Study on Tolerance and Accumulation Potential of Biofuel Crops for Phytoremediation of Heavy Metals

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1 Interntionl Journl of Environmentl Siene nd Development, Vol. 4, No. 2, April 2013 Study on Tolerne nd Aumultion Potentil of Biofuel Crops for Phytoremedition of Hevy Metls Kokyo Oh, To Li, Hongyn Cheng, Xieying He, nd Shinihi Yonemohi Astrt Phytoremedition is ost-effetive nd environment-friendly tehnology tht uses plnts for environmentl remedition. In order to promote prtil pplition of phytoremedition, n inome genertion phytoremedition strtegy ws suggested using iofuel rops for utiliztion nd phytoremedition of ontminted soils. In this study, the tolerne nd umultion potentil to hevy metls of two iofuel plnts nd two umultor plnts were investigted in order to evlute their suitility for phytoremedition. Two iofuel rops, mize (Ze mys L.) nd sunflower (Helinthus nnuus L.), nd two umultor plnts, Elsholtzi splendens (ES) nd Kummerowi strit (KS) were exposed to the hydroponi mixtures of P, Cu nd Cd. Results showed tht, t the 0.01 mol/l pplition level of P, Cu nd Cd, sunflower hd the highest umultion ility for P, Cu nd Cd in the shoot prt ompred to other three plnts, nd mize hd similr umultion level to ES nd KS. Sunflower lso hd muh higher shoot/root rtios of umultion for Cu nd Cd thn mize. However, sunflower showed lower tolerne to P, Cu nd Cd ontmintion thn mize, ES nd KS. This study provided useful dt supporting the use of iofuel plnts in phytoremedition. Index Terms Phytoremedition, hevy metls, iofuel rops, mize, sunflower. I. INTRODUCTION Soil ontmintion with hevy metls hs een worldwide onern s it poses gret thret to rop prodution, food seurity, wter pollution nd humn helth. As n emerging green tehnology for tretment of ontminted soils, phytoremedition hs inresingly reeived extensive ttention over the pst severl dedes [1], [2]. Phytoremedition is defined s the use of green plnts to remove, redue, degrde, or immoilize ontminnts from ontminted environmentl mtrix suh s soil, wter nd sediments [1], [3]. With pplition of phytoremedition in the mngement nd remedition of ontminted environment, the gret positive hrteristis re tht the ost is very low in omprison to other physiohemil methods, nd it n remove pollutnts from soil nd redue their movement towrds groundwter, sustins the soil properties, nd my improve soil qulity nd produtivity. Mnusript reeived Jnury 1, 2013; revised Ferury 15, This work ws supported in prt y the Grnt-in-Aid for Sientifi Reserh of Jpn Soiety for the Promotion of Siene (No nd No ). Kokyo Oh nd Shinihi Yonemohi re with the Center for Environmentl Siene in Sitm, 914 Kmitndre, Kzo, Sitm Jpn (e-mil: o.kokyo@pref.sitm.lg.jp). To Li, Hongyn Cheng, nd Yinghe Xie re with the College of Resoures nd Environment, Shnxi Agriulturl University, Shnxi, Chin (e-mil: ndlito@126.om, ndhenghy@yhoo.om.n). However, phytoremedition usully hs low remedition rte, nd generlly need longer period (usully over 3 or 5 yers) [1], [3], [4]. The onventionl phytoremedition wy hs foused on metl hyperumultor or umultor plnts, whih n grow in hevy metl ontminted soils, nd is ple of umulting potentilly phytotoxi elements to onentrtions muh higher thn the norml plnts growing in the sme environment [1], [3], [5]. At present, more thn 400 speies of umultor plnts hve een found [4], [5]. However, most of these umultor plnts usully hd very high hevy metl ontents, so fter hrvested the plnts usully need ininertion tretment [4]. Moreover, their individul plnts re usully smll, slow growing, nd lk of eonomi vlue [2], [6], [7]. In this wy, the onventionl phytoremedition needs ost yer y yer, nd the owners of the ontminted sites hve no inome during the remedition period. Therefore, t present the fully prtil pplition of field phytoremedition is still few, lthough mny ompnies hve strted their usiness in phytoremedition. To promote the prtil pplition of phytoremedition for ontminted soil, we re fousing on estlishing inome genertion phyotoremedition systems y using iofuel plnts (suh s mize, sunflower, soyen, rley nd whet) [4], [7]. Insted of the speil umultor plnts, the iofuel rops re used for oth utiliztion nd phytoremedition of the ontminted soils. Biofuel rops in the ontminted soil n oth remedite ontminted soils, nd produe vlule iofuel iomss. In this wy, the owners of the ontminted lnd n otin inome during the phytoremedition period, through whih the prtil pplition of phytoremedition possily e gretly promoted for soil resoures onservtion. In this study, hydroponi experiment ws onduted to ompre the hevy metl tolerne nd umultion potentil of iofuel plnts with omprison to umultor plnts, in order to ssess the potentil of the iofuel rops for hevy metl phytoremedition. II. MATERIALS AND METHODS A. Test Plnts A hydroponi experiment ws onduted in green house to ompre the tolerne nd umultion potentil of the plnts to hevy metls. In the experiment, mize (Ze mys L.) nd sunflower (Helinthus nnuus L.) were used s iofuel rops. In order to mke omprison with metl umultor plnts, Elsholtzi splendens (ES) nd Kummerowi strit DOI: /IJESD.2013.V

2 Interntionl Journl of Environmentl Siene nd Development, Vol. 4, No. 2, April 2013 (KS) were used in the experiment, s they were reported to hve high ility for umultion or tolerne to hevy metls [8]-[10]. B. Solution Preprtion Initilly the seeds of the four plnts were grown in trys with ommeril red ll erth used s soil for plnt ulture. The verge temperture of green house ws pproximtely 28 t the dy time nd 20 t night. Finlly 3-week seedlings of the plnts of similr size were trnsplnted to plsti pots ontining solution ulture to initite the green house experiment. Control, 0.01mol/L nd 0.1mol/L levels of P, Cu nd Cd tretments were used, dded s P(NO 3 ) 2, Cu(NO 3 ) 2 3H 2 O, nd Cd(NO 3 )2 4H 2 O, respetively. The solution ws erted gently with ir ompressors, mintined t ph 5.8±0.3 djusted with 0.1 mol/l NOH or 0.1 mol/l HCl, nd ws renewed every dy during the experiment. The plnts were hrvested fter 5d exposure of seedlings to tretment solution for ssy of P, Cu nd Cd umultion in the plnts. The experiment ws rndomly rrnged with three replites for eh tretment. The olleted plnt smples were pled in plsti gs, leled refully nd rought to the lortory. C. Smpling nd Anlysis The hrvested plnts were seprted into roots nd shoots, nd wshed thoroughly with tp wter to remove dirt, then wshed with demonized wter three times. Smples were first dried for 3 dys t room temperture, then in n oven t 70 C until the weight remined unhnged nd were used for further nlyses. The iomss of eh plnt ws weighted. Dried plnt smples of roots nd shoots were ground in fine powder in mehnil grinder (TML160, Tesom, Jpn). The ground smples were mixed uniformly. The smples of plnt-prts were hemilly nlyzed for detetion of hevy metls of P, Cu nd Cd. Plnt smple were weighed nd digested with onentrted HNO 3 nd H 2 O 2 with hot-plte method nd nlyzed using ICP-AES. Men vlues of triplite su smples of the plnt smples were onsidered. During the experiment, ll ontiners were lened with tp wter, nd deionized wter. Sttistil nlyses were performed nd Lest signifint differene (LSD) t the 5% onfidene level ws used for omprison etween tretments. III. RESULTS AND DISCUSSION A. Plnt Growth Different influene of hevy metl tretments on the growth of the four plnts ws oserved. Biomss under different Cd ddition levels ws shown in Fig. 1 nd Fig. 2. The trend of shoot iomss prodution under 0.01mol/L Cd level is: mize>es>ks>sunflower, while tht under 0.1mol/L Cd level is: mize>ks>sunflower>es. The trend of root prodution under 0.01 mol/l Cd level is: mize > ES>KS>Sunflower, while tht under 0.1mol/L Cd level is: mize>ks>sunflower>es. Generlly, mize hd the lrgest shoot nd root iomss prodution under oth 0.01 mol/l nd 0.1 mol/l Cd ddition levels. Biomss of mize nd KS ws not redued y Cd pplition t oth 0.1 mol/l nd 0.1 mol/l. This indited tht Cd pplition did not put influene to growth of mize nd KS. Shoot Biomss(g) CK Cd0.01mol/l Cd0.1mol/l Mize Sunflower ES KS Fig. 1. Shoot iomss of plnts under different Cd pplition levels. Root Biomss(g) CK Cd0.01mol/l Cd0.1mol/l d Mize Sunfloewr ES KS Fig. 2. Root iomss of plnts under different Cd pplition levels. TABLE I: TOTALBIOMASS UNDER DIFFERENCT APPLICAION LEVELS OF LEAD (G, MEANS±SD) Sunflower Mize ES KS CK 0.21± ± ± ± mol/l 0.19± ± ± ± mol/l 0.15± ± ± ±0.12 However, the derese of iomss prodution of sunflower nd ES under 0.1 mol/l Cd pplition ws found ompred to tretments of CK nd 0.01 mol/l Cd, showing tht the growth of sunflower nd ES ws retrded with high Cd ontmintion. Sunflower ws lso ffeted y P tretment. As shown in Tle I, ompred to ontrol, 0.1 mol/l P tretment redued iomss of sunflower, ut no influene on other three plnts. Atully, the influene of hevy metl ontmintion to sunflower growth ws lerly oserved y the plnt pperne. As shown in Piture of Fig.2, sunflower lmost died 3 dys fter exposure in the tretments of 0.1 mol/l Cd or 0.1 mol/l Cu. These dt indites tht sunflower hd lower tolerne to Cd, P nd Cu ontmintion thn mize. B. Hevy Metl Conentrtions in Plnts The metl onentrtions of P, Cu nd Cd in shoot nd root of the plnts under the lower ontmintion tretment in whih the onentrtions of P, Cu nd Zn were 0.01 mol/l d 153

3 Interntionl Journl of Environmentl Siene nd Development, Vol. 4, No. 2, April 2013 ws shown in Tle II nd Tle III. As shown, the onentrtions of the hevy metl elements vried signifintly mong the four plnts. Sunflower hd the highest onentrtion of P, Cu nd Cd in shoot under this light ontmintion ondition. The onentrtions of P, Cu nd Cd in the shoot of the sunflower were, respetively, out 5 times for P, 3 times for Cu nd 6 times for Cd higher thn tht of mize. Mize hd similr or higher onentrtion ompred to ES nd KS. umultion [9], however, we found their onentrtions of P, Cu nd Cd were not so high in this study. TABLE II: HEAVY METAL CONCENTRATIONS IN SHOOT OF THE PLANTS (UG/G, MEANS±SD) P Cu Cd Mize 48.5± ± ±5.72 Sunflower 268± ± ±17.4 E.S 102± ± ±2.28 KS 39.4± ± ±1.79 TABLE III: HEAVY METAL CONCENTRATIONS IN ROOT OF THE PLANTS (UG/G, MEANS±SD) P Cu Cd Mize 599± ± ±29.9 Sunflower 4921± ± ±13.9 ES 3150± ± ±9.07 KS 1755± ± ±176 Fig. 4. Cd onentrtions in shoot of the plnts under different Cd tretments. Fig. 3. Influene on sunflower growth y Cd nd Cu tretment three dys fter exposure to Cd nd Cu tretment solution. As to the onentrtion in root, sunflower hd higher onentrtions of P nd Cu, ut lower onentrtion of Cd thn mize (Tle III). The hevy metl onentrtion in the plnts inresed with the inrese of metl ddition levels. As shown in Fig. 4, the Cd onentrtion under 0.1 mol/l Cd pplition in the shoot for mize, ES nd KS were 123, 196 nd 186 ug/g respetively, whih ws 4 to 11 times tht under 0.01 mol/l pplition. Under the 0.01 mol/l Cd level, the sunflower hd the highest Cd onentrtion (103 ug/g), whih ws out 3 times tht of mize (37.8 ug/g), nd 5 times tht of ES (17.8 ug/g) nd KS (22.1 ug/g). However, under the 0.1 mol/l Cd level, sunflower hd the lowest Cd onentrtion (49 ug/l). The reson ws tht the sunflower seedlings died in the 0.1 mol/l Cd solution s mentioned ove. The results showed tht hevy metl onentrtions in the plnts quite vried with plnt speies. Sunflower showed notiele higher onentrtion of P, Cd nd Cu, espeilly in the shoot. Although ES were reported s n umultor plnt for Cu [8], nd KS ws lso reported for hevy metl C. Hevy Metl Aumultion Potentil of the Plnts The hevy metl umultion mount from eh pot (3 seedlings) y the plnt speies in the solution with 0.01 mol/l of P, Cu nd Cd ws shown in tle IV. As shown, the umultion mount in shoot rnged from 8.46 to 60.6 ug/pot P, 3.08 to 20.7 ug/pot Cu, nd 3.76 to 29.1 ug/pot Cd, respetively, nd the highest umultion levels for P, Cu nd Cd were oserved in sunflower. Mize hd lower umultion level thn ES for P, ut no signifint differene ws found for Cu nd Cd. Compred to KS, mize hd signifint higher umultion level for Cu, ut hd no signifint differene for P nd Cd. Generlly, the sunflower showed the highest umultion levels for P, Cu nd Cd in the shoot ompred to other three plnts. Mize showed umultion ility in shoot higher thn or similr to ES nd KS (Tle IV). However, the umultion in root ws different from tht in shoot. Compred to mize nd KS, sunflower nd ES hd very muh higher P umultion levels, very lower Cd umultion levels, nd similr Cu umultion levels (Tle V). Shoot/root rtio of metl umultion (Fig. 5) lerly showed the different umultion hrteristis mong 154

4 Interntionl Journl of Environmentl Siene nd Development, Vol. 4, No. 2, April 2013 plnt speies nd metls. Shoot/root rtio of the metl umultion rnged from 0.17 to 0.46 for P, 0.31 to 2.35 for Cu, 0.30 to 14.9 for Cd, respetively. Sunflower hd muh higher shoot/root rtios of umultion, espeilly for Cd nd Cu, showing tht sunflower hd higher metl trnsporttion potentil from root to shoot thn other three plnt speies, nd possily min umulted hevy metls in shoot, espeilly for Cd nd Cu. ES ws lso oserved very high shoot/root rtio of Cd umultion. Mize hd shoot/root rtios of metl umultion rnged from 0.30 to 0.49, inditing tht most P, Cu nd Cd ws umulted in the root, whih ws quite different from sunflower. Phytoremedition potentil of plnts re minly deided y ove ground (shoot) hevy metl umultion levels [3], [4], [11]. This study showed tht the two iofuel plnts hd higher or similr levels of metl umultion potentil for hevy metls in shoot ompred to the two umultor plnts. Therefore, our study showed tht the two iofuel plnts, sunflower nd mize, generlly hd higher or similr phytoremedition potentil for hevy metls ompred to the two umultor plnts. TABLE IV: HEAVY METAL ACCUMULATION IN THE SHOOT OF THE PLANTS (UG/POT, MEANS±SD) P Cu Cd Mize 10.8± ± ±1.28 Sunflower 60.6± ± ±3.93 ES 27.2± ± ±0.61 KS 8.46± ± ±0.38 TABLE V: H HEAVY METAL ACCUMULATION IN THE UNDERGROUND PARTS OF THE PLANTS (UG/POT, MEANS±SD) P Cu Cd Mize 35.9± ± ±1.79 Sunflower 132± ± ±0.37 ES 170± ± ±0.17 KS 49.1± ± ±4.93 It is resonle wy to regrd the ontminted soils s potentilly reoverle resoure for oth remedition nd utiliztion. Phytoremedition hve so fr minly foused on umultor or hyperumulting plnts, these speil plnts usully hve smll iomss produtivity, nd no pprent eonomi vlue, whih mkes the phytoremedition ost yer y yer, thus gretly limited the prtil pplition of phytoremedition. Atully, it is diffiult to onvine the lol people, espeilly in developing ountries, to grow speil umultors in the ontminted fields for the sole purpose of soil remedition unless they ould otin finnil inome. The present study showed tht the two iofuel plnts hd high potentil for phytoremedition, espeilly sunflower hd muh higher potentil of phytoremedition thn the two umultor plnts. Besides eing used for phytoremedition, the sle of the iofuel rops for iofuel prodution ould ring inome to the remeditors or the owners of the ontminted sites. Considering the eonomi effets of the iofuel plnts, the sunflower nd mize were possily promising wy for oth utiliztion nd remedition of ontminted sites. As sunflower showed lower tolerne for hevy metls, it ws possily more suitle for phytoremedition of soils with lower level of ontmintion. Fig. 5. Shoot/root rtio of the metl umultion in the plnts. IV. CONCLUSIONS In summry, sunflower hd the highest umultion level for P, Cu nd Cd in the shoot ompred to other three plnts. Mize lso showed similr umultion level for P, Cu nd Cd ompred to ES nd KS. This onluded tht the two iofuel plnts, sunflower nd mize generlly hd higher or similr phytoremedition potentil for hevy metls ompred to the two umultor plnts. The sunflower hd the highest umultion ility under the low ontmintion level (0.01 mol/l) for P, Cu nd Cd, ut hd poor tolerne to hevy metls under high ontmintion level (0.1 mol/l) of P, Cu nd Cd. This study lso showed tht sunflower umulted more Cu nd Cd in shoot thn in root, wheres mize minly umulted P, Cu nd Cd in root. Mize showed similr umultion levels to the two umultor plnts oth under low nd high ontmintion levels, showing the mize hd high tolerne to P, Cu nd Cd ontmintion thn the sunflower. Biofuel plnts n oth remedite ontminted soils nd produe vlule iomss, whih n ring inome for the owners of the ontminted sites, it would e resonle hoie to use them for utiliztion nd remedition of the ontminted sites. Therefore, this study primrily provided vlule dt supporting the use of iofuel plnts in phytoremedition. REFERENCES [1] X. J. Wng, F. Y. Li, M. Okzki, nd M. Sugiski, Phytoremedition of ontminted soil, Annul Report CESS, vol. 3, pp , [2] I. D. Pulford nd C. Wtson, Phytoremedition of hevy metl-ontminted lnd y trees review, Environmentl Interntionl, vol.29, pp , [3] C. A. Slt, R. D. Smith, nd I. Rskin, Phytoremedition, Annu. Rev. Plnt Physiol, vol. 49, pp , [4] K. Oh, Y. H. Xie, J. P. Hong, T. H. Co., Q. Lin, S. Yonemohi, M. Ogw, nd T. Hirno, A Strtegy for phytoremedition of Contminted Agriulturl Soils with Biofuel Crops, in Pro Interntionl Conferene on Green Energy nd Environmentl Sustinle Development, pp , [5] Y. Wng, Q. Li, J. Shi, Q. Lin, X. Chen, W. Wu, nd Y. Chen, Assessment of miroil tivity nd teril ommunity 155

5 Interntionl Journl of Environmentl Siene nd Development, Vol. 4, No. 2, April 2013 omposition in the rhizosphere of opper umultor nd nonumultor, Soil Bio Biohem, vol. 40, pp , [6] K. Oh, S. Hosono, Q. Lin, Y. H. Xie, F. Y. Li, C. J. Jing, nd T. Hirno, Remedition of Dioxin-ontminted Soil with Comintion of Biofuel rops nd white rot fungus, Orgnohlogen Compounds, vol. 71, pp , [7] K. Oh, X. F. Hu, C. Q. He, S. Yonemohi, nd F. Shi, Perspetive on pplition of phytoremedition tehnology in remedition of ontminted soils, in Pro World Congress on Engineering nd Tehnology, pp , [8] J. Song, F. J. Zho, Y. M. Luo, S. P. MGrth, nd H. Zhng, Copper uptke y Elsholtzi splendens nd Silene vulgris nd ssessment of opper phytovilility in ontminted soils, Environmentl Pollution, vol. 128, pp , [9] G. K. Evnylo, A. O. Aye, C. Dunds, C. E. Zipper, R Lemus, B Sukkriyh, nd J. Rokett, Hereous vegettion produtivity, persistene, nd metls uptke on iosolids-mended mine soil, J. Environ. Qul, vol. 34, no. 5, pp , [10] X. Chen, C. Wu, J. Tng, nd S. Hu, Arusulr myorrhize enhne metl led uptke nd growth of host plnts under snd ulture experiment, Chemosphere, vol.60, pp , [11] B. Roinson, S. Green, T. Mills, B. Clothier, M. vn der Velde, R. Lplne et l., Phytoremedition: using plnts s iopumps to improve degrded environments, Aust. J. Soil Res., vol. 41, pp , Kokyo Oh is senior reserher in Center for Environmentl Siene in Sitm, Jpn. He grduted with his MSi degree nd Ph.D. degree in Chinese Ademy of Sienes, nd ws honored s STA reserh fellow y Jpn government. The reserh res inlude soil environment, wter environment onservtion environmentl hemistry, nd tmospheri environment. His urrent reserh is minly on soil remedition, environmentl gronomy, tmospheri PM2.5 nd wter environment onservtion. He hs pulished more thn 90 pulitions. To Li is mster ourse student of Shnxi Agriulturl University (Chin). She is studying nd doing reserh ssistnt on environmentl siene. She hs een invited to do interntionl oopertion reserh in Jpn for two times s she is n exellent student with very oopertive personl hrter s well s tive nd hrdworking spirit. Hongyn Cheng is professor of Shnxi Agriulturl University (Chin). Her urrent reserh interest is on soil environment, phytoremedition, nd hemil nlysis. She hs pulished more thn 30 pulitions, nd tively ooperted with overses reserh institutions. 156