Low-level radioactivity studies in the marine environment of the South of Spain

i lnmen Low-le el adioac i i y s udies in he ma ine en o he Sou h o Spain * G. Manjón, A. Ma ínez-Agui e and M. Ga cía-León Facul ad de Física, UniL·e sidad de Sel'illa, 41080 Sel'illa, Spain In his pape p elimina y le els o na u al and man-made adionuclides in he Sou h Spanish ma ine en i onmen a e p esen ed. Local man-made sou ces a e ound o be he main con ibu o s o he na u al en i onmen al adioac i i y in such a eas while allou is mainly esponsible o he occu ence o a i icial adioac i i y in ou zone. . In oduc ion So a , he p esence o en i onmen al adioac i i y in Andalucía (Sou h o Spah) had no been s udied. Thus, since 1988 a la gc p ojec o hc de e mina ion o na u al and man-made adionuclidcs in his egion was s a ed. *Wo k pa ially suppo ed by he con ac PB89-0621 o he Spanish CICYT and he AMA o he Jun a de Andalucía. Andalucía (sec ig. 1) occupies he whole Sou h o Spain and he majo i y o he Sou h o he lbe ian peninsula. The esea ch p og amme consis s o he measu emcn o 9<JTc, 137Cs. U-. Ra- and Th-iso opes and 210Po in a la ge g oup o samples, such as seaweed, i e wa e s, ainwa e s, sedimen s, e c. (see ig. 1 ). Wc p esen he c so ne esul s ob ained o he ma ine sidc o hc en i onmen s udied. We will de sc ibe in he nex sec ions, le els o 99Tc and 137Cs in scawecd samples. U-iso opes and 2Hl Po in i c wa e and sedimen samples will also be gi cn. MEOITERRANEAN SEA Q k: '.'Ei' -,.ATI.R SAMPLES D S�.A�"El:.'.J SAMPLES & üNDERGROUND WATERS • RAINWATER SAMPLES • MAIS TCXJNS Fig. l. Map o Andalucía (Sou h o Spain) showing he ype o samples and s:::11p!ing s a ions included in he esea ch p ojec . Thc mc hods o dc c mina ion o hc abo c-mcn ioncd iso opcs and hc esul s ob aincd a e ou lincd in hc ollowing scc ions. 2. Expe imen al Low-backg ound GM gas- low �-coun ing. -y- and a-spcc ome y ha e been used o ('9Tc, 137 Cs and a-emi e measu cmen s, espec i ely. A b ie accoun o he indi idual me hods is gi en in hc ollowing pa ag aphs. 2.1. 99Tc A sol en ex ac ion cchniquc is uscd o 99Tc de e mina ion. Fi s , so ne 15-30 g o d ied and pow de cd seaweed a e spiked wi h a known 99mTc ac i i y. The sample is hen calcina ed a 600 º C. The ashes a e dissol ed wi h 2% HCI, and echnc ium is ex ac cd wi h ibu ylphospha e (TBP). Subsequen ly, Te is back-ex ac ed om he o ganic phase wi h 2M NaOH. This solu ion is elec opla ed a 0.35 A o 2 h and echne ium is deposi ed on o a s ainless s eel planche (1,2]. Due o he ela i ely so 99Tc �-spec um (Emax = 292.3 ke V) an elec odeposi ion echnique o hc p epa a ion o he inal sou ce is mo e adequa e han a simple e apo a ion o he 2M NaOH solu ion, since in his way sel -abso p ion e ec s a e minimized. The adiochemical yicld Y o hc p ocess is calcu la ed by measu ing he 99mTc ac i i y cco c ed. This is accomplished wi h a 76 mm X 76 mm Nal(TI) -y-spec omc c , aking ad an age o he 140-kcV pho on emi ed by his adionuclidc. A e i e o six days, when ali he 99mTc (T112 = 6.02 h) has dccayed, he 99Tc (3-ac i i y om h · samplc is measu ed. Due o he e y Iow 99Tc concen a ion in na u e, a low-le el coun ing echnique has o be ap- Table 1 plicd. Thus, a low-backg ound (0.2 cpm) gas- low GM coun c is uscd o (J9Tc mcasu cmcn s. The c iciency o he de ec o cachcs a aluc o 37%. I was calcu la cd wi h 99Tc s anda d samplcs o wcll-known ac i i ics. 2.2. 137Cs mes is di cc ly de c mined by HPGc -y-spec omc y. Fo ha , a gi cn mass o d icd and powdc ed scaweed is placed in a s anda d geomc y and coun ed wi h he spec omc c [3]. The de ec o backg ound is educed by using a passi e lead shielding 1 O cm hick, in c nally co e ed wi h a ew mm o coppe . The coun ing e iciency was ob ained by coun ing algae ma e ial, in hc s anda d geomc y. homoge ncously spiked wi h known mes and 152 Eu ac i i ies. 2.3. U-iso opes and 210 Po Thc a-ac i i y om 238 U. 234U, 235 U and 210Po was measu ed by Si su acc ba ic o ion implan ed a spec ome y [4,5]. Fo ha , so ne ew g ams o d ied and powde ed sedimen a e spikcd wi h known 232 U and 208Po ac i i ies. Then he sample is diges ed wi h HN03 and aqua egia. The esiduc is dissol ed in 8M HN03 and he solu ion il e ed in o a decan a ion unnel which con ains TBP. A e shaking, U and Th pass o he o ganic phasc while Po and Ra emain in he aqueous phasc. Bo h phases a e scpa a ed. The aqueous phasc is e apo a ed o nea d yness and he csidue dissol ed wi h concen a ed HCI. A e ha , Po is sel -deposi ed on o Ni planche s a 60 º C. acco ding o he me hod o Flynn e al. [6]. l is impo an o no e ha so ne mg o asco bic acid a e added o he elec oly e o a oid he deposi ion o Fe. The o ganic phasc is dissol ed wi h xylenc and Th is back-ex ac cd om i wi h 1.5M HCI. Thc cmaining o ganic phase is mixed wi h dis illed H :!O o back-cx- 137Cs le els in seaweed samples collec ed along he coas s o Andalucía egion (Sou h o Spain) du ing 1988 and 1989 Type o Species Numbe o Ac i i y (d y weigh ) [mBq/g] alga da a mínimum maximum a e age B own halop e is scopa ia 10 0.7±0.2 2.9±0.3 l.4±0.7 G een ul a ígida 7 0.6±0.5 2.3 ± 0.3 l.4±0.6 G een codium 7 0.7 ±0.3 3.8± 1.7 2.2± 1.1 B own ucus ó 0.6±0.2 1.5 ±0.3 1.2±0.3 G een sa gassum ulga e 6 0.7 ±0.4 2.8±0.6 l.3±0.8 B own dyc io a dicho oma 2 0.6±0.4 1.4±0.6 l.0±0.6 B own cys osei a e icoides 2 0.3±0.7 0.8±0.3 0.6±0.3 B own co allina medi e anea l.6±0.6 B own cimodocea modosa l.2±0.4 Red holopi is incunous 0.8±0.3 ac U. Thc inal solu ion is d icd and U is clcc o pla cd on o s ainless s eel planche s by he ne hod o eís. [7] and [8]. As o wa e sa nples, so ne 1 o 5 1 a e spiked wi h a known m U ac i i y and c apo a cd. Thc csiduc is ca ed as a scdimcn samplc o U cx ac ion. 3. Resul s 3.1. Le els in seaweed mes and 99 Tc ac i i ies ha c becn s udicd in a widc nu nbe o scawccd specics. In able 1 hc mes nini mu n, naxi num and a e age ac i i y alues o so ne o such species a e p escn ed. Ve y simila , and low, B7Cs spcci ic ac i i ies, oughly 1.3 nBq/ g d y weigh , a e ob ained ei hc o he ed, b own o g een alga species. Such low alues do no allow o de e mine hc bes bioindica o o ou zonc. On he o he hand, sincc he e is no local sou ce o adioac i i y o ou egion, he le els ob ained seem o be cp escn a i e o hc wo ldwide allou backg ound in he Sou h o Spain. This idea can be con i med when ou esul s and he e y sca ce p e ious da a exis ing in hc cu en li e a u e a e compa ed. Table 2 n7Cs and ""'Te lc cls ound in ucu!ii spi alis and VC!iiiculo!iius samples collcc c,• along hc Sou h Spanish coa!-ih du ing 19kK and 19H9. Thc silc numhc co csponds o hc !-iampling si c shown in hc map o ig. 1. Mean alucs o hc Mcdi c  ancan and A lan ic coas s a e also gi cn. Sampling Ac i i y (d y wcigh ) (mBq/g} si e (da e) 1'7Cs l,l lTc ac i i y ac i i y Paloma es (1988) [1] 0,6±0.2 0.25±0.04 Paloma es (1989) (1) 1.3±0.5 0.31 ±0.03 Cabo de Ga a (1988) [2] 1.6±0.3 O.IS ±0.04 Pun a Palomas (1988)(3) 1.1 ±0.4 0.43±0.06 Ro a ( 1989) (4) n.m.ª 0.1 ±0.2 Isla C is ina (1989) [5] 1.2±0.5 0.30 ± (l.03 Ayamon e (1988) (6) 1.5 ±0.4 0.14±0.oJ Medi e anean coas s 1.1 ±0.4 0.25±0.13 A lan ic coas s 1.3 ±0.2 0.22+0.11 ª n.m. = no measu ed Thus, le e Is o 0.8 nBq/ g wc c ound in Galicia, No h-Wes o Spain, du ing 1984 [9] and o abou 0.9 nBq/g in he coas s o Po ugal du ing 1985 [10], bo h o Fucus spccics. They wc c a ibu cd essen ially o allou , which suppo s ou p e ious commen . O Wa e Samples 6 Sedimen 5a lPleS Fig. 2. Map co esponding o he sampling s a ions o Tin o and Odiel i e s a ound he own o Huel a (see also ig. 1 ). Table 3 U-iso opes ac i i y concen a ion. oge he wi h he 234U ¡ 2Jsu ac i i y a io o i e wa e samples aken a he Odiel (O) and Tin o (T) i e s. Samples OT we e aken a he con luence o bo h i e s. The pH o he wa e s a e also gi cn. See ig. 2. o an easie comp ehension o he able. Sample pH Ac i i y concen a ion [mBq/1) T1 T2 T3 T4 OTl OT2 07 06 05 04 03 02 01 2.0 5.0 5.0 5.5 5.5 6.0 5.5 4.5 4.5 4.5 5.5 5.5 3.0 23NU 170.0± 11.0 37.0± 3.8 24.8± 3.0 26.0± 2.0 31.0± 5.1 31.1± 1.7 30.0± 4.0 '60.0± 8.1 778.0±50.0 206.5± 18.8 13.9± 2.6 20.0± 2.7 66.0± 8.0 350.0±20.2 41.0± 4.1 30.3± 3.4 23.0± 2.0 46.0± 6.4 38.0± 2.0 36.0± 4.6 SO.O± 7.0 777.0±50.0 206.5± 18.9 20.3± 3.11 22.0± 2.8 121.0± 13.0 Ac i i y a io 2.02±0.06 1.09±0.11 1.22±0.20 0.88±0.10 1.40±0.09 l.22±0.08 1.20±0.18 0.83±0.12 l.00±0.02 1.00±0.07 1.47±0.35 1.10±0.17 1.83±0.30 In able 2, wc p esen so ne ew addi ional 137es esul s oge he wi h he q9Tc ac i i ies in Fucus sam ples. The c is no di e encc, bo h o mes and 99Tc, be wecn hc ac i i ics ob aincd in hc mcdi c anean and hc a lan ic sidcs o he Andalusian coas . eon cc ning hc 99Tc csul s, c y simila commen s o hose gi en in able 1 o 137es can be made. Thus, an a e age aluc o 0.2 mBq/g d y weigh can be ob sc cd. which is in modc a c ag ccmen wi h alucs ound in Galicia [21 and Po ugal [10) coas s, o abou 0.4 and 0.6 mBq/g d y weigh , cspcc i cly, bo h du  ing 1985. Table 4 3.2. Lel'el.,· in sedimcn and il'en a e U-iso opes and 2111Po ha e been dc c mina ed in scdimen and i c wa e samplcs collec cd a he Odiel and Tin o i c s (Sou h-Wes o Spain). Such i c s (scc ig. l and 2) su ound a la gc indus ial complcx, which includes se e al phospha e e iliz e s ac o ies nea hei mou hs a he A lan ic Ocean. I is well known ha such acili ies p oduce a clca adiological impac in hei immcdia c en i onmen [11]. Ou csul s, using U and 210Po as indica o s, con i m such obsc a ions. In able 3 he U-iso opc ac i i ics ound in wa c s o hc Odicl and Tin o i e s a e p esen cd (sec ig. 2 o an casie comp ehension o able 3). In gene al, hc ac i i ies in hc Odicl i e a e highc han in he Tin o i c . Thus, in hc Odiel wa e s, a clca peak o ac i i y can be seen. This co esponds o samples aken nca he place whc e he phospha c e ilize complex is loca ed. I seems, he e o c, ha such indus ies a e di ec ly elcasing hci was es o hc Odiel i c . I does no occu so, o hc case o hc Tin o i c . In ac , hc U le els ound in i s wa e s a e o ally compa ible wi h ac i i ics ob ained in he Guadalqui i i e [12], which c osses ou cgion om Eas o Wes , and ha ha c bcen akcn as a backg ound le el o ou s udy. Thc esul s o samplcs Tl and O 1 a e specially in c cs ing. Such wa e s wc c akcn nea hc sou ces o he Tin o and Odiel i e s, cspcc i cly. Thc na u al Iow pH o such wa c s a ou s hc cdissolu ion o U om hc bcd o he i c s o hc aqucous phasc, which would cxplain hc cla i ely high lc cls o ac i i ics ound. Fu hc mo c. his would accoun o hc high 234U cn ichmen obsc ed in hcse samplcs. I would be in c cs ing o s udy he o m in which hc was cs om he e ilize ac o ics a e cleased U-iso opes and zwpo ac i i y concen a ions (in mBq/g) o sedimen samples aken ,: he Odiel (SO) and Tin o (ST) i e s. Sample SOT was aken a he con luence o bo h i e s. Sec ig. 2 o and easie comp ehension o he able. Sample Ac i i y concen a ion [mBq/1] :!JNU z35u z3..iu :iwpo ST2 100.0± 7.8 3.60± 0.72 110.0± 8.1 n.m:1 ST3 250.0 ± 1.7 11.0 ± 1.2 260.0 ± 1.7 252.0± 10.0 ST4 277.0± 13.0 l().3 ± 0.8 290.0± 14.0 341 ± 12.0 SOT 264.1 ± 29.6 n.d.h 275.7± 30.8 339.4 ± 13.3 S07 1060.0± 75.0 48.0 ± 4.9 1060.0± 75.0 1194.8 ± 112.2 SOó 42.0± 3.9 2.80± 0.66 45.0± 4.2 41.6± 2.7 sos 1100.0 ± 130.0 55.0 ± 1 o.o 1200.0 ± 130.0 820.9± 50.2 S04 160.0± 11.0 7.7 ± 1.0 170.0 � 12.0 615.2 ± 28.0 ª n.m. = no measu ed. h n.d. = no de cc cd. in o hci immcdia c cn i onmcn . This wo k is cu  cn ly bcing ca :-icd ou in ou g oup. Howc c , om hc da a wc p cscn in able 4. i seems ha bo h i e beds, hose o Odiel and Tin o i c s, a e accumula ing U and 2111Po adi i ics. lndccd, hc lc els obsc cd in scdimcn s a e clea ly highc , bo h o U-iso opcs and o 2H>Po, han o hc le cls ound in di c cn i c s, including Spanish sys ems [13,14]. Thc case o samplc S06 is no su p ising, sincc so ne o hc chemical ma c ials, wi hou adioac i i y, a e bcing clcascd in such sampling poin ogc hc wi h hc was cs om hc c ilizc indus ies. This would con ibu c o Iowc ing he spcci ic ac i i y. Re e ences [1] E. Holm, J. Rioseco and M. Ga cía-León, Nucl. lns . and Me h. 223 (1984) 204. [2] G. Manjón and M. Ga cía-León, An. Fís. 886 (1990) (in Spanish) 63. (3) C.I. Sánchez-Angulo and M. Ga cía-León, Nucl. Geo phys. 2 (1988) 69. (4) A. Ma íncz-Agui c. M.C. Monín and M. Ga da-Lcún. o he puhlishcd in J. Radionanal. Nucl. n.�m. (5) A. Ma íncz-Agui c and M. Ga cía-Lc<,n. o he puh- lishcd in J. Radioanal. Nucl. Chcm. Lc . (6) W.W. Flynn, Anal. Chcm. Ac a 43 (1968) 221. (7) L. Halls adim,. Nucl. lns . and Mc h. 22J ( 1984) 266. lXJ R. Ga cía-Teno io, M. Ga cía-León, G. Madu ga and C. Piazza, An. Fís. 882 (1986) 238 (in Spanish). (9) P.I. Mi chell. A. Vidal-Quad as. J.L. Fon and M. Oli a. J. En i on. Rad. 6 ( 1988) 77. [ 10) A. Aa k og, S. Boelski e, E. Buch. G.C. Ch is cnsen. H. Dahlgaa d, L. Halls adius. H. Hansen. E. Holm and J. Rioseco, Ris0 Na ional Labo a o y Repo -R-510 (1987) 74. (11] R.J. Guimond and J.M. Ha din, Radia . Phys. Chem. 2 (1989) 309. (12] A. Ma ínez-Agui c and M. Ga cía-León. in p cpa a ion. (13) F. Ve a-Tomé and A. Ma ín-Sánchez, J. Radioanal. Nucl. Chem. 1 ( 1989) 73. (14) M.C. Mo ón, A. Ma ínez-Agui e and M. Ga cía-León. P oc. ln . Con . on En i onmen al Radioac i i y in he Medi e anean A ca. Ba celona. 1988 (SNE-ENS. 1988) p. 111.