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2 Chpter 15 Lechility nd Vegetle sorption of Hevy Metls from Sewge Sludge Biochr Mieko Ychigo nd Shinjiro Sto dditionl informtion is ville t the end of the chpter 1. Introduction Mngement of industril wstes hs een one of the most chllenging prolems in most urn municiplities due to incresing wste volume with limited disposl res, nd energy-consuming nd high-cost tretment processes for disposl. In Jpn, lthough the totl volume of the industril wste generted hs een reltively constnt since 199 eing pproximtely 4 million tons per yer, remining cpcity of the finl disposl for the industril wste hs decresed y pproximtely 2% since 1994, reching to 172 million m 3 in 27 (Ministry of the Environment Government of Jpn, 211). This disposl cpcity is predicted to e filled in the verge of 8.5 yers for Jpn, nd 3.6 yers for Tokyo Metropolitn res. Due minly to high cost of tretment for proper disposl, illegl dumping of the industril wste hs een new prolem despite of severe regultion nd monitoring of ffected res. The numer nd totl volume of unsolved cses of illegl dumping nd improper disposl of the wste were 2,61 nd 1.78 million tons, respectively, in 21 (Ministry of the Environment Government of Jpn, 211). Sewge sludge is one of the most produced industril wstes nd comprised pproximtely 2% (77.2 million tons) of the totl volume of industril wstes generted cross Jpn in 21 (Ministry of the Environment Government of Jpn, 211). However, the volume of its finl disposl ws insignificnt (.37 million tons) since the mjority of sewge sludge were reclimed nd/or treted y intermedite processing such s thickening, dewtering, neroic digestion, composting, incinertion, croniztion, nd melting. On the dry solid sis, 78% of the totl volume of sewge sludge (1.72 million tons) ws recycled in eneficil pplictions minly for construction mterils (1.39 million tons), energy production (.2 million tons), nd ppliction in griculture nd horticulture s lterntive fertilizers nd/or soil conditioner (.31 million tons). Due to new technology nd diversifiction of sewge sludge recycling techniques, further recycling venues re expected prticulrly for production of energy, griculture, forestry, livestock, nd fisheries in the future. 213 Ychigo nd Sto; licensee InTech. This is n open ccess rticle distriuted under the terms of the Cretive Commons ttriution License ( which permits unrestricted use, distriution, nd reproduction in ny medium, provided the originl work is properly cited.

3 4 Soil Processes nd Current Trends in Qulity ssessment Pyrolysis process of sewge sludge is one of the useful pproches for sewge sludge recycling, nd its product clled sewge sludge iochr (SSB) cn e used s supplementl or lterntive mteril to col for therml power plnts. Some municiplities in Jpn hve initited to use SSB s prt of therml sources for energy production. In Tokyo, since 27, 8,7 tons of SSB hve een produced per yer from 99, tons of sewge sludge nd mixed with col for energy plnt to contriute pproximtely 1% of the totl clorific vlue y the plnt. The SSB produced is pyrolysed t 5 o C for one hour nd genertes 2, kcl kg 1 of het clorie, which is equivlent to one third of tht of col. ichi Prefecture strted similr project s Tokyo in 212, nd uses 2,7 tons of SSB pyrolysed t 5 o C from 33, tons of sewge sludge every yer to generte 4.6 million kwh of energy, which is cple of providing electricity equivlent to nnul usges of typicl 1,27 households in the re. Sewge sludge iochr cn e lso used for supplementl or lterntive fertilizer mteril for crop production. Different feedstock properties nd pyrolysis tempertures, however, yield SSB with different physicochemicl properties, thus exhiit different degrees of effect when SSB is pplied to soil s soil mendments or fertilizers for improving crop production or soil properties (Chn & Xu, 29). n SSB produced t 8 o C in Jpn contined moderte mounts of mcronutrients for crop production, mong which P ws reltively high (78.9 g P kg 1 ), nd reltively high mounts of hevy metls (1,1 mg Cu kg 1, 1,63 mg Zn kg 1, 4 mg Cd kg 1, 126 mg Ni kg 1 ) which were within the limits legislted in Jpn (Kwno et l., 212). Effects of SSB ppliction to soils up to 4% y weight on the growth of Begoni (Begoni semperflorens) differed depending on the soil type nd were more positively pronounced in soils more infertile such s snd-dune nd yellow soils. wstewter sludge iochr pyrolysed t 55 o C in ustrli ws pplied t rte of 1 t h 1 nd improved the production of cherry tomtoes (Lycopersicon esculentum) y 64% ove the control without SSB ppliction (Hossin et l., 21). Some hevy metls such s Cd, Cu, nd Zn were tken up more y the plnt with SSB ppliction (.4, 6.2, nd 22 mg kg 1, respectively) compred with the control, however the plnt uptke of ll 16 metls nd trce elements mesured in the SSB itself were elow the ustrlin mximum permitted concentrtions for food products. s SSB pyrolysis temperture incresed from 3 o C to 7 o C, while iochr yield, fixed C, voltile mtter, totl N, nd inorgnic N contents decresed, ph vlues, sh, totl P, ville (Colwell) P, C, Mg, Fe, S, Zn, Cd contents incresed (Hossin et l., 211). The totl concentrtion of hevy metls such s Cd, Cr, Ni, nd P tends to e enriched in the SSB, ut the iovilility (e.g., DTP-extrctle) of mny of these trce elements ppers to e reduced during pyrolysis process, compred with those in the rw feedstock (Hossin et l., 211; Méndez et l., 212). The vriility of the micronutrient concentrtions in iochr is due to its voltility nd pyrolysis temperture effects on oth composition nd chemicl structure of the iochr (Chn nd Xu, 29). gronomic effects of SSB ppliction to soils, therefore, widely vry depending on physicochemicl properties of the sewge sludge, pyrolysis temperture, nd soil properties, which need to e further clrified including the hevy metl dynmics in order for the SSB ppliction to e rodly ccepted in griculturl nd horticulturl prctices. Therefore, ojectives of this study were to 1) investigte the lechility of hevy metls, prticulrly Cu, Zn, nd Cd from SSB s pplied to soil with vrying rtes, nd 2) evlute the effect of SSB ppliction to soil on plnts growth nd sorption of the hevy metls, using SSB produced t two different pyrolysis tempertures.

4 Lechility nd Vegetle sorption of Hevy Metls from Sewge Sludge Biochr Mterils nd methods 2.1. Soil nd iochr soil used in this study ws forest ndisol collected from mulerry plnttion forest in Hchioji, Tokyo, Jpn (35.692, ) on pr. 29, 211. Surfce 15-cm soils were smpled, dried t 45 o C overnight, sieved through 2 mm, nd used for physicochemicl nlyses nd pot study. Sewge sludge iochrs were produced in commercil plnts t high (pproximtely 8 o C; SSB-H) nd low (pproximtely 3 o C; SSB-L) tempertures, crshed y hummer, nd sieved through 2-mm sieve for chemicl nlyses, nd homogenized etween 2 nd 5 mm in size for the pot study Pot study pot study ws performed on cmpus of Sok University, Tokyo, Jpn. Jpnese mustrd spinch (Brssic rp) nd common en (Phseolus vulgris) were plnted in 1.3 L plnting pots in which the soil nd SSB were mixed t different rtes. Experimentl design ws completely rndomized lock design with triplicte, two different plnts, nd four different ppliction rtes for ech SSB: %, 25%, 5%, nd 75% (v/v) for SSB-H, nd %, 5%, 15%, nd 25% (v/v) for SSB-L. Ech pot received respective mounts of mmonium nitrte, superphosphte, nd potssium chloride efore plnting sed on fertilizer ppliction rtes recommended for the plnts y Tokyo Prefecture: kg N-P-K h 1 for spinch nd kg N-P-K h 1 for en. Ech plnt ws sowed on Sep. 23, 211, nd thinned to 4 spinch individuls nd 2 en individuls per pot 2 weeks lter. The plnts were grown outside nd the pots were covered y plstic sheet only when rinfll events occurred. Wter ws pplied periodiclly to keep 5% of wter holding cpcity of the soil-ssb mix. Spinch nd en were hrvested 46 nd 66 dys fter sowing on Nov. 8 nd Nov. 28, 211, respectively. Throughout the experiment, the dily men temperture fluctuted etween 16 o C nd 22 o C, nd the dily rinfll more thn 2 mm occurred 5 times on Oct. 5, 15, 22, Nov, 11, nd 19, 211. fter hrvest, the plnts were divided into shoot, root, nd en sheth (only for common en), nd dried t 7 o C overnight. The soil nd SSB in the pot were seprted using 2-mm sieve, nd seprtely dried t 45 o C overnight Soil, iochr, plnt nlyses Dry weight (DW) of ech prt of the plnts ws determined fter drying t 7 o C overnight. The soil, SSBs, nd plnt tissues fter the pot study were ground to pss through 15 µm in size nd digested for totl elementl nlyses for hevy metls. Two grms of the soil smple ws heted to 18 o C with 3 ml of concentrted nitric cid in eker with glss wtch on hotplte until it turned like syrup. Then, 3 ml of perchloric cid-nitric cid mixture (1:4) ws dded nd heted for further 1 min. fter cooling, 25 ml of hydrochloric cid (1:5) ws dded nd heted to 13 o C for 1 hr. fter cooling, the content ws quntittively trnsferred

5 42 Soil Processes nd Current Trends in Qulity ssessment to 1 ml flsk nd filtered through Whtmn No 1 pper (Committee for nlyticl Methods for Soil Environment, 1997). Two grms of the SSB smple in crucile ws shed in n electric furnce t 55 o C for 8 hr, nd the sh ws trnsferred to eker with 5 ml of concentrted nitric cid nd heted to 12 o C on hotplte for 3 hr. fter cooling, 25 ml of hydrochloric cid (1:5) ws dded nd heted t 12 o C for further 6 min. fter cooling, the content ws quntittively trnsferred to 25 ml flsk nd filtered through Whtmn No 1 pper (Jpn Soil ssocition, 21). One grm of ech of the shoot, root, nd sheth plnt smples ws heted to 14 o C with 1 ml of concentrted nitric cid in eker with glss wtch on hotplte until the content is reduced to pproximtely 1 ml. fter cooling, the content ws quntittively trnsferred to 25 ml flsk using 1% nitric cid, nd filtered through Whtmn No 1 pper (Committee for Experimentl Methods for Plnt Nutrition, 199). The hevy metls extrctle y.1 M HCl re used s n indictor for environmentl pollution in soils. Vrious chemicl extrctnts re used for single extrction evlution of hevy metls nd my rodly e divided into 3 min clsses: (i) wek replcement of ion slts (MgCl 2, CCl 2, NH 4 CO 3 ), (ii) dilute solutions of either wek cid (cetic cid) or strong cids (HCl, HNO 3 ), nd (iii) chelting gents (DTP, EDP) (Kshem et l. 27). The unuffered ion slt solutions re simple procedure to extrct ioville metls, while use of.1 M HCl solution my reflect iovilility of metls (CSTP, 198). Dried 7. g of soil smples (< 2 mm) ws weighed to 5 ml centrifuge tue nd 35 ml of.1 M HCl ws dded. The tue ws shken horizontlly for 1 hr t 16 stroke min 1, centrifuged t 5, rpm, nd the superntnt ws filtered through Whtmn No 1 pper (Committee for nlyticl Methods for Soil Environment, 1997). Prior to nlyticl determintion, ll filtrtes were further filtered through.45 µm memrne. Totl nd extrctle concentrtions of Cu, Zn, nd Cd in the soil, SSBs, nd plnt smples were determined using ICP (ICPS-7 ver. 2.1, Shimzu) Sttisticl nlyses Significnt differences of the totl nd extrctle concentrtions of Cu, Zn, nd Cd in the soil, SSBs, nd plnt smples mong different SSB ppliction rtes for ech SSB type nd ech plnt were tested y NOV using STTISTIC 6.1 (SttSoft Inc., Tuls, Oklhom, US). Unless otherwise stted, the differences were significnt t p.5 level. 3. Results 3.1. Soil nd iochr properties The ndisol used in this study hd n lmost neutrl ph (H 2 O) of 7.1 nd reltively verge TC nd TN concentrtions (Tle 1). The totl hevy metl concentrtions in the soil were 25 mg Cu kg 1, 43 mg Zn kg 1, nd 4.9 mg Cd kg 1. The SSB used in this study hd slightly cidic ph levels of 6.6 (SSB-H) nd 5.6 (SSB-L). The totl Cd concentrtions were similr for oth SSB types rnging mg kg 1, while the totl Cu nd Zn concentrtions in the

6 Lechility nd Vegetle sorption of Hevy Metls from Sewge Sludge Biochr 43 SSB-H were 5 nd 1.7 times greter thn those in the SSB-L, respectively. The dilute cid (.1 M HCl)-extrctle hevy metls vried mong elements nd SSB types; Cu concentrtion in SSB-H ws 34 times greter thn tht in SSB-L, while Cd in SSB-H ws 5 times less thn tht in SSB-L. ph Totl C Totl N Totl Cu Totl Zn Totl Cd HCl Cu HCl Zn HCl Cd g kg 1 mg kg 1 ndisol SSB-H SSB-L :2.5 soil:solution with H 2 O nd 1:1 SSB:solution with hot H 2 O.1 M HCl-extrctle SSB pyrolysed t high temperture (8 o C; SSB-H) nd low temperture (3 o C; SSB-L) Tle 1. Bsic properties of the soil (ndisol) nd sewge sludge iochr (SSB) used in this study. 3.2 Dry weight of the plnts Seeds of oth plnts with ll tretments germinted 1% except for those of the en with % tretment eing 66% of the germintion rte. The verge DW of individul spinch shoot showed significnt decrese with incresing ppliction rtes of oth SSB-H nd SSB-L, respectively (Fig. 1). The highest DW ws 1.1 nd 1.4 g with % nd % tretment, respectively. The verge DW of the en shoot did not show significnt differences mong the SSB-H tretment, ut significnt increse with % nd 15% compred with tht of control. The verge DW of the spinch root showed significnt decrese with incresing ppliction rte of SSB-H, ut not mong the SSB-L tretment except for % showing the lowest DW mong the tretment (Fig. 1). The verge DW of the en root showed significnt decrese with the incresing SSB-H ppliction rte, nd significnt increse only with SSB- L 15% mong the SSB-L tretment. The verge DW of the en sheth ws not significntly ffected y the SSB ppliction, rnging from.4 nd.18 g mong the SSB-H tretment, nd.4 g for % rte (the en did not er the sheth with % nd 25% rtes; Tle 2).

7 44 Soil Processes nd Current Trends in Qulity ssessment () 2. Dry weight (g) c d B C D B B B () c B B B B.. Spinch Ben Spinch Ben Figure 1. Dry weight of () shoot nd () root prts of Jpnese mustrd spinch nd common en with different ppliction rtes of sewge sludge iochr pyrolysed t high (SSB-H) nd low (SSB-L) tempertures. Different letters denote significnt differences y Fisher test (p<.5) mong different ppliction rtes for ech plnt nd SSB, respectively. DW Cu Zn Cd DW Cu Zn Cd g mg kg -1 g mg kg n n n n n n n n Tle 2. Dry weight (DW), Cu, Zn, nd Cd concentrtions in the common en sheth with different ppliction rtes of sewge sludge iochr pyrolysed t high (SSB-H) nd low (SSB-L) tempertures. Different letters denote significnt differences y Fisher test (p<.5) mong different ppliction rtes for ech SSB nd plnt, respectively. n denotes non-pplicle Totl hevy metl concentrtions in the plnts Copper concentrtions in the spinch shoot significntly incresed with oth SSB tretments over the control, respectively, while, lthough not significntly different, those in the en shoot were lower with oth SSB tretments compred with the control, respectively (Fig. 2). Zinc concentrtions in the spinch shoot significntly incresed with oth SSB tretments over the control, respectively, except for % rte (Fig. 2). On the other hnd, Zn in the en shoot ws not significntly ffected y oth SSB tretments, except for % eing significntly lower thn the control. The shoot prt of ech of oth plnts contined significntly greter Cd concentrtions with oth SSB tretments over the control, respectively (Fig. 2c). The concentrtions in the plnt root were generlly greter thn those in the shoot for ll hevy metls investigted regrdless of the plnt, SSB type nd ppliction rte. The Cu concentrtion

8 Lechility nd Vegetle sorption of Hevy Metls from Sewge Sludge Biochr 45 in the spinch root ws gretest with % rte nd % rte mong SSB-H nd SSB-L tretments, respectively, while Cu in the en root ws gretest with % rte nd %, mong ech SSB tretment, respectively (Fig. 2d). The Zn concentrtions in the spinch root with % nd 5% rtes were significntly greter thn tht of the control, nd lthough not significnt, those with the SSB-L tretment were greter thn tht of the control (Fig. 2e). The en root sored significntly greter Zn with % nd 75% rtes, nd not significntly ut greter Zn with % nd 25% rtes, compred with tht of the control, respectively. Cdmium in the spinch root ws significntly higher with SSB- H 75% rte thn those t other rtes, ut Cd with the SSB-L tretment ws lower thn tht of the control (Fig. 2f). The Cu in the en root ws significntly lower with % rte nd higher with % rte compred to other rtes, respectively. () 5 (d) () (c) 2. Cu (mg kg -1 ) Zn (mg kg -1 ) Cd (mg kg -1 ) C C B B B B B c B B B c B B B (e) (f) B B B C c C C B B C C Spinch Ben Spinch Ben Figure 2. Totl concentrtions of () Cu, () Zn, nd (c) Cd in the shoot nd (d) Cu, (e) Zn, nd (f) Cd in the root of Jpnese mustrd spinch nd common en with different ppliction rtes of sewge sludge iochr pyrolysed t high (SSB-H) nd low (SSB-L) tempertures. Different letters denote significnt differences y Fisher test (p<.5) mong different ppliction rtes for ech plnt nd SSB, respectively. ny of Cu, Zn, nd Cd in the sheth ws not significntly ffected y either ppliction of SSB- H or SSB-L compred with tht of the control, respectively, except for Cd with % nd 5% rtes eing significntly higher thn tht of the control (Tle 2).

9 46 Soil Processes nd Current Trends in Qulity ssessment () 5 4 Cu (mg kg -1 ) () 5 4 Zn (mg kg -1 ) (c).4 Cd (mg kg -1 ) Spinch Ben Figure 3. Totl concentrtions of () Cu, () Zn, nd (c) Cd in the iochr fter the pot study with different ppliction rtes of sewge sludge iochr pyrolysed t high (SSB-H) nd low (SSB-L) tempertures. Different letters denote significnt differences y Fisher test (p<.5) mong different ppliction rtes for ech plnt nd SSB, respectively Totl hevy metl concentrtions in the iochr fter the pot study The totl Cu concentrtion in the SSB-H fter the pot study ws not significntly ffected for the spinch ut significntly incresed with % rte for the en (Fig. 3). The totl Cu concentrtions in the SSB-L were not significntly ffected y the ppliction rte for oth plnts. fter hrvest of the spinch the totl Zn in the iochr ws not ffected y the ppliction rte for oth SSBs, ut t the en s hrvest only % rte cused significntly

10 Lechility nd Vegetle sorption of Hevy Metls from Sewge Sludge Biochr 47 higher totl Zn mong the SSB-H tretment (Fig. 3). The totl Cd in the iochr did not significntly chnge mong ech of the SSB rtes nd plnts, respectively, except for tht with % rte with the spinch eing significntly greter thn other SSB-H rtes (Fig. 3c) Totl hevy metl concentrtions in the soil fter the pot study The totl Cu concentrtion in the soil fter the pot study ws significntly incresed only with % rte mong the SSB-H tretment for oth plnts, respectively, ut not ffected mong the SSB-L tretment for oth plnts (Fig. 4). The totl Zn in the soil tended to increse with the SSB-H ppliction rte nd ws significntly greter with % rte compred with those with other rtes (Fig. 4). The totl Zn in the soil ws not significntly different mong the SSB-L tretments for oth plnts. The totl Cd in the soil ws significntly incresed with % nd 5% rtes for the spinch, ut not ffected for the en (Fig. 4c). The totl Cd in the soil with the SSB-L tretment significntly incresed compred with tht of the control for oth plnts, respectively. () 25 Cu (mg kg -1 ) (d) B c B () Zn (mg kg -1 ) (c) c B BC C B B B. (e) (f).4.3 c B B B C c B B B B Cd (mg kg -1 ) Spinch Ben Spinch Ben Figure 4. Totl concentrtions of () Cu, () Zn, nd (c) Cd nd dilute cid (.1M HCl)- extrctle (d) Cu, (e) Zn, nd (f) Cd in the soil fter the pot study with different ppliction rtes of sewge sludge iochr pyrolysed t high (SSB-H) nd low (SSB-L) tempertures. Different letters denote significnt differences y Fisher test (p<.5) mong different ppliction rtes for ech plnt nd SSB, respectively.

11 48 Soil Processes nd Current Trends in Qulity ssessment 3.6. cid-extrctle hevy metl concentrtions in the soil fter the pot study The dilute cid (.1 M HCl)-extrctle Cu in the soil fter the pot study tended to increse with incresing SSB-H ppliction rte for oth plnts, respectively, nd those with 75% for spinch, nd 5% nd 75% for en were significntly greter thn those with lower rtes, respectively (Fig. 4d). The HCl-Cu with % for spinch nd % for en ws significntly lower nd higher, respectively, thn those with other rtes. Similrly, the HCl- Zn with % rte for spinch nd % nd 75% rtes for en were significntly greter thn those with other rtes, respectively (Fig. 4e). The HCl-Zn with % nd 25% were significntly greter thn those with other rtes for spinch, nd tht with % rte ws significntly greter thn those with other rtes for en. The HCl-Cd with % rte ws significntly higher thn those with other rtes for spinch, nd tht with % rte ws significntly lower thn those with other rtes for en (Fig. 4f). The HCl-Cd with % ws greter compred with those with other rtes for spinch, ut there were no significnt differences mong the SSB-L tretment for en. 4. Results nd discussion 4.1. Hevy metl concentrtions in the soil nd iochr It ppers tht the ndisol used in this study contined less ut comprle totl Cu nd Zn, nd greter totl Cd concentrtions compred with the concentrtion rnge in similr soils of Jpn. The concentrtions of ndisols smpled in surrounded sures of Tokyo rnged from 97 nd 14 with the verge of 118 mg Cu kg 1, from 121 nd 175 with the verge of 143 mg Zn kg 1, nd from.37 nd.55 with the verge of.44 mg Cd kg 1 (Tershim et l., 24). Some hevy metls including Cu, Zn, nd Cd hve tendency of eing retined thus ccumulted in soils given eing reltively immoile fter wethering in the soil (Tershim et l., 24). High concentrtions of some hevy metls including Cd, Hg, P, nd S were oserved ecuse of possile rtificil interventions especilly in suur res of Tokyo (Tershim et l., 27). In fct, the re where the ndisol used in this study ws smpled ws former forest converted to plnttion re for mulerry (Morus l L.) tree. The conversion nd mintennce processes of the plnttion could hve involved some rtificil interferences tht might involve Cd deposition to the re. Mny properties including hevy metl concentrtions in SSB widely vry primrily depending on those contined in the feedstock (Chn & Xu, 29). n SSB pyrolysed t 8 o C from sewge sludge in Kyoto, Jpn contined 1,1 mg Cu kg 1, 1,63 mg Zn kg 1, 4 mg Cd kg 1 (Kwno et l., 212), while one pyrolysed t 5 o C using sewge sludge in Mdrid, Spin contined 222 mg Cu kg 1, 1,25 mg Zn kg 1, 1.79 mg Cd kg 1 (Pz-Ferreiro et l., 212). It seems tht oth SSB used in this study fll in the low end of concentrtion rnges for Cu, Zn, nd Cd in the SSB found in the literture. Prticulrly, Zn concentrtions in oth SSBs were exceptionlly lower thn those in the literture. The hevy metl concentrtion in the SSB ppers to ccumulte s the pyrolysis temperture increses (Hossin et l., 211), to which the SSB used in this study followed similr pttern.

12 Lechility nd Vegetle sorption of Hevy Metls from Sewge Sludge Biochr Effect of iochr on plnt growth The DW of spinch shoot nd root nd en root significntly decresed with incresing rtes of SSB-H due minly to lck of soil volume in the pot. In fct, chlorosis due to N deficiency ws oserved with the SSB-H tretment nd more pronounced on leves of oth plnts with higher SSB-H rtes. lthough the plnt ws fertilized, it ppered tht the lck of soil volume in the pot with high SSB-H rtes limited plnt root growth thus the plnt growth. In ddition, lthough the concentrtion ws not mesured in soil or plnts, oth plnts with the SSB-L tretment showed leve curvture due possily to excess uptke of oron. When SSB-L ws pplied, however, the shoot of oth plnts grew more thn tht of the control nd their DW peked t 5% rte for spinch nd 15% for en. similr trend ws oserved when egoni (Begoni semperflorens) ws grown on n ndisol mixed with SSB pyrolysed t 8 o C resulting in the DW pek with 25% rte (v/v) (Kwno et l., 212). In Kwno s study, the effect of SSB ppliction on the plnt growth ws most pronounced on most infertile sndy Entisol (Typic Udipsmments) mong tested soils with the highest SSB ppliction. It ppers tht the positive effect of SSB ppliction to soil on the plnt my e more prominent in soils which re less fvorle for plnt growth (Kwno et l., 212). On the other hnd, when n SSB pyrolysed t 7 o C ws pplied to volcnic sh soil from Knto re, Jpn with % (control), 3%, 5%, nd 1% (v/v) ppliction rtes to grow common en, the DW t hrvest with ech tretment ws in the order of control<1%<3%<5% (2.2, 3.6, 4. times of control, respectively), nd rhizoi with ll SSB tretments developed more thn tht with control (Ternum & Mori, 22). It ppers tht the optimum ppliction rtes of SSB for mximum plnt growth widely depend on vrying properties of soil, SSB, nd plnt, on which requires further investigtions Plnt sorption of hevy metl Some hevy metls such s Zn, Cu, nd Ni re importnt for proper functioning of iologicl systems nd deficiency or excess cn led to numer of disorders (Wrd, 1995), while others such s Cd re dngerous pollutnt due to their high toxicity to plnts nd inhiit growth t high sorption (Liu et l., 26). The rnge of hevy metl concentrtions sored in oth shoot nd root of the plnts ws in the order of Cd<Cu<Zn, respectively, in this study. The sme order of the concentrtion rnge of hevy metls ws oserved in vrious vegetle crops including similr plnts used in this study s spinch (mrnthus cudtus), lettuce (Lctuc stive), nd pes (Pisum stivum L.) (Uwh et l, 211; Singh et l., 212). The concentrtions of Cu, Zn, nd Cd in helthy plnts cn rnge 4 15, , nd.2.8 mg kg 1, respectively (Ntionl Institute for gro-environmentl Sciences, 1977). The totl Cu nd Zn concentrtions in the shoot of oth plnts in this study my hve fllen in sfe concentrtion rnges, respectively, wheres the totl Cd my hve een in excess sorption rnge which my hve cused inhiition of the plnt growth. In fct, the DW of the shoot of the plnts showed inverse reltionships with the totl concentrtions of the hevy metls sored in the plnts shoot, except for the en DW under the SSB-L tretment with the totl Cd (Tle 3). The inhiitive effect of hevy metl sorption on the plnt growth, judged y the slope of the correltion eqution, ws in the order of Zn<Cu<Cd for oth plnts nd oth SSB types, respectively.

13 41 Soil Processes nd Current Trends in Qulity ssessment Prticulrly, the correltion coefficient ws highest for Cd mong the hevy metls with the SSB-H tretment for the spinch (.719). similr trend ws oserved when hevy metls effectiveness in producing oxidtive dmge on spinch, ssessed y the mnifesttion of externl visul toxicity effects, ws in the order of Zn<Cu<Cd (Pndey et l., 29). Interestingly, however, the en shoot showed Cd tolernce to some degree with the SSB-L tretment in this study (its correltion coefficient ws positive). Plnt/SSB Equtions Coefficients Spinch/SSB-H (DW) =.97*(Cu) (DW) =.15*(Zn) (DW) =.443*(Cd) Spinch/SSB-L (DW) =.76*(Cu) (DW) =.8*(Zn) (DW) =.129*(Cd) Ben/SSB-H (DW) =.8*(Cu) (DW) =.1*(Zn) (DW) =.22*(Cd) Ben/SSB-L (DW) =.53*(Cu) (DW) =.6*(Zn) (DW) =.151*(Cd) Tle 3. Correltion equtions nd coefficients etween the dry weight (DW) nd totl concentrtions of Cu, Zn, nd Cd sored in the shoot of the plnts. Overll concentrtions of Cu, Zn, nd Cd in the root were greter thn those in the shoot of the plnts proly ecuse of root s chelting exudtes to soluilize hevy metls in the rhizosphere (In & Tkenk, 2) nd rpid sorption y the root nd slow trnsloction to shoot (Nd et l., 27). ccumultion of hevy metls (Cu, Zn, nd Cd) in spinch fter exposure to 5 µm supply of the metls ws greter in the root thn in the lef nd stem t the end of experiment (Pndey et l., 29). The rte of hevy metl sorption y the plnt cn e ffected y mny fctors of oth soil nd plnt such s soil ph, plnt ge, plnt species, nd nture of soil nd climte (llowy & yres, 1997; Uwh, 29). lthough not verified, the ppliction of cidic SSBs used in this study my hve decresed the neutrl ph of the soil during the pot study, which my hve enhnced plnt sorption of especilly Zn nd Cd, s commonly oserved irrespective of the vegetle crops nd soil types (Kuo et l., 1985; Xue & Hrrison, 1991). The effects of SSB ppliction on soil properties, hevy metl iovilility, nd plnt growth, therefore, need to e further evluted for the rnge of different soils nd plnts, nd over time ecuse hevy metl iovilility my increse over time in soil (Schuer et l., 198).

14 Lechility nd Vegetle sorption of Hevy Metls from Sewge Sludge Biochr Hevy metl lechility from iochr The totl concentrtions of Cu, Zn, nd Cd in SSB fter the pot study did not gretly vry mong the ppliction rtes within the sme SSB type nd plnt, respectively, nd 89 91%, 9 92%, nd 98 99% of the originl concentrtions of Cu, Zn, nd Cd were lost from the SSB during the pot study, respectively, regrdless of the SSB type, ppliction rte, nd plnt. While there re numerous studies tht del with sorption cpcity of iochrs for hevy metls when pplied to soil in light of phytoremedition perspective (Co et l., 29; Nmgy et l., 21; Uchimiy et l., 211), studies regrding on lechility (through desorption or dissolution) of hevy metls from iochr nd their iovilility re virtully nonexistent. The hevy metls, however, re known to e desored y nturlly occurring orgnic cids such s citric, oxlic, cetic, nd lctic cids (Nscimento, 26; Mrchi, 29) nd dissolved orgnic cron (ntonidis & llowy, 22) from soils mended with sewge sludge. Regrdless of equilirium mounts of Cd dsored in n ndisol, more thn 8% of Cd ws desored with one time extrction with citric cid if its concentrtion ws more thn.1 M, nd more thn 9% ws recovered if five soil pore volumes of.1 M citric cid were continuously run through the Cd-contminted soil (e et l., 24). n increse of dissolved orgnic mtter in soil y the ppliction of digested dewtered sludge significntly reduced the sorption of Cu on oth cidic sndy lom nd clcreous cly lom (Zhou & Wong, 21). The ppliction of SSBs in this study my hve incresed dissolved orgnic cron given the SSBs eing cidic, which my hve incresed Cu desorption (extrctility) thus lso iovilility. The hevy metls in the SSB used in this study my hve leched due to functions of vrious interctions etween soil nd plnt roots. Further studies re needed to clrify lechility nd iovilility of hevy metls from iochrs whose feedstock contin significnt mounts of hevy metls in order to elucidte hevy metl dynmics in soil upon the ppliction of such iochrs Hevy metl ccumultion nd vilility in soil The totl concentrtions of Cu nd Zn in the soil fter the pot study, regrdless of the tretment, were greter nd lmost equl compred with those of the originl soil (25 nd 43 mg kg 1, respectively), while oth concentrtions significntly incresed when SSB-H ws pplied t 75% rte for oth plnts. On the other hnd, the overll concentrtions of the totl Cd were smller fter the pot study compred with tht t pre-plnt condition (4.9 mg kg 1 ); however those with the SSB-L tretment incresed with incresing ppliction rte for oth plnts. Trnsfer fctors (TF) of hevy metl, s clculted s the rtio of the concentrtion of hevy metl sored in plnt to the concentrtion of hevy metl in soil, cn quntify the reltive differences in iovilility of hevy metls to vegetles or to identify the efficiency of vegetle species to ccumulte hevy metl (Uwh et l., 211). The TF vlues in this study, clculted sed on the sum of hevy metl concentrtions of the shoot nd root s the plnt concentrtion nd the sum of hevy metl concentrtions in the soil nd SSB s the soil concentrtion, were.77,.83, nd 1.37 for spinch, nd.69,.91, nd 1.19 for en for Cu, Zn, nd Cd, respectively, regrdless of the SSB ppliction rte. These TF vlues my explin why Cu ppered to hve een ccumulted in the soil (TF less thn 1 nd lowest mong the 3 metls for oth plnts), Zn seemed to hve hd no chnges efore nd fter the pot study

15 412 Soil Processes nd Current Trends in Qulity ssessment (TF close to 1), nd Cd ppered to hve een ccumulted more in the plnt thn in the soil (TF more thn 1). The TF vlues widely vry depending on properties of soils nd plnts, however, those clculted in this study my e comprle with those found y Uwh et l. (211), which were.25.95,.38.55, nd for Cu, Zn, nd Cd, respectively, for spinch nd lettuce grown on tropicl soils in Nigeri. Further studies re needed to elucidte hevy metl ccumultion in soil nd selective sorption y plnts with the SSB ppliction. The hevy metl concentrtions extrctle y.1 M HCl cid solution in the soil fter the pot study followed similr ptterns s the totl concentrtions in the soil. The Cu nd Zn concentrtions significntly incresed only when SSB-H ws pplied t 75% rte for oth plnts, while the Cd concentrtions did not show noteworthy differences mong the tretment. However, the percentge of the concentrtion of the cid-extrctle Cu, Zn, nd Cd to the totl concentrtion (cid solution extrctility) ws.3.8%, %, nd %, respectively. When 4 contminted nd 4 non-contminted soils from northern prt of Jpn were extrcted for hevy metls using.1 M HCl, the extrctility rnged 12% nd 27 33% for Cu, 9% nd 12 31% for Zn, nd 33% nd 73 92% for Cd in the contminted nd non-contminted soils, respectively (Kshem et l., 27). lthough the extrctility of hevy metls from soil y the dilute cid my vry depending on soil type, hevy metl, contmintion degrees, nd so on,.1 M HCl extrctnt my e the est choice for ssessment of moility or iovilility of hevy metls (Kshem et l., 27). The environmentl threshold concentrtions in soils re 125 mg Cu kg 1, 125 mg Zn kg 1, nd.1 mg Cd L 1 s.1 M HCl extrctle hevy metls, set y the Jpnese Environmentl Ministry. It seems tht neither of SSB types within the ppliction rtes nd study durtion used in this study hve cused environmentl threds to soils. Bsed on life cycle ssessment nlysis on different tretment processes of sewge sludge including neroic digestion, pyrolysis, nd incinertion, it ws concluded tht the most effective utiliztion of sewge sludge implied oth energy nd mteril reuse, nd tht the lnd ppliction of digested sludge ws n cceptle nd good choice s long s hevy metl contents in the finl cke could e minimized (Hospido et l., 25). Therefore, long-term effects of SSB ppliction on hevy metl dynmics mong SSBs, soils, nd plnts re needed to e evluted for further cceptnce of SSB ppliction in gronomic enefits. 5. Conclusions Biochrs derived from feedstock including hevy metls such s SSB need to e thoroughly evluted for hevy metl dynmics mong SSBs, soils, nd plnts for environmentlly sfe nd sound ppliction of SSB. Both SSBs used in this study contined low end of concentrtion rnges of Cu, Zn, nd Cd, respectively, found in the literture, nd the hevy metl concentrtions ccumulted in the SSB s the pyrolysis temperture incresed s found in the literture. Both spinch nd en plnts suffered from N deficiency due minly to lck of soil volume with excessively high ppliction of SSB-H, nd possily from B toxicity especilly from SSB-L ppliction. However, when SSB-L ws pplied, the shoot DW of plnts peked

16 Lechility nd Vegetle sorption of Hevy Metls from Sewge Sludge Biochr with 5% ppliction rte for spinch nd 15% rte for en. Therefore, it ws concluded tht the optimum ppliction rtes of SSB-H nd SSB-L were indeterminte (lower ppliction rtes of SSB-H need to e evluted) nd 5 15%, respectively, for the est growth of the plnts in this study. The concentrtion rnges of the hevy metls sored in oth plnts were in the order of Cd<Cu<Zn for oth shoot nd root. The totl Cu nd Zn in the shoot my hve een in sfe concentrtion rnges, nd the totl Cd my hve een in excess rnge which my hve cused inhiition of the growth. In fct, the plnt DW showed inverse reltionships with the totl concentrtions of the hevy metls sored in the plnts, nd the inhiitive effect of hevy metls on the plnt growth ws in the order of Zn<Cu<Cd. Overll concentrtions of the hevy metls in the root were greter thn those in the shoot for oth plnts. The lechility of Cu, Zn, nd Cd from SSBs ws 89 91%, 9 92%, nd 98 99% of the originl totl concentrtions, respectively, during the pot study regrdless of the SSB type, ppliction rte, nd plnt. However, the totl concentrtions of Cu, Zn, nd Cd in the soil fter the pot study were ccumulted, unffected, nd reduced, respectively, compred with those efore the pot study, which could e explined y the TF of ech hevy metl which were less thn 1, close to 1, nd more thn 1, respectively. Nevertheless, the percentge of the dilute cid-extrctle Cu, Zn, nd Cd to the totl concentrtions in the soil fter the pot study ws.3.8%, %, nd %, respectively, which were lower thn the environmentl threshold concentrtions in Jpn. However, long-term effects of SSB ppliction on hevy metl dynmics mong SSBs, soils, nd plnts re needed to e evluted for further cceptnce of SSB ppliction in gronomic enefits. uthor detils Mieko Ychigo nd Shinjiro Sto Deprtment of Environmentl Engineering for Symiosis, Sok University, Tokyo, Jpn References [1] e, Y, Ymguchi, N, Mizoguchi, M, Imoto, H, & Miyzki, T. (24). Effect of orgnic cid on trnsport of cdmium in soil, Proceedings for nnul Meeting of the Jpnese Society of Irrigtion Dringe nd Reclmtion Engineering, (in Jpnese), [2] llowy, B. J, & yers, D. C. (1997). Chemicl Principles for Environmentl Pollution, Blckie cdemic nd Professionl, London, UK., [3] ntonidis, V, & llowy, B. J. (22). The role of dissolved orgnic cron in the moility of Cd, Ni nd Zn in sewge sludge-mended soils, Environmentl Pollution, 117,

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