Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

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## An Integrated Framew ork for Evaluating Leaching in Waste Management and Utiliz a tion of Secondary Materials

D.S
. K o ss on 1* , H. A. van der Sloot 2 , F. San c hez 1 and A. C. G a rrabrants 1

1 Depa rt m e nt of C i vi l an d E n vi ro nm ent a l Eng i neeri n g Vand erb ilt Un i v ersity Nashv ille, Tenn essee, USA

2 The Nethe r lands E n e r gy Res earch Foundation Petten , th e Neth erlan d s

Abs t rac t
A fram ewo r k fo r th e ev alu a ti o n of i n org a n i c con s titu en t leach i ng fro m wastes andsecond ary m a terials is

prese n ted. T h e fram e work is based on the m e asurem ent of i n trin sic leach i ng p r op erties o f th e m a terial in

co nju n c tion wi th m a th e m at ica l m o d e lin g to esti m a te release un d e r fieldm a n a g e m e n t scenario s. Site specific a n d de fault sce n ari o s are c onsi d ere d , which m a y be selected bas e d on the e v aluation context. A
tieredap proach is p r ov id edt o allow t h e e n d

- use r t o bal a nc e bet w ee n t h e s p ecificity of the release estimate,

t h e am ount of t e st i ng k n o w l e d g e req u i r e d , a pri o ri kn ow ledg e, and r e sour ces r e q u i r e d to co m p lete an
evaluation. Det a iled test m e thodologies a r e provid e d for a s u ite of laboratory leaching test s. Key Wo rds: lea c hing , metals, wa ste, so il, utiliza t io n, beneficia l use, seco nda r y ma teria l s, dispo s a l , la ndfill, risk assess ment, test metho d s

* t o wh om com m uni cat i ons sh oul d be a d d r es sed. Bo x 183 1 Statio n B, Nash v ille, TN 3 723 5. Ph on e: (615 ) 322 -10 6 4 , Em ail : Dav i d

. Ko sso n @Vand e rb ilt.ed u

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### INTRODUCTION

Leaching tests are used as t o ols to estim ate t h e release pote ntial of constituents from waste

m a t e ri al s over a ra nge o f po ss i b l e wast e m a nagem e nt act i v i t i e s, i n cl u d i n g d u ri ng recy cl i n g o r re use , f o r assessing the e fficacy of wast e treatm e nt processes, a n d aft e r disposal. T h ey m a y also be use dt o devel o p endpoints for re m e diation of contam inated s o ils and t h e s o urce term 1 f o r e nvi ro nm ental risk
ch aracterizatio n
. Th e Resou r ce Con s erv a tion andRe co v e ry Act (RCRA) req u i res th e USEPA t o classify
wastes as eithe r hazardous or n on-haza rdous. In im ple m enti ng this portion of RCRA, t h e USEPA a s ks,

“ W ould this waste pose unac ceptable e n vironm ental h azards if dispose d unde r a pla u sibl e, re gulatorily
defi ned, m i s m anagem ent sce n ari o ? ” T h is sc enari o typi cally represe n ts “ w orst case” m a nagem e nt (i.e., the

est i m a t e d hi gh est ri sk , pl ausi bl e, l e gal m a nagem e nt opt i o n) an d wast es po si ng suc h u n ac cept abl e
envi ronm ental hazards wa rra nt cla ssification and re gulation as haza r dous wastes. In de velopi ng the
To xi ci t y C h ara c t e ri st i c reg u l a t i on (4 0 C F R 2 6 1

. 2 4 ) , t h e US EPA de fi ne d t h e pl ausi bl e, w o rst

- case
mis m anage m e n t sce n ario for evaluating i n dustrial wa st e as co-dis posal in a m unicipal sol i d wa ste (MSW)
lan d fill. Th e assu m p tio n o f t

h is m i s m an ag emen t scen ario, i n tu rn , resu lted i n th e d e v e lopmen t o f th e
Extraction Procedure T o xicity test and its s u ccess o r, the T oxicity Cha r acter istic Leaching Procedure ( T CLP; see 45 FR 33 084 , May 1 9 , 1 980 , and 5 5 FR 11 798, Mar c h 2 9 , 1 9 9 0 ) , wh ich attem p ts to r e p licate

som e key leaching factors ty pical of MSW landfills.
The TCL P has com e unde r c r i ticism because of over broa d a pplication of t h e test (and underlying

assum p t i on of M S W c o - d i s po sal ) i n e v al u a t i n g an d re gul at i n g wast es , a n d som e t echni cal speci fi cat i o ns of

t h e m e t hod ol o g y
. T h e Sci e nc e A dvi s o ry B o ard o f USE P A revi e w ed t h e l e achi n g e v al uat i on f r am ewor k
b e ing em p l o y ed b y th e ag en cy in 199 1 and 1 999 ( U SEPA , 19 91 ; U S EPA, 199 9) . In th e 1 999 r e v i ew , t h e
Science Advis o ry B o ard state d :

The c u rre n t sta t e of the scie nc e supports, e v e n e n courages , t h e devel opm ent and use of diffe re nt leach tests for di ffe re nt applications . To be m o st scie ntifically supporta ble, a leac hing protoc ol s h oul d be bot h acc urate and reas onably related t o conditions g overni n g leacha b ility unde r actual waste di sposal conditions.

An d

1 In th is con t ex t , ‘sou rce term ’ refe rs to rep r esen tatio n of co nstitu en t release fro m a waste o r con t am in ate d
so il th at is u s ed in su b s equ e nt fate and t r an sp ort m o d e lin g for ex po su re ev alu a tion i n risk assessm e n t

.

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Th e m u ltip le uses of TCLP may requ ire t h e d e v e l o p m en t of m u ltip le leac h i ng tests. Th e resu lt may be a m o re flexi b le, case

- specific, tiere d testing sc h e m e or a su ite of relatedtests in corpo r ating t h e m o st im port a nt pa ram e t e rs aff ect i ng l eac hi n g
. A p pl y i ng t h e im pro v ed p r oc edu r e( s) t o t h e wo rst

- case scenari o likely to be enc o unte r ed in t h e fiel d coul d am elio rate m a n y p r ob lem s associated with c u rrent proce d ures. Al though t h e C o mmittee recognizes that t h ese m odificati o n s m a y b e mo r e c u mb e r s o me t o i m ple m ent, this type of prot ocol would bett er pre d ict leachability.

Th e Scien ce Ad v i so ry B o ard also criticizedt h e TC LP p r o t oco l on t h e b a si s of sev e ral tech n i cal
considerations , including t h e t e st’s c onsi d era tion of l eaching kinetics, liquid-to-s olid rati o, pH, potential for

co llo id fo rm ati o n, p a rticle size red u c tion , agin g , vo latile losses, an d co -m i n g ling of th e testedm a terial with
othe r wastes (i. e ., c o - d isposal)

. In res p onse , thi s pa per offe rs a n alternative fr a m ework for e v aluation of waste leaching potential
th at resp ond s t o m a n y o f th e criticis m s o f the TCLP. It p r ov id es a tiered , flex ib le fram e work cap ab l e of
in corpo r ating a ran g e of site co nd itio ns th at affect waste leach ing an d so can estim ate le ach ing p o t en tial

u n d e r co nd ition s m o re represen tativ e o f act u a l waste m a n a g e m e n t . Th e p a p e r also ad dresses practical
im pl em ent a t i o n of t h e fram e wo rk i ndi f f ere n t ap pl i cat i ons , an d a n e x am pl e ap pl i cat i on o f t h i s a p pr oac h f o r

ev alu a ting altern ativ e treatm e n t pro cesses for m e rcu r y co n t a m in atedso ils is p r esen tedin a co m p an ion

pape r (Sa n chez et al. , 200 2)

. Th e leach testin g pro t o c o l s used inthe fram e wo rk also address technical

conce r ns wi t h t h e TC L P . T h e t e st pr ot oc ol s p r o v i d e d here ar e desi gne d o n l y fo r a ppl i cat i o n t o i n or ga ni c species; however, t h e c once p t s prese n ted for the integrat ed fram ework are gene ral, with ap p lication to bo th
i n o r ga ni c a n d or ga ni c speci es . A p pl i cabl e t e st m e t hods f o r or ga ni c speci es are t h e s u b j ect o f f

u t

u re
devel opm ent

. C o m p l e t e t echni cal speci fi cat i ons f o r

t h e pr o t ocol s a r e pr o v i ded i n t h e A p pen d i x
.

IS THE RIGHT QUESTION BEING ASKED?

In eval uating the leachi n g pot ential of waste s base d on a single, pla u sible worst-case
mis m anage m e n t sce n ario via TCLP, t h e USEPA seeks to pr ov id e env i ro nmen tal p r otection for unregul ated

wastes. Ho wever, wastes are man a g e d in m a n y d i fferen t settin g s , and un d e r a rang e of con d ition s t h at affect
waste leachi n g. T h e relia nce of the USE P A on a si ngl e, pla u sible worst-ca se, m a nagem e nt sce n ario for leach testing may be gene rally protectiv e, but often at t h e c o st of ove r re gulation. It has als o proven to be
in ad eq u a tely pro t ectiv e i n some cases (see d i scu ssi on o f sp en t al u m in u m po tlin er regu latio n at 6 2 FR
4 100 5, Ju ly 31, 199 7 and 62 FR 63 458 , D e ce m b er 1 , 19 97 ). W h ile r e lian c e on a sing le waste m a n a g e m e n t
scenari o as the basis for leach testing m a y sim p lify im ple m entation of RC RA, m a ny of the wastes e v aluated

u s ing TCLP h a v e little if an y p o s sib ility o f co -d ispo sal with MSW ; assessmen t o f th e rel ease po ten tial o f

wast es as act ua l l y m a naged i s neede dt o bet t e r un der s t a n d t h e haza rds p o se d by wast e
. Ne i t h er t h e TC LP ,

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n o r an y o t h e r test p e rfo rm edu n d e r a si n g l e set o f c ond ition s , can prov id e an accurate assessm en t o f waste
hazards for all waste.
Fro m an env i ro n m en tal p r o t ectio n p e rsp ecti v e (and setting asid e th e p a rticu l ar requ irem en ts o f RCRA), t h e goal of leaching t e sting is t o a n swer th e question “ W hat is the pote n tial for t o xic constitue n t
release from this waste by leachin g (and t h erefore the ris k ) unde r th e selec t ed m a nagem e nt option ? ” For
envi ro nm ent a l l y sou n dwast e m a nagem e nt , t h e fol l o wi n g q u estio ns result fr om differe nt pers pectives:

• From the waste ge nerat o r’s pros pective - Whic h waste m a nagem e nt options are accepta ble for a

waste ?

• Fro m th e waste m a n a g e m e n t facility’s p e rspectiv e - Wh ich wastes are su itab l e fo r d i spo s al in a
sp ecific d i spo s al facility ?

• From the pote n tial end-use r’s pers pective - Is this sec o nda r y m a terial acceptable for use in commerce (e.g., as a c onst r uc tion m a terial)?
The fram e wor k fo r a n sw eri n g t h e s e quest i o ns s h oul d be c onsi s t e nt acr os s m a ny appl i cat i ons, ra ngi ng f r om

m

u l tiple waste disposal sce n arios to determ ination of the e n vironm enta l acceptability of materials that may
be s u bject t o l e achi n g (e. g ., co nst r uct i o nm a teri al s). At th e sa m e ti m e , th e fram e wo rk sh ou ld b e flex i b le

en oug h to con s id er reg i o n a l an d facility -sp e cific d i fferen ces in factors aff ectin g leach i ng (e.g ., p r ecip itatio n , facility design). A m e thodol ogy guid eline (ENV 12920, 1996) devel ope d unde r E u ropean sta nda rdiz ation
in itiativ es recommen d s th at t h e m a n a g e m e n t scen ari o b e a cen tral co n s i d eratio n in t h e testin g and
eval uat i o n of wast e f o r di sp o s al an d bene fi c i al use of seco nda ry m a t e ri als. T h i s m e t hod ol o g y i s a n

ex ten s i o n of the app r o a ch in th e B u ild ing M a terial s Decree estab lish e di n Th e Neth erland s (Bu ild i n g Materials Decree, 1995).
The a n s w ers t o t h e que st i ons pos ed ab o v e re qui re sev e ral i n terrelated assessm en ts in clu d i ng (i) th e
release rate a n d total am ount ove r a de fine d ti m e in terval of pote n tially hazar dous c o nstituents from the waste, (ii) atten u a tion of th e co nstitu en ts o f co n c ern as t h ey m i g r ate fro m th e waste, t h rou g h groun dwat er,

to the rece ptor being c o nsidered, ( iii) exposure of t h e recept o r, a n d (iv) t h e toxicity of eac h specific

co nstitu en t. C o n s id erab le effort h a s resu lted i n acc u r ate assessm en t tech n i qu es and d a ta for ev alu a ting

co n t am in an t tran sp or t thr ough th e env i ron m en t ( a nd attenuatio n ) , an d tox i city f o r

a larg e n u m b e r o f

co nstitu en ts.
In con t rast t o t h e d e tailed research on con s titu en t fate, transp ort an d risk fo llo wi n g release,
esti m a t i o n o f co n s titu en t release b y leach i ng m o st o f ten assu m e s (i) th e t o tal co n t en t p r esen t is av ailab l e fo r

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release, o r (ii) t h e co n t am in an t con cen t r atio n in th e l each a te will b e eq u a l to th at m easu r ed d u ring a single
b a tch ex traction an d is co n s tan t with tim e 2 , or (iii) t h e fractio n of t h e co n t amin an t ex tract ed d u ring a b a t c h
extraction is e q ual to t h e fracti o n th at will leach (USE PA, 1986; Goum ans et al. , 1991). T h ese a p proache s
fre que ntly res u lt in gros sly inaccurate e s timation of actual release (both over - a n d under-estim ation).
Inacc urate rele ase estim a tion, in turn , forces disposal of m a terials that are s u itable for beneficial use,

man d a tes rem e d i atio n of so ils to lev e ls b e y o n d th at necessa ry for environmental pr ot ect i o n , un necessa r i l y depl et es di sp os al capaci t y , o r resul t s i n gr ou ndwat e r conta m ination (i f rel ease is underes tim a ted). In
ad d ition , t r eatmen t p r o cesses, th at m a y b e prov en to red u c e th e ex tracted co n c en tration fo r a regu lato ry test (TC L P ) , ha ve r e sul t e d i n i n c r e a sed rel ease w h en com p are d t o m a nagem e nt scena r i o s wi t h out t

r eat m e nt (Ga rra bra n ts, 1998). T h us, m e thodol ogies tha t result in a m o re acc urate esti mate of c onta m inant leaching

m a y bot h i m pr ove en vi r o nm ent a l p r ot ect i o n t h r o u g h m o re e ffi ci ent use of r e so urces an d b e eco nom i cal l y bene fi ci al

. In ge neral , l eac hi n g t e st s ca n be cl assi fi e d i n t o t h e f o l l o wi n g cat eg o r i e s ( E nvi ro nm ent C a nada , 1 990 ): (i) tests d e sign edto sim u la te co n t amin an t re lease unde r a speci fic envi ronm ental scenari o (e.g., synthetic acid rain leach test or TCLP ), (ii) seque ntial chem i cal extraction tests, or (iii) te sts which a ssess
fund am en tal le ach ing p a ram e t e rs.
Tests that are designe d t o simulate release u nde r s p ecific e nvi ronm ental scenari o s a r e limited
because they m o st often do not pr ovide inform ation on re lease unde r e n vironm ental scenari o s diffe re nt
fr om t h e one b e i ng si m u l a t e d. Thi s t y pe o f l i m i t a t i on has l e d t o wi des p rea d m i suse an d m i si nt erpret at i o no f
TCLP resu lts. Relian ce on si m u la tio n - b a sedtesting also results in t r eatment processes t h at are desi gne d to “pass t h e test” rather tha n t o i m prove waste characte r istics or re duce leaching unde r act ual use or dis posal

scen ari o s. Fo r i n stan ce, it is co mm o n p r actice to in cl u d e waste treatm e n t a d d itiv es to bu ffer th e TCLP
leachant at a pH resulting in mini m u m relea s e of targ et c o nstituents. However, whe n t h e buffe re d m a terial is landfilled, t h e landfill leachate pH m a y be dom inated either by the m a terial buffe ring ca pacity (m onofill
scenari o s) or by othe r s o urces (c o-disposal s cenari o s). In ei ther case , the release scena r io m a y diffe r sig n i fican tly fro m co n d ition s si m u latedb y t h e testing p r o t o c o l and u npred ictedleach i ng b e h a v i o r m a y

occur. Sequ en tial ch emical ex tractio n tests ev alu a te releas e base d on ext r action of the waste with a series
of increa singly m o re aggressi ve e x tractants

. The se qu en tial ex traction ap pro ach, o r i g in ally co m p iled b y

2 Th is assu m p tio n is o f te n re fe rre d to as t h e “ i nfinite s o urce ” assum p tion.

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Tessier et al. (Tessier et al. , 19 79) , h a s b e en ad ap ted b y o t her s ( F r azer and Lu m , 19 83 ). Th ese ad ap ted

app r oaches ha ve l i m i t a t i ons t h at re q u i r e cas e-by -ca s e e v al uat i o n ( K heb o h i a n a n d B a uer , 1 9 87; Ni rel a n d
Mo rel, 19 90). In ad d ition , t h e o p e ration a lly defin e d n a tu re of seq u e n tial ex t r actio n app r o a ch es m a k e
gene ral i zed a p pl i cat i on i n a wast e m a nage m e nt fram e wor k di ffi c u l t

. In addition, ge ochem i cal speciation m odeling also ca n provide useful insi ghts int o leachi n g
b e h a v i or, as it p r ov id es i n fo rmatio n on p o ssib le so l u b ility co n t ro lling m i n e ral ph ases (Mei m a et al. , 19 99 ;

van de r Sl o o t , 19 9 9 ; C r a nnel l et al. , 200 0), th e ro le o f so rp tio n pro cesses with Fe, M n and Al ph ases (M eim a and C o m a ns, 1 9 98; M e im a and C o m a ns, 19 9 9 ), a n d com p l e xat i o n wi t h di ss ol v e d or ga ni c m a ter (Kei zer an d va n R i em sdi j k, 1 9 9 8 ; Ki n n i b ur g h et al. , 19 99 ; v a n d e r Sloo t, 2 002 ). How e ver , g e o c h e m i ca l

m o d e lin g often req u i res d e tailedso lid ph ase id en tificatio n th at is eith er imp r actical or no t po ssib l e fo r

co m p lex m a ter i als, and n eed ed so lub ility an d ad so rp tio n param e ters m a y b e u n a v a ilab l e. Altho ugh th e
in fo rm atio n it p r ov id es can be u s edeffectively in wast e m a nagem e nt , ge ochem i cal m odel i ng oft e n onl y
p r ov id es qu alitativ e or sem i -q u a n titativ e results an d is no t a to o l for regu lato ry con t ro l.
The alternative fram e work de scri be d below was designe d t o asses s int r ins i c waste leachi n g
p a ram e ters, th ereb y p r ov id ing a so und b a sis for estim at io n o f release po ten tial in a rang e of d i fferen t pote n tial waste m a nage m e nt scenari o s. It provides a basis ei ther for c h oosi n g accepta ble managem e nt or
di sp osal fr om am ong se veral pos si bl e opt i o n s o r f o r ju d g i n g whet her a pr e-sel ect ed m a nagem e nt or di s pos al
opt i o n i s i n fac t envi ro nm ent a l l y sou n d an d a p p r op ri at e.



### AN ALTE RNATIVE FRAMEW ORK FO R EVALUAT I ON OF LEACHING

Waste testing sh ou ld pro v i d e i n fo rm atio n ab ou t po ten tial con t amin an t release fro m a waste in th e

co n t ex t of t h e an ticip ated d i sp o s al or u tilizatio n co nd ition s . Th u s , testing sh ou l d reflect th e rang e o f

co nd itio ns (e.g., p H , water con t act, etc.) th at will b e presen t in th e waste an d at its in terface with its

sur r o u ndi n g s d u ri ng t h e l o n g - t erm , whi c h m a y be si gni fi ca nt l y di ffe re nt t h ant h e p r o p ert i es of t h e m a t e ri al
im m e di at el y fol l o wi n g pr o duc t i o n 3

.

3 Ex am p l es wh ere th e m a terial as produ ced h a s d i ffer en t co nstitu en t release b e h a v i o r th an th at du ri n g utilization are: (i) c onc rete pillars immersed in su rface water whe r e release reflects t h e ne utral pH of surface water rather t h an the a l kali pH of Portland cem ent conc rete (va n der Sl oot, 2000), (ii) stabilized coal fly ash e x posed to sea w a t er showing surface sealing (Hoc kley and van der Sloot, 1991), (iii) MSWI bot t o m ash use d i n r o a dbase appl i cat i o n bei n g ne ut ral i zed wi t h a fe w y e a r s of fi el d e x po sure (S ch reu r s et al ., 2000), a n d (iv) use of steel slag in coasta l protection applications where V a n d Cr leaching is reduce d b y th e n a tural fo rm atio n of ferric ox id e co ati n g s in th e u tilizatio n en v i ronmen t (Co m an s et al. , 19 91)

.

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The goals of a revise d fram e work for e v aluation of conta m inant leaching s h ou l d be to: (i) provide
conservative 4 but realistic estimates of c ont a m inant leaching for a broa d range of waste t ypes, c o nstituents

o f

con cern , env i ro n m en tal con d ition s , and man a g e m e n t op tio ns, (ii) u tili ze testin g st rateg i es th at can b e
carried o u t usi n g stan dar d la b o rat o ry practic es in reas ona bl e tim e fram e s (e.g. , se veral h o u rs to s e ve ral
d a ys, d e p e nd ing o n requ irem e n ts), (iii) p r ov id e for re lease esti m a tes th at co n s i d er site-specific con d ition s , (iv ) en cou r ag e i m p r ov em en ts in waste m a n a g e m e n t p r actices, (v) p r o v i d e flex ib ility to allo w lev e l of
eval uat i o n (an dhence de g r ee o f ove r-c o n ser v at i s m 5 ) t o be b a sed o n t h e use r’s re qui rem e nts, ( v i ) ev ol ve i n
resp o n se t o ne w i n f o rm at i on and t a ke a d va n t age o f pri o r i n fo rm ati on, a n d (vi i ) be c o st e f f ect i v e.
In con cert with th ese go als, evalu a tio n of co nstitu en t release can b e app r o a ch ed b y a series of
step s: (i) d e fine m a n a g e m e n t scen ari o s and mech an ism s o ccu rring in th e scen ari o s (e .g ., rain fall i n filtratio n)
th at con t ro l con s titu en t release, (ii) m easu r e in trin sic leach i n g p a ram e ters for th e waste or m a terial b e in g

ev alu a ted (ov e r a rang e of leach i ng co nd ition s ), (iii) u s e rel ease m o d e ls inco rpo r ating m easu r edleach i ng
param e t e rs (c o rres p on di n g t o ant i c i p at ed m a nagem e nt conditions) t o estimate rel ease fl uxes and l o ng-te r m

cum u lative release, a n d (iv) c o m p are release estim a tes to acceptance criteri a. Mana gem e nt scenari o s ca n
either be defa ult scenarios tha t are desi g n ed t o be c o n s er vat i v e or i n c o rp orate site-sp ecific in fo rm atio n to provide m o re-a ccurate estim ates of release. In CE N TC 292 6 , such a sce n ari o -base da p proa ch has bee n
descri bed as a nex peri m e nt al st anda rd (E N V 12 9 2 0 , 19 9 6 )

. Thi s st a nda rd descri bes st e p s ve ry si m i l a r t o
th o s e id en tified ab ov e.
Th e con t ro lling release m ech an ism s m o st o f ten can b e describ e d in term s o f eith er equ ilib ri u m

co n t ro lled or mass-tran sfer rate co n t ro lled. Equ ilib ri u m con t ro lledrelease o c cu rs fo r slow p e rco l atio n

t h r o u g h po ro us o r gra nul a r m a t e ri al s. M a ss t r ansf e r

rate controlled release occurs when fl ow is

p r edo m in an tly at th e ex terior b oun d a ry o f m o no lith ic m a ter i als o r p e rco l at io n is v e ry rap i d relativ e to m a ss

tran sfer rate o f co nstitu en t release to t h e p e rco l atin g water. In trin sic leach i ng p a ram e ters th at are to b e

measu r ed using laborato r y testin g are: con s t itu en t availab ility, co n s titu en t p a rtitio n i ng at eq u ilibriu m
bet w ee n a que o u s a n d s o l i d ph ases as a f

unct i ono f pH a n d l i qui d-t o -s ol i d ( L S) rat i o , aci d and ba se

4 In th is p a p e r, “co nserv a tiv e” esti m a tes o f release i m p lies th at th e actu al release will b e l e ss th an o r equal to th e esti m a te d release during th e m a nagem e nt sce n ari o c o nsi d e r ed

. 5 For m o st case s , m o re detaile d waste c h arac terization resul t s in m o re acc urate estim a t es of actual

co n t am in an t release, prov id i n g safety m a rg in s b y redu cing the de gree of over-es tim a t ed release. However,
m o re d e tailed ch aracterizatio n requ ires add i tio n a l testin g co st an d ti m e wh ich m a y n o t be ju stified b ecau s e of

ei t h er t h e l i m i t e d am ount of wast e t o be m a naged , t i m e con s t r ai nt s, o r ot he r rea s o n s. 6 C E N/ TC 29 2 i s t h e E u ro pea nSt an dar d i zat i o n Or ga ni zat i o n(C E N ) t e c hni c a l com m i t t ee deal i ng wi t h

ch aracterizatio n o f w a ste (est ab lish e din 1993 ). Fo r add ition a l inform atio n , see ww w.ce no rm .be on t h e Inter n et.

7Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

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n e u t ralizatio n cap acities (ANC and BNC ) , an d con s titu en t mass tran sfer rates. Defin ition o f m a n a g e men t
scenari o s a n d a pplication of i n trinsic pa ram e ters, releas e m odels a n d decisi on criteria a r e discuss e d in lat e r

sect i ons o f t h i s pa per
. To ac hieve the desire d fram e wo rk g o als a n d seri es o f ev al uatio n step s, a t h ree-tiered testin g
pr o g ram i s pr o pos ed (Fi g u r e 1) . A n anal og o u s, t i e re d a p pr oach , devel o p e d wi t h i n p u t f

r o m t h e aut h ors o f

t h i s pa per , has been rec o m m ende d by Ei ghm y and C h es ne r fo r e v al uat i o n of seco n d ary m a t e ri al s for u s e i n
hi g h way c o nst r uct i o n (Ei g hm y and C h es ne r, 2 0 0 1 )

. In t h e f r am ework p r es ent e d i n t h i s pa per , eac h
successi ve tier provides leac hi ng data t h at is m o re speci fic t o th e m a terial b e ing te sted and pos sible leac hing
conditions tha n the pre v ious ti er. Indi vi dual leaching tests a r e designed to provide data on in t r insic leac hing

p a ram e ters for a waste o r secon d a ry m a terial. Resu lts fro m m u l tip le tests, u s edin co m b inatio n with either
defa ul t m a nagem e nt scenari o assum p t i ons ( m ore conse r v a tiv e, b u t with sim p ler i m p l e m e n tatio n) o rsitespecific inform ation, provide m o re accu rate release assess ments. However, t h e re sults of a si ngle test (e.g.,
th e first tier availab ility tes t ) can b e u s ed as th e m o st co n s erv a tiv e app r o a ch for m a n a g e men t d ecision s
wh en tim e o r eco n o m ic co n s i d eration s do no t ju stify m o re-d etailed ev aluatio n s
. Three t i e rs of a ssessm ent can be defi ned t o e ffi ci ent l y ad dre ss t h e a b ove w a st e m a nagem e nt

que st i ons an d cri t e ri a:
Tier 1 – Screenin g b a sed assessm e n t (av a ilab ility). Tier 2 – Eq u ilib ri u m b a sedassessm en t ( o v e r a rang e o f pH an d LS cond itio n s ).
Tier 3 – Mass t r ans f er ba sed a ssessm ent.
Pr ogr essing f r om Tier 1 th roug h Tier 3 pr ov i d es i n cr easi n g l y m o r e r ealistic andtailo r e d , an d less

co nserv a tiv e, esti m a tes o f release, b u t also req u i res m o re exten s iv e testing

. Tier 1 is a screen ing test th at p r ov id es an as sessm en t o f th e max i m u m p o t en tial for release un d e r
th e li m its o f anticip atedenv i ro n m en tal con d itio n s , witho u t co nsid eration of th e ti m e frame fo r release t o

o ccur. Th is con cep t of m a x i m u m p o t en tial release is o f ten referredt o as “av ailab ility.” In practical

ap p lication , availab ility is o p e ratio n a lly d e fi n e d using a sel ected test m e th o d . Leach i ng po ten tial is

exp r esse d o n a m a ss basi s (e. g ., m g X l eac he d/ k g wast e). T h e basi s fo r t h i s b o u n d i n g a n a l y s i s wo ul d be

t e st i ng un der e x t r act i o n c o n d i t i ons t h at m a xim i ze re lease within practical considerations (see furthe r
d i scu ssi on b e low). Tier 2 testin g is b a sed on d e fi n i ng liqu i d-so lid equ ilib ri u m as a fun c tion o f pH andLS (i.e., ch em ical reten tion in th e m a trix ). Tier 3 te stin g u s es inform at io n o n liq u i d

- so lid equ ilib riu m in

co nju n c tion wi th m a ss tran sfer rate i n fo rm ati o n (i.e., ph ysical reten tion o f co nstitu en ts i n ad d ition to

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chem ical retention i n the m a trix). Bot h Tier 2 and Ti er 3 testin g m a y u s e eith er d e fau lt o r site-sp ecific

man a g e m e n t assu m p tio n s (e.g ., infiltratio n rates, fill d e p t h) to estim ate rel ease as a fu n c ti o nof tim e. Fo r a

scen ari o , leachate co n c en trati o n s based on eq u ilibriu m will always b e g r eater th an o r equ a l to t h ose b a sed

o n m a ss tran sfer rate. Th u s , eq u ilibriu m release esti m a tes (Tier 2) m a y b e a con s erv a tive app r ox im a tio n in
the absence of mass trans f er rate in fo rm atio n (Tier 3) 7

. For Tier 2 and Tier 3 assessm ents, t h ree le ve ls of testing (L evels A, B or C) are de fine d. Each of

t h e t h ree l e vel s o f t e st i n g m a y be use d de pen d i n g ont h e am ou nt of p r evi o us kn o w l e d g e ( t est dat a ) of t h e

wast e, or t h e d e gree o f si t e -s p eci fi c t a i l o ri n g desi re d. Level A (i n ei t h e r Ti er 2 or 3 ) uses conci s e o r
si m p lified tests. The basis for Tier 2A woul d be m easurem e n t of t h e leachi n g ch a r acteristics at conditions
that bound the range of antic i p at ed fi el d s c e n ari o s fo r e qui l i bri u m (e.g ., us e o f t h ree e x t r a c t i ons t o defi n e
rel ease at aci di c, ne ut ral a n d a l kal i pH co n d i t i ons wi t h co nsi d erat i o n of t h e m a t e ri al ’s nat u ral p H at L S =1 0

m L / g ). T h e bas i s fo r Ti e r 3A t e st i ng w oul d b e a coa r se e s t i m at e of rel ease rat e s (e. g ., a f o u r p o i n t , 5 da y

m onolithic leach test). The data from these tests wo uld be use din conj unction with defa ult m a nagem e n t

scen ari o b oun din g con d ition s , and sim p lified release m o d e l s , to prov id e a co nserv a tiv e assessm en t in th e
abse nce of m o r e det a i l e d k n o w l e d g e. Exam pl e ap pl i cat i o n s o f Le vel A t e st i ng (i n ei t h er Ti er 2 o r 3) i n c l ude
for rou tin e d i sp o s al of wastes th at m a y fail Tier 1 te stin g, si m p lified ev al u a tio ns for d i sp o s al or u tilizatio n

t h at can be j u st i f i e d based o n m o re conse r vat i v e ass u m p t i ons, a n d ve ri fi cat i on t h at a m a t e ri al bei n g t e st e d

ex h i b its ch aracteristics si m ilar to a class of m a terials th at h a s prev i o usly b e en m o re ex ten s iv ely
characte r ized (e.g., Le vel B, s ee below).
Lev e l B testing prov id es d e tai l ed ch aracterizati on of the wa ste or sec o ndary raw m a terial. The
b a sis for Tier 2B testin g wou l db e d e fi n itio n o f eq u ilib ri u m o v e r t h e fu ll ran g e of relev a n t pH an d LS

co nd itio ns (i.e., pH 2

- 13 , andLS 0

. 5

- 1 0 m L / g ). Th e m a x i mu m release o b serv ed un d e r these cond itio n s also
is fun c tion a lly eq u i v a len t t o t h e av ailab ility measu r ed in Tier 1 , althou gh t h e sp ecific v a l u es m a y d i ffer
b a sed o n th e m e th od o f d e termin atio n
. Th e b a sis for Ti er 3B testin g wou l d b e a m o re com p le te d e fin itio n of

m a ss t r ans f er r a t e s (e. g ., 1 0 d a t a poi nt s ove r 60 day s ) an d verificatio n of material in teg r ity (e.g., st reng t h
aft e r l eac hi n g ). These m o re de t a i l e d dat a ca n be use d in conju n c tion with eith er d e fau lt o r site-sp ecific

m a nagem e nt scenari o ass u m p t i o n s , a n d ei t h er si m p l i f i e d o r a dva nce d rel e ase m odel s . F o r e x am pl e, resu l t s
fro m Lev e l B testin g i n co njun ctio n with defau lt s cen ario s an d sim p lifiedreleas e m odels can provide the
basi s fo r c o m p ari s o n of t r eat m e nt pr ocesses
. R e sul t s fro m Lev e l B testing u s edi n co nju n ctio n with site-

7 Ex trapo l atio n o f labo ratory mass tran sfer t e st resu lts to fieldcond itio n s requ ires care f ul considerati o n of

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speci fi c i n f o rm at i on a n d ad va nced m odel s p r ovi de t h e m o st realistic and least conservative assessm ent.
Lev e l B testing wo u l d o n l y b e carried o u t i n itially fo r a m a terial o r class o f materials g e n e ratedin larg e
q u a n tities, and th ereafter o n l y if sign ifican t ch ang e s in m a te rial ch aracteristics are ind i cated b y p e riod ic
Level A t e st i n g. Level B t e st i n g p r ovi des i n s i ght i n t o t h e cri t i cal com ponen t s fo r a gi ven m a t e ri al and t h us
pr o v i d i n g t h e b a si s f o r s e l ect i o no f a

re duce dset of pa ram e ters fo r su b s equ e n t testing

. After co m p letio n of
Lev e l B testing, Lev e l A testin g can b e used to an sw er t h e que stion, “ D oe s the m a terial currently bei n g
tested ha ve t h e sam e characteristics of the m a terial th at was previ ously c h a r acterized in m o re detail (Le v el B)? ” Th e freq uen c y of testing can b e relatedt o th e d e gree o f agreem en t with th e lev e l B testin g
. Goo d

p e rform a n ce is th en reward ed b y redu ction i n test freq u e n c y. A d e v i atio n th en req u i res i n itially m o re
fre que nt testing to ve rify the deviation, and if neces sary a return to th e le vel B testing t o evaluate t h e ca use.
Add itio n a l ex am p l es o f app l i catio n o f Lev e l B testin g i n clud e m o n o fill d i sp o s al of sp ecial wastes an d approvals for beneficial use of secondary m a terials.
Lev e l C p r ov ides th e m o st sim p l i fied testing for q u a lity con t ro l pu rpo s es, and relies on

measurem ent of a few key i n dicators of wast e cha r acter istics, as i d en tified in th e lev e l B t e stin g
. An

ex am p l e o f Lev e l C testing wo u l dco nsist of titratio n of a sam p le to a d e sign ated pH with measu r em en t of
th e con c en tratio n of a li m ited n u m b e r o f constitu en ts in t h e resu lting si n g l e ex tract. Sp ecific Lev e l C testin g
req u i r em ent s wo ul d be de fi n e d ona case sp eci fi c basi s. Le vel C s h o u l d o n l y be use da f t e r Le vel B t e st i n g
h a s i n itially b een co m p letedto p r ov id e a con t ex t for q u a lit y co n t ro l. On e ap p lication o f Lev e l C testing

wo ul d be t h e r out i n e (e .g ., da i l y , weekl y o r m ont hl y ) eval u a t i on of i n ci ne r a t o r as h p r i o r t o di sp osal

. A feedb a ck loop is p r ov id ed betw een Tier 2C and Tier 2A within t h e fra m e wor k (Fig u r e 1 ) . T h is
lo op is p r ov id edto ind i cate that Tier 2A testi n g can be u s ed o n a ra nd om basi s t o pr o v i d e fu rt he r ass u ra n ce

o f

attain m e n t o f regu lato ry obj ectiv es wh en m u ch m o re si m p l i fied testing is allowed o n a rou tin e b a sis (Tier 2C). In t h is cas e, the Tier 2A t e sting is c o m p ared with th e m o re co m p lete Tier 2 B ch aracterizatio n testin g to
veri fy t h at t h e bat c h o f m a t e rial bei n g t e st ed has n o t de vi at ed si gni fi ca nt l y fr om t h e m a t e ri al t h at was
ori g inally cha r acterized a n d s e rves as t h e ba seline assessm ent. A sim ilar approach m a y be use d whe n
q u a lity con t ro l testin g is b a sed on m a ss tran sfer rate te sting (Tier 3 C ) rath er th an equ ilib ri um testin g (Tier
2C ).
Wh ile the ab ove fram e work prov id es th e sp ecific b a sis on ly fo r ev alu a ti o n o f ino r g a n i c

co nstitu en ts, an an alog ou s set o f test con d iti o n s can b e d e scrib e dfor ev alu a tio n of o r g a nic co nstitu en ts.

the exte rnal surface a r ea for water c o ntact and the potentia l for e x ternal st resses.

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Add itio n a l consid eration s for o r g a n i c con s titu en ts wou l d i n clu d e (i) t h e poten tial for m o bilit y o f a non aq u e ou s ph ase liq u i d , (ii) t h e fact th at pH d e pen d e n ce of aq ueo u s p a rtitio n i n g is u s u a lly limitedto th e
i ndi rect (al t h ou gh i m port a nt ) effect of p H o ndi ss ol ve d or ga ni c car b o nl e ve l s fr om hum i c or si m i l a r

su bstan ces, and (iii) av ailab i l ity fo r m a n y org a n i c con s titu en ts is limited an d m a y req u i re a m o re co m p lex

m odel i ng a p p r oach

.

DECI SIO N M A KI NG B A S E D O N THE EVAL UATI O N F R A M EW ORK
App licatio n of lab o rato ry testi n g resu lts to env i ro n m en tal d e cisio n - m a k i ng requ ires lin k i ng th e
l abo rat o ry dat a t o e nvi ro nm ent a l end poi nt s o f c once r n( p r o t ect i on of h u m a n heal t h a n d e n vi r onm ent ) . T h i s
i s d one t h r o ug h dat a o r m ode l s t h at re prese n t envi ro nm ent a l pr ocesses , i n c l udi n g g r o u n dw at er t r a n s p ort o f
releasedcon s titu en ts, expo sure to h u m an s o r an im als v i a d r in k i ng water, an d th e t o x i city o f th e released

co nstitu en ts o f co n c ern
. Th is link a ge was estab lish e d fo r th e TCLP based on assu m i n g th e test results yield e da leach ate

co nstitu en t co ncen tration th at reflected an ticip atedfield leach a te th at wou l d b e p r od u c edd u ring d i spo s al in the bounding scenari o . This l eachate c onstituent c o ncent r ation i n tu rn would be re duced through natural

gr o u n d w a t e r att e nuat i o n pr oc esses as i t m o v e d t h r o u g h th e g r ou nd water (e.g ., d ilu tio n and ad so rp tio n)
b e fo re reach i ng a drink i ng water well. Th is “co n c en tr ation-b a sed app r o a ch ” im p licit ly a ssu m e s an infin ite

so urce of th e co n s titu en ts o f co n c ern an d do es no t acco u n t fo r eith er t h e anticip ated ch anges in release o v er
ti m e ( i n c lu d i ng exh a ustio n of th e so ur ce) or t

h e p o t en tial for cu m u lativ e effects o f release o v e r tim e.
Furt herm ore, this a p proac h c onsi d ers only t h e leachi n g be havi or of the material; it does not c o nside r the

man a g e m e n t co n t ex t (e.g., d i sp osal v s
. u tilizatio n , d e si g n o f th e m a n a g e men t scen ari o , g e ograph i c location). Thus , the c o ncent r ation-ba se d a p proach establis he s a leachate c o ncent r ation (as m easured in the
TC LP) bel o w whi c h no si g n i f i cant i m pact to dri nki ng wat e r i s a n t i c i p at ed. Thi s a p pr oa ch al s o ca n be
mislead in g if th e test co nd ition s d o no t reason ab ly refl ect the fieldcon d ition s (e.g ., with resp ect to pH an d
LS ratio ). The proposed alternative is a pe rform a nce or “im p act-base d approa c h .” T h is approach foc u ses on
th e release flux of p o t en tially t o x i c con s titu ents ov er a d e fin e d tim e in terv al. Thu s , th e m a n a g e m e n t
scenari o i s e v a l uat e d base d o n a so urce t e rm t h at i n c o r p orat es co nsi d e r at i o n of sy st em desi gn , net
in filtratio n and th e leach i ng ch aract eristics of th e m a terial. Basin g assessmen t an d d e cisio n s on estim at ed
release allows consideration of the waste a s c ontaini ng a fini te am ount of the constituent of intere st, the

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ti m e co u r se of release, an d the ab ility to ad ap t tes tin g resu l t s to a rang e of m a n a g e m e n t scen ari o s. Th e

measu r e o f rel ease wou l d b e th e m a ss o f con s titu en t releas ed p e r affected area ov er tim e (i.e., release fl u x ). Knowledge of the release flux woul d allow m o re accurate assessm ent of i m pact to water res o urces (e.g., groundwater or surface water) by defi ning the m a ss i nput of constituent t o the r ecei ving body over tim e
. R e sul t s o f t h i s im pact -base da p p r oach canp r ovi de di rect i n put i n t o su bse q uent ri sk asses s m e nt for deci s i on

m a ki ng, ei t h er base d onsi t e -s peci fi c a n al y s i s o r usi n g a ge neral i zed set of de faul t ass u m p t i o n s
.
Manageme nt scenari o s
Waste m a n a g e men t o r u tilizatio n scen ario s m u st b e u s ed t o link laboratory assessm en t resu lts to
im pact assessment. De fining scena r io s f o r

t h i s pu rp ose re q u i r es t h e l eac hi ng m ode co nt r o l l i ng rel ease (equ ilib riu m o r m a ss tran sfer), th e site-sp ecifi c LS ratio , t h e field p H , an d a ti m e fram e fo r assessm en t.
Valu es d e scribin g a sp ecific waste m a n a g e men t facility o r a h ypo th etical d e fau lt scen ario cou l d b e used

. Using t h ese sit e con d ition s wi th labo rat o ry measu r es o f con s titu en t so lub i lity as a fun c tio n of p H an d LS
ratio , a sim p le release m o d e l can b e u s edto esti m a te th e cu m u la tiv e m a ss o f th e con s tituen t released over
th e ti m e fram e for a p e rco l ation / equ ilib riu m scen ari o
. In cl udin g lab o ratory measu r em en t mass tran sfer rates
allo ws app licatio n of sim p le release m o d e ls for m a ss tran sfer rate con t ro lled m a n a g e m e n t scen ari o s (e.g.,

m o n o lith ic m a t e rials).
Fo r a h ypo th eti cal d e fau lt land fill d i sp osal scen ari o , p a rameter v a l u es m a y b e b a sed o n n a tio n a l
d a ta fo r d i fferen t land fill typ e s, or d e fin e das a po licy m a t t e r
. Valu es fo r fi eld pH and LS ratio m a y b e eith er
measured at a nactual site or e s ti m a ted for the site. Measuring field pH requires c o llecting landfill leacha t e

o r

land fill po re water andm easu r i n g th e pH b e fo re co n t act with th e air b e g i n s to alter the pH. LS ratio

serve s as t h e s u rrogate param e ter fo r ti m e . Good ag reem en t h a s b een ob t a in ed b e tween lab o rato ry test d a ta
and landfill leachate ba sed on LS (va n der Sl oot, 2001)

. Measuri n g field L S ratio invol ve s m easuring the

v o l u m e o f leach a te co llected (an n u a lly) fro m th e landfill, andco m p arin g it with th e estim a t ed waste vo lume
in th e lan d fill, o r th e lan d fill d e sign cap acity. As an alternativ e to m easu r in g t h e LS rati o , it m a y b e

est i m a t e d, base d on de fi ni ng t h e geom et ry fo r t h e m a nagem e nt sce n ari o a n d l o cal e n vi r o n m ent a l

co nd itio ns. Para m e ters for d e fin i n g th e m a n a g e m e n t scen ari o in cl u d e fill geo m etry (relati n g waste m a ss to
im pacted area ), net i n filtration rates (defi n ing am ount of water contact), a n d tim e fram e . For e x am ple, a
d e fau lt d i sp osal scen ari o m a y b e a fill h e igh t o f 10 m , 20 cm in filtration p e r year an d 100 years (altern ativ ely, t h e to tal m a ss of waste and fo otp r in t a r ea m a y be specifie d ). The selection of the de fault

12Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

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man a g e m e n t scen ari o is u ltimatel y a con s id eration o f typical waste m a n a g e m e n t p r actices and o f so cietal

v a lu e ju dg m e n t s reflected in t h e regu lato ry dev e lop m en t p r o cess.
For di sc ussi on pu r poses , a 1 0 0 -y ear i n t e r v al i s su ggest e das a hy pot het i cal assessm ent per i od,
al t hou g h ot he r t i m e fram e s coul d be use d 8 . For c o m p arison of treated wa stes , a c u be one m e t e r on ed ge i s

assu m e d

. Lab o rato ry test results are presen ted p r im ar ily as release per unit mass of waste t e sted (e .g., m g X/kg waste), but also are pres ented a n d use d on a c o ncent r a tion basis for T i er 2 testing.

Environmental Considerations

Release esti m a tes for m o st cases assu m e th at co nd itio ns influ e n c ing release are con t ro lled b y th e

waste m a terial an d asso ciated d e sign con d ition s ; h o wev e r, prop erties o f su rroun d i n g m a ter i als m a y d o m in ate th e release con d ition s i n so m e scen ari o s. Th es e ex tern al stresses (e.g ., p H or red o x grad ien t s, carbonation, c o -m ingling eff ects) can lead to s u bstantial deviation from material-drive n leachi n g behavior.
Fo r in stan ce, cau tio n m u st b e u s edif larg e pH o r red o x grad ien t s ex ist between th e waste andth e

su rroun d i ng env i ro n m en t o r with in t h e wast e m a trix . Th e so lub ility o f m a n y ino r g a n i c sp ecies m a y b e

stron g l y a fu n c tio n o f pH (e.g ., Pb , C d , Ba) or sign ific an tly altered b y redox co nd itio ns (e.g ., Cr, Se, As). Large g r a d i e nt s i n pH o r re do x pot e n t i a l can resul t i np r eci p i t a t i on o r r a pi d di ss ol ut i o n ph enom ena f o r

s o m e
ele m en ts as con cen t r atio n grad ien t s with in th e m a terial or at t h e m a t e ri al bo u nda ry re di s t ri but e o v er l o ng
ti m e in terv als (v an d e r Sloo t et a l

. , 19 94 ; Sanch ez, 19 96)

. Th e r e lease of hi ghl y s o l u bl e s p eci es (e. g ., Na , K, Cl) is no t co n s i d ereda stro ng fun c tion o f leach a te cond itio ns.
Red o x g r ad ien t s and redu cing co nd itio ns m a y resu lt fro m m a terial ch aracteristics, b i o l og ical
activ ity o r ex tern al i n pu ts. Materials with i n heren t re du ci n g p r op er ties in cl u d e sev e r a l types of indu str i al
sl ag, fres h sedi m e nt and de g r adi n g or ga ni c m a t t e r. Test i n g o f t h ese m a t e r i al s un der ai r- e x p o se d c o ndi t i ons may leadto u n represen tativ e an swers fo r t h e situ atio n to be evaluate d. For an a p propriate assessm ent of
red u ci n g m a t e ri al s, t e st i ng a n d rel ease m ode l i ng t h at co nsi d ers co n d i t i ons im pose d by ex t e rnal fa ct or s,
rather tha n by t h e waste itself, will be necessary . This is still an unde rde v e l ope d a r ea of research.
For m o st alkaline wastes, t h e m o st prevale n t inte rfac e react ion is abs o rpti on of ca rbon dioxi de.
Carbo n a tion of waste m a terial s resu lts in t h e form at i on of c a rb o n at e speci es an d ne ut ral i zat i on of al kal i n e
bu ffe ri n g ca pa ci t y . For P o rt l a nd cem ent

- bas e d m a t r i ces, t h e co nve rsi o n o f cal ci um hy dr oxi de t o cal ci u m
carb o n at e has beenn o t e d t o r e duce p o r e wat e r pH t o war d s 8 (Sa n chez , 20 01; Ga rra bra n t s , 2 0 0 1 )

. T hus , i f

13Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

p H

- d ep end e n t sp ecies ar e a co n c ern , car bonatio n o f th e m a tr ix can p l ay a sig n i f i can t ro le in p r ed ictin g lo ngterm release.
C u r r ent l y , t h e pr o pose da p pr oach does not consider the i m pact of co -m ingl i n g di f f ere n t t ypes o f

wastes d u ring d i spo s al o t h e r t h an th e im p act o f resu ltin g chan g e s in pH. In cases wh ere a p H grad ien t

appea r s t o be t h e m o st si gni fi cant fact or , rel ease est i m a t e s can be acc om pl i s hed usi n g a d vance dm odel i ng approaches in conjunction wi th cha r acterizat ion data inte rpolated fr om the concent r atio n as a fun c tio n of pH as defi ned un de r Ti er 2

. T e st m e t hods an d rel ease m ode l s t o asses s t h e im pact of m a t e ri al agi n g u nde r

car bon atio n and r e du cing cond itio n s ar e un der d e v e l o p m en t ( N V N 743 8, 2 000 ; G a r r a br an ts, 20 01 ; San c h e z et al. , 2 0 0 1 a )

. Ex peri m e nt al wo rk i s i n p r og ress t o e v al uat e wast e- wast e i n t e ract i o n by q u ant i f y i n g
buffe ring of pH, diss ol ve d organic ca rbon, a n d leaching fr om waste m i xtures (va n der Sl oot et al. , 200 1a;

vande r Sl o o t et a l

. , 20 01b ).



### TEST M E THODS FOR USE I N THE FRAMEWORK

CRITE RI A F O R E Q UILIB R IU M TEST METHO D S

Im portant c o ns iderations for t h e design of equilibrium test m e thods are (i) the relations hi ps
betwee n particle size, sam p le size and co n t act ti m e , (ii) d e fi n itio n of an app r op riate LS ratio , (ii) selectio n

o f

th e aci d o r alk a li for p H mo d i ficatio n , and (iii) pr actical m ech an ical li mits. Ex p e rim e n t al ob serv ation s
wi t h se veral w a st es ha ve i n di cat ed t h at use of a m a xim u m part i c l e si ze of 2 m m and co nt act t i m e of 4 8
h ours resu lts i n a reason ab le measu r em en t of eq u ilib ri u m (Garrabran ts, 19 98). If d i ffu sio nis assu m e dto b e
th e rate con t ro llin g m ech an ism , th e relatio nsh i p s b e t w een p a rticle size andco n t act tim e requ iredto

ap pro ach equ ilib riu m can b e ap pro x i m a tedas d i ffu sion from a sp h e re i n to a fi n ite b a th (Crank , 19 75). Critical p a rameters are th e fractio n o f con s t itu en t re leased at eq u ilibriu m , o b s erv e d d i ffusiv ity, p a rticle
d i am e t er andco n t act tim e. Th e ratio b e tween th e fraction o f con s titu en t rel easedat a g i v e n tim e an d th e
fraction o f th e co nstitu en t released at equ ilib riu m can b e consid ered an ind e x o f th e app r o a ch to

eq u ilibriu m . Resu lts of sim u latio n s u s ing t h is m o d e lin g appro a ch are co nsisten t with app r o ach i n g
eq u ilibriu m after 4 8 hou rs fo r ob serv ed d i ffusiv ities less th an 1 0 -14 m 2 /s (G arra bra n ts, 1 9 9 8 )

.

8 Th e au t h or s hav e f oun d 100 year s to b e a usef u l p e r i odfor r e lease estimates. Th is p e r i odis typ i cally l o n g er t h a n a l i fet i m e but s h ort eno u g h t o be com p rehe ndi bl e. I n a d di t i on, f o r

m a ny cases, a m a jor fract i o n o f

th e l o ng -term release is an ticip ated to o c cu r du ri n g a p e rio dless th an this in terv al.

14Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.
Equ ilib ration times for d i fferen t p a rticle size syste m s, a ssumin g all o t h e r p r op erties rem a in

co nstan t (e.g., o b s erv e d d i ffusiv ity, liq u i d-so lid ratio , fract io n a l release at equ ilib riu m ), can b e ev alu a t e d
usi n g a di m e nsi onl ess t i m e param e t e r:

2 r t D obs

⋅ = τ (Eq u at i o n 1 )

w h er e τ is th e d i m e n s io n l ess tim e p a ram e ter [-];

t is th e co n t act ti m e [s];

r is th e p a rticle rad i u s [m ]; an d , D obs is th e ob serv ed d i ffu s i v ity [m 2 /s].

Based o nth is ap pro ach, ach i ev ing a con d ition eq u i v a le n t t o th e 2 mm/4 8 hr case, a p a rticle size of 5 mm

wo ul d re q u i r e ext r act i o n fo r 12 .5 day s ; fo r a pa rt i c l e si ze of 9 m m , 40.5 day s w o ul d be req u i r e d

. H o w e ver ,

m o st m a t e ri al s un de rg oi n g t e s t i ng wo ul d be s i zed re d u ced or n a tu rally have a p a rticle size d i stribu tion with
the m a xim u m particle size s p ecified. Thus, a m a xim u m pa rt i c l e si ze of 2 m m wi t h a 4 8 hr m i nim u m cont act
tim e is specified as a base cas e, with alternat iv e cond itio n s su gg estedco nsid ering bo th equ i v a len t

ap pro ach es to eq u ilibriu m an d p r actical li m i tatio n s (T ab le 1 ) . Dem o n s tratio n of ap prox i m atin g equ ilib riu m

co nd itio ns for t h e m a terial b e in g testedis reco mmen d e d befo re u s i n g altern ativ e co n t act t i m e s.
Sel ect i on of sa m p l e si zes assum e s t e st i ng o f re prese n t a t i v e al i quot s o f t h e m a t e ri al bei ng
eval uat e d. F o r t h e ba se case wi t h a m a xi m u m part i c l e si ze of 2 m m , a sam p l e si ze of 40 g (e qui val e nt dry
wei g ht ) i s rec o m m e nded whe n ca rry i n g out an e x t r act i o n a t an L S rat i o of 1 0 m L / g . Het e ro ge neo u s
materials an d materials with a larg er p a rticle size will require eith er testin g o f larg er aliqu o t s or
hom oge ni zat i o n a n d pa rt i c l e s i ze red u ct i o n p r i o r t o su b- sam p l i n g f o r

t e st i n g. A di sc ussi o n an d e x am pl e o f

sam p ling of he terogene ous materials and particle size reduc tion followe d s u b-sam p ling for leachi n g tests is

p r ov id ed elsewh er e (I AW G, 19 97)

. For m a ny t e st m e t hods , a n L S rat i o o f 10 m L / g has been s e l ect ed t o pr o v i de ade q uat e e x t r act

v o l u m es fo r sub s eq u e n t filtrat io n andan alysis wh ile u s i n g stan d a rd size extractio n con t ain e rs (i.e., 50 0

m L ). Th is liqu i d

- t o -so lid ratio also p r ov id es fo r reas on ab le ap pro ach to equilib riu m b a sed o nth eo retical

co nsid eration s . Typ i cally, u s e of an LS ratio o f 10 m L /g prov id es so l u b ility-con tro lledequilib riu m o v e r th e

ran g e of p H rel e vant f o r e x t r a pol at i o n t o t h e fi el d. Th e resu l tin g so lu tion co n c en tration is g e n e rally on ly

15Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

weakl y depe n d e nt o n LS rat i o bet w ee n LS ra t i o o f 10 an d 2 m L / g
. LS rat i o de pen d e n ce m a y be veri fi e d
usi n g a n e x t r ac t i on at l o we r L S (see m e t hods bel o w )

. Int h e e x peri m e nt al m e t hods, pH ad j u st m e nts are m a de u s i n g al i q u o t s of ni t r i c aci d o r p o t a ssi um
h ydr ox id e. Nitric acid was cho s en to m i n i mi ze th e p o t en tial fo r precip itatio n (e.g., su ch as o c cu rring with
sul f uri c aci d), com p l e xat i on ( e .g. , wi t h or ga ni c aci ds o r hy dr oc hl ori c a c i d ) or a n al y t i cal i n t e rfe re nces. It i s
also recog n i zedth at n itric aci dis ox id izing wh ich is a con s erv a tiv e selectio n du e t o th e so lub ility b e h a vio r
of

m e t a l hy dr o x y l speci es (e. g ., P b ( O H ) 3 - , C d ( O H ) 3 - ) andt h e p o t en tial for ox id izing cond itio n s du ri n g

m a nagem e nt . Ho we ver , oxy a n i o ns (e. g ., ch r o m a t e ) exhi b it max i m u m release at n e ar n e utral to sligh tly
alk a lin e co nd itio n s th at typ i cally are ach iev a b l e withou t sign ifican t aci d ad d ition s . Testin g fo r release u n d e r
red u ci n g c o ndi t i ons req u i r es t h e devel opm en t of ad di t i onal t e st m e t hods be cause c o nsi d e r at i on m u st be gi ve n t o aci d s e l ect i on, sam p l e ha ndl i n g a n d est abl i s hm ent of re pr o duci b l e re duci n g co n d i t i ons. Pot a ssi u m
h ydr ox id e w a s selected to avoid in terferen ce with th e use o f sod i u m io n as an in ert tracer i n so m e
ap p lication s ; ho wev e r, sod i um h y d r ox id e m a y b e sub s titu tedfor cases in wh ich p o t assi um ch aracterizatio n
is a concern.
Du ri n g e x t r act i o n , c o m p l e t e m i xi ng s h oul d be i n su red by e n d

- ove r-e n dm i xi ng
. Inal l cases, i t i s
desi re d t o t e st t h e m a t e ri al wi th t h e m i nim u m am ount o f m a ni p u l a t i on o r m odi fi cat i on n eeded p r i o r t o
extraction. Thus, it is prefe r a b le to avoid sample drying before testin g, although this can be accepta ble
whe n non-vola tile constituent s are of prim ary interest and it is necessa ry to ac hieve pa rticle size re ducti on.

RECO M M E NDE D TEST METHO D S
The following test m e thods are rec o m m e nde d for use i n the proposed tiere d leachi n g fra m ework.
The ge neral p u r p o se, ap p r oac h a n d ap pl i cat i o n o f t

h ese t e st m e t hod s are s h o w n i n Ta bl e 2. Det a i l e d

pr ot oc ol s fo r t h ese t e st m e t hods are p r ese n t e d as A p pen d i x A.

Tier 1 – Scree ning Tes t s
An id eal screen ing test wou l d resu lt in a con s erv a tive e s timate of release over the broa d ra nge of

an ticip atedenviron m en tal co nd itio n s . In add itio n , t h is screen ing test wou l d requ ire on ly a sing le ex tractio n
th at cou l d b e co m p leted in less th an 2 4 hou rs. Howev e r, this ideal sce n ari o is im possible t o ac hieve. Se veral approaches to measuring “availability” or maxim u m leach i n g potential ha ve been de vel o ped or c o nside r ed.
On e appro a ch i s a two step seq u e n tial ex tr ac t i on pr oce d u r e wi t h part i c l e si ze <3 00 μ m, L S = 1 0 0 mL / g a n d

16Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

co n t r o l at pH 8 and 4 ( N EN 73 41 , 199 4) . Ano t h e r ap pr o a ch u s es EDTA to ch elate m e tals of in ter e st in
sol u t i o n at nea r neut ral p H du ri n g a si ngl e ex t r act i on (Ga r r a bra n t s a n d K o s s on , 20 0 0 )

. Ei t h er o f t h e s e approaches can be use das a sc reeni n g test, but bot h a p p r oac h es ha ve pract i cal l i m i t a t i ons rel a t i v e t o
i m p l e m en tatio n
. Th e NEN 734 1 9 requ ires a small p a rticle size, tw o e x t r act i ons a n d p H c o nt r o l

. T h e
ap pro ach of Garrab r an ts an d Ko sson (200 0) req u i re s a p r e-titratio n andcan h a v e so m e d i fficu lties in

co n t ro lling th e p H . Th is ap proach also h a s b e en criticized as prov id i n g a rel ease esti m a te t h at m a y b e to o
conservative.

T i er 2 - S o l ubi l i t y and Rel e a s e as a Fun c ti on of p H

Th e ob j ectiv es o f th is testing i s to d e term in e th e acid / b a se titratio n bu fferi n g cap acity o f th e tested
material an dthe liq u i d-so lid partitio n i ng eq u i lib riu m o f t h e “co nstitu en ts of p o t en tial co ncern ” (C OPCs).
Fo r wastes wit h h i gh lev e ls of COPCs, t h e liq u i d

- so lid p a rtitio n i ng eq u ilibriu m is d e term i n ed b y aqu e ous

so lub ility as a fu n c tion of p H

. Fo r low lev e ls o f COPCs, eq uilib riu m m a y b e do m i n a tedby ad so rp tio n
p r o cesses. Howev e r, th e concu r ren t release o f o t h e r con s titu en ts (e.g ., d i sso l v e do r g a n i c carbon , o t h e r i o n s )
will also im p act th e resu lts b y m o d i fyin g th e so lu tion ch aracteristics o f t

h e aq u e ou s ph ase 10 . The tw o
ap pro ach es th at h a v e b e en con s id ered fo r ach i ev ing t h e ob jectiv e of m easu r i n g so l u b ility and release as a
fu nct i o n of p H are (i ) st at i c (c ont rol l e d ) pH t e st i ng at m u l t i pl e p H val u e s t h r o ug h use o f a p H c ont rol l e r at
desi re d set p o i n t s ( v a n der Sl oot et al. , 199 7), and (ii) a series of p a ra llel ex traction s o f mu ltip le sam p le
al i quot s usi n g a ra nge o f a ddi t i ons of aci d o r al kal i t o ac hi e v e t h e de si red r a nge o f e n dp oi nt p H val u e s (En v i r o n m e nt C a nada an d Al bert a E n vi r o n m ent a l C e nt er, 19 8 6 ; K o ss o n et al. , 1 9 9 6 ; K o ss on an d va n der
Sl oot , 1 9 97; p r EN 14 4 2 9 , 20 0 1 )

. B o t h t e st i n g a p p r oaches h a ve beens h o w n t o p r ovi de si m i l a r resul t s ( v an
d e r Sloo t an d Ho ed e, 199 7), in clu d i n g determin atio n of both th e aci d / b a se titratio n b u ffering cap acities of
th e tested m a te rial and th e ch aracteristic b e h a v i or o f t h e co nstitu en ts of po ten tial con cern
. Th e static p H

app r oach has t h e a dva nt ag e o f bei n g a b l e t o achi e ve desi re d pH en d poi nt s wi t h a hi gh de gree o f acc urac y
. The paral l e l e x t r act i on a p pr oa ch has t h e a dva nt age o f m echanical sim p lic ity. Th e r a n g e of pH ex am in ed
sh ou l din cl u d e th e ex t r em e v a lu es o f pH an ticip ated u n d e r fieldcon d ition s andth e pH when co n t ro lled by
the tested m a te rial (i.e., “ n atural ” or “own” pH). T hus , whil e the r ecom m ende d m e t hod b e l o w p r o v i d es a

9 NE N i s t h e na t i onal D u t c h st anda r d i zat i on or ga ni zat i on, whe r e a st an da rdi zat i o n c o m m i tt ee has bee n addressi ng the devel opm ent of leachi n g tests for c o nstruction m a terials and waste m a terials since 1983. Fo r ad d ition a l in fo rm atio n , see w w w
. ne n. nl o n th e In tern et

. 10 For ex am p l e, th e d i sso l u tio n o f org a n i c carbo n fro m a wast e h a s b e en shown to i n crease th e so lub ility o f cop p e r i n m uni ci pal sol i d was t e i n ci nerat o r ( M S W I ) bot t o m ash and se ve ra l m e tals in m a trices containi ng or ga ni c m a tt er (va n der Sl o o t , 2 0 0 2 )

.

17Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

full c h aracteris tic beha vio r c u rve (i.e. , fo r Ti er 2, le vel B t e st i ng) , a n a b b r evi a t e d versi o n base d o n t h ree
anal y s i s p o i n t s m a y be u s ed f

o r

si m p l i f i e d t e st i ng (i .e., f o r Ti er 2 A ). T h e r ecom m e nde d m e t hod bel o w i s
also a n alogous to CE N TC 292 C h ar acterizat ion of Waste – Leaching Be havior Test – pH Depe ndence T e st
with In itial Aci d /Base Add itio n (prEN144 29 , 20 01).

SR0 0 2

. 1 (Alk alin ity, So lub ility an d Release as a Fun c tio n of p H ) Thi s pr ot oc ol c onsi s t s o f 11 p a ral l e l ext r act i ons o f p a rticle size redu cedm a terial at a liq uid

- to-so lid
ratio o f 10 m L ex tractan t/g dry sam p le. An acidor b a se a ddition sc hedule i s form ulated for eleve n e x trac ts
wi t h fi nal s o l u t i on p H val u es bet w ee n 3 a n d 12 , t h r o u g h a d di t i on o f al i q u o t s of H N O 3 or KO H as n e ed ed

. The e x act sc he dul e i s ad j u st e d base d on t h e nat u re of t h e m a t e ri al ; ho weve r, t h e ra n g e of pH val u es
in clu d e s th e n a tu ral p H of th e matrix th at m a y ex tend t h e p H dom ai n (e. g
. , f o r

ve ry al kal i ne o r aci di c

m a t e ri al s). Usi n g t h e sche d u l e , t h e e q ui val e nt s of aci d or b a se are a d ded t o a c o m b i n at i o n of dei oni ze d (D I)
water andth e particle size redu ced m a terial. Th e fin a l liqu i d

- so lid (LS) ratio is 10 m L extractan t/g d r y

sam p l e whi c h i n cl u d es DI wat e r, t h e a dde d a c i d o r base, an d t h e am ount o f m o i s t u re t h at i s i nhe rent t o t h e

waste m a trix as d e term in ed by m o istu re co nten t an al ysis. T h e eleve n extra c tions a r e tum b led i n a n e n do v e r - e nd f a sh i o n at 28± 2 rp m. Con t act ti m e is a fu n c tio n of the selected maxim u m particle size, with a n

ext r act i o n peri od o f 4 8 hr f o r t h e ba se case o f 2 m m m a ximu m part i c l e si ze. F o l l o wi ng g r oss se pa rat i o n of
th e so lidan d liq u i d p h a ses b y cen trifug ation o r settlin g , leach a te pH m easurem en ts are taken an d th e ph ases
are sep a rated by v acuu m filtratio n thro ugh 0

. 4 5 -μm p o l yp rop y len e filtratio n m e m b ran e s. An alytical

sam p les of the leachates are c o llected a n d preserve d a s a p propriate for c h e m ical analysis . T h e acid and base

neut ralization beha vior of the m a teri als is evaluated by pl otting the pH of each e x tract as a function of equi val e nt s o f aci d o r base a d ded pe r gram o f dry s o l i d

. Eq ui val e nt s o f ba se are p r esent e d as o p posi t e si gn

o f

acid equ i v a l e n t s. C o n c en tratio n o f con s titu en ts of in terest for each ex tract is p l o tted as a fu n c tion o f

ex tract fi n a l pH to pro v i d e liq u i d

- so lid p a rtitio n i ng e q u ilibriu m as a fu n c t i o n of p H . Fi gu re 2 (a-b) shows

co n c ep tu al ou t p u t fro m th e reco mmen d e d SR0 0 2

. 1 p r o t o c o l with th e reco gn itio n th at a b r o a drang e o f
b e h a v i ors is possib l e. In Figu re 3 a , th e ou tput d a ta of t h e SR0 0 2

. 1 p r o t o c o l fo r a cem en titio u s syn t h e tic

waste m a trix (Garrabran ts, 20 01) is co m p ared to th e t o tal ele m en tal co n t en t and con s titu en t av ailab ility (Tier 1 value )

. Th e abb r ev iated v e rsi o n of t h e SR002 .1 -A (Alk alin ity, So l u b ility an d Release as a Fun c t i o n of p H )

pr ot oc ol c onsi s t s of t h ree para l l e l ext r act i ons o f part i c l e size red u c ed m a terial at a liq u i d-to -so lid ratio o f 10

m L ex tractan t/g d r y sam p le. Th e selection of th e targ et pH v a lu es is d e p e nd en t on th e natu ral pH o f t

h e

18Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

material. If th e n a tural p H is <5 , t h en n a t u ral p H , 7 an d 9 a r e selected as t h e target pH va lues. If the nat u ral pH ra n g es bet w een5 an d 9, t h en5 , 7 a n d 9 are selected as the target pH valu es, andif t h e n a tural p H is >9 , then 5, 7 and natural pH are s e l ected as the target pH value s
.

T i er 2 - S o l ubi l i t y and Rel e a s e as a Fun c ti on of L S R a ti o
Th e ob j ectiv e o f th is test is to d e term in e th e effect o f low liq u i d

- t o -so lid ratio on liqu i d-so lid

p a rtitio n i n g equ ilib riu m wh en th e so lu tion ph ase is con t ro lled b y th e tested m a terial. Th is is u s ed t o approxim a te initial pore

- water conditions a nd initial l eachate com positions in m a ny perc ol ation sce n ari o s (e.g., m onofills ). T h is objective is accom p lished by a seri es of parallel extractions using m u ltiple aliquots of
th e testedm a te rial at d i fferen t LS ratio with d e io ni zed wat e r t o achi e ve t h e desi re d ra nge of co n d i t i ons.
Whe n necessa ry, res u lts can be extra p olated to lo wer LS rat i o t h a n readi l y achi e ve d un de r t ypi cal
lab o rato ry cond itio n s . Th e ran g e of LS ratio ex am in edsh ou ldi n clud e t h e con d ition u s ed fo r so l u b ility an d
rel ease as a f

u n c t i on of p H t e s t i ng (i .e., LS= 1 0 m L /g) and t h e lowe st LS practically achie vable t h at

app r oaches t yp i cal po re wat e r sol u t i ons (i .e ., LS= 0

. 5 m L / g ). T hus , whi l e t h e recom m ended m e t hod bel o w provides a full characte r istic behavi or curve (i.e., for Ti er 2, lev e l B testin g), an abbrev iated v e rsi o n b a sed

o n two an alysis po in ts m a y b e u s ed for sim p lifiedtestin g (i.e., for Tier 2A) 11

. Fo r so m e m a te rials, LS <2 mL/g m a y b e d i fficu lt to ach i eve with sufficien t qu an tity o f elu a te fo r

an alysis du e to li m i tatio n s of so lid -liqu i d sep a ration

. I n a d di t i on, t h e f o r

m at i on o f l eac hat e col l oi ds c a n

resu lt in ov eresti m a tio n o f rel ease fo r so m e metals an d o r gan i c con t am in an ts. Use o f a co lu m n test is an
altern ativ e to use of b a tch test in g fo r m easu r i n g re lease as fu n c tion of LS. A co lu m n test (prEN144 05 , 20 0 1 ) , si m i l a r t o t h e D u t c h st a nda r dc o l u m n t e st (N EN 7 3 4 3 , 1 9 9 5 ) , has be en devel ope d wi t h i n t h e European Standardization Organization CE N.

SR0 0 3

. 1 (So l ub ility an dRelease as a Fun c tio n of LS Ratio) Thi s pr ot oc ol c onsi s t s o f fi ve paral l e l bat c h e x t r act i o ns ov er a ra n g e of LS rat i o s (i .e., 1 0 , 5, 2, 1 , and 0

. 5 m L / g dr y m a t e ri al ), us i ng dei o ni ze d ( D I ) wat e r as the ex tractan t wi th aliq uo ts o f material th at h a s been pa rticle size re duce d . T h e m a ss of m a te rial use d for the test v a ries wi th th e p a rticle size o f th e
material. All ex traction s are co ndu cted at room te m p erature (20±2 o C ) in leak -p roo f v e ssels th at are tu mb led
in an end-over-end fas h ion at 28±2 rp m
. Co ntact ti m e is a fu n c tion of th e selectedm a x i m u m p a rticle size,
wi t h a n e x t r act i on pe ri o d of 4 8 hr f

o r

t h e bas e case of 2 m m m a xim u m part i c l e si ze. Fo llowing g r o ss

19Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.
separation of t h e solid a n d liquid phases by c e ntri fugati on or settling, leach ate pH and c onductivity

measu r em en ts are tak e n andt h e p h a ses are sep a rated b y a co m b in atio n o f p r essure an d vacu u m filtratio n

u s ing 0

. 45 -μm p o l ypro p y len e filter m e m b ran e . Th e fi v e leach a tes are co llected , an d preserv e d as appropriate for chem ical analysis. Figure 2 (c-d) s h ows co n cept u al out p u t fr om t h e reco m m e nded SR 0 0 3

. 1

pr ot oc ol wi t h t h e reco g n i t i on t h at a b r oad ra nge o f be havi o r s i s po ssi bl e. I n Fi gu re 3 b , t h e o u t p ut dat a o f

eq u ilibriu m -b ased p r o t o c o l s (SR0 02 .1 and SR0 0 3

. 1 ) are com p ared fo r a ce m e n titio u s sy n t h e tic waste

matr ix ( G ar r a br an ts, 200 1)

. Th e abb r ev iated v e rsi o n, SR 00 3.1-A (So l u b i lity a n dRelease as a Fun c tion of LS Ratio ) pro t o c o l

co nsists of two p a rallel ex tractio n s o f p a rticle size red u c ed material u s in g DI water at liqu i d-to -so lid rat i o of
10 an d 0. 5 m L ext r act ant / g dr y sam p le, respectiv ely. Th e ex traction at an LS ratio of 10 m L /g m a y b e th e

sam e sam p le as use di n SR 002. 1

- A t o re duc e the require d num ber of anal yses.

T i er 3 - M a ss T r ansf er Ra te ( M o n ol i t hi c a nd Com p ac te d Gr anul ar M a teri al s)

Th e ob j ectiv e o f m a ss tran sfer rate tests is to m easu r e th e rate o f COPC rel ease fro m a m o n o lith ic material (e.g ., so lid ified waste fo rm o r con c rete m a tr ix) or a com p acted granula r m a terial . Resu lts o f th ese
tests are to estimate in trin sic mass tran sfer param e ters (e.g., ob serv ed d i ffu siv ities fo r C O PCs) th at are th en

u s edin conj unctio n with o t h e r testin g resu lts andasse ssm ent m odels to estimate release. Results of t h ese

tests reflect b o t h p h y sical an d ch em ical in tera ctio n s with in th e tested m a tri x , t h us requ iring ad d ition a l test
resul t s fo r i n t e grat e d asses s m e nt . Whi l e t h e recom m ended m e t hods are de ri vat i v es o f A

N S 1 6

. 1 ( A NS,
1 986 ), a leach a b ility in d e x is n o t assu m e dno r u s ed as a d e cisio n criterion. Th e reco mm e n d e dm e th o d s
bel o w a r e al so anal o g o u s t o N E N 7 3 4 5 (N E N 73 4 5 , 1 9 9 4 ) and m e t hods u nde r de vel o pm ent by C E N/ T C
29 2.

MT0 0 1

. 0 (Mass Tran sfer Rates in M o no lith ic Materials) This protoc ol c onsists of tank leaching of c o n tinuously wat e r-sat urated mo nolithic m a ter i al with peri odi c ren e w a l of t h e l eac hi ng sol u t i o n. T h e vessel a n d sa m p l e dim e nsi ons a r e c h o s en s o t h at t

h e sam p l e
i s ful l y i m m e rsed i n t h e l eac hi ng sol u t i o n. C y l i nders o f 2 cm m i nim u m di am et er and 4

- c m m i nim u m hei ght
or 4-cm minimum cubes a r e c ontacted wit h DI water using a liqui d to s u rface area ratio of 10 m L of DI

water fo r e v ery cm 2 of expose d s o lid s u rface area. La rger cylinder sizes are rec o mmended for t r eated
materials that have a particle size greate r tha n 2 mm p r io r t o so lid ification. Typ i cally, th e cylin d e r d i ameter

11 The abbre v iat e d m e thods for testing s o lubil ity as a function of pH (three poi nts) a n d s o l ubility as a

fu nct i o n of LS (t w o poi nt s) i n cl ude o n e c o m m on poi nt i n b o t h t e st s. T hus , f o r i n t e g r at ed t e st i ng un der T i er

20Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

and hei ght o r c ube di m e nsi o n sho u l d be at l e ast t e n t i m es t h e m a xim u m part i c l e si ze of t h e m a t e ri al

cont ai ne d t h ere i n. Leac hi n g so l u t i on i s exc h a nge d wi t h fresh DI water at pre-d e term in ed cu m u lativ e ti mes
of

2 , 5 a n d 8 h o u r s, 1 , 2, 4 a n d 8 day s 12 . Thi s sche dul e res u l t s i n se ve n l eac h a tes with leach i ng in terv als o f
2 , 3 , 3, 1 6 hou rs, 1, 2 and 4 d a ys. At t h e co mp le tio n of each con t act p e riod, th e m a ss of the m o n o lith ic

sam p l e aft e r be i ng freel y drai ned i s rec o rde d t o m oni t o r t h e am ount o f l e a c hant a

b s o r b e d i n t o t h e s o l i d
matrix. The s o lution pH a n d c o nductivity for each leac hate i s m eas ured for each tim e interval. A leachate

sam p le is p r epared fo r ch em i cal an alysis b y v acuu m filtrati o n throug h a 0

. 4 5 -μm p o r e size po lyp r op ylene
filtration m e mbra ne a n d preservation as appropriate. Leachate conc entrat i ons are pl otted as a function of
tim e along with the analytical det ection lim it and the equilibri um con cent r ation determ ined from SR002.1
at the ext r act pH for quality cont rol t o insure that release was not limited by sa turation of the leachate.
Cu m u lativ e release and flux as a fun c tio n of ti m e fo r each co n s titu en t o f i n terest are p l o t t e d an d used to
esti m a te mass tran sfer p a ram e ters (i.e., ob serv ed d i ffu s iv ity). Fi gu re 4 shows sam p le ou tp u t d a ta fro m t h e
MT0 0 1

. 1 test fo r a so lid ified waste m a trix (v an d e r Sl oo t, 1 999 ). Th e so l u b ility d a ta sho w n i n th e fi g u re

cor r es po n d s t o dat a de ri ve d fr om SR 00 2. 1.

MT002.0 (Mas s Tra n s f er Rate s in C o m p acted Gra n ular Ma terials) This protoc ol c onsists of tank leaching of c o ntinuously wat e r-sat urated c o m p acted gra n ular
material with in term it ten t renewal of t h e leach i ng so lu tion

. Th is test is u s ed wh en a granu l ar m a terial is

ex p ected t o b e h a v e as a m o n o lith b e cau s e of co m p actio n du ri n g field p l ace m en t. An u n c o n s o lid ated o r
g r anu l ar m a teri al is co m p acted in t o m o ld s at op ti m u m m o istu re con t en t u s in g a m o d i fied Procto r

co m p activ e ef fo r t ( N EN 734 7, 199 7) . A 10-c m dia m eter cylindrical m o ld is u s ed and th e s a mp le is p a c k e d

to a dept h of 7 c m . The m o ld and sam p le are imm e rsed in deionized wate r suc h that only the s u rface a r ea of
the top face of the sam p le contacted the leac hing m e dium , without m i xi ng. T h e leacha n t is refres hed wi th

an e qual v o l u m e of dei o ni ze d wat e r usi n g a l i qui d t o su rfa ce area rat i o of 1 0 m L / c m 2 (i. e ., L S ratio of 10

cm ) at cum u l a ti ve t i m e s of 2 , 5 a n d 8 h o u rs , 1, 2, 4 an d 8 da y s (see fo ot n o t e 1 2 )

. T h i s sc h e dul e res u l t s i n

seve n leachate s with leaching interv als of 2, 3, 3, 16 hours, 1, 2 a n d 4 days . T h e s o lution pH and conductivity for eac h leachate is m easured for eac h tim e interval. A leacha t e sam p le is prepare d for
ch em ical an aly s is b y v acuu m filtratio n t h ro ug h a 0

. 4 5 -μm p o r e size po lypro p y len e filtratio n m e m b ran e an d

2, four a n alysis points a r e recommended. 12 Th is sch e du le may b e ex ten d ed for ad d itional ex trac tion s t o p r ov id e m o re in fo rm atio n ab ou t long er-term rel ease. T h e re com m e nded sc hed u l e e x t e nsi o nw o ul d be a d di t i onal c u m u l a t i v e t i m e s 14 day s , 2 1 day s , 28 day s , a n d e v er y fo ur wee k s t h erea ft er as d e si red. Al t e r n at el y , t h e d u r at i o n of t h e t e st m a y be s h ort e ne d (e.g ., cu m u lati v e tim e o f 4 d a ys) fo r co m p lian ce testing

.

21Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

prese r vation as appropriate. L eachate c once n trations a r e plotted as a functi on of tim e along with the analytical detection lim it and the eq uilibri um concent r ation determ ined from SR002.1 at t h e e x tract pH for

q u a lity con t ro l. Cu m u lativ e release andfl u x as a fun c tio n of tim e fo r each co nstitu en t o f in terest are p l o tted
and u s ed to est i m a te m a ss transfe r param e ters (i .e., o b se rve d diff usi v ity ).



### RELEAS E ASSES S MENT ESTI MATES

Release estim a tes m a y be obt a ined for site-s pecific a n d m a nagem e nt scenario-specific ca ses whe n
app r op ri at e en vi r onm ent a l da t a (e. g ., p r eci pi t a t i on f r eq ue nc y and am ount s ) a n d desi gni n fo rm ati on (e. g
. , placem ent geometry, infiltration rates) are available. For m a ny situations , site-specific inform ation either

m a y not be rea d i l y avai l abl e or m a y not be necessa ry (e. g
. , as i n t h e case whe n t h e i n t e n t of t e st i ng i s o n l y

t o p r ovi de uni f o rm si de- b y - si de c o m p ari s on s o f t r eat m e nt pr ocesses )

. F o r t h ese si t u at i o n s , d e fa ul t scena r i o s

m a y be de fi ne d; anap pl i cat i o no f t

h i s ap p r oach i s pr ovi de d i nt h e c o m p ani o n pape r (Sa n chez et al

. , 200 2)

. Th ese d e fau lt scen ari o s are for illu strativ e purpo ses on ly, and o t h e r p a ram e ter v a l u es m a y b e m o re
app r op ri at e f o r

di f f ere n t m a nagem e nt scenari o s a n d geo g ra p h i c l o cat i o ns.

Percolation-c ontrolled sce n ario

Perco l atio n - con t ro lled release o c cu rs wh en water flows t h ro ugh a p e rm ea b l e fill with low
in filtratio n rate and low liqu i d-to -so lid ratio (Fig ure 5 )

. In this case, lo cal eq u ilibri u m at fieldpH is assumed

to b e li m itin g release. The info rm atio n requ ired to estim ate co nstitu en t release du ri n g th is scen ari o is t h e (i)
field g e o m etry, (ii) field d e nsity, (iii) an ticipated inf iltratio n rate, (i v ) an ti cip a ted field pH, (v) an ticip at ed site-sp ecific liqu i d-to -so lid rat i o , an d (v i) constitu en t so l u b i l ity at th e an ticip ated field pH. Th e an ticip ated site-sp ecific liqu i d-to -so lid ( LS site ) ratio represen ts th e cu m u lativ e liq u i d-to-so lid ratio th at can b e exp ected

to con t act th e fill o v e r th e estimated ti m e p e rio d

. It is b a sed o n th e i n filtratio n rate, th e con t act ti m e , th e fill
d e nsity an d th e fill g e o m etry a n d can b e d e te rmin edacco r d i n g to (Hj e lm ar, 19 90 ; Kosson et al. , 19 96) :

H

t inf 10 LS fill year site

⋅ ⋅
= ρ (Eq u at i o n 2 )

whe r e, LS site is th e an ti cip a ted site-specific liq u i d-to-so lid ratio [L/ k g ] ;
in

f

is th e an ticip atedi n filtratio n rate [cm / ye ar];

t year the estim a ted tim e period [year];
ρ is th e fill d e nsity [k g / m 3 ];

22Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

H fill

is th e fill dep t h [m ]; an d,
10 i s a c o nve rs i on fact o r [1 0 L/ cm - m 2 ].

O v er an i n ter v al o f 100 year s or long er , LS site values greater than 10 m L /g may be obtaine d for cases that
have relatively high rates of infiltra tion or li mited placem e n t de pth (Kosson et al. , 1 996 ; Schr eu r s et al. , 2 000 ). How e ver , f o r

m a n y d i sp osal scen ar ios, th e ob ser v ed LS site has bee nl e ss t h a n 2 L/ k g ove r a pe ri o d o f

ca. 10 years and for an iso l ated landfill site with re du ced i n filtration , it may tak e 100 0 years to reach LS site

o f

1 L/kg ( J ohn son et al. , 1 998 ; Jo hn so n et al. , 1 9 99; H j el m a r et al. , 20 01 ).
An estim a t e o f th e cu m u lativ e m a ss release per u n it m a ss o f m a terial can th en b e ob tain ed u s ing
th e an ticip ated site-sp ecific LS ratio and t h e co nstitu en t so l u b ility at th e an ticip ated field pH ( S field pH ) according t o : ) ( pH field site t mass (S ) LS M year = (Eq u at i o n 3 )

whe r e, is th e cu m u lati v e m a ss o f th e co nstitu en t released (m ass b a sis) at ti m e t year t mass M year [m g/ kg] ; and , S field pH is th e co n s titu en t so lub ility [ m g / L] at th e pH v a lue co rresp ond ing to field pH.

Mass tran sfer -contr olled sc enario

Mass tran sfer-co n t ro lled scenario o c cu rs when infiltratin g water is d i v e rt edaroun d a low

p e rm eab ility fi ll o r p r ev en ted fro m p e rco l atin g throug h th e fill d u e to an i m p e r m eab le o v e rlay (Figu r e 6 ) or adjace nt high perm eability ch an n e ls. In t h is case, m a ss transp ort with in t h e so lid m a trix is rate lim i tin g
. Th e
in fo rm atio n req u i red to estimate co nstitu en t release during su ch scen ari o are th e (i) field g e o m etry, (ii) field density, (iii) initial leachable conte n t and (iv) obs e r ved diffusivity of th e species of c o nc ern.
Th e m ech an ism s o f release un d e r m a ss transfer con t ro l can b e q u ite co mp lex and co nstitu en tspecific. The rate of COPC di ffusion t h rough the m a terial can be retarded by s u rface rea c tions or preci pi t a t i on of i n s o l u bl e com p o u nds

. Al t e rn at el y , m a ss t r ansp o r t m a y be enha nce d by s p eci es

com p l e xat i on or m i neral pha se di ss ol ut i o n. Num e ri cal t echni q u es oft e n a r e re qui re d t o fu l l y descri be
release und er co m p lex m ech an istic con d ition s
. Soph isti catedm o d e ls h a ve b e en d e v e l oped , or are und er
devel opm ent , t o di ssol u t i on/ p r eci pi t a t i on p h e nom ena (B at c h el o r , 1 9 9 0 ; C h en g a n d B i sh op , 19 9 0 ; B a t c hel o r,
1 992 ; H i n s en veld , 1 992 ; Batch e lor an d W u , 1 993 ; H i n s en veldandBish op, 199 6 ; M o szko w i cz et al. , 19 96;
Sanc hez, 1 9 9 6 ; B a ker an d B i s h o p , 1 9 97; M o szk o wi cz et al. , 1 9 97; B a t c hel o r , 19 9 8 ; M o sz ko wi cz et al. , 19 9 8 ) , s o r p t i o n / deso rpt i o n p h e nom ena, a n d m a t e ri al het e ro genei t y ( S anc h ez et al. , 2001 b)

.

23Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

Fi cki a n Di f f u s i o n m odel

The Fi cki a n di ff usi o n m odel , base d onFi ck ’ s seco n d law, assu m e s th at th e sp ecies of in terest is
in itially p r esent th ro ugh ou t the ho m o g e n e o u s po rou s m e d i um a t

u n i fo rm co n c en tration an d con s i d ers that

mass trans f er t a kes place in response to c oncentration gra d ients in t h e pore water sol u tion of the porous

m e di um . The a ssum p t i ons a n d rel ease est i m at i on a p p r oach sh ow n he re i s m o st appr op ri a t e fo r rel ease
scenari o s for which only highl y soluble s p ecies are a co nce r n or f

o r

w h i c h ext e r n al st resse s (e. g
. , pH

g r ad ien t s, carbo n a tion , redo x ch ang e s) are no t sign ifican t.
In the classical re prese n tation of th e d i ffu sion m o d e l, two co up led p a ram e ters ch aracterize th e

m a gni t ude a n d rat e of t h e rel ease: C 0 , the i n itial leachable c onte n t (e .g., a v ailable release pote n tial, total
ele m ental cont ent) 13 and D obs , t h e ob ser v ed di ff usi v i t y o f t h e speci es i n t h e po r ous m e di um . W h e n t h e species of conc ern is not deple t ed ove r the time pe riod of interest, the cum u lative m a ss release can be
descri bed by a one - d i m ensi onal sem i -i nfi n i t e ge om et ry . Depl et i on i s co nsi d ere dt o occu r whe n m o re t h a n
20% of t h e tota l leachable c ontent has bee n released (de Groot, 1993).
For a o n e- di m e nsi o nal geom etry , a n a n al y t i c al sol u t i o n fo r F i cki a n di ff usi o n i s pr o v i d e d b y C r an k (197 5) with the sim p lify i n g assu m p tio n o f zero con c en tratio n at th e so lid-liq u i d i n terface (i.e., case of a

su fficien t water ren e wal; in fi n ite b a th assum p t i o n ) :

2 1        

⋅

⋅ ⋅ = π ρ t D C 2 M obs 0 t area (Eq u at i o n 4 )

w h er e is the c u m u lati ve m a ss of the constituent re leased (surface a r ea basis) at ti me t [m g/ m t area M 2 ];

C

0 is the initial leachable cont ent (i.e ., a v a ilable or t o tal elemental conte n t) [m g/kg];
ρ

is th e sam p le d e n s ity [kg / m 3 ];

t is th e tim e in t e rv al [s]; and , D obs i s t h e o b se rve d di f f usi v i t y of t h e s p eci e s o f c once r n [ m 2 /s].

The t e st c o n d i t i ons f o r

t h e M T seri es p r ot oc ol s (i .e ., MT001 .1 an d MT002 .1 ) ar e d e si gned to ensure a nondepl et i n g m a t r ix a n d ap p r o x i m at e t h e zero - conce n t r at i o n bo u nda ry , al t h ou g h fi el d c o n d i t i ons m a y not satisfy th ese si m p l i ficatio n s fo r m a n y cases an d th e resu ltin g release estimate m a y o v e resti m ate releas e.
There f ore, ot her m odeling approac h es m a y be require d to m o re accuratel y extra polate t o field c o nditions.

24Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

In release sce n arios for which CO PC de pl et i o n d o es n o t oc cur an d Fi cki a n di ff usi o ni s c onsi d ere d
th e do m i n a n t release m ech an ism , th e m a ss r e lease is pr opor tio n a l t o release ti m e b y a t 1/2 rel a t i ons hi p
. After
a l o g t r a n sf orm , E quat i o n 4 be com e s:

t D C 2 log M log obs

o t area log 2 1 2 1 +                

⋅ ⋅ = π ρ (Eq u at i o n 5 )

Thu s , t h e log a rith m o f t

h e cum u la tiv e release p l o tted versus th e l o g a rith m of tim e is ex pected to b e a straig h t line with a sl o p e of 0

. 5

. Often , in itial releas e as ob serv ed fro m lab o r at o r y testing reflects wash off

o r

d i sso l u tion o f surface-associated con s tituen ts. Th e app a ren t con s titu en t release th en m a y b e fo llowed b y diffusi o n-controlled release. Mass release over this initial ti m e when surface phenom ena are observe d

wou l d resu lt in a lin e with a slo p e greater t h an 0

. 5

. In t h ese cases, onl y t h e dat a p o i n t s re fl ect i ng di ff usi o nco n t ro lled release are u s ed t o esti m a te o b s erv e d d i ffu s iv ity. Th e in itial release shou ld b e verified t o b e
in sign ifican t i n relatio n to t h e lo ng -term field esti m a te o f rel ease (see San c h ez et al, 200 2 for an illu strati o n
of

t h i s phe n o m e na)

.

Estima tion o f ob served d iffu sivity
Un de r t h e ass u m p ti ons of t h e Fi cki a n di f f u s i o n m odel , an o b ser v e d di ff usi v i t y can be det e rm i n ed
for eac h leac hing interval where the slope is 0.5 ± 0.15 b y (de Gr oo t an d v a n d e r Sloo t, 199 2) :

2        

⋅ ⋅ = ) t

- t ( C 2 M D
1

- i i 0 t area obs i i ρ π (Eq u at i o n 6 )

w h er e i s t h e o b ser v e d di ff usi v i t y of t h e s p eci es of conce r n f o r l e a c hi n g i n t e rval i [m obs i D 2 /s ];

is the m a ss released (s urface area basis) duri ng leaching i n t e rval i [m g/m i t area M 2 ];

t i is the c ontact tim e after leaching inte rval i [s] ; an d,

t i-1 is the conta c t tim e after leaching inte rval i-1 [s]

.

Th e ov erall o b serv ed d i ffusivity is th en d e term in edb y tak i n g th e av erag e o f th e i n terval o b s erv e d
d i ffu s i v ities.

Release estimates

13 The val u e use d for the initial leachable cont ent an d t h e det e rm ined observed di ffusivity are c o upled param e ters suc h that t h e sam e set o f param e ters obt ai ne d fr om experi m e nt al dat a m u st be use di n d e term in in g lon g -term release esti m a tes.

25Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

An estim a t e of the cum u lative m a ss release for th e m a nage ment scenari o can the n be obt a ined

u s ing t h e an alytical so lu tio n (Equ atio n 4) o v er th e an ticip at edassessm en t in terv al. Wh en COPC release p e r
uni t m a ss of m a t e ri al i s desi re d, c o nve rsi o n b a sed o n m a t e rial fi el d geom etry can be ap pl i e d t o E quat i o n 4.

2 1        

⋅

⋅ ⋅ ⋅ = π t D V S C 2 M obs 0 t mass (Eq u at i o n 7 )

whe r e, is th e cu m u lati v e m a ss o f th e co nstitu en t released (m ass b a sis) at ti m e t [mg / kg ]; t mass M

S

is t h e fill surface area [m 2 ]; and , V

is th e fill vo lu m e [ m 3 ].

In th e case where in itial surface wash -off is co nsid ered t o prov id e sign ifican t con t ri b u tion to th e release

p r ed ictio n (i.e., >5 % of cu m u l a tiv e release), release fro m in itial su rface wash -o ff is add e d to release

est i m a t e from di ff usi o n - co nt r o l l e d phe n o m e na. A n es tim at e of th e cu m u lativ e m a ss release can the n be
obt ai ne d usi ng:

2 1        

⋅

⋅ ⋅ ⋅ + ⋅ = − π t D V S C 2 S M M obs 0 off wash area t mass (Eq u at i o n 8 )

whe r e, is the m a ss of constituent rel eased (surface a r ea basis) fr om surface wash-off [m g/ m off wash area M − 2 ].

Wh en d e p l etion o f th e C O PC is an ticip ated to o ccur over t h e release i n terval, three

- dim e nsional a n alysis
usi n g fi ni t e b o d y m odel s m a y be re qui re d t o est i m a t e cu m u lat i v e rel ease. Anal y t i cal sol u t i ons m a y be f o u n d
for d i fferen t g e o m etries in m a ss tran spo r t literatu re (C rank , 1 975 ) or sim p lifyin g assu m p tio n s m a y b e appl i e d t o val i dat e t h e ab o v e 1- D a p pr oach ( K os so n et al. , 19 9 6 )

. Al t e r n at el y , num eri cal m e t hods m a y be

use dt o sol v e t h e Fi c k i a n di f f u si o n e q uat i o n i n t h ree di m e n s i ons (B a r na , 1 9 9 4 )

. The a b ove estimates represe n t a conservative approac h for m o st m a ss transfer-controlled release
scenari o s where significant e x ternal stres s es are not pre s ent. A ze ro s u rface concent r ation assum e s a

m a xim u m grad i e nt , o r dri v i n g f o rce, f o r

m a ss t r an sp ort (i n f i n i t e bat h ass u m p ti on) . I n t h e case of sl o w wat e r flow past the s u rface or sm all liqui d-to-s urfa ce area ratios, accum u lation of the COPC concent r ation in t h e
leachate re duc es the c o ncent r ation gr a d ient and lim its leac hate conce n trat ion t o the m a ss of COPC in

eq u ilibriu m with th e so lid ph ase. Th us, t h e up p e r bo und(or m a x i m u m co n cen tration ) fo r mass tran sferco n t ro lled release shou ld b e esti m a tedu s ing release es tim a t es ob tain edfrom eq u ilib riu m assu m p tio n s (e.g ., Tier 2 testin g in co nju n c ti o n with p e rco l ation co n t ro lled rel ease).

26Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

Other modeling c o nsid erations

M a ss t r ans p ort m odel i ng a p pr oache s ( G a rra b r ant s , 2 0 01; Ga rra bra n t s et al. , 20 01 ; San c h e z et al. , 2 001 a; Tiru ta-Bar n a et al. , 20 01 ) a r e un de r d e vel o pm ent t o addr ess en vi r o nm ent a l con d i t i ons t h at are m o re
lik ely to b e en co un tered i n th e field su ch as in term it t e nt wet t i ng un de r vari ed e nvi ro nm ent a l con d i t i ons ( i .e.,
relativ e hu m i d i ty an dC O 2 co nten t). Ad d itional m o d e ling also h a s b e en d one to relate co lum n test resu lts to
field leachi n g through a p plication of ge oc he mical speciation (Di j kst r a

et al. , 200 1) . Th ese m o d e ls can

p r ov id e m o re accu rate release esti m a tes, b u t typ i cally req u i re add itio n a l i n fo rm atio n (exp erim en tal an d
fi el d) a n d great er e xpe rt i s e f o r

use
. T h e si m p l e m odel i ng a p pr oac h pr ovi de d here i s i n t e nd ed t o be a

co nserv a tiv e, first-ord e r app r o x i m a tio n th at will resu lt i n ov erestim atio n o f actu a l release fo r m o st cases.



### EXAMP L E APPLICATIONS OF THE FRAMEWORK

Im port a nt pot e n t i a l appl i cat i o ns of t h e l eac hi ng f r am ewor k defi ned he re i n cl ude (i ) t h e

com p arative as sessm ent of wa ste treatm e nt proces ses, s u c h as f o r

det e rm i n at i ons of eq ui v a l e nt t r eat m e nt

u n d e r RCRA, (ii) esti m a tin g en v i ron m en tal i m p acts fro m u tilizatio n o f seco nd ary m a teria l s in co n s t r u c ti o n applications, or (iii) estim atin g releases from large s cale wa ste m onofills. For these cases , Tier 2B a n d T i er
3 B testin g is reco mmen d e d for in itial ev alu a t i o n
. An ex am p l e o f th is ap p l i catio n is p r ov i d ed in t h e

accom p anying pape r (Sa n chez et al. , 2 0 0 2 )

. S ubs eq ue nt l y , Ti er 2 A t e st i n g c a n be use d t o e s t abl i s h

co nsisten c y b e t w een th e m a terials in itiall y testedand o t h e r si milar m a terials

.



### ECONOMIC CONSIDERATIONS

Th e m o re ex ten s iv e testin g reco mmen d e d in th e p r op o s ed fram ewo r k will o b v i ou sly in crease
in itial testin g co sts. Ho wev e r, th ese i n itial co sts sho u l db e offset b y sev e ral factors. First, d e tailed
characte r ization of a m a terial is only necessa ry initially to define its c h arac teristic leaching properties, a n d

o n l y for m a teri als th at are prod u c edi n relativ ely larg e qu an tities. Sub s equ e n tly, m u ch l e ss testin g is need ed

to v e rify th at new sam p les con f o r m to th e prev iou s ly estab l ish e d prop erties. Secon d , co st sav i n g s sh ou l d b e
real i zed t h r o u g h t h e f r am ewor k by ena b l i n g a l t e rnat i v e m a nagem e nt st rat e gi es t h at a r e n o t po ssi bl e un de r
th e curren t rig i d system . Treatmen t p r o cesses ev alu a ted un der th is syste m will b e b e tter t a rg eted to reducin g leaching under field sce n a r ios

. Reduce d treat ment costs m a y be ac hieve di n m a ny cases (howe v er,

27Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

treatm e nt costs m a y increase i n cases whe r e t r eatm e nt p r o c esses were on ly effectiv e at m e etin g TCLP, bu t

were ineffective at re duci n g leaching in the fi eld to le vels c o nsistent with risk-base d e n dpoints). In addition, the potential for e nvironm ental dam a ge and future liability will be reduce d because of t h e closer
rel a t i ons hi p be t w een t e st i n g a n d fi el d pe rf or

m a nce. C o st s f o r

Ti er 1 a n d T i er 2 A t e st i n g s h o u l d be o f t

h e

sam e order

- o f

- m agni t ude as c u r r ent TC LP t e st i ng. R e d u ct i o ns i n c o st s are ant i c i p at ed as t h e m e t hods
b eco m e co mmercializedand d a ta in terpretatio n is au t o m a te d

.



### CONCL US IONS

The proposed fram ework pr es ents a n a p proa ch to eval uate t h e leachi n g pot ential of waste s over a
range of val u es for pa ram e ters that ha ve a signif icant im pact on c o nstituent leaching (e .g., pH, LS, a n d
waste form ) and c o nsideri n g the m a nagem e nt scenari o
. Th is app r o a ch p r esen ts th e po ten t i a l to estim a t e leaching m u ch m o re accuratel y (tha n m a ny currently used leach tests), rel a tive to field le aching, when
conditions for l each test data a r e m a tched wit h fi eld c o nditions. The greater accuracy of t h e proposed approach m a kes it a use f ul tool fo r ex am in in g w a ste an d assessin g th e envir o n m en tal so un dn ess of a r a ng e
of

wast e m a nagem e nt opt i o ns as w e l l as f o r assessi n g t h e e ffect i v e n ess o f pr o pose d wast e t r eat m e nt

m e thods . In a d dition, the propose d fram ework provides flexibility to the end user to select the e x tent of
testin g b a sed on th e lev e l o f in fo rm atio n need ed an d read ily p e rm its th e in corp oratio n of n e w testin g

m e t hods an d re l ease m odel s as t h ey are de ve l ope d fo r s p eci fi c ap pl i cat i ons . A p pr op ri at el y use d i n wast e
regu lato ry prog ram s , th is ap pro a ch cou l dm a k e th ose p r o g r am s subst a nt i a l l y m o re cost

- e ffect i v e an d

p r o t ectiv e o f the env i ro n m en t. Th e flex i b ility of th e propo sedap pro ach allo ws fo r d e v e l o p m en t o f t

h e
fram e wo rk t o p r ov id e a great er d e gree o f tailo ring t o site co nd itio ns, t o acco un t for th e effects of o t h e r
waste leachi n g pa ram e ters critical to a pa rticular site. Relia nce on a tiere d approach to testing ca n also make this approac h m o re econom i cal for sm aller waste vol um es an d t h e r ef o r e m o re br oadl y f easi b l e
.

ACKNOWLE DGE M ENT AND DISCL A IMER

Prim ary support fo r this resea r ch was provi ded by the USE P A Northe ast Hazardous Substances Resea r ch
Cen t er an d th e U S EPA Of f i ce of So lid W a st e. Lim i ted supp or t also w a s pr ov id ed b y ( i ) Th e C o nsor tium f

o r
R i sk E v al uat i o n wi t h St a k eh o l der In v o l v em ent (C R E S P ) t h r o u g h U.S

. Dep a rt m e nt of E n e r gy gra n t s DE

FG2 6

- 00N T 40 938 an d DE-FG0 2- 00 ER 630 22 .A0 0 0 and ( ii) EU D G Resear ch fun d e d p r oj ects. Th e au tho r s

28Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

grat ef ul l y ack n o wl e dge t h e t h ou g h t f ul fee d b ack fr om M r . Gre g Hel m s (USEP A ), a n d Dr. C h a r l e s W. Powers (In s titute for Resp on si b l e Man a g e m e n t ) du ring t h e d e v e l o p m en t of th is m a n u s crip t andt h e

t echni cal s u p p o rt of M s
. Tere sa K o ss on d u r i n g t h e de vel o p m ent of t h e t e s t m e t hods . T h e aut h o r s al s o grat ef ul l y ack n o wl e dge t h e t h ou g h t f ul com m e nt s a n d fee db ack of t h e a n on ym ous re vi ewe r s a n d t h e
assistan ce o f t

h e Ed itor , Dr

. D. Gr asso , lead au tho r of th e USEPA Scien ce A d v i sor y B o ard Rev i ew ( 1999 )
for wh ich th is p a p e r is prim ar ily in respon se. Th e v i ewpo in t s exp r essed in t h is p a p e r are so lely th e
respon sib ility o f th e au tho r s an d do no t n e cessarily reflect th e v i ew o r end o rsem en t o f th e USEPA.

29Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

REFERE NC ES

ANS ( 1 9 8 6 )

. A N S 1 6

. 1

. Am erican National Standa rd Measurem ent of the Leacha b ility of Solidi f ied LowLevel Radi oact ive W a stes by a Short-Term Procedure

. La Gra n ge Pa rk, IL, Am erican Nuclear Society.
B a ker, P. G. an d P

. L. B i sh op ( 1 9 9 7 )

. “P redi ct i on o f m e tal le ach ing rates fro m so lid ified / stab ilizedwastes using t h e s h ri nking unreacted core leachi n g proce d u r e
. ” J o u r n a l o f H a z a rdous Mate rials 52 (2 -3) : 311 -33 3

. Bar n a, R. ( 1994 ). Etud e d e la d i f f u s i o n d e s po llu an ts d a n s l e s d é ch ets so lid if iés p a r lian t s h ydr au liq u e s. Lyo n , Fran ce, In stitu t National d e s Scien ces Ap p liqu ées d e Lyon , 21 0 pp

. Batchelor, B. (1990). “Leac h m odels: Theory an d app licatio n
. ” J o u r n a l of H azar dou s Mater i als 24 (2 -3 ) : 2 55- 266

. Batchelor, B. (1992). “ A num erical leaching m odel for solidified/stabilized wastes.” W a te r Scie nce a n d Tech nol ogy 26 (1 -2 ): 10 7- 1 1 5

. B a t c hel o r, B

. ( 1 9 9 8 )

. “Leac h m odel s fo r c o n t am i n ant s im m obi l i zed by pH -de p e nde nt m e chani s m s .” En vi ro nm ent a l Sci e nce a n d T echn o l o gy 32 : 17 2 1

- 1 72 6.
Batch e lo r, B. an d K. Wu (19 9 3 ) . Effects o f eq u ilib riu m ch emistry o n leach i ng o f con t amin an ts fro m stab ilized /so lidifiedwastes. C h em istry an d micro s tru c t u re o f so lid i f iedwaste form s . R.D. Sp en ce. Bato n Rouge, LA, Le wis P ublis hers 2 43- 260

. B u i l d i n g M a t e r i al s Decree ( 1 9 9 5 )

. St aat sbl a d va n het K o ni n k ri jk

de r Nede r l ande n 56 7. Cheng, K.Y. a n d P.L. Bi shop (1990). “De v e l oping a ki netic l eaching m o del for so lidifie d/stabilized hazardous wa s t e s
. ” J o urna l of Hazardous Materials 24 : 213 -2 24

. Cr ank , J. ( 1975 )

. T h e Math ematics o f D i f f usio n
. Lo ndo n, U K , O x f o rdUn iv er sity Pr ess. Crannell, B.S

. , T.T. Eighm y , J.E. Kr zanows k i, J

. D. E u s d en, Jr ., E.L. D h a w a n d C.A

. F r a n cis ( 2 000). “Heav y m e tal stab ilizatio n in m u n i cip a l so lid waste co m b u s tio n bo tto m as h u s ing so lub l e ph o s ph ate.” Wast e M a na ge m e nt 20 : 13 5-14 8. de Groot, G.J. (1993). Detailed de scri ption of the leaching beha viour of s econda r y const r uction product s
. ECN

- 93 -0 85 ( i n D u tch )

. de Groot, G.J. and H.A. van der Sl oot (1992). Dete rm inatio n of leachin g c h aracteristics of waste m a teria l s lead in g to env i ron m en tal p r o d u c t certification

. So lid i f icatio n an d Stab ilizatio n o f Hazardo u s , Rad i o acti v e, an d Mix e d W a stes, 2nd V o l u me, A S TM STP 112 3 . T.M. Gillia m an dC.C. W iles. Ph ilad e lph i a, PA, Am erican Soci ety for Testing and Materials 1 49- 170

. D ijk str a , J.J., H

. A

. v a n d e r Slo o t an d R.N

. J. Co m a n s (2 001) . “Pro cess i d en tif icatio n and m o d e l devel opm ent o f c ont am i n ant t r ans p ort i n M S WI b o t t o m ash.” W a st e M a na gem e nt : (in pre ss).
Ei ghm y , T.T. a n d W.H

. C h es ner ( 2 0 0 1 )

. F r a m ewor k fo r e v aluating use of recycled m a terials in the highway envi ro nm ent. F H WA-R D- 0 0

- 1 4 0

. M c Lean , VA , F H WA

. ENV 1 2 9 2 0 ( 1 99 6 ) . M e t h o d o l ogy gui del i n e fo r t h e det e rm inat i o n o f t

h e l e achi n g beha vi o u r o f wast e un der sp ecif i ed cond i tio n s , CEN / TC 29 2 W G 6

. En vi ro nm ent C a nada ( 1 99 0)

. C o m p endi um of W a st e Leac hi n g Test s
. EP S 3/ HA/ 7. Ot t a wa, C a na da, En vi ro nm ent C a nada

. En vi ro nm ent C a nada an d Al b e rt a En vi r o nm ent a l C e nt er ( 1 98 6 ) . Te st m e tho d s f o r sol i d i f i e d wa st e charact e r i zat i on, Aci d Ne ut ra l i zat i on C a paci t y , M e t h o d #7

. Ont a ri o, C a na d a , E nvi r o nm ent C a nada an d Al be rt a En vi r o nm ent a l C e nt er.

30Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

Frazer, J.L. a n d K.R. Lum (1983). “ A vailabilit y of elem ents of e nvi ronm e n tal i m porta nc e in inci nerate d sl ud ge as h.” E nvi ro nm ent a l Sci e nce a n d Tec h n o l o gy 17 (1 ) : 1- 9.
Gar r ab ra nt s, A

. C

. ( 1 99 8 ) . De vel o pm ent and ap pl i cat i on of fu n d am ent a l l e achi n g pr o p ert y pr ot oc ol s fo r evaluating i n organic release fr om wast es an d soi l s
. C h em i c al and B i oc hem i cal En gi nee r i n g . Ne w Brunswic k, NJ , Rut g ers , T h e State Uni v ersit y of Ne w Je rse y , 21 6 pp

. Garrabran t s, A.C. (20 01). Assessm en t o f inorg a n i c co n s tituen t release from a Po rtlan d ce m e n t -b ased m a trix as a resu lt o f i n termitten t wetti n g , d r ying and carbon atio n. Dep t . C h em ica l an d Bio c h e m i c a l Eng i n e ering

. New Bruns wic k , NJ, Rut g ers , The State Uni v ersity of Ne w Jersey, 396 p p
. Garrabran t s, A.C. an d D.S. Ko sso n (2 000 ). “Use o f a ch elatin g ag en t to d e termin e th e m e tal av ailab ility for leaching from soils and waste s .” Waste Managem e nt and Research 20 (2 -3 ): 1 5 5

- 1 6 5

. Gar r ab ra nt s, A

. C ., F

. S a nc hez , C

. Ger v ai s, P. M o sz ko w i cz an d D. K o sson (2 001 ). “T he e f fect of st ora g e in
an in ert atm o sp h e re on th e release o f ino r g a n i c con s titu en ts du ri n g in term itten t wettin g of a cem en t-b a sed
m a t e r i a l

. ” J o u r n a l o f Hazardous Materials : (accepted).
Go um ans, J.J

. J

. M ., H. A. va n der Sl o o t a n d T.G

. A a l b er s, Eds. ( 1 99 1)

. W a st e M a t e ri al s i n C onst r uct i o n
. St

udi es i n E n vi ro nm ent a l Sci e nce, V o l 4 8

. A m st erdam , El sevi er Sci e nce Pu bl i s her s
. Hi nse n vel d , M

. ( 1 99 2)

. A s h ri nki ng co re m odel as a f

u n d a m ent a l rep r ese n t a t i on o f l eac hi n g m echani s m s i n ce m e n t stab ilized waste. Cin c i n n a ti, OH, Un iv ersity of Cin c in n a ti.
Hi nse n vel d , M

. an d P.L

. B i sh op ( 1 99 6)

. Use o f t h e sh ri n k i n g c o re/ e xp os ur e m odel t o des c ri be t h e leachability from ce ment stabilized wa s t e s
. S t ab i l i z a t i o n a n d S o l i d i f i c a t i o n of Haza rdous, Ra di oactive, and M i xed Wast es, ASTM STP 1 2 4 0 . T.M. Gillia m an d C

. C. W iles, Am eric an So ciety fo r Testin g and Mater i als. 3rd

. Hjel m a r, O

. ( 1 99 0 ) . “Leac hat e fr om l a nd di s pos al o f c o al fl y ash.” W a st e M a nagem e nt and R e searc h 8 : 4 29- 449

. Hjel m a r, O ., H

. A. va n de r Sl o o t , D. G u y o n n e t , R

. P.J

. J. R i et ra, A. B r unan d D. Hal l ( 2 00 1) . D e vel opm ent o f acceptance criteria for landfilling of waste. An a p proach based on im pact m odelling and scenari o calcu latio n s
. P r o ceed i ng s of t h e 8 t h Waste Man a g e m e n t an d Lan d fill Sym p o s iu m . T.H. Christe n sen, R

. Co ssu and R. Steg m a n n
. 3: 711 -72 1

. IA WG ( 1 99 7 )

. M uni ci pal Sol i d Wast e I n ci n e rat o r R e si d u es
. Am st erdam , El sevi er Sci e nce Pu bl i s he rs.
Joh n s o n, C

. A. , M

. Kä p p el i , S

. B r an de nbe r g e r , A. Ul ri c h a n d W. B a um ann( 1 9 9 9 ). “Hy d r o l o gi cal an d geoc hem i cal factors a ffecti n g leachate com position in m uni cipal solid waste incinerat o r bottom ash. Pa rt II: The ge ochem i stry of leachate from landfill Losdo rf, Switzerland.” Journal of Contaminant Hydrol ogy 40 : 2 39- 259

. Jo hn son , C.A., G.A. Richn e r, T. Vitv ar, N. Sc h ittli an d M. Eb erh a rd (1 998 ). “Hyd ro log i cal an d geoc hem i cal factors a ffecti n g leachate com position in m uni cipal solid waste incinerat o r bottom ash. Pa rt I: Th e h ydro l o g y of land fill Lo sd orf, Switzerlan d

. ” J o u r n a l of Con t amin an t Hyd r o l o g y 33 : 3 61- 376

. Kei zer, M

. G

. a n d W.H

. vanR i em sdi j k (1 9 9 8 ) . EC OS AT. D e part m e nt of E nvi ro nm ent a l Sci e nce, Sub d e p a rtm e n t So il Scien ce an d Plan t Nu tritio n , W a g e n i ngen Agricu ltural Un iv ersity, The Neth erland s.
Khe b ohi a n , C

. and C

. F

. B a ue r ( 1 9 8 7 ). “Acc uracy of selective extraction procedures for metal speciation in
m o d e l aq u a tic sed i m e n t s
. ” A n alytical Ch e m istry 59 : 14 17-1 423

. Kinn ibu r gh , D.G., W.H. v a n Rie m sd ij k , L.K. Ko pp al, M

. Bo rk ov ec, M.F. Ben e d e tti and M.J. Av en a (199 9). “Io n b i n d i n g to n a tural o r g a n i c m a t t e r : co m p etitio n , h e tero g e n e ity, sto i ch io m e try an d therm odynam i c consistenc y.” C o l l o i d s and Surfaces A- 1 8 1 : 14 7-1 6 6

.

31Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

Kos s o n , D

. S. a n d H

. A

. vande r Sl oot (1 9 9 7 )

. Int e grat i o n of t e st i ng pr ot oc ol s f o r eval uat i o n of co nt am i n ant release fro m mo no lith ic an d granu l ar wastes

. WASCO N ' 9 7 - Inte rnatio na l C o nfe r ence o nC o nst r uct i o n wi t h Wast e M a t e ri al s, H out ha m , The Net h e r l a nd s, El se vi er Sci e nce P u bl i s hers

. Kos s o n , D

. S. , H. A. va n der S l oot a n d T. T. E i ghm y (19 9 6 ). “Anap p r oac h fo r est i m ati ng of co nt am i n ant release during u tilizatio n andd i spo s al o f m u n i cip a l waste co m b u s tio n resi d u e s
. ” J o u r n a l o f Hazardou s Mater i als 47 : 43 -75

. M e im a, J., A

. vanZ o m e ren a n d R

. N

. J. C o m a ns (1 9 9 9 )

. “T he c o m p l e xat i on of C u wi t h di ssol v e d o r ga ni c carbon in m unicipal solid was t e incinerat o r bottom a s h l e a c h a t e s
. ” E n vironm en tal Science and Tec h nol ogy 33 (9 ) : 1 424 -142 9.
Meim a, J.A. a n d R.N.J

. Com a ns (1998). “Applica tion of s u rface c o m p lexation/precipitation m odeling to contam inant leaching from weat here d MSWI bottom ash.” Enviro nm ental Science a n d T echnology 32 : 6 83- 693

. Meim a, J.A. a n d R.N.J

. Com a ns (1999). “The l eaching of trace elem ents from m unicipal solid waste i n ci nerat o r b o t t o m ash at di f f e r ent st a g es of weat he ri n g .” A ppl i e d Ge oc he m i st ry 14 : 159- 171

. Moszkowicz, P., R. Barna, F. Sa nchez , H.R

. Bae a n d J. M é h u ( 1 9 9 7 )

. M odels for leaching of porous mater i als . W A SC ON ' 97 - Int e rnat i o nal C o n f ere n ce on C onstru c tion with Waste Materials, Hou t h a m St. Gerlac h, T h e Nethe r lands, E l sevier.
M o szk o w i cz, P., J

. P o usi n an d F

. Sa nc hez ( 1 9 9 6 )

. “ D i f f u si onan d di ss ol ut i on i n a react i v e p o r o us m e di um : m a t h em at i c al m odel l i ng an d num eri cal simu l a t i ons .” Jo urn a l of C o m p u t atio n a l an d App lied Math em atics 66 : 37 7-3 8 9

. M o szk o w i cz, P., F. Sanc hez, R

. B a r n a a n d J

. M é h u (1 9 9 8 )

. “Pol l u t a nt s l e a c hi n g beha vi ou r f r o m sol i d i f i e d wast es: A sel e ct i on of ada p t e d vari ous m odel s
. ” T a l a nt a 46 : 375 -38 3

. NEN 7341 (1994). Leachi n g ch aracte r istics of soil, c o nstruction m a te rials and wastes - L eaching tests - Determ ination of the a v ailability of inorga ni c constituents for leachin g from construction m a terials and waste m a terials. Del f t, T h e Netherlands, NNI (Dutch Standardization Insti t ute). NEN 7343 (1995). Leachi n g ch aracte r istics of soil, c o nstruction m a te rials and wastes - L eaching tests - Det e rm i n at i on of t h e l eac hi n g o f i n or ga ni c c o m pone nt s f r o m granul ar m a teri al s wi t h t h e col u m n t e st . D e l f t , Th e Neth erland s, NNI (Du t ch Stan d a rd izatio n In stitu te). NEN 7345 (1994). Leachi n g ch aracte r istics of soil, c o nstruction m a te rials and wastes - L eaching tests - Determ ination of the release of inorga nic constituents from construction m a terials, m onol ithic wastes a n d stab ilizedwastes. Delft, Th e Neth erland s, NNI (Du t ch Stand a rd izatio n In stitu te). NEN 7347 (1997). Leachi n g ch aracte r istics of soil, c o nstruction m a te rials and wastes - L eaching tests - Com p acted gra nula r leach test of inorga nic c onstitue n ts. De lft, The Net h erlands , NNI (Dutch Stan d a rd izatio n In stitu te).
N i r e l, P.M.V

. an d F.M.M

. M o r e l ( 199 0)

. “Pitf a lls o f sequ en tial ex tractions.” Water Research 24 (8) : 105 5- 1 056

. NVN 7438 (2000). Leach i n g characte r istics of soil, stony building m a teria l s and wastes - Characterization tests - Determ ination of t h e re duci n g cha r act ers a n d redu cing cap acity. Del f t, Th e Neth erlan d s, NEN. prE N 14405 (2001). C h aracte r isation of was t e: Leaching behavi or tests - Up-fl ow pe rc olati on test, CE N/TC 29 2 WG 6

. prEN14429 (2001). C h ar acte r isation of waste: Leaching behavi or tests - pH de pe nde nc e test with i n itial aci d/ base a d di t i on, C E N/ TC 2 9 2 WG 6.

32Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

San c h ez, F. (19 96). Et u d e d e la lix iv iatio n de milie u x po reu x con t en an t des esp èces so lub l es: App licati o n au cas d e s d é ch ets so lid ifiés p a r lian t s h y d r au liq u e s. Ly o n , Fran ce, In stitu t Nation a l d e s Scien ces Ap pl i q uées de Ly on , 26 9 p p
. San c h ez, F., A.C. Garrab r an ts an d D. S. Ko sso n(20 0 1 a ). “Effects o f in termit ten t wettin g on co n c en trati o n pr ofi l e s a n d rel ease f r om a cem ent

- base d wa st e m a t r i x
. ” E n vi r onm ent a l Engi neeri n g Sci e nce : (sub m i t t e d ).
Sanc hez, F., I

. W. M a ss ry , T. T. Ei g h m y and D. S. K o ss on ( 2 0 0 1 b )

. “M ul t i -re gi m e t r ansp ort m odel f o r leaching of het e roge neous porous m a terials.” W a ste Ma nage m e nt : (su b m i tted).
Sanc hez, F., C. Mattus, M. Morris a n d D.S. Kos s on (2002). “Us e of a ne w leachi n g test fram e work for ev alu a ting altern ativ e treatm e n t pro cesses for m e rcury c ont am i n at ed m i xed wast e
. ” E n vi ro nm ent a l En gi neeri n g Sc i e nce : (su b m itt ed ).
Sch r eu rs, J.P

. G.M

. , H

. A

. va n der Sl o o t an d C.F. H e nd r i ks ( 200 0) . “V er if i catio n o f labo rato ry-field leach i ng beha vi o r of co al fl y ash a n d M S W I b o t t o m ash as a roa d b a se m a t e ri al .” Wast e M a na ge m e nt 20 (2 -3 ) : 1 93- 20 1. Tessier, A. , P

. G.C. Cam pbell and M. Bisson ( 1 979). “S eq uen tial ex traction p r o c ed ure for th e sp eciation of p a rticu l ate trace m e t a l s
. ” A n alytical Ch e m ist r y 51 (7) : 844 -85 1

. Ti rut a -B a r na , L.R ., R

. B a r n a and P. M o sz k o w i cz ( 2 00 1) . “ M odel i n g of s o l i d / l i qui d/ gas m a ss t r ans f er f o r envi ro nm ent a l eval uat i o n of c e m e nt -base d s o l i d i f i e d w a s t e
. ” E n v i ron m en tal Scien ce an d Techno log y 35 : 1 49- 156

. USEP A ( 1 9 8 6 )

. Haza r d o u s W a st e M a nagem e nt Sy st em : Land Di s p o s al R e st ri ct i ons: Fi na l R u l e , Fe der a l R e gi st er, Part I I , Vol

. 40 C F R Part 2 6 1 et se q. Was h i n gt o n , DC , US E nvi r onm ent a l Pr ot ect i on Age n cy
. USEPA (1 991 ). Leach ab ility Ph en o m en a. EPA-SAB

- EEC-9 2-0 0 3

. W a sh i n g t o n , D.C., USEPA Scien ce Ad vi so ry B o ar d.
USEPA (1 999 ). W a ste Leach a b ility: Th e Need for Rev i ew of Curren t Ag ency Pro cedu r es. EPA-SAB-EECCO M- 99- 002 . W a sh ing t on , D.C., U S EPA Scien ce Adv i sor y Bo ard

.

van de r Sloot, H.A. (1999)

. C h a r a c t e r i z a t i o n o f t h e leaching beha vi our of conc rete m o rtars a n d of cem ent stabilized wa stes with differe n t wa ste loa d in g fo r lo n g -term en vi ronm ental assessm ent . Waste Stabilization and the Environm ent, Lyon, Fra n ce.

van de r Sloot, H.A. (2001). Eu ropean activities on harm onisation of leachi ng/e x traction t e sts and stan d a rd isation in relatio n t o t h e u s e o f alternativ e m a teria l s in con s tru c tion . ICMAT In tern atio n a l Confere n ce on Materials for Adva nced Tec h nologies, Singapore.
EU P r oject SM T4-C T 9 6- 2 0 6 6

. Tec hni cal s u p p o r t t o t h e Net w o r k Ha rm oni zat i on of Leac hi n g / E xt ra ct i o n t e st s. 2 0 0 0

. va n der Sl o o t , H. A., pe rs onal c o m muni cat i on ( 2 0 0 2 )

.

v a n d e r Sloo t, H.A., L. Heasman and P. Quev auv ille r, Ed s. (19 9 7 )

. H a rm o n i zation o f Leach ing / Ex t r actio n Tests . St udi es i n E n vi ro nm ent a l Sci e nce, V o l 7 0

. Am st erdam , El sevi er Sci e nce P u bl i s her s
.

van de r Sloot, H.A. a n d D. Hoede (1 997). C o m p arison of pH static leach t e st with ANC test data. EC N R9 7 -0 02 . Petten , Th e Net h erland s, ECN.

van de r Sl o o t , H. A., D

. Hoe d e an d R

. N.J

. C o m a ns (1 9 9 4 )

. The i n fl ue nce of re duci n g p r ope rt i e s o n l e a c hi n g of

el em ent s fro m wast e m a t e rial s an d c onst r u c t i on m a t e ri al s
. E nvi r o nm ent a l As pect s o f C onst r uct i o n wi t h Waste M a terials . J.J.J.M. Gouman s, H

. A. v a n d e r Sloo t an d T. G. Aalbe r s. Am sterdam , The Nethe r lan d s , Elsevier Science B.V. 48 3- 4 9 0

.

v a n d e r Sloo t, H.A., R.P.J.J. Rietra, R.C. Vro o n , H. Sc ha rf f a n d J. A. Wo e l ders ( 2 0 0 1 a). Sim ilarities in the long-term leaching beha viour of pr e dom inantly inorganic waste, MS WI botto m ash, de gra d ed MSW a n d bioreactor resi due s
. P r o c e e d i ngs of t h e 8th Waste Mana ge ment and La ndfill Sym posium . T.H. Christense n, R

. C o ss u a n d R

. St egm a nn. 1: 199 -2 08

.

33Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

van de r Sl o o t , H. A., A

. van Z o m e ren, R

. P

. J. J. R i et ra, D. H o ede an d H. Sc har f f ( 2 0 0 1 b )

. Int e grat i o n of l abscale testin g , lysi m e ter stu d i es and p ilo t scal e m o n ito ring of a p r edo m in an tly in o r g a n i c waste lan d fill to reach sustainable landfill conditions

. Proceedings of the 8t h Waste Ma na ge ment and La ndfill Sym posium

. T.H. Christen sen , R

. Cossu an d R. Steg m a n n
. 1: 25 5- 2 6 4

.

34Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

Tab l e 1

. Sp eci ficatio n s for th e b a se case an d su gg estedaltern ativ e co nd ition s for equ ilib riu m ex tractio n s
. M a x i mu m P a r t i c l e S i z e [ m m ] Base case Suggeste d alternates 2 0. 3 5 M i nim u m sam p l e si ze [ g ] 40 20 80 M i nim u m cont act t i m e [hr] 48 18 16 8 ( 7 day s ) C ont ai ne r si ze [m L] 25 0 50 0 10 0 0

35Environmental EngineeringScience, In-press, 2002.Table 2.Comparisonofrecommendedleachingprotocols andapplications.TierTestNamePurposeMethodologyOutputApplication1AV001.1Todeterminethepotentially extractablecontent of constituentsunder environmentalconditions.Parallel extractionsat pH4and8inDIwater;Liquid-tosolid(LS) ratioof 100mL/g;contacttime dependentonparticle size.Availability at pH4Availability at pH8Screening:conservative release estimate.Characterization: realistic source termformodeling mass transport-controlledrelease.1AV002.1Todeterminethepotentially extractablecontent of constituentsunder environmentalconditions.Single extractionusing50mM EDTA; LS ratio of100mL/g; contact timedependent onparticlesizeAvailability inEDTAScreening:conservative release estimate.Characterization: realistic source termformodeling mass transport-controlledrelease.2SR002.1Toobtainsolubility andrelease dataasafunctionof leachatepHMultiple parallel extractionsusingDIwaterandHNO3orKOH; LS ratio of10mL/g;contacttime dependentonparticle size.Material-specificacid/base titrationcurve.Solubility andrelease asa functionofpHCharacterization:detailedbehaviorofCOPCasa functionofpH.Compliance:abbreviatedprotocoltoindicate consistency withpreviouscharacterization.2SR003.1To estimate porewaterconditions byobtainingsolubility andreleasedataas afunctionofLSratio.Multiple parallel extractionsusingDI water; LS ratiosof0.5to 10mL/g; contact timedependent onparticlesize.Solubility andrelease asa functionofLSratio.Characterization:detailedbehaviorofCOPCasa functionofLSratio.Compliance:abbreviatedprotocoltoindicate consistency withpreviouscharacterization.3MT001.1Todeterminemasstransfer parameters.To estimate rate ofrelease undercontinuously saturatedconditions.Semi-dynamic tankleachingofmonolithicmaterial;Liquid-to-surface-area ratioof10[mL/cm2]Observed constituentdiffusivity.Rate and cumulativerelease of constituentrelease undercontinuously saturatedconditions.Characterization: detailed leachingmechanismsandrate ofrelease undermass-controlled leaching scenario.Compliance: abbreviatedto indicateconsistency withpreviouscharacterization.3MT002.1Todeterminemasstransfer parameters.To estimate rate ofrelease undercontinuously saturatedconditions.Semi-dynamic tankleachingof compactedgranularmaterial; Liquid-to-surfacearearatio of 10[mL/cm2]Observed constituentdiffusivity.Rate and cumulativerelease of constituentrelease undercontinuously saturatedconditions.Characterization: detailed leachingmechanismsandrate ofrelease undermass-controlled leaching scenario.Compliance: abbreviatedto indicateconsistency withpreviouscharacterization.36Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

MA T E R I AL WA STE, SOIL OR PRO D U C T

MAN A G E MENT SC ENA R IO

y S peci f i c di sposal or

ut i l i z at io n sc e nario

y D e fa ult cases

SCR EEN ING TI

E

R

1 Ti er 1

TI

E

R

2

TI

E

R

3 MASS TR AN SFE R R A TE

Compl i ance

T i er 3A

L EVE L A LEVE L B L EVEL C EQ U I LI B R I U M Com p li ance

T i er 2A EQ U I LI BR I U M C h a r ac ter i z a ti on Ti er 2B

MASS TR ANS F ER RA TE C h a r ac ter i z a ti on Ti er 3B EQ UIL I BR IUM Qual it y Con t rol (Mat eria l speci f ic) Ti er 2 C

MASS TR ANSF ER RAT E

Qual it y Con t rol (Mat eria l speci f ic) Ti er 3 C Ran d o m comp lia nce t e s t ing Defau l t S cen ari o Sp e c i f ic or Defau l t (see text) S cen ari o

Ran d o m co mplia nce t e s t in g

Figure 1. Alternative Fram ew ork for e v aluat i on of leachi n g

37Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

2 4 6 8 10 12 14

- 2 0 246 8 1 0 A c i d A d de d [m e q / g dry ]pH Ma t r i x A

Ma t r i x B

a) KO H HNO 3 0.00001 0

. 0001

0.001

0.01

0.1

1 10 100 1000

4 6 8 10 12 L eac h a t e

p HConc[mg/L]

C a t i oni c A m phot e r i c O xya ni oni c Hi g hl y So l u b l e

b)

10 11 12 13 14

0 2 468 1 0 LS

R a t i o [ m L/

g d ry ]pH Ma t r i x A Ma t r i x B

c) 0 200 400 600 800 1,000

0 2 468 1 0 LS

R a t i o [ m L/

g d ry ]Conc[mg/L]

C o n s ti tu e n t 1 C o n s ti tu e n t 2

d)

Fig u re 2

. Con c ep tu al d a ta o b t ain e du s i n g equ ilib riu m -b as ed testing p r o t oco l s: a) titration cu rv e (SR 0 02 .1 ), b ) con s titu en t release as a functio n o f pH (SR0 02 .1 ), c) p H as a fun c tion of LS ratio (SR 0 0 3 .1), and d )
co nstitu en t co ncen tration as a fun c tion o f LS ratio (SR003 .1).

DRAFT – do not cite, qu ote or distribu te Fr am ew o r k

f

i nal ( i n - pr ess).doc 3 / 27 /02 3 8Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

0

. 0001

0.01 1 100 10000

2 4 6 8 10 12 14 L eac h a t e

p HLeadRelease[mg/kg]

R e l e as e f ( p H ) Av ai l ( p H4 ) To t a l R l f i a) 0.001 0.01

0.1

1 10 100

8 1 0 1 2 Le ac h a t e

p HLeadConc[mg/L]

1 4 S R

002. 1 C onc f ( p H ) S R

003. 1 C onc f ( L S )

b)
Fig u re 3

. Act u al d a ta ob tain ed u s ing equ ilib riu m -b ased testin g pro t o c o l s fro m a cem en ti t i o u s syn t h e tic waste: a) lead release as a functio n o f pH com p ared to lead av ailab ility andto tal leadco nten t and b )
com p ari s ono f SR 00 2. 1 an d S R 00 3. 1 c o ncen t r at i on dat a
.

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f

i nal ( i n - pr ess).doc 3 / 27 /02 3 9Enviro nmental Eng i neering Science , In -p re ss, 20 0 2

.

6.5

7 7.5

8

0 2 0 4 0 6 0 8 Ti m e ( d a y s )LeachatepH

a) 0 0 200 400 600 800 1000

0 2 0 4 0 6 0 8 Ti m e ( d a y s )BaConcentrationμg/L

0 M T 001. 1 d a t a S R

002. 1 d a t a

b)

0 40 80 120 160

0 2 0 4 0 6 0 8 Ti m e ( d a y s )CumulativeBaRelease(mg/m2)

c) 0 0.01 0.1

1

0.1 1 10 1 0 0 Ti m e ( d a y s )BaFlux(mg/m2s)

d) s l ope = - 0. 5

Fi gu re 4. Act u al dat a o b t a i n e d usi n g M T 0 0 1

. 1 pr ot oc ol f r o m a st abi l i zed wast e (va n de r Sl o o t , 19 9 9 ): a) leachate pH as a function of c u m u lative tim e , b) c o m p arison of leachate barium conce n tration (MT001.1)
an d b a riu m so lu b ility as a functio n o f pH (SR0 02 .1 ), c) cum u la tiv e release of b a riu m as a fu n c tion o f
cum u lative time, and d) barium flux as a function of m ean cum u lative time.

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.



### Release s cenario: P e r c olat ion

S eepag e B a s i ns V

S fi e l d p H



### @ Local equil i brium at fie l d pH is rate li m iti ng Scen ar io ch a r acte ris tics

- G r a nu l a r or hi g h ly p e rm e ab le m a t e r i al

- L o w in fi lt rat i o n r a te

- L o w l i quid

- sol i d ra t i o s [mL / g]

Site inf o r m a tion

- I nf il tr a tion rate inf

- F i l l densi t y ρ - F i l l g e o m e t r y H f ill - F i e l d p H

Figure 5. Release scena r io: percolation.

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.



### R e lease sc enario: D i f f

usion

- controlled s cen ario

C sa t

C s ≈ 0 R o adb a s e m a t e ri al



### @ M a s s t r ansport w i thin solid m a trix i s r a t e l i m iti ng Scenario cha r acte r is tic s

- L o w p e r m eabili t y m a te r i al

- H ig h in f i l t

ra tion rate

- H ig h liq u i d

- su rface a r ea ra tios

S i te info r m a tion

- F i l l de n s ity

- F ill ge om e t ry S, V

- F il l por o s i ty

Fi gu re 6. R e l ease scena r i o : di f f usi o n - c ont r o l l e d sce n ari o
.

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f

i nal ( i n - pr ess).doc 3 / 27 /02 4 2