Anthropogenic emissions of Po-210, Pb-210 and Ra-226 in an estuarine environment

. .. 1- ANTHROPOGENIC EMISSIONS OF 21oPo, 21oPb ANO 226Ra IN AN ESTUARINE ENVIRONMENT A. MARTÍNEZ-AGUIRRE,* M. GARdA-LEÓN,* C. GASCÓ,** A. TRAVESI** *Facul ad de Física, Uni e sidad de Se illa, 41080 Se illa (Spain) **! ns i u o de Medio Ambien e, Ciema , 28040 Mad id (Spain) An ex ensi e s udy on he dis ibu ion o na u al adionuclides in an es ua ine ecosys em loca ed in Sou hwes em Spain is p esen ed. This en i onmen is highly a ec ed by he was es eleased by a phospho ic acid indus y which uses phospha e ocks as aw ma e ial o e ilize p oduc ion. This ock has gene ally high concen a ions o U and i s daugh e s. The es ua y is o med by wo i e s, Odiel and Tin o, which ha e a common mou h in o he A lanic Ocean and a sal ma sh (Odiel ma sh) a ec ed by he in come o Odiel i e wa e s. This i e ecei es di ec ly he liquid and pa o he solid (gypsum) was es eleased om he indus ies. Besides ha , mos o he phosphogypsum was es a e s o ed in unco e ed piles a he igh ma gin o he Tin o i e . The s udy has concluded ha he was es om such indus ies a e he cause o he enhanced concen a ions ound a he bed o bo h i e channels as well as he enhancemen ound in su ace soils in ce ain zones o he Odiel we ma shland. lndeed, he No hem ma sh and he Moja e a channel a he Odiel ma sh seem o be he main sinks o he con aminan eleased by he phospho ic acid indus y. On a his o ical ime scale, sedimen s may be ega ded as, a leas , a empo a y sink o much o he ma e ial which passes h ough he a ious chemical and biological cycles ope a ing on he ea h's su ace. A p esen , he ma e ial which is eleased and akes pa in hese cycles can ha e i s composi ion ma kedly a eé ed by an h opogenic emissions. Sedimen s became an en i onmen al hos o many o he was e p oduc s discha ged by socie y. Toe e ec s o hese man-made emissions, in so ne si ua ions, can be su icien ly s ong o a ec highly he composi ion o he deposi ed sedimen . In he ma ine en i onmen , nea -sho e sedimen s e ain he s onges memo y o he impac o he eleased ma e ial on he ea h 's su ace. This is because hese sedimen s accumula e a a es which can be as much as se e al o de s o magi ude highe han hose in deep sea and because hey a e being o med in a eas in which many an h opogenic subs ances ini ially each he sea. Mos indus ial complexes a e loca ed in es ua ine a eas close o he sea. Thus, hey beha e as sinks o much o he an h opogenic emissions, which wi h ime will p obably be anspo ed o hei close sea en i onmen . Thus. he s udy o na u al en i onmen al adioac i i y in es ua ine sys ems is o g ea impo ance and in e es in heal h physics and many o he pu poses. J:;S. Pile• ol pho1phogypsum O 3 km Fig. l. Map o he Es ua ine a ea o Huel a. Bo om sedimen s om he Odiel and Tin o i e s a e deno ed by "O" and "T', espec i ely, ollowed by a numbe which indica es he loca ion o he sample. Soil samples om he Odiel ma sh a e deno ed by "M" ollowed by he numbe o he s a ion In Spain a la ge indus ial complex is loca ed nea he ci y o Huel a, along he es ua y o med by he Odiel and Tin o i e s. A phospho ic acid indus y o e ilize p oduc ion is loca ed a he le ma gin o he Odiel i e (see Fig. 1 ). Phospha e o es used o phospho ic acid p oduc ion con ain impo an amoun s o na u al adioac i e elemen s, specially 238U and daugh e s, in concen a ions ha depend on hei geog aphical and geological o igin, bu which can each up o 300 ppm o U. Toe adioac i e impac o he indus ial complex o e he Odiel and Tin o i e s has been widely s udied o he case o U and Th iso opes.1•2 A dose es ima ion due o he 222Rn inhala ion emi ed by he phosphogypsum piles has been also published. 3 Toe mo emen s o hese wa e s due o he low o he wa e du ing change in ide, p oduce he logical dis ibu ion o he con aminan upwa ds and downwa ds o he poin o elease. Nex o he i e s, he e is a la ge saline we ma shland. This a ea is a na u al ese a ion wi h high biological ac i i y. I is loca ed a he igh side o he Odiel i e in on o he e ilize indus y and is highly a ec ed by he income o he Odiel i e wa e s. Toe adiological signi icance o 210Po, 210Pb and 226Ra in he u u e <lose ecei ed by he popula ion mo i a ed he ex en ion o p e ious wo ks. Toe p esen pape discusses he esul s ob ained in he s udy in he p esence o hese adionuclides in bo om sedimen s om he Odiel and Tin o i e s as well as in su ace soil samples om he we Ma shland. The gene al aim was o s udy he each and in luence ha he e ilize p oduc ion has o e all he es ua ine a ea. Expe imen al Two sampling campaigns we e pe o med in Feb ua y and No embe 1993, espec i ely. In each campaign bo om sedimen s om he Odiel and Tin o i e s and su ace soil sampes om he Odiel Ma sh we e collec ed. Bo om sedimen s we e collec ed a he cen e o he i e s, whe eas soil samples we e collec ed du ing he low ide in a eas co e ed wi h wa e du ing he high ide. Toe samples we e d ied, powde ed and homogenized be o e he analysis. So ne 1 g o sample was spiked wi h well known 208Po ac i i ies. A e diges ion o he sample wi h HN03 and aqua egia, Po is ex ac ed by sol en ex ac ion and he inal solu ion is sel -deposi ed on o sil e planche s.4 210Po ac i i y is de e mined by a-spec ome y wi h su ace ba ie o ion-implan ed de ec o s. 210Pb and 226Ra a e measu ed by y-spec ome y wi h Re e se Coa ed Ge manium de ec o s. 210Pb duplica e analysis we e pe o med in sedimen aliquo s,5•6 being signi ican ly conco dan wi h hose ob ained by y-spec ome y. Resul s and discussion To simpli y he discussion, he da a ob ained on bo om sedimen s om he Odiel and Tin o i e s o bo h sampling campaigns will be i s discussed. Fo he sake o cla i y, we will deno e by "O" hose samples collec ed a he Odiel i e and by "T" hose om he Tin o i e . Samples collec ed in he con luence o bo h i e will be deno ed by "OT". The numbe ollowing hese da a will deno e he loca ion o he sampling s a ion (see Fig. 1 ). La elly, da a ob ained o he same sampling campaigns in su ace soils om he Odiel we ma shland will be p esen ed and discussed. Toe loca ion o he soils collec ed a his a ea is shown in he same Figu e. Code 210p0 01 518 ± 26 02 726± 21 03 4919± 126 04 1300± 100 05 884± 33 TI 76± 10 T2 221 ± 16 T3 1498± 75 OTl 474± 13 OT2 1062± 47 OT3 56± 5 OT4 54± 8 Bo om sedimen s In Tables 1 and 2 he 210J>o, 210Pb and 226Ra ac i i y concen a ions in mBq/g oge he wi h so ne ac i i y a ios, o Feb ua y and No embe campaigns a e p esen ed, espec i ely. F om he esul s o ali adionuclides in bo h sampling campaigns,7 i can be concluded ha all bo om sedimen s om he Odiel i e p esen ac i i y concen a ions Table 1 Radioac i e concen a ions in mBq/g in bo om sedimen s om he Odiel and Tin o i e s collec ed in Feb uay 1993 210pb226Ra 506± 31 406± 96 922 ± 38 584± 88 2743 ± 64 3395 ± 198 1176 ± 41 1140 ± 129 763 ± 35 723 ± 65 31 ± 16 70± 20 82±20 �203 914 ± 40 618 ± 110 445 ± 27 211 ± 68 629 ±31 364± 77 20± 15 �67 <26 <62 Table 2 210p0¡210pb 1.02 ±0.08 0.79±0.04 1.79± 0.06 1.16 ± 0.07 2.45 ± 1.30 2.70±0.69 1.64 ± 0.11 1.07 ±0.07 1.69 ± 0.11 2.80±2.11 21 ºPb 226Ra 1.24± 0.30 1.57 ± 0.25 0.81 ±0.05 1.03± 0.12 1.05± 0.11 0.44± 0.26 1.47 ± 0.27 2.11 ± 0.69 1.73 ± 0.37 Radioac i e concen a ions in mBq/g in bo om sedimen s om he Odiel and Tin o i e s collec ed Code 210p0 01 567 ± 38 02 500± 30 03 2080± 140 04 1330± 80 05 1660± 140 T1 T2 233± 16 T3 788± 50 OTI 600± 24 OT2 618± 39 OT3 21 ± 2 OT4 19 ± 2 in No embe 1993 210pb226R_a 511 ± 86 405 ± 55 419 ± 66 363 ± 75 925 ± 134 972 ± 109 1160 ± 189 831 ± 83 1450±213 1273 ± 112 98± 22 94± 22 73 ± 14 87± 20 733±116 718± 62 408 ± 70 407± 45 529 ± 81 416± 29 �35 �32 15± 10 19± 10 210p0¡210pb 1.11 ± 0.20 1.19 ± 0.20 2.25 ± 0.36 1.15 ± 0.20 1.15 ± 0.19 3.19 ± 0.65 1.08 ± 0.18 1.47 ± 0.26 1.17 ± 0.19 1.27 ± 0.86 21 ºPb 226Ra 1.26± 0.27 1.15 ± 0.30 0.95 ± 0.17 1.40± 0.27 1.14 ± 0.19 1.04 ± 0.34 0.84± 0.25 1.02 ± 0.18 1.00± 0.21 1.27 ± 0.21 0.79± 0.67 ... abo e backg ound le els. 8 Thus, adioac i e concen a ions abo e 470, 445 and 211 mBq/g o 210Po, 210pb and 226Ra, espec i ely, a e ound along he es ua y o he Odiel i e in Feb ua y. Radioac i e concen a ions in No embe a e simila o hos� ound in Feb ua y. The highes ac i i y concen a ion is ound, as i was expec ed, a hc, poin o elease o he phospho ic acid indus y (03), being he adioac i concen a ion in Feb ua y much highe han ha in No embe o ali adionuclides. Tui ac i i y concen a ion dec eases downs eam he i e channel bu s ill high adioac i d concen a ions we e ound a he common con luence wi h he Tin o i e (OTl and OT2). Pa em dis ibu ions o 210po and 210Pb along he Odiel i e o samples collec ed in No embe a e shown in Fig. 2. These pa em dis ibu ions a e simila o ha o 226Ra, and e lec s ali said abo e. Samples OT3 and OT4 we e collec ed a he A lan ic Ocean coas close o he mou h o he i e . F om he da a in Tables 1 and 2 o s a ions OT3 and OT4 is easy o conclude ha he con amina ion in he Odiel i e does no ye each he coas . In ac , adioac i e concen a ions a e simila o ypical backg ound le els ( - 25 mBq/g).9 In he case o he Tin o i e channel, h ee samples we e collec ed. The adioac i e concen a ion in bo h sampling campaigns a e simila and excep ing s a ion T3, hey a e 10l 5 CT 'b 4 x 3 2 _210Po ----- 210Pb Fig. 2. Compa ison o 210Po and 210Pb ac i i y concen a ion in mBq/g in bo om sedimen s om he Odiel i e collec ed in Feb ua y 1993 lowe han hose ound in he Odiel i e channel. The e o e, he excep ion o s a ion T3, has an ac i i y concen a ion e en highe han in mos Joca ion o he Odiel i e�. This s a ion is loca ed a he con luence o a small na u al i ule (Es e o del Rincón) wi h he Tin o i e . This i ule c osses he phosphogypsum s o age a ea and p obably, i can edissol e pa o he adioac i i y concen a ion con ained in hese was es. S a ion T2 also seems o be con amina ed. This sample was collec ed close o an a i ical s eam which c osses he phosphogypsum s o age a ea. Ups eam his s a ions, he ac i i y concen a ions a e simila o backg ound. F om he esul s i is clea ha he was es om he phospho ic acid p oduc ion enhance he adioac i e concen a ions in bo om sedimen s om he Odiel and Tin o i e s. Howe e , his con amina ion seems o be es ic ed o he es ua ine a ea o he i e s, hus being he adioac i e concen a ions a he coas al a ea simila o backg ound le els. I is also in e es ing o discusse he 21°I>o/210Pb and 210Pb/226Ra ac i i y a ios which a e also gi en in Tables 1 and 2 o Feb ua y and No embe campaigns, espec i ely. The 21 0Po/21°I>b ac i i y a io e eals he exis ence o secula equilib ium in hose s a ions less con amina ed whe eas hose highly enhanced show an excess o 21°I>o compa ed o 21°I>b. The excess is con i med by he alues o his ac i i y a io in s a ions 03, T2 and T3. This excess should e lec ei he a highe p esence o 210Po in he was es om he indus ies o a di e en en i onmen al beha iou a e he elease. Toe excess disappea s downs eam he i e channel. The excess o 210Po ound a s a ion STl, loca ed ups eam om he phosphogypsum piles in he Tin o i e , which seems o be unenhanced by he indus ies, mus be ela ed wi h he highe 21°I>o associa ion wi h solid pa icles. In he case o he 21°I>b/226Ra ac i i y a io, mos s a ions p esen alues which indica e he exis ence o secula equilib ium be ween bo h adionuclides o a li le excess o 210Pb compa ed o 226Ra. Howe e , s a ion 03 om he Odiel i e and T1 om he Tin o i e , p esen a clea excess o 226Ra ela ed o 210Pb (mainly in samples collec ed in Feb ua y) gi en 210Pb/226Ra ac i i y a ios clea ly below uni y. This si ua ion should be explained in di e en ways o each sample. Sample 03, was collec ed a he poin o discha ge om he phospho ic acid indus y in o he Odiel i e . Thus, he excess o 226Ra should indica e he exis ence o a simila excess in he was es. As i is well know, phosphogypsum (mainly CaS04) a e en iched in 226Ra compa ing wi h o he adionuclides ( om he 238U decay se ies.10 The equilib ium is es o ed downs eam he Odiel channel due o a highe associa ion o Pb11 o solid phases as well as o he edissolu ion o 226Ra in saline wa e s.8,12 Toe case o s a ion T1 loca ed ups eam om he indus ies mus be ela ed o a highe p esence o 226Ra in solu ion. Thus, due o he solubili y o his adionuclide in na u al wa e s, eleases o was es wi h high concen a ion o 226Ra would p oduce a gene al inc ease o 226Ra in solu ion in compa e wi h uncon amined i e s. This excess o Ra would p oduce a highe con ain o 226Ra in bo om sedimen s in loca ions upwa ds, compa ed o 21 0Po whk.h has been al eady inco po a ed o he sedimen s. Sw ace soils In Tables 3 and 4 adioac i e concen a ions o he same adionuclides and same ac i i y a ios as hose o bo om sedimen s a e p esen ed he e bu o su ace soil samples om he Odiel we ma shland. In each Table esul s o Feb ua y and No embe campaigns a e p esen ed, espec i ely. Toe esul s e eal clea ly ha he Ma sh is also enhanced by he phospho ic acid p oduc ion.13 Toe ac i i y concen a ions a e, in gene al, below he maxima o�nd in bo om sedimen s om he Odiel i e . Howe e , ac i i y concen a ions up o 370, 660 and 500 mBq/g o 210Po, 210J>b and 226Ra, espec i ely, we e ound in Feb ua y, being in No embe he le els up o 580, 670 and 600 mBq/1 o 210Po, 210Pb and 226Ra, espec i ely. Besides ha , much highe adioac i i y concen a ions we e ound in samples collec ed in he No he n ma sh (see Fig. 1) in he campaign o No embe . In he Odiel i e ma gin o he ma sh, eigh s a ions we e sampled o soils. These loca ed in on o he e ilize indus ies, p esen adioac i e concen a ions in he campaign o Feb ua y only sligh ly abo e backg ound concen a ions, being hose ups eam and downs eam mo e con amina ed. In No embe , he s a ion in on o he indus ies p esen s he lowes adioac i e concen a ions, below he concen a ions ound in Feb ua y. Thus, i seems ha con amina ion in he ans e sal di ec ion is no as high as in he longi udinal di ec ion. O cou se, his ac mus be ela ed wi h he low eloci y o he i e wa e . Toe di e ences in s a ions M20 and M21 be ween bo h Table 3 Radioac i e concen a ions in mB/g in su ace soil samples collec ed a he Odiel we ma shland Code 2JOp0 M6 264 ± 412 M7 290± 31 MIO 341 ± 19 Mll 276± 14 M12 25.1 ± 1.7 M14 108±6 MIS 367 ± 34 M16 117±7 M20 288 ±25 M21 181 ± 14 M22 168±9 M23 124± 8 M24 44.9 ± 2.9 M18 29.0± 1.8 M17 40.5 ±2.3 in Feb ua y 1993 210pb 226Ra 454 ±27 321 ± 40 424 ±29 280± 43 514±36 326± 56 435 ±30 304± 39 37.4 ± 9.1 26.4 ± 14.8 160±25 143 ± 35 658 ± 30 505 ± 44 137 ± 18 65.4 ± 25.4 125 ±20 �241 125 ± 21 � 148 236 ±25 136 ± 36 205 ±23 76.6± 35.9 34.8 ±6.8 33.2 ± 11.4 34.0± 8.4 34.8 ± 13.7 53.2 ± 6.5 43.3 ± 10.5 2H)po¡2JC>pb 0.581 ± 0.043 0.684 ± 0.087 0.663 ± 0.059 0.634 ± 0.054 0.671 ± 0.169 0.675 ± 0.112 0.558 ± 0.058 0.854 ± 0.123 2.30 ±0.42 1.45 ± 0.27 0.716 ± 0.085 0.605 ± 0.078 1.29 ± 0.26 0.853± 0.217 0.761 ± 0.102 21 Opb¡226Ra 1.41 ± 0.20 1.51± 0.25 1.58± 0.29 1.43 ± 0.21 1.42± 0.87 1.12 ± 0.32 1.30± 0.13 2.10±0.86 1.73± 0.50 2.68 ± 1.29 1.05 ± 0.41 0.98± 0.45 1.13 ± 0.33 Table4 Radioac i e concen a ions in mBq/g in su ace soil samples collec ed a he Odiel we ma shland in No embe 1993 Code 210p0 210pb226R_a210p0¡210pb210pb¡226Ra Ml 199± 10 236± 16 166± 25 0.843 ± 0.071 1.42 ± 0.24 M2 778 ± 41 820±27 711 ± 45 0.949 ± 0.059 1.153 ± 0.082 M3 643 ±28 795 ±23 681 ± 36 0.811 ± 0.042 1.167 ± 0.070 M4 210± 11 233 ± 13 242 ± 23 0.901 ± 0.069 o. 963 ± 0.106 M5 222± 11 156 ± 14 161 ± 24 1.42 ± 0.15 0.97 ± 0.17 M6 580±26 673 ± 16 598 ±25 0.862 ± 0.044 1.125 ± 0.054 M7 213 ± 10 287 ± 12 213 ± 21 0.742 ± 0.047 1.347 ± 0.144 M8 130±7 212 ± 14 130± 21 0.613 ± 0.052 1.631 ± 0.285 M9 141 ±7 161 ± 12 149 ± 20 0.876 ± 0.078 1.081 ± 0.166 MIO 188 ± 10 161 ± 13 149 ± 22 1.168 ± 0.113 1.081± 0.182 Mll 64.6±4.0 76.2 ± 12.3 49.0± 18.6 0.848 ± 0.147 1.56 ± 0.64 M12 27.9 ± 2.0 24.8 ± 12.3 46.0± 22.3 1.13 ± 0.56 0.54 ± 0.37 M13 565 ±23 681 ± 23 673 ± 39 0.830 ± 0.044 1.012 ± 0.068 M14 41.0 ± 3.2 18.4 ± 10.1 30.4± 16.5 2.23 ± 1.24 0.605 ± 0.467 M15 441±20 589 ± 21 484± 32 0.749 ± 0.043 1.217±0.091 M16 131 ±7 162 ± 11 134 ± 16 0.809 ± 0.070 1.21 ±0.17 M19 233± 11 268 ± 15 245 ± 26 0.869 ± 0.064 1.094 ± 0.131 M20 16.2 ± 2.5 15.4± 10.1 21.3 ± 16.0 1.05 ±0.71 0.72 ±0.72 M21 37.2 ± 2.5 22.9 ± 10.9 20.3 ± 17.7 1.62 ±0.78 1.12 ± 1.12 M22 44.2±2.5 26.6 ± 11.1 31.7 ± 17.2 1.66 ±0.70 0.84 ±0.57 M23 194±9 121 ± 13 97.3 ± 20.7 1.61 ±0.19 1.24 ±0.30 M18 54.4± 3.7 51.9 ± 11.1 35.3 ± 17.6 0.830 ± 0.044 1.012 ± 0.068 M17 54.7 ± 3.7 51.9 ± 11.1 35.3 ± 17.6 0.68 ± 0.10 2.7 ± 1.7 campaigns mus be ela ed o he composi ion o he samples. Thus, samples collec ed in No embe had highe con en o sand pa icles, which was e lec ed in he densi y (0.7 and 1.5 g/cm3 d y weigh in Feb ua y and No embe , espec i ely), and in he o ganic con en (10% and 1.5%, espec i ely) o he samples. Concen a ions a he eas side o he Sal és island, which clea ly e eals a con amina ion, a e simila o hose ound in bo om sedimen s a he con luence o he Odiel and Tin o i e s (OTl and OT2). Toe di e ences ound in s a ions a he eas side o he Sal és island again mus be pa ially ela ed wi h he composi ion o he samples. Thus, alues o densi y and o ganic con en o s a ions M16 and M14 may e eal ha hey ha e a high amoun o sandy pa icles, which p oduces a dec ease in he speci ic ac i i y o he samples. In gene al, he di e ences i11 adioac i e concen a ions in s a ions along he Odiel i e ma gin could be due o di e ences in o ganic con en . I we nonnalize he adioac i e concen a ions o he o ganic con en o he soil samples, he di e ences ,,,, be ween s a ions a e less signi ica i e. This e ec can be clea ly obse ed in Fig. 3, whe e he 210Po concen a ion in mBq/g a e compa ed wi h he da a no malized o he o ganic con en o hose soils along he Odiel i e ma gin, which showed wide di e ences in composi ion. Only, s a ion M14 does no seem o be con amina ed in he same deg ee as hose s a ions in he icini y. 300 200 100 M21 M20 M19 M13 M14 M15 M16 Fig. 3. Compa ison o 210Po ac i i y concen a ion in mBq/g o d y soil sample (con inuous line) wi h he 21 Üpo ac i i y concen a ion nonnalized o he o ganic con en o he soil samples (dashed line) collec ed along he Odiel i e bank o he Odiel ma sh in No embe 1993. Da a o no malized concen a ions (in mBq/g) ha e been di ided by 10 Besides, ha , a se o samples appea s in which he in luence o he was es eleased om he indus ies is clea ly e lec ed. Thus, soils along he Moja e a channel ha e qui e high adioac i e concen a ions. I we conside ha he cause o he high ac i i y concen a ions ound in sedimen s O 1 and 02 was he mo emen o he con aminan s ups eam he Odiel i e du ing high ide, his should be also he cause o he con amina ion along he Moja e a channel. Thus, du ing he high ide he Odiel i e wa e lows ups eam. Pa o his con amina ed wa e will low o he No hem ma sh and he o he pa will lood he Odiel ma sh h ough he no h o he Bacu a island. The same could occu h ough he sou h o his island. O his mos o he con amina ed wa e lows in o he Moja e a channel and a small pa would low in o he Cha e channel. The ac i i y concen a ion a he No hwes o he Enmedio island dec eases downs eam hc Cha e channel and he Pun a Umb ía i e , whe e backg ound concen a ions o 210Po. 210Pb and 226Ra we e ound. Thus, he pa em dis ibu ion o adioac i i y concen a ions in soils ac oss he ma sh has clea ly iden i ied he way o