LEAD contamination in soils is of major concern due

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1 Pulished online Jnury 25, 2007 Applition Methods Affet Phosphorus-Indued Led Immoiliztion from Contminted Soil Joon Ki Yoon, Xinde Co, nd Len Q. M* Reprodued from Journl of Environmentl Qulity. Pulished y ASA, CSSA, nd SSSA. All opyrights reserved. ABSTRACT Phosphte rok (PR) nd phosphori id (PA) re n effetive omintion of P soures for immoilizing P in ontminted soils. This olumn experiment exmined the effetiveness of different pplition methods on P immoiliztion in ontminted soil. Phosphte ws pplied t P/P molr rtio of 4 with hlf s PR nd hlf PA. While PR ws mixed with the soil or pled s lyer, queous PA ws pplied from the top of the olumn s one or two pplitions. After 4 wk of inution, totl nd solule P nd P, TCLP-P (toxiity hrteristi lehing proedure) nd PBET-P (physiologilly-sed extrtion test) in the P-treted soil were determined. Phosphte ddition effetively redued lehle P to elow the EPA drinking wter stndrd of 15 mgl 21 in ll tretments. Mixing oth PA nd PR with the soil ws the most effetive method in P immoiliztion, reduing TCLP-P y up to 95% nd PBET-P y 25 to 42%. Applition of PR s lyer in the soil olumn ws the most effetive in reduing P migrtion (y 73 79%) nd minimizing soil idifition nd P entrophition, potentil drwks of PA. Applying PA in two pplitions ws less effetive thn one pplition. Mixing PR nd PA with the soil plus pling PR s lyer n e employed for effetive remedition of P-ontminted soils, reduing P lehility, iovilility, nd moility while minimizing soil idifition nd P entrophition. LEAD ontmintion in soils is of mjor onern due to not only its toxiity to humns nd nimls, ut lso to its ese of exposure through ingestion or inhltion. Ativities suh s mining nd mnufturing, nd the use of syntheti produts (e.g., pestiides, pints, tteries, nd industril wste) hve resulted in mny P-ontminted sites. Over time, the P loding rte in soil exeeds its nturl removl rte y more thn 20- fold (Nrigu, 1978). A soil is generlly onsidered ontminted with P when its totl P onentrtion exeeds 400 mg kg 21 (USEPA, 1996), nd remedition is required t this level (OSWER, 1994). Vrious remedition tehnologies hve een developed to len up P-ontminted soils. Among those, in situ P stiliztion using inding gents is promising pproh due to its sustinility nd osteffetiveness. Other remedition tehnologies, inluding exvtion, solidifition, nd heltion/extrtion, re either very ostly or only prtilly effetive. The estimted ost of solidifition is out $750 m 23 nd tht of stiliztion $250 m 23. Stiliztion seems to e more fesile option due to its ese of opertion nd reltively low ost (Wng et l., 2001). Soil nd Wter Siene Dep., Univ. of Florid, Ginesville, FL Reeived 11 Aug *Corresponding uthor (lqm@ufl.edu). Pulished in J. Environ. Qul. 36: (2007). Tehnil Reports: Hevy Metls in the Environment doi: /jeq ª ASA, CSSA, SSSA 677 S. Segoe Rd., Mdison, WI USA In situ P immoiliztion in soil using phosphte hs een onsidered ost-effetive nd environmentllyenign remedition tehnology. When P rets with P in soil, it trnsforms retive nd ioville P speies into more stle forms. Pyromorphite is one of the lest solule forms of P found in soils under wide rnge of environmentl onditions. The iovilility nd moility of soil P n e drstilly redued when unstle P forms, suh s errusite (PCO 3 ), re onverted into pyromorphite (Zhng nd Ryn, 1999). During the lst dede, mny reserhers hve suessfully demonstrted the effetiveness of phosphte-indued P immoiliztion y mixing phosphte minerls with P-ontminted soils (M et l., 1993, 1994; Cotter- Howells, 1996). Dissolution of P ompounds followed y preipittion of P-phosphte hs een onsidered s primry mehnism for P immoiliztion in soils (M et l., 1993). Thus, suessful immoiliztion of P in soil requires enhned soluility of soil P nd P y deresing soil ph nd/or pplying suffiient mount of solule P. Among vrious P soures, phosphte rok (PR) hs een proved to e fesile to immoilize P in soils. Phosphte rok, omplex ssemlge of phosphte minerls, is minly omposed of mirorystlline ronte fluorptite (M et l., 1995). Its effetiveness in immoilizing P primrily depends on its ility to provide solule P (M et l., 1993, 1995). To ompenste for its low soluility in soil, solule phosphori id (PA) hs een used in omintion with PR. This pproh hs een used to effetively immoilize P from P-ontminted soil (Co et l., 2001). The role of PA in the mixture ws to soluilize P minerls in soils nd PR, therey inresing the ville P nd P in the soil. This, in turn, filittes more preipittion of P-phosphte ompounds. Applition of PA promoted the gretest soil ph redution while mixture of PA nd PR yields the est overll results for in situ P immoiliztion with less soil ph hnge nd less P lehing (Co et l., 2001). The ojetive of this study ws to evlute the effetiveness of different pplition methods on P immoiliztion in soil using mixture of PR nd PA s P soure. This ws omplished y (i) determining P lehing hrteristis nd iovilility; nd (ii) to evlute P distriution in soil fter P pplition. MATERIALS AND METHODS Site Chrteriztion The soil used for this study ws olleted from Pontminted site in n urn re of northwest Jksonville, Arevitions: XRD, X-ry diffrtion; TCLP, toxiity hrteristi lehing proedure; PBET, physiologilly-sed extrtion test; PR, phosphte rok; PA, phosphori id. 373

2 374 J. ENVIRON. QUAL., VOL. 36, MARCH APRIL 2007 Reprodued from Journl of Environmentl Qulity. Pulished y ASA, CSSA, nd SSSA. All opyrights reserved. Florid. The site is loted in vnt, fened retngulr re (4100 m 2 ), nd overed y vegettion (minly grsses). Pst industril tivities, whih inluded gsoline sttion, slvge yrd, uto ody shop, nd reyling opertion for led tteries, hve ll ontriuted to the ontmintion of this site. The totl P onentrtions in the soil rnged from 36 to mg kg 21. Led onentrtion deresed with soil depth, with the mjority of the P present ner the soil surfe (0 20 m). Minerlogil hrteriztion of the site y X-ry diffrtion (XRD) revels tht PCO 3 (erussite) is the predominnt P minerl in the snd frtion nd PO in the silt nd ly frtion (Co et l., 2001). Soil Chrteriztion Soil smples were olleted from the top 20 m t the Jksonville site. They were olleted from lotion where high onentrtions of P re present (Co et l., 2001). They were ir-dried, sieved through 2-mm stinless steel sreen nd stored t room temperture. The soil smple ws thoroughly mixed to ensure uniformity. They were then digested using the hot-lok digestion proedure (USEPA Method 3050A) for totl P onentrtion. The len soil smple ws olleted from outside the fene diretly djent to the site. The P ontents nd ph in the len nd ontminted soils were 77 nd 5017 mg kg 21, nd 6.7 nd 6.2, respetively. Column Preprtion The olumn test ws used to simulte field onditions. A totl 400 g of soil ws pked into PVC olumn (40 m height y 3.5 m dimeter), with the top hlf (0 20 m) eing filled with the ontminted soil nd the lower hlf (20 40 m) the len soil to pproximte the P distriution t the site. The ulk density of pked soil ws 1.2 g m 23. A totl of 18 olumns were mounted with eh tretment replited three times. The phosphte pplition rte ws sed on P/P molr rtio 5 4, whih ws the optimum rte for P-immoiliztion in ontminted soil (Co et l., 2001). A fixed mount of P ws pplied to ll olumns exept for the ontrol, with hlf s PR (R) nd hlf s PA (A). Both PR nd PA were pplied only to the first 20 m of the soil olumn, i.e., the ontminted soil. Phosphte rok ws dded in two wys: either mixed (M) with the ontminted soil or dded s lyer (L) pled etween the ontminted nd len soil. Phosphori id ws dded in three wys, dded simultneously with the PR (S1), one pplition week lter (W1), or two pplitions with week prt (W2). While PR ws dded s powder without grinding, PA ws dded from the top s solution to 75% field pity of the soil. A totl of five different P pplition methods were used in this experiment nd they were s follows: R M A S1 : PR ws mixed with the ontminted soil nd PA ws dded t the sme time; R M A W1 : PR ws mixed with the ontminted soil (Dy 1) nd PA ws dded 1 wk lter (Dy 8); R L A S1 : PR ws dded s lyer nd PA ws dded t the sme time; R M A W2 : PR ws mixed with the ontminted soil (Dy 1) nd PA ws dded two times (Dy 1 nd Dy 8) with 1 wk prt; R L A W2 : PR ws dded s lyer (Dy 1) nd PA ws dded two times (Dy 1 nd Dy 8) with 1 wk prt. A fine textured glss wool ws pled t the ottom of ll olumns, ting s filter for the lehte. The soil olumns were lehed with deionized distilled wter twie up to 2 pore volumes 1 nd 4 wk fter the lst pplition of PA. After inution t 75% field pity of the soil, the PA in the tretments R M A S1,R L A S1, nd R M A W1 ws in the soil for 5 nd 4 wk, wheres hlf of the PA in the tretment R M A W2 ws in the soil for 5 wk nd the other hlf 4 wk. By ompring these tretments, the effets of inution time nd pplition methods on phosphte-indued P immoiliztion n e otined. Anlytil Proedure Soil ph ws mesured with deionized wter t 1:1 soil/ solution rtio fter 24 h of equilirium. Totl P ws mesured olorimetrilly with Shimdzu 160U spetrometer using the molydte sori id method (Pge et l., 1982). At the end of the experiment, the soil olumns were divided into four setions (0 10, 10 20, 20 30, nd m). The modified physiologilly-sed extrtion test (PBET) (the soils were mixed with M HCl solutions t 1:100 soil/ solution rtio t ph of 1.95) nd toxiity hrteristi lehing proedure (TCLP) were onduted in eh setion to determine the effetiveness of P-indued P immoiliztion in the soil. Totl P in eh soil lyer ws lso determined to ompre the downwrd movement of P mong different tretments. After lehing olumns with up to 2 pore volumes of distilled deionized wter (DDW) twie, olumn lehtes were nlyzed for P nd P onentrtions. Led nlysis ws performed using flme tomi sorption spetrophotometer (AAS, 220 FS with SIPS, Vrin, Wlnut Creek, CA) or grphite furne tomi sorption spetrophotometer (SIMMA 6000, PerkinElmer Corp., Norwlk, CT). Stndrd soil referene mterils (2709 Sn Joquin soil nd 2710 Montn soil) from the Ntionl Institute of Siene nd Tehnology (NIST, Githersurg, MD) were rried through the digestion nd nlyzed s prt of qulity ontrol (within %). Regent lnks nd internl stndrds were used where pproprite to ensure ury nd preision. Differenes mong different mens were determined y nlysis of vrine. Soil ly frtions were seprted y entrifugtion nd nlyzed using XRD to detet the formtion of pyromorphite in the soil. All results re expressed s n verge of triplites 6 stndrd devition. The effet of tretment ws determined y nlysis of vrine using the Sttistil Anlysis System (SAS Institute In., 1987). RESULTS Soil Chrteriztion The soil is sndy with ph of 6.2 to 6.7 (dt not shown), whih is greter thn typil Florid soils (Chen et l., 1999). Led ws the min ontminnt with onentrtion of 5017 mg kg 21, exeeding the ritil level of lenup for industril soils (1400 mg kg 21 ). More detiled desription of the site n e found in Co et l. (2001). Generlly, P ws onentrted t the surfe soil (0 20 m) nd its onentrtions deresed with soil depth. Effets of Phosphorus Applition on Soil ph The phs of the P-treted soils were mesured to evlute the degree of soil idifition. As seen from Tle 1, redued soil ph in the surfe soil (0 20 m) ws oserved in ll P-treted soils due primrily to the ddition of PA. Signifint redution in ph, pproxi-

3 YOON ET AL.: P APPLICATION METHODS AFFECT PB IMMOBILIZATION 375 Tle 1. Effets of P tretments on soil ph. Reprodued from Journl of Environmentl Qulity. Pulished y ASA, CSSA, nd SSSA. All opyrights reserved. Soil lyer Control R M A S1 R M A W1 R L A S1 R M A W2 R L A W2 m R M A S1 : Phosphte rok (PR) ws mixed with the soil nd phosphori id (PA) ws dded simultneously; R M A W1 : PR ws mixed nd PA ws dded 1 wk lter; R L A S1 : PR ws dded s lyer nd PA ws dded simultneously; R M A W2 : PR ws mixed nd PA ws dded two times with 1 wk prt; R L A W2 :PR ws dded s lyer nd PA ws dded two times with 1 wk prt. mtely 1 ph unit, ws limited to only the top 10 m. Yng et l. (2001) dded 5000 mg kg 21 of P s PA to immoilize P nd reported redution of soil ph y three units from 7.22 to The presene of PR in the soil hs uffered soil ph in our experiment. The ft tht redution in soil ph ws mostly limited to the top 20 m of the soil olumn (Tle 1) indites limited movement of P in the soil profile. Redution of soil ph to ner 5.5 is neessry for effiient P immoiliztion in soils. Sine lrge frtion of the P in the soil is ssoited with ronte (Co et l., 2001), ddition of PA to the soil is essentil for the dissolution of PR nd P ronte. Solule P nd P my enhne preipittion of insolule pyromorphitelike minerls in soil, whih t given P nd phosphte onentrtions re formed t greter rte t ph 5 thn t ph 6 or 7 (Lperhe et l., 1996). Other reserhers hve used liming mterils long with phosphte tretments to uffer ginst derese in ph (Bst nd MGowen, 2004; Brown nd Elliott, 1992). Also the pplition of PA to idify soil my inrese the risk of ground wter ontmintion with P nd other hevy metls, so re should e exerised Toxiity Chrteristi Lehing Proedure Led The toxiity hrteristi lehing proedure is designed to evlute the potentil for migrtion of hzrdous onstituents through the vdose zone soils to wter tle under lndfill onditions. Higher P onentrtion in TCLP extrts is inditive of higher potentil for P moility in soil. Toxiity hrteristi lehing proedure-p in the ontminted soil, i.e., top 20 m of the olumn, ws determined. The TCLP-P onentrtions in the ontrol soil without P tretment were s high s 127 mg L 21, signifintly greter thn the regultory level of 5 mg L 21 (Fig. 1). This is euse most of the P in this soil is in the ronte frtion, whih would redily dissolve in n idi TCLP solution (Melmed et l., 2003). Phosphte ddition, on the other hnd, gretly redued TCLP-P, i.e., y.95% (Fig. 1). As result of P pplition, TCLP-P in the ontminted soil (0 20 m) ws redued to elow 5 mg L 21 (the EPA riteri for TCLP-P) in ll five tretments (Fig. 1). This is onsistent with the results y Hettirhhi et l. (2000) nd Chen et l. (2003) who reported the ddition of P signifintly redued TCLP-P in ontminted soils to elow the ritil level of 5 mg L 21. Among the five P tretments, the highest redution in TCLP-P ws oserved for tretment R M A S1 (PR ws mixed nd PA ws dded simultneously), whih hd less thn 3 mg L 21 in the ontminted soil (Fig. 1). On the other hnd, tretment R M A W2 (PR ws mixed with nd PA ws dded two times with 1 wk prt) ws the lest effetive in reduing TCLP-P in the soil. This mkes sense sine the PA in the tretment R M A S1 ws in the soil more thn week longer thn tht in R M A W2. This indites tht not only the method of P pplition is importnt, ut the retion time of P with P is lso ritil. Phosphte-indued P immoiliztion ourred during the 4 wk of inution in ddition to during the TCLP extrtion. Led Biovilility Inidentl ingestion of P-ontminted soil hs een reported s primry exposure pthwy to humns for elevted lood P levels (Chen et l., 2003). A physiologilly-sed extrtion test hs een used to estimte P iovilility (in vivo), whih simultes P dissolution under gstrointestinl onditions using hemil extrtion (Yng et l., 2001). Led iovilility in ontminted soils hs een shown to vry with its minerlogil forms (Dvis et l., 1993). In vivo nd in vitro ssys hve indited tht the mmmlin gstrointestinl vilility of P is ontrolled y the form nd reltive soluility of P solids (Ruy et l., 1996). The PBET hs een used to ssess the P iovilility Soil depth (m) RLAW2 RMAW2 RLAS1 RMAW1 RMAS1 Control TCLP P(mg L -1 ) Fig. 1. Toxiity hrteristi lehing proedure (TCLP) metl ontents in setioned soil olumns (0 20 m) fter lehing. Detetion limit mg L 21.R M A S1 : Phosphte rok (PR) ws mixed with the soil nd phosphori id (PA) ws dded simultneously; R M A W1 : PR ws mixed nd PA ws dded 1 wk lter; R L A S1 :PR ws dded s lyer nd PA ws dded simultneously; R M A W2 : PR ws mixed nd PA ws dded two times with 1 wk prt; R L A W2 : PR ws dded s lyer nd PA ws dded two times with 1 wk prt. Columns with the sme letter re not signifintly different t p, 0.05.

4 376 J. ENVIRON. QUAL., VOL. 36, MARCH APRIL 2007 Reprodued from Journl of Environmentl Qulity. Pulished y ASA, CSSA, nd SSSA. All opyrights reserved. in ontminted soil fter reeiving vrious mounts nd soures of P (Hettirhhi et l., 2000). The iovilility of soil P is ssoited with its soluility nd dissolution rte in the gstrointestinl trt. Bioville P in the ontminted soil sed on PBET ws redued fter P pplition in ll five tretments (Fig. 2). The ontrol soil showed 50 to 51% of ioville frtion P while P-treted soils showed of 30 to 45% ioville frtion P. Redution of ioville P ws similr to the 25 to 35% redution reported y Hettirhhi et l. (2000) nd 39% y Yng et l. (2001). The gretest redution in PBET-P ws otined gin from the tretment R M A S1, similr to the TCLP results (Fig. 1), ut no signifint differenes were found etween tretments. PBET P(mg L -1 ) Control RMAS1 RMAW1 RLAS1 RMAW2 RLAW2 Led Migrtion in Soil In most ontminted soils, metls do not pper to leh downwrd in signifint quntities in the short term primrily due to their strong intertions with the soils. However, in the long run, metls n leh downwrd in soil due to their omplextion with soluilized orgni mtter, espeilly in n lkline environment where orgni mtter is more solule (Mrshner nd Wilzynski, 1991). This my e true t this site where soil orgni mtter (3.91%) nd ph (6.95) re muh higher thn those of typil Florid soils (Chen et l., 1999). To determine the effetiveness of P tretment to prevent P downwrd migrtion, totl P onentrtions in ottom hlf of the olumn (20 40 m) were determined (Fig. 3). As expeted, signifint downwrd movement of P ws oserved in the ontrol soil, espeilly in the 20- to 30-m frtion, whih ws loted diretly under the ontminted soil (0 20 m). The initil P onentrtion in the lower hlf of the olumn (20 40 m) in the ontrol soil ws 77 mg kg 21 (dt not shown). After eing in ontt with the P-ontminted soil for 5 wk under 75% field pity, the P onentrtion in the 20- to 30-m soil olumn frtion inresed to 365 mg kg 21. However, P migrtion ws mostly limited to tht setion of the olumn s P onentrtion in the 30- to 40-m frtion remined t 77 mg kg 21 nd little differene ws oserved mong the five tretments in 30- to 40-m frtions (Fig. 3). All tretments were effetive in reduing P migrtion exept R M A W2 where PR ws mixed with the ontminted soil in the top 20 m, nd PA ws pplied two times with 1 wk etween pplitions. Sine PA ws dded in two liquots, the mount of idity ws proly insuffiient to dissolve enough P from the soil to indue the preipittion of P-phosphte minerls. This ws onfirmed y the P dt where P onentrtion in the lehte of R M A W2 ws the lowest (Fig. 4). This ws lso onsistent with the highest TCLP-P (Fig. 1) nd PBET-P (Fig. 2) oserved in the tretment R M A W2. Tretments with PR pled s lyer (e.g., R L A S1 nd R L A W2 ) were more effetive in reduing P migrtion 0-10 m m m m Tretments Fig. 3. Totl P onentrtion in setioned soil olumns (20 40 m). Detetion limit mg L 21.R M A S1 : Phosphte rok (PR) ws mixed with the soil nd phosphori id (PA) ws dded simultneously; R M A W1 : PR ws mixed nd PA ws dded 1 wk lter; R L A S1 : PR ws dded s lyer nd PA ws dded simultneously; R M A W2 : PR ws mixed nd PA ws dded two times with 1 wk prt; R L A W2 : PR ws dded s lyer nd PA ws dded two times with 1 wk prt. Columns with the sme letter re not signifintly different t p, 0.05 for the sme depth. 0 Control RMAS1 RMAW1 RLAS1 RMAW2 RLAW2 Tretments Fig. 2. Physiologilly sed extrtion test (PBET)-extrtle P ontents in setioned soil olumns (0 20 m) fter lehing. Detetion limit mg L 21.R M A S1 : Phosphte rok (PR) ws mixed with the soil nd phosphori id (PA) ws dded simultneously; R M A W1 : PR ws mixed nd PA ws dded 1 wk lter; R L A S1 : PR ws dded s lyer nd PA ws dded simultneously; R M A W2 : PR ws mixed nd PA ws dded two times with 1 wk prt; R L A W2 : PR ws dded s lyer nd PA ws dded two times with 1 wk prt.

5 YOON ET AL.: P APPLICATION METHODS AFFECT PB IMMOBILIZATION 377 Reprodued from Journl of Environmentl Qulity. Pulished y ASA, CSSA, nd SSSA. All opyrights reserved. Lehte P (mg L -1 ) st lehing Control RMAS1 RMAW1 RLAS1 RMAW2 RLAW2 Tretments 2nd lehing Fig. 4. Phosphorus onentrtions (mg L 21 ) in olumn lehte (0 20 m). R M A S1 : Phosphte rok (PR) ws mixed with the soil nd phosphori id (PA) ws dded simultneously; R M A W1 : PR ws mixed nd PA ws dded 1 wk lter; R L A S1 : PR ws dded s lyer nd PA ws dded simultneously; R M A W2 : PR ws mixed nd PA ws dded two times with 1 wk prt; R L A W2 : PR ws dded s lyer nd PA ws dded two times with 1 wk prt. thn those where PR ws mixed with the soil (R M A S1, R M A W1, nd R M A W2 ; Fig. 3). This my e due to the formtion nd/or ontinment of stle P minerls within the PR lyer. Among the tretments where PR ws mixed with the soil, tretment R M A S1, where PA ws pplied t the sme time with PR, ws the most effetive. To determine the mehnism of redution in P downwrd movement, the soil round the PR lyer ws seprted nd nlyzed with XRD. Previous nlysis of minerlogil hnges over time resulting from P ddition using XRD showed formtion of stle pyromorphite-like minerls in P-treted soil (Co et l., 2002). However, no P-phosphte ws identified in the ly frtions in this reserh (dt not shown). With the P onentrtion in the soil eing lower thn the detetion limit for XRD ( 1%), formtion of P-phosphte in the soil nnot e ruled out. Lehle Led nd Phosphorus Column studies more losely simulte field onditions thn TCLP extrtion does. To simulte field onditions, soil olumns were lehed twie with DDW nd the lehte ws olleted. The lehte ws nlyzed for totl P nd P onentrtions. All P-treted soils showed tht lehle P hd een redued to elow the EPA drinking wter regultory level of 15 mg L 21 or nondetetle (Tle 2). The highest P onentrtion ws gin oserved in the tretment R M A W2, omprle to the ontrol soil. Led onentrtions in the seond lehte were lower thn those in the first lehte. Signifint differenes were seen in the relese of P etween tretments with different pplition methods of PA, where the tretment R M A W2 ws oserved to e the Tle 2. Effets of P tretments on P onentrtions (mg L 21 ) in soil lehte. lest effetive yet still elow the EPA regultory level (15 mgl 21 ). All five tretments proved to e effetive in reduing P soluility in the soil. The ddition of lrge mounts of P to ontminted soil my inrese the risk of eutrophition in wter odies (Bst nd MGowen, 2004). Tking P lehing in the soil into ount is importnt with respet to seondry ontmintion. Although it is well reognized tht phosphte mendment is n effetive method for immoilizing metls in ontminted soils, it is unvoidle tht some elevted solule P my enhne eutrophition risk (Co et l., 2001). This ws not the se in this study s P lehed from the P-treted soil olumns ws less thn 1 mg L 21 for ll tretments (Fig. 4). Tretments where PA ws pplied in two liquots (R M A W2 nd R L A W2 ) hd lower P onentrtions in the lehte thn in the other tretments. This my indite tht the pplition of P in smll quntities n limit the downwrd movement of PA, however, with orrespondingly lower effiieny in immoilizing P in the soil (Fig. 1 nd 2). Though P relese from P-treted soil ws limited, some of the P, whih ws not onverted to P-phosphte or sored y the soil, ws relesed from the soil. Therefore, ution is needed to ssess the P movement within P-treted fields to minimize eutrophition risk, nd onsidertion should e given to soil type nd the mount of P dded. CONCLUSIONS The effiieny of in situ P-indued P immoiliztion depends on the type nd rte of P mendment, long with pproprite pplition methods. This study hs shown tht pplying mixture of PA nd PR effetively redued TCLP-extrtle P, ioville P (PBET), nd vertil P migrtion in P-ontminted soil. All P-treted soil resulted in signifint redutions in ioville nd lehle P s ompred with the ontrol soil. Of ll the tretments, mixing of PR with the soil oupled with simultneous pplition of PA (R M A S1 ) ws the most effetive in deresing lehle nd ioville P with the lest impt on soil ph nd lowest eutrophition risk. The tretment tht inluded PA eing pplied in two liquots nd PR eing pplied s lyer ws the lest effetive overll. These results lso indite tht simultneously pplied PA with the PR is neessry for effetive immoiliztion of P in soils. The ft tht lyered PR showed lower effiieny in P immoiliztion s ompred with the other tretments my e due to n insuffiient mount of P supplied to the soil. However, the PR lyer showed improved re- Lehing Control R M A S1 R M A W1 R L A S1 R M A W2 R L A W2 First lehing ND ND ND Seond lehing ND ND ND ND R M A S1 : Phosphte rok (PR) ws mixed with the soil nd phosphori id (PA) ws dded simultneously; R M A W1 : PR ws mixed nd PA ws dded 1 wk lter; R L A S1 : PR ws dded s lyer nd PA ws dded simultneously; R M A W2 : PR ws mixed nd PA ws dded two times with 1 wk prt; R L A W2 :PR ws dded s lyer nd PA ws dded two times with 1 wk prt. ND, not deteted; Detetion limit 5 1 mg L 21.

6 378 J. ENVIRON. QUAL., VOL. 36, MARCH APRIL 2007 Reprodued from Journl of Environmentl Qulity. Pulished y ASA, CSSA, nd SSSA. All opyrights reserved. dution of P migrtion over the mixing tretments. Furthermore, these results suggest lyered PR elow ontminted soil my serve s retive rrier to prevent P from migrting into the ground wter. Although the effets of PA on ph nd lehle P were eptle in this experiment, P lehing nd eutrophition my e potentil drwks of its indisriminte utiliztion. The omintion of the soil-pr mixture nd PR lyer n e onsidered s well for remedition of P-ontminted soils, nd with redued lehing, iovilility nd moility of P. ACKNOWLEDGMENTS This reserh ws supported in prt y the Florid Institute of Phosphte Reserh. The uthors would like to thnk Dr. Slly Brown for her onstrutive omments to improve the mnusript. REFERENCES Bst, N.T., nd S.L. MGowen Evlution of hemil immoiliztion tretments for reduing hevy metl trnsport in smelter-ontminted soil. Environ. Pollut. 127: Brown, G.A., nd H.A. Elliott Influene of eletrolytes on EDTA extrtion of P from polluted soil. Wter Air Soil Pollut. 62: Co, X., L.Q. M, M. Chen, S.P. Singh, nd W.G. Hrris Phosphte-indued metl immoiliztion in ontminted site. Environ. Pollut. 122: Co, X., L.Q. M, W.G. Hrris, nd P. Nkedi-kizz Field demonstrtion of metl immoiliztion in ontminted soils using P mendments, FIPR Projet # R. Finl Rep. Univ. of Florid, Ginesville, FL. Chen, M., L.Q. M, W.G. Hrris, nd A. Hornsy Bkground onentrtions of 15 tre metls in Florid soil. J. Environ. Qul. 28: Chen, M., L.Q. M, S.P. Singh, X. Co, nd R. Melmed Field demonstrtion of in situ immoiliztion of soil P using P mendments. Adv. Environ. Res. 8: Cotter-Howells, J Led phosphte formtion in soils. Environ. Pollut. 93:9 16. Dvis, A., J.W. Drexler, M.V. Ruy, nd A. Niholson Mirominerlogy of mine wstes in reltion to led iovilility, Butte, Montn. Environ. Si. Tehnol. 23: Hettirhhi, G., G. Pierzynski, nd M. Rnsom In situ stiliztion of soil led using phosphorus nd mngnese oxide. Environ. Si. Tehnol. 34: Lperhe, V., S.J. Trin, P. Gddm, nd T.J. Logn Chemil nd minerlogil hrteriztions of P in ontminted soil, retions with syntheti ptite. Environ. Si. Tehnol. 30: M, Q., T.J. Logn, nd S.J. Trin Led immoiliztion from queous solutions nd ontminted soils using phosphte roks. Environ. Si. Tehnol. 29: M, Q., S.J. Trin, nd T.J. Logn In situ led immoiliztion y ptite. Environ. Si. Tehnol. 27: M, Q., S.J. Trin, T.J. Logn, nd J. Ryn Effets of queous Al, Cd, Cu, Fe(II), Ni, nd Zn on P immoiliztion y hydroxyptite. Environ. Si. Tehnol. 28: Mrshner, B., nd A.M. Wilzynski The effets of liming on quntity nd hemil omposition of soil orgni mtter in pine forest in Berlin, Germny. Plnt Soil 137: Melmed, R., X. Co, M. Chen, nd L.Q. M Field ssessment of led immoiliztion in ontminted soil fter phosphte pplition. Si. Totl Environ. 305: Nrigu, J.O The iogeohemistry of led in the environment Prt A, B. Elsevier/North-Hollnd Biomedil Press, Amsterdm. OSWER Revised Interim Soil P Guidne for CERCLA Sites RCRA Corretive Ation Filities. 9355:4 12 USEPA, Wshington, DC. Pge, A.L., R.H. Miller, nd D.R. Keeney Methods of Soil Anlysis, Prt 2. Chemil nd Miroiologil Properties. 2nd ed. ASA, Mdison, WI. Ruy, M., A.R. Dvis, S. Shoof, S. Eerle, nd C. Sellstone Estimtion of led nd rseni iovilility using physiologilly sed extrtion proedure. Environ. Si. Tehnol. 30: SAS Institute In SAS user s guide. 6th ed. SAS, Cry, NC. USEPA Soil sreening guidne, user s guidne, EPA 540/ R96/018. Offie of Solid Wste nd Emergeny Response, Wshington, DC. Wng, Y.M., T.C. Chen, K.J. Yeh, nd M.F. Shue Stiliztion of n elevted hevy metl ontminted site. J. Hzrd. Mter. 88: Yng, J., D.E. Mosy, S.W. Cstell, nd R.W. Blnhr Led immoiliztion using phosphori id in smelter-ontminted urn soil. Environ. Si. Tehnol. 35: Zhng, P., nd J.A. Ryn Formtion of hloropyromorphite from glen (PS) in the presene of hydroxyptite. Environ. Si. Tehnol. 33: