The distribution of U, Th and 226Ra derived from the phosphate fertilizer industries on an estuarine system in Southwest Spain

The Dis ibu ion o U, Th and 226Ra De i ed om he Phospha e Fe ilize Indus ies on an Es ua ine Sys em in Sou hwes Spain A. Ma ínez-Agui e, M. Ga cía-León Facul ad de Física, Uni e sidad de Se illa, Apa ado 1065. 41080 Se illa, Spain & M. I ano ich AEA En i onmen and Ene gy, Ha well Labo a o y, Oxon OXI 1 ORA. UK ABSTRACT This pape epo s an ex ensi e s udy o he p esence o na u al adioac i i y a ound a phospha e e ilize ac o y complex sí ua ed in an es ua ine a ea o sou hwes Spain. The s udy has concluded ha he was es om such indus ies a e he cause o he enhancemen o na u al adioac i i y in he immedia e en i onmen . Thus, signi ican ly high le els o U- and Th-iso opes and 226 Ra a e de ec ed in wa e and sedimen samples collec ed in his a ea. These conclusions based on he enhanced iso opic concen a ions a e u he suppo ed by he measu ed U, Th and Ra iso opic ac i i y a ios being qui e di e en om any obse ed e sewhe e in undis u bed es ua ies. These iso ope ac i i y a ios appea o be e y sensi i e indica o s o was e disposal p ac ices in such en i onmen s. INTRODUCTION Recen ly, se e a! s udies ha e been ca ied ou in he icini y o phospha e e ilize indus ies in a de o es ablish he signi icance o he adiological impac o hei ope a ions on he en i onmen as well as on he human popula ion (S ain, 1979; Van de Heidje e al., 1988; Kos e e al., 1991; Ma ínez-Agui e & Ga cía-León, 1991a). While ypical ocks con ain on a e age so ne 2·8 ppm o U (UNSCEAR, 1977), a phospha e ock can con ain up o 50-300 ppm o U (Gascoyne, 1982). The Eu opean Communi y impo s annually so ne 15-17 MT o phospha e ock (Baes slé, 1991 ). The impo ed ma e ial is p ocessed in o di e en p oduc s gene a ing was es such as phosphogypsum. Each yea 6-7 MT o phosphogypsum is discha ged di ec ly in o he sea, and, in addi ion, so ne 8-11 MT is deposi ed as so lid was es in piles (Baes slé, 1991 ). These piles emain unp o ec ed om ainwa e , wind and o he elemen s, and hus hey could be connec ed hyd aulically o su ace o g oundwa e s as a po en ial sou ce o con amina ion. The phosphogypsum is mainly composed o CaS04. This means ha i also con ains U, Th and Ra in la ge quan i ies as a esul o co-p ecipi a ion wi h Ca du ing he p ocess o e ilize p oduc ion. I is he e o e possible ha na u al p ocesses could lead o he edis ibu ion o hese na u al adionuclides in o he en i onmen su ounding he was e disposal si es. S ain ( 1979) ound a signi ican inc ease o Ra ac i i ies in g ound wa e s collec ed a ound a e ilize ac o y a No h Ca olina, USA. So ne o he wo ke s (Van de Heidje e al., 1988; Kos e e al., 1991) ha e also s udied he p esence o na u al adioac i i y, mainly 226Ra and 21 ºPo, in Eu opean en i onmen s a ec ed by such indus ies. Also, Paul e al. (1980) in es iga ed signi ican ly high 226Ra concen a ions in phosphogypsum a Ke ala, India. Recen ly, Ma ínez-Agui e and Ga cía-León (1991a) ound anoma lously high U-iso ope ac i i ies in wa e and sedimen samples collec ed a he Odie! and Tin o i e s in sou hwes Spain (Figs 1 and 2). Such enhancemen s we e a ibu ed o an indus ial complex su ounded by hese i e s in which wo phospha e e ilize ac o ies we e loca ed. One ac o y p ocesses a ound 1-4 MT pe yea o phospha e ock om Mo occo, while he o he uses a ound 0·2 MT o ock om Mo occo, Senegal and Togo. Bo h ac o ies elease hei was es di ec ly o he Odie! i e o a e s o ed in unco e ed piles ( he a ea ma ked wi h s a s in Fig. 2). U sing he da a gi en by Guimond and Ha din (1989) o phospha e ock om Mo occo, he i s ac o y alone may p oduce a ound 2-2 TBq o 226Ra, 2-3 TBq o 238U and 1 -4 TBq o 232Th each yea . Pa o his ac i i y can ob iously be edis ibu ed o e he en i onmen ha su ounds he indus ial complex. This pape ep esen s a mo e comple e s udy o possible edis ibu ion o he adioac i i y om he was es gene a ed by he abo e phospha e e ilize ac o ies. To his pu pose iso opes o U and Th and 226Ra ha e been ex ac ed and de e mined om di e en su ace wa e and sedimen Medi e anean sea Fig. l. Map o Spain showing he s udied a ea in he Andalousian egion. collec ed du ing 1989. The adionuclide concen a ions in hese samples and he co esponding ac i i y a ios, which e lec he daugh e s mobili y, and p obably, also he o igin o he adionuclides, will be used o in es iga e he dis ibu ion o adioac i i y o e his a ea o sou hwes e n Spain. SAMPLING AND EXPERIMENTAL METHODS Samples o i e wa e and sedimen we e collec ed along he Odiel and Tin o i e basins (Fig. 2) du ing July 1989. Su ace wa e samples o 7-1 O l we e collec ed in plas ic bo les du ing low ide, and pH and empe a u e (ºC) we e measu ed a he same ime. The suspended ma e was sepa a ed as soon as possible using 0-45 µm po e size Nuclepo e il e s. I has been p ese ed o u u e analysis, since i could p o ide in e es ing addi ional in o ma ion. Then, he il a e was acidi ied o pH ""2 by concen a ed HN03, o a oid he g ow h o mic oo ganisms and o minimize wa e /wall in e ac ions. A he same ime, bo om sedimen s we e collec ed. Samples o abou 1 kg we e collec ed and s o ed in plas ic bags. Then, in he labo a o y, sub-samples we e d ied and powde ed be o e analysis. The ex ac ion me hod used o U- and Th-iso ope sepa a e is gi en in ® Piles o phosphogypsum O 3km L____J__j Fig. 2. Map o Odiel and Tin o i e s showing he sampling s a ions in 1989. I ano ich and Mu ay (1992) and Ma ínez-Agui e (1991). Only a b ie desc ip ion is gi en he e. A e homogeniza ion, a ew g ams o d y sedimen , spiked wi h known quan i ies o 236U and 229Th s anda d solu ions o chemical yield de e mina ions, a e diges ed wi h HN03, aqua egia, HC104 and HF. The esidue le a e he abo e ea men is dissol ed in 7M HN03. The U and Th a e co-p ecipi a ed wi h Fe3+ by adding concen a ed ammonia o he solu ion. The U- and Th-iso opes a e i s sepa a ed by using anion exchange esins (Dowex AG 1 X 8 hyd ochlo ic o m) condi ioned wi h 8M HCl. Then each ac ion is u he pu i ied by he emo al o Fe whose p esence would a ec he .x spec al esolu ion. Fo his las pu i ica ion s ep he esins in he sepa a ion columns a e condi ioned wi h 7M HN03. These pu i ied solu ions a e d ied and U and Th a e elec opla ed on o s ainless s eel planche s using he p ocedu e o Lally and Eakins (1978). The ac i i ies a e de e mined by a-spec ome y using su ace ba ie Si a-de ec o s. In he case o wa e samples, so ne 7-101 o wa e a e spiked wi h 236U and 229Th s anda d solu ions and hen boiled down o app oxima ely 11. The U and Th con en is hen co-p ecipi a ed wi h Fe3 + by he addi ion o (NH)40H. The p ecipi a e, a e sepa a ion om supe na e by con i uging, is dissol ed by 7M HN03. Finally, he same p ocedu e, desc ibed abo e o diges ed solid samples, is ollowed. Fo he 226Ra analysis in sedimen samples, he 222Rn emana ion me hod was used. The samples a e i s diges ed wi h HN03, aqua egia, HC104 and HF and hen he esidue is dissol ed wi h 8M HCl and he olume made up o 0-51. The solu ion is hen ans e ed in o a sealed glass bo le and he o iginal c op o 222Rn expelled by bubbling ul apu e He gas h ough. A e app oxima ely h ee weeks secula equilib ium be ween a new c op o 222Rn and 226 Ra in solu ion is eached. The 222Rn is again expelled and collec ed in a ZnOz-lined qua z coun ing cell. The 222Rn ac i i y is measu ed by a gas scin illa ion coun e and om i he 226Ra concen a ion in he sample is de e mined (I ano ich & Mu ay, 1992). RESULTS AND DISCUSSION As al eady s a ed, he indus ial zone unde s udy is si ua ed on a ongue o land su ounded by he i e s Odiel and Tin o, wi h hei con luence a i s ip (Fig. 2). The wo i e s a e a ec ed di e en ly by he indus ial ac i i y. Consequen ly, he p esen a ion and he discussion o he esul s will be ca ied ou sepa a ely o each i e . In he ables and igu es he au ho s ha e deno ed wi h 'O' and 'SO' he wa e and sedimen samples, espec i ely, om he Odie! i e . Simila ly, o he Tin o i e samples, p e ix le e 'T' and 'ST' ha e been used. P e ix le e s 'OT' and 'SOT' co espond o samples de i ed om he con luence o he wo i e s which o ms a common mou h o he A lan ic Ocean. The numbe s gi en o each sample iden i y he sampling s a ion (Fig. 2). In addi ion o he U and Th iso opic ac i i ies exp essed in mBq/1 ( o wa e samples) o mBq/g ( o sedimen samples), U and Th mass concen a ions a e also gi en in µg/1 o µg/g. The wo a e ela ed by he ollowing con e sion o mulae: [U] = 0-08 l lA23s [Th] = 0-2436A232 (1) (2) whe e [U] and [Th] a e he mass concen a ions and A238 and A232 a e he ac i i ies o 238U and 232Th, espec i ely. Odiel i e The sampling s a ions a e dis ibu ed along he lowe eaches o he i e close o he indus ial zone a ea (Fig. 2). The excep ion is s a ion 1 which is si ua ed a ups eam o his a ea close o he i e sou ce. Wa e The U- and Th-iso ope ac i i ies a e gi en in Table 1 oge he wi h pH alues. I is appa en ha all adionuclides measu ed in he collec ed wa e TABLE 1 U- and Th-Iso ope Ac i i ies (m/Bq/1) and pH o Wa e Samples Taken Along he Odiel Ri e 238Th Sample pH 23su 234u 232Th 230Th 01 3-01 197·9 ± 6·8 316-3 ± 10-7 13-4 ± 0-6 49.7 ± 1-7 22-9 ± 0-9 02 7-40 34-2 ± 1-1 36-3±1-2 0-58 ± 0-30 7-02 ± 1-33 2-65 ± 0-78 03 7-20 33·0 ± 2-0 35-0 ± 2-1 1-81 ± 0-14 12-0 ± 0-5 NM NM 04 7-12 54·1 ± 3.4 58-7 ± 3.7 2-21 ± 0-24 14-3 ± 0-7 05 7-08 52·7 ± 3-6 54.3 ± 3.7 2-51 ± 0-25 18-9±1-3 7-52 ± 1-20 8-83 ± 2-89 2-38±0-15 06 6-80 131-3±11-3 136-2± 11-7 4.73 ± 0-67 34-2 ± 3.3 07 6-96 35-8 ± 0-9 39-2 ± 0-9 1-83±0-12 11-2±0-4 NM, No measu ed. sample ollow he same dis ibu ion pa e n along he i e wi h wo well de ined peaks. The iso opic da a ob ained o sample O 1 a e anomalous ela i e o he es o he da a se . The e y low pH alue o 3, due o local geology condi ions, accoun s o he obse ed enhanced concen a ion lis ed. The head wa e s o i e Odiel a e chemically agg essi e, esul ing in e ec i e leaching and ans e o U and Th om he solid o he aqueous phase o he sys em. The Th iso opes, mainly insoluble in na u al wa e s, ha e concen a ions a leas one o de o magni ude highe han in a e age su ace wa e s (Ma ínez-Agui e & Ga cía-León, 1992; Osmond & l ano ich, 1992), e lec ing he highe mobili y o Th a e y low pH alues. Highe concen a ions o U- and Th-iso opes also pe sis downs eam be ween sampling s a ions 04 and 06, wi h a clea peak o ac i i y a sampling s a ion 06. A simila pa e n was obse ed o U-iso opes in samples collec ed in 1988 (Ma ínez-Agui e & Ga cía-León, 1991a). The obse ed pa e n is indica i e o he exis ence o a local sou ce be ween s a ions 04 and 06. The ob ious candida e o his local sou ce o adioac i i y has o be ela ed o he phospha e manu ac u ing complex loca ed be ween s a ions 04 and 05. The obse ed shi in he loca ion o he peak o ac i i y om s a ions 05 and 06 in he wo sampling campaigns is a esul o a lowe idal inpu and a highe ac i i y inpu (highe was e ou pu om he phospha e ac o ies) o he i e a he ime o sampling. This si ua ion was encoun e ed du ing he 1988 sampling campaign when he ac i i y peak was obse ed highe ups eam a s a ion 05 (Ma ínez Agui e & Ga cía-León, 1991a). Table 2 p esen s he U and Th con en s o he wa e s collec ed in he Odiel i e , and he co esponding Th/U mass a io oge he wi h he 234U /238U, 23ºTh/234U and 228 Th/232 Th ac i i y a ios. In Fig. 3, U and Th concen a ions along he i e channel a e shown. The Th/U a ios ound a e consis en wi h he well known ac o highe end o Th o be associa ed wi h he solid phase in i e s. On he o he hand, such esul s a e highe han no mally encoun e ed in mos i e wa e s (Osmond & I ano ich, 1992) sampled ups eam om he es ua y. These esul s, howe e , a e qui e simila o he mass a ios ob ained o he es ua ine wa e s o he Guadalqui i i e (Ma ínez-Agui e, 1991; Ma ínez Agui e & Ga cía-León, 1992). The 234U/238U ac i i y a ios epo ed in Table 2 a e unusually low o a i e sys em. A weigh ed a e age o he da a o s a ions 02 o 07 is 1-07 ± 0-02. This alue is mo e ypical o a p ima y mine al ac i i y a io om a e ilize manu ac u ing p ocess han he a e age disequilib ium obse ed in i e s (Sco , 1982). Sample 01 is clea ly a di e en case. I s low pH p omo es he dissolu ion TABLE 2 U and Th Concen a ions (µg/1), Th/U Mass Ra io and Iso opic Ac i i y Ra ios in Wa e Samples Taken Along he Odie! Ri e Sample [U] [Th] Th/U 214u¡21su210Th/214U21sTh/212Th 01 ¡5.9 ± 0·6 3·31±0·15 0·208 ± 0·012 1·60 ± 0,02 0· 157 ± 0·008 1·70 ± 0·07 02 2.75 ± 0·09 0· 145 ± 0·075 0,053 ± 0·027 1,06 ± 0,03 0•71 ± 0-21 4-51 ± 2-49 03 2-68 ± 0-16 0-447 ± 0-035 0-167 ± 0,017 1-07 ± 0-02 0-34 ± 0-03 04 4.39 ± 0-30 0-546 ± 0-059 0,134 ± 0-017 1-08±0-10 0-24 ± 0-02 os 4·28 ± 0-29 0-620 ± 0-061 0-151 ± 0-018 1-02 ± 0-09 0-37 ± 0-04 3-00 ± 0-25 06 10-7 ± 0-9 ¡ .¡7 ± 0-16 0-110 ± 0-018 1-04 ± 0-04 0-25 ± 0-03 1-87 ± 0-67 07 2-88 ± 0-07 0-450 ± 0-029 0-157±0,011 1-10 ± 0-02 0-29 ± 0-01 1-31±0-11 (a) ú) úJ 02 03 04 05 06 07 (b) -a- o J � � ··� 01 02 03 04 05 06 C1l OT1 Fig. 3. U concen a ion (a) and Th concen a ion (b) in µg/1 in wa e samples along he Odie! i e . o U-iso ope ac i i ies om he solid phase o he i e sys em. In such condi ions, he 234 U-iso ope is p e e en ially mobilized, esul ing in 234U en ichmen in he aqueous phase ela i e o 238U (Gascoyne, 1982) and hence he highe 234U /238U ac i i y a io obse ed in sample O l. The 23ºTh/234U ac i i y a ios epo ed in Table 2 a e anomalously high when compa ed wi h o he i e sys ems. Thus, ypical ac i i y a ios o i e wa e s a e a ound Ü· l o less (Pla e e al., 1992; Ma ínez-Agui e & Ga cía-León, 1992). In he p esen case he weigh ed a e age 23ºTh/234 U (a) T1 T2 T3 T4 Ts Ts (b) ID ú) o -·� j T1 " .2 T3 T4 Ts Ts OT1 OT2 Fig. 4. U concen a ion (a) and Th concen a ion (b) in µg/1 in wa e samples along he Tin o i e . The ma e ial discha ged a s a ions 2 and 4 mus also con ain U. The ac ha enhanced le els o U ha e no been obse ed is p obably ela ed o he di e en ial mobili ies o Th and U in aqueous sys ems. The U being much mo e mobile han Th, i will end o edis ibu e mo e apidly in he mass o wa e along he i e channel, esul ing in a smoo he dis ibu ion pa e n, compa ed o Th which will be inco po a ed o he solid pa icles e y as . The iso ope ac i i y a ios p esen ed in Table 6 o s a ions 2 and 4 may help o suppo his p oposi ion. TABLE 6 U and Th Concen a ions (µg/1), Th/U Mass Ra ios and Iso opic Ac i i y Ra ios in Wa e Samples Along he Tin o Ri e 234u¡2Jsu 230Th/234U22sTh/232Th 230Th/232Th Sample [U} [Th} Th/U TI 9-26 ± 0-32 4-82 ± 0-23 0-521 ± 0-031 1-83 ± 0-03 0-25 ± 0-01 3-60 ± 0-12 2-67 ± 0-09 T2 3-20±0-15 11-8±3,6 3-69±1·13 1-07 ± 0-04 2-14 ±0-64 0-27 ± 0-05 1-90±0-21 T3 3-82 ± 0-18 0-193 ± 0-028 0-050 ± 0-006 1-09 ± 0-04 0-11±0-01 1-27 ± 0-22 7-2 ± 0-8 T4 3-87±0-19 5.33 ± 1-21 1-38 ± 0-32 1-11 ± 0-04 0-77±0-17 0-10 ± 0-03 1-90 ± 0-21 T5 3-42 ± 0-08 0-136 ± 0-024 0-040 ± 0-007 1-08 ± 0-02 0-085 ± 0-007 7.1 ±0·3 T6 3-68±0-12 0-155 ± 0-015 0·042 ± 0-004 1-08 ± 0-03 0-077 ± 0-004 1-09 ± 0-17 6-0 ± 0-6 OT1 3.97 ± 0-11 0-135 ± 0-016 0-034 ± 0-004 1-09 ± 0-02 0-060 ± 0-004 0-91 ± 0·18 5.9 ± 0-7 OT2 2-80 ± 0-16 0-021 ± 0-008 0-008 ± 0-003 1-11 ± 0-05 0-016 ± 0-002 7.4 ± 2-8 The weigh a e age o he 234U /238U ac i i y a io o 1-09 ± 0-02 ( excluding sample Tl) is s a is ically iden ical o he weigh ed a e age ob ained o he Odiel i e wa e samples. The e o e, simila conclusions can be d awn on he o igin o U-iso ope signa u es. Howe e , he impac o he p esence o he phosphogypsum piles on he Tin o i e wa e s wi h espec o U-iso opes is no as high as ha o he di ec inpu o phospha e e ilize p ocess was es on he Odiel i e . In ac , i is e y di icul o iden i y he sou ces o U ac i i ies om he da a p esen ed in Table 6. I any hing, he only i m conclusion is ha any Th-en ichmen a s a ions 2 and 4 is apidly emo ed om he aqueous column and p esumably adso bed on o he solid pa icles su ace. In ac , all o he Th/U mass a ios a e ,.._, 10�2, in good ag eemen wi h published da a o o he i e sys ems (Sco , 1982; Ma ínez-Agui e, 1991). The 23ºTh/234U ac i i y a ios a e consis en wi h he abo e a gumen s, adding weigh o he conclusion ha discha ge o he Tin o i e om he phosphogypsum piles con ains a g ea <leal mo e Th han U. The dec ease in he 228Th/232Th ac i i y a io a s a ions 2 and 4 in he Tin o i e e lec s he ela i e immobili y o 228Ra, a p ecu so o 228Tb in he decay se ies, in he phosphogypsum piles. Sedimen The iso ope adioac i i y in bo om sedimen s in he Tin o i e a e gi en in Table 7. I compa ed o published U da a o bo om sedimen s in o he i e sys ems (Sco , 1982; Descamps & Foulquie , 1988; Mo ón e al., 1988; Pla e e al., 1992) i becomes clea ha he i e bo om sedimen s i e accumula ing U and i s daugh e s. The concen a ions o 238U, 234U, 226Ra and 23ºTh a e lowe han hose epo ed in Table 3 o he Odiel i e bu signi ican ly highe han he published le els o undis u bed i e sys ems, always below 60 mBq/g o all o hem (Sco , 1982; Ma ínez Agui e , 1991; Ma ínez-Agui e & Ga cía-León, 1992; Pla e e al., 1992). This is no he case o 232Tb and i s daugh e 228Tb, whe e he concen a ions a e simila o hose ound in he li e a u e o unpe u bed sys ems, usually below 57 mBq/g o 232Tb (Sco , 1982; Ma ínez-Agui e, 1991; Ma ínez-Agui e & Ga cía-León, 1992). Howe e , he ac ha all U-de i ed ac i i ies inc ease owa ds he con luence wi h he Odiel i e may e lec a possible ans e o adioac i e ma e ial om he Odiel i e o he Tin o i e . The ways h ough which his occu s should be in es iga ed, bu mus be ela ed mainly o he idal cycle and suspended ma e dynamics. The co esponding ac i i y a ios o he Tin o i e bo om sedimen s a e p esen ed in Table 8. Again, as in he case o he Odiel i e , he weigh ed a e age 234U /238U ac i i y a io o 1-04 ± 0-03 sugges s an Sample - STl ST2 ST3 ST4 ST5 ST6 SOT1 ND, No de ec ed. TABLE 7 U- and Th-Iso ope and 226Ra Ac i i ies (mBq/g) in Sedimen Samples Taken Along he Tin o Ri e 23su231u226Ra232Th230Th 15,7 ± 1-3 16·8 ± 0,8 25·2 ± 0-9 11,5±3·0 20-3 ± 4-0 195·2 ± 4-4 198-5 ± 4.5 146-0 ± 2-7 30·8 ± ¡.o 341,7±11·6 74.5 ± 2-8 80-9 ± 3.0 33.2 ± 0-5 45·0 ± 4.0 66·4 ± 5-2 133.1 ± 3,8 137,8 ± 3.9 49,6±1·1 36-1 ± 3·6 88-6 ± 6-6 342·0 ± 7.5 363·8 ± 7.9 46·1 ± ¡.o 25,3 ± 2·0 231-0 ± 12·3 516·9 ± 15-9 531-2± 16·3 149-9 ± 0-8 47.5 ± 4-0 490,8 ± 23·3 299-0 ± 12-6 304-5 ± 12-8 50-3±1·7 53-7±4·1 279·5 ± ¡5.¡ 22sTh ND 34.3 ± 1-5 48,9 ± 4-8 36-3 ± 4,1 30-8 ± 2·3 41·0 ± 4·0 55.4 ± 4.0 TABLE 8 U and Th Concen a ions (µg/g), Th/U Mass Ra io and Iso opic Ac i i y Ra ios in Sedimen Samples Along he Tin o Ri e Sample [U][ThjTh/U STI 1·26 ± 0·06 2·84 ± 0-74 2·24 ± 0.59 ST2 15·7 ± 0-5 7-6±0-3 0-485 ± 0·023 ST3 6-0 ±0·2 11-1 ± l·O 1·85±0·18 ST4 10-7 ± 0·3 3.9 ± 0-9 0·831 ± 0-087 ST5 27-5 ± 0·6 6-2 ± 0·5 0,226 ± 0,019 ST6 41-6±1·3 11,7 ± 1-0 0-282 ± 0·025 SOT1 24-0 ± l·O 13·2± l·O 0,550 ± 0-048 234U/23su 230Th/234U 1,07 ± 0-07 1-21±0·25 1.02 ± 0,02 1-72 ± 0·07 1·09 ± 0·05 0·82 ± 0-07 1·04 ± 0,03 0,64 ± 0·05 1-06 ± 0-02 0·64 ± 0·04 1·03 ± 0,02 0-92 ± 0·05 1-02 ± 0·03 0·92 ± 0·06 226 Ra/230Th 1-24 ± 0,25 0-43 ± 0·02 0·50 ± 0,04 0,56 ± 0,04 0,20 ± 0,01 0·31 ± 0·02 0·18±0,01 22sTh/232Th 230Th/232Th 1-77 ± 0-56 1·11 ± 0-05 11·1 ±0·5 1-09 ± 0-13 1-48 ± 0· 15 1-01 ± 0,14 2-46 ± 0·26 1-22±0·10 9.2 ± 0·6 0,86 ± 0-10 10·3 ± 0·8 1-04 ± 0-09 5·2 ± 0·3 a i icial ongm o U-iso ope signa u es such as phosphogypsum piles si ua ed along i s igh bank. The gene al end in he iso opic a ios sugges a U-en ichmen in he Tin o i e bo om sedimen s. Obse a ions made om he sedimen s in he Odiel i e a e also alid o he Tin o i e case. CONCLUSIONS A ca e ul sampling campaign ca ied ou in 1989 o i e wa e and bo om sedimen samples along he Odiel and Tin o i e s (sou hwes Spain) has yielded comp ehensi e U, Th and 226Ra iso opic da a. These da a ha e been in e p e ed o es ablish he connec ion be ween he obse ed anomalously high concen a ions o U-, Th- and 226Ra-iso opes in wa e s and sedimen s, and he ope a ions o phospha e e ilize ac o ies loca ed in a zone i ually su ounded by bo h i e s. The conclusion based on he iso opic da a is ha bo h liquid and solid was es a ising om he e ilize p oduc ion, and discha ged om his indus ial zone, a e esponsible o he obse ed adioac i i y enhancemen in he immedia e en i onmen o he e ilize plan s. ACKNOWLEDGEMENTS The au ho s hank he Spanish DGICYT (con ac PB89-0621) and he AMA o Jun a de Andalucía o he inancial suppo o his wo k. They also wish o hank J. M. Ab il, G. Manjón and J. Díaz o helping in he sampling, and a e obliged o Miss Sand a Hasle o Iso ope Geoscience Sec ion, Ha well Labo a o y o in aluable help wi h he analy ical wo k. REFERENCES Bae slé, L. H. (1991) S udy o he adionuclides con ained in was es p oduced by he phospha e indus y and hei impac on he en i onmen . Commission o he Eu opean Communi ies, EUR 13262 EN, Nuclea Science and Technology. Bo ego-Flo es, J. & Pendón-Ma ín, J. C. (1988). Algunos ejemplos de in luencia de los p ocesos an ópicos en el medio sedimen a io: La Ría de Huel a. Hena es, Re . Geol., 2, 299-305 (in Spanish). Descamps, B. & Foulquie , L. (1988). Na u al adioac i i y in he p incipal cons i uen s o F ench i e ecosys ems. Radia ion P o ec ion Dosime y, 24(1), 143----47. Gascoyne, M. (1982). Geochemis y o he Ac inides and hei daugh e s. In U anium Se ies Disequilib ium: Applica ions o En i onmen al P oblems, ed. I ano ich, M. & Ha mon, R. S. Cla endon P ess, Ox o d, chap. 2. Gascoyne, M. (1992). Geochemis y o he Ac inides and hei daugh e s. In U anium Se ies Disequilib ium: Applica ions o Ea h, Ma ine and En i on men al Sciences, ed. I ano ich, M. & Ha mon, R. S. Cla endon P ess, Ox o d, chap. 2. Guimond, R. J. & Ha din, J. M. (1989). Radioac i i y eleased om phospha e con aining e ilize s and om gypsum. Radia . Phys. Chem., 34, 309-15. I ano ich, M. & Mu ay, A. (1992). U anium Se ies Disequilib ium: Applica ions o Ea h, Ma ine and En i onmen al Sciences, ed. I ano ich, M. & Ha mon, R. S. Cla endon P ess, Ox o d, chap. 5. Kos e , H. W., Ma wi z, P. A., Be ge , G. W., an Wee s, A. W., Hegel, P. & Nienwenh ize, J. (1991). 210Po, 210Pb, 226Ra in aqua ic ecosys ems and polde s, an h opogenic sou ces, dis ibu ion and enhanced adia ion doses in he Ne he lands. In V In . Symp. on he Na ional Radia ion En i onmen , Salzbu g, Aus ia. Lally, A. E. & Eakins, J. D. (1978). Pape p esen ed a Symp. De e . Radionuclides En i on. Bio. Ma s. CEGB, London. Ma ínez-Agui e, A. (1991 ). Radioac i idad na u al en di e sos compa imen os na u ales de Andalucía. PhD hesis, Se ille Uni e si y, Spain (in Spanish). Ma ínez-Agui e, A. & Ga cía-León, M. (1991a). Na u al adioac i i y enhance men by human ac i i ies in i e s o sou hwes o Spain. J. Radioanal. Nucl. Chem., Le e s, 155(2), 97-105. Ma ínez-Agui e, A. & Ga cía-León, M. (1991b). U- and Ra-iso opes in he Guadalqui i i e , sou h o Spain. In V ln e na ional Symposium on he Na u al Radia ion En i onmen , Salzbu g, Aus ia. Ma ínez-Agui e, A. & Ga cía-León, M. (1992). Na u al adioac i i y in he Guadalqui i i e , sou h o Spain (submi ed). Miyake, Y., Sugimu a, Y. & Tsubo a, H. (1964). Con en o U, Ra, and Th in i e wa e s in Japan. In The Na u al Radia ion En i onmen , eds. Adams, J. & Lowde , W. M . . Uni e si y o Chicago P ess, Chicago, IL, pp. 219-25. Miyake, Y., Sugimu a, Y. & Yasujima, T. (1972). Tho ium iso ope con en in i e wa e in Japan. Pape s in Me eo ology and Geophysics, 24(1), 67-73. Moo e, W. S. (1967). Amazon and Mississippi i e concen a ions o u anium, ho ium and adium iso opes. Ea h Plane . Sci. Le ., 2, 231-4. Mo ón, M.C., Ma ínez-Agui e, A. & Ga cía-León, M. (1988). De e mina ion o le els o U, Th and Po om di e en en i onmen al samples. In In e na ional Con e ence on En i onmen al Radioac i i y in he Medi e anean A ea. SNE ENS, Ba celona, Spain, p. 111. Osmond, J. K. & I ano ich, M. (1992). U anium se ies mobilisa ion and su ace hyd ology. In U anium Se ies Disequilib ium: Applica ions o Ea h, Ma ine and En i onmen al Sciences, ed. I ano ich, M. & Ha mon, R. S. Cla endon P ess, Ox o d, chap. 8. Paul, A., Londhe, V. & Pillai, K. (1980). 228Ra and 226Ra le els in a i e en i onmen and i s modi ica ion by human ac i i ies. In Na u al Radia ion En i onmen III, Vol. 2. US Depa men o Ene gy, pp. 1633-54. Pla e , A. J., I ano ich, M. & Dugdale, R.E. (1992). U anium se ies disequili b ium in i e sedimen s and wa e s: he signi icance o anomalous ac i i y a ios. Appl. Geochem., 7(2), 1-5. San schi, P., Li, Y. H. & Bell, J. (1979). Na u al adionuclides in he wa e o Na aganse Bay. Ea h Plane . Sci. Le ., 45, 201-13. Sco , M. R. (1982). The chemis y o U- and Th-se ies nuclides in i e s. In U anium Se ies Disequilib ium: Applica ions o En i onmen al P oblems, ed. l ano ich, M. & Ha mon, R. S. Cla endon P ess, Ox o d, chap. 8. S ain, C. D. (1979). An e alua ion o adium-226 and adon-222 concen a ions in g ound and su ace wa e s nea phospha e mining and manu ac u ing acili y. Pape p esen ed a Annual Mee ing o he Heal h Physics Socie y, Philadelphia, PA. UNSCEAR (1977). Ionizing Radia ion and Biological E ec s. Uni ed Na ions Scien . Comm. on E ec o A omic Radia ion, New Yo k, pp. 86-91. Van de Heidje, H., Klijn, P. & Passchie , W. (1988). Radiological impac s o he disposal o phosphogypsum. Radia ion P o ec ion Dosime y 24(1), 419-23.