Dieter Rank

Deuterium excess in precipitation of Alpine regions – moisture recycling

The paper evaluates long-term seasonal variations of the deuterium excess (d-excess = δ2H − 8… δ18O) in precipitation of stations located north and south of the main ridge of the Austrian Alps. It demonstrates that sub-cloud evaporation during precipitation and continental moisture recycling are local, respectively, regional processes controlling these variations. In general, sub-cloud evaporation decreases and moisture recycling increases the d-excess. Therefore, evaluation of d-excess variations in terms of moisture recycling, the main aim of this paper, includes determination of the effect of sub-cloud evaporation. Since sub-cloud evaporation is governed by saturation deficit and distance between cloud base and the ground, its effect on the d-excess is expected to be lower at mountain than at lowland/valley stations. To determine quantitatively this difference, we examined long-term seasonal d-excess variations measured at three selected mountain and adjoining valley stations. The altitude differences between mountain and valley stations ranged from 470 to 1665 m. Adapting the ‘falling water drop’ model by Stewart [J. Geophys. Res., 80(9), 1133–1146 (1975).], we estimated that the long-term average of sub-cloud evaporation at the selected mountain stations (altitudes between about 1600 and 2250 m.a.s.l.) is less than 1 % of the precipitation and causes a decrease of the d-excess of less than 2 ‰. For the selected valley stations, the corresponding evaporated fraction is at maximum 7 % and the difference in d-excess ranges up to 8 ‰. The estimated d-excess differences have been used to correct the measured long-term d-excess values at the selected stations. Finally, the corresponding fraction of water vapour has been estimated that recycled by evaporation of surface water including soil water from the ground. For the two mountain stations Patscherkofel and Feuerkogel, which are located north of the main ridge of the Alps, the maximum seasonal change of the corrected d-excess (July/August) has been estimated to be between 5 and 6 ‰, and the corresponding recycled fraction between 2.5–3 % of the local precipitation. It has been found that the estimated recycled fractions are in good agreement with values derived from other approaches.

Isotope studies in large river basins: A new global research focus

Rivers are an important linkage in the global hydrological cycle, returning about 35%of continental precipitation to the oceans. Rivers are also the most important source of water for human use. Much of the worlds population lives along large rivers, relying on them for trade, transportation, industry, agriculture, and domestic water supplies. The resulting pressure has led to the extreme regulation of some river systems, and often a degradation of water quantity and quality For sustainable management of water supply agriculture, flood-drought cycles, and ecosystem and human health, there is a basic need for improving the scientific understanding of water cycling processes in river basins, and the ability to detect and predict impacts of climate change and water resources development.

Analysis of isotopic signals in the Danube River water at Tulln, Austria, based on daily grab samples in 2012

Results of stable isotope measurements (δ2H, δ18O) of daily grab samples, taken from the Danube River at Tulln (river km 1963) during 2012, show seasonal and short-term variations depending on the climatic/hydrological conditions and changes in the catchment area (temperature changes, heavy rains and snow melt processes). Isotope ratios in river water clearly reflect the isotopic composition of precipitation water in the catchment area since evaporation influences play a minor role. Average δ2H and δ18O values in 2012 are−78‰ and−11.0‰, respectively, deuterium excess averages 10‰. The entire variation amounts to 1.8‰ in δ18O and 15‰ in δ2H. Quick changes of the isotopic composition within a few days emphasise the necessity of daily sampling for the investigation of hydrological events, while monthly grab sampling seems sufficient for the investigation of long-term hydro-climatic trends. 3H results show peaks (half-width 1–2 days, up to about 150 TU) exceeding the regional environmental level of about 9 TU, probably due to releases from nuclear power plants.

Hydrological and Biogeochemical Characterization of the Danube River System Using Isotopes

Meeting Danube Basin monitoring and management objectives such as those implied by the EU Water Framework Directive requires a comprehensive understanding about the hydrological and biogeochemical functioning of not only the river system but also the connections between groundwater and surface water across the basin. While hydraulic and geochemical measurements can provide some of this understanding, it is often difficult to obtain knowledge about some of the more critical aspects of basin functioning or it can take decades of intensive monitoring before adequate interpretations can be made. Isotope hydrology approaches can often provide critical insights on surface water/groundwater interactions and biogeochemical cycling with only moderate effort and cost. Such information can help clarify local behaviors as well as overall basin responses. Approaches using “environmental” stable and radioactive isotopes (i.e., isotopes that are already in the environment and not intentionally applied) have been used to understand sources and losses of water in the Danube, the importance of groundwater discharge, basin residence times, tributary mixing, and nitrate cycling using isotope methods. We review existing studies as well as present new isotope data that reveal important spatial and temporal dynamics occurring in the Danube River, tributaries, and across the basin.

Isotope Evidence to Link a Suspect with a Pipe Bomb Multimurder in Austria 1995

Abstract:  A bomb attempt in Oberwart, Austria, on February 4, 1995, was the culmination of several pipe and letter bomb attempts mainly in Austria. The pipe bomb had been mounted on a self‐made gypsum (plaster of Paris) pedestal and exploded when touched, killing four persons. With a level of 200 tritium units (TU), the water extracted from the gypsum pedestal was unusually enriched in tritium (3H) compared to an environmental level of about 20 TU at that time. Investigation of the 3H content of air moisture in the living room of an arrested suspect showed values of about 1000 TU (normally, 50 TU is not exceeded). Additionally, water used as sealing liquid in a glass with nitroglycerine found in the living room was also significantly enriched in 3H (>400 TU). The living room therefore offered the high 3H level environment necessary to lead to elevated 3H concentrations in the gypsum pedestal.

Temporal and spatial distribution of isotopes in river water in Central Europe: 50 years experience with the Austrian network of isotopes in rivers

ABSTRACT The Austrian network of isotopes in rivers comprises about 15 sampling locations and has been operated since 1976. The Danube isotope time series goes back to 1963. The isotopic composition of river water in Central Europe is mainly governed by the isotopic composition of precipitation in the catchment area; evaporation effects play only a minor role. Short-term and long-term isotope signals in precipitation are thus transmitted through the whole catchment. The influence of climatic changes has become observable in the long-term stable isotope time series of precipitation and surface waters. Environmental 3H values were around 8 TU in 2015, short-term 3H pulses up to about 80 TU in the rivers Danube and March were a consequence of releases from nuclear power plants. The complete isotope data series of this network will be included in the Global Network of Isotopes in Rivers database of the International Atomic Energy Agency (IAEA) in 2017. This article comprises a review of 50 years isotope monitoring on rivers and is also intended to provide base information on the (isotope-)hydrological conditions in Central Europe specifically for the end-users of these data, e.g. for modelling hydrological processes. Furthermore, this paper includes the 2006–2015 supplement adding to the Danube isotope set published earlier.