Distribution and Fate of Background and Bioavailable Metals in Oregon Agricultural Soils, and Plants

Transcription

1 Distriution nd Fte of Bckground nd Bioville Metls in Oregon Agriculturl Soils, nd Plnts June 9, 7 Prepred y Angel L. Pérez nd Kim A. Anderson Food Sfety nd Environmentl Stewrdship Progrm Deprtment of Environmentl & Moleculr Toxicology Oregon Stte University Agriculturl & Life Sciences Bldg. room 17 Corvllis, OR June 9, 7 1

2 EXECUTIVE SUMMARY Distriution nd Fte of Bckground nd Bioville Metls in Agriculturl Soils nd Plnts Concentrtions of non-nutritive metls nd metlloids in fertilizers, nd griculturl mendments re suject to regultions y stte governments. Oregon must dopt stndrds for rsenic, cdmium, led, mercury nd nickel in these products. The ojective of this regultion is to protect humn helth nd nturl resources from toxicity of these metls/metlloids. In order to set these regultions considertions of cumultive chnge over decdes will e necessry. In review report prepred for ODA in, Curtis nd Smith found tht there were limittions to the ville informtion necessry for models tht represent ehvior of these metls in griculturl systems. Curtis nd Smith lso concluded tht estimtes of the soil metl concentrtion fter 5 yers ( yers for led) dominntly determined the humn helth risk. Curtis nd Smith, rn simultions nd found tht estimtes of the metl distriution coefficients (soil to wter concentrtion rtio) were criticl determinnts in the projections of soil metl ccumultion with time. The lrge disprity etween distriution (K d ) estimtes ws found to e prolemtic nd creted high degree of uncertinty. The ojectives of this study were: Determine the ckground concentrtions of metls in griculturl systems in Oregon. Apply environmentlly relevnt tretment levels of commercilly ville phosphte fertilizer over three yer period, using typicl griculturl prctices. Determine the metls/metlloids concentrtion in the edile portion of crops nd the totl, dissolved, nd lile metl/metlloid concentrtions. Estimte the correltion etween ioville, soil nd soil solution metl concentrtions with the edile crop portion. Define the ioccumultion potentil from fertilizer input of metls/metlloids in griculturl systems over the three yer study. Identify the rtes of chnge for metl concentrtions in distinct griculturl soils over time. The ckground levels of rsenic, cdmium, led, nd mercury were found to e the sme or lower thn those reported y Holgrem et l nd Boerngen nd Shkette yers go. This is consistent with current ntionl trends tht these metls re generlly declining in the environment. The men ckground level of rsenic, cdmium, led, nickel nd mercury re elow the ODEQ soil screening levels for risk ssessments for representtive mmmls. Metl concentrtion in irrigtions wters from Hermiston nd Klmth were elow the fresh wter qulity limit for oth the qutic life nd humn helth criteri. No significnt tretment effect ws oserved for rsenic, led nd nickel in soil. A significnt tretment effect ws oserved for cdmium nd mercury in soil t most sites. Cdmium nd mercury were found in the edile portion of the potto nd whet crop. Nickel ws found in potto. Arsenic nd led were not found in either crop for ny of the trils. For some trils (site nd crop -specific) cdmium, nickel nd mercury were yerly nd/or dose dependent. The ioville metls were site specific nd in generl significnt tretment nd/or yerly effects were seen for cdmium, led, nd nickel. The distriution nd io-distriution coefficients were determined nd generlly found to e lrger thn those reported y Btes nd Shrp, nd typiclly smller thn those reported y Suve et l. The distriution coefficients were similr mong the sites except for rsenic which ws seen to vry significntly etween the sites. There ws slight tendency for the io-distriution coefficients to decrese with tretment nd with yerly pplictions. If these tendencies were to continue with further studies, they my hve long term impliction for risk ssessment. June 9, 7

3 TABLE OF CONTENTS EXECUTIVE SUMMARY... INTRODUCTION... 7 EXPERIMENTAL SECTION... 1 Soil tretment SAMPLE COLLECTION Surfce soils Deep soils Diffusive Grdient in Thin Film soils Plnt CHEMICAL ANALYSIS Regents Methods DGT deployment nd smple nlysis Qulity Control... 1 DATA ANALYSIS... 3 RESULTS nd DISCUSSION... 8 Arsenic... 8 Cdmium Led Nickel Mercury Deep soil... 8 REFERENCES APPENDIX I June 9, 7 3

4 FIGURES AND TABLES FIGURE 1. Oregon field smpling loctions... 1 TABLE 1. Site specifictions nd selected properties of soils FIGURE. Soil smpling scheme from ech of the four field sites. The control indictes 1x ppliction with non-metl rich fertilizer. Tretment indictes either 1x, x, or 3x ppliction with metl rich fertilizer. Within ech replicte 3 su-smples of surfce soil nd DGT soil were tken. Deep soil, lso composite of three su-smples, nd soil fertility were smpled once yer t hrvest... 1 TABLE. Soil ckground concentrtions for five metls in Oregon soils nd Oregon Deprtment of Environmentl Qulity (ODEQ) ird/mmml screening levels soil concentrtions (mg metl / dry kg of soil). (Adpted from Curtis, L.R. nd Smith, B.W.,, ODA report) TABLE 3. Mesured metl concentrtions in fertilizers FIGURE 3. Diffusive Grdients Thinfilm (DGT) Processing from field to lortory nlysis... FIGURE. Diffusive Grdient in Thin Film (DGT) deployed in soil solution. The mjority of metl in soil is ound to solid, with vrile rtes of relese. The frction of metl tht is relesed into solution, or lile metl, diffuses through the diffusive gel lyer nd is ound to the chelex resin. (dpted from Ernsterger et l., ES&T, )... 1 TABLE. Averge percent recovery of check stndrds, spikes nd certified reference mterils... 3 TABLE 5. Metl concentrtions in irrigtion wters from Hermiston nd Klmth field sites TABLE 6. Distriution coefficients (log, 1) for metls in griculturl soils... 5 FIGURE 5. Fertilizer lods (g/h/y) for rsenic, cdmium, led, nickel nd mercury (mg) t four field sites in Oregon FIGURE 6. Dilution to fertilizer in griculturl soil exmple clcultions spredsheet for Klmth Flls experiment sttion sed on soil type nd crop grown FIGURE 7. Arsenic concentrtions (mg/kg) in surfce soil smpled t hrvest from four field sites in Oregon (n=) FIGURE 8. Arsenic concentrtions (µg/l) in soil solution smpled t hrvest from four Oregon field sites (n=) FIGURE 9. Log Kd vlues for As t four Oregon griculturl field sites sed on rtios etween totl recoverle As in surfce soil nd As in soil solution (n=) FIGURE 1. Log Kd mesured t four Oregon field sites. Ech yer represents composite of control nd tretment 1x smples only. Tretment x, nd 3x were omitted FIGURE 11. Cdmium concentrtions (µg/kg) in surfce soil smpled t hrvest from four field sites in Oregon (n=).... FIGURE 1. Cdmium concentrtions (µg/l) in soil solution smpled t hrvest from four field sites in Oregon (n=) FIGURE 13. Cdmium concentrtions (µg/l) mesured y DGT soils smpled t hrvest from four field sites in Oregon (n=)... 6 FIGURE 1. Cdmium concentrtions (µg/kg) in plnt tissue smpled from four field sites in Oregon (n=) June 9, 7

5 FIGURE 15. Log Kd Cd (totl recoverle/soil solution) (L/kg) grouped y tretment level, mesued 3 (Bseline)-6, t four Oregon field sites. Regression equtions represent est fit line through ll of the dt points FIGURE 16. Log Kd-DGT (totl recoverle Cd / DGT mesured Cd) (L/kg) grouped y tretment level, mesued 3 (Bseline)-6, t four Oregon field sites. Regression equtions represent est fit line through ll of the dt points... 5 FIGURE 17. Log Kd mesured t four Oregon field sites. Ech yer represents composite of control nd tretment 1x smples only. Tretment x, nd 3x were omitted FIGURE 18. Log Kd-DGT mesured t four Oregon field sites. Ech yer represents composite of control nd tretment 1x smples only. Tretment x, nd 3x were omitted FIGURE 19. Led concentrtions (mg/kg) in surfce soil smpled t hrvest from four field sites in Oregon (n=) FIGURE. Led concentrtions (µg/l) in soil solution smpled t hrvest from four field sites in Oregon (n=) FIGURE 1. Led concentrtions (µg/l) mesured y DGT soils smpled t hrvest from four field sites in Oregon (n=) FIGURE. Log Kd (totl recoverle P / soil solution P) (L/kg) grouped y tretment level, mesued 3 (Bseline)-6, t four Oregon field sites. Regression equtions represent est fit line through ll of the dt points FIGURE 3. Log Kd-DGT (totl recoverle P / DGT mesured P) (L/kg) grouped y tretment level, mesued 3 (Bseline)-6, t four Oregon field sites. Regression equtions represent est fit line through ll of the dt points... 6 FIGURE. Log Kd mesured t four Oregon field sites. Ech yer represents composite of control nd tretment 1x smples only. Tretment x, nd 3x were omitted FIGURE 5. Log Kd-DGT mesured t four Oregon field sites. Ech yer represents composite of control nd tretment 1x smples only. Tretment x, nd 3x were omitted FIGURE 6. Nickel concentrtion (mg/kg) in surfce soil smpled t hrvest from four field sites in Oregon (n=) FIGURE 7. Nickel concentrtion (µg/l) in soil solution smpled t hrvest from four field sites in Oregon (n=) FIGURE 8. Nickel concentrtion (µg/l) mesured y DGT in soils from four field sites in Oregon (n=) FIGURE 9. Log Kd (totl recoverle Ni / soil solution Ni) (L/kg) grouped y tretment level, mesued 3 (Bseline)-6, t four Oregon field sites. Regression equtions represent est fit line through ll of the dt points... 7 FIGURE 3. Log Kd-DGT vlues for Ni t four Oregon griculturl field sites sed on rtios etween totl recoverle Ni in surfce soil nd DGT mesured Ni (n=) FIGURE 31. Log Kd mesured t four Oregon field sites. Ech yer represents composite of control nd tretment 1x smples only. Tretment x, nd 3x were omitted June 9, 7 5

6 FIGURE 3. Log Kd-DGT mesured t four Oregon field sites. Ech yer represents composite of control nd tretment 1x smples only. Tretment x, nd 3x were omitted FIGURE 33. Mercury concentrtions (µg/kg) in surfce soil smpled t hrvest from four field sites in Oregon (n=) FIGURE 3. Mercury concentrtions (µg/kg) in plnt tissue smpled from four field sites in Oregon (n=) FIGURE 35. Metl nd metlloid concentrtions in deep soil (mg/kg) mesured 3-6 t four field sites in Oregon (n=) June 9, 7 6

7 INTRODUCTION Mny commercilly ville fertilizers contin vrile levels of non-nutritive metls or metlloids such s rsenic (As), cdmium (Cd), led (P), nickel (Ni), nd mercury (Hg), rising from multiple sources including prent rock, or the use of wste products s fertilizer (1,). Recycling of wste is encourged y the EPA, to minimize output of toxins, including metls into the environment. Tilings cn contin vlule plnt nutrients such s zinc (Zn), phosphorus (P), nd potssium (K) tht cn e pckged nd sold s griculturl fertilizer. Consequently, metls cn e present in concentrtions greter thn prt per million levels nd my pose potentil risk. The mrket shre of wste derived fertilizer is unknown nd hs proven difficult to trck. The United Sttes rnks in the top five glolly for fertilizer importtion nd n estimted 53 million tons were used in the U.S. in 1- (3). In Ferury zinc fertilizer distriutor in Wshington upon inspection discovered, mg/kg cdmium in rw zinc sulfte mteril from Chin. Consequently, the compny ws forced to recll fertilizer from the mrket nd closed for severl months for fcility clen up. Worker exposure ws mjor concern nd the possiility remins tht the Zn sulfte ws deliertely contminted (). Investigtions in to the long term effect of pplying potentilly toxic, metl rich fertilizer to soils hve resulted in mixed nd conflicting conclusions (5) mking risk prmeteriztion difficult. Metl sorption y soil my e enhnced with the ddition of phosphtic fertilizers, which hve een found to decrese positive chrge, ut increse the ction exchnge cpcity (CEC) of soil (6). Soil ph cn decline with the ddition of fertilizer high in mmonium (NH + ) (7). Notle differences etween field nd greenhouse or continer June 9, 7 7

8 studies continue to excerte the difficult tsk for regultory gencies to set mximum tolerle limits for non-nutritive metls/metlloids in soils. Previous studies hve employed one time use of highly contminted soils to mesure metls. This leves unnswered questions out metl iovilility in griculturl settings where metl concentrtions re ssumed to e considerly lower. Mny studies used spiked soils, which hve een shown to hve consistently higher trnsfer rtes to plnts (8,9). In ddition, physicl nd chemicl properties my differ significntly in griculturl soils sujected to repetitive tilling nd irrigtion (1), potentilly ffecting metl iovilility over time. Potentil risks from metls in fertilizers hve een outlined (11) nd in development re soil screening criteri (USEPA) to estimte risk of soil metl contmintion to iot. Although mximum llowle concentrtions for metls in contminted soils exist, limits in non-contminted, griculturl soils hve yet een defined (1). Europen ntions oserve criticl limits of metls in oth contminted nd non-contminted soils (13). Potentil risks of repeted input of non-nutritive or toxic constituents from fertilizer include the potentil ccumultion nd incresed iovilility of metls in griculturl soils over time. Biovilility of metls is the ccessiility for iologicl ssimiltion nd possile toxicity. An increse in the iovilility of metls my led to enhnced plnt ssimiltion including the potentil for trnsport of metls into the edile portion of crops. Tolerle intke vlues of mny toxic metls from foods hve een recommended (1,15). Metls lso leve griculturl systems vi surficil wters nd leching nd my negtively impct djcent wter systems, posing potentil risk to qutic life nd to drinking wter qulity. The mjority of metl specition studies ssessing the June 9, 7 8

9 iovilility of metls in soil utilize one-step extrction methods, or modeling progrms such s the free ion ctivity model (FIAM)(16). Few studies hve nlyzed for the ioville frction of metls in griculturl soils. One pproch to cpture the reported ioville frction is the use of Diffusive Grdients in Thin Films (DGT), with which recent reserch hs demonstrted oth insight into the supply of metls from soils nd the potentil for use s physicl surrogtes for plnt/orgnism uptke. DGT is pssive smpling device developed nd used for quntittive determintion of lile metls in situ (17). Lile metl frctions re considered to e ioville from soil solution to iot. The focus of DGT is on the vilility of metls in soil systems rther thn on their mere presence. Prior studies hve pplied the use of DGT to mesure lile metl in soils (18-), nd DGT mesured lile metl hs een shown to more ccurtely reflect metl vilility to plnts thn mesurement of ion ctivities lone (1). The chelex 1 resin lyer used in the DGT device dsors mostly divlent nd some monovlent ctions (). Binding ffinities to the resin re metl specific nd re dependent on the ph, ionic strength, nd presence of other complexforming species. Chelex 1 will not redily ind rsenic due to the trivlent nd pentvlent sttes (As 3+, As 5+ ). Although chelex 1 hs high ffinity for mercury in the presence of nitrte ions, other competing ions, such s chloride, lower its ffinity to undetectle levels. We hypothesize tht DGT cptures the dose-dependent, fertilizer cdmium, nickel, nd led contriution in distinct griculturl systems. Secondly, DGT mesured metl is n effective indictor of the frction of metl ville for crop uptke. The ojectives of this three yer field study were: June 9, 7 9

10 1. Determine the ckground concentrtions of metls in distinct griculturl systems in Oregon.. Apply environmentlly relevnt tretment levels of commercilly ville phosphte fertilizer to four experimentl field plots over three yer period, using typicl griculturl prctices. 3. Determine the vilility of metls/metlloids to the edile portion of whet or potto crops nd the totl, dissolved, nd lile metl/metlloid concentrtions in soils.. Estimte the correltion etween DGT mesured lile metl nd metl concentrtion in the edile portion of whet nd potto crop. 5. Define the ioccumultion potentil from fertilizer input of metls/metlloids in griculturl systems over the three yer study. 6. Identify the rtes of chnge for metl concentrtions in distinct griculturl soils over time. EXPERIMENTAL SECTION Study re. Soils were collected from four field loctions in the stte of Oregon, USA (Figure 1). Smpling loctions represent distinct griculturl systems defined y differing climtes, soil clssifictions, crop rottions, nd gronomy prctices. Selected chrcteristics of the soils used in the study re presented in Tle 1. At ech smpling loction, n re of 11 m ws llocted nd divided into x rndomized grid consisting of four tretment (dose) levels (Figure ). June 9, 7 1

11 TABLE 1. Site specifictions nd selected properties of soils 3-6. Loction Soil clssifiction ph Mtter c % Orgnic CEC d (cmol/kg) P e µg/g K f µg/g NH -N g µg/g NO 3 -N h µg/g Irrigtion prctices Klmth Bsin Poe fine sndy lom irrigted Hermiston Adkins fine sndy lom irrigted Crop(s) grown summer whet/ potto winter whet/ potto Pendleton Wll Wll silt lom dry lnd winter whet Willmette Bsin Woodurn silt lom dry lnd winter whet Soil clssifiction ccording to the NRCS. Mesured using sturted pste; electrode method (ASA 1-.6). c Dichromte/HSO colorimetric method. d CEC=ction exchnge cpcity, mesured using mmonium cette EPA method 981. e ville P Colorimetric, ASA -3., N cette extrction f ville K AA, N cette extrction g Nitrogen-Ammoni: Colorimetric, ASA KCl Extrctle, ASA h Nitrte-N + Nitrite-N Colorimetric, ASA , KCl extrctle, ASA June 9, 7 11

12 Hermiston Pendleton Willmette Klmth FIGURE 1. Oregon field smpling loctions. June 9, 7 1

13 TABLE. Soil ckground concentrtions for five metls in Oregon soils nd Oregon Deprtment of Environmentl Qulity (ODEQ) ird/mmml screening levels soil concentrtions (mg metl / dry kg of soil). (Adpted from Curtis, L.R. nd Smith, B.W.,, ODA report) Pérez nd Anderson 7, in preprtion 1 Holmgren et l Boerngen nd Shckette, ODEQ Arsenic 3.8 N/A 6. 1/9 ( ) (.3-1.3) Cdmium.18.9 N/A 6/15 (.1-.3) Led / (.8-.3) (1-) Nickel /65 (1-18.) (7-3) Mercury.13 N/A /73 (.5-.3) (.-.6) N/A = not ville. 1. Vlues re rithmetic mens (rnge) for 16 ckground smples collected from fllow field sites t Oregon Stte University griculturl reserch sttions Klmth, Hermiston, Columi, nd Hyslop.. The vlues re geometric mens for 88 smples collected from northwestern, southcentrl nd southestern Oregon. 3. The vlues re rithmetic mens nd (rnges) for smples from Benton (1 site), Columi (1 site), Lincoln (1 site), Mrion ( sites), Multnomh (1 site), nd Tillmook ( sites) counties.. ODEQ soil screening levels from risk ssessments with rts (representtive mmml) nd roins (representtive ird). Soil tretment. Commercilly ville fertilizers known to contin more elevted concentrtions of As, Cd, P, Ni, nd Hg were used for field dosing. All phosphte fertilizers used in this study were purchsed y the Oregon Deprtment of Agriculture nd were ssumed to e representtive of phosphte fertilizers currently on the mrket. Appliction levels were ssigned sed on crop nd irrigtion prctice (3,). Tretment levels were control, using 1x typicl gronomicl ppliction of commercilly ville, non-metl rich fertilizer (16--/N-P-K); tretment level 1, June 9, 7 13

14 using 1x ppliction of commercilly ville metl rich fertilizer (1--); tretment level, using x ppliction of metl rich fertilizer; nd tretment level 3 using 3x ppliction of metl rich fertilizer (Tle 3). 5ft 1ft Control Replicte 1 Tretment #1 Replicte 1 Tretment # Replicte 1 Tretment #3 Replicte 1 Tret #3 Rep. Tret #1 Rep. Tret # Rep. Control Rep. Tret #3 Rep. 3 Tret # Rep. 3 Tret #1 Rep. 3 Control Rep. 3 Tret #1 Rep. Tret #3 Rep. Control Rep. Tret # Rep. Key SS: surfce soil DS: deep soil (once per yer) DGT: Diffusive Grdient in Thin-Film soil SF: soil fertility (once per yer) DS (1x/y) SS DGT SF (1x/y) SS SS DGT DGT FIGURE. Soil smpling scheme from ech of the four field sites. The control indictes 1x ppliction with non-metl rich fertilizer. Tretment indictes either 1x, x, or 3x ppliction with metl rich fertilizer. Within ech replicte 3 su-smples of surfce soil nd DGT soil were tken. Deep soil, lso composite of three su-smples, nd soil fertility were smpled once yer t hrvest. June 9, 7 1

15 TABLE 3. Mesured metl concentrtions in fertilizers 3-6 n=5 3/ /5 5/6 N-P-K-(S) mg/kg Control Tret Control Tret Control Tret As..8 < Cd.1 < P Ni Hg (µg/kg) SAMPLE COLLECTION Soils were collected twice nnully, post fertilizer ppliction llowing 6 dys incorportion, nd gin t crop hrvest pproximtely 5-1 months post fertilizer ppliction. Surfce soils. Surfce soils were collected from the rhizosphere (- cm) using stinless steel soil proes (AMS inc., Americn Flls, ID, USA), which smple n intct core. Within ech tretment replicte, composite of three cores were collected from distinct spots within the tretment plot re. This ws done to cpture field heterogeneity within ech tretment plot (Figure ). Overll, 16 surfce soil smples were tken ck to the lortory, ech of the 16 smples ws composite of 3 su-smples. Deep soils. Deep soils were collected once yer using gs powered uger to drill core of 3 m in depth. Only the control replicte 1, tretment 1 replicte 1, tretment replicte 1, nd tretment 3 replicte 1 were smpled. These correspond to one row of ech field plot t ll four sites (Figure ). In 3, deep soil core ws mde 1 over, 1 in from the top left corner of ech of the replicte 1 grids from the field plot. To prevent repeted smpling from the sme deep core loction in, the core drilling spot ws shifted over, in, followed y 3 y 3 in 5, nd y in 6. Stinless June 9, 7 15

16 steel proes were used to smple soil in triplicte from the 3 m hole. Deep soil smples were plced in clen gs for trnsport nd further processing. Diffusive Grdient in Thin Film soils. DGT soils were collected from the surfce horizon nd the rhizosphere (- cm). A composite of three su-smples were tken from ech tretment replicte to ccount for soil heterogeneity. Soils were kept intct (not dried or ground) to preserve the nturl iot of the soil. Rhizosphere microil communities re thought to contriute 65% of the totl orgnic cids from oth plnt nd microil contriutions (5) mking their role criticl in our efforts to relisticlly determine the iovilility of metls. DGT soils were plced in clen plstic gs, nd stored in < - C freezer until further nlysis. Side-y-side liquots were removed from the DGT soil to simultneous test for DGT mesured nd soil solution metl concentrtions. Plnt. Sixteen plnt smples were collected once yer t hrvest from ech of the sites. In 5, Pendleton ws fllow nd no plnt smples were tken. Whet smples were hrvested using mini-comine. By using the mini-comine, we were le to smple ech individul replicte from ll of the tretments. Aliquots were tken from ech of the 16 grin gs nd plced in plstic gs for trnsport nd nlysis. Pottoes were smpled using smll potto hrvesting mchine. Pottoes were pulled from the ground y the hrvester nd moved up slotted conveyor elt to help shke off deris. Twelve pottoes were rndomly smpled from ech tretment nd ech replicte, for totl of 19 (1 * 16) pottoes from one field site. Pottoes were stored in mesh gs for trnsport to the lortory. CHEMICAL ANALYSIS June 9, 7 16

17 Regents. Concentrted nitric (HNO 3 ) nd hydrochloric (HCl) cid, trce metl grde (Fisher Optim, Pittsurgh, PA); elementl stock stndrd solutions (Alf Aesr Specpure, Wrd Hill, MA); nd 18 MΩ cm wter (Brnsted, Duuque, IA, USA) were used. Certified reference mterils (CRMs) were purchsed from the Ntionl Institute of Stndrds nd Technology (NIST, Githersurg, MD, USA). Soil CRMs included 71 Montn Highly elevted soil, 711 Montn Modertely elevted soil, nd 79 Sn Joquin soil. For DGT nd soil solution nlysis, CRM 16 Nturl Wters ws utilized. Plnt CRMs included 1515 pple lef, nd 1573 tomto lef. Methods. Surfce soils were dried t 75 C for h, nd homogenized using coffee grinders (Tostmster corp., Menominee, MI, USA) with stinless steel ldes. Soil moisture content ws determined for ech site during the drying process. Totl recoverle metl concentrtion of surfce soils nd plnt smples ws determined using n cid digestion. An liquot of.5 ±.1 g of dried nd homogenized soil or plnt mtrix ws weighed out in to grduted kimx digestion tues (Kimle/Kontes, Vinelnd, New Jersey, USA). A mesurement of ml of concentrted HNO 3 ws immeditely dded to egin the digestion process. The soil or plnt mtrix digested t room temperture for pproximtely h in fume hood. After h, 1 ml of concentrted HNO 3 nd 1 ml of concentrted HCl were dded to ech digestion tue. Tues were plced on digest lock nd refluxed t incresing tempertures (, 6, 1 up to 15 C) until ornge NO x gses no longer formed. Typicl digest times were 1 h for soils nd 5 h for plnts. Following the digestion, the tues were cooled to room temperture, then diluted to 1 ml finl volume using 18 MΩ cm wter. All digest tues were vortexed nd filtered using.5µm PVDF (polyvinylidene difluoride) (Pll Corportion, Est June 9, 7 17

18 Hills, New York, USA) filter. Smples were nlyzed y inductively coupled plsm mss spectrometry (ICP-MS) (PQ ExCell, Thermo Elementl, Wlthm, MA, USA) s dpted from EPA methods 35B nd 7 (6). Soil su-smples, collected from the rhizosphere with stinless steel proes, were sent to the University of Idho Anlyticl Sciences Lortory (Moscow, ID, USA) nd nlyzed for moisture content nd generl fertility including ph, P, K, percent orgnic mtter (% O.M.), nitrte (NO 3 -N), mmonium (NH -N), nd CEC. A summry of these dt re shown in Tle 1. DGT deployment nd smple nlysis. DGT soils were rought to room temperture (1 C) prior to use. An liquot of ech soil (~5 g) ws weighed in duplicte nd plced in individul cid wshed plstic continers. Approprite quntities of 18 MΩ cm wter were dded to chieve 115% moisture level. Soils were stirred with glss rods, followed y h equilirtion prior to DGT deployment. Diffusive nd chelex gels were purchsed (DGT Reserch Ltd., Lncster, Lncshire, UK) nd ssemled ccording to Zhng nd Dvison (7,8) (Figure 3-). DGT units were deployed into the sturted soil slurry y pushing them elow the soil solution surfce t n ngle to prevent ir ules nd into the soil s previously descried (9). Continers were covered nd mintined t room temperture for 7 h. Previous experiments were conducted in l to determine the deployment durtion. We found tht 7 h provided mple time for the chelex resin to concentrte enough metl to e detected using ICP-MS (Eqution 1). To llevite ny concern out potentil depletion of metl from the soil within the 5 g smple cups, time trils were lso conducted, where DGT units were deployed for fixed times, 36, 8, 7 h. It ws found tht the time integrted June 9, 7 18

19 concentrtion of DGT mesured metl, ws identicl for ll deployment times (Eqution ). This informtion demonstrtes tht t ech griculturl field site, metls in the soil systems re constntly resupplied from soil solids, or ound sttes, in to soil solution. DGT units were retrieved from the soil nd rinsed with 18 MΩ cm wter to remove ny soil prticultes tht remined on the filter memrne. The resin gel ws removed nd plced into n cid clened plstic vil long with 1 ml of 1 N HNO 3 for h. Smples were diluted 1-fold nd nlyzed y ICP-MS. The mount of metl ccumulted on the resin gel per unit re ws clculted s: M = C eluent (V HNO3 + V gel )/f e (1) Where C eluent is the eluent concentrtion in µg/l, V HNO3 is the volume of 1N nitric cid used to extrct metl from the resin, V gel is the volume of the gel, f e is the elution fctor. To clculte the time integrted metl concentrtion in the DGT device (C DGT ), the following eqution is used: C DGT =M g/(dta) () Where M is the mss of metl ccumulted on the resin lyer; g is.93 cm, or the thickness of the diffusive gel lyer (~.8mm) plus the filter (~.13mm); D is the diffusion coefficient for ech metl t C from "Prcticl Guide to using DGT for Metl" (3); t is the deployment time, nd A is the exposure re of the chelex resin (3.1 cm ). June 9, 7 19

20 FIGURE 3. Diffusive Grdients Thinfilm (DGT) Processing from field to lortory nlysis. June 9, 7

21 FIGURE. Diffusive Grdient in Thin Film (DGT) deployed in soil solution. The mjority of metl in soil is ound to solid, with vrile rtes of relese. The frction of metl tht is relesed into solution, or lile metl, diffuses through the diffusive gel lyer nd is ound to the chelex resin. (dpted from Ernsterger et l., ES&T, ) Qulity Control. Qulity control (QC) consisted of oth field nd lortory components. QC smples comprise t lest 15% of ech nlyticl run. The field QC ws comprised of trip lnks, field lnks, nd rinste lnks. Rinste lnks were tken t ech smpling event from ech soil smpling tool utilized, including the trowel nd soil proes, s well s the luminum pns used for soil drying nd coffee grinders used for soil homogeniztion. The method detection limits for metls/metlloids in qulity control field wter smples re s follows: rsenic.35, cdmium.8, led.53, nickel 3.7 µg/l. Field QC wters were not nlyzed for mercury. Trip lnks nd rinste lnks were elow detection limits for ll metls/metlloids 3-6. Field lnks were elow detection limits for ll metls except led. Only the Hermiston site hd detectle led concentrtions in the field lnks. The verge led concentrtion in June 9, 7 1

22 Hermiston field lnks ws 3.81 µg/l (3 BDL, BDL, 5.63 ±.9, 6.98 ±.67 µg/l). Lortory QC consists of lnks, rinste lnks of l equipment, check stndrds, spikes, nd certified reference mterils. No lnk smples of 1% HNO 3 solution were ove detection limits (n=1), nor were the rinste lnks of lortory equipment used to process smples (n=). The verge percent recovery for ll check stndrds ws 96% (n= 63; As 95%, Cd 97%, P 97%, Ni 96%). Averge spike recoveries were 9% (n= 1). The verge percent recovery for ll certified reference mterils shown in Tle ws 11% (n= ; CRMs: 711, 17%; 79, 96%; 1515, 1%; 1573, 1%; 16, 11%). In house reference soil ws collected t the eginning of the project. Lrge quntities were dried nd ground for use in ech nlyticl tch to trck concentrtions over time. The verge concentrtions of metls in the in house reference soil were: As 3.8 ±.85, Cd.1 ±., P 6.6 ±.69, Ni.9 ±.1 mg/kg (n=16), Hg 15. ± 5.3 µg/kg. Irrigtion wters were smpled from sprinkler heds nd outdoor hoses from Klmth nd Hermiston sites (n=/site totl). Averge concentrtions of irrigtion wter re shown in Tle 5. June 9, 7

23 TABLE. Averge percent recovery of check stndrds, spikes nd certified reference mterils. % recovery check certified reference mteril stndrds spikes n As nd nd 91 Cd nd 1 1 P nd 117 Ni nd Hg * Hg n vlues: (CRM 79, n=61; 711, n=16; 1515, n=35; 1573, n=16) TABLE 5. Metl concentrtions in irrigtion wters from Hermiston nd Klmth field sites 3-6. Hermiston Klmth µg/l SD n ove MDL µg/l SD n ove MDL As Cd P Ni * Hg not tested M.D.L. = method detection limit DATA ANALYSIS For grphicl representtions, SigmPlot 3 for Windows, Version 8. (SPSS Inc., Chicgo IL, USA) ws used. Severl sttisticl nlysis methods were pplied to the dt. Multiple comprisons nlysis of vrince (ANOVA) ws used in tretment nlysis y Sigm Stt for Windows, Version 3.1 (Systt Softwre, Inc., Sn Jose, CA, USA). Yerly effects nd multivrite modeling were ddressed using multiple liner regression (MLR) with Sigm Stt. For simplistic modeling pproch, correltions etween metl/metlloid concentrtions in surfce soil, DGT, soil solution nd plnt were oserved. The soil fertility prmeters were lso included in the correltion nlysis. All June 9, 7 3

24 correltions were nlyzed using Person product moment correltion progrm y Sigm Stt. In order to tke in to ccount the effect of multiple prmeters on the metl/metlloid concentrtion response, rich model ws developed using multiple liner regression (MLR). Using MLR provides dt tht cn help nswer the question of whether continuous metl input from fertilizer incresed, decresed or hd no effect on the concentrtion of metl in the soil, soil solution or the lile frction s mesured y DGT over the three yer study period. By using MLR, other vriles tht potentilly my lter concentrtions of metl, prticulrly the ioville frction, could e ccounted for in the model. These vriles included P, K, NO 3 -N, NH -N, ph, % O.M., CEC, irrigtion prctices, nd the fertilizer lods to the soil ech yer. Fertilizer lods were clculted using the fertilizer ppliction rte, the volume of the plot using 1 till depth, which ccounted for the dilution of the fertilizer. The fertilizer ppliction rtes were derived from Oregon Stte University s Fertilizer Guide nd re specific for individul crops, soils, nd irrigtion prctices. From the dilution, totl metl lod ws clculted using the mesured metl concentrtions in the fertilizers for ech yer of the study. The lod (g/h/y) is used s the tretment vlue nd is lwys included in the MLR model (Figure 5-6). With this informtion out the lods, we cn determine if chnge in metl concentrtion over time is result of the input of fertilizer or is product of nother soil chemistry interction. If yerly effects were present, slope fctors from the MLR model were investigted to determine the rtes of chnge of metl concentrtions in soils over time. Significnce levels for ll sttisticl nlyses were set t P <.5. June 9, 7

25 Distriution coefficients were lso determined for metls in Oregon griculturl soils. Trditionl Kd vlues were clculted using the totl recoverle metl concentrtion in surfce soil divided y the concentrtion mesured in soil solution from rhizosphere soil smple (eqution 3). Totl recoverle [Me] / soil solution [Me] (3) Bio-distriution coefficients (Kd-dgt) were clculted s detiled in eqution. Totl recoverle [Me] / DGT mesured [Me] () The io-distriution coefficients re nother method to evlute the potentil for metl uptke into crops, or offsite movement of metl. One of the mny enefits of utilizing io-distriution coefficients is tht only the frction tht is truly in solution, or tht which is reported to e more representtive of crop uptke, is mesured. The Kd-dgt vlues reported in this study lso provide rel system dt, smpled t circumneutrl ph levels, t ctive griculturl sites. Trditionl Kd vlues rnge orders of mgnitude, re often determined in lortory settings, nd lter extrpolted to rel systems. With this dt we offer not only point of comprison to mssive ody of trditionl Kd literture, ut lso much sought fter ioville frction represented s distriution coefficient. A comprison of oth Kd nd Kd-dgst vlues for this study re listed in Tle 6 long with those mesured y Btes nd Shrp (3), nd Suve et l. (35). June 9, 7 5

26 TABLE 6. Distriution coefficients (log, 1) for metls in griculturl soils. Perez nd Anderson 1 Klmth Hermiston Pendleton Willmette Arsenic Cdmium Led Nickel Mercury K d-dgt N/A K d K d-dgt K d K d-dgt K d K d-dgt K d Btes nd Shrp K d N/A N/A Suve et l. 3 K d N/A = not ville 1. Rnges for Perez nd Anderson (7), in preprtion re for rnge of ph (.3 to 7. nd include control, tretment level 1x, x, nd 3x mesured t four griculturl sites in Oregon 3-6. Clssicl Kd vlues re clculted using totl recoverle surfce soil [Me]/soil solution [Me]. Kd-dgt vlues for Cd, P, nd Ni re clculted using totl recoverle surfce soil [Me]/Diffusive Grdient in Thin-Film [Me].. Rnges for Btes nd Shrp (1983) re for rnge of ph.5 to Suve (et l. ) specify their Kd vlues do not consider desorption potentil or iovilility of different metl species N/A N/A N/A N/A June 9, 7 6

27 g / h / y Arsenic Cdmium Led 15 Klmth C 1x x 3x C 1x x 3x Hermiston 1 C 1x x 3x C 1x x 3x Pendleton C 1x x 3x C 1x x 3x Nickel control tret 1x tret x tret 3x control tret 1x tret x tret 3x Mercury (mg) 5 6 C 1x x 3x C 1x x 3x C 1x x 3x Willmette 3 1 C 1x x 3x C 1x x 3x 8 6 control tret 1x tret x tret 3x C 1x x 3x C 1x x 3x C 1x x 3x. C 1x x 3x C 1x x 3x C 1x x 3x FIGURE 5. Fertilizer lods (g/h/y) for rsenic, cdmium, led, nickel nd mercury (mg) t four field sites in Oregon. E3- Bioville Metls Project-Oregon Stte University Klmth Fertilizer Appliction Rtes-Pottoes- Metl loding clcultions Klmth / Irrigted Spring Potto Plot Width Plot Length Totl Plot Squre Feet - Reps Pounds of N needed per cre Pounds of fertilizer pplied per plot ((ls N/356ft )*tot l plot ft ) Pounds of N pplied per plot (ls N pp./.1;.16) Pounds of P pplied per plot (ls P pp./;.1) plot volume (till depth 1ft) (ft 3 ) Dilution to fertilizer (ls/ft 3 ) Metl per ppliction (mg) Metl lods (mg/ft 3 ) Metl lods (mg/m 3 ) Metl lods (g/h) Control - Rep Cd Tret 1X - Rep Tret X - Rep Tret 3X - Rep Ni Fertilizer Concentrtions n=5 3/ /5 5/ NPK(S) mg/kg Control Tret Control Tret Control Tret P As..8 < Cd.1 < P Ni As Hg (µg/kg) Key: l= g 1 cre = 356 ft 1 cre= m Hg 1 ft 3 = m 3 1 plot = ft 1 l= g hectre =.715 cres 1 m = ft 1 ft 3 = m Hg results re 1x lower ug ug ug mg FIGURE 6. Dilution to fertilizer in griculturl soil exmple clcultions spredsheet for Klmth Flls experiment sttion sed on soil type nd crop grown. June 9, 7 7

28 RESULTS nd DISCUSSION Arsenic Arsenic in surfce soil. The men seline As concentrtion in surfce soil t ll four sites ws 3.77 mg/kg (Klmth 1.66 ±., Hermiston 3.1 ±.1, Pendleton 3.83 ±.1, Willmette 6.16 ±.9). The verge method detection limit for As in surfce soil ws.37 mg/kg (verge of 5 smple runs). Arsenic is lrgely immoile in griculturl soils nd tends to remin in the upper O nd A soil horizons (31). In generl, no tretment effects were oserved t ll fours sites during the study. At the Klmth, Hermiston, nd Pendleton experimentl plots, no significnt tretment effect ws oserved for surfce soil during the hrvest field smpling events in, 5, nd 6 sed on one wy nlysis of vrince (P >.5, 11 d.f.) (Figure 7). At Willmette, rsenic concentrtions for the nd 5 events were not significntly different etween tretments. A significnt tretment effect ws oserved for the 6 hrvest smpling event t Willmette where tretments 1x, x, nd 3x were significntly lower thn the control smples y.87,.77, 1.3 mg/kg less respectively (All pirwise multiple comprison procedures (Holm-Sidk method; P <.1). On verge, the tretment smples t Willmette in 6 contined.98 mg/kg less As thn the control smples. One fctor to consider is tht the ph t Willmette in 5 fell to less thn 5 (.7-5) nd in response, s per typicl gronomy prctice, the field ws limed prior to the 6 growing seson. The lime smples were elow detection limits for ll metls except P, which hd n verge of 1.6 ±.7 mg/kg. June 9, 7 8

29 .5 Klmth 6. Hermiston..5 totl recoverle As (mg/kg) Bseline 5 6 Bseline Control Tret 1x Tret x Tret 3x Pendleton Bseline Control Tret 1x Tret x Tret 3x Willmette 1.5. Bseline Control Tret 1x Tret x Tret 3x Bseline Control Tret 1x Tret x Tret 3x FIGURE 7. Arsenic concentrtions (mg/kg) in surfce soil smpled t hrvest from four field sites in Oregon (n=). June 9, 7 9

30 Arsenic concentrtions in surfce soil t Klmth, Hermiston, nd Willmette, did not correlte significntly with As concentrtions in soil solution or plnt. The only exception ws t Pendleton in 5, where surfce soil As did show negtive correltion with soil solution As (Person Product moment test, r = -.573, P =.). Using ckwrd stepwise regression, the following vriles were determined to e the most predictive of the surfce soil As concentrtion: ph, NH -N, NO 3 -N, K, irrigtion prctice, nd yer (P <.1 ll fctors). To determine whether As concentrtion incresed in surfce soil ech yer, ll sites nd tretments were held constnt in the MLR model. The djusted r for the model ws.71 with stndrd error of estimte.1. A yerly increse of surfce soil As ws seen t Klmth, ut no other site. In nd 6, surfce soil As ws not significntly different from the seline As concentrtion (P =.68,.7 respectively, n=). In 5, surfce soil As concentrtions were significntly greter thn those of seline (P =.1, n=). In, As ws significntly lower thn 5 nd 6 (P =.,. respectively, n=). Surfce soil As in 5 ws not significntly different from 6 (P =.65). The As concentrtions in the fertilizer for 5 were lso the highest of the study. Using MLR, it ws determined tht fter tking into ccount multiple other field vriles, the increse in As surfce soil concentrtions oth t Klmth ll yers, nd in 5 t ll other sites, could e ttriuted to the ddition of fertilizer. These results were nticipted s the As lods from the tretment fertilizer in 5 were fctor of 1 greter thn those in. The 5 As lods from the tretment fertilizer were 1% those from 6. Arsenic in soil solution. The men seline As concentrtion in soil solution t ll four sites ws.76 µg/l (Klmth 7.3 ±.3, Hermiston 3. ±.8, Pendleton.61 ±.8, June 9, 7 3

31 Willmette BDL). The verge method detection limit for As in soil solution ws.8 µg/l soil solution (verge of 8 smple runs). Soil solution As showed no significnt tretment effect t ll sites except Klmth. A significnt tretment effect ws oserved in, 5, nd 6 t the Klmth experimentl plots. Three yers dt resulted in qudrtic curves ech yer, which cnnot e dismissed s chnce (Figure 8). By fitting qudrtic eqution, r vlues of.93,.98,.99 were chieved for -6 respectively. One explntion is tht phosphte effectively competes with As for dsorption sites in soil (3,33). Excess P my hve resulted in the relese of solule As species nd susequent off site movement t the highest tretment level. No significnt tretment effect ws oserved t the Hermiston, Pendleton, nor Willmette field sites -6. Willmette soil solution smples from nd 5 were elow the method detection limit (BDL), while ll soil solution smples from Pendleton nd Willmette 6 were BDL. The est predictor of As in soil solution ws liner comintion of the vriles CEC, NH -N, NO 3 -N, K, nd irrigtion prctice (r =.85 ±.17; N=15). No significnt yerly increses were seen in soil solution As. Soil solution mesurements of As in nd 6 were not significntly different from seline. In 5, As soil solution concentrtions were mrginlly less thn the seline concentrtion y 1.5 ± 1.1 µg/l (P =.5). In -6, no significnt differences of soil solution As were seen etween yers. June 9, 7 31

32 1 1 Klmth Bseline Hermiston soil solution As (µg/l) Bseline Control Tret 1x Tret x Tret 3x Pendleton c c c c 3 1 Bseline Control Tret 1x Tret x Tret 3x Willmette mostly BDL -1 6 (BDL) -1 6 (BDL) Bseline Control Tret 1x Tret x Tret 3x Bseline Control Tret 1x Tret x Tret 3x FIGURE 8. Arsenic concentrtions (µg/l) in soil solution smpled t hrvest from four Oregon field sites (n=). June 9, 7 3

33 Arsenic in plnt. The verge method detection limit for As in plnt ws.8 mg/kg (verge of 3 smple runs). The edile portion of ll crops t ll sites in, 5, nd 6were elow detection limits for As. The Pendleton site ws fllow in 5. Arsenic could not e mesured using DGT. In generl, As in phosphtic fertilizers pplied t relevnt ppliction levels ws lrgely unville in griculturl field trils for uptke into whet nd potto crop. To define the ioccumultion potentil of As in griculturl soils in Oregon, Kd vlues were ssessed. The Kd tht is defined for As is the rtio etween totl recoverle As in surfce soil nd As in soil solution. Kd-dgt ws not determined for As. First, Kd vlues were plotted y tretment levels (Figure 9). The log Kd vlues for As t ll sites rnged from.-. L/kg. Trends showed negtive slopes t Hermiston nd Willmette, where Kd decresed with incresing tretment level, however no significnt differences were oserved etween tretment levels or etween yers. To determine n overll Kd trend for Oregon griculturl soils, only the control nd tretment level 1x were composited (Figure 1). This ws done to cpture the most relistic vlue for the distriution coefficient for As in Oregon soils, s x nd 3x pplictions of fertilizer re rrely reported. The slope fctor, or rte of chnge for As etween surfce soil nd soil solution over time is -.3 L/kg. A negtive slope indictes tht the rtio etween the totl recoverle [Me] nd the soil solution [Me] is ecoming smller over time. In other words, the frction of As in solution is incresing over time, rring no significnt chnges in surfce soil As concentrtions. This result suggests tht under the current field mngement prctices nd sed on the current model, Kd projected out 5 yers June 9, 7 33

34 would y considerly smller thn the Kds oserved 3-6 nd my result in more As in solution, ville for uptke into crops nd/or ville for offsite movement. June 9, 7 3

35 log Kd surfce soil/soil solution (L/kg) Log Kd (L/kg) totl recoverle/soil solution log Kd surfce soil/soil solution (L/kg) Klmth Bseline control T1x Tx T3x Pendleton 5 6 y = -.1x +.5 y = 6.9x Bseline control T1x Tx T3x log Kd surfce soil/soil solution (L/kg) log Kd surfce soil/soil solution (L/kg) Hermiston y = -.x +.97 Bseline control T1x Tx T3x Willmette y = -.9x +.16 Bseline control T1x Tx T3x FIGURE 9. Log Kd vlues for As t four Oregon griculturl field sites sed on rtios etween totl recoverle As in surfce soil nd As in soil solution (n=). June 9, 7 35

36 log Kd totl recoverle/soil solution (L/kg) Arsenic Klmth Hermiston Pendleton Willmette y = -.3x FIGURE 1. Log Kd mesured t four Oregon field sites. Ech yer represents composite of control nd tretment 1x smples only. Tretment x, nd 3x were omitted. June 9, 7 36

37 Cdmium Cdmium in surfce soil. The men seline Cd concentrtion in surfce soil t ll four sites ws.177 mg/kg (Klmth.11 ±., Hermiston.1 ±., Pendleton. ±.9, Willmette.19 ±.8 mg/kg). The verge method detection limit for Cd in surfce soil ws.6 mg/kg. Surfce soil Cd showed significnt tretment effect t ll sites, in prticulr, t two sites in 5, nd t ll sites in 6. At Klmth field site there ws significnt tretment effect for 6, ut no effect ws oserved in or 5 (Figure 11). Tretment levels 3x nd x hd.6 nd. mg/kg more Cd thn the control respectively (P =.,.3 respectively). There ws no significnt tretment effect t Hermiston in, ut 5-6 showed tht trets 3x nd x were significntly greter thn the control. Hermiston 5 tret x nd 3x were.9 nd.98 mg/kg greter thn the control (P =.,.6 respectively). In 6, tret 3x nd x were.6 nd.68 mg/kg greter thn the control (P =.,.1), while tret x ws lso significntly lrger thn tret 1x y.9 mg/kg (P =.8). Pendleton surfce soil Cd showed no significnt increses in nd 5. In 6, tret 3x nd x were significntly greter thn the control y., nd. mg/kg (P =.,.8). Surfce soil smples from Willmette -6 showed significnt Cd tretment effect. In, tret x hd n verge of.1 mg/kg more Cd thn the control (P =.). In 5, tret 3x ws significntly greter thn tret 1x nd the control y.1 nd.77 mg/kg (P <.8). In 6, trets 3x, x, nd 1x were ll significntly greter thn the control y.167,.7, nd.6 mg/kg respectively (P <.5). Tret 3x ws lso significntly lrger thn trets x nd 1x y.97,.13 mg/kg (P <.). June 9, 7 37

38 These results suggest tht Cd is eing retined in the soils, rther thn moving off site. The lrgest rtes of increse with tretment were seen t Willmette, site with one of the highest % O.M., ut with the lowest ph. Willmette soils lso received the highest fertilizer ppliction rtes of ll sites. However, this does not necessrily correspond to the incresed Cd concentrtions found in surfce soils. Pendleton soils received the lowest fertilizer ppliction rtes, yet hd comprle surfce soil Cd concentrtions to Willmette. Accumultion of Cd in Oregon griculturl soils ws further evidenced y significnt yerly increses of Cd t ll sites. No differences in surfce soil Cd concentrtion were seen etween irrigted nd dry lnd sites. Surfce soil Cd from Klmth did not correlte significntly with DGT, soil solution, or plnt mesured Cd in, nor in 5. Significnt positive correltion ws seen with surfce soil Cd in 6 with DGT nd soil solution Cd (r =.59,.6; P =.1,.1 respectively). Surfce soil Cd t Hermiston correlted well with Cd mesured in whet erries in (r =.6,.63; P =.7,.9 respectively), nd with DGT mesured Cd t Hermiston in 5 (r =.56; P =.). At Willmette, surfce soil Cd correlted significntly with plnt in nd 5 (r =.63,.6; P =.9,.), with soil solution in (r =.61; P =.1), nd strongly with DGT in 6 (r =.83; P =.1). Surfce soil Cd could est e predicted using liner comintion of the vriles CEC, % O.M., NO 3 -N, nd K (r =.77 ±.7; N=). After tking into ccount multiple field vriles using MLR, yerly increses in surfce soil Cd were seen t ll sites nd indicte potentil ccumultion in griculturl soils using Cd rich phosphtic fertilizers. Surfce soil Cd ws significntly greter in concentrtion in 5-6 compred to the seline Cd June 9, 7 38

39 concentrtion y n verge of 1.5 ± 1. µg Cd/kg soil (P <.1). In 5 nd 6, surfce soil Cd ws lso significntly greter in concentrtion thn in y 1.3 ± 1. µg/kg (P <.1). Although the verge surfce soil Cd in 6 is lrger thn in 5, the results re not sttisticlly significnt. In generl, there were positive slopes for the study durtion of incresing Cd concentrtions in surfce soil over time. June 9, 7 39

40 totl recoverle Cd (µg/kg) Klmth Bseline Pendleton Bseline 5 6* Control Tret 1x Tret x Tret 3x c c Hermiston Bseline 5* 6* Willmette Control Tret 1x Tret x Tret 3x c c c c 1 6* Bseline Control Tret 1x Tret x Tret 3x 1 * 5* 6* Bseline Control Tret 1x Tret x Tret 3x FIGURE 11. Cdmium concentrtions (µg/kg) in surfce soil smpled t hrvest from four field sites in Oregon (n=). June 9, 7