Cong Nghe Xl Kim Loai Nang Trong Dat Bang Thuc Vat

8/6/2019 Cong Nghe Xl Kim Loai Nang Trong Dat Bang Thuc Vat

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CNG NGH X L KIM LOI NNGTRONG T BNG THC VT - HNG TIP CNV TRIN VNGPHYTOREMEDIATION OF HEAVY METAL CONTAMINATED SOILS:

APPROACHES AND PERSPECTIVES

V VN MINH V CHU TUNTrng i hc S phm, i hc Nng

TM TTHin nay, vn nhim kim loi nng trong t ang din ra ph bin nhiu ni trn Thgii. C rt nhiu phng php khc nhau c s dng x l kim loi nng trong t.Tuy nhin, gn y phng php s dng thc vt x l kim loi nng trong t c ccnh khoa hc quan tm c bit bi chi ph u t thp, an ton v thn thin vi mi trng.

Bi vit ny tp trung gii thiu cc loi thc vt siu hp th kim loi nng trong t cngnh trin vng ca cng ngh x l mi trng mi ny.ABSTRACTToday, contamination of soil by heavy metal is occuring all over the world. There are manymethods to treat heavy metal in soils. However, phytoremediation for heavy metal in soils hasrecently emerged as a cheap, safe and environmentally friendly technique. This paper focuseson metal hyperaccumulator plants and their potential use in this new technology.

1. Gii thiuLm sch t nhim l mt qu trnh i hi cng ngh phc tp v vn u t cao.

x l t nhim ngi ta thng s dng cc phng php truyn thng nh: ra t; cnh cc cht nhim bng ho hc hoc vt l; x l nhit; trao i ion, xi ho hoc khcc cht nhim; o t b nhim chuyn i n nhng ni chn lp thch hp,... Huht cc phng php rt tn km v kinh ph, gii hn v k thut v hn ch v dintch,... Gn y, nh nhng hiu bit v c ch hp th, chuyn ho, chng chu v loi bkim loi nng ca mt s loi thc vt, ngi ta bt u ch n kh nng s dng thcvt x l mi trng nh mt cng ngh mi trng c bit. Kh nng lm sch mitrng ca thc vt c bit t th k XVIII bng cc th nghim ca Joseph Priestley,Antoine Lavoissier, Karl Scheele v Jan Ingenhousz. Tuy nhin, mi n nhng nm 1990phng php ny mi c nhc n nh mt loi cng ngh mi dng x l mi trngt v nc b nhim bi cc kim loi, cc hp cht hu c, thuc sng v cc cht phngx. Tuy nhin, trong khun kh ca bi vit ny chng ti ch tp trung gii thiu v kh nngx l cc kim loi nng trong t bi mt s loi thc vt.

2. Cng ngh x l kim loi nng trong t bng thc vt

Thc vt c nhiu cch phn ng khc nhau i vi s c mt ca cc ion kim loitrong mi trng. Hu ht, cc loi thc vt rt nhy cm vi s c mt ca cc ion kim loi,

thm ch nng rt thp. Tuy nhin, vn c mt s loi thc vt khng ch c kh nngsng c trong mi trng b nhim bi cc kim loi c hi m cn c kh nng hp thv tch cc kim loi ny trong cc b phn khc nhau ca chng[1].


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Trong thc t, cng ngh x l nhim bng thc vt i hi phi p ng mt siu kin c bn nh d trng, c kh nng vn chuyn cc cht nhim t t ln thnnhanh, chng chu c vi nng cc cht nhim cao v cho sinh khi nhanh [1,3,6].Tuy nhin, hu ht cc loi thc vt c kh nng tch lu KLN cao l nhng loi pht trinchm v c sinh khi thp, trong khi cc thc vt cho sinh khi nhanh thng rt nhy cmvi mi trng c nng kim loi cao.

X l KLN trong t bng thc vt c th thc hin bng nhiu phng php khcnhau ph thuc vo tng c ch loi b cc KLN nh:

- Phng php lm gim nng kim loi trong t bng cch trng cc loi thc vtc kh nng tch lu kim loi cao trong thn. Cc loi thc vt ny phi kt hp c 2 yu tl c th tch lu kim loi trong thn v cho sinh khi cao. C rt nhiu loi p ng ciu kin th nht (bng 1), nhng khng p ng c iu kin th hai. V vy, cc loi ckh nng tch lu thp nhng cho sinh khi cao cng rt cn thit (bng 2). Khi thu hoch ccloi thc vt ny th cc cht nhim cng c loi b ra khi t v cc kim loi qu himnh Ni, Tl, Au,... c th c chit tch ra khi cy.

- Phng php s dng thc vt c nh kim loi trong t hoc bn bi s hp thca r hoc kt ta trong vng r. Qu trnh ny lm gim kh nng linh ng ca kim loi,ngn chn nhim nc ngm v lm gim hm lng kim loi khuch tn vo trong ccchui thc n.

Bng 1. Mt s loi thc vt c kh nng tch lu kim loi nng cao [1]

Tn loiNng kim loi tch lu trong

thn ( g/g trng lng kh)Tc gi v nm cng b

Arabidopsis halleri

(Cardaminopsis halleri)13.600 Zn Ernst, 1968

Thlaspi caerulescens 10.300 Zn Ernst, 1982Thlaspi caerulescens 12.000 Cd Mdico et al, 1992Thlaspi rotundifolium 8.200 Pb Reeves & Brooks, 1983Minuartia verna 11.000 Pb Ernst, 1974Thlaspi geosingense 12.000 Ni Reeves & Brooks, 1983Alyssum bertholonii 13.400 Ni Brooks & Radford, 1978Alyssum pintodasilvae 9.000 Ni Brooks & Radford, 1978Berkheya codii 11.600 Ni Brooks, 1998Psychotria douarrei 47.500 Ni Baker et al., 1985Miconia lutescens 6.800 Al Bech et al., 1997Melastoma malabathricum 10.000 Al Watanabe et al., 1998

Trong nhng nm gn y, ngi ta quan tm rt nhiu v cng ngh s dng thc vt x l mi trng bi nhiu l do: din tch t b nhim ngy cng tng, cc kin thckhoa hc v c ch, chc nng ca sinh vt v h sinh thi, p lc ca cng ng, s quantm v kinh t v chnh tr,... Hai mi nm trc y, cc nghin cu v lnh vc ny cn rtt, nhng ngy nay, nhiu nh khoa hc c bit l M v chu u c rt nhiu tinghin cu c bn v ng dng cng ngh ny nh mt cng ngh mang tnh cht thngmi. Hn ch ca cng ngh ny l ch khng thxem nh mt cng ngh x l tc thi vph bin mi ni. Tuy nhin, chin lc pht trin cc chng trnh nghin cu c bn c

th cung cp c cc gii php x l t mt cch thn thin vi mi trng v bn vng.Nm 1998, Cc mi trng Chu u (EEA) nh gi hiu qu kinh t ca cc phng phpx l KLN trong t bng phng php truyn thng v phng php s dng thc vt ti1.400.000 v tr b nhim Ty u, kt qu cho thy chi ph trung bnh ca phng php


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truyn thng trn 1 hecta t t 0,27 n 1,6 triu USD, trong khi phng php s dng thcvt chi ph thp hn 10 n 1000 ln [1].

Bng 2. Mt s loi thc vt cho sinh khi nhanhc th s dng x l kim loi nng trong t [1]

Tn loi Kh nng x l Tc gi v nm cng bSalix KLN trong t, nc Greger v Landberg, 1999

Populus Ni trong t, nc v ncngm

Punshon v Adriano, 2003

Brassica napus, B. Juncea,B. nigra

Cht phng x, KLN, Setrong t

Brown, 1996 v Banuelos etal, 1997

Cannabis sativa Cht phng x, Cd trong t Ostwald, 2000

Helianthus Pb, Cd trong t EPA, 2000 v Elkatib et al.,2001

Typha sp. Mn, Cu, Se trong nc thim khong sn

Horne, 2000

Phragmites australis KLN trong cht thi mkhong sn

Massacci et al., 2001

Glyceria fluitans KLN trong cht thi mkhong sn

MacCabe v Otte, 2000

Lemna minor KLN trong nc Zayed et al., 1998

3. Cc loi thc vt c kh nng hp th kim loi

C t nht 400 loi phn b trong 45 h thc vt c bit l c kh nng hp th kimloi [2, 3, 6]. Cc loi ny l cc loi thc vt thn tho hoc thn g, c kh nng tch lu vkhng c biu hin v mt hnh thi khi nng kim loi trong thn cao hn hng trm ln sovi cc loi bnh thng khc. Cc loi thc vt ny thch nghi mt cch c bit vi cc iu

kin mi trng v kh nng tch lu hm lng kim loi cao c th gp phn ngn cn ccloi su b v s nhim nm [1].

C nhiu gii thuyt c a ra gii thch c ch v trin vng ca loi cngngh ny.

3.1. Gi thuyt s hnh thnh phc hp: c ch loi b cc kim loi c ca cc loithc vt bng cch hnh thnh mt phc hp. Phc hp ny c th l cht ho tan, cht khngc hoc l phc hp hu c - kim loi c chuyn n cc b phn ca t bo c cc hotng trao i cht thp (thnh t bo, khng bo), y chng c tch lu dng cc hpcht hu c hoc v c bn vng [1,4].

3.2. Gi thuyt v s lng ng: cc loi thc vt tch kim loi ra khi t, tch lutrong cc b phn ca cy, sau c loi b qua l kh, ra tri qua biu b hoc b tchy.


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3.3. Gi thuyt hp th th ng: s tch lu kim loi l mt sn phm ph ca c chthch nghi i vi iu kin bt li ca t (v d nh c ch hp th Ni trong loi tserpentin).

3.4. S tch lu kim loi l c ch chng li cc iu kin stress v sinh hoc husinh: hiu lc ca kim loi chng li cc loi vi khun, nm k sinh v cc loi sinh vt n l c nghin cu [1,3,4].

Ngy nay, s thch nghi ca cc loi thc vt c kh nng hp th kim loi nng chac lm sng t bi c rt nhiu yu t phc hp tc ng ln nhau. Tch lu kim loi l mtm hnh c th ca s hp th dinh dng khong thc vt. C 17 nguyn t c bit lcn thit cho tt c cc loi thc vt bc cao (C, H, O, N, S, P, K, Ca, Mg, Fe, Mn, Cu, Zn, B,Mo, Cl v Ni). Cc nguyn t a lng cn thit cho cc loi thc vt nng cao, trongkhi cc nguyn t vi lng ch cn i hi nng rt thp. Cc loi thc vt c s dng x l mi trng bao gm cc loi c kh nng hp th c cc kim loi dng vt cnthit nh Cu, Mn, Zn v Ni hoc khng cn thit nh Cd, Pb, Hg, Se, Al, As vi hm lngln, trong khi i vi cc loi thc vt khc cc nng ny l cc k c hi [1,5,6].

4. Cc hng tip cn trong vic s dng thc vt x l mi trng

Nh phn trn gii thiu, thng mi ho cng ngh x l mi trng bng thcvt, cn phi tm kim cc loi thc vt c kh nng cho sinh khi nhanh v tch lu nng kim loi cao trong cc c quan v d dng thu hoch. C hai hng tip cn ch yu trongvic s dng thc vt x l mi trng:

- Nhp ni v nhn ging cc loi c kh nng siu hp th kim loi(hyperaccumulator).

- ng dng k thut di truyn pht trin cc loi thc vt cho sinh khi nhanh v citin kh nng hp th, chuyn ho, chng chu tt i vi cc iu kin mi trng[1].

Hng tip cn th nht, pht trin ch yu M bi nhm nghin cu ng u lChaney, bao gm cc bc c bn nh: chn cc loi thc vt, thu thp ht hoang di v thnghim kh nng x l mi trng, nhn ging, ci tin iu kin trng v tin hnh p dngi tr. Hiu qu ca h thng ny c cng b trong vic x l Co v Ni. Tuy nhin, tcgi cho rng cc loi thc vt t nhin l khng to ra cc sn phm mang tch cht thngmi. iu ny, cng ni ln rng, cng ngh sinh hc s l trin vng rt ln trong vic dunghp 2 c tnh c bn l kh nng siu hp th v tng sinh khi.

Chng trnh nghin cu ca cng ng chu u bao gm 2 d n i vi thc vtchuyn gen phc v cho hng ny c tin hnh. D n th nht l chuyn gen c khnng siu hp th kim loi cy Thlaspi caerulescens vo cy Thuc l v cy M tc lnhng loi cho sinh khi nhanh. Trong khi d n th hai tp trung ci tin kh nng chngchu v hp th kim loi. n nay, kt qu nghin cu thnh cng nht l s dng gen merA9ca vi khun chuyn vo cyArabidopsi x l Hg (II) [1].

Tuy nhin, c mt s ro cn nht nh ca hng tip cn thc vt chuyn gen mt

s nc v mt php l, x hi v sinh thi. Trin vng ca thc vt chuyn gen trong viclm sch cc vng nhim c l s lm thay i mt s quan im x hi i nghch. D saoth cc nghin cu trong tng lai cn phi khng ch ch tm n phng php to ra nhng


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thc vt hu hiu cho x l mi trng m cn phi sng lc nhng tc ng tim n ca thcvt chuyn gen i vi mi trng.

5. Kt lun

Cng ngh x l mi trng bng thc vt l mt cng ngh mi v hp dn c

cp trong nhng nm gn y. K thut ny c cho bit l c mt trin vng c bit trongvic lm sch kim loi trong t, t nht l di iu kin c th no v c s dng trongh thng qun l thch hp. S pht trin ca k thut di truyn v sinh hc phn t l rt cnthit cho loi cng ngh ny.

Tuy nhin, s pht trin ca cng ngh hp dn ny s khng th c tnh kh thi nukhng c s ng gp v gi ca cc nhm nghin cu nh l. Hn 30 nm qua, cc nh khoahc c nhiu nghin cu ng gp quan trng v kh nng c bit ca thc vt trong xl mi trng. Tuy nhin, nghin cu iu tra v lnh vc ny vn lun cn thit v phi chng ng bo tn ngun ti nguyn di truyn t nhin to ln, qu gi cc mi trng b nhim kim loi v nng cao kin thc ca chng ta v c ch thch nghi t nhin ca ccloi siu tch lu kim loi.

TI LIU THAM KHO

[1] Barcel J., and Poschenrieder C., Phytoremediation: principles and perspectives,Contributions to Science, institute dEdtudis Catalans, Bacelona, pp 333 344, 2003.

[2] Brooks RR (ed.), Plants that Hyperaccumulate heavy metal, CAB International,Wallingford, UK, pp380, 1998.

[3] Jerald L. Schnoor,Phytoremediation Of Soil And Groundwater, Center for Global andRegional Environmental Research and Dept. of Civil and Environmental Engineering,The University of Iowa, IA 52242, 2002.

[4] Saxena PK. et al, Phytoremediation of heavy metal contaminated and polluted soils,In: MNV prasad & J Hagemayr (eds) Heavy metal stress on plants, From molecules toecosystems, Springer Verlag, Berlin, pp 305-329, 1999.

[5] Schat H. et al, Metal specific patterns of tolenrance, uptake, and transport of heavymetals in hyperaccumulating and non-hyperaccumulating metallophytes, In: N Terry,G Banuelos (eds.), Phytoremediation of contaminated soils and waters. CRC PressLLC; Boca Raton, FL., USA, pp 171 188, 1999.

[6] Timothy Oppelt E., Introduction to Phytoremediation. National Risk Management Research Laboratory, Office of Research and Development, U.S. EnvironmentalProtection Agency, Cincinnati, Ohio 45268, 2000.

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Cong Nghe Xl Kim Loai Nang Trong Dat Bang Thuc Vat