Effect of fresh and mature organic amendments on the phytoremediation of technosols contaminated with high concentrations of trace elements

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1 Effect of fresh nd mture orgnic mendments on the phytoremedition of technosols contminted with high concentrtions of trce elements Nour Httb, Mikel Motelic-Heino, Olivier Fure, Jen Luc Bouchrdon To cite this version: Nour Httb, Mikel Motelic-Heino, Olivier Fure, Jen Luc Bouchrdon. Effect of fresh nd mture orgnic mendments on the phytoremedition of technosols contminted with high concentrtions of trce elements. Journl of Environmentl Mngement, Elsevier, 2015, 159, pp < /j.jenvmn >. <insu > HAL Id: insu Submitted on 18 Mr 2016 HAL is multi-disciplinry open ccess rchive for the deposit nd dissemintion of scientific reserch documents, whether they re published or not. The documents my come from teching nd reserch institutions in Frnce or brod, or from public or privte reserch centers. L rchive ouverte pluridisciplinire HAL, est destinée u dépôt et à l diffusion de documents scientifiques de niveu recherche, publiés ou non, émnnt des étblissements d enseignement et de recherche frnçis ou étrngers, des lbortoires publics ou privés.

2 Effect of fresh nd mture orgnic mendments on the phytoremedition of technosols contminted with high concentrtions of trce elements Nour HATTAB,b*, Mikel MOTELICA-HEINO, Olivier FAURE c nd Jen-Luc BOUCHARDON c ISTO, UMR CNRS/Université d Orléns, Cmpus Géosciences, 1A, rue de l Férollerie, Orléns cedex 2, Frnce. E-mil : nour.httb@univ-orlens.fr b Université d Orléns, UFR-Fculté des Sciences, Lbortoire de Biologie des Ligneux et des Grndes Cultures, UPRES EA 1207, rue de Chrtres, BP 6759, F Orléns Cedex 02, Frnce. c Ecole Ntionle Supérieure des Mines de Sint-Etienne, Déprtement SPIN, Lbortoire GéoSciences & Environnement, 158 cours Furiel, F-42023, Sint Etienne Cedex 2, Frnce Abstrct Orgnic compounds resulting from the decomposition of orgnic mendments re used in the remedition of trce element (TE) contminted soils. The mobility, phytovilbility nd soil exposure intensity of molybdenum (Mo), chromium (Cr), zinc (Zn), copper (Cu), Coblt (Co) nd Arsenic (As) were evluted in the phytoremedition of contminted technosols fter the ddition of two orgnic mtter types, fresh rmil chipped wood (RCW) nd composted sewge sludge (CSS). The experiment consisted of nine min tretment blocks: (A) 3X unmended soil (NE), (B) 3X soil mended with RCW nd (C) 3X soil mended with mture CSS. Totl dissolved TE concentrtions were determined in soil pore wter (SPW) smpled by Rhizon smplers. The soil exposure intensity ws ssessed by stndrd Chelex 100 DGT (diffusive grdient in thin films) probes. TE phytovilbility ws chrcterized by growing dwrf bens on potted soils nd nlyzing their folir TE concentrtions. The results of the present study indicte tht the ddition of fresh RCW nd CSS hs positive effect on contminted technosols. RCW decresed the mobility of ll the studied TE in the SPW, wheres CSS reduced the mobility of Mo, Cr nd Co, while it incresed the mobility of Zn, Cu nd As compred with the NE soil. 1

3 The Zn soil exposure intensity ssessed by DGT ws not significntly chnged by the ddition of RCW nd CSS, while the Cr soil exposure intensity ws significntly decresed fter RCW ddition compred with the soil treted with CSS nd the NE soil. In contrst Cu nd Co were non lbile in the three soils. Both RCW nd CSS decresed the folir concentrtion nd the minerl mss of Mo, Zn, Cr, As nd Co in the ben leves but incresed the folir Cu concentrtion. Key words: Soil contmintion, phytostbilistion, Trce elements, Orgnic mendment, Mobility, phytovilbility, soil exposure intensity 1. Introduction Among nthrosols, technosols nd hortic, nthrosols re considered to be the most exposed to pollution (Bulgriu et l., 2007; Thornton, 1991: Flore nd Muntenu, 2003, IUSS, 2006). The high concentrtion, distribution nd migrtion of TE in these soils represent n importnt environmentl problem due to the gret toxicity of these elements tht my cuse mjor perturbtions to soil ecosystems (Jmil et l., 2014; Allowy, 1995; Kbt-Pendis nd Pendis, 1992; Ross, 1994). In fct the high concentrtions of TE in the contminted nthrosols is more problemtic thn for other soils becuse most of the properties of these types of soil my chnge with time, mking their hndling more difficult (Kelly et l., 1996). Therefore to limit the solubility nd the biovilbility of metl(oid)s in contminted nthrosol specil soil-mngement techniques is required. Severl tretment techniques cn be used to remedite TE contminted soils. These techniques include physicl nd chemicl remedition, nd gro-ecologicl engineering methods such s phytoremedition (Chen et l., 1999; Chen et l., 2000, b). Conventionl soil reclmtion technologies such s dig nd dump, soil wshing, nd sieving re effective but destructive thus not sustinble in terms of consumption of rw mterils nd wste production (Ricevic et l., 2005; Dermont et l., 2008). In ddition, they re very expensive, prticulrly for lrge contminted sites. Less invsive, low-cost phytotechnologies such s phytostbiliztion, singly nd in combintion with in situ stbiliztion (i.e. ssisted phytostbiliztion), re potentil mngement options to restore the physicl, chemicl nd biologicl properties of TE contminted soils (Mench et l., 2

4 2000; Boln nd Durismy, 2003; Pérez de Mor et l., 2005; Ricevic et l., 2005; Kumpiene et l., 2006, 2008; Segur nd Rmos 2013). Severl minerl nd orgnic mendments cn improve phytostbiliztion nd the production of plnt by decresing the solubility, leching nd biovilbility of TE (Brown et l., 2004; Bst nd McGowen., 2004; Kumpiene et l., 2008; Mench et l., 2010; Angelov et l., 2013). The immobilizing effect of such mendments re thought to ct through vrious complex processes e.g. dsorption onto minerl surfces, formtion of stble compounds with orgnic lignds, surfce precipittion nd ion exchnge (Kumpiene et l., 2008; Ahmd et l., 2011). However, these processes re still not well understood nd the choice of prticulr mendment is often problemtic. Thus, cse studies ssessing the mobility nd biovilbility of TE in contminted soils mnged by ssisted phytostbiliztion re needed to better define the pros nd cons of such mngement options (Mench et l., 2010). Orgnic mtter (compost, mnure or vrious orgnic wstes) dditions to soil hve long been considered importnt in mintining the qulity of both nturl nd mnged soils, principlly becuse of their cpcity to provide nutrients to the soil s living orgnisms nd through their influence on the soil physicl properties. This influence on soil properties depends on severl fctors such s the quntity, type nd mturtion of the orgnic mtters pplied to the soil nd the soil properties. Moreover orgnic mendments my enhnce the soil fertility nd microbil ctivity, leding to the meliortion of the soil qulity s whole. These overll modifictions generlly decrese the mobility nd the biovilbility of TE, even if temporrily, nd thus promote the reestblishment of vegettion nd increse plnt growth (Cstldi nd Melis, 2004; Mdejón et l., 2006; Brnzini nd Zubillg, 2012). Nevertheless, the effect of orgnic mendments on the mobility nd the biovilbility of metl(loid)s depends on the nture of the orgnic mtter itself, its microbil degrdbility, its effects on soil chemicl nd physicl proprieties, s well s on the prticulr soil type nd metl(loid)s concerned (Wlker et l.., 2003, 2004; Angelov et l., 2013). However very few comprtive studies hve been performed so fr nd the choice of prticulr orgnic mendment in ssisted phytostbiliztion strtegies often remin empiricl. The min im of this work ws to ssess the effect of two different orgnic mendments (composted sewge sludge (CSS) nd fresh rmil chipped wood (RCW)) on the mobility, phytovilbility nd soil exposure intensity of severl TE in metllurgicl technosol remedited by ssisted phytostbiliztion. 3

5 2. Mterils nd methods 2.1. Site description nd experimentl design The studied site is metllurgicl lndfill (Industeel-Loire; N; 4 38 E) ner Lyon, Frnce. It is locted behind steel nd iron fctory which is still in ctivity. Site description nd experimentl design were previously reported in Httb et l, The min chemicl nd physicl properties nd the totl metl concentrtions mesured in the RCW nd CSS before being mixed with the technosol re given in tble 1. The min pedologicl chrcteristics of the soils studied (tken t 0-20 cm depth) re given in tble 2. Their totl metl concentrtions re given in tble 3. The verge concentrtion vlues of metls mesured in the soil were 5837 mg.kg _1 Cr, 620 mg.kg -1 Mo, 1464 mg.kg -1 Zn, 444 mg.kg -1 Cu nd 80 mg.kg _1 As (Tble 3). These TE concentrtions re well bove the limits of TE concentrtions mesured in nturl unpolluted French soils (Bize, 2000), which confirms the existence of very high polymetllic contmintion. Tble 1 Tble 2 Tble Assessment of TE (phyto)vilbility TE (phyto)vilbility in the studied soils ws ssessed using three different pproches: i/ the mesurement of growth inhibition nd TE ccumultion in Phseolus vulgris; ii/ the mesurement of metl concentrtion in the soil pore wter; nd iii/ the diffusive grdient in thin films (DGT) method to ssess the TE soil exposure intensity. 4

6 Growth inhibition nd TE ccumultion in Phseolus vulgris Soil smples were collected in My 2011, i.e 18 months fter ploughing nd soil enrichment with RCW nd CSS mendments. Ech soil smple (pprox. 3.0 kg) ws mde of six independent sub-smples (pprox. 0.5 kg) rndomly tken from the surfce soil (0 25 cm) t ech of the nine experimentl plots. The nine smples (3 x RCW, 3 x CSS nd 3 x NE) were sieved t 2 mm. One kilo of ech soil ws then plced in 1.5 L pots (15 cm D X 14 cm L), nd wtered up to 80% of the wter holding cpcity (WHC) with ddition of deionized wter. Four dwrf ben seeds (Phseolus vulgris L. cv. Contender) were then sown in ech pot nd cultivted under controlled conditions (16 h light/8 h drkness, 25 C/21 C, 150 μmol m -2 s -1, 65% reltive humidity (ISO, 2005)). The conditions of culture nd the digestion of primry ben leves (BL) hve been previously published in Httb et l. 2014b Extrction nd chrcteriztion of SPW Soil moisture smplers (model MOM, Rhizosphere Reserch Products, Wgeningen, The Netherlnds), herefter clled rhizons, were used to extrct the SPW from ech pot. Rhizons were clened with 5% HNO 3 nd crefully wshed with deionized wter before use. Three rhizons were plced t 45 in ech pot during potting. After 15 dys of ben culture, rhizons from ech pot were left under vcuum for 24 hours (Cttni et l., 2006) to collect the soil pore solution ( 30 ml per pot). Three liquots (3 ml) of the soil solution from ech pot were cidified with HNO 3 (finl concentrtion: 0.1 mol.l -1 ) for metl nlyses. Additionlly, three liquots (1.5 ml) were kept untreted for mesurements of dissolved orgnic crbon (DOC). The SPW solutions were stored t 4C until nlyses DGT mesurements The potentilly vilble TE concentrtions (C DGT ) or soil exposure intensity were determined using stndrd Chelex-100 cylindricl DGT units (DGT Reserch, Lncster, UK) with n ctive surfce re of 3.14 cm 2. These DGT devices (Zhng et l., 2001) consisted of Chelex 100 binding resin lyer nd polycrylmide diffusion gel lyer covered with 0.45 m filter membrne (Dvison et l., 2000; Ernstberger et l., 2002).. Two DGT probes were mnully inserted into the humid topsoil (80% RCW) of ech pot, just fter the ben hrvest. After 24 h period, metls ccumulted in the resin-gel lyer were extrcted by immersion for 24h in 1mL of 5% HNO 3. This solution ws further diluted 10 times before TE nlysis. 5

7 2.3. Mesurements of TE in ben extrcts, SPW nd DGT probes TE concentrtions were determined by HR-ICP-MS (Element 2, Thermo Fischer, Wlthm, USA) using Twinnbr cyclonic spry chmber nd Micromist nebulizer (Glss Expnsion, Melbourne, Austrli). The ccurcy nd precision of nlyses were checked by performing clibrtions with stndrd reference wter solution (1000 ppm, Fisher scientific). For the primry BL digests, six TE (As, Co, Cr, Cu, Mo nd Zn) were nlyzed. Four repeted mesurements were performed for ech digest, generting 36 test results (4 replictes x 9 digests). Totl TE concentrtions in leves were first determined on g TE/g DW (dry weight) bsis. In ddition, the minerl msses (expressed in g TE/pot) were clculted by multiplying the element concentrtion in leves by the totl DW of the hrvested mteril. For the SPW solutions extrcted with Rhizon smplers, the sme TE (As, Co, Cr, Cu, Mo nd Zn) were nlyzed. Results were expressed on g TE/L soil solution bsis. Lstly, for the TE extrcted with DGT probes, only Co, Cu, Cr nd Zn concentrtions were determined becuse of the selectivity of the chelex 100 resin. The totl mss of metl (M) ccumulted per unit re of the DGT probe over its deployment time (t) ws clculted s previously reported in Httb et l. 2014b Mesurements of totl nd dissolved orgnic crbon Totl orgnic crbon (TOC) in the soils studied ws determined using Rock-Evl 6 pprtus (Vinci Technologies; Espitlié et l. (1985, b) nd Lfrgue et l. (1998)). This instrument uses rmped temperture pyrolysis technique, where smll mount of mteril ( mg) is heted in n inert tmosphere (helium or nitrogen) nd combusted with ir, to mesure severl key geochemicl prmeters, including TOC. Mesurements of TOC were performed in smples tken from the potted soils, just before ben sowing, nd fter drying the soil t 105C nd milling it very finely to obtin homogeneous smples. Dissolved orgnic crbon (DOC) ws mesured in SPW collected with Rhizon smplers. Anlyses were performed with Shimdzu TOC 5000A crbon nlyzer. The ccurcy of the instrument ws checked by performing 6

8 clibrtion with stndrd reference solution of potssium hydrogen phthlte (KHP) t concentrtion of 1000 mg Crbon/L. Four repeted mesurements of DOC were performed for ech SPW solution Other mesurements The ph nd electric conductivity (EC) of the studied soils were mesured t the beginning of the experiment, before ben sowing. Mesures were performed in deionized wter with soil:wter rtio of 1:2.5 (S: W)(NF ISO 10390). ph nd EC were lso determined in the SPW solutions tken with Rhizon smplers. Additionlly, the concentrtions of mjor ctions (N +, K +, C 2+, nd NH + 4 ) nd nions (NO - 3, SO 2-4, nd Cl ) were determined by ion chromtogrphy (Dionex ICS-2000, Sunnyvle, CA), using CS16A column for ctions nd AS17 column for nions Sttisticl nlyses One-wy nlysis of vrince (ANOVA), followed by Tukey post hoc comprisons were performed on the totl dissolved SPW concentrtions, DGT concentrtions, R rtios, folir element concentrtions, folir minerl msses nd primry ben lef DW yields to evlute the influence of the tretment on TE (phyto)vilbility. Person correltion coefficients (liner regression) between soil, SPW nd plnt prmeters were lso clculted. Differences were considered sttisticlly significnt t p < All sttisticl nlyses were performed using the Sttistic V. 6 softwre (SttSoft). 3. Results 3.1. SPW chrcteristics Tble 4 shows the physico-chemicl chrcteristics of the soil (i.e. TOC) nd SPW (ph, DOC, EC nd the concentrtions of mjor ctions nd nions) determined for the treted (RCW nd CSS) nd the untreted subplots (NE) one yer fter the ddition of orgnic mendments. The tble presents the verge vlues nd stndrd devitions for the nine plots (3 replictes X 3 types of soil). The experiments revel tht the dditions of the orgnic mendments (RCW nd CSS) in the soils hve severl effects. 7

9 First the soil ph did not chnge significntly between the treted nd untreted soils (p > 0.05); it decresed slightly by 3% in the soil treted with RCW nd CSS compred to the untreted soil (NE). Similr results were found by Vc et l. (2011) who investigted the effect of CSS on the soil properties nd TE mobility. They found tht the ddition of CSS decresed the soil ph slightly by 3% compred with the control soil. Likewise Soumré et l. (2006) who studied the effect of RCW nd litter compost (LC) on contminted soil properties, found tht RCW decresed the soil ph slightly by 3% compred with the control soil. Secondly, the vlues of the DOC incresed by 2 nd 4 fold, the TOC by 2 nd 3.5 fold nd the EC by 1.8 nd 1.3 fold for the RCW nd CSS treted soils respectively compred with the untreted soil (NE). Vc et l. (2011) lso found tht the ddition of CSS to the soil incresed its soil orgnic mtter (SOM) content by 2 fold compred to the soil without mendments, while Soumré et l. (2006) found tht the ppliction of RCW to the soil incresed the quntity of SOM in the soil by 2 fold compred with the control soil. Brgto et l. (1998) investigted two types of orgnic mendment (dehydrted sludge nd sewge sludge compost (SSC)) on slty lom soil. They found tht the ppliction of dehydrted sludge nd SSC compost incresed the soil TOC-content (from 0.71 to 0.86 %; i.e. reltive increse of 21 %) compred with the control soil. Additionlly, soil mendments hd n impct on the ction nd nion concentrtions in the SPW. We cn note tht the ddition of the RCW nd CSS decresed the concentrtions of nions nd some ctions such s (Cl -, NO3 -, SO4 2-, PO4 3- ; N +, C +2 ), while it incresed the concentrtion of other ctions such s (Mg 2+, Fe 2+, Mn 2+ ) in comprison with the untreted soil. Tble SPW concentrtions of TE The most obvious feture of the studied subplots ws the high level of contmintion in the soil pore wter by vrious TE such s Mo, Zn, Cu, Cr, As nd Co (Fig. 1). The verge concentrtion of TE collected from the 9 SPW extrcted from the 9 potted contminted soils showed high effect of soil mendment on the TE concentrtions in the SPW. These concentrtions were often relted to the totl TE concentrtion in the soil. Their verge concentrtions in the treted nd untreted contminted soils (RCW, CSS nd NE) were s follows: 3.32 mg.l -1 of MO, µg.l -1 of Zn 8

10 , 41.1 µg.l -1 of Cr,43.0 µg.l -1 of Cu,15.5 µg.l -1 of As, nd 2.6 µg.l -1 of Co (Fig. 1). The vlues shown on figure 1 re the medin, 25%-75% nd the Min-Mx for (n=9). Orgnic mendments (RCW nd CSS) significntly ffected the Mo soil pore wter [Mo SPW] of the treted soils compred with untreted soil (P=0.02). RCW dded to the soil slightly decresed [Mo SPW] in the soil by (0.4%), wheres this decrese ws more significnt in the soil treted with CSS (36%) compred with the untreted soil (NE). Our results demonstrted tht CSS ws the best mendment to reduce [Mo SPW] in the contminted soils (fig.1.). Figure (1, b) shows tht the orgnic mendments hd two different significnt effects on the mobility of Zn in the soil. The ddition of RCW reduced Zn soil pore wter concentrtion [Zn spw ] by bout 57% compred with the untreted soil (from ±40.85 (µg.l -1 ) in the soil (NE) to 72.79±27.31 (µg.l -1 ) in the soil treted with RCW). In contrst the CSS hd n inverse effect on Zn mobility, incresing the concentrtion of mobile Zn compred to the untreted soil by 54% (from ±40.85 (µg.l -1 ) in the soil (NE) to ±33.78 (µg.l -1 ) in the soil treted with CSS). A very significnt correltion (r= 0.76, r= 0.71) ws observed between the DOC nd the TOC nd the SPW zinc concentrtion in the soil solution [Zn spw ] respectively. Figure (1, c) shows the effect of orgnic mendments on the Cu soil pore wter concentrtion [Cu spw ]. Orgnic mendments hd significnt effect on the mobility of Cu in the soil (p= ). RCW reduced [Cu spw ] by 4 fold compred with the untreted soil (NE), from 18.05±0.89 (µg. l -1 ) in the soil (NE), to 4.59±0.86 (µg. l -1 ) in the soil treted with RCW, wheres CSS incresed the mobile Cu concentrtion by 6 fold compred with the soil without mendment, from 18.05±0.89 (µg. L -1 ) in the soil (NE), to ±21.15 (µg. l -1 ) in the soil treted with (CSS). Additionlly we found tht totl Cu concentrtion mesured in the SPW [Cu spw ] ws highly relted to the totl orgnic mtter content of the soils ([Cu SPW ](µg.l -1 ) = * TOC(%), Correltion: r = ), nd dissolved orgnic mtter of the SPW ([Cu SPW ](µg. l -1 ) = * DOC (mg.l -1 ), Correltion: r = ). The effect of orgnic mendments (CSS nd RCW) on the mobility of Cr in the soil cn be clerly observed in figure (1, d). The orgnic mendments significntly reduced the Cr soil pore wter concentrtion [Cr spw ] in the treted soil by nerly 1.7 fold compred with the untreted soil (p= ). This reduction ws 39% for the soil mended with RCW (from 56.02±9.86 (µg.l -1 ) in the soil NE to 34.97±7.59 (µg.l -1 ) in the RCW soil), nd 42% for the soil mended with CSS (from 56.02±9.86 (µg.l -1 ) in the soil NE to 32.48±8.27 (µg.l -1 ) in the CSS soil). A good correltion ws 9

11 observed between the soil ph nd the [Cr spw ] (r=0.68), wheres DOC nd TOC vlues were significntly negtively correlted with the Cr SPW concentrtion (r = p=<0.05 nd r=-0.714, p=<0.05 respectively). Figure (1, e) shows the different effects of orgnic mendments on the As soil pore wter concentrtion [As spw ]. The ddition of RCW to the soil did not hve ny effect on the [As spw ] concentrtion 11.72±3.41 (µg.l -1 ) compred with the untreted soil (11.63±3.96 (µg.l -1 ), wheres the effect of CSS on the As concentrtion in the SPW compred to the soil treted with RCW nd NE soils ws significnt (p= ). Soil mended with CSS incresed the As mobility by 49.4% compred with the RCW soil nd by 50.2% compred with the NE soil: As concentrtion incresed from (11.63±3.96 (µg.l -1 ) of [As spw ] in the NE soil to 23.32±4.51 (µg.l -1 ) of [As spw ] in the soil treted with CSS. A very strong correltion ws observed between DOC nd TOC mesured in SPW nd in soil nd the [As spw ] concentrtion mesured in the SPW solutions; this correltion ws r = 0.82, p=<0.05 nd r=0.80, p<0.05 respectively. RCW nd CSS dded to the soil significntly ffected the Co soil pore wter concentrtion [Co spw ] in the treted soil nd untreted soil (p= 1.64E -11 ). The effect of RCW nd CSS dded to the soil on the mobility of Co in the soil ws similr to their impct on the mobility of Cu. Figure (1, f) shows tht the ddition of RCW to the contminted soil reduced [Co spw ] by 48% compred with the untreted soil NE (from 1.32±0.48 (µg.l -1 ) in the (NE) soil to 0.68± (µg.l -1 ) in the (RCW) soil). In contrst, CSS incresed the Co mobility by 82% compred to the (NE) soil, from 1.32±0.48 (µg.l -1 ) in the (NE) soil to 7.17±1.36 (µg.l -1 ) in the (CSS) soil. The SPW Co concentrtion shows very good correltion with both DOC nd TOC; this reltion ws very strong with DOC vlues (r = 0.89, p=<0.01), wheres it ws less strong with the TOC (r = 0.79, p=<0.05). Figure Soil exposure intensity of TE Soil mendment did not hve significnt effect on the soil exposure intensity of Zn in the treted soil compred with the soil (NE) (Tble 5) for either of the orgnic mendments. The R vlues clculted from the [Zn DGT ] divided by [Zn spw ] mesured in the untreted contminted soil (NE) nd the soil mended with CSS were lower thn tht 10

12 mesured in the soil mended with RCW (Tble 5). The increse in the (Zn R ) vlues in the three types of soil ws s follows: CSS< NE<RCW, where CSS hs the cpcity to reduce the (Zn R ) vlues by bout 60%, while the soil mended by RCW incresed it by 51% compred with the NE soil. The higher vlue in the soil mended with RCW my lso indicte higher vlues of vilble Zn during the first hours of deployment, due to higher initil mobiliztion flux from the solid phse (Zhng et l., 2001). The untreted soil (NE) provided the highest concentrtion of soluble Cr (56.02±9.86 µg.l -1 ) nd the highest concentrtion of vilble Cr; this contribution ws bout 2% of the SPW concentrtion of Cr. RCW nd CSS dded to the soil decresed the vilble concentrtion of [Cr DGT ] in the contminted soils compred with the untreted soil (NE) (Tble 5). RCW decresed significntly (p= ) the vilble Cr concentrtion by nerly 73%, reducing the vilble Cr concentrtion from 0.67±0.10 µg.l -1 in the soil without mendment (NE) to 0.18±0.03 µg.l -1 in the soil treted with RCW. In the soil mended with CSS, the vilble concentrtion of Cr ws slightly reduced by 9% compred with the control soil. The vilble concentrtions of Cr in the soil mended with CSS nd in the soil without mendment NE were bout 1.9 % nd 0.5% of the SPW concentrtion of Cr in these soils. Tble 5 lso presents the [Cr DGT]: [Cr spw ] rtio R (Cr R ) vlues for ll contminted nd uncontminted soils. The soil mended with RCW presented (Cr R ) vlues 56% lower thn tht in the NE soil, wheres the soil mended with CSS hd the highest (Cr R ) vlues (bout 3.8 nd 1.7 fold more thn tht in the RCW nd NE soils respectively). A strong negtive correltion ws observed between [Cr spw ] nd totl nd dissolved orgnic mtter in the soil nd solution r= -0.82, r= respectively, nd between [Cr DGT ] nd the electricl conductivity (EC) in the soil r= [Cr DGT ] lso showed good correltion with totl Cr in the soil r=0.68. We did not detect ny vilble concentrtion of Cu nd Co in the DGT used, thus the rtio clculted from the mobile nd vilble frction ws equl to zero (Tble 5). Tble 5 11

13 3.4. Biomss of primry BL nd TE phytovilbility Tble 6 shows the DW nd folir TE concentrtion of the BL grown on treted nd untreted contminted soils. The ben lef dry weight (BLDW) in the soil mended with CSS ws equl to tht of the untreted contminted soil, wheres the soil mended with RCW incresed the BLDW by 14% nd 15% compred to the CSS nd NE soils respectively (p=0.013). TE phytovilbility ws ssessed by mesuring TE concentrtions in the primry BL. The results presented in Tble 6 lso show tht RCW nd CSS dded to the contminted soil significntly decresed the concentrtion of Mo, Cr, As nd Co mesured in the BL compred with the soil without mendment (NE) (p<0.0001). This decrese S ws bout 2.4 nd 1.6 fold for Mo, 6 nd 3.8 fold for Cr, 2 nd 1.8 fold for As nd 1.5 nd 1.2 fold for Co respectively (e.g. Cr concentrtion decresed from 14.46±1.06 (mg.kg -1 ) in the NE soil to 2.35±0.11 (mg.kg -1 ) in the RCW soil nd to 3.82±0.52 (mg.kg -1 ) in the CSS soil). In contrst the Cu concentrtion in the BL incresed fter the ddition of RCW nd CSS to the soil, but this effect ws not significnt compred with the untreted soil s this increse ws bout 10% nd 6% respectively (from 14.56±0.21 (mg.kg -1 ) in the NE soil to 16.17±1.28 (mg.kg -1 ) in the soil mended with CSS). Additionlly the effect of RCW nd CSS on Zn concentrtion in the BL ws different from the other TE. RCW reduced the Zn concentrtion in the BL slightly by 7% wheres the ddition of CSS incresed the Zn concentrtion slightly by 6.5% compred to the untreted soil. A good correltion ws found between the folir Mo, As nd Cr concentrtion nd the soil ph mesured in these soils (r 0.7 nd p<0.05). Tble 6 Figure 2 shows the minerl msses of Mo, Zn, Cu, Cr, As nd Co in the primry BL (µg.plnt -1 ) clculted bsed on the folir element concentrtion (µg.kg -1 DW) nd lef biomss production (µg DW.pot -1 ). A higher significnt decrese (p<0.0001) ws found in the minerl msses of the Mo, Cr nd As metls in the treted soils (RCW nd CSS) compred with the untreted (NE) soil. This decrese in the Mo, Cr nd As minerl msses in plnts fter the ddition of RCW nd CSS ws s follows: 2.0 nd 1.6 fold for Mo, 5.2 nd 3.8 fold for Cr nd 1.7, nd 1.8 fold for As respectively. Orgnic mendments slightly decresed the Co minerl mss by 1.3 nd 1.2 fold fter the ddition of RCW nd CSS respectively. However the mendment effects were not significnt compred to the other TE. In contrst the effect of soil mendment on the Cu nd Zn minerl msses ws different: the ddition of RCW nd CSS incresed 12

14 the minerl mss of Cu by 22% nd 4% nd by 8% nd 6% for the Zn respectively compred with the untreted soil (NE). If only the effects of orgnic mendments on the minerl msses of TE re compred, we cn see tht the soil mended with RCW ws more ble thn CSS to reduce the minerl mss of Mo, Cr nd Co in the BL tissues. The RCW decresed the minerl mss of these TE in the BLDW by 19% for Mo, 27 % for Cr nd 10 % for Co compred with tht clculted in the soil mended with CSS. In contrst RCW ws more efficient thn CSS t incresing the minerl msses of Zn, Cu nd As by 2%, 18 nd 5% respectively. A strong positive correltion ws in fct found between the minerl msses of Mo, Cr, nd As except Cu nd the soil ph (r>0.7, p<0.05), wheres this correltion ws strongly negtive between the sme TE minerl msses nd the EC mesured of the SPW r > 0.8, p=<0.001 nd r=0.80,p<0.05 respectively. 4. Discussion Figure Mobility of TE All our results showed tht RCW dded to the contminted soil decresed the mobile frction of TE (Mo, Zn, Cu, Cr nd Co) in the SPW compred with the untreted soil (Tble 4). Munksgrd nd Lottermoser (2010) tested the effect of two mendments on metl mobility in metlcontminted soils from the Broken Hill mining center, Austrli. The first mendment ws Phosphte fertilizer (bovine bone mel, superphosphte, triple superphosphte, potssium orthophosphte) nd the second ws fresh orgnic mendment (pine brk (Pinus rdit)). The two mendments were pplied to two soils contminted with mining wste. The results showed tht the ddition of fertilizers nd/or pine brk to both soil types incresed wter extrctble metls nd metlloids concentrtions (As, Cd, Cu, Fe, Mn, Pb, Sb, Zn) compred with unmended soils. Composted orgnic wste mendments such s composted sewge sludge hve been shown to hve multiple benefits of improving vegettion estblishment, reducing compction, (Bernl et l., 2006), protecting ginst erosion (Crul, 1999; Whlen et l., 2003) nd binding metls (Song nd Greenwy, 2004). The rpid mobiliztion nd verticl trnsport of trce metls nd As ws lso consequence of dding this mteril to the soil (Beesley nd Dickinson, 2010; Beesley et l., 2010). 13

15 Clemente et l. (2006) reported tht fresh orgnic wste, such s municipl wste compost (MWC), is rich in soluble orgnic compounds which cn increse the mobility of Zn by 48% nd of Cu by 74% compred with the control soil shortly fter the ddition of these mterils to soil, nd tht this increse results from the formtion of soluble orgnometllic complexes. These results re confirmed by our finding tht the ddition of CSS to the soil incresed the mobile frction of Zn by 54% compred with the untreted soil. Smith (2009) reported tht the ddition of compost nd sewge sludge to griculturl nd other soils rises the soil content nd the vilbility of hevy metls for trnsfer into crop plnts. The vilbility in soil depends on the nture of the chemicl ssocition between metl nd the orgnic residul nd soil mtrix, the ph vlue of the soil, the concentrtion of the element in the compost nd the soil, nd the bility of the plnt to regulte the uptke of prticulr element. There is no evidence of incresed metl relese in vilble forms s orgnic mtter degrdes in soil once compost pplictions hve cesed. This is confirmed by our results (Tble 4) nd my explin the increse in the mobile Zn (54%), Cu (83%), Co (82%) nd As (49%) concentrtions in the SPW fter the ddition of CSS to the contminted soil compred with the untreted one. Additionlly we noticed tht the mobility of TE ws strongly relted to the dissolved nd totl orgnic crbon concentrtions mesured in the soil nd soil solution. Moreover, the composition of orgnic mendments cn chnge with time due to the decomposition of orgnic mtter by soil microorgnisms, with soluble orgno-metl complexes being relesed into soil solution (Hood nd Allowy, 1994; Kschl et l., 2002). Xi et l. (2005) tested the effect of vrying mendment rtes of compost on the mobility nd the leching potentil of TE in the soil. They found tht incresing compost rtes significntly incresed the extrctble frction of Cu nd Zn by 8 fold nd 7 fold respectively t 1 L.L -1 of compost compred with the soil without compost (0 L. L -1 ). This is confirmed by the present study where we found tht CSS dded to contminted soil incresed the mobile frction of Cu nd Zn by 6 nd 2.2 fold respectively compred with the soil without mendment. Beesley et l. (2010, 2014) found tht pplying mendments such s compost nd biochr mendments to multi-element contminted soils cn hve contrdictory effects on the mobility, biovilbility nd toxicity of specific elements, depending on the mendment. TE were mesured fter 60 dys in contminted soil mended with biochr nd green wste compost, fter phytotoxicity hd been ssessed by simple bio-indictor test. They found tht Cu nd As concentrtions in the SPW incresed more thn 30 fold fter dding both mendments, ssocited with significnt increses in dissolved orgnic crbon nd ph, wheres Zn nd Cd significntly decresed. Gigliotti et l. (1996) mesured the ccumultion of TE in the top 20 cm of clcreous soil mended with urbn wste compost. They reported tht compred with untreted soils, mended soils showed significnt increse 14

16 only in Cu, Zn, Pb nd, in the lst 2 yers, Cr concentrtions. They concluded tht the long-term ppliction of lrge mounts of urbn wste compost to CCO 3 -contining soils does not necessrily cuse medium-term problems to plnt, niml or humn helth. Two types of composts were tested s mulching mterils in vineyrd by Pinmonti, (1998): one ws sewge sludge nd brk (SB) compost with low trce element concentrtion, the other ws municipl solid wste (MSW) compost with higher concentrtion of metls. Both compost mulches meliorted soil properties; they incresed orgnic mtter content nd improved the porosity nd wter retention cpcity of the soil. The SB compost only cused significnt increse in totl nd DTPA-extrctble Zn in the soil; with this compost the soil concentrtions of the other trce elements exmined (Cu, Ni, Pb, Cd nd Cr) did not show ny significnt chnges. In contrst, the MSW compost, used over six-yer period, incresed concentrtions of totl Zn, Ni, Pb, Cd nd Cr nd of DTPA extrctble Zn, Ni, Pb nd Cd in the soil when compred to the control. Co et l. (2003) investigted the effects of phosphte rock, municipl solid wste nd Biosolids (BS) on the leching of As from soils nd As uptke by Chinese brke fern in chromted copper rsente (CCA) contminted soil or in As spiked contminted (ASC) soil. They found tht As uptke in the compost-treted CCA soil ws relted to the increse of soil wter-soluble As nd As(V) trnsformtion into As(III). Reduced As uptke in the ASC soil my be ttributed to As dsorption to the compost. Compost nd phosphte mendments incresed As leching from the CCA soil by 34% nd 26% compred with the control soil, but decresed leching with the presence of n As ccumultor (Chinese brke fern (Pteris vittt L)). These results confirm the effect of CSS which incresed the mobile concentrtion of As by 49% compred with the untreted soil. The ecologicl effects of metls nd metlloids in soils re closely relted to the concentrtion nd specition of the elements in the soil nd soil pore wter (Bruemmer et l., 1986). Generlly the plnt exposure to metls is relted to the concentrtions of both mobile nd vilble trce metls in SPW (Suvé et l., 1997; Suvé, 2003; Tndy et l., 2006; Forsberg et l., 2009; Httb et l., 2014b). Orgnic mtter dditions to soil hve long been considered importnt in mintining the qulity of both nturl nd mnged soils. When RCW decomposes on soil, stble nd enduring humus is creted. The lignins in the RCW re slowly broken down by nturlly occurring fungi, nd these fungi lso ply vitl role in the soil food web, serving s nourishment for microorgnisms (bcteri, fungi, nd soil fun), which rpidly invde the RCW ccording to specific stges of succession (Käärik, 1974). The second orgnic mtter which we used, composted sewge sludge (CSS), provides more mture soil orgnic mtter thn RCW. 15

17 The mjority of trils showed higher SOM effects on soil properties especilly with composted mteril. Whtever the crbon source (strw, mnure, compost), it hs significnt impct on soil properties. However, well mtured compost leds to higher SOM increse thn fresh compost. The stble C frction responsible for OM reproduction is higher in mture compost (50% of totl compost C). This increse in soil orgnic mtter results from the increse in the mount of orgnic mtter nd the biologicl ctivity present within the soil due to the fresh pool of orgnic substrte. SOM hs probbly the gretest cpcity nd strength of bonding with most trce metls of ny soil component (the possible exceptions re some non-crystlline minerls with very high surfce res). As result, there re often sttisticlly significnt correltions between solubility of trce metls such s Cu, Hg nd Cd, nd soil orgnic mtter content. Generlly the metls tht bond most strongly to SOM tend lso to be the most rpidly dsorbed. When these metls such s Pb 3+, Cd 2+, Cu 2+ nd Fe 3+ form complexes with soil orgnic mtter their lbility decreses. In contrst when some trce elements such s Cu 2+, Ni 2+ nd Co 2+ form cid-metl complexes with dissolved humic nd fulvic cid, they pper to be lrgely lbile. This lbility is controlled by the soil ph nd the metl/orgnic rtio, which decreses with incresing ph nd with decresing metl/orgnic rtio (Petruzzelli nd Pezzross, 2003; Leit et l., 2003; Sherene, 2010) Phytovilbility of TE Orgnic mendments dded to the soil (RCW nd CSS) reduced Mo, Cr, As nd Co concentrtions in the bens grown in treted soil compred to the untreted soil. The concentrtions of mny TE exceeded the limit vlues reported by (Kbt-Pendis nd Pendis, 2000) for folir Cu, Cr, As nd Zn, i.e. 20, 5, 5 nd 100 mg. kg -1 DW respectively, nd those reported by McNicol nd Beckett (1985), nmely µg Cu g _1 DW, < 1 µg Cr g _1 DW, µg Zn g _1 DW nd 1-4 µg As g _1 DW. The ddition of fresh orgnic mteril (RCW) to the soil decresed the mobility of Zn, Cr, Cu nd Co mesured in the soil solutions (Fig. 1) nd the TE concentrtions of (Mo, Cr, Zn, As nd Co) mesured in the BL, except for Cu (Tble 5). Angelov et l. (2010) investigted the effect of severl orgnic mendments (pet, compost nd vermin compost) on the quntity of mobile forms of Pb, Zn, Cd nd Cu nd the uptke of these elements by potto (Solnum tuberosum L.) plnts. They concluded tht the ppliction of soil mendments fvors plnt growth nd its development which is confirmed by our results in the cse of CSS wheres RCW showed no effect; these effects were best expressed with the ppliction of 10% compost (5% in our experience). They lso found tht orgnic mendment ppliction led to n 16

18 effective immobiliztion of Pb, Cu, Zn nd Cd phytovilble forms in soil nd decresed the trce metl content in the potto peel nd tubers. This grees with wht we found fter RCW ddition except for Cu, nd except for Cu nd Zn fter CSS ddition. Gigliotti et l. (1996) investigted the effects of soil mended with urbn wste compost on the uptke nd distribution of TE (Cd, Cu, Ni, Pb, Zn nd Cr) in corn plnts grown in this soil. They reported tht the corn plnts grown on the mended soil showed generl increse in metl uptke, which ws bout three times greter for Pb nd two times greter for the other metls thn in plnts grown on untreted soil. They lso found Cu nd Zn in ll plnt prts nd lthough the quntity bsorbed by the plnts from the treted plots ws higher, their distribution ws uniform in ll plnts. These results gree with the effect of CSS dded to our soil concerning Cu nd Zn concentrtion in the ben leves, which incresed by bout 6 nd 6.5 % compred with the control soil. Businelli et l. (1996) investigted the effect of two types of compost (MWC) on the mobility nd the vilbility of (Cu, Pb, Zn, Cd, Cr nd Ni) in n rgillceous lom clcreous soil for 6 yers. They found tht mendments significntly incresed the mobile TE concentrtions in the treted soil compred with the untreted one. Cu, Pb, nd Zn concentrtions mesured in the plnts grown on the mended soil were generlly higher thn those mesured in the control soil. This ws not however the cse for Cd, Cr nd Ni mesured in the treted soil. Our results fully confirm these findings on the effects of CSS, which incresed Cu nd Zn concentrtion in the BL, wheres it decresed the Cr concentrtion by 3.8 fold compred with the untreted soil. Bes nd Mench (2008) dded five types of orgnic mtter (three phosphte compounds, zerovlent iron grit (ZVIG, 2% by soil weight), two lkline compounds, nd two commercil formultions) singly nd some combined with ZVIG, to highly Cucontminted topsoil (2600 mg Cu kg -1 ) from wood tretment fcility. They found tht the mjority of mendments enhnced the growth of bens in treted soils compred to the untreted one. They lso reported tht CSS nd Compost poultry mnure (CPM) dded to the contminted soil incresed the quntity of the biomsses by bout 1.5 fold nd 1.4 fold respectively compred with the untreted soil. In our experiment CSS did not hve ny effect on the biomss of the BL compred with the untreted soil, wheres RWC incresed the BL biomss slightly by 1.2 fold compred with the untreted soil. Cu nd Zn concentrtions mesured in the BL decresed by 1.5 nd 2 fold respectively, while we found tht the ddition of CSS to our contminted soil incresed the concentrtion of Cu nd Zn by 6 nd 6.5 fold compred with the untreted soil. However the soil type nd Cu concentrtion rnge used by Bes nd Mench were very different from our study. Bes nd Mench (2008) reported tht the Cu minerl mss [Cu MM ] incresed in the soil mended with CSS nd mixture of Compost poultry mnure nd zerovlent iron grit (CPMX ZVIG), wheres our results showed tht there ws no significnt effect of mendment on the minerl msses of Cu in the ben leves. Cstldi nd Melis (2004) 17

19 reported tht orgnic mendments (compost) contin high proportion of humified orgnic mtter, which could decrese the TE biovilbility in soil, thus reducing its toxicity for vegettion. The ddition of fresh orgnic mteril is usully ssocited with the rrivl of lrge number of microorgnisms nd mcroorgnisms in the soil. Interctions between microorgnisms nd metls re multiple: ccumultion, intrcellulr, metl/ cell wll combintion, extrcellulr polymeric / metl interction, etc. These rections cn led in theory to immobiliztion or remobiliztion of the trce elements in the soil under certin environmentl conditions (Ford nd Mitchell, 1993). The bcteri in soil possess surfces tht interct strongly with metl ions in soil solution, which could dsorb greter mount of hevy metls thn inorgnic soil components such s montmorillonite, kolinite or vermiculite (Ledin et l., 1996), since bcteril cells (pproximtely 1.0e1.5 mm3) hve n extremely high rtio of surfce re to volume, which endows bcteri with strong for dsorbing nd immobilizing toxic ions from soil solution (Beveridge nd Schultze-Lm, 1995). 5. Conclusion First, the mobility of TE ws ssessed by investigting the totl dissolved concentrtions of TE in the SPW of the mended nd control soils. Totl dissolved TE concentrtions were determined in soil pore wter (SPW) smpled by Rhizon smplers. The verge results of ech of the 3 plots showed tht RCW significntly reduced the Mo, Zn, Cu, Cr nd Co dissolved concentrtions in the SPW wheres it did not hve ny effect on the As concentrtion. In contrst the ppliction of CSS significntly incresed the dissolved concentrtions of Zn, Cu, Co nd As in the SPW while it decresed the concentrtions of Mo nd Cr. Thus RCW decresed the mobility of ll the studied TE in the SPW, wheres CSS reduced the mobility of Mo, Cr nd Co, while it incresed the mobility of Zn, Cu nd As. Second, the soil exposure intensity ws ssessed by DGT probes. The Zn soil exposure intensity ssessed by DGT ws not significntly chnged by the ddition of RCW nd CSS, while the Cr soil exposure intensity significntly decresed fter RCW ddition compred with the soil treted with CSS nd the NE soil. Cu nd Co could not be detected by DGT in our three soils, suggesting tht these TE were non lbile. Third, the TE phytovilbility ws chrcterized by growing dwrf bens on potted soils nd nlyzing their folir TE concentrtions. The effect of orgnic mendments on the TE concentrtion in the ben leves ws very mrked: we found tht the soil mended with RCW provided ben lef dry weight higher thn tht of the other soils nd tht RCW ws ble to reduce Mo, Zn, Cr, As nd Co concentrtion in the ben leves compred with the NE soil. RCW ws lso more efficient thn CSS t reducing the minerl mss of Mo, Cr nd Co in the ben lef tissues. In contrst, CSS ws more ble thn RCW to increse the minerl msses of Zn nd Cu 18

20 in the ben leves. Consequently, RCW ws more effective thn CSS t reducing TE mobility nd phytovilbility in the contminted technosols. Acknowledgements The uthors grtefully cknowledge the Agence de l Environnement et de l Mîtrise de l Energie (ADEME), Dept. Polluted Sites & Soils, Angers, Frnce for its finncil support ( Physfimm progrm). References Ahmd, H.R., Ghfoor, A., Corwin, D.L., Aziz, M.A., Sifullh, S.M., Orgnic nd inorgnic mendments ffect soil concentrtion nd ccumultion of cdmium nd led in whet in clcreous lkline soils. Commun Soil Sci Plnt Anl 42: Allowy, B.J., Hevy Metls in Soils (2nd ed.), Blckie Acdemic Professionl, London, U.K. Angelov, V. R., V. I. Akov, N. S. Artinov., K. I. Ivnov., The effect of orgnic mendments on soil chemicl chrcteristics. Bulg. J. Agric. Sci., 19: Angelov, V.A., Rdk Ivnov, B., Glin Pevichrov, C., Krsimir, I., Effect of orgnic mendments on hevy metls uptke by potto plnts. In: 19th World congress of soil science, soil solutions for chnging world, 1 6 August 2010, Brisbne, Austrli. Published on DVDBize, Teneurs totles en «métux lourds» dns les sols frnçis. Résultts générux du progrmme Aspitet. Le Courrier de l environnement de l INRA, 39, Bst, N.T., McGowen, S.L., Evlution of chemicl immobiliztion tretments for reducing hevy metl trnsport in smelter contminted soil. Environ Pollut. 127: Beesley, L., Dickinson, N.M., Crbon nd trce element mobility in n urbn soil mended with green wste compost. Journl of Soils nd Sediments 10, 215e222. Beesley, L., Inneh, O.S., Norton, G.J., Jimenez, E.M., Prdo, T., Clemente, R., Dwson, J.J.C., Assessing the influence of compost nd biochr mendments on the mobility nd toxicity of metls nd rsenic in nturlly contminted mine soil. Environ. Pollut. 186, Beesley, L., Moreno-Jimenez, E., Gomez-Eyles, J. L., Effects of biochr nd greenwste compost mendments on mobility, biovilbility nd toxicity of inorgnic nd orgnic contminnts in multi-element polluted soil. Environ. Pollut., 158, Bernl, M.P., Clemente, R., Wlker, D.J., The role of orgnic mendment in the bioremedition of hevy metl polluted soils. In: Gore, R.W. (Ed.), Environmentl Reserch t the Leding Edge. Nov Science, pp. 1e60. 19

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