Heinz Surbeck's research while affiliated with Eötvös Loránd University and other places

We present an analytical method that allows for the rapid measurement of uranium in water samples. For a 50 ml sample concentrations down to about 2 micro-g/l can be measured within an hour. There are no toxic chemicals used and the whole equipment is portable and can be powered by a 12 V battery. The preparation consists of adding 200 mg silica gel to the 50 ml sample, stirring for 1 hour, filtering out the silica gel and transferring it to a semi-micro cuvette for the measurement. Several samples can be prepared in parallel, depening on the number of magnetic stirrers available. The measurement takes only 1 minute and uses the uranyl fluorescence, enhanced by the adsorption on silica gel. Excitation is done by a pulsed UV-LED at 285 nm. The delayed fluorescence signal around 520 nm is detected by a 6 mm x 6 mm Silicon Photomultiplie (SiPM) behind a 520 nm bandpass filter. Pulsing the LED, converting the SiPM output and displaying the result is controlled by an Arduino microprocessor. All details of the experimental setup as well the software code are presented. It's open source, open to be copied and the whole material costs are only around 500 Euro. Powered by TCPDF (www.tcpdf.org)

Lake Velence is a shallow soda lake whose water level and water quality show a severely deteriorating tendency in recent years. Until recently, the groundwater component in the lake’s water budget has not been taken into consideration. To integrate the lake into the groundwater flow system at the regional scale, methods of “basin hydraulics” were applied. In addition, 17 water samples were collected for δ2H and δ18O, and for ΣU, 226Ra and 222Rn activity measurements to use these parameters as environmental tracers of groundwater contribution. Groundwater mapping revealed that groundwater recharges in Velence Hills and the local elevations south of the lake, whereas discharge occurs by the lake’s shoreline and along surface watercourses. The results indicated that Lake Velence is the discharge point of local groundwater flow systems known to be more sensitive to climate changes and anthropogenic activities (e.g., contamination, overexploitation). Groundwater and lake water have similar uranium activity concentrations serving as another sign of groundwater inflow into the lake. Therefore, it is necessary to consider both the groundwater component in the lake’s water management and its vulnerability regarding local and short-term changes in the catchment area.

Groundwater is an important freshwater resource, which can be affected by geogenic radionuclide contamination. To make decisions regarding the use and management of groundwater, understanding the controls of radionuclide mobility is critical. In the southern foreland of a granitic outcrop in Hungary, high gross alpha activity concentration was measured in drinking water wells, related probably to the presence of uranium. It has been suggested that understanding of the groundwater flow system may be a key aspect to understand uranium mobility in groundwater. The goal of the present work was to elucidate the conceptual model of radionuclide mobility in the study area, focusing in particular on the geochemical controls of uranium. For this purpose, water samples were collected and nuclide-specific measurements for ²²⁶Ra and radon isotopes were carried out, in addition to ²³⁴U+²³⁸U measurements, to increase the range of radionuclides and better understand their mobility. A geochemical modeling analysis involving redox-controlling kinetic reactions and a surface complexation model was developed to support the conceptual model. The results from the sampling indicate that excess of ²³⁴U+²³⁸U (3–753 mBq L⁻¹) contribute to the natural radioactivity measured in drinking water to a large degree. ²²⁶Ra was measured in relatively low activity concentrations (<5–63 mBq L⁻¹) with the exception of three specific wells. Notable radon activity concentration was measured in the springwaters from Velence Hills (1.01–3.14 × 10⁵ mBq L⁻¹) and in interrelation with the highest (285–695 mBq L⁻¹) ²²⁶Ra activity concentrations. The geochemical model suggests that uranium distribution is sensitive to redox changes in the aquifer. Its mobility in groundwater depends on the residence time of groundwater compared to the reaction time controlling the consumption of oxidizing species. The longer the flow path from the recharge point to an observation point where U is measured, the more likely it is that reducing conditions will be found in the aquifer and the elemental concentration U will be low.

Magyarország ivóvízellátásának nagy része felszínalatti vízből származik, melyben előfordulhatnak természetes radionuklidok. Mivel ezek mobilitása erősen függ a geokémiai környezettől, a felszínalatti víz geokémiai paramétereinek ismerete fontos tényező, melyek erősen függnek a felszínalatti víz áramlási rendszereitől. Ezért a hidrogeológiai háttér ismerete elengedhetetlen ezeknek a radionuklidoknak a vizsgálatakor, különösképpen, ha megemelkedett koncentrációban fordulnak elő a felszínalatti vizekben. Kutatásunk során egy partiszűrésű- és karsztos kutakat egyaránt használó vízbázis megemelkedett természetes radioaktivitásának okát vizsgáltuk. Az esetek többségében a területen található felszínalatti vizek összes alfa aktivitása meghaladja a 0,1 Bq/l határértéket. A kutatás célja meghatározni melyik radionuklid felelős a megemelkedett aktivitásért és jelenlétére hidrogeológiai szempontú magyarázatot adni. A kutatás során vett vízminták mindegyikének (U-238+U-234), Ra-226, Rn-222 koncentrációja került meghatározásra. A területen jelen levő megemelkedett urán aktivitás mértéke összefüggésbe hozható a folyó vízszint ingadozásaival, ezáltal a kutatás rávilágít ezen partiszűrésű rendszerek tranziens viselkedésére, melynek figyelembevétele nem elhanyagolható a mintázások és a biztonságos ivóvízellátás kapcsán. A kutatás az Innovációs és Technológiai Minisztérium ÚNKP-19-3 kódszámú Új Nemzeti Kiválóság Programjának szakmai támogatásával készült. In Hungary the drinking water supply is mainly based on groundwater, in which radionuclides are common components. Since the mobility of the most common radionuclides, uranium and radium, is strongly influenced by the geochemical conditions, knowledge on the geochemical parameters of water is required. This depends on the flow system and the flow regime. Therefore, hydrogeology has a crucial role in revealing the origin of elevated activity concentrations. This research presents a case study in Hungary where the drinking water supply is provided by bank filtered and karst wells. In most of the wells of the research area the gross alpha values are above the limit, 0.1 Bq L-1. The aim of this study is to determine which radionuclides may cause the elevated radioactivity and explain their occurrence using the hydrogeological approach. All samples of the study were analysed for (U-238+U-234), Ra-226, Rn-222. The study revealed the correlation between the river water level fluctuation and the uranium content of the wells. The results of this study highlighted the transient nature of river bank filtered systems, which should be taken into account in the monitoring and water supply strategy. Supported by the ÚNKP-19-3 New National Excellence Program of the Ministry for Innovation and Technology.