Janko Urbanc

The isotope altitude effect reflected in groundwater: a case study from Slovenia

This paper presents the stable isotope data of oxygen (δ18O) and hydrogen (δ2H) in groundwater from 83 sampling locations in Slovenia and their interpretation. The isotopic composition of water was monitored over 3 years (2009–2011), and each location was sampled twice. New findings on the isotopic composition of sampled groundwater are presented, and the data are also compared to past studies regarding the isotopic composition of precipitation, surface water, and groundwater in Slovenia. This study comprises: (1) the general characteristics of the isotopic composition of oxygen and hydrogen in groundwater in Slovenia, (2) the spatial distribution of oxygen isotope composition (δ18O) and d-excess in groundwater, (3) the groundwater isotope altitude effect, (4) the correlation between groundwater d-excess and the recharge area altitude of the sampling location, (5) the relation between hydrogen and oxygen isotopes in groundwater in comparison to the global precipitation isotope data, (6) the groundwater isotope effect of distance from the sea, and (7) the estimated relation between the mean temperature of recharge area and δ18O in groundwater.

Carbonate Chemistry and Isotope Characteristics of Groundwater of Ljubljansko Polje and Ljubljansko Barje Aquifers in Slovenia

Ljubljansko polje and Ljubljansko Barje aquifers are the main groundwater resources for the needs of Ljubljana, the capital of Slovenia. Carbonate chemistry and isotope analysis of the groundwater were performed to acquire new hydrogeological data, which should serve as a base for improvement of hydrogeological conceptual models of both aquifers. A total of 138 groundwater samples were collected at 69 sampling locations from both aquifers. Major carbonate ions and the stable isotope of oxygen were used to identify differences in the recharging areas of aquifers. Four groups of groundwater were identified: (1) Ljubljansko polje aquifer, with higher Ca2+values, as limestone predominates in its recharge area, (2) northern part of Ljubljansko Barje aquifer, with prevailing dolomite in its recharge area, (3) central part of Ljubljansko Barje aquifer, which lies below surface cover of impermeable clay and is poor in carbonate, and (4) Brest and Iški vršaj aquifer in the southern part of Ljubljansko Barje with higher Mg2+ in groundwater and dolomite prevailing in its recharge area. The radioactive isotope tritium was also used to estimate the age of groundwater. Sampled groundwater is recent with tritium activity between 4 and 8 TU and residence time of up to 10 years.

Development of a Protocol for the Karst Water Source Protection Zoning: Application to the Classical Karst Region (NE Italy and SW Slovenia)

Although karst aquifers are highly vulnerable and represent an important water resource, they are often inadequately protected. Furthermore, national water resource protection policies lack precision regarding the criteria for delimitation of source protection zones in karst. Usually either vulnerability assessment or travel time is considered. The proposed integrated protocol considers both. It is specifically designed for large karst aquifers where i) an additional distinction between areas of different liability to contamination within the aquifer, and ii) a certain generalisation of protection classes should be made for practical reasons. The protocol includes a detailed description of the separate steps of the protection zoning procedure. Information obtained from both artificial and natural tracers is used to account for the variability of groundwater flow under different hydrologic conditions. Analysis of groundwater physico-chemical parameters time series is better employed under high flow regimes and analysis of artificial tracers breakthrough curves under low flow conditions. Source protection zones are divided into three levels of protection, which should be further generalised, validated and adjusted to land use plans. The protocol has been applied to the Classical Karst Region transboundary aquifer (NE Italy and SW Slovenia). The results enable a uniform delineation of protection zones encompassing water sources that have not been protected to date, and improve the understanding and management of transboundary aquifers. The proposed protocol can be used in other karst aquifers, and adjusted to national protection legislation and spatial planning frameworks.

Intrinsic vulnerability of the Isonzo/Soča high plain aquifer (NE Italy – W Slovenia)

ABSTRACT The paper presents the map of intrinsic groundwater vulnerability of the Isonzo/Soča High Plain, which is located between the Collio Hills and the Classical Karst Region and holds an aquifer shared between Italy and Slovenia. The map, produced at a scale of 1:25,000 and printed in A0 format, was obtained by means of the SINTACS method and shows the intrinsic vulnerability of the aquifer in terms of seven vulnerability classes, from extremely high to low. It is accompanied by four supplementary sketches that illustrate the geological framework, the bedrock top surface, the groundwater flow paths, the Hazard Index map and three diagrams that summarize the percentages of vulnerability classes and of Hazard Index classes of the study area.

Comparison of prediction methods for oxygen-18 isotope composition in shallow groundwater

Groundwater is the most important source of drinking water in the world. Therefore, information on the quality and quantity is important, as is new information related to the characteristics of the aquifer and the recharge area. In the present study we focused on the isotope composition of oxygen (δ18O) in groundwater, which is a natural tracer and provides a better understanding of the water cycle, in terms of origin, dynamics and interaction. The groundwater δ18O at 83 locations over the entire Slovenian territory was studied. Each location was sampled twice during the period 2009-2011. Geostatistical tools (such us ordinary kriging, simple and multiple linear regressions, and artificial neural networks were used and compared to select the best tool. Measured values of δ18O in the groundwater were used as the dependent variable, while the spatial characteristics of the territory (elevation, distance from the sea and average annual precipitation) were used as independent variables. Based on validation data sets, the artificial neural network model proved to be the most suitable method for predicting δ18O in the groundwater, since it produced the smallest deviations from the real/measured values in groundwater.

Mercury in the unconfined aquifer of the Isonzo/Soca River alluvial plain downstream from the Idrija mining area

This work aims at evaluating mercury (Hg) occurrence, spatial distribution and speciation in groundwater of the Isonzo/Soča River upper alluvial plain downstream from the Idrija Hg mine (Western Slovenia). Several wells and piezometers were sampled both in static and dynamic mode. Total (THg) and filtered (FHg) concentrations were generally higher in static (THg, 1.87-855 ng L-1; FHg, 0.20-13.61 ng L-1) than in dynamic mode (THg, 0.08-78.77 ng L-1; FHg, 0.28-6.65 ng L-1). The estimated background value accounts for 2-3 ng L-1. On the basis of hydrochemistry and isotopic composition, the main sources of groundwater were established. Hg concentrations in the Slovenian sector, supplied by local rainfall, are comparable to values measured close to the Isonzo River. Possible further Hg local sources have been suggested. Stability field analysis for the aqueous Hg species revealed that in the presence of chloride Hg solubility may be increased by the formation of chlorocomplexes. Mercury that rarely enters reduced surrounding conditions can be bound to sulphur to form polysulphide species depending on the pH of water. Since Hg-contaminated alluvial sediments of the Isonzo River may act as a secondary Hg source in groundwater, a borehole was dug down to the water table. Mercury content and speciation revealed that cinnabar (HgS) is the prevalent form followed by the matrix-bound Hg (Hgbound). Variations of the physico-chemical boundary conditions, as well as the raising/lowering of the water table, may be locally responsible for the slight variability of Hg concentrations in the aquifer.

Geological evaluation of the Slovenian territory for radioactive waste disposal

Due to the growing need for a final disposal of low and intermediate level (LILW) radioactive waste, the final solution for the short-lived LILW is one of the key issue of radioactive waste management in Slovenia at the moment. In the Area Survey Stage of the site selection process for the final disposal the suitability of the Slovenian territory for a surface or underground repository of LILW is examined by cabinet investigations in order to locate geologically suitable formations. The assessment of natural conditions of the system was based on consideration of the main geological, hydro-geological and seismotectonic conditions. It was performed with ARC/INFO technology. The results are compiled in a map, showing potential areas for underground and surface disposal of LILW in Slovenia. It has been established that there is a potential suitability for both surface and underground disposal on about 10,000 km2 of the Slovenian territory, which represents almost half of the entire Slovenian territory. doi:10.5475/geologija.2002.072 600 Janko Urbanc, Jasna Šinigoj & Peter Tom{e strokovno pripravljene smernice, izdelane na osnovi mednarodnih priporo~il ter z upo{tevanjem lokalnih specifi~nosti. Najpomembnej{a tehni~na priporo~ila oziroma smernice se nana{ajo na zagotavljanje dolgoro~ne varnosti odlagali{~a. Postopek analize in vrednotenja prostora glede na primernost za odlaganje NSRAO torej ustreza predvsem tehnolo{kim in prostorsko funkcionalnim merilom oziroma tehni~nim vidikom lokacije za odlagali{~e NSRAO. V za~etni stopnji stopnji lokacij odlagali{~a izvedemo kabinetni pregled ozemlja na osnovi obstoje~ih podatkov. V ta namen je potrebno pridobiti ustrezne prostorske podatke, jih primerno obdelati, zagotoviti njihovo kakovost in medsebojno zdru‘ljivost ter nato po posameznih parametrih izbora ovrednotiti prostor. Tu gre predvsem za ra~unalni{ko podprte zbirke prostorskih podatkov, pri samem vrednotenju prostora pa si pomagamo z ve~parametrskimi odlo~itvenimi metodami. Agencija ARAO je leta 1999 za~ela zbirati in obdelovati vse potrebne digitalizirane prostorske podatke. Ko so bili ti obdelani do take mere, da je bila zagotovljena njihova usklajenost in zdru‘ljivost, se je pri~elo z vrednotenjem slovenskega ozemlja, katerega cilj je bil prikaz potencialno primernih obmo~ij za odlaganje NSRAO v Sloveniji. Znotraj teh bi nato v sodelovanju z lokalnimi skupnostmi in podrobnej{imi raziskavami izbranih obmo~ij pri{li do kon~ne lokacije za odlagali{~e NSRAO. Vloga geologije v postopku vrednotenja prostora za odlagali{~e NSRAO Osnovni princip odlaganja radioaktivnih odpadkov (RAO) je poiskati stabilna in slabo prepustna geolo{ka okolja, kjer naravni procesi, ki lahko vplivajo na radioaktivne odpadke, potekajo ~im bolj upo~asnjeno. Koncept odlaganja RAO temelji na vzpostavitvi ve~ zaporednih pregrad, ki upo~asnijo ali onemogo~ajo migracijo radionuklidov v okolju, kjer so odpadki odlo‘eni. Geolo{ko okolje, v katerem je zgrajeno odlagali{~e, predstavlja zadnjo pregrado tega koncepta, saj omogo~a dolgoro~no izolacijo odpadkov od biosfere oziroma od ljudi in okolja. Geolo{ki dejavniki, ki karakterizirajo neko lokacijo odlagali{~a, so torej v neposredni zvezi z dolgoro~no varnostjo odlagali{~a saj: • zagotavljajo fizi~no za{~ito odlagali{~a pred naravnimi (npr. erozija, tektonika) in antropogenimi vplivi, • omejujejo prehod radioaktivnih izotopov iz odlagali{~a in njegove bli‘nje okolice, • zadr‘ujejo radionuklide v geolo{kem okolju v {ir{i okolici odlagali{~a (kamnini, ki ga obdaja). Vsako na~rtovanje odlagali{~a radioaktivnih odpadkov mora zato vsebovati obse‘ne geolo{ke raziskave za zagotovitev zadostnega razumevanja lastnosti geolo{kega okolja, primernega za odlaganje RAO. Skladno z mednarodnimi priporo~ili (IAEA, 1994) obstaja konsenz o vlogi in pomenu posameznih geolo{kih dejavnikov pri zagotavljanju dolgoro~ne varnosti odlagali{~a RAO. V splo{nem lahko kot zelo pomemben dejavnik navedemo stopnjo kompleksnosti geolo{kega okolja. Relativno preprosto in predvidljivo geolo{ko okolje je ‘eleni pogoj za izvedbo varnostne ocene odlagali{~a, prav tako je tak{no lokacijo la‘je karakterizirati. Vsak geolo{ki dejavnik, za katerega lahko smatramo, da pove~uje kompleksnost geolo{kega okolja na~eloma zmanj{uje oceno primernosti posamezne lokacije ( S a v a g e , 1995). Pri dolo~itvi vloge in na~ina upo{tevanja posameznih geolo{kih dejavnikov je pomembno, da jim ne pripi{emo prevelike vloge glede na vrsto odpadkov, katerih odlo‘itev na~rtujemo. V za~etnih fazah postopka izbora lokacij mora biti pozornost osredoto~ena na geolo{ka okolja, ki po pri~akovanjih nudijo ve~ji potencial za odlaganje NSRAO. Šele v kasnej{ih stopnjah je cilj izbrati lokacijo, ki bo skupaj svojimi zna~ilnostmi, primerno zasnovo odlagali{~a in in‘enirskimi pregradami izpolnjevala s strani upravnega organa postavljene zahteve glede varstva pred sevanji. Na osnovi izku{enj ( P e t k o v { e k et al., 1996) se je pokazalo, da je pomembno, da v za~etnih stopnjah ne uporabljamo nikakr{nih izklju~itvenih kriterijev. Va‘no je zasnovati postopek, ki ostaja fleksibilen in temelji na smernicah in priporo~ilih, ki niso preskriptivne narave. V primerjavi z neuspe{nim postopkom izbora lokacije v letih 1990 – 93, ne i{~emo ve~ »geolo{ko najbolj{e« lokacije, ampak geolo{ka okolja, ki so za odlaganje bolj primerna. Odlo~itev o morebitni izklju~itvi nekega obmo~ja ali lokacije lahko temelji samo na neposrednem ali poVrednotenje ozemlja Slovenije za odlaganje radioaktivnih odpadkov z vidika geologije 601 srednem dokazu neprimernosti, pridobljenem med izvr{enimi terenskimi raziskavami v naslednjih na~rtovanih stopnjah postopka. Ne uporabljamo torej strogih izlo~itvenih kvalitativnih kriterijev, ampak opisna priporo~ila, ki dajejo postopku nujno fleksibilnost. Rezultati so eno izmed izhodi{~ za postopek izbora lokacije za odlagali{~e NSRAO, ki naj bi se zaklju~il s potrditvijo lokacije. Kljub temu, da je za dokon~no ovrednotenje prostora potrebno obravnavati {e {tevilne druge prostorske sestavine ter dodatne vidike (ranljivost), pa gre v tej fazi vendarle za klju~ni del vrednotenja (Urbanisti~ni in{titut, 2000) in sicer iz ve~ razlogov: • Obravnavan je tisti del (naravne danosti – geologija,vode, seizmika) prostora, ki je pri izboru lokacije klju~en za zagotavljanje funkcionalnosti in varnosti odlagali{~a in ga tako obravnavajo tudi mednarodne smernice za izbor lokacij odlagali{~ RAO • Gre za merila, ki imajo vlogo v ve~ vidikih vrednotenja: po eni strani so klju~na za opredelitev privla~nosti za investicijo – kolikor ugodnej{e so naravne razmere, toliko enostavnej{a in cenej{a je izgradnja odlagali{~a. Ta merila so v primeru odlagali{~a NSRAO povezana z izolacijskimi lastnostmi geolo{ke pregrade in so torej tudi v neposredni povezavi z varnostjo odlagali{~a. Za ovrednotenje primernosti prostora z vidika geologije za odlaganje NSRAO so bila upo{tevana priporo~ila navedena v Tabeli 1 ( P e t k o v { e k et al., 1995, V e s e l i ~ , 1995, U r b a n c et al., 1998). Metoda vrednotenja in na~in izdelave karte Prostor celotne Slovenije je bil obdelan v GIS okolju z uporabo ve~parametrske metode ute‘ene vsote ( N i j k a m p et al., 1990). Metoda ima dve izraziti prednosti zaradi katerih smo se odlo~ili, da jo uporabimo: • je enostavna, kar je ugodno za razumevanje postopka izbora, saj bodo vanj vklju~ene razli~ne skupine ljudi z razli~no stopnjo znanja, in • omogo~a dober pregled vpliva posameznega parametra na kon~ni rezultat. Pri mnogih tovrstnih metodah zaradi bolj kompliciranega postopka namre~ ni mogo~e videti, na kak{en na~in se bo vrednost dolo~enega parametra odra‘ala v kon~ni oceni koristTabela 1: Upo{tevana priporo~ila pri vrednotenju prostora za odlaganje NSRAO z vidika geologije Parameter / Osnova za upo{tevanje Na~in upo{tevanja Priporo~ilo Prostornina Ve~ja prostornina / Posredno – oddaljenost geolo{ke pregrade ve~ja u~inkovitost od najbli‘je geolo{ke meje geolo{ke pregrade Enostavnost Sorazmerno preprosta Gostota strukturnih elementov / km2 geolo{ke zgradbe in predvidljiva Vrsta kamnine Litolo{ke zna~ilnosti, Dolo~itev primernosti za odlaganje ki prepre~ujejo migracijo vsem litolo{kim ~lenom radionuklidov litostratigrafske karte Geokemi~ne Stabilnost geokemi~ne pregrade Posredno iz litolo{ke karte – zna~ilnosti / minimiziranje reakcij z odpadki primernost glinastih geolo{ke pregrade in kristalinskih kamnin Podzemna voda Ugodne hidravli~ne zna~ilnosti / Geolo{ke strukture z manj{o majhna izdatnost podzemne vode prepustnostjo, izdatnostjo Seizmi~na aktivnost Izven obmo~ij pri~akovane Projektni pospe{ek tal ve~je seizmi~ne aktivnosti. za povratno dobo 475 let. Tektonske zna~ilnosti Izven obmo~ij pri~akovane ve~je Linije glavnih tektonske aktivnosti. regionalnih prelomov. Stabilnost terena Izven nestabilnih obmo~ij Trdnost kamnin (podzemno odlaganje) (povr{insko odlaganje) Obmo~ja plazenja, nagib pobo~ij (povr{insko odlaganje) Poplave in erozija Izven obmo~ij erozije, poplav Vodotoki, poplavna obmo~ja, stopnja erozije. Morfologija Primernej{i teren za izgradnjo Digitalni model reliefa odlagali{~a (povr{insko odlaganje) 602 Janko Urbanc, Jasna Šinigoj & Peter Tom{e nosti posamezne variante, kar pove~a mo‘nost napa~ne presoje posameznih parametrov v odlo~itvenem postopku. Pri uporabi metode ute‘ene vsote moramo vsakemu parametru dolo~iti najprej stopnjo primernosti (koristnosti), poleg tega pa moramo dolo~iti tudi relativni pomen dolo~enega parametra glede na ostale parametre, ki nastopajo v procesu izbora. Odlo~ili smo se, da poleg {tevil~nih ocen uporabimo tudi opisno lestvico ocen primernosti posameznega parametra, saj so opisne ocene v na~elu primernej{e za ocenjevanje ( R a j k o v i ~ , 1987). Uporabili smo slede~o lestvico ocen primernosti: 5 – zelo primerno, 4 – primerno, 3 – srednje primerno, 2 – manj primerno, 1 – zelo nizka stopnja primernosti, 0 – izjemoma primerno V tabeli 2 je prikazan na~in ocenjevanja primernosti za parameter seizmi~na aktivnost. Oceno prim