H. Moser

Dispersivity and velocity relationship from laboratory and field experiments

Abstract Laboratory test results on longitudinal dispersion of soluble material in loose rocks with artificially composed or natural grain-size distributions are compared with one another and with results of field tests. In this way it can be demonstrated that it is quite possible to translate laboratory results to field conditions, if sedimentological properties of the loose materials are comparable, if bedding (geological interfaces) runs parallel to the flow direction and is hydraulically ineffective, and if distances between injection and detection are about less than 50 m. Transverse dispersion is difficult to determine. At first approximation the width of tracer cloud from a line injection was determined and the aperture angle of the resultant cloud calculated. The laboratory and field experiments showed an aperture angle of about 5° on distances between 10 and 2500 m.

Isotope hydrology investigations in large refuse lysimeters

With the aim of studying the hydraulic behaviour and isotopic effects in refuse dumps, measurements of the 18O and 2H content of rainwater infiltrating into large cylindrical refuse lysimeters (1.5–4 m height with diameter of about 5 m), installed by the Technical University of Brunswick, Germany, were performed. The 11 lysimeters were filled with household refuse and sewage sludge under different conditions (aerobic/anaerobic, compaction, layering). The long-term hydraulic parameters of flow through the lysimeters (transit time, apparent dispersivity, volume of total water) were estimated with a specially adapted black-box model, which used isotopic content curves of rainwater and infiltrated water sampled at different depths in the lysimeters. The transit times of rainwater through the lysimeters (3–6 years) and the mean flow velocities deduced from them (0.4–1 m year−1), correspond to values in the unsaturated zone of sandy aquifers. The dispersivities are in the range of 0.1–1 cm. A special attempt was made to follow individual heavy rain events and estimate the travel times and portions of rainwater percolating swiftly through the lysimeter. It was found that up to 40% of those precipitation events drains off directly, i.e. within a few weeks. However, as it remains only a short time in the lysimeter, this water should not be greatly affected by the lysimeter filling. In addition, by evaluating the δ2H-δ18O relationship of the water samples from the different lysimeter sampling points, it was possible to differentiate, on a preliminary basis, isotopic effects caused by evaporation and biochemical reactions.

Accumulation and ice core-studies on Filchner-Ronne Ice Shelf, Antarctica

Accumulation rates in the eastern part of Ronne Ice Shelf were determined by isotopic stratigraphy eBO). The samples were taken from snow-pits dug during the Filchner I and II operations in 1984 and 1986. In general, the accumulation rate decreases towards the south; the greatest decrease, from 21.3 to 13.3 g cm-2 a-1, was observed between Filchner Station and measuring point 341, sited 270 km up-stream of the ice edge. The SlBO values of the near-surface layers vary between -25 and -29%0. The 1BO content in the more southerly part is progressively depleted in the direction of Mollereisstrom, paralleling a decrease in the accumulation rate. Near the ice edge the 1BO content decreases to the west. A 100 m ice core drilled in 1984 at point 340, 220 km from the ice edge, probably goes back to A.D. 1460; it has been dated by isotopic stratigraphy. The accumulation rate up-stream of the drilling site was deduced from the sequence of annual layers, using a simple ice-flow model. The accumulation shows strong variations over the last 200 years, which may be caused in part by local variations in the accumulation on Ronne Ice Shelf.

THE 520-YEAR TEMPERATURE RECORD OF A 100 M CORE FROM THE RONNE ICE SHELF. ANTARCTICA

THE 520YEAR TEMPERATURE RECORD OF A 100 M CORE FROM THE RONNE ICE SHELF. ANTARCTICA

Vergleich der Deuterium-und Kohlenstoff-13-Gehalte in Fermentations-und Syntheseethanol/Comparison of the Deuterium and Carbon-13 Contents of Ethanol Obtained by Fermentation and Chemical Synthesis

The ratios of deuterium to hydrogen and carbon-13 to carbon-12 expressed as δ D ‰ and d 13C ‰ , respectively, were determined in ten synthetical ethanols of different origin and compared with those of 28 samples of ethanol which were prepared from plant material grown in different places and at different times. The δ D values of the synthetic ethanols are between - 117‰ and - 140‰ and those for ethanol obtained by fermentation between - 200‰ and - 272‰. Using glucose samples of different origins with δ D values between - 3‰ and - 76‰ and water of a δ D value of - 77‰ led to ethanol with drastically diminished deuterium contents ranging from δ D values of -211 to -247‰. The differences of the δ 13C values between ethanols obtained by fermentation of C3 and C4-plant carbohydrates are greater than those between synthetic ethanols and the ethanols obtained from the starch of C3-plants.