Arsenic accumulation by ferns: a field survey in southern China

Transcription

1 Environ Geochem Helth DOI /s ORIGINAL PAPER Arsenic ccumultion y ferns: field survey in southern Chin Cho-Yng Wei Æ Cheng Wng Æ Xin Sun Æ Wu-Yi Wng Received: 6 Decemer 2005 / Accepted: 13 Mrch 2006 Ó Springer Science+Business Medi B.V Astrct The ojective of this study reported here ws to chrcterize rsenic (As) ccumultion y Pteris ferns y compring 3 of the ferns of this genus with ech other s well s with four non-pteris ferns growing on seven sites in southern Chin with different As levels. A totl of 112 smples, including 78 Pteris vittt, 13 P. cretic, 3P. multifid nd 18 ferns from other non-pteris gener, with the soils in which they grew were collected for As nd other elementl nlyses. P. vittt ws found to e the most dominnt species nd the most efficient As-ccumultor, wheres P. multifid ws the lowest As-ccumultor mong the Pteris ferns, with , nd mg kg 1 As recorded in the fronds of P. vittt, P. cretic nd P. multifid, respectively. Arsenic concentrtions in non-pteris ferns were generlly much lower thn those in Pteris ferns, with , 3.59, 10.7, mg kg 1 in the fronds of Blechumum orientle, Dicrnopteris dichotom, C.-Y. Wei (&) Æ C. Wng Æ X. Sun Æ W.-Y. Wng Institute of Geogrphicl Sciences nd Nturl Resources Reserch, Chinese Acdemy of Sciences, A11 Dtun Rod, Anwi, Choyng District, Beijing , Chin e-mil: weicy@igsnrr.c.cn C. Wng Æ X. Sun Grdute School of the Chinese Acdemy of Sciences, Beijing , Chin Pteridium quilinum nd Cyclosorus cumintus, respectively. For P. vittt, the As ioccumultion fctor (rtio of As in fronds to tht in soils) chnged, wheres the As trnsloction fctor (rtio of As in fronds to tht in roots) remined unchnged mong the different sites. The concentrtions of Fe were very high in ll of the collected fern smple, with the exception of B. orientle, with , , , 1876, nd 492 mg kg 1 in the fronds of P. vittt, P. cretic, P. multifid, C. cumintus, P. quilinum nd D. dichotom, respectively. The ssocition etween Fe ccumultion nd As ccumultion nd tolernce in these ferns indictes the unique role of Fe in As-hyperccumultion. Keywords Accumultion Æ Arsenic Æ Hyperccumultor Æ Iron Æ ph Æ soil Introduction Arsenic (As) hs een clssified s toxic nd crcinogenic element nd s such hs contriuted to numer of environmentl nd humn helth prolems worldwide, with the highest numer of cses hving een reported in South-Est Asin countries, minly Indi, Bngldesh nd Chin (Mndl nd Suzuki 2002). Drinking wter from wells locted in res with As-rich underground

2 Environ Geochem Helth sediments hs een shown to e the source of rsenocosis (Mndl et l. 1996; Ptel et l. 2005; Yng et l. 2002). It is estimted tht totl of 90 million people worldwide re t risk of As toxicity, with more thn 2 million of these eing in Chin (Nordstrom 2002). Metl mining nd smelting ctivities re dditionl sources of As toxicity nd cn led to As contmintion of the ir, wter nd soil (Andre et l. 2004; Cheng 2003). Lio (1989) reported rsenic concentrtions in vrious plnt types in Chin nd recorded levels of mg kg 1 in cerel crops, mg kg 1 in legumes, mg kg 1 in vegetles nd mg kg 1 in woody plnts. A numer of investigtors hve reported high levels of As in vrious plnts growing on As-contminted soils. For exmple, Porter nd Peterson (1975) reported tht Jsione montn, Cllun vulgris, Agrostis tenuis nd Agrostis stolonifer plnts collected from sites in the UK polluted with high levels of As contined 6640, 4130, 3470 nd 1350 mg kg 1 As, respectively. De Koe (1994) found tht Agrostis cstelln plnts growing in tilings from the gold mines in Portugl contined As levels of 1900 mg kg 1. A high As concentrtion ws reported y Bech et l. (1997) in plnts of the grss Psplum rcemosum, with the ded leves contining up to 5280 mg kg 1 As. The term metl hyperccumultor is term of reltivity nd is used to designte plnts tht re le to ccumulte more thn 100 times concentrtions of metls in their shoots thn non-hyperccumultors. For exmple, elevted concentrtions of metls hve een mesured in the shoots of the following hyperccumultors: Cd > 100 mg kg 1 ; Co, Cu, Ni nd P > 1000 mg kg )1 ; Mn nd Zn > 10,000 mg kg 1 (Bker 1989). Pteris vittt hs recently een identified s n As-hyperccumultor (Chen et l. 2002; M et l. 2001). Other species of ferns, including Pteris cretic nd Pityrogrmm clomelnos, hve lso een determined to e As-hyperccumultors nd show gret potentil in phytoremedition (Frncesconi et l. 2002; Visoottiviseth et l. 2002; Wei et l. 2002). In fct, these ferns hve een strongly put forwrd s good cndidtes for As phytoremedition (Chen et l. 2002; M et l. 2001; Visoottiviseth et l. 2002). Reserch hs focused on screening for dditionl possile As-hyperccumultors nd on the mechnisms relted to Ashypertolernce nd hyperccumultion (Bondd et l. 2004; Dun et l. 2005; Fitz et l. 2003; Mehrg 2003; Zhng et l. 2002; Zho et l. 2002). To dte, little knowledge is ville on the interction of As with other elements in As-hyperccumultors. Phosphte is known to ct s n ntgonist to rsente nd consequently suppresses As uptke in some As-tolernt plnts (Mehrg et l. 1994). An erly study y Porter nd Peterson (1977) reported tht cler correltion exists etween As nd Fe in plnts growing on soils hevily contminted with As, with the results indicting tht Fe plys role in As ccumultion in these plnts. Fitz et l. (2003) found high Fe concentrtion in soil solutions in the rhizosphere of P. vittt, suggesting the possile moiliztion of Fe y the roots of P. vittt. However, more studies re needed to explore the exct role of nutrient elements on the detoxifiction nd ccumultion of As in As-hyperccumultors. Since the As frctions in soils, especilly the ioville or/nd solule/exchngele frctions, re different etween the pot nd field, more informtion relted to As ccumultion chrcteristics under field conditions is needed in order to evlute the phytoremedition potentil of these plnts. The ojectives of the present study were: (1) to chrcterize As ccumultion in three Pteris ferns growing t different sites in southern Chin; (2) to ssess the possile influence of Fe nd other nutrient elements on As ccumultion in the ferns. The results should contriute to n understnding of As ccumultion in Pteris ferns under field conditions. Mterils nd methods Site description nd smpling The survey ws conducted t seven sites in southern Chin in April Arsenic ws present long with gold, mercury/thllium nd tin deposits t four sites, resulting in very high As levels in the soils (Tle 1). All of the smpling points t ech site were locted on hill slopes or hillsides, some distnce wy from mining,

3 Environ Geochem Helth Tle 1 Arsenic concentrtion in the fronds/roots of the ferns nd in the soils on which the ferns were growing Ferns smpled Smpling Loction Metl present Numer of sites with As smples Soil ph (Men SD) As (mg kg 1 ) (rnge) Fe (mg kg 1 ) (rnge) Soils Fronds Roots Fronds Roots Pteris vittt ZMD Zimudng, Xinren county, Guizhou province LMC Lnmuchng, Xinren county, Guizhou province Au Hg/Tl GJ Gejiu, Yunnn province Sn Au GT Getng, Anlong county, Guizhou province GZ Gungzhou, Gungdong province BS Bise, Gungxi province Pteris cretic GJ Sn ms 2151 ms ZMD SL Shilin, Yunnn province Pteris multifid ZMD ms ms GJ Sn ms 605 ms Cyclosorus cumintus ZMD Au Pteridium quilinum GT Dicrnopteris dichotom LMC Blechnum orientle BS GZ ms ms Zimudng (ZMD), Lnmuchng (LMC), Getng (GT), nd Gejiu (GJ), ll with high As levels; Bise (BS) nd Gungzhou (GZ), with low As levels Some ferns were not collected from the elts of metl deposits with high As levels; ms: missing smples

4 Environ Geochem Helth smelting nd griculturl ctivities, in order to reduce s much s possile the influences of nthropogenic As sources nd to determine the true properties of As ccumultion y these ferns. Ferns from the Pteris genus were collected t every smpling site. Additionlly, four selected gener of non-pteris ferns tht grew with undnt distriution t these sme sites were lso collected. Mture ferns with four to eight fronds (ove-ground prts) nd roots (elow-ground prts) were smpled. The smpling points t ech site were strictly kept t more thn 20 m from ech other to gurntee the representtion of ech smple. Approximtely 1 kg soil round the fern roots to depth of 20 cm ws collected for ech smple. Soil nd plnt nlysis Soil smples were ir-dried, the stonesnd plnt deris removed nd the smple sieved through 20-guge mesh (0.18 mm). A 10 g frction of the smples ws ground still finer to pss through 60-guge mesh (100 lm) for the nlysis of As forms in soils using the modified procedure of Chng nd Jckson (1957). The As in these finer soil smples ws sequentilly extrcted s ioville (F1), C-incorported (F2), Al-incorported (F3), Fe-incorported (F4) nd residul (F5). A second frction of the smples (pprox. 15 g) ws ground yet finer to pss through 100- guge mesh (150 lm) for the nlysis of As nd other elements. Fern smples were seprted into fronds nd roots, wshed thoroughly with flowing tp wter, rinsed three times in deionized wter, then dried in n oven t 70 C for 5 h. Extremely crefulness ws pid during the wshing processes to remove ll soil prticles tht dhered to roots nd to prevent the loss of ny tiny fern roots. Plnt smples were then powdered using n electric stinless steel miller nd homogenized. Soil nd plnt smples were digested with mixtures of 8:1 HNO 3 nd HClO 4 on n electric hot plte t 120 C. The presence of As in the soil nd fern smples ws determined using hydride genertion tomic fluorescence spectrometer (AFS830, Beijing Jitin Co., Chin). Phosphorus, K, N, C, Mg, Fe, Mn, Cu nd Zn in the ferns were determined y inductively coupled plsm tomic emission spectroscopy (ICP-AES). Stndrd soil nd plnt references (Center for Stndrd Reference of Chin) were used to check the ccurcy of the chemicl nlyses. Milli Q (18W) wter ws used throughout, nd the cid nd regents were ll super grde or higher. Sttistics The sttisticl nlysis of the dt ws done using the softwre pckge SPSS 10.0 (SPSS, Chicgo, Ill.). One-wy ANOVA with the Duncn test ws used for the nlysis the vrince of the ioccumultion fctor (BF; rtio of rsenic in fronds to soil) nd trnsloction fctor (TF; rtio of rsenic in fronds to roots) etween different sites. The Student s t-test ws employed to compre the concentrtion of As nd nutrient elements in the fronds of P. vittt etween the sites of Zimudng (ZMD), Lnmuchng (LMC), Getng (GT) nd Gejiu (GJ), with high As levels, nd Bise (BS), Gungzhou (GZ), with low As levels. Results The distriution of ferns nd soil properties P. vittt ws found to e growing well t ll of the smpling sites, reching height of cm nd showing no symptoms of toxicity (dt not shown). At site Shiling (SL), only P. cretic were collected s P. vittt did not grow here. In generl, P. cretic hd lower iomss nd were less undnt thn P. vittt plnts. In contrst to P. vittt nd P. cretic, P. multifid ws found only rrely, with only three smples collected from totl of 112 ferns in this survey (Tle 1). Cyclosorus cumintus, non-pteris fern, hd ccumulted high concentrtions of As nd ws lso found in undnce t ZMD, where As concentrtions in the soils rnged from 285 to 2603 mg kg )1 ; this my indicte tht this fern hs similr As tolernce s P. vittt nd P. cretic (Tle 1). Dicrnopteris dichotomy ws the dominnt species t LMC; however, it only ccumulted 3.59 mg kg )1 As in the fronds compred to the mg kg )1 As in the fronds of P. vittt t the sme site.

5 Environ Geochem Helth The ph in the growing soils of P. vittt ws mostly in the rnge of 7 8, except t LMC, where the verge vlue of ph in growing soils ws P. cetic ws found to e growing on slightly cidic soils t ZMD nd on strongly lkline soils t SL nd GJ, with men ph vlues t the ltter sites of This ltter ph rnge ws lso oserved for P. multifid, which my indicte the dpttion of Pteris ferns to soil ph chnges (Tle 1). However, Blechnum orientle, non- Pteris fern found nery P. vittt t BS nd GZ, ws growing in soils with ph of only 4.05 nd 4.70 t GZ nd BS, respectively, which were much lower thn those tolerted y P. vittt. The lowest ph 3.67 ws recorded in growing soils of D. dichotomy t LMC, indicting tht this fern prefers strong cidic soils. The distriution ptterns of the vrious forms of As in the soils t different sites were similr. As extrcted in the first three steps of the sequentil extrction procedure, which were the ioville, C-incorported nd Al-incorported frctions, respectively, generlly represented less thn 5% of the totl As. Most of the As ws extrcted during the lst two steps, suggesting tht As ws minly incorported with Fe oxides nd silicon minerl phses in the soils (Fig. 1). As concentrtion in soils nd ferns t different sites Among the four sites with high As levels in the soils ZMD, LMC, GJ nd GT As concentrtion in the fronds of P. vittt were invrily % BS GZ SL GJ GT LMC ZMD Smpling site F5 F4 F3 F2 F1 Fig. 1 The distriution of As forms y sequentil extrction t different sites. F1 Bioville, F2 C-incorported, F3 Al-incorported, F4 Fe-incorported, F5 residul high, with the highest As concentrtion recorded s 3599 mg kg 1 t ZMD, suggesting tht high As concentrtions in soils results in high As ccumultion in the plnt (Tle 1). Although the soil ph t LMC ws mostly lower thn 6, we did not find reduced ccumultion of As y P. vittt, indicting tht As ccumultion y P. vittt ws not ffected y soil ph in the field. At BS nd GZ, lthough the As concentrtions were gretly lower thn those t ZMD, LMC, GT nd GJ, P. vittt ws le to ccumulte nerly 320 mg kg 1 As in the fronds, which reflects the lrge cpcity of this plnt to ccumulte As. P. cretic ws clerly the second most efficient of the ferns tested with respect to the efficiency to ccumulte As (Tle 1). As the As concentrtion in soils incresed from SL to ZMD to GJ, more As ws ccumulted y this fern, with the highest As concentrtion recorded in P. cretic plnts t GJ 757 mg kg 1 suggesting tht P. cretic lso ccumultes more As s the concentrtion of As increses in the growing soil. P. multifid, which ws le to ccumulte slightly more As in the fronds thn wht ws present in the growing soils, reched mximum As concentrtion of 341 mg kg 1 t GJ; this fern type ws the lest efficient of the three Pteris ferns with respect to As ccumultion. C. cumintus, lthough growing together with P. vittt on soils with high As levels t ZMD, contined fr lower levels of As in the fronds less thn 24.3 mg kg 1 As thn P. vittt (Tle 1). Nevertheless, this fern could grow well nd undntly on soils with high As concentrtions of mg kg 1, indicting tht it hs gret tolernce to As. At BS nd GZ, lthough the rnge of As concentrtions in the growing soils of B. orientle were the sme with those of P. vittt, the As concentrtions in the fronds of B. orientle were less thn 1.32 mg kg 1, much lower thn those of ll the Pteris ferns in this survey, reflecting different mechnism of As ccumultion etween the two gener of ferns (Tle 1). Pteridium quilinum nd Dicrnopteris dichotom from GT nd LMC, while ccumulting more As thn B. orientle from BS nd GZ, lso did not demonstrte n As ccumultion ility (Tle 1).

6 Environ Geochem Helth As trnsloction nd ioccumultion fctors of ferns In generl, the concentrtions of As in the fronds of the Pteris ferns studied were greter thn those in roots, wheres the reverse ws true for the non- Pteris ferns (Tle 1). Consequently, the TFs for most of the Pteris ferns were greter thn 1 (Tle 1, Fig. 2). For P. vittt, the gretest BF ws mesured in P. vittt plnts t GZ, with 51 mg kg 1 As in the soil (Fig. 2). The ANOVA test showed tht the BFs of P. vittt chnged mong the different sites, wheres the TFs did not even though the As levels vried (Fig. 2). The constnt vlue of the TFs of P. vittt t ll six sites with different As sources suggests tht As trnsloction in P. vittt is constitutive property. Concentrtions of nutrient elements in ferns Iron concentrtions were very high in ll the ferns collected, with the exception of B. orientle, with , , , 1876, nd 492 mg kg 1 in the fronds, nd , , 3880, , 1911 nd 578 mg kg )1 in the roots of P. vittt, P. cretic, P. multifid, C. cumintus, P. quilinum nd D. dichotom, respectively. We then considered sites BS nd GZ, with reltively low As levels, s one group nd sites ZMD, LMC, GJ nd GT, with high As levels, s nother. The concentrtions of As, C, Fe, Mn, K, BF TF BS GZ GJ GT LMC ZMD Smpling site Fig. 2 The vlues of the ioccumultion fctor (BF) nd trnsloction fctor (TF) of Pteris vittt t different sites. Dt re shown s mens stndrd errors. For smple numers refer to Tle 1. Brs with different letters indicte tht the difference is significnt (P < 0.05) c c c Pwere significntly greter nd the level of N ws lower in the fronds of P. vittt plnts growing t the former group of sites reltive to the ltter group; there ws no difference etween the two groups for Cu, Mg nd Zn concentrtions (Fig. 3). Discussion The ility of P. vittt plnts to efficiently ccumulte As when growing in soils with high levels of As, s shown y the high concentrtions of As in the fonds of these plnts growing t the sites with the highest levels of As(Tle 1), indicte tht P. vittt hs gret ility to tolerte nd ccumulte As. In ddition, our oservtion tht P. viitt growing t the BS nd GZ sites, which hd reltively low levels of As, lso ccumulted more thn 300 mg kg 1 As suggests tht P. vittt lso efficiently ccumultes As from soils with low As concentrtions. The As concentrtion in the fronds of P. mulifid ws slightly higher thn tht in its growing soils, therey confirming to some extent the results of other surveys on As mines (Du et l. 2005; Wng et l. 2006). However, we did not find the undnt distriution of P. multifid, s hd een reported y these investigtors. In ddition, oth of these investigtors climed tht P. multifid growing on As tilings could ccumulte more thn 1000 mg kg 1 As in the fronds. Since the As concentrtions t the sites reported y Wng et l. (2006) rnged from 3,611 to 47,235 mg kg 1, they were much higher thn those in our study, which my indicte tht the popultion of P. multifid from the As tilings of Wng et l. s study hd greter As tolernce nd evolved competition priority. More studies re needed to chrcterize the As tolernce nd ccumultion of P. multifid, s the relevnt informtion on this fern is scrce compred to tht ville for P. vittt nd P. cretic. Soils in southern Chin re cidic nd re either yellow or red-yellow on the clssifiction of the soil type (Xiong 1987). However, P. vittt nd P. cretic were found growing t ll the sites except SL, where limestone wethering, mnmde concrete construction nd rick stitches

7 Environ Geochem Helth Fig. 3 Comprison of As nd nutrient element concentrtions in the fronds of P. vittt t sites with high (ZMD, LMC, GT nd GJ) nd low (BS, GZ) As levels. Dt re shown s mens stndrd errors. Brs with different letters indicte tht the difference is significnt (P < 0.05) mg kg Cu Zn Fe Mn Mg C K N P As Sites with low As levels (BS nd GZ) Sites with high As levels (ZMD, LMC, GT nd GJ) provided n lkline condition tht the Pteris ferns prefer. Our survey lso showed tht while P. vittt plnts were more likely e found growing on lkline soils, they were le to grow on cidic soils, s seen t site LMC (Tle 1). The verge winter temperture is the principl limiting fctor to the survivl nd propgtion of P. vittt (Chen et l. 2005). Although the SL site flls within the su-tropic climte zone nd the ph vlues of the soils were greter thn 7, we still did not find P. vittt t this loction. The reson for this is uncler. The BFs mesured in the present study fell within the rnge of (dt not shown), which re similr to those seen y Cille et l. who reported rnge of in pot experiments using nturlly As-contminted soils from the field. Our results re much lower thn those in reported from other greenhouse experiments (Co et l. 2003; Tu nd M, 2003; Zho et l. 2002) in which solule As slts were dded to uncontminted soils or composts; this most likely would hve resulted in much higher As phytovilility thn in the nturlly contminted nd ged soils. The vlues of TFs of P. vittt smpled in n expnding circle t six sites from different As sources further confirmed tht As-hyperccumultion y P. vittt hs constitutive chrcter (Wei nd Chen 2006; Wei et l. 2006; Zho et l. 2002). This should e n importnt fct for considertion during field screening for hyperccumultors. Previous studies hve not pid ttention to this phenomenon, s the metl concentrtions nd BFs in plnts depend lrgely on the metl concentrtions nd phytoville frctions in soils, wheres the TFs should e generlly consistent t vlue tht is greter thn 1. Therefore, for field screening of hyperccumultors, it is importnt to collect oth the shoots nd the roots of plnts. If TF is greter thn 1 nd high metl concentrtion is recorded in plnt, it should e considered to e hypercccumultor cndidte. We hve successfully discovered two species of As-hyperccumulting ferns, P. vittt nd P. cretic, in Chin y this method, with susequent pot experiments under controlled conditions confirming their hyperccumulting properties (Chen et l. 2002; Wei et l. 2002). These hyperccumulting properties were susequently confirmed y other workers (Mehrg 2003; Zho et l. 2002). The Fe concentrtion we mesured in the fronds of P. vittt ws much higher thn the rnges tht hve een reported previously in nonhyperccumultors (Jones 1998; Kt-Pendis nd Pendis 2001). In ddition, we found tht high As concentrtion in the soils resulted in greter As nd Fe concentrtion in P. vittt fronds, suggesting tht P. vittt proly tkes up As nd Fe together from the roots into the fronds (Fig. 3). This rnge ws lso fr higher thn tht reported y Tu nd M (2005) who, sed on pot experiments, ssessed the rnge of Fe in P. vittt s eing only mg kg )1. The Fe concentrtion in the fronds of P. vittt ws found y Tu nd M to e negtive with the ddition of As to the soils. In the present study,

8 Environ Geochem Helth however, we did not find correltion etween Fe nd As in P. vittt, which is proly due to the fct tht pot experiments re totlly different from field ones, nd therefore my result in different Fe nd As frctiontion in the soils (McLren et l. 1998; Mter et l. 2003). Our results lso differed from those of Porter nd Peterson (1975) on As-tolernt plnts growing in ndoned mine fields, who lso found significnt correltion etween As nd Fe. Our results were in greement with those of Fitz et l. (2003) who, in rhizosphere study, discovered significntly higher levels of Fe in soil solutions round the roots of P. vittt, suggesting tht the roots of P. vittt ply role in the moiliztion of Fe from soil prticles. However, in our survey we found only reltively low Fe concentrtion in B. orientle, wheres ll of the other ferns ccumulted high Fe concentrtions in oth their fronds nd roots. This my indicte tht Fe hs close ssocition with As tolernce nd/or ccumultion since the three Pteris ferns nd C. cumintus, D. dichotom in this survey showed n As ccumultion nd/or tolernce chrcter, while P. quilinum elongs to the sme fmily of Pteridicee with the Pteris ferns. Arsenic hypertolernce nd hyperccumultion y ferns my e n evolutionry trit, however, the mechnisms hve not een elucidted (Mehrg 2003). While our results point in the direction of possile link etween Fe nd As tolernce nd ccumultion, more studies on the reltionship of As with Fe in ferns re needed to explore the ctul role of Fe in As ccumultion of hyperccumulting ferns. There is currently very little informtion ville on the reltionship etween other elements nd As in As-hyperccumultors. Two groups of investigtors hve reported tht potssium (K) incresed, wheres C decresed, in the fronds of P. vittt when As ws dded to the pots (Lio et l. 2003; Co et l. 2004). In the present study, we found tht the concentrtions of nutrient elements in P. vittt were in the sme rnge s those reported for non-hyperccumultors, with the exception of Fe (Fig. 3) (Jones 1998). Our oservtion of greter Fe, Mn, C, K, P concentrtions in the fronds of P. vittt plnts from sites with higher As levels, compred to those in plnts from sites with lower As levels, suggests tht P. vittt plnts tke up more of these nutrient elements during the As ccumultion process. Acknowledgements This study ws jointly supported y the Ntionl Nturl Science Foundtion of Chin (Grnt No , ), the Renovtion Project of the Institute of Geogrphicl Sciences nd Nturl Resources Reserch, Chinese Acdemy of Sciences (Grnt No. CXIOG-C04-02), nd the Ntionl Fund for Distinguished Young Scholrs (Grnt No ). CY Wei thnks Prof. L Shi nd XC Zhng from the Institute of Botny, Chinese Acdemy of Sciences for their kind dvice on fern smpling nd help with fern identifiction. References Andre, L. H., Mlcolm, R. S., Dmien, J., Klerk, W., Bstone, E. B., Gerostmoulos, J., & Drummer, O. H. (2004). Exposure to inorgnic rsenic in soil increses urinry inorgnic rsenic concentrtions of residents living in old mining res. Environ Geochem Helth, 26, Bker, A. J. M. (1989). Terrestril higher plnts which hyperccumulte metllic elements review of their distriution, ecology nd phytochemistry. Biorecovery,1, Bech, J., Poschenrieder, C., Llugny, M., Brcelo, J., Thume, P., & Tolois, F. J. (1997). As nd hevy metl contmintion of soil nd vegettion round copper mine in Northern Peru. The Sci Totl Environ, 203, Bondd, B. R., Tu, S., & M, L. Q. (2004). Asorption of folir-pplied As y the As hyperccumulting fern (Pteris vittt L.). The Sci Totl Environ, 332, Cille, N., Swnwick, S., Zho, F. J., & McGrth, S. P. (2004). Arsenic hyperccumultion y Pteris vittt from rsenic contminted soils nd the effect of liming nd phosphte fertiliztion. Environ Pollut, 132, Co, X. D., M, L. Q., & Tu, C. (2004). Antioxidtive responses to rsenic in the rsenic-hyperccumultor Chinese rke fern (Pteris vittt L.). Environ Pollut, 128, Co, X. D., M, L. Q., & Shirlipour, A. (2003). Effects of compost nd phosphte mendments on rsenic moility in soils nd rsenic uptke y the hyperccumultor Pteris vittt L. Environ Pollut, 126, Chng, S., & Jckson, M. L. (1957). Frctiontion of soil phosphorus. Soil Sci, 84, Chen, T. B., Wei, C. Y., Hung, Z. C., Hung, Q. F., & Lu, Q. G. (2002). Arsenic hyperccumultor Pteris vittt L. nd its rsenic ccumultion. Chin Sci Bull, 47, Chen, T. B., Zhng, B. C., Hung, Z. C., Liu, Y. R., Zheng, Y. M., Lei, M., Lio, X. Y., & Pio, S. J. (2005). Geogrphicl distriution nd chrcteristics of hitt of As-hyperccumultor Pteris vittt L. in Chin(in Chinese). Geogr Res, 24,

9 Environ Geochem Helth Cheng, S. (2003).Hevy metl pollution in Chin: origin, pttern nd control. Environ Sci Pollut Res, 10, De Koe (1994). Agrostic cstelln nd Agrostis delictul on hevy metl nd rsenic enriched sites in NE Portugl. The Sci Totl Environ, 145, Du, W. B., Li, Z. A., Zou, B., & Peng, S. L. (2005). Pteris multifid poir., new rsenic hyperccumultor: chrcteristics nd potentil. Int J Environ Pollut, 23, Dun, G. L., Zhu, Y. G., Tong, Y. P., Ci, C., & Kneer, R. (2005). Chrcteriztion of rsente reductse in the extrct of roots nd fronds of Chinese rke fern, n rsenic hyperccumultor. Plnt Physiol, 138, Fitz, W. J., Wenzel, W. W., Zhng, H., Nurmi, J., Stipek, K., Fischerov, Z., Schweiger, P., Kollensperger, G., M, L. Q., & Stingeder, G. (2003). Rhizosphere chrcteristics of the rsenic hyperccumultor Pteris vittt L. nd monitoring of phytoremovl efficiency. Environ Sci Technol, 37, Frncesconi, K., Visoottiviseth, P., Sridokchn, W., & Goessler, W. (2002) Arsenic species in n As hyperccumulting fern, Pityrogrmm clomelnos: potentil phytoremeditor of As-contminted soils. The Sci Totl Environ, 284, Jones, Jr J. B. (1998). Plnt nutrition mnul. CRC Press, Boc Rton, FL, USA. Kt-Pendis, A., & Pendis, H. (2001). Trce elements in soils nd plnts. (3rd ed.), Boc Rton: CRC Press Lio, X.Y., Xio X.Y., Xio, X.Y., Chn T.B. (2003) Effects of C nd As ddition on As, P nd C uptke y hyperccumultor Pteris vittt L. under snd culture (in Chinese). Act Ecologic Sinic, 3, Lio, Z. J. (1989). The contmintion nd hzrdousness of hevy metls in the environment (in Chinese). Beijing: Science Press. M, L. Q., Kenneth, M. K., & Tu, C. (2001). A fern tht hyperccumulting rsenic. Nture, 409, 579. Mndl, B. K., & Suzuki, K. T. (2002). Arsenic round the world: review. Tlnt, 58, Mndl, B. K., Chowdhury, T. R., Smnt, G., Bsu, G. K., Chowdhury, P. P., Chnd, C. R., Lodh, D., Krn, N. K., Dhr, R. K., Tmili, D. K., Ds, D., Sh, K. C., & Chkrorti, D. (1996). Arsenic in groundwter in seven districts of West Bengl, Indi-the iggest rsenic clmity in the world. Curr Sci, 70, Mter, V., Le Hecho, I., Loudigue, A., Thoms, P., Tellier, S., & Astruc, M. (2003). A methodologicl pproch for the identifiction of As ering phses in polluted soils. Environ Pollut, 126, McLren, R. G., Nidu, R., Smith, J., & Tiller, K. G. (1998). Frctiontion nd distriution of As in soils contminted y cttle dip. J Environ Qul, 27, Mehrg, A. A. (2003). Vrition in As ccumultionhyperccumultion in ferns nd their llies. New Phytologist, 157, Mehrg, A. A., Nylor, J., & Mcnir, M. R. (1994). Phosphorus nutrition of rsente-tolernt nd non-tolernt phenotypes of velvet grss. J Environ Qul, 23, Nordstrom, D. K. (2002). Worldwide occurrences of As in ground wter. Science, 296, Ptel, K. S., Shrivs, K., Brndt, R. N., Jkuowski, W. C., & Hoffmnn, P. (2005). Arsenic contmintion in wter, soil, sediment nd rice of centrl Indi. Environ Geochem Helth, 27, Porter, E. K., & Peterson, P. J. (1975). Arsenic ccumultion y plnts on mine wste (United Kingdom). The Sci Totl Environ, 4, Porter, E. K., & Peterson, P. J. (1977). Arsenic tolernce in grsses growing on mine wste. Environ Pollut, 14, Tu, C., & M, L. Q. (2003). Effects of rsente nd phosphte on their ccumultion y n rsenic hyperccumultor Pteris vittt L. Plnt nd Soil, 249, Tu, C., & M, L. Q. (2005). Effects of rsenic on concentrtion nd distriution of nutrients in the fronds of the rsenic hyperccumultor Pteris vittt L. Environ Pollut, 135, Visoottiviseth, P., Frncesconi, K., & Sridokchn, W. (2002). The potentil of Thi indigenous plnt species for the phytormedition of As contminted lnd. Environ Pollut, 118, Wng, H. B., Ye, Z. H., Shu, W. S., Li, W. C., Wong, M. H., & Ln, C. Y. (2006). Arsenic uptke nd ccumultion in fern species growing t rsenic-contminted sites of southern chin: field surveys. Int J Phytoremedition, 8, Wei, C. Y., Chen, T. B., Hung, Z. C., & Zhng, X. Q. (2002). Cretn rke n rsenic-ccumulting plnt (in Chinese). Act Ecologic Sinic, 22, Wei, C. Y., & Chen, T. B. (2006). Arsenic ccumultion y two rke ferns growing on n rsenic mine nd their potentil in phytoremedition. Chemosphere, 63, Wei, C. Y., Sun, X., Wng, C., & Wng W. Y. (2006). Fctors influencing rsenic ccumultion y Pteris vittt: comprtive field study t two sites. Environ Pollut, 141, Xiong, Y. (1987). Soils in Chin (in Chinese). Beijing: Chin Science Press. Yng, L. S., Peterson, P. J., Willims, W. P., Wng, W. Y., Hou, S. F., & Tn, J. A. (2002). The reltionship etween exposure to rsenic concentrtions in drinking wter nd the development of skin lesions in frmers from Inner Mongoli, Chin. Environ Geochem Helth, 24, Zhng, W., Ci, Y., Tu, C., & M, L. Q. (2002) As specition nd distriution in n As hyperccumulting plnt. The Sci Totl Environ, 300, Zho, F. J., Duhm, S. J., McGrth, S. P. (2002) As hyperccumultion y different fern species. New Phytologist, 156,