Anthropogenic contamination analyzed by TTPIXE in samples from the Odiel salt marsh at the SW Spain

An h opogenic con amina ion analyzed by TTPIXE in samples om he Odiel sal ma sh a he SW Spain J. E. Ma ín,* A. Ma ínez-Agui e,* M. A. Respaldiza,* M.F. da Sil a** *Depa amen o, de FAMN, Facul ad de F(sica, Uni e sidad. de Se illa, Apdo. 1065, 41080 Se illa, Spain **Depa amen o de Física, ITN. E. N. JO, 2685 Saca ém, Po ugal Toe s udied ma sh a ea is loca ed al he sou hwes o Spain in an es ua ine sys em onned by he con luence o he Odiel i e and he A lan ic ocean. 23 samples collec ed in he ma sh ha e been analysed by Thick Ta ge P o on lnduced X- ay Emission using 2 Me V p o ons om he 3 MV Van de G aa accele a o o he ITN. Elemen al concen a ions in he samples a e a ec ed, by he A lan ic ocean, he ma e ials anspo ed by he Odiel i e and he was es discha ged by he ac o ies o a neamy indus ial a ea. The s udy has shown ha ce ain a eas o he es ua y p esen high concen a ions o P, Cu, Zn, As and Pb, which we e a ibu ed o he ope a ion o a phospha e e ilize ac o y and a Cu ex ac ion ac o y. The mining ac i i y ca ied ou nea he sou ce o he i e could be also esponsible o pa o his con amina ion. Finally, he spa ial dis ibu ion o he con amina ion has e lec ed he dinamic o he Odiel i e wa e s, due o idal mo emen s, in o he ma sh a ea. In oduc ion Toe ma e ials anspo ed by he Odiel i e wa e s in o i s es ua y a e he esul o he ock-wea he ing and he biological ac i i y along i s basin. Toe p ocess o ock-wea he ing esul s in he in oduc ion o ce ain amoun s o mine al pa icles in o he wa e column. These pa icles will be anspo ed downs eam he i e su e ing a con inuous wea he ing along he i e basin. This wea he ing yields a wide ange in pa icle sizes and pa icles wi h di e en composi ion han hose o he o iginal ocks. Toe inal se o mine al ac ions: qua z, alumino-silica e mine als, Al, Fe and Mn hyd oxides, calci e, e c., e lec s he ock ypes and wea he ing condi ions along he i e basin.1 On he o he hand, he biological ac i i y in he i e in oduces in o he wa e column so ne biogenic pa icles: o ganic ma e , ca bona e and opal (amo phous Si02), which ha e been o med by o ganisms in he wa e o in he bo om o he i e .1 A he es ua ine a ea o he i e a la ge indus ial complex is loca ed, which is discha ging pa o i s was es in o he Odiel i e . These was es belong basically o RTM, a Cu ex ac ion ac o y and PESA, a ac o y which p oduces phospho ic acid o e ilize s. RTM ex ac s Cu om mine als ich in Cu by oxida ion ollowed by an elec oly ic Cu pu i ica ion. These mine als a e mainly Cu and Fe sulphides (30% Cu, 26% Fe, 29% S) which also con ain ce ain amoun s o Zn, As, Pb, Mg, qua z, Ca, Ag and Au. S is elimina ed by ixing S02 (gaseous) p oduced in he oxida ion p ocess as sul u ic acid. So ne ashes con aining As a e collec ed om he S02 cleaning.2 Fe is sepa a ed by using sand in he oxida ion p ocess p oducing ayali e [(FeO)iSi02]. Zn is inally con ained in a was e called "pucha" which is also o med in he oxida ion p ocess. Bo h, he ayali e and he pucha con ain so ne amoun s o o he elemen s and di e en compounds o S, Fe and Cu. Ag, Au and o he me als a e con ained in he inal mud. Toe o he ac o y, PESA, p ocesses phospha e ock, luo oapa i e [Ca10(PO,J6F2] wi h sulphu ic acid o p oduce phospho ic acid. Hyd o luo ic acid is one o he by-p oduc s o he eac ion and eac s wi h qua z impu i ies. Thus, F is inally eco e ed as luo osilicic acid H2SiF6. Ano he by-p oduc is phosphogypsum ( > 90% dyhid a ed gypsum, CaS04 • 2 i0), which also con ains la ge amoun s o impu i ies (qua z, luo ides, phospha es, o ganic ma e and Al and Fe mine als).2 Residual amoun s o phospho ic, sul u ic and luo ide acids can s ill e nain inside he phosphogypsum po osi ies. These acid esidues gi e he phosphogypsum acid na u e which allows o e ain ace elemen s om he o iginal ock in dissolu ion.2 This ac o y also p oduces sulphu ic acid o i s qwn consume, which is ex ac ed om py i e mine als (FeSi) ollowing a simila oxida ion and ixing p ocess ca ied ou in RTM. Pa o he was es emain in he acid esidual wa e s which a e eleased di ec ly in o he Odiel i e a i s es ua y. Howe e , mos o hese was es a e s o ed in unco e ed piles a he Tin o ma sh (see Fig. l). Thus, he Tin o i e is a ec ed by he Ieaching o di e en elemen s om hese unco e ed piles. 3 In addi ion o hese was es, uncon olled inpu s in he Odiel i e be ween he ac o ies4 and a ound Nue o Pue o ha bou (see Fig. 1) may occu du ing he unload o phospha e ock, py i e and o he aw goods. Finally, he idal ac ion ends o dis ibu e ali ma e ial eleased in o he es ua y, upwa d and downwa d be o e being de ini i ely deposi ed a he bo om o he es ua y o expulsed ou in o he ocean.1 Fu he mo e, he acid na u e o he Odiel i e , due o he py i e mining ac i i y and he discha ges om he ac o ies, ends o keep so ne ma e ials in dissolu ion. Toe mixing o hese acid wa e s wi h sea wa e p o okes a la ge p ecipi a ion o elemen s in he es ua y and, he consequen con amina ion o i s bank.1 A lan ic Ocean Fig. 1. Map o he es ua y onned by he Odie) and Tin o i e s a he A lan ic ocean loca ed nea he Huel a ci y (sou hwes e n Spain). I shows he sampling s a ions ac oss he Odiel ma sh as well as he loca ions o he phospha e e ili7.e ac o y (PESA) and he Cu ex ac ion ac o y (RTM) The con amina ion ha a ce ain a ca has su e ed may be e alua ed by de ennining i s en ichmen ac o index (EFI), de ined as he quo ien be ween he a io o he a e age concen a ion o such elemen o ha o Al and he same a io in a shale.1 By e alua ing he EFI o an elemen in a global a ea o in a sample, i is possible o cha ac e ize he global o indi idual con amina ion ha he a ea o he sample has been su e ing. The s udied a ea is pa o he es ua y ha he Odie! i e o os in i s con luence wi h he A lan ic ocean. l is a na u al ese a ion wi h high biological ac i i y, mainly composed by ou small islands c ossed by ou small channels. These channels a e, due o idal mo emen o he wa e s, highly a ec ed by he income o he Odie! i e wa e s. In a p e ious wo k,4 a clea con amina ion in P, S, Ca, Fe, Cu, Zn, As and Pb in bo om sedimen s collec ed a he es ua y o he Odie! i e we e ound. This pape p esen s an ex en ion o ha wo k o he Odie! ma sh loca ed along he Odie! i e opposi e o he indus ial discha ges. The main objec i e is o de e mine he ex en ha such con amina ion has o e all he es ua y. In las sense, global and indi idual EFI ha e been calcula ed in he samples collec ed in he a ea. Expe imen al Twen y su ace soil samples a he Odiel sal ma sh, opposi e o he ac o ies and 3 a he no hem ma sh si e a he en ance o he Odiel i e in he Huel a es ua y (see Fig. 1) we e collec ed. Toe samples we e aken du ing he Iow ide in a eas co e ed wi h wa e du ing he high ide. A ending o he geog aphical si ua ion (see Fig. 1), he samples a e classi ied in ou g oups: No hem ma sh (l-3), Odie! i e (15-18, 20-23), Moja e a channel (4, 13, 5, 7, 6, 8--10) and Pun a Umb ía i e . Each sample was desicca ed, homogenized and calcina ed (550 ºC) p io o analysis. A e calcina ing, so ne 0.1 � o sample was p essed (10 on) in o pelle s o 11 mm o diame e on a subs a e o 0.4-0.5 g o bo ic acid. These pelle s we e analyzed by TIPIXE using 2 Me V p o ons om he 3 MV Van de G aa accele a o o he I1N. 15° was used as he incoming p o on angle and 55° as he ou going X- ay angle, wi h espec o he no mal o he sample in bo h cases. An elec on gun was used o supp ess he cha ge build-up e ec s. Cha ac e is ic X- ays we e measu ed wi h a Si(Li) de ec o , wi h a esolu ion o Table 1. Si, Al, Ti and K concen a ions in he samples. Sampling poin s a e di ided in·o 4 g oups, om up o down: Nonhem ma sh, Odiel i e , Moja e a channel and Pun a Umb la i e . Numbe s in pa en heses e e o he e o o he las igu es Sampling poin No. Si,% Al,% l 21.80(6) 9.36(6) 2 15.15(5) 7.62(6) 3 13.59(5) 7.70(6) 23 16.93(5) 8.49(6) 22 35.00(7) 5.96(6) 21 38.75(6) 3.01(5) 20 21.06(5) 7.18(6) 18 12.84(4) 6.73(6) 17 26.05(6) 9.99(6) 16 13.69(5) 6.89(6) 15 25.35(6) 5.55(6) 13 15.23(5) 7.96(6) 4 14.95(5) 8.13(6) 5 17.00(5) 8.16(6) 7 19.45(5) 8.57(6) 6 20.50(5) 8.43(6) 8 17.38(5) 6.76(5) 9 22.29(5) 8.94(6) 10 19.04(5) 8.54(6) 12 27.89(5) 10.52 (6) 11 21.45(5) 7.94(6) 19 25.81(6) 7.59(6) 14 22.93(5) 7.83(6) 155 eV a 5.9 keV, connec ed o a mul ichannel analyze h ough a con en ional elec onic chain. Two uns we e made on each pelle , one wi h 10 nA in ensi y, o accumula e 2 µC cha ge, looking o ma ix elemen s and he o he one wi h 30 nA in ensi y, o accumula e 3 µC cha ge, bu pu ing a 1 mm plas ic il e in on o he Si(Li), looking o ace elemen s. The X- ay spec a we e i ed and he elemen al concen a ions ob ained using he GUPIX p og am.5 The esul s we e co ec ed by he con en s o o ganic ma e . The accu acy in he elemen al concen a ions was checked by analyzing e e ence sedimen samples (IAEA SL-1, NBS SRM 1646 & 2704). Resul s and discussion In Tables 1, 2 and 3 elemen al concen a ions in each sample a e p esen ed. By obse ing da a in Table 1, so ne di e ences be ween samples can be seen. In gene al, a di e ence in Si concen a ion is ollowed by a di e ence in Al concen a ion. Thus, mos o sa nples wi h high Si concen a ion ha e simila o highe Al concen a ion han hose sa nples wi h lowe Si concen a ion, gi ing, in gene al, Si/Al a ios be ween 2 and 3. Howe e , samples 15, 21 and 22 a e di e en s om he es o samples. These h ee sa nples ha e also high Si concen a ion, bu he co esponding Al concen a ions a e he lowes . These wo las esul s imply Si/Al a ios much highe han hose o he o he samples. Toe high Si concen a ion and Si/ Al a io in samples 15, 21 and 22, loca ed along he Odiel i e , could Si/Al Ti,% K,% 2.329(16) 0.500(6) 2.031(10) 1.988(18) 0.366(6) 1.459 (9) 1.765(16) 0.380(6) 1.395 (9) 1.994(16) 0.430(6) 1.676 (9) 5.87 (6) 0.330(5) 1.768(10) 12.87(22) 0.211(4) 1.214 (9) 2.93(3) 0.505(6) 1.607 (9) 1.908(17) 0.338(5) 1.307 (8) 2.608(16) 0.609(6) 2.619(11) 1.987(18) 0.415(5) 1.391 (8) 4.57 (5) 0.322(5) 1.588 (9) 1.913(15) 0.372(5) 1.546 (8) 1.839(15) 0.386(5) 1.612 (9) 2.083(17) 0.401(5) 1.824 (9) 2.270(16) 0.460(5) 1.951 (9) 2.432(19) 0.476(5) 1.972 (9) 2.571(21) 0.548(6) 2.028(10) 2.493(17) 0.479(6) 2.126(10) 2.230(18) 0.432(5) 1.871(9) 2.651(16) 0.577(6) 2.837 (9) 2.702(22) 0.525(6) 2.063(10) 3.40 (3) 0.554(6) 1.997(10) 2.928(23) 0.478(6) 2.031(10) be ela ed wi h he discha ges o ayali e om RTM ac o y. Howe e , a ending o he ayali e s oichiome y (Si02(FeO)i), he Fe concen a ion in hese samples should be ou imes highe han he Si concen a ion, i his is he eason o such di e ence wi h he es o samples. Fe concen a ion in Table 2 e eals ha Fe concen a ion in such sa nples is e en much lowe han he Si concen a ion. This esul may indica e a high p esence o sandy pa icles in hei composi ion. This las esul can be co obo a ed a ending o he o ganic con en o he samples. Thus, whe eas mos o samples ha e an o ganic con en anging om 10 o 15%, samples 15, 21 and 22 ha e only 4.6, 1.1 and 2.3% espec i ely o o ganic con en . Sa nples 1, 8, 12 and 17 ha e also di e en Si concen a ion, bu simila Si/Al a io han samples in hei su oundings. Toe low Si concen a ion o sample 8, wlilich has also a low Al concen a ion, could be ela ed wi h i s high Cl concen a ion o 9.87(2)% whe eas he es o he samples ha e Cl concen a ion below 1 %, excep ion being sample 11 wi h 2.61(1)%. A high amoun o NaCl p oduced by he e apo a ion o sea wa e could explain bo h, he high Cl con en and he deple ion in Si and Al. I he Cl con en is sub ac ed as NaCl and eno malizing o uni y he concen a ion o he es o elemen s, he new Si and Al concen a íon will be 20.76(5)% and 8.07(6)%, espec i ely. In his way, he concen a ion o Si and Al a e simila o hose in he su oundings (samples 6 and 9). Samples 1, 12 and 17, ha e Si, Al, K and Ti concen a ions highe han hei su ounding samples (see Table 1). Howe e , as can be seen in Tables 2 and 3, he Table 2. Same as Table I bu o Fe, S, Ca and P Sampling poin No. Fe,% S,% Ca,% P,% 11.70(3) 1.923(13) 0.869(10) 0.882(16) 2 14.18(4) 3.086(17) 1.939(12) 3.013(22) 3 13.96(4) 3.979(19) 2.141(13) 2.617(21) 23 12.34(3) 0.841(9) 0.927(9) 0.679(13) 22 8.31(3) 0.175(6) 0.981(10) 0.308(15) 21 3.357(20) 0.204(7) l.196(10) 0.262(18) 20 7.79(3) 1.275(11) 1.414(11) 1.069(16) 18 11.84(3) 1.370(11) 1.784(11) 2.693(19) 17 4.670(22) 0.142(6) 0.445(9) 0.014(12) 16 11.81(3) 1.401(11) 2.476(13) 2.599(20) 15 8.73(3) 1.023(11) 2.222(13) 2.057(21) 13 13.29(3) 0.784(8) 0.897(9) 0.744(13) 4 11.60(3) 2.534(15) 1.882(12) 2.247(19) 5 12.56(3) 1.027(10) 1.210(10) 1.110(15) 7 9.95(3) 0.934(9) 1.315(10) 1.140(15) 6 8.37(3) 1.060(10) 1.186(10) 0.818(14) 8 6.46(2) 1.032(10) 1.671(12) 0.228(11) 9 10.35(3) l.127(11) 1.424(11) 1.133(16) 10 15.04(4) 0.805(11) 0.671(9) 0.020(10) 12 6.582(20) l.271(10) 0.798(10) 0.074(14) 11 7.27(3) 1.402(12) 2.501(14) 0.663(15) 19 5.198(23) 1.139(11) 0.726(10) 0.225(14) 14 5.347(23) l.844(13) 0.728(10) 0.136(12) Table 3. Same as Table 1 bu o Cu, Zn, As and Pb Sampling poin No. Cu, ppm Zn,ppm As, ppm Pb, ppm 1 1340(30) 2320(40) 1270(50) 1470(170) 2 2000(40) 2900(60) 2070(80) 2300(300) 3 2710(50) 4650(70) 2080(80) 2700(300) 23 2151(21) 3550(30) 1070(30) I010(110) 22 563(17) 1750(30) 520(30) 350(100) 21 243(10) 810(20) 240(20) 160(70) 20 1504(25) 2090(30) 630(30) 730(110) 18 2392(30) 3600(50) 2500(60) 1910(250) 17 148 (5) 394(8) 56(6) 85(20) 16 2160(30) 3960(50) 2180(50) 1340(210) 15 1136(22) 2940(40) 1120(40) 600(140) 13 1467(25) 4210(50) 1390(40) 530(160) 4 2790(40) 4060(50) 1540(60) 2720(200) 5 1790(30) 4680(60) 1140(50) 1110(170) 7 1727(24) 3610(40) 1030(30) . 1210(130) 6 1325(20) 3180(40) 730(30) 630(100) 8 516(13) 1360(22) 277(16) 200(60) 9 1430(30) 4070(50) 870(40) 1050(130) 10 687(24) 5400(60) 770(40) 490(140) 12 523 (9) 1860(20) 143(9) 170(30) 11 1232(19) 3770(40) 534(23) 410(80) 19 654(17) 1920(30) 229(19) 310(60) 14 677(16) 1890(30) 251(17) 200(60) concen a ions o o he elemen s in hese samples a e he lowes . This ac indica es ha he a eas whe e hese samples we e collec ed a e somehow less a ec ed by he discha ges om he ac o ies. Being ali samples collec ed in a eas co e ed by wa e du ing he high ide, which p oduced he con amina ion, he esul indica es ha , p obably, hese samples a e less ime looded by he Odie! wa e s han he samples collec ed in hei su oundings. This seems o be specially ue in he case o sample 17, whose elemen al concen a ions seem o be he ypical ones in soils o an un looded ma sh. Table 4. A e age concen a ions and EFI o he analyzed elemen s in he Odie! ma sh (O, EFio), he no hem ma sh (N, EFIN) and ypical co nposi ion o a shale. Numbe s in pa en heses e e o he e o o he las igu es Elemen o N Shale EFI0EFIN Si, % 22(7) 17(4) 27.16 0.9(3) 0.62(16) Al,% 7.7(16) 8.2(10) 8.15 1 1 Ti,% 0.44(10) 0.42(7) 0.39 1.2(4) 1.07(22) K,% 1.9(4) 1.6(4) 2.69 0.75(22) 0.59(16) S,% 1.1(6) 3.0(10) 0.26 4(3) 11(4) Ca,% 1.3(6) 1.6(7) 2.22 0.6(3) 0.7(3) Fe,% 9(3) 13.3(14) 4.72 2.0(8) 2.8(5) P,% 0.9(9) 2.2(11) 0.074 13(13) 30(15) Cu,ppm 1300(800) 2000(700) 45 31(20) 44(16) Zn,ppm 3000(1400) 3300(1200) 95 33(17) 35(13) As, ppm 900(600) 1800(500) 13 70(50) 140(40) Pb, ppm 800(700) 2200(600) 20 40(40) 110(30) Table 5. Same as Table 4 bu EFI ela ed o sample 17 and composi ion o sample Elemen o N Si,% 22(7) 17(4) Al,% 7.7(16} 8.2(10) Ti,% 0.44(10) 0.42(7) K,% 1.9(4} 1.6(4) S,% 1.1(6) 3.0(10) Ca,% 1.3(6) 1.6(7) Fe,% 9(3) 13.3(14) P,% 0.9(9} 2.2(11) Cu,ppm 1300(800) 2000(700) Zn,ppm 3000(1400) 3300(1200) As,ppm 900(600) 1800(500) Pb,ppm 800(700) 2200(600) Tables 2 and 3 show ha , excep ing he samples abo e, he ma shes ( he Odiel and no hem ma sh) a e clea ly a ec ed by he discha ges om he indus ies. Toe no hem ma sh, he no h o he Moja e a channel and he eas side o he Sal és island, a e he a eas mo e a ec ed by such discha ges. Howe e , om he esul s, i seems clea ha he Pun a Umbóa i e is no a ec ed by he discha ges p oduced in o he Odiel i e . Cha ac e iza ion o he global con amina ion In Table 4, he a e age concen a ion and he global EFI o each analyzed elemen in he samples a e shown. Toe abo e alues ha e been de e mined sepa a ely o he Odiel ma sh (O) and he no hem ma sh (N). In he same able, he ypical concen a ion o hese elemen s in a shale6 a e, o compa ison, shown. Fo he i s ou elemen s in Table 4, Si, Al, Ti and K, i is clea ha he a e age concen a ion o hese elemen s in sapiples om bo h ma shes a e simila o hose in a shale; wi h EFI alues close o uni y, e ealing he na u al o igin o hese elemen s in he samples. In he case o Fe Sample 17 EFI0EFIN 26.05(6) 1.1(4) 0.80(21) 9.99(6) 1 1 0.609(6} 0.9(3) 0.84(17) 2.619(11) 0.9(3) 0.74(21) 0.142(6) 10(6) 26(9) 0.445(9) 3.8(19) 4.4(20) 4.670(22) 2.5(10) 3.5(6) 0.014(12) 80(110) 190(190) 148(5) 11(7) 16(6) 394(8) 10(5) 10(4) 56(6) 21(15) 39(13) 85(20) 12(11) 32(12) and S, bo h ma shes ha e a e age concen a ions clea ly abo e he concen a ion in a shale, wi h EFI alues abo e uni y in bo h cases and o bo h ma shes. Toe case o Ca is di e en . Toe concen a ion o his elemen in bo h ma shes is sligh ly lowe han in a shale, gi ing EFI alues below uni y in bo h cases, meaning ha he es ua y is deple ed in Ca espec o a shale. Fo he i e las elemen s: P, Cu, Zn, As and Pb, i is clea ha he esul s in Table 4, e lec a clea con amina ion o bo h ma shes by ali o hem. Bo h ma shes ha e concen a ions in hese elemen s much highe han in a shale and he EFI o each elemen is well abo e uni y. As i is well known, he concen a ion o an elemen in a sample depends s ongly on i s own mine al composi ion, which indeed depends on i s geog aphical loca ion. Thus, i seems mo e app op ia e o e alua e he EFI o each elemen by compa ing wi h an uncon amina ed sample o he same a ea. As i was commen ed p e iously, sample 17 seems o be he less a ec ed sample wi h elemen al concen a ions ha could be conside ed as he na u al le els in he a ea. In Table 5, he EFI alues o each elemen in bo h ma shes ela ed o sample 17 a e p esen ed. Toe EFI, close o uni y, e 40 30 :e: 20 • 10 .. a) • .. •• * .. • • • + + + ... • .. • .. o �- -T'""'T'-'-....... -- -...-, - - -........ --.-.,.....,-- -...-, - - -'-T- -T'""'T'- 1 2 3 2322 212018171815 13 4 5 7 8 8 910 12 11 1914 Sampllng poln s 5 4 3 ü ... !!;. 2 10 8 8 ¡; !:!. 2 o T * * : * .. • b) :11: .. • • - * . .. •• 1 2 3 2322 212018171815 13 4 5 7 8 8 9 10 12 111914 Sampllng poln s 1 2 3 23 22 21 20181716 15 13 4 5 7 6 8 9 10 12 1119 14 Sampllng poln s Fig. 2. EFI alues e alua ed in each sampling s a ion o S (a), Ca (b) and Fe (e) o Si. Ti and K, in Table 5 e lec ha bo h ma shes ha e concen a ions o hese elemen s ypical o he a ea Thus, i seems clea e now ha he e a e no an h opogenic discha ges o hese elemen s in he es ua,y. As í can be obse ed, he EFI o he es o elemen s is well abo e uni y, bu he e a e so ne di e ences e sus he EFI de e mined wi h he concen a ion o a shale. Now, he EFI o S, Ca and P a e highe han p e iously, and hose o he es o elemen s, excep ing Fe, a e lowe bu s ill being well abo e uni y. F om he esul s, i can be ex ac ed he high con amina ion o bo h ma shes by P, which is cohe en wi h he p esence o he e ilize indus ies. Mo eo e , he deple ion in Ca p e iously ound, has disappea ed and he esul s show a li le con amina ion o bo h ma shes by his elemen . Toe dec ease o he EFI o Cu, Zn, As and Pb, may be ela ed wi h he mine al composi ion o he ma shes, which a e s ill highly a ec ed by an h opogenic emíssíon o hese elemen s ín he a ea. Spa ial dis ibu ion o he con amina ion As i was men ioned p e iously, by de e mining he indi idual EFI o each sample i is possible o s udy he spa ial dis ibu ion o he con amina ion in he es ua y, which mus be ela ed o he Odie! wa e mo emen s in o he ma sh. In Figs 2a, 2b and 2c, he spa ial dis ibu ion o EFI o S, Ca and Fe, espec i ely, ela ed o sample 17, a e plo ed. Toe highes EFI o hese h ee elemen s a e ound in samples collec ed a he en ance o he Odiel i e in o he es ua y ( he no hem ma sh), a he eas side o he Sal és ísland and a he no h o he Moja e a channel. Toe spa ial dís ibu íon o EFI alues o he es o elemen s, P, Cu, Zn, As and Pb a e p esen ed in Figs 3a, 3b, 3c, 3d and 3e, espec i ely. Toe EFI o hese elemen s a e highe han hose o Ca and Fe, specially in he case o P, which ha e alues abo e 200 a he no hem ma sh and a he eas side o he Sal és island. Toe Pun a Umb ía i e shows gene ally he lowes EFI alues, excep ing sa nple 11. Fo ali elemen s, sa nple 4 has he highes EFI om ali samples collec ed a he Moja e a channel, alues ha dec ease downs eam he channel. This ac shows ha he no h o he Moja e a channel (see Fig. 1) is he main en ance o con amina ed Odiel wa e s in o he Odiel ma sh. Howe e , so ne con amina ion coming om he sou h o his island canno be conside ed as negligible. Toe 300 :, JC T][ 250 200 [ ¡¡: 150 w 100 •• • • • • •I * ISO a) • • • o 1 2 3 2322 21 2018171815 13 4 5 7 8 8 8 10 12111914 Sampllng poln s 20 15 ª 10 ¡¡: w *• 5 o 1 2 3 23 22 212018 1718 15 13 4 5 7 8 8 9 10 12111914 Sampllng poln s so 40 1I I 30 1 20 I I I 10 •> II o * 1 2 3 23 22 212018 171815 25 I 20 I 18 'S !:!. ¡¡: w 10 JI: 5 b) o 1 2 3 70 80 50 I!.. -40 ! i 30 ][ 20 10 d) o 1 2 3 I 1!I I ! I • I :a: JC I T • JI: -:e :a: I -- .. 2322 212018171815 13 4 5 7 8 8 1 10 Sampllng poln a + I i_ II I -:a: ][ : JC I II .. 23 22 212011171115 13 4 e 7 e a • 10 I II •I Sampllng polnlo 13 4 5 7 8 8 9 10 121119 14 - ** • 12 1118 14 X *'* .. 12 111914 sampllng polnls Fig. 3. Sa ne as Fig. 2. bu o P (a), Cu (b), Zn (e), As (d) and Pb (e) case o sample 8, wi h low EFI o ali elemen s, mus be ela ed, as was commen ed p e iously, wi h i s high con en in NaCI p oduced by he e apo a ion o sea wa e on he a ea. The e is a high and gene al con amina ion by P in ali he es ua y, wi h he highes EFI a he no hem ma sh and a he con luence o he Odiel and Tin o i e s (eas side o he Sal és island). FESA ac o y is, by idal mo emen s o he Odiel wa e s, esponsible o his con amina ion since bo h i e s do no anspo Pin hei wa e s. Mo eo e , since bo h RTM and FESA ac o ies con ain in hei was es pa o he o he elemen s wi h simila spa ial dis ibu ion o EFI o ha o P, i can be concluded ha hese ac o ies a e also esponsibles o he gene al con amina ion in S, Ca, Fe, Cu, Zn, As and Pb. Howe e , so ne inpu s o pollu an s, owed o he mining ac i i y a he sou ce o he Odiel i e , canno be disca ded as an addi ional sou ce o con a nina ion o he es ua y in hese elemen s, excep ing Ca Conclusions The p esen s udy e eals he high and gene al con amina ion ha he ope a ion o a Cu ex ac ion ac o y and a phospho ic acid ac o y, p oduce in he Odiel and in he no hem ma shes loca ed a he Huel a es ua y, a he sou hwes o Spain. This con amina ion is p oduced by he idal mo emen s o he Odiel i e wa e s in he es ua y which ecei es di ec ly pa o he was es discha ged om he ac o ies. F om ali analyzed elemen s, P has he highes EFI alues in ali he es ua y. Indeed, EFI alues abo e 200 ha e been ound in ce ain a eas o he ma sh. Fu he mo e, he no hem ma sh, he no h o he Moja e a channel and he eas side o Sal és island, seem o be he a eas mo e a ec ed by he pollu an s eleased by he indus ies. The conclusions a e in acco dance wi h a p e ious s udy o he adioac i e con amina ion in he same ma shes.7 * lbis wo k has been suppo ed by ENRESA unde a 1 + D con ac . We a e g a e ul o Isabel GARc A-ÜRELLANA, Raúl PERIAJilEZ and José D!Az o helping in he sampling wo k. J. E. M. acknowledges he help and kind hospi ali y gi en by he Van de G aa accele a o s a om ITN, specially he PIXE se -up calib a ion and help om Luis CERQUEIRA. Re e ences l. U. FORSTNER, G. T. W. W ITMANN, Me al Pollu ion in he Aqua ic En i onmen , Sp inge -Ve lag, Be lín, Heidelbe g, New Yo k, Tokyo, 1983. 2. P.M. RUTHEFORD, M. J. DUDAS, R. A. SAMBK, Sci. To al En i on., 149 (1994) l. 3. J. E. MARTIN, J. P. Boú AR, M. A. REsPALDIZA, R. GARclA-'J'ENORIO, M.F. DA Sil.VA, Nucl. lns . Me h., B 103 (1995) 477. 4. J. E. MARTlN, M. A. REsPALDIZA, R. GARclA-TENORIO, J. P. Boú AR, J. GóMEZ-CAMA no, M. F. DA Sil.VA, Nucl. lns . Me h., B 109/110 (1996) 506. 5. J. A. MAXWELL, J. L. CAMPBEU., W. J. TEEsnALE, Nucl. lns . Me h., B 43 (1989) 218; B 95 (1995) 407. 6. K. K. TuREKIAN, K. H. WEDEPOHL, Bull. Geol. Soc. Am., 72 (1%1) 172. 7. A. MARTINEZ-AGUIRRE, M. GARciA-LEóN, J. En i on. Radioac , 34 (1997) 45.