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Title:Radioactive isotopes in ground waters of Slovenia
Authors:Kovačič, Katarina (Author)
Lipoglavšek, Matej (Mentor) More about this mentor... New window
Kožar Logar, Jasmina (Mentor) More about this mentor... New window
Files:.pdf Katarina_Kovacic.pdf (8,62 MB)
 
Language:English
Work type:Dissertation (m)
Tipology:2.08 - Doctoral Dissertation
Organization:FPŠ - Graduate School
Abstract:Within the duration of three projects (J7-0363, L1-0437, L1-4280), in the period from 2008 to 2013, measurements of tritium (3H), 40K and γ-ray emitters of uranium (238U, 226Ra and 210Pb) and thorium (228Ra and 228Th) decay series in groundwaters of Slovenia were carried out. Tritium was also measured in precipitation at selected locations. Groundwater sampling sites were selected in order to cover the most representative lithological units that are found in Slovenia and were at the same time evenly distributed throughout the country. In total, 281 samples were measured from 120 different locations. Measurements in the period 2009-2013 have shown that tritium concentrations in precipitation in Ljubljana are for about 30% lower compared to those in Vienna, however they are in line with seasonal fluctuations observed in Vienna. This was an important information in the process of the reconstruction of past tritium concentrations in precipitation in Ljubljana (tritium curve) for the missing period between 1953 and 1981. Tritium curve represents the input data when determining the average age of water. In determining the influence of various parameters on the final interpretation of the groundwater age it has been found that the greatest uncertainty contribute the measurements of the tritium curve and the measurements of tritium in groundwater samples. Also, the interaction of other factors (continental effect, rainfall regime, infiltration) and the lack of knowledge of them may have a major impact on the misinterpretation of groundwater age. Based on tritium concentration, groundwaters were divided into 4 major categories, into groundwaters that are older than 100 years (tritium concentration was below the detection limit), groundwaters, where the older component prevails (concentration of tritium was between 0 and 2.5 TU), groundwaters with the age between 30 and 60 years (the concentration of tritium was on average 8 TU) and recent groundwaters with age up to 15 years (tritium concentration of about 6 TU). The natural background of γ-ray emitters was determined for each lithological unit. The most represented radionuclide was 40K with concentrations always above the detection limit. A dependency of 40K concentrations on nitrate was observed, especially in the recharge areas, where limestone prevailed. Other γ-ray emitters revealed some dependence on nitrate concentration, especially both radium isotopes (226Ra and 228Ra). The concentration of 210Pb in groundwaters is mainly due to the connection with the surface and consequently with atmospheric 210Pb. The highest concentrations of 238U and 228Ra were measured in groundwaters from recharge areas in clastic rocks with a clay component. In contrast to the expected, concentrations for all γ-ray emitters (except 210Pb) were the lowest or even not detectable, in groundwaters from recharge areas in igneous and metamorphic rocks. Among γ-ray emitters and categorization based on tritium concentrations, elevated concentrations of 238U were observed in groundwaters with prevailing older component. Elevated concentrations of 40K were also observed in them. The largest scattering of 210Pb and 40K concentrations was observed in recent waters, which indicates a connection with the surface and application of fertilizers.
Keywords:Groundwaters, Slovenia, tritium input curve, natural gamma-ray emitters background.
Year of publishing:2015
Source:Nova Gorica
COBISS_ID:4048891  Link is opened in a new window
URN:URN:SI:UNG:REP:TPYZ5FAC
Views:4250
Downloads:142
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Secondary language

Language:Slovenian
Title:Radioaktivni izotopi v podzemnih vodah Slovenije
Abstract:Meritve tritija v padavinah so pokazale, da je koncentracija tritija v Ljubljani za okoli 30 % nižja ter da je v skladu s sezonskim nihanjem, opaženim na Dunaju. To je bil pomemben podatek pri rekonstrukciji preteklih koncentracij tritija (tritijeva krivulja) za manjkajoče obdobje med letoma 1953 in 1981 v ljubljanskih padavinah. Tritijeva krivulja predstavlja vhodne podatke pri določevanju povprečne starosti vod. Pri določanju vpliva različnih parametrov na končno interpretacijo starosti vode smo ugotovili, da doprineseta največ k negotovosti starosti sama negotovost tritijeve krivulje, t.j. negotovost meritev v padavinah in negotovost meritev tritija v vzorcih podzemnih vod. Tudi medsebojno delovanje drugih faktorjev (kontinentalni efekt, padavinski režim, infiltracija) in nepoznavanje le-teh ima lahko velik vpliv na napačno interpretacijo starosti. Na podlagi koncentracije tritija smo podzemne vode razdelili na 4 večje skupine, in sicer na podzemne vode, ki so starejše od 100 let (koncentracija tritija je bila pod detekcijsko mejo), na podzemne vode, kjer gre verjetno za prevlado starejše komponente (koncentracija tritija je bila med 0 in 2,5 TU), na podzemne vode, ki imajo starost med 30 in 60 let (koncentracija tritija je bila povprečno nad 8 TU) in recentne podzemne vode s starostjo do okoli 15 let (koncentracija tritija okoli 6 TU). Za posamezne litološke enote smo določili naravno ozadje sevalcev žarkov gama. Najbolj zastopan sevalec žarkov gama je bil 40K, katerega koncentracije so bile vedno nad detekcijsko mejo. Opažena je bila odvisnost koncentracije 40K od vsebnosti nitratov, še posebej v zaledjih, kjer prevladujejo apnenci. Tudi pri ostalih sevalcih žarkov gama se je ponekod pokazala odvisnost od nitratov, še posebej pri obeh radijih (226Ra in 228Ra). Vsebnost 210Pb v podzemnih vodah kaže predvsem na povezavo le-teh s površjem in posledično s 210Pb, ki nastaja v atmosferi. Najvišje koncentracije 238U in 228Ra so bile izmerjene v podzemnih vodah, kjer so v zaledju prevladovali klastiti z glineno komponento. V nasprotju s pričakovanim, so bile najnižje koncentracije vseh sevalcev žarkov gama (z izjemo 210Pb) zaznane v podzemnih vodah, kjer so v zaledju prevladovale magmatske in metamorfne kamnine. Med sevalci žarkov gama in kategorizacijo podzemnih vod na podlagi vsebnosti tritija smo opazili povišano koncentracijo 238U v podzemnih vodah s prevladujočo starejšo komponento. Le-te so imele tudi povišane koncentracije 40K. Največji raztros koncentracij 210Pb in 40K je bil opažen pri recentnih vodah, kar nakazuje na stik s površino in vnos gnojil.
Keywords:Podzemne vode, Slovenija, tritijeva krivulja, naravna ozadja sevalcev žarkov gama.


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