Radioac i i y le els in ae osol pa icles su ounding a la ge
TENORM was e eposi o y a e applica ion o
p elimina y es o a ion wo k
E. Bo ego, J.L. Mas⁎, J.E. Ma ín, J.P. Bolí a , F. Vaca, J.L. Aguado
Dp o. de Física Aplicada, Campus de El Ca men, Uni e si y o Huel a, 21071 Huel a, Spain
Recei ed 1 Sep embe 2006; ecei ed in e ised o m 16 Janua y 2007; accep ed 22 Janua y 2007
A ailable online 6 Ma ch 2007
Abs ac
In his pape ,
238
U-se ies adionuclides ha e been analysed in pa icula e ma e samples collec ed a a phosphogypsum s ack
sys em loca ed nea he ci y o Huel a (SW Spain) du ing he cou se o 1 yea . The esul s ha e been compa ed o hose collec ed a
a e e ence (backg ound) si e loca ed a ew km away, in o de o es ablish i he s ack sys em p o okes an inc ease in adionuclide
exposu e due o inhala ion wi h pa icula e ma e . The
222
Rn p ogeny, which is conside ed a e y impo an con ibu o o he
in e nal dose a e ecei ed by he popula ion, was collec ed o 6 mon hs. The esul s indica e ha o se e al ypes o adionuclides
he e is a signi ican inc ease in he adioac i i y adso bed by he ae osol pa icles collec ed a phosphogypsum s acks. The iso ope
analysis indica es ha his inc emen could be a ec ed by he wa e apou emissions om he ac o y, which con ain high
concen a ions o hese adionuclides. Howe e , he majo i y o hese adionuclides could no be de ec ed a he backg ound
loca ion. The co esponding dose inc emen es ima ed a he sampling poin is, howe e , negligible. This ac is a consequence o
he e y small adionuclide concen a ion inc emen , oge he wi h ela i ely conse a i e na u e o he occupa ional ac o applied.
Rega ding he Rn p ogeny, no signi ican di e ences be ween ei he he collec ing si es has been egis e ed due o o he dominan
wind egime a he sampling loca ions.
Keywo ds: Na u al adioac i i y; TENORM; ae osol; esuspension
1. In oduc ion
I is es ima ed ha mo e han a hal o o al
adioac i e dose a e ecei ed by wo ld's popula ion is
associa ed o adioac i i y inhala ion ia ae osol pa i-
cles (UNSCEAR, 2000). A loca ions a om nuclea
indus ial ac i i ies, only adioac i e allou ( ela ed o
a mosphe ic nuclea es s du ing he 1950s and 1960s)
and na u al adioac i i y should be conside ed om he
in e nal dose poin o iew. Howe e , backg ound le els
o adionuclides in ae osol pa icles can be enhanced
due o indus ial p ocesses in ol ing NORM (Na u ally
Occu ing Radioac i e Ma e ial) wo k ac i i ies, one o
hese being he p oduc ion o phospho ic acid using
phospha e ock. This sedimen a y aw ma e ial usually
con ains high concen a ions o adionuclides belonging
o he na u al
238
U-se ies:
238
U-se ies ac i i y concen-
a ions anging om 200 up o 2000 Bq/kg ha e been
epo ed, whe e
238
U is in secula equilib ium wi h i s
⁎ Co esponding au ho . Dp o. de Física Aplicada I, E.U.P.,
Uni e si y o Se ille, 41012 Se ille, Spain. Tel.: +34 620048967;
ax: +34 954559967.
E-mail add ess: [email p o ec ed] (J.L. Mas).
doi:10.1016/j.sci o en .2007.01.098
daugh e s (Bolí a e al., 1996; Azouazi e al., 2001).
These alues a e up o 100 imes highe han hose co -
esponding o an a e age soil which is a ound 20 Bq/kg
o
238
U. This adionuclide is usually close o secula
equilib ium wi h i s daugh e s (UNSCEAR, 2000).
Du ing he indus ial p ocess, he secula equilib ium
condi ions exis ing in he aw ma e ial a e al e ed, and a
by-p oduc called phosphogypsum (PG, mainly CaSO
4
·
2H
2
O) is o med, which also con ains a ce ain amoun
o phospho ic acid (abou 1% con en s in P
2
O
5
). Di -
e en ac ions o he hea y me als and na u al adio-
nuclides con ained in he phospha e ock a e hus
eleased wi h he PG. Hence, he di e en adioac i e
iso opes eleased om he aw o e a e ca ied by ei he
he phospho ic acid o he gene a ed by-p oduc , acco d-
ing o hei espec i e elemen a y chemical beha iou .
In he p e ious s udies pe o med o he plan s
loca ed a Huel a, i has been ound ha a majo ac ion
o Ra iso opes (mo e han 95%), Th iso opes (∼70%)
and a smalle ac ion o U iso opes (∼15%), ollow he
by-p oduc (Bolí a e al., 1996; Pé ez-Mo eno, 2005).
The p esence o high concen a ions o
226
Ra in he PG
(a e age alue o abou 650 Bq/kg, Mas e al., 2006)is
e y impo an om he adiological poin o iew:
226
Ra is he pa en adionuclide o he noble gas
adioiso ope
222
Rn, whose sho -li ed daugh e s a e
esponsible o an impo an ac ion o he o al in e nal
dose ecei ed by he popula ion.
Du ing he pas 40 yea s, di e en acili ies de o ed
o he p oduc ion o phospho ic acid, and loca ed in he
su oundings o he ci y o Huel a (SW Spain), ha e
eleased a PG o al amoun o abou 8×10
7
onnes. Un il
1997, 80% o he PG gene a ed by his e ilize
indus ial complex was s o ed in nea by sal ma shes.
This disposal si e p esen ly co e s abou 1200 Ha, a
si ua ion conside ed by he scien i ic communi ies as a
adiological anomaly.
Due o he p oximi y o he PG s acks o he ci y o
Huel a (less han 2 km) and as consequence o he
in ensi ying social ala m gene a ed o e he yea s, he
egional au ho i ies ha e been ca ying ou di e en
es o a ion wo k om he beginning o he 1990s.
Among hese ac i i ies, mo e han 50% o he su ace o
he PG s acks has been co e ed wi h successi e laye s o
di e en ma e ials including na u al soils, building by-
p oduc s and neu alised indus ial was e.
The p incipal conce n o his wo k is o check he
exis ence o an ex a adioac i i y supply h ough ai
om he phosphogypsum s acks, and, i ound, o
es ablish i s en i onmen al and adiological impac .
Acco ding o he p e iously explained p oblem, a ge
adionuclides a e na u ally occu ing adionuclides
associa ed o he gypsum s acks (
238
U,
234
U,
230
Th,
226
Ra,
222
Rn and
210
Pb). Besides he ac ha many
pape s ha e been de o ed o he adiological impac on
he aqua ic sys em ha su ounds he PG s acks (Bolí a
e al., 1996, 1995; Mas e al., 2001), o he bes o ou
knowledge he e a e no e e ence da a o adioac i i y
con ained in he ae osol pa icles in his s udy a ea.
Hence, one o he majo objec i es o his wo k is o
cla i y he adiological impac (i.e., he dosime ic
inc emen abo e he backg ound le el) on bo h local
popula ion and wo ke s wi hin h ough he inhala ion o
bo h
222
Rn p ogeny and long-li ed na u al adionuclides
in ae osol pa icles. Wo ke s could be exposed o an
inc ease o inhaled adioac i i y du ing hei wo king
ime a he PG s acks. The popula ion could be exposed
as a consequence o he p oximi y o bo h he PG s acks
and he ac o ies o he ci y (see below o de ails).
2. Ma e ials and me hods
2.1. Ai sampling
An ex ensi e sampling campaign was ca ied ou
du ing he cou se o 1 yea (24 May 2002 o 16 May
2003) a wo di e en sampling loca ions. The i s
selec ed poin is loca ed o e he PG s acks whe e he
ex e nal exposu e eaches i s maximum alue (Mas
e al., 2006). The maximum occupa ional ac o is also
loca ed a his poin . The second sampling poin is
loca ed 25 km away om he PG s acks (see Fig. 1).
This loca ion is selec ed in o de o ob ain a backg ound
e e ence le el.
To al suspended pa icles (TSP) we e collec ed in
ibe glass il e s using a high- olume pumping sys em
CAV-A/HF (MCV, Ba celona, Spain), keeping sampling
low a e a a alue o 30 m
3
/h. Each sample was
collec ed o e a pe iod o 3 weeks, wi h an e ec i e
collec ion ime o 1 week. This is he ime in which he
il e ends o each sa u a ion and i s ae osol pa icles
collec ion e iciency becomes d as ically educed.
Sampling was pe o med using cycles o 240 min
du ing 3 weeks consis ing o an 80-min sampling pe iod
ollowed by a s op pe iod o abou 160 min. Unde hese
condi ions, du ing a sampling pe iod o 3 weeks, he
pause episodes successi ely co e di e en pe iods un il
a whole day is scanned. This sampling scheme was
selec ed as a comp omise be ween he objec i es o he
s udy and se e al echnical and ope a i e equi emen s
(see below o de ails).
Ae osol pa icles we e e ained on o 12-cm diame e
Wha man A bo osilica e ibe glass il e s. The deposi ed
mass was de e mined by a g a ime ic me hod, i.e., he
28 E. Bo ego e al. / Science o he To al En i onmen 377 (2007) 27–35
ae osol pa icles mass was de e mined by sub ac ing
he mass il e om he o al mass a e sampling (and
a e ha ing desicca ed o a cons an weigh ). To his
end, an elec onic weighing machine wi h 0.1 mg
p ecision was used. Sampled o al mass was always
wi hin a ange o 0.1–0.3 g.
Radionuclide ac i i y concen a ions we e de e -
mined using ei he con en ional alpha o gamma
spec ome y, as desc ibed below. F om hese concen-
a ions, only hose long hal -li e adionuclides om
238
U-se ies ha e been inally used in his s udy.
Cosmogenic adionuclides such as
7
Be a e beyond i s
scope.
To al adon p ogeny con en was egis e ed by
moni o ing as desc ibed below a he same loca ion as
pa icula e ma e , only o e he cou se o 6 mon hs; he
backg ound loca ion was moni o ed o 1 mon h.
2.2. Radioac i i y measu emen
The
238
U,
234
U and
230
Th le els we e measu ed by
alpha pa icle spec ome y. The
210
Po was no de e -
mined due o he long decay ime elapsed a e he
sampling. Besides he ac ha analy ical co ec ions a e
possible, he e a e se e al easons o hei a oidance in
his wo k: (1) he magni ude o he ela i e unce ain ies
so in oduced (i.e., a e passing a long ime be ween
sampling and analysis) is so high he quali y o he
in o ma ion so achie ed is d as ically educed, and (2)
his de e mina ion would equi e a eplica ion o each
analysis a di e en imes, he eby p o oking a d as ic
educ ion o he il e mass a ailable. A he p esen ime,
howe e , a new sampling me hodology is being applied
in o de o acili a e an immedia e analysis o il e
samples, o example, he
210
Pb/
210
Po disequilib ium is
applied o ob ain he calcula ion o ai mass esidence
ime. Alpha pa icle spec ome y was pe o med using
an EG and G ORTEC SOLOIST-U0450 sys em,
consis ing o eigh independen chambe s, each wi h an
implan ed silicon ba ie de ec o . Coun ing ime pe
sample was abou 3 days depending on he ac i i y le el.
In his case, a adiochemical me hod was p e iously
applied o each il e o sepa a ion and isola ion o alpha
emi e adionuclides.
The isola ion o U and Th iso opes was ca ied ou
acco ding o a chemical ex ac ion me hod de eloped by
Holm and Fukai (1977) and was con enien ly adap ed o
ou ope a ional equi emen s (Bolí a e al., 1996). The
chemical yields (which a e wi hin he ange 40–70%)
we e calcula ed by using he in e nal s anda d echnique
a e addi ion o abou 40 mBq o
232
U and
229
Th.
I is necessa y o conside he ac i i y added by he
ibe glass ma e ial (i.e., he blank le els) in o de o
co ec he calcula ed concen a ions, especially bea ing
in mind he ela i e mass di e ence be ween he il e
i sel and he TSP mass. To ake his con ibu ion in o
Fig. 1. Loca ion o he wo sampling poin s in Huel a p o ince (SW
Spain). One o loca ion, PGS, is he phosphogypsum s ack which a e
sp ead along he eas bo de o Huel a own, whe eas he o he
sampling poin , INTA, is in a esea ch cen e loca ed in a pine ee a ea
nea Doñana Na ional Pa k.
29E. Bo ego e al. / Science o he To al En i onmen 377 (2007) 27–35
accoun , bo h U and Th-iso opes we e measu ed in h ee
il e s om each comme cially a ailable ba ch o 25
il e s. The blank ac i i ies o hese adionuclides we e
wi hin a ange o 1–4 Bq/kg.
The
226
Ra and
210
Pb we e measu ed by gamma
spec ome y using a coaxial ge manium X Ra (Ex end-
ed Range) de ec o (Canbe a GX3519; 38% ela i e
e iciency) which included passi e shielding (a 15 cm-
hick Fe laye ). The
226
Ra was measu ed h ough he
352-keV emission o i s daugh e
214
Pb once secula
equilib ium was eached in he sample (a e 3 weeks).
On he o he hand,
210
Pb was analysed h ough i s
46.5 keV gamma emission. Whe eby each ci cula il e
was olded 3 imes o a 45° sec o o a ci cle and
w apped wi h plas ic pape be o e analysis. Coun ing
ime was 1 week. E iciency calib a ion was pe o med
acco ding o a me hodology de eloped in ou labo a o y
in o de o ake in o accoun he g ea hickness
di e ences be ween il e samples and common,
liquid/solid ma ices (Ma ínez-Ruiz e al., 2006).
Finally, adon p ogeny was measu ed using a TN-
WL-02 moni o (Thompson Nielsen elec onics L d.,
Canada) ensemble ha includes a pump o ai sampling,
wo king a a low a e o 1 L/min. Sucked ai is o ced o
pass h ough a 0.45-μm Millipo e il e , whe e ae osol
pa icles, including hose wi h adso bed Rn-p ogeny
a oms, a e e ained. The il e is loca ed opposi e a
semiconduc o de ec o whe e alpha emissions p oduce
he gene a ion o pulses which a e egis e ed in a digi al
pulse eco de . This il e is changed e e y 2 days, and
da a o
222
Rn, in Bq/m
3
, a e p oduced e e y 15 min.
Due o he sensi i i y o he de ec o o alpha emissions
om he sho hal -li e Rn p ogeny, he physical
magni ude de e mined is he equi alen equilib ium
concen a ion (EEC), which is he magni ude o in e es
ega ding dosime ic e alua ions.
An es ima ion o he e ec i e doses ecei ed h ough
inhala ion by people in he p oximi y o he gypsum
s acks could be pe o med. To his end, he co esponding
dose a e ac o s p oposed in UNSCEAR (2000) should
be applied. Howe e , i is necessa y o bea in mind ha
dose a e ecei ed h ough inhala ion depends on many
ac o s ha ha e been no analysed in his wo k, such as
g ain size, adionuclide solubili y, abso p ion a e in body
luids, e c. As hese pa ame e s a e beyond he scope o
his wo k, only a aw es ima ion could be made. This has
been pe o med assuming ha (1) Th abso p ion a e is
slow (abso p ion ype “S”) and (2) he abso p ion a e o
he emaining adionuclides is medium (abso p ion ype
“M”). The limi a ions o hisme hodology on he abili y o
p edic he accu a e dose a es a e discussed in he nex
sec ion.
3. Resul s and discussion
3.1. To al suspended pa icles (TSP)
Indi idual da a o TSP a bo h si es a e gi en in
Fig. 2. A gene al co ela ion be ween he wo da a se s
can be ound he e. I is obse ed ha he highes alues
a bo h loca ions occu du ing he summe , e lec ing
ha ypical me eo ological condi ions in his season
(less ain all and humidi y, highe empe a u es, g ea e
a mosphe ic s abili y) a ou he ae osol o ma ion. In
he case o PG s acks, da a imply an annual a e age
alue o 49.1±19.0 μg/m
3
. This alue is in ag eemen
wi h p e iously published alues o he ci y o Huel a
(50 μg/m
3
,Que ol e al., 2002). Howe e , i is g ea e
han ha o INTA (33.1±11.3 μg/m
3
) since indi idual
da a a PG s acks a e sys ema ically highe han hose
aken a he backg ound loca ion. Indeed, when he a io
o TSP con en s is pe o med o each sampling pe iod,
i is always g ea e han one, wi h an a e age a io o
1.65±0.22. This beha iou indica es ha he e exis s a
local sou ce o ae osols ha inc eases he TSP in his
zone. Ne e heless, his inc emen is mainly due o he
ac ha he PG s acks a e in mo e indus ial and u ban
su oundings han INTA, and no due o a con ibu ion
om he PG s acks. They o med he eas bo de o he
ci y o Huel a and an impo an indus ial complex is
loca ed in he sou h o he ci y in he con luence o he
Odiel and Tin o i e s. The adionuclide ac i i ies (
238
U,
230
Th and
226
Ra) should imply ei he suppo o
con adic ion o his hypo hesis, by showing i he
Fig. 2. TSP con en , in μg/m
3
, a he wo sampling poin s om 24 May
2002 o 16 June 2003. Gaps in he da a indica ed e lec ha he ai
sample had b oken down.
30 E. Bo ego e al. / Science o he To al En i onmen 377 (2007) 27–35
o igin o such a possible TSP enhancemen could be due
o PG. This ac will be discussed in he ollowing
sec ions.
3.2. U iso opes
Fig. 3 shows he
238
U (and
230
Th and
226
Ra) con en ,
in Bq/kg, in he ae osol samples collec ed a he PG
sampling poin . Values o
234
U a e no shown since
hey a e simila o hose o
238
U and e lec he secula
equilib ium be ween hem. These esul s ange om 6.6
o 29.2 μBq/m
3
wi h an a e age ac i i y o 16.0±
6.1 μBq/m
3
. The associa ed unce ain y is in his case
he s a is ical dispe sion o he da a se ins ead o he
s anda d de ia ion. Unce ain y is calcula ed as he
mean s anda d de ia ion. These da a a e in ag eemen
wi h p e ious alues epo ed o he ci y o Huel a by
Que ol e al. (2002). Thei alues a e u he mo e
simila o ou da a o maximum alues, hough clea ly
smalle han hose o he e e ence o minimum alues
(7 imes less) and app oxima ely 50% less o mean
alues. I is wo h o no e ha he a e age concen a ion
(μBq/m
3
) is up o 16 imes highe han he e e ence da a
o ai concen a ions (UNSCEAR, 2000). On he o he
hand, he
238
U con en s, in Bq/kg, ange om 141 o
653 Bq/kg, wi h an a e age ac i i y o 354±145 Bq/kg.
These alues a e clea ly highe han he a e age
238
U
con en in a ypical soil (UNSCEAR, 2000). In he case
o he INTA sampling poin ,
238
U ac i i y was below
ou minimum de ec able ac i i y (abo e 5 Bq/kg).
Conside ing he lowe alues epo ed in he ci y o
Huel a o
238
U, his ac seems o e lec ha he e is a
con ibu ion o TSP in u anium associa ed wi h PG
s acks and e ilize plan s, which a e loca ed qui e close
o PG s acks. These u anium con en s mus ha e hei
o igin no only in he esuspension o s acked PG, bu
also ei he in he e apo a ion o wa e s used in i s ans-
po o in he gaseous emissions om he ou e ilize
plan s, as i is well known ha he apou emissions
con ain signi ican ac ions o esidual phospho ic acid
which is en iched in U (Bolí a e al., 1996). Phospho ic
acid con ained in hese apou emissions ha e concen-
a ions in he ange o 1 kBq/kg o
238
U, o he s o ed
PG he ac i i y concen a ion is abou 70 Bq/kg, and o
wa e s used in he eci cula ion sys em his concen a-
ions is ela i ely uni o m, a ound 200 Bq/kg (Pé ez-
Mo eno, 2005). Hence, he p e iously shown high U
concen a ions could be associa ed o hese sou ces.
Maximum concen a ions o
238
U a e ound in
Sep embe and Feb ua y, co esponding o minima TSP
con en s. Indeed, he u anium con en s (μBq/m
3
)inTSP
a e a iable h oughou he yea and a e g ea e in summe
when he o ma ion o ae osols is a ou ed. As p e iously
indica ed, he enhancemen o U concen a ion in TSP
could be ela ed o sou ces gene a ed by liquid ae osol
pa icles, a possibili y ha is e lec ed in he ac ha he e
is no TSP inc ease when he U concen a ion inc eases.
Hence, he mos p obable hypo hesis is he U associa ion
o liquid ae osol pa icles emi ed om he wa e
eci cula ion o he e ilize plan s.
Using a me hodology p oposed by Be g e al. (1994),
en ichmen ac o s (EF) could be used in o de o
cha ac e ize how he ae osol pa icles a e en iched in
di e en analy es. To his end, a e e ence alue o
su ounding soil should be de ined, and, acco ding o
p e ious e e ences, in Table 1 hese e e ence alues
ha e been de ined o ou geog aphical a ea. Fo
238
U,
en ichmen ac o s (EF) lie wi hin he ange 5–22, wi h
an a i hme ic mean o 12. These EF alues a e e y high
and he e o e indica e a e y impo an con ibu ion o
he ae osol pa icle composi ion om an addi ional
sou ce di e en om c us al soil. I is wo h men ioning
ha , acco ding o Que ol e al. (2002), c us al soil seems
o be esponsible o mo e han 40% o he TSP mass
collec ed a he ci y o Huel a o e he cou se o a yea
and a hal . Abou 24% seems o be o an h opogenic
o igin. Le us emembe , howe e , he di e ences
Table 1
Re e ence alues o adionuclide con en s o he di e en ma e ials
possibly con ibu ing o he TSP mass
Radionuclide
226
Ra (Bq/kg)
230
Th (Bq/kg)
238
U (Bq/kg)
Co e soil 26 20 20
Phosphogypsum 620 280 140
Reci cula ion wa e 2 2 200
Fig. 3. The
238
U,
230
Th and
226
Ra ac i i ies, in Bq/kg, a he PG s acks.
Gaps in he da a e lec a le el below ou minimum de ec able ac i i y.
31E. Bo ego e al. / Science o he To al En i onmen 377 (2007) 27–35

be ween bo h collec ion si es. The sampling poin a he
PG s acks is loca ed qui e close o indus y; hence,
al hough he equency o wind p ecludes a con inuous
indus ial e ec , umiga ion e en s om bo h nea by
chimneys and unco e ed gypsum s acks a e possible.
Fu he mo e, i is necessa y o emembe ha he
sampling si e is su ounded by a eci cula ion wa e
sys em, om whe e ae osol pa icles con aining ela-
i ely high u anium con en s could be esuspended and
subsequen ly inco po a ed in o he il e s. This possi-
bili y will be analysed in de ail unde he ligh o esul s
o o he adionuclides.
3.3. The
226
Ra and
230
Th
Fig. 3 shows he
226
Ra and
230
Th con en s, in Bq/kg,
in he ae osol samples collec ed a he PG sampling
poin . In he case o
226
Ra, esul s ange om 64.6 o
600 Bq/kg (2.8 o 18 μBq/m
3
) wi h an a e age ac i i y
o 221±136 Bq/kg (10.3±4.1 μBq/m
3
), and in he case
o
230
Th, om 59.7 o 360 Bq/kg (2.99 o 24.0 μBq/m
3
)
wi h an a e age ac i i y o 162±76 Bq/kg (10.3±
4.1 μBq/m
3
). As in he case o
238
U, he a e age ac i i y
concen a ion alues (μBq/m3) he e epo ed a e up o
20 (
230
Th) and 10 (
226
Ra) imes highe han he e e ence
da a (UNSCEAR, 2000). The maximum concen a ions
a e once again associa ed o he minimum TSP alues, as
in he case o
238
U. These ac i i y concen a ions a e
clea ly highe han hose co esponding o ypical soils.
In he case o he INTA sampling poin , ac i i ies we e
again below he le el o ou minimum de ec able ac i i y
(in he ange o 100 Bq/kg o
226
Ra and 5 Bq/kg o
230
Th depending on he measu ing ime). These esul s
con i m he p e iously men ioned o igin o he ae osol,
i.e., ha he en ichmen can be associa ed o he liquid
ae osol pa icles since Ra and Th con en s in phospho ic
acid a e abou one o de o magni ude less han hose o
U. Howe e , i he only o igin o his con ibu ion we e
he esuspension o s acked PG, acco ding o published
da a (in he ange o 220 Bq/kg o
230
Th and 650 Bq/kg
o
226
Ra, Mas e al., 2006), he
226
Ra and
232
Th TSP
con en s should be conside ably highe han hose esul s
shown he e, i.e., highe han hose e lec ed o
238
U.
Acco ding o Pé ez-Mo eno (2005),
226
Ra/
238
U
iso ope a ios a e cha ac e is ic and well known bo h
o PG (app oxima ely 5) and liquid ae osols coming
om he eci cula ion sys em and om he gaseous
emissions om he e ilize plan s (1/40). Hence, his
iso ope a io could be used as a ace o inge p in o
he sou ces gene a ing he TSP con ained in he il e s. A
simila easoning could be applied o he iso ope a io
230
Th/
238
U. Howe e , he ela i e magni ude o a ia ion
o his iso ope a io is no as high as ha o
226
Ra/
238
U,
and he e o e i has been no used in his wo k.
The a e age alue o
226
Ra/
238
U iso ope a io is
app oxima ely 0. 71 ( anging om 0.17 o 1.61), as can
be seen in Fig. 4. This ac con i ms ha he e is a
con ibu ion o solid pa icula e ma e ial associa ed o
he PG s acks ha should be ela ed wi h he di e ence
o TSP be ween he wo loca ions (wi h an a e age
inc emen o 16 μg/m
3
).
3.4. The
210
Pb
The
210
Pb da a a e plo ed in Fig. 5. Mean concen a-
ion a he PG s acks is abou 0.6 mBq/m
3
.This alueis
Fig. 5. The
210
Pb ac i i y, in Bq/kg, a he PG s acks and a he back-
g ound loca ion.
Fig. 4. The
226
Ra/
238
U ac i i y a io a he PG s acks.
32 E. Bo ego e al. / Science o he To al En i onmen 377 (2007) 27–35
compa able wi h da a in he li e a u e o egions ha ing
simila la i udes (Ca alho, 1995). As opposed o he case
o
238
Uand
226
Ra, he
210
Pb concen a ions a e pe ec ly
de ec able a he backg ound loca ion, yielding concen-
a ion anges (0.2–0.9 mBq/m
3
) simila o hose o he
PG s acks. Indeed, he a io o
210
Pb concen a ion a he
PG s acks agains ha a he backg ound s a ion a ies
wi hin a e y na ow ange (0.3–4) wi h a mean alue o
1.10. This esul seems o indica e ha he e is no
sys ema ic inc ease o
210
Pb a he PG s acks since he
supply o his adioiso ope coming om he PG s acks and
he su ounding indus ial a ea is negligible in compa ison
wi h he ele a ed concen a ions due o
222
Rn decay.
Bea ing in mind he p e iously men ioned en ichmen in
he o he adionuclides his ac could esul sligh ly
su p ising. Howe e , i con i ms he p e ious esul s
acco ding o he ollowing easoning.
I is expec ed ha when soil esuspension is ela ed o
he o igin o TSP, he TSP mass amoun and he
210
Pb
concen a ion inc ease oge he (Ca alho, 1995). I
highe concen a ions o
210
Pb we e associa ed o lowe
TSP alues, ha would indica e ha a signi ican
ac ion o he measu ed iso ope is associa ed o he
decay o
222
Rn p esen in he ai , mo e han o pa icle
esuspension om he soil. When
210
Pb concen a ions
a e exp essed in e ms o mass ac i i y (Bq/kg), i is
ound ha hey a e almos sys ema ically highe a he
backg ound loca ion ( he only excep ion is qui e close o
uni , 0.87), wi h a ange o 1.2–4.1 and a mean alue o
1.78. This ac i s shows ha he e is no addi ional
sou ce o his adionuclide a he PG s acks and second,
i is con i ming he highe TSP ange a his poin . Unde
hese condi ions, i should be expec ed ha he PG
s acks ae osol pa icles a e cha ac e ised by a
210
Pb
con en less han ha o he backg ound loca ion. This
hypo hesis is con i med by he esul s: he mean
concen a ion (exp essed in Bq/kg) a PG he s acks is
13.6 k Bq/kg, and o he backg ound loca ion is 19.0 k
Bq/kg, and he backg ound/PG s acks a io o ac i i y
pe mass is 1.40. This alue is simila o ha o he
backg ound/PG s acks a io o TSP.
3.5. The
222
Rn and p ogeny
Da a o
222
Rn a e shown in Table 2. I is obse ed,
in i s place, ha a e age mon hly adon alues a PG
s acks, and also he co esponding s a is ical dispe sion
and anges, we e simila h oughou he sampling.
Mo eo e , backg ound alues (12.7±5.7 Bq/m
3
) a e
ypical o coas al a eas (UNSCEAR, 2000). This
inding may be unexpec ed bea ing in mind ha he
adon exhala ion a es in he PG s acks a e 5 o 10
imes highe han hose o local soils. A g ea e adon
concen a ion a he PG s acks sampling poin would be
expec ed ins ead o simila esul s. This homogenei y
can be unde s ood in he ollowing way: acco ding o
he analysis o he wind da a, he e a e almos no
s agna ion e en s nea he ci y o Huel a (Adame,
2005). Indeed, he wind calm ela i e equency is less
han 10%. This ac is explained by he p oximi y o
he A lan ic Ocean and he usual b eeze ci cula ion,
which es ablishes a wind egime ha p ecludes bo h
s agna ion and eci cula ion and induces a high en i-
la ion egime.
The e o e, al hough PG s acks ac as a local sou ce o
adon, he inc emen o adon p ogeny con en s in ai
mus be being dilu ed as consequence o he dispe sion
p oduced by he dominan winds, hence no addi ional
e ec is egis e ed a he PG sampling poin . Tha could
also be he eason why he maximum alues a PG
s acks a e up o h ee imes highe han hose measu ed
a backg ound loca ion, i.e., he e ec o a highe
exhala ion is el wi h high maximum alues al hough
he wind d i en dilu ion e ec p e en s a d as ic adon
concen a ion a ha loca ion. In his sense, he adon
da a se shows a ce ain nega i e co ela ion ( =−0.8)
wi h wind speed independen o he dominan add ess,
acco ding o wind da a (Adame, 2005).
Secondly, i is in e es ing o see ha ha a e age
alues co esponding o nigh (∼17.7 Bq/m
3
)a e
app oxima ely wice hose collec ed du ing he day
(∼9.0 Bq/m
3
). Fu he mo e, he a e age wind speed
du ing he nigh b eeze episodes is less han ha o day
b eeze in he same way, as hei co esponding
dispe sion abili y. This ac was expec ed since i is
known ha he noc u nal coas b eeze usually induces
he mal in e sion episodes (Adame, 2005). The he mal
in e sion es ic s he e ical mixing o he lowe laye s
o ai and, in his way, i p e en s he dilu ion o adon
concen a ion.
Table 2
Rn concen a ions (Bq/m
3
) and hei s anda d de ia ions (SD, Bq/m
3
)
a he PG s acks and a he backg ound loca ion INTA (selec ed
backg ound sampling s a ion)
Sampling loca ion/mon h A e age
(Bq/m
3
)
SD
(Bq/m
3
)
Minimum
(Bq/m
3
)
Maximum
(Bq/m
3
)
PG/Janua y 11.7 2.6 3.8 29.4
PG/Feb ua y 9.8 2.0 18 36.2
PG/Ma ch 10.8 2.2 3.5 20.1
PG/Ap il 8 1.8 3.1 34.4
PG/May 15.1 6.0 4.8 37.9
PG/June 18.2 6.9 3.4 67.1
INTA/June 12.7 5.7 6.2 22.7
33E. Bo ego e al. / Science o he To al En i onmen 377 (2007) 27–35
As p e iously concluded, despi e he e is a clea
inc emen o adioac i i y (
238
U,
230
Th,
226
Ra) in
ae osol pa icles o he zone unde s udy due o he
p esence o PG s acks, he e is no in
210
Pb olume
ac i i y concen a ions. As p e iously explained, how-
e e , he e is s ill a ce ain lack o da a on necessa y
physical and biochemical pa ame e s o an accu a e
es ima ion o he doses ecei ed by inhala ion. A aw
es ima ion o he co esponding dosime ic con ibu ion
is gi en in Table 3, oge he wi h he dose a e ac o s
used, in spi e o he limi a ions o his me hodology. Fo
his calcula ion: (i) adioac i e equilib ium is assumed
among
234m
Pa,
234
Th and he pa en
238
U; (ii) he
a e age ac i i y inc eases a e calcula ed by sub ac ing
he minimum de ec able ac i i y ob ained a INTA
sampling poin om he mean ac i i y measu ed a he
PG sampling poin ; (iii) he ne ac i i y inc emen s a e
con e ed o dose using he co esponding inhala ion
ac o s p o ided by he Spanish egula ions (which
ollows he EURATOM'96 di ec i e on p o ec ion
agains ionizing adia ion, R.D. 173, 2001); and (i ) a
b ea hed yea ly ai olume o 8030 m
3
is assumed pe
adul o he popula ion (UNSCEAR, 2000) and a
ela i ely conse a i e occupa ion ac o o 0.2 (o e
40 h pe week du ing 48 weeks). Due o he simila i ies
o he adon concen a ions a all he sampling poin s, no
inc emen is concluded o i . Fu he mo e, as p e i-
ously explained, “S”abso p ion ype has been assumed
o Th, while ype “M”has been assumed o he o he
adionuclides. This assump ion mus be kep in mind, as
he ela i e con ibu ion o each adionuclide o he dose
ecei ed by inhala ion would be highe han p edic ed in
his wo k by a ac o in he ange o 2–4 i he
abso p ion ype we e di e en han assumed (i.e., “M”
o Th ins ead o “S”and he e e se o he emaining
adionuclides).
Unde he p e iously men ioned condi ions, he
e ec i e dose a e inc emen (i.e., a he phosphogypsum
s acks in compa ison wi h he backg ound loca ion) is in
he ange o 0.71 μS pe yea . This alue is low
compa ed o he limi s o dose a e inc emen s
es ablished by bo h Spanish egula ions and he
Eu opean Di ec i e (1 mS /yea o he gene al
popula ion is he mos es ic i e limi ). Such a ac is a
consequence o he e y low adionuclide concen a-
ions, in addi ion o he p e iously men ioned en ich-
men in he ae osol pa icles collec ed a he analysed
si e. Indeed, his con ibu ion appea s negligible agains
he calcula ed backg ound o al e ec i e dose a e
(including con ibu ions such as adon and p ogeny,
ex e nal dose a e due o adionuclides in soil and cosmic
ays) in his a ea, which is app oxima ely 2.4 mS /yea
(Mas e al., 2000). Howe e , a mo e de ailed analysis
could be pe o med once addi ional de ails a e known,
and his wo k is o be unde aken by his g oup in he nea
u u e.
4. Summa y and conclusions
Acco ding o ou esul s, ae osol pa icles collec ed a
he Phosphogypsum s acks show an ex a con en in
adioiso opes p esen in was es associa ed o phospho ic
acid p oduc ion. The dosime ic con ibu ion seems o be
negligible when compa ed o bo h he egula ion limi s
o he popula ion and he backg ound le els. Howe e ,
his conclusion is no ye de ini i e as u he wo k,
including he de e mina ion o pa icle g ain size and
adionuclide solubili y, mus be ca ied ou . The esul s
he e shown sugges he need o accu a e es ima ions o
he doses ecei ed by wo ke s wi hin he ac o ies
de o ed o he p oduc ion o phospho ic acid.
No p e ious in o ma ion has been published on he
dose a e inc emen s due o adioac i i y con ained in ai
be o e beginning es o a ion wo k. I is impossible
he e o e o ca y ou a compa a i e s udy; howe e ,
addi ional in o ma ion could be supplied when he
es o a ion wo k is inished. I is wo h men ioning
howe e ha wa e s u ilized o he anspo a ion o he
PG o he s acks use o be dumped in o he Huel a es ua y,
and he unco e ed a ea used o be g ea e han now.
Acknowledgemen s
Thanks a e due o M . F ancisco Ga alda and D .
Beni o de la Mo ena (Na ional Ins i u e o Ae ospace
Table 3
Es ima ion o he dose inc emen due o he p esence o an ex a inpu
o adioac i i y in ae osol pa icles collec ed a he PG s acks
Radionuclide Mean ac i i y
inc emen
(Bq/m
3
)
Dose
con e sion
ac o (S /Bq)
Volume ic dose
inc emen
(S /m
3
)
238
U 1.3×10
−5
2.9×10
−6
3.9×10
−11
234m
Pa 3.8×10
−10
5.1×10
−15
234
Th 6.6×10
−9
8.8×10
−16
234
U 3.5×10
−6
4.7×10
−11
230
Th 7.4×10
−6
4.3×10
−5
3.2×10
−10
226
Ra 1.1×10
−5
3.5×10
−6
3.8×10
−11
Dose inc emen 0.44 nS /m
3
B ea hed olume 8030 m
3
/a
Occupa ion ac o 0.2
Dose inc emen 0.71 μS /a
Abso p ion a e ype “S”has been assumed o Th and ype “M” o he
o he adionuclides. Radioac i e equilib ium is assumed among
234m
Pa,
234
Th and he pa en
238
U.
34 E. Bo ego e al. / Science o he To al En i onmen 377 (2007) 27–35
Techniques, INTA) o hei kind help h oughou he
sampling campaigns. Addi ional hanks o M . An onio
Padilla o his help and suppo du ing bo h he
sampling and he labo a o y analysis. This wo k has
been suppo ed by he En i onmen Council o he
Andalusia Regional Go e nmen (Conseje ía de Medio
Ambien e de la Jun a de Andalucía).
Re e ences
Adame J. Análisis de ozono opos é ico en la p o incia de Huel a
2005. PhD Thesis, Uni e si y o Huel a (in Spanish).
Azouazi M, Ouahidi Y, Fakhi S, And es Y, Abbe JCh, Benmansou M.
Na u al adioac i i y in phospha es, phosphogypsum and na u al
wa e s in Mo occo. J En i on Radioac 2001;54:231–42.
Be g T, Røyse O, S einnes S. T ace elemen s in a mosphe ic
p ecipi a ion a No wegian backg ound s a ions (1989–1990)
measu ed by ICP-MS. A mos En i on 1994;28:3519–36.
Bolí a JP, Ga cía-Teno io R, Ga cía-León M. Enhancemen o na u al
adioac i i y in soils and sal -ma shes su ounding a non-nuclea
indus ial complex. Sci To al En i on 1995;173–174:125–36.
Bolí a JP, Ga cía-Teno io R, Ga cía-León M. On he ac iona ion o
na u al adioac i i y in he p oduc ion o phospho ic acid by he
we acid me hod. J Radioanal Nucl Chem 1996;214:77–88.
Ca alho FP. O igins and concen a ions o
222
Rn,
210
Pb,
210
Bi and
210
Po in he su ace ai a Lisbon, Po ugal, a he A lan ic Edge o
he Eu opean Con inen al Landmass. A mos En i on 1995;29:
1809–19.
Holm E, Fukai R. Me hod o mul i-elemen alpha-spec ome y o
ac inides and i s applica ion o en i onmen al- adioac i i y s udies.
Talan a 1977;24:659–64.
Ma ínez-Ruiz FJ, Adame JA, Bolí a JP, San Miguel EG, de la Rosa J,
de la Campa AM. A mosphe ic il e measu emen s by gamma- ay
spec ome y wi h a Ge de ec o . Abs ac s o he 3 d Eu opean
geophysics union gene al assembly, ol. 8. Geophysical esea ch
abs ac s; 2006. p. 1247–8.
Mas JL, Boli a JP, San Miguel EG, Ga cia-Teno io R, Aguado JL,
Pe ez JP. E aluacion Dosime ica de Balsas de Fos oyeso
Cubie as pa a su Uso Publico. Abs ac s o : 3 d Ibe ian cong ess
on en i onmen al con amina ion and oxicology. Fa o, Po ugal:
Uni e sidade do Alga e; 2000. [In Spanish].
Mas JL, Bolí a JP, Ga cía-Teno io R, Aguado JL, San Miguel EG,
González J. A dosime ic model o de e mining he e ec i eness
o soil co e s o phosphogypsum was e piles. Heal h Phys
2001;80:34–40.
Mas JL, San Miguel EG, Bolí a JP, Vaca F, Pé ez-Mo eno JP. An
assay on he e ec o p elimina y es o a ion asks applied o a
la ge TENORM was es disposal in he Sou h-Wes o Spain. Sci
To al En i on 2006;364:55–66.
Pé ez-Mo eno JP, Radionúclidos Na u ales en la Indus ia de
Fe ilizan es, PhD.Thesis, Uni e si y o Se ille (in Spanish) 2005.
Que ol X, Alas uey A, de la Rosa J, Sánchez-de-la-Campa A, Plana F,
Ruiz CR. Sou ce appo ionmen analysis o a mosphe ic pa icu-
la es in an indus ialised u ban si e in Sou hwes e n Spain. A mos
En i on 2002;36:3113–25.
UNSCEAR. Repo o he Uni ed Na ions Scien i ic Commi ee on he
e ec s o a omic adia ion. New Yo k: Uni ed Na ions; 2000.
35E. Bo ego e al. / Science o he To al En i onmen 377 (2007) 27–35