Phytoremediation

Phytoremediation

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CONTENTS

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€9

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PREFACE

SECTION I INTRODl'C Rationale for Use of Ph

For ()rdering and customer ,en ice. call I -ROO-CALL- WILEY,

Blin [J ElisII'Y. Ph. f) Library of Congress Cataloging-ill-Publicatioll Data: Raskin, 11) uptake sugge~h that Cd is accuI11ulated intraeellularly \ ill the same transport meehunism (Salt el at.. 19(7). Phytnchelatins play an important role in the accuillulation and cletmification of Cd in the \[[cllok (Salt et al.. 19l)5. 1997l. Phytochelatins appear to he the primal': metal-hinding polypeptides of planh that arc constiluti\t'ly exprt'ssd and pia) a central role ill accull1ulating and/or detoxifying e:orption. \\hich ma~ be t\\ 0 major processes imolwd in n.':l11o\ul of metals. tend to form insnluhk compouncb, Plant appoplast is influenced by the properties of the ~'el1 \\all and middle lamella and is found to he negati\ely charged, Therefore. l'atiolls from the e\ternal solutinn can accumulate in a nOl1ll1etaholic step in the free space. \\ here anion~ are "repelled." Plant specics as well as root segment age differ c(lnsiderahl~ in ~'ation-excl1ange capacit~ (numher of cation-exchange sites) located in ccll \\alls, This aspect should he con"idered \\hen sekcting :1 plant for phytotiltration, \loreo\er. there is little relationship bet\\'eel1cation adsorption and cation absorption, and some of the ~'ations reillain attached to form an ion-e\change-Iike surface, The de\elopment of anion-exL'hange reactions (that charactcrized hy short uptake time periods. a rate-limiting step, anJ an apparent sekcthity of one ion in preference to another) is one important component of ph~ tnfiltration, Although the formulation of ,uch a real,tion \\ould be similar to thai employed for kinetic analy"is in a carrier theory. it has a ditTu,ion-limited step rather than carrier turno\er. Remmal of U from ,olmion i~ a~sociated \\ith a combination of such physical and chemical pro~'es,es a, chelation. ion eXl'hange. and chemical precipitation, Positi\el: charged U ions may interact "ith carboxyl groups of polygalacturonic acid and other negati\ely charged hinding ,ites \\ithin plant cell \\ ails (Dushenkm et aL. Illl)7b l. It \\as found that lead is precipitated from solution by suntlO\\er roOh mostly as lead phosphate (Dus!1el1ko\' et al.. IlY95 I. :'lilToscopic analysi, of corn roots. exposed to soluhle Ph slHm ell the prest'nce of ~imi lar electwn-dense deposits in' ide and outside cells (.vlalone et al.. 197·{j, Analysis of B, ./III1Ce1l roots expo,ed to Ph "hcl\\ecl the formation of precipitate' that contained suhstantial a11101l11l\ of Ph carbon;ltes in the cdl walls (Raskin et al.. 1l)971. Lead can also hind to e\changeable anionic binding

sik's in the ct'11 \\

-

800

0 t: 0

400

:;::;

200

t:

0

G>

t: 0 U

1000 750 500 250 ,,,"-0""'"'''''0'''''''

0 nHlh

"rdifl'crclll plallh, H)ci!'op()l1ic'a!i:

"

1000

600

(.)

I

Japanese lawngrass

0,

III

f--I--i

Orchardgrass

'0

0

E

-..

1--1--1

Corn

~rl1\\n

pL..lllt:-. \\ L'n...' treated \\ iIIl L't)ntinu{lu"l~ ~h:rllted "olutinn \{ 300 1l1g!l. Ph . . ~!pplicd

dellote S,E,

'\1n

H-I

Tobacco

Lead ac'ClIlllU]alHlI1lll

\\-~

r . .' l..iUl\,,'d

Ph-' \\ Ithll1 the' (ir't hllur of tl ',\ c';" I11Ue'h lc:" l'1fil.'iellt in rem()\'

Creeping bent grass

Figure 7--1

\

~-old "llnllti\\ l'r Ph ,upplil'd a, Phi :\0; 12. \·cniccll bar,

llg/L (Dus!JenKm et al.. 19(5), e reillmal of Cd c+. O·h+, Cu c+, that is. the ratio of metal wI concentration ill the solution

I 0

......0 .........0 ...................

0 I I

10

20

0

I

I

10

20

500 0

Time (hrs) Figure 7·:' Rhiwl·iilralilill "r hca\ \ 111,'(,,(, U'Elg 'L1lln, ,\\ cr pI.1I'1'. HI c!wrulliL"alil gnm 11 pl'lIlh lIl'rc pUI Oil 1,,1' III 1.1--"I11·decp pla'li, jar Ihal c(lllt,1IIlcd ,50 I11L "I' ""1l1illlhHhl., aerated l1ldi,L The lnlcd ·q,11I1lle df lh\..' -.ululi{ll1 \\~h kept l'OIh{dnt b;, adJing dl.?ioni/ed \\ater tn L~)Jlll)L'lh "f

)r the remO\al of radiollllclides ) Indian mustard and bean for al plants were screened for their .onel ncar the Chernob\1 nuclear bioaccumulatioll coefficient for for 'IIlS r in suntlo\\er,huoh cd up to 8 times more I;;CS than tail V\lOPCClintS protells;s L j, ilogrill11 dry weight-a quantity in quarantine in the Chernobyl

.

~

; of 100-250 (Salt et aI., 1907l. Blaslofiltration Ill;}) represent an alternati\c plum-hascd \\arer trcatI1l~11l tcchnology, It takes ad\anwge of the fast increase in surface:\ (Jlllm~ ratio that occurs after germination and e\ploit, the fact thar ,ome germinating seedling, also ah,orh or ad,orh large quantities of to\ic metal ion,. Thi, property make, seedlings perfectl) suitable for \\ater remediation. To produce seedling culture, to be used for blastofiltration. s~cd" water. and air are the only components requircd,

It \\as recentl;. dis(o\ered that \\hen gn1\\n in aerated

fIELD P

\\ ater at the Ashtabula site was plants. Figure 7-H illustrates rhe! Flm\ rate, of O. 15- I .60 Lim i of the rhizofiltration syQell1. T~ concentration from se\eral hUIll discharge Ie\el of 20 pg/L. Wh residence time in the tanks. the operat ion \\as found to be ap concentration~ correlated \\'ith tht l' concentratioll in roots was nbse 110\\. roots were able to accul11uJa producing a bioaeCUl11ulation coe! operarions coulcl be permitted \\ adapted. It i, note\\orthy that thc ! uranium conccntration and to pro' water to belm\ the sire specific EI

600 ---Influx

500

-o-Dischll

400

..J

t il

::taoo

200

100

FIELD PERFORl\IANCE OF RHIZOFILTRA TIOl\' SYSTE:\IS

In naturally polluted \\ater. a wide range of solutes is e\pected to be found amI. potentially. interfere \\ith the ph;. tofiltration process. Validation of th~ rhilOfiltration concept was carried 011 site with polluted \\ater sources. A pump-and-treat rhizofiltration system \\as recently re~ted for cleaning gwunc!\\atercontaminated \\itll uranium in Ashtabula. Ohio. LSA (Dushenkm et al.. 1997bL A pilot rhizofiltration system with a total \olume of 150() L operated for 6 month". Tile incoming uranium concentration. ranging from 20 to 1800 ~tg/L. \\as pumped from a drilled well and \\;lter \\as aLiju;;ted to pH 5,5, A wtal of more than 200111' of I:ontalllillated

o

o

25 Time

Figure 7,8 Pilot rili!ofilirar;on" ,rem I" gl'O\\ n h~ droponiL'ally ttlr 6 \\\e~ck ... (llld Ih..: PLlI1t, II ere pcriOlliL"Il~ han e,tcd and 1'''1'1. . . y"t~m \\~l" a'''t:mhk~d in (ht.~ gn.'('tlh()lhC. ;.) Th" \I ate I' temperature lIa, 1l1;lilllail1c'd al 2,

Genetic Engineering in Kie\ ,. ~()O()) e\a]uated the u"e of n the Ukraine. A natura] pond ,>elecled as the \\'ater source. ,lose to SO and ] ~()O 84/L for '1l1\\ er planh \\ ere submerged J with fresh plants, This hatch J ill the removal of l)()(i of the II1;..k;. ct al.. ]l)l)71.

J \\ater (aquacultured). young hea\;. meta\:-, from \\ ater (Salt . to remo\ e to'..ic metah from ling 111 Greek) (Ra"kin et al.. L C/ern .. Bl'1IssiUl IWllli., L.. 1'1/ L. call and gn 1\\ !Ill and Ilutrienh. Fi\e-day-old ,arioll;' meta];. from artificially and NO~~ at k~\e!s re,>cmbling \\ere able to concentrate the factor of 5(JO-~OOO (Her the .' and the hexa\'alent Cr anion )accumulation coefficienh of

FIEI D PERfOR\L\\CE OF RHIZOFlLTRATlO\ SYSTDIS

\\ ater at the A'>htabula site \\a~ treated in thb manner with 6-\\eek-old sunflower planb, Figure 7-8 illustrate;.. the performance of the pilot rhizofiltration ~ystem, FI(l\\ rate, of (). I 5-1,60 Llmin \\ ere lhed to entluate the dynamic characteristic,> ()f the rhizofiltratioll system. The pilot-scale rhizofiltration ,,)'-;te111 reduced the U cOI1l:entratinn from ,>e\eral hundred micrograms per liter tn below the regulatory discharge lewl of ~O /lg/L. When the tl()\\ rate \\ as increased, thu" reducing the residence time in the wnb. the highest !low rate that pro\ided acceptable system operation Wet;.. found tn be appro,\imatel) I L/min. Reductions in soluble U concentrations C()ITciated \\ ith the increased U concentration in the mOh. The highest L' concentration in roots \\as oh\er\ cd in the fir"ttank or the \ystem. Under continuou" tllm. roots \\ ere able tll accumulate more than 1,0'; of L' on a dry-\\'eight (OW) ba~i~. producing a bioC\ccllmlllation coefficient of ~O.OOll (OllshenkO\ et a!.. ]l)l)7b). Longer operatioll" (l)uld be permitted \\hen a ~-\\eek plant replacement inten'a] could he adapted. It i~ note\\ orth) that the rhiwfi Itration ~y"t(,111 \\ as able to treat spikes of high uranium concelllrati()l1 and to pn)\ ide reliable rel\1O\ al of uraniulIl from contaminmed \\ater to bel(l\\ the ,ite ;..pecifk EPA ground\\ui.l. OH ,ite, Sunlloll ~r pl'lIlh \\er" J'nr h \\\.?t'" .... and Ih...' n \\121"(' ~r~i!l"..ft"rrt.:'d III th(' rh:/t)ti!tr~1l1nn ':,,(cm for ') \\('('k ..... Plant' \\ ere p"rJt)di,all~ I:.m c,lL'd and leplclccd \\ ltil i'le,h 1'1"l1h Irol11 ihe '1'-I1'''1~ Th" pilol rhi/ilrilllal;,lll . . ~"lem \\