0 DM S No DU S Yes
3 2-54 2-32 4-32 5-89 6-401 41

11 ; 79 3 79 3 ; 91 1 90 ? 93 ? FM S No

FM S Yes0 Fn S No FM S No Fn S No FH S No 47 37 7.6 Chapman 1993 47 37 7.5 Chapman 1993
36 25 7.0 Nebeker et al. 1983 36 25 7.0 Nebeker et al. 1983 51 49 8.1 uws 1993 49 49 7.9 uws 1993 50 49 8.1 uws 1993 48 49 8.1 uws 1993 120 49 8.2 uws 1993 249 49 8.1 uws 1993

10ZINC (Freshwater: CCC = 59 to 190 ug/L; cnc 65 to 210 ug/L)F

52 31 62 77 191 77 356 74 551 78 741 76 7' 71-129 18-273' 81-107 167' 180 99

94 188-393' 551 100

100 40-500 95O 1940 100 5520 83 <4000 >4000 90

70 160-400 103 240 96 

## ?

? 3 ? P

2 2
2 1 2 1 ? ? ? 3 3 13 13 DM

DM DM DM DU Dn CD CD CD CD FM Fn

cs AS AS F?! FH FI¶,GM,DH SG R

R R S S S R R R S R S F F F F F S S Yes 211 169 8.2 Chapman 1993 Yes 104 83 7.8 Chapman 1993 Yes 52 47 7.5 Chapman 1993 No 54 47 7.6 Chapman 1993 No 105 85 8.1 Chapman 1993 No 196 153 8.2 Chapman 1993 Yes 31 38 7.2 Carlson et al. 1986b Yes 31 38 7.2 Carlson et al. 1986b No 31 38 7.2 Carlson et al. 1986b No 52 55 7.7 Carlson et al. 1986b No 31 38 7.2 Carlson et al. 1986b No 52 55 7.7 Carlson et al. 1986b No 21 19 7.1 Finlayson and Verrue 1982 No 20 12 7.1 Sprague 1964 No 20 12 7.9 Sprague 1964 No 204 162 7.7 Mount 1966 No 204 162 7.7 Mount 1966 No 52 43 7.5 Hammermeister et al. 1983 No 49 46 7.2 Haamermeister et al. 1983

A Total recoverable concentration. B Except as noted, a 0.45-pa membrane filter was used.

11

# Y 0) Ll

3 f co a u 0 t-l d 0 d d 4 -4

a 

# & a:References

Adelman, I.R., and L.L. Smith, Jr. 1976. Standard Test Fish Development. Part I. Fathead Minnows (PimeDhales promelag) and Goldfish (Carassiu guratus) as Standard Fish in Bioassays and Their Reaction to Potential Reference Toxicants. EPA-600/3-76- 061a. National Technical Information Service, Springfield, VA. Page 24. Benoit, D.A. 1975. Chronic Effects of Copper on Survival, Growth, and Reproduction of the Bluegill (Lepomis macrochims). Trans. Am. Fish. Sot. 104:353-358. Brungs, W.A., T.S. Holderman, and M.T. Southerland. 1992. Synopsis of Water-Effect Ratics for Heavy Metals as Derived for Site-Specific Water Quality Criteria. Call, D.J., L.T. Brooke, and 0.0. Vaishnav. 1982. Aquatic Pollutant Hazard Assessments and Development of a Hazard Prediction Technology by Quantitative Structure-Activity Relationships. Fourth Quarterly Report. University of Wisconsin-Superior, Superior, WI. Carlson, A.R., H. Nelson, and 0. Hammsrmeister. 1986a. Development and Validation of Site-Specific Water Quality Criteria for Copper. Environ. Toxicol. Chem. 5:997-1012. Carlson, A.R., H. Nelson, and D. Hammermeister. 1986b. Evaluation of Site-SpedLiz Crft.eria for Capper and Zinc: An Integration of Metal Addition Toxicity, Effluent and Receiving Water Toxicity, and Ecological Survey Data. EPA/600/S3-86-026. National Technical Information Service, Springfield, VA. Carroll, J.J., S.J. Ellis, and W.S. Oliver. 1979. Influences of Hardness Constituents on the Acute Toxicity of Cadmium to Brook Trout (Salvelinus fontinalis). Chakoumakos, C., R.C. Russo, and R.V. Thurston. 1979. Toxicity of Copper to Cutthroat Trout (Salmo clarki) under Different Condition8 of Alkalinity, pH, and Hardness. Environ. Sci. Technol. 13;213-219. Chapman, G.A. 1993. Memorandum to C. Stephan. Junm 4. Davies, P.H., 

### J.P. Goettl, Jr., J.R. Sinley, and N.F. Smith. 1976. Acute and Chronic Toxicity of Lead to Rainbow Trout SaLmo gairdneri, in Hard and Soft Water. Water Re8. 10:199-206. Finlayson, B.J., and 

### K.M Verrue. 1982. Toxicities of Copper, Zinc, and Cadmium Mixtures to Juvenile Chinook Salmon. Trans. Am. Fish. Sot. 111:645-650. 13Geckler, J.R., W.B. Horning, T.M. Neiheisel, Q.H. Pickering, E.i,.

Robinson, and C.E. Stephan. 1976. Validity of Laboratory Tests for Predicting copper Toxicity in Streams. EPA-600/3-76-116. National Technical Information Service, Springfield, VA. Page 118. Grunwald, 0. 1992. Metal Toxicity Evaluation: Review, Results, and Data Base Documentation. Hammermeister, D., C. Northcott, L. Brooke, 

### and 0. Call. 1983. Comparison of Copper, Lead and Zinc Toxicity to Four Animal Species in Laboratory and ST. Louis River Watrr. University of Wisconsin-Superior, Superior, WI. Hansen, D.J. 1993. Memorandum to C.E. Stephan. April 15. Holcombe, G.W., D.A. Benoit, E.N. Leonard, and J.M. McKim. 1976. Long-Term Effects of Lead Exposure on Three Generations of Brook Trout (SalveLinus fontfnalfs). J. Fish. Res. Bd. Canada 33:1731- 1741. Holcombe, G.W., and R.W. Andrew. 1970. The Acute Toxicity of Zinc to Rainbow and Brook Trout. EPA-600/3-78-094. National Technical Information Service, Springfield, VA. Horowitz, A.J., 

### K.A. Elrick, and M.R. Colbsrg. 1992. The Effect of Membrane Filtration Artifacts on Dissolved Trace Element Concentrations. Water Res. 26:753-763. Howarth, R.S., and J.B. Sprague. 1978. Copper Lsthality to Rainbow Trout in Waters on Various Hardness and pH. Water Res. 12:455-462. JRB Associates. 1983. Demonstration of the Site-specific Criteria Modification Process: Selser's Creek, Ponchatoula, Louisiana. Lazorchak, J.M. 1987. The Significance of Weight Loss of ehz Straus During Acute Toxicity Tests with Copper.

. . . Lima, A.R., C. Curtis, D.E. Hammermeister, T.P. Markee, C.E. Northcott, L.T. Brooke. 1984. Acute and Chronic Toxicities of Arsenic(II1) to Fathead Minnows, Flagfish, Daphnids, 

### and an Amphipod. Arch. Environ. Contam. Toxicol. 13:595-601. Lind, D., K. Alto, 

### and S. Chatterton. 1978. Regional CopperNickel Study. Draft. Mount, 0.1. 1966. The Effect of Total Hardness and pH on Acute Toxicity of Zinc to Fish. Air Water Pollut. Int. J. 10:49-56.
14Nebeker, A.V., C.K. McAuliffe, R. Msher, and D.G. Stevens. 1983.

Toxicity of Silver to Steelhead and Rainbow Trout, Fathead Minnows, and Daphnia magna. Environ. Toxicol. Chem. 2:9S-104. Pickering, Q.P., and M.H. Gast. 1972. Acute and Chronic Toxicity of Cadmium to the Fathead Minnow (Pimephales promelas). J. Fish. Res. Bd. Canada 29:1099-1106. Rice, D.W., Jr., and F.L. Harrison. 1983. The Sensitivity of Adult, Embryonic, and Larval Crayfish Procambarus clarkii to Copper. NUREG/CR-3133 or UCRL-53048. National Technical Information Service, Springfield, VA. Schuytema, G.S., P.O. Nelson, K.W. Malueg, A.V. Nebeker, D.F. Krawczyk, A.K. Ratcliff, and J.H. Gakstatter. 1984. Toxicity of Cadmium in Water and Sediment Slurries to Daphnia magna. Environ. Toxicol. Chem. 3:293-308. Spehar, R.L., R.L. Anderson, and J.T. Fiandt. 1978. Toxicity and Bioaccumulation of Cadmium and Lead in Aquatic Invertebrates. Environ. Pollut. lS:l95-208. Spehar, R.L., and A.R. Carlson. 1984. Derivation of SiteSpecific Water Quality Criteria for Cadmium and the St. Louis River Basin, Duluth, Minnesota. Environ. Toxicol. Chem. 3:6Sl665. Spehar, R.L., and J.T. Fiandt. 1986. Acute and Chronic Effects of Water Quality Criteria-Based Metal Mixtures on Three Aquatic Species. Environ. Toxicol. Chem. S:917-931. Sprague, J.B. 1964. Lethal Concentration of Copper and Zinc for Young Atlantic Salmon. J. Fish. Res. Bd. Canada 21317-9926. Stevens, D.G., and G.A. Chapman. 1984. Toxicity of Trivalent Chromium to Early Life Stages 

### of Steelhead Trout. Environ. Toxicol. Chem. 3:125-133. University of Wisconsin-Superior. 1993. Preliminary data from work assignment l-10 

### for Contract No. 680Cl-0034.

15ATTACHMENT #3

GUIDANCE DOCUMENT ON DYNAMIC MODELING AND TRANSLATORS August 1993

Total Maximum

Daily Loads (TMDLs) and Permits

o Dynamic Water Quality Modeling Although not specifically part of the reassessment of water quality criteria for metals, dynamic or probabilistic models are another useful tool for implementing water quality criteria, especially those for protecting aquatic life. Dynamic models make best use of the specified magnitude, duration, and frequency of water quality criteria and thereby provide a more accurate calculation of discharge impacts on ambient water quality. In contrast, steadystate modeling is based on various simplifying assumptions which makes it less complex and less accurate than dynamic modeling. Building on accepted practices in water resource engineering, ten years ago OW devised methods allowing the use of probability distributions in place of worst-case conditions. The description of these models and their advantages and disadvantages is found in the 1991 Technical Support Document for Water Quality-based Toxic Control (TSD). Dynamic models have received increased attention in the last few years as a result of the perception that static modeling is over-conservative due to environmentally conservative dilution assumptions. This has led to the misconception that dynamic models will always justify less stringent regulatory controls (e.g. NPDES effluent limits) than static models. In effluent dominated waters where the upstream concentrations are relatively constant, however, a dynamic model will calculate a more stringent wasteload allocation than will a steady state model. The reason is that the critical low flow required by many State water quality standards in effluent dominated streams occurs more frequently than once every three years. When other environmental factors (e.g. upstream pollutant concentrations) do not vary appreciably, that the overall return frequency of the steady state model may be greater than once in three years. A dynamic modeling approach, on the other hand, would be more stringent, allowing only a once in three year return frequency. As a result, EPA considers dynamic models to be amore accurate rather than a less stringent approach to implementing water quality criteria.
The 1991 TSD provides recommendations on the use of steady state and dynamic water quality models. The reliability of any modeling technique greatly depends on the accuracy of the data used in the analysis. Therefore, the selection of a model also depends upon the data. EPA recommends that steady state wasteload allocation analyses generally be used where few or no whole effluent toxicity or specific chemical measurements are available, or where daily receiving water flow records are not available. Also, if staff resources are insufficient to use and defend the use of dynamic models, then steady statemodels may be necessary. If adequate receiving water flow and effluent concentration data

are available to estimate frequency distributions, EPA recommends that one of the dynamic wasteload allocation modeling techniques be used to derive wasteload allocations which will more exactly maintain water quality standards. The minimum data required for input into dynamic models include at least 30 years of river flow data and one year of effluent and ambient pollutant concentrations.

o Dissolved-Total Metal Translators
When water quality criteria are expressed as the dissolved form of a metal, there is a need to translate TMDLs and NPDES permits to and from the dissolved form of a metal to the total recoverable form. TMDLs for toxic metals must be able to calculate 1) the dissolved metal concentration inorder to ascertain attainment of water quality standards and 2) the total recoverable metal concentration in order to achieve mass balance. In meeting these requirements, TMDLs consider metals to be conservative pollutants and quantified as total recoverable to preserve conservation of mass. The TMDL calculates the dissolved or ionic species of the metals basal on factors such as total suspended solids (TSS) and ambient pH. (These assumptions ignore the complicating factors of metals interactions with other metals.) In addition, this approach assumes that ambient factors influencing metal partitioning remain constant with distance down the river. This assumption probably is valid under the low flow conditions typically used as design flows for permitting of metals (e.g., 7Q10, 4B3, etc) because erosion, resuspension, and wet weather loadings are unlikely to be significant and ever chemistry is generally stable. In steady-state dilution modeling, metals releases may be assumed to remain fairly constant (concentrations exhibit low variability) with time.
EPA’s NPDES regulations require that metals limits in permits be stated as total recoverable in most cases (see 40 CFR §122.45(c)). Exceptions occur when an effluent guideline specifies the limitation in another form of the metal or the approved analytical methods measure only the dissolved form. Also, the permit writer may express a metals limit in another form (e.g., dissolved, valent, or total) when required, in highly unusual cases, to carry out the provisions of the CWA.
The preamble to the September 1984 National Pollutant Discharge Elimination System Permit Regulations states that the total recoverable method measures dissolved metals plus that portion of solid metals that can easily dissolve under ambient conditions (see 49 Federal Register 38028, September 26, 1984). This method is intended to measure metals in the effluent that are or may easily become environmentally active, while not measuring metals that are expected to settle out and remain inert.
The preamble cites, as an example, effluent from an electroplating facility that adds lime and uses clarifiers. This effluent will be a combination of solids not removed by the clarifiers and residual dissolved metals. When the effluent from the clarifiers, usually with ahigh pH levei, miXcS with receivingwater havingsignificantly lower pH level, thesesolids instantlydissolve. Measuringdissolvedmetalsin the effluent, in this case,would underestimate

the impacton the receivingwater. Measuringwith the total metalsmethod,on the other hand,would measure metalsthatwould be expected to disperse

or settleout and remain inert or be coveredover. Thus, measuring total recoverable

metalsin the effluent bestapproximates

the amountof metal likely to producewaterquality impacts. However, the NPDESrule dots not require in any way that Statewater quality standards be in the total recoverable

form; rather, the rule rcquircspermit writers to consider the translationbetween

differing metalforms in the calculationof the permit limit sothata total razoverable

limit canbc established.Therefore, both theTMDL and NPDES uses of waterquality criteria requiretheability to translate from the dissolvedform andthe total recoverable

form. Many toxic substances,

including metals,havea tendency to leavethe dissolved

phase andattachto suspended

solids. The partitioning of toxicsbetweensolid anddissolved phases canbe determined

asa functionof a pollutant-specific partition coefficient andthe concentration

of solids. This function is expressed by a linear partitioning quation:

Cf % 1+K,W10-‘ where,

C - dissolved

phase metal conocntration, C, = total metalconcentration, TSS = total suspended

solidsconcentration,

and I& = partition coefficient.

A key assumption

of the linear partitioningquation is thatthe sorption reaction reaches dynamicquilibrium at the point of applicationof the criter& that is, after allowing for initial mixing the partitioningof the~llutant between the adsorbed

anddissolved

foms canbe usedat any locationto predictthefraction of pollutant in eachrespective phase. SuccesW applicationof the linearpartitioning equationrelies on the selection of the partition coefficient. The useof a partition coefficientto rcprcmt the degreeto which toxicsadsorbto solidsis mostreadily appliedto organicpollutants; partition coefficientsfor metals are moredifficult to define. Metalstypically exhibit morecomplexspeciation and complexationreactions

thanorganicsand the degree of partitioning canvary greatly dependinguponsite-specific waterchemistry. Estimated partition coefficientscanbe detcrmincdfor a numberof metals,but waterbodyor site-specific observations

of dissolved and adsorbed concentrations arc prcferrcd.EPA suggests threeapproaches

for instances

wherea waterquality criterion for a metalis express@

in the dissolved

form in a State’swaterquality standards: 1. Using cleananalyticaltechniques andfield samplingprocedures with appropriate QA/QC, collect receivingwatersamples and determine site specificvaluesof IC,, for eachmetal. UsetheseI(d values to “translate’ between

total recoverable

and dissolvedmetalsin receivingwater. This approach is moredifficult to apply because it relies uponthe availability of goodquality mca&rcmcnts of ambientmetal concentrations.This approach providesan accurate

assessment

of the dissolvedmetal fraction providing sufficient samples arccollected. EPA’s initial rccommcndation is thatat leastfour pairs of total recoverable anddissolved

ambientmetal mcasurcmcnts bc madeduring low flow conditionsor 20 pairs overall flow conditions. EPA suggests that theaverage

of datacollected

during low flow or the 95th percentile highestdissolved

fraction for all flows be used. The low flow average providesa representative

picture of conditionsduring the rare low flow events. The 95th percentilehighestdissolved fraction for all flows providesa critical condition approach analogous to the approach

used to identify low flows andother critical environmental

conditions. 2. Calculatethetotal recoverable concentration

for the purpose

of settingthe permit limit. Usea valueof I unless the permitteehascollecteddata(see#l above)to show thata different ratio shouldbe used. Thevalueof 1 is conservative andwill not err on the sideof violating standards.This approach is very simpleto apply because it places the entire burdenof datacollectionand analysis solely uponpermitted facilities. In termsof technicalmerit, it hasthesame characteristics

of the previous approach. However,permittingauthoritiesmay befacedwith difficulties in negotiatingwith facilities on theamountof datanecessary to determinethe ratio and the necessary

quality control methods

to assure thatthe ambientdataare reliable. 3. Usethe historicaldataon total suspended solids(TSS)in receivingwaterbodies at appropriatedesignflows and & valuespresented in theTechnicalGuidanceManual for PerformingWasteLnad Allocations. Book II. SW andRivers. EPA-440/4- 84-020(1984)to “translate’ bctwecn(total recoverable) permitslimits anddissolved metalsin receivingwater. This approach is fairly simpleto apply. Howcvcr, these & values are suspect

dueto possible

quality assurance

problemswith thedata usedto developthevalues. EPA’s initial analysis of this approach

andthesevaluesin one site indiw thattheseK,,valuesgenerallyoverutimate thedissolvedfraction of metalsin ambientwaters(seeFiguresfollowing). Therefore,althoughthis approach may not providean accurate estimate of the dissolved

fraction, the bias in the estimate is likely to be a conSerYative one. EPA suggests

that regulatoryauthoritiesuseapproacha I1 and#2 whereStates express their waterquality standards in thedissolved

form. In thoseStates

wherethe standards arc in thetotal recoverable or acid solubleform, EPA recommends that notranslationbe useduntil thetime that theStatechanges the standards

to thedissolvedform. Approach #3 maybe usedasan interim measure until thedataare COktcd to implement approach #1.ma8au.A VB. 

### ~tobslad DitmolveA Coppar Concentrations

3.5
3

2.5

2 Ii P

- 1.5

1


### 0.5

0 -_-- -. --

0 5 10 IS 20 25 30 35 40 45 SIlnplhlg station0.16

0.14

0.12

0.1 Ii 2 0.08

0.08

0.04

0.02

0 

### 0 5 10 1s 20 2s 30 35 40 4s Sampling Station 

### numard tm. Ilodolod Dissolved 

### CadmiumConcontrrtioam

_. .----.- Modeled

-- 0 Measured1.6

1.4

1.2

1 

### th j 0.6
-- 0.6

0.4

0.2 no8mar.d V8 l 

### Hodold Dio8olvob Lord Concentrations

I- . Modeled II Measured



### 0 0 5 10 15 20 25 30 35 40 

### 4s Sampling Shlion0.12

0.1

0.06

s jj 0.06

0.04

0.02 

# I

I 

### nu8wod va. 8toUrlod 

### Dissolved Worcury Concentrrtfonr

0 5 10 15 20 25 30 35 40 4s Samplittg Station7

6

S

4 ii =3

2

1 

### Womurd vm. Mob.106 Dimolvod Nick.1 

### Cormcntrattonm

O,----+ -+--------t-----------t0 S 10 lS e 20 2s 30 35 Sampling Station -- l Modeled

0 Measured L--_-

---t--- --- ---4 40

. 4s

### 30

2s

20

3 15

-

10

5 

### @-aura VII. W~cslob Dim~olveb 2iac Concontratfons

--+-

_ 0 s 10 15 20 25 30 Smpldng SWlon Modeted Measured
I

- I 35 I

40 I

45(i/WATTACHMENT #4

GUIDANCE DOCUMENT ON CLEAN ANALYTICAL TECHNIQUES AND MONITORING October 1993

Guidance on Monitoring

o Use of Clean Sampling and Analytical Techniques Appendix B to the WER guidance document (attached) provides some general guidance on the use of clean techniques. The Office of Water recommends that this guidance be used by States and Regions as an interim step while the Office of Water prepares more detailed guidance.

o Use of Historical DMR Data
With respect to effluent or ambient monitoring data reported by an NPDES permittee on a Discharge Monitoring Report (DMR), the certification requirements place the burden on the permittee for collecting and repotting quality data. The certification regulation at 40 CFR 122.22(d) requires permittees, when submitting information, to state: “I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gather and evaluate the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations.” Permitting authorities should continue to consider the information reported in DMRs to be true, accurate, and complete as certified by the permittee. Under 40 CFR 122.41(1)(8), however, as soon as the permittee becomes aware of new information specific to the effluent discharge that calls into question the accuracy of the DMR data, the permittee must submit such information to the permitting authority. Examples of such information include a new finding that the reagents used in the laboratory analysis are contaminated with trace levels of metals, or a new study that the sampling equipment imparts trace metal contamination. This information must be specific to the discharge and based on actual measurements rather than extrapolations from reports from other facilities. Where a permittee submits informationIn addition to submitting the Information described above, the permittee also must

develop procedures to assure the collection and analysis of quality data that are true, accurate, and complete. For example, the permittee may submit a revised quality assurance plan that describes the specific procedures to be undertaken to reduce or eliminate trace metal contamination.10-l-93

Appendix B. Guidance Concerning 

### the Use of "Clean T8chniquesoo and

QA/QC in the Measurement of Trace Metals
Recent information (Shiller and Boyle 1987; Windom et al. 1991) has raised questions concerning the quality of reported concentrations of trace metals in both fresh and salt (estuarine and marine) surface waters. A lack of awareness of true ambient concentrations of metals in saltwater and freshwater systems can be both a cause and a result of the problem. The ranges of dissolved metals that an typical in 

### surface waters of the United States away from the immediate influence of discharges (Bruland 1983; Shiller and Boyle 1985,1987; Trefry et al. 1986; Windom et al. 1991) are:

Metal Salt water Fresh Water f UU/T,l (UU/f‘l Cadmium 0.01 to 0.2 0.002 to 0.08 Copper 0.1 to 3. 0.4 to 4. Lead 0.01 to 1. 0.01 to 0.19 Nickel 0.3 

### to 5. 1. to 2. Silver 0.005 to 0.2 -------w----- Zinc 0.1 to 15. 0.03 to 5. The U.S. EPA (1983,1991) has published analytical methods 

### for monitoring metals in waters and wastewaters, but these methods are inadequate for determination of ambient concentrations of some metals in some surface waters. Accurate 

### and precise measurement of these low concentrations requires appropriate attention to seven areas: 1.
2. 3. use of 

### “clean techniques e during collecting, handling, storing, preparing, and analyzing samples to avoid contamination. Use of analytical methods that have sufficiently low detection limits. Avoidance of interference in the quantification (instrumental analysis) step. 4. 5. 6. 7. In Use of blanks to assess contamination. Use of matrix spikes (sample spikes) and certified reference materials (CRMe) to assess interference and contamination. Use of replicator to assess precision. Use of certified standards. a strict sense, the term "clean techniques" rafmre to techniques that reduce contamination and enable the accurate and precise measurement of trace metals in fresh and salt surfaco waters. In a broader sense, the term also refers to related issues concerning detection limits, quality control, and quality assurance. Documenting data quality demonstrates the amount 

### of confidence that can be placed in the data, whereas increasing the sensitivity of methods reduce the problem of deciding how to 1interpret results that are reported to be below detection limits.

. This auoenQirc 1s written for those analytical laboratories that want auidqace concerninu wavs to lower detection limits, increase

. gr 1s~ n. and/ r increase accuracvL The ways to achieve these goE?s aze to i&ease the sensitivity of the analytical methods, decrease contamination, and decrease interference. Ideally, validation of a procedure for measuring concentrations of metals in surface water requires demonstration that agreement can be obtained using completely different procedures beginning with the sampling step and continuing through the quantification step (Bruland et al. 1979), but 

### few laboratories have the resources to compare two different procedures. Laboratories can, however, (a) use techniques that others have found useful for improving detection limits, accuracy, and precision, and (b) document data quality through use of blanks, spikes, CR?&, replicates, and standards. In general, in order to achieve accurate and precise measurement of a particular concentration, both the detection limit and the blanks should be less than one-tenth of that concentration. Therefore, the term t'metal-free8t can be interpreted to mean that the total amount of contamination that occurs during sample collection and processing (e.g., from gloves, sample containers, labware, sampling apparatus, cleaning solutions, air, reagents, etc.) is sufficiently low that blanks 

### are lese than one-tenth of the lowest concentration that needs to be measured. Atmospheric particulate8 can be a major source of contamination (Moody 1982; Adeloju and Bond 1985). The term nclase-lOOm refers to 

### a specification concerning the amount of particulate8 in air (Moody 1982); although the specification 

### says nothing about the composition of the particulates, generic control of particulates can greatly reduce trace-metal blanks. Except during collection of samples and initial cleaning 

### of equipment, all handling of samples, sample containers, labware, and sampling apparatus should be performed in a class-100 bench, room, or glove box.

. subtracts from w raw 

### rewts set forth j,~ otm EPA documents concer&a metal anuses, The word 

### nmuet* is used in this appendix merely to indicate items that are considered very important by analytical chemists who have worked to 

### increase accuracy and precision and lower detection limits 

### in trace-metal analysis. Some items are considered important because they have been found to have received inadequate attention in eoma laboratories performing trace-metal analyses. Two topics that are not addressed in this appendix are: 1. The @'ultraclean techniques n that are likely to be necessary when trace analyses of mercury are performed. 2. Safety in analytical laboratories. 2Other documents should be consulted if these topics are of

concern. Fvoidinu contamination bv use of "clean technicrues" Measurement Of trace metals in receiving waters rust take into account the potential for contamination during each step in the 

### process. Regardless of the specific procedures used 

### for collection, handling, storage, preparation (digestion, filtration, and/or extraction), and quantification (instrumental analysis), the general principles of contamination control must be applied. Some specific recommendations are: a. NoWtalc latex or class-100 polyethylene gloves must be worn during all steps from sample collection to analysis. (Talc seems to be a particular problem with zinc; gloves made with talc cannot be decontaminated sufficiently.) Gloves should only contact surfaces that are metal-free; gloves should be changed if even suspected 

### of contamination. b. The acid used to acidify samples for preservation and digestion and to acidify water for final cleaning of labware, sampling apparatus, and sample containers 

### must be metal-free. The quality of the acid used should be better than reagentgrade. Each lot of acid must be analyzed 

### for the metal(s) of interest before use. c. The water used to prepare acidic cleaning solutions and to rinse labware, sample containers, and sampling apparatus may be prepared by distillation, deionization, or reverse osmosis, and must be demonstrated to be metal-free. d. The work area, including bench tops and hoods, should be cleaned (e.g., washed and wiped dry with lint-free, class-100 wipes) frequently to remove contamination. e. All handling 

### of samples in the laboratory, including filtering and analysis, 

### must be performed in a class-100 clean bench or a glove box fed by particle-free air or nitrogen; ideally the clean bench or glove box should be located within 

### a class-100 clean room. f. Labware, reagents, sampling apparatus, and sample containers must never be left open to the atmosphere; they should be stored in a class-100 bench, covered with plastic wrap, stored in a plastic box, or turned upside down on a clean surface. Minimizing the time between cleaning and using will help minimito contamination. g. Separate sets of sample containers, labware, and sampling apparatus should be dedicated for different kind8 of samples, e.g., rec8iving water samples, effluent samples, etc. h. To avoid contamination of clean roeme, samples that contain very high concentrations of metals and do not require use of Itclean techniqueen should not be brought into clean rooms. i. Acid-cleaned plastic, such as high-density polyethylene (HDPE) 8 low-density polyethylene (LDPE), or a fluoroplaetic, 

### must be the only material that ever contacts a sample, except possibly during digestion for the total recoverable 3measurement. (Total recoverable samples can be digested in

some plastic containers.) Even HDPE and LOPE might not be acceptable for mercury, however. j. ~11 labware, sample containers, and sampling apparatus must be acid-cleaned before use or reuse. 1. Sample containers, sampling apparatus, tubing, membrane filters, filter assemblies, and other labware must be soaked in acid until metal-free. The amount of cleaning necessary might depend on the amount of contamination and the length of time the item will be in contact with samples. For example, if an acidified sample will be stored in a sample container for three weeks, ideally the container should have been soaked in an acidified metalfree solution for at least three weeks. 2. It might be desirable to perform initial cleaning, 

### for which reagent-grade acid may be used, before the items are allowed into a clean room. For most metals, 

### items should be either (a) soaked in 10 percent concentrated nitric acid at SOOC

### for at least one hour, or (b) soaked in SO percent concentrated nitric acid at room temperature for at least two days; for arsenic and mercury, soaking for up to two weeks at 50°C in 10 percent concentrated nitric acid might be required. For plastics that might be damaged by strong nitric acid, such as polycarbonate and possibly HDPE and LDPE, soaking in 10 percent concentrated hydrochloric acid, either in place of or before soaking in a nitric acid solution, might be desirable. 3. Chromic acid muet not be used to clean items that will be used in analysis of metals. 4. Final soaking and cleaning of sample containers, labware, and sampling apparatus must be performed in a claee-100 clean room using metal-free acid and water. The solution in an acid bath must be analyzed periodically to demonstrate that it is metal-free. 5. After labware and sampling apparatus are cleanad, they may be stored in a clean room in a weak acid bath prepared using metal-free acid and water. Before use, the items should be rinsed at least three times with metal-free water. After the final rinse, the items should be moved immediately, with the open end pointed down, to a class-100 clean bench. Items may be dried on a class-100 clean bench; items rust not be dried in an oven or with laboratory towels. The sampling apparatus should ba assembled in a class-100 clean room or banch and doublebagged in metal-free polyethylene zip-type bag8 for transport to the field; new bags are usually natal-free. 6. After sample containers are cleaned, they should ba filled with metal-'free water that has been acidified to a pH of 2 with metal-free nitric acid (about 0.5 mL per liter) for storage until use. At the time of S?&mpl@ collection, the sample containers should be emptied and rinsed at least twice with the solution being sampled before the actual 4sample is placed in the sample container.

k. Field samples must be collected in a manner that eliminates the potential for contamination from the sampling platform, probes, etc. Exhaust from boats and the direction of wind and water currents should be taken into account. The people who collect the samples must be specifically trained on how to collect field samples. After collection, all handling of samples in the field that will expose the sample to air must be performed in a portable class-100 clean bench or glove box. 1. Samples must be acidified (after filtration if dissolved metal is to be measured) to a pH of less than 2, except that the pH must be less than 1 

### for mercury. Acidification should be done in a clean room or bench, and so it might bo desirable to wait and acidify samples in a laboratory rather than in the field. If samples are acidified in the field, Fetal-free acid can be transported in plastic bottles and poured into a plastic container from which acid can be removed and added to samples using plastic pipettes. Alternatively, plastic automatic dispensers can be used. HI. Such things as probes and thermometers 

### must not be put in samples that are to be analyzed for metals. In particular, pH electrodes and mercury-in-glass thermometers rust not be used if mercury is to be measured. If pH is measured, it 

### must be done on a separate aliquot. n. Sample handling should be minimized. For example, instead of pouring a sample into a graduated cylinder to measure the volume, the sample can be weighed after being poured into a tared container; alternatively, the container from which the sample is poured can be weighed. (For saltwater samples, the salinity or density should be taken into account when weight is converted to volume.) 0. Each reagent used rust be verified to be metal-fres. If metal-free reagents are not commercially available, removal of metals will probably be necessary. p. 

### For the total recoverable measursment, samples should be digested in 

### a class-100 bench, not in a metallic hood. If feasible, digestion should be done in the sample container by acidification and hsating. q. The longer the time between collection and analysis of samples, the greater the chance of contamination, loss, etc. r. Samples must be stored in the dark, preferably 

### between 0 and 4OC with no air space in the sample container.

Achievinu low detect&on w a. Extraction of the m&al from the sample can be 

### l xtremsly useful if it simultaneously concentrates the metal and eliminates potential matrix interferenc88. 

### For l xampla, ammonium 1-pyrrolidfnsdithiocarbamate and/or diethylammonium diethyldithiocarbamate can extract cadmium, copper, lead, 5nickel, and zinc (Bruland et al. 1979; Nriagu et al. 1993).

b. The detection limit should be less than ten percent of the lowest concentration that is to be measured. Avoidina interference3
a. Potential interferences nust be assessed for the specific instrumental analysis technique used and each metal to be measured. b. If direct analysis is used, the salt present in high-salinity saltwater samples is likely to cause interference in most instrumental techniques. c. As stated above, extraction 

### of the metal from the sample is particularly useful because it simultaneously concentrates the metal and eliminates potential matrix interferences.

a. A laboratory (procedural, method) blank consists 

### of filling a sample container with analyzed metal-free water and processing (filtering, acidifying, etc.) the water through the laboratory procedure in exactly the same way as a sampls. A laboratory blank must be included in each set of ten or fewer samples to check for contamination in the laboratory, and must contain less than ten percent of the lowest concentration that is to be measured. Separate laboratory blanks must be processed for the total recoverable and dissolved measurements, if both measurements are performed. b. A field (trip) blank consists of filling a sample container with analyzed metal-free water in the laboratory, taking the container to the site, processing the water through tubing, filter, etc., collecting the water in a sampls containar, and acidifying ths water the same as a field sample. A fisld blank must be processed for each sampling trip. Separate field blanks rust be processed for tha total recoverable measurement and for the dissolved measurement, if filtrations are performed at the sits. Field blanks must ba processed in the laboratory the same as laboratory blank8.

Assessina acwacv a. A calibration curve must be determined for each analytical run and the calibration should be checked about every tenth sample. Calibration solutions must be traceable back to a certified standard from the U.S. EPA or ths National Institute of Science and Technology (NIST). b. A blind standard or a blind calibration solution wrt be included in each group of about twenty samples. 6C. Ak least one of the following must be included in each group

of about twenty samples: 1. A matrix spike (spiked sample; the method of known additions). 2. A CPM, if one is available in a matrix that closely approximates that of the samples. Values obtained for the CPMmust be within the published values. The concentrations in blind standards and solutions, spikes, and CRMs must not be more than 5 times the Ledian concentration expected to be present in the samples.

. . Fssessina Drecluan a. A sampling replicate must be included with each set of samples collected at each sampling location. b. If the volume 

### of the sample is large enough, replicate analysis of at least one sample 

### must be performed along with each group 

### of about ten samples.

Whereas the total recoverable measurement is especially subject to contamination during the digestion step, the dissolved measurement is subject to both loss and contamination during the filtration step. a. Filtrations 

### must be performed using acid-cleaned plastic filter holders and acid-cleaned membrane filters. Samples must not be filtered through glass fiber filters, even if the filters have been cleaned with acid. If positive-pressure filtration is used, the air or gas 

### must bs passed through a 0.20um in-line filter; if vacuum filtration is used, it must be performed on a class-100 bench. b. Plastic filter holders must be rinsed and/,or dipped between filtrations, but they do 

### not have to be 

### soaked between filtrations if all the samples contain about the same concentrations of metal. It is best to filter samples from low to high concentrations. A 

### membrane filter 

### au8t sot be used for more 

### than one filtration. After each filtration, the 

### membrane filter must bo removed and discarded, and the filter holder 

### w8t be either rinsed with metal-free water or dilute acid and 

### dipped in a metal-free acid bath or rinsed at least twice with metal-free dilute acid; finally, the filter holder must be rinsed at least twice with metal-free water. C. For each sample to be filtered, the filter holder and membrane filter must be conditioned with the sample, i.e., an initial portion of the sample must be filtered and discarded. The accuracy and precision of the dissolved measurement should be 7assessed periodically. A large volume of a buffered solution

(such as aerated 0.05 N sodium bicarbonate) should be spiked so that the concentration of the metal of interest is in the range of the low concentrations that are to be measured. The total recoverable concentration and the dissolved concentration of the metal in the spiked buffered solution should be measured alternately until each measurement has been performed at least ten times. The means and standard deviations for the two measurements should be the same. All values deleted as outliers must be acknowledged.

penortina regultp To indicate the quality of the data, reports of results of measurements of the concentrations of metals must include a description of the blanks, spikes, CRMs, replicates, and standards that were run, the number run, and the results obtained. All values deleted as outliers must be acknowledged.

The items presented above are some of the important aspects of "clean techniques"; some aspects of quality assurance and quality control are also presented. This is not a definitive treatment of these topics; additional information that might be useful is available in such publications as Patterson and Settle (1976), Zief and Mitchell (1976), Bruland et al. (1979), Moody and Beary (1982), Moody (1982), Bruland (1983), Adeloju and Bond (1985), Berman and Yeats (1985), Byrd and Andreae (1986), Taylor (1987), Sakamoto-Arnold (1987), Tramontano et al. (1987), Puls and Barcelona (1989), Windom et al. (1991), U.S. EPA (1992), Horowitz et al. (1992), and Nriagu et al. (1993).

Adeloju, S.B., and A.M. Bond. 1985. Influence of Laboratory Environment on the Precision and Accuracy 

### of Trace Element Analysis. Anal. Chem. 573172801733. Berman, S.S., and P.A. Yeats. 1985. Sampling of Seawater 

### for Trace Metals. CRC Reviews in Analytical Cbmistry 16:1-14. Bruland, 

### X.W., R.P. Franks, G.A. Knauer, and J.H. Martin. 1979. Sampling and Analytical Methods for the Determination of Copper, Cadmium, Zinc, and Nickel at the Nanogram per Liter Level in Sea Water. Anal. Chim. Acta 105:233-245.Bruland, K.W. 1983. Trace Elements in Sea-water. In: Chemical

Oceanography, Vol. 8. J.P. Riley and R. Chester, eds. Academic Press, New York, NY. pp. 157-220. Byrd, J.T., and M.O. Andreae. 1986. Dissolved and Particulate Tin in North Atlantic Seawater. Marine Chemistry 19:193-200. Horowitz, A.J., K.A. Elrick, and M.R. Colberg. 1992. The Effect of Membrane Filtration Artifacts on Dissolved Trace Element Concentrations. Water Res. 26:753-763. Moody, J.R. 1982. NBS Clean Laboratories 

### for Trace Element Analysis. Anal. Chem. 54:1358A-1376A. Moody, J.R., and E.S. Beary. 1982. Purified Reagents for Trace Metal Analysis. Talanta 29:1003-1010. Nriagu, J.O., G. Lawson, H.K.T. Wong, and J.M, 

### Azcue. 1993. A Protocol for Minimizing Contamination in the Analysis of Trace Metals in Great Lakes Waters. J. Great Lakes Res. 19:175-182. Patterson, C.C., and D.M. Settle. 1976. The Reduction in Orders of Magnitude Errors in Lead Analysis of Biological Materials and Natural Waters by Evaluating and Controlling the Extent and Sources of Industrial Lead Contamination Introduced during Sample Collection and Processing. In: Accuracy in Trace Analysis: Sampling, Sample Handling, Analysis. P.D. LaFleur, ed. National Bureau of Standards Spec. Publ. 422, U.S. Government Printing Office, Washington, DC. Puls, R.W., and M.J. Barcelona. 1989. Ground Water Sampling for Metals Analyses. EPA/540/4-89/001. National Technical Information Service, Springfield, VA. Sakamoto-Arnold, C.M., A.K. Hanson, Jr., D.L. Huizenga, and D.R. Kester. 1987. Spatial and Temporal Variability of Cadmium in Gulf Stream Warm-core Rings and Associated Waters. J. Mar. Res. 45:201-230. Shiller, 

### A.M., and E. Boyle. 1985. Dissolved Zinc in Rivers. Nature 317:49-52. Shiller, A.M., and 

### E.A. Boyle. 1987. Variability 

### of Dissolved Trace Metals in the Mississippi River. Geochin. Cosmochim. Acta 51:3273-3277. Taylor, J.K. 1987. Quality Assurance of Chemical Measurements. Lewis Publishers, Chelsea, 

### MI. Tramontano, J.M., J.R. Scudlark, and T.M. Church. 1987. A Method for the Collection, Handling, and Analysis of Trace Metals in Precipitation. Environ. Sci. Technol. 21:749-753.Trefry, J.H., T.A. Nelsen, R.P. Trocine, S. Metz., and T.W.

Vetter. 1986.

Raw l P.-v. Reun. Cons. int. Explor. Mer. 186:277-288. U.S. Environmental Protection Agency. 1983. Methods for Chemical Analysis of Water and Wastes. EPA-600/4-79-020. National Technical Information Service, Springfield, VA. Sections 4.1.1, 4.1.3, and 4.1.4 U.S. Environmental Protection Agency. 1991. Methods for the Determination of Metals in Environmental Samples. EPA-600/4-91- 010. National Technical Information Service, Springfield, VP,. U.S. Environmental Protection Agency. 1992. Evaluation of Trace-Metal Levels in Ambient Waters and Tributaries to New York/New Jersey Harbor for Waste Load Allocation. Prepared by Battelle Ocean Sciences under Contract No. 68-C8-0105. Windom, H.L., J.T. Byrd, R.G. Smith, and F. Huan. 1991. Inadequacy of NASQANData for Assessing Metals Trends in the Nation's Rivers. Environ. Sci. Technol. 25:1137-1142. (Also see Comment and Response, Vol. 25, p. 1940.) Zief, M., and J.W. Mitchell. 1976. Contamination Control in Trace Element Analysis. Chemical Analysis Series, Vol. 47. Wiley, New York, NY.

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