Lead-210 in the atmospheric air of North and South Estonia: long-term monitoring and back-trajectory calculations/[sup.210]Pb Pohja- ja Louna-Eesti atmosfaariohus: pikaajaline seire ning paritolu hindamine

• Published in: Proceedings of the Estonian Academy of Sciences p. 442
• Main Authors: Isakar, Kadri, Kiisk, Madis, Realo, Enn, Suursoo, Siiri
• Format: Journal Article
• Language: English
• Published: Estonian Academy Publishers 01.12.2016
• Subjects: Analysis; Ionizing radiation; Planetary boundary layer; Precipitation (Meteorology); Estonia
• ISSN: 1736-6046
• DOI: 10.3176/proc.2016.4.11

As the first study of long-term atmospheric [sup.210]Pb in Estonia, the activity concentration and possible origins of the nuclide were monitored at Toravere, South Estonia, and Narva-Joesuu, North- East Estonia, from 2001 to 2008. Activities of [sup.210]Pb in weekly collected air filter samples were analysed using HPGe gamma spectrometry. Results show high weekly, seasonal, and yearly variability in the range from 0.12 mBq [m.sup.-3] to 2.76 mBq [m.sup.-3] (median 0.45 mBq [m.sup.-3]) for Toravere and from 0.08 mBq [m.sup.-3] to 2.53 mB [m.sup.-3] (median 0.43 mBq [m.sup.-3]) for Narva-Joesuu. No significant correlation between the [sup.210]Pb activity concentration and meteorological data was found as far as total weekly precipitation, relative humidity, or air temperature were considered. A strong correlation between the [sup.210]Pb concentrations from the two sampling sites was present. Back-trajectory calculations made with the METEX software showed clearly that high [sup.210]Pb values in surface air were prevailingly caused by continental air masses from the Eurasian continent, while the low activity concentrations tended to arrive via marine air masses from the North Atlantic. Indications of correlation of atmospheric boundary layer height with [sup.210]Pb activity concentration were found. Key words: Pb-210, back-trajectory calculations, atmospheric air, environmental radioactivity, coast area environment, METEX. On kajastatud esmakordselt pikaajalise atmosfaarse [sup.210]Pb seire tulemusi koos [sup.210]Pb paritolu hinnanguga. [sup.210]Pb proove koguti filterseadmete abil Louna-Eestis Toraveres ja Pohja- Eestis Narva-Joesuus aastail 2001-2008. Iga kogumistsukkel kestis nadala ja filtri hilisemal gammaspektromeetrilisel analuusil maarati nadala kumulatiivne [sup.210]Pb aktiivsuskontsentratsioon. [sup.210]Pb kontsentratsioonid varieerusid nadalate, aastaaegade ja aastate loikes markimisvaarselt: 0,12 mBq [m.sup.-3] kuni 2,76 mBq [m.sup.-3] Toraveres (mediaan 0,45 mBq [m.sup.-3]) ning 0,08 mBq [m.sup.-3] kuni 2,53 mB [m.sup.-3] NarvaJoesuus (mediaan 0,43 mBq [m.sup.-3]). Korgemad vaartused ja suurem varieeruvus ilmnesid talviti, madalad aktiivsuskontsentratsioonid ning nende vaiksem varieeruvus iseloomustasid suveperioode. Tarkvarapaketi METEX abil hinnati korge ja madala [sup.210]Pb kontsentratsiooniga ohupakettide paritolu. Nn tagasitrajektooride (back-trajectories) arvutused naitasid, et suure [sup.210]Pb kontsentratsiooniga ohk saabub nii Narva-Joesuusse kui ka Toraverre kontinentaalsete ohumassidega Euraasiast, samas kui madala [sup.210]Pb kontsentratsiooniga ohk on merelist paritolu, saabudes meile PohjaAtlandilt. Korrelatsiooni ilmastikunahtuste (temperatuur, suhteline ohuniiskus, sademed) ja [sup.210]Pb kontsentratsiooni vahel ei leitud. Kull aga tuvastati nork korrelatsioon [sup.210]Pb kontsentratsiooni ja atmosfaarse piirkihi korguse vahel. Viimane nouab autorite hinnangul veel edasisi uuringuid. Toraveres ja Narva-Joesuus moodetud [sup.210]Pb kontsentratsioonide vahel leiti vaga tugev positiivne korrelatsioon. Sellest jareldavad autorid, et kaugemat paritolu ohumasside moju [sup.210]Pb kontsentratsioonile on suurem kui lokaalsete allikate, sh toostus, oma.