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H Hötzl

Publications and source records attributed to H Hötzl.

12 recordsLinked to original sources
PubMed2006

Integrating groundwater into urban water management.

The management of urban groundwater resources is directly linked to urban water supply and drainage concepts. A proper integration of groundwater into urban water management plans is recommended for long-term planning. The paper describes the development of a new modelling suite which addresses the urban water and solute balance in a holistic way. Special focus has been placed on the assessment of the impact of sewer leakage on groundwater in four case study cities. Tools for the prediction of sewer leakage including the assessment of uncertainties are now available. Field investigations in four European case study cities were able to trace the influence of sewer leakage on urban groundwater using microbiological indicators and pharmaceutical residues.

Cities↗
PubMed1996

The ratio of long-lived to short-lived radon-222 progeny concentrations in ground-level air.

The ratio of 210Pb air concentration to the short-lived radon (222Rn) decay products concentration at ground level was investigated at a semi-rural location 10 km north of Munich, south Germany, for a period of 11 years (1982-1992). The average ratio from 132 monthly mean values has been found to be (7.5 +/- 2.2) x 10-5 (arithmetic mean +/- S.D.). While the time series of the short-lived radon daughter concentration exhibit a distinct seasonal pattern with maxima mostly in October of each year, the course of 210Pb air concentration is characterized by high values from October through February. Consequently, high ratios of 210Pb to short-lived decay product concentration are often observed in the winter months of December-February. To study the influence of meteorological conditions on this behaviour, 210Pb and 214Pb concentrations were measured on a short-term basis with sampling intervals of 2-3 days from October 1991 to November 1992. The air concentrations obtained within those intervals were then correlated with actual meteorological parameters. On the base of this investigation the seasonal behaviour can essentially be explained by the more frequent inversion weather conditions in winter than in the summer months. At the same location, the average ratio of 210Po to 210Pb concentration in ground level air has been found to be 0.079 from 459 weekly mean values between 1976 and 1985. Hence, the corresponding average ratios of the short-lived radon daughters (EEC) to 210Pb and 210Po, were 1:7.5 x 10(-5) and l:0.6 x 10(-5), respectively.

Air Pollutants, Radioactive↗
PubMed1996

Comparison of direct alpha spectrometry and neutron activation analysis of aerosol filters for determination of workplace thorium air concentrations.

Direct alpha spectrometry with three different filter types was investigated for the determination of thorium air concentrations at workplaces in the manufacturing process of discharge lamps containing thoriated tungsten electrodes. The method was compared with neutron activation analysis over an activity range of five orders of magnitude. Within the experimental limits of error, both methods were found to be comparable with respect to sensitivity and accuracy. The advantage of direct alpha spectrometry, however, is that it is less laborious than neutron activation analysis and that it supplies information on the degree of radioactive equilibrium of the thorium series, which is important with regard to the estimation of dose.

Aerosols↗
PubMed1994

Long-term variation of outdoor radon equilibrium equivalent concentration.

Long-term variation of outdoor radon equilibrium equivalent concentration was investigated from 1982 to 1992 at a semi-natural location 10 km north of Munich, southern Germany. For this period the continuous measurement yielded a long-term average of 8.6 Bq.m-3 (arithmetic mean) and 6.9 Bq.m-3 (geometric mean), from which an average annual effective dose of 0.14 mSv due to outdoor radon can be derived. A long-term trend of the radon concentration was not detectable over the whole period of observation. However, by time series analysis, a long-term cyclic pattern was identified with two maxima (1984-1986, 1989-1991) and two minima (1982-1983, 1987-1988). The seasonal pattern is characterized by an autumn maximum and an early summer minimum. On average, the seasonal maximum in October was found to be higher by a factor of 2 than the June minimum. The diurnal variation of the radon concentration shows a maximum in the early morning and a minimum in the afternoon. On average, this maximum is a factor of 2 higher than the minimum. In the long term a seasonal pattern was observed for diurnal variation, with an average diurnal maximum to minimum ratio of 1.5 in winter compared with 3.5 in the summer months. The radon concentration is correlated with a meteorological parameter (stagnation index) which takes into account horizontal and vertical exchange processes and the wash-out of aerosols in the lower atmosphere.

Air Pollutants, Radioactive↗
PubMed1993

Rapid determination of radon daughters and of artificial radionuclides in air by online gamma-ray spectrometry.

For the determination of airborne radionuclide concentrations in real time, a fixed filter device was constructed which fits directly onto a germanium detector with standard nuclear electronics and a multichannel analyzer buffer connected via a data line to a personal computer for remote control and on-line spectrum evaluation. The on-line gamma-ray spectrometer was applied to the study of radon decay product concentrations in ground-level air and to the rapid detection of any contamination of the environmental air by artificial radionuclides. At Munich-Neuherberg, depending on the meterological conditions, the measured air concentrations of 214Pb, the first gamma-ray-emitting member of the 222Rn decay series, varied from about 1 to 50 Bq m-3. For the artificial radionuclides 60Co, 131I and 137Cs the detection limits were determined as a function of the varying natural radon daughter concentrations at sampling and counting times of 1 h or 1 day. For these radionuclides minimum detectable air activity concentrations of 0.3 or 0.001 Bq m-3, respectively, were obtained at low radon daughter levels. At high radon daughter levels the respective detection limits were found to be higher by a factor of only about 2.

Accidents↗
PubMed1992

Sources of present Chernobyl-derived caesium concentrations in surface air and deposition samples.

The sources of Chernobyl-derived caesium concentrations in air and deposition samples collected from mid-1986 to the end of 1990 at Munich-Neuherberg, Germany, were investigated. Local resuspension has been found to be the main source. By comparison with deposition data from other locations it is estimated that within a range from 20 Bq m-2 to 60 kBq m-2 of initially deposited 137Cs activity approximately 2% is re-deposited by the process of local resuspension in Austria, Germany, Japan and the United Kingdom, while significantly higher total resuspension is to be expected for Denmark and Finland. Stratospheric contribution to the present concentrations is shown to be negligible. This is confirmed by cross correlation analysis between the time series of 137Cs in air and precipitation before and after the Chernobyl accident and the respective time series of cosmogenic 7Be, which is an indicator of stratospheric input. Seasonal variations of caesium concentrations with maxima in the winter months were observed.

Accidents↗
PubMed1990

Effect of dry deposition, washout and resuspension on radionuclide ratios after the Chernobyl accident.

The temporal variations of radionuclide ratios in air and deposition samples collected simultaneously at Munich-Neuherberg (F.R.G.) after the Chernobyl accident have been studied. Until 8 May 1986, the radionuclides investigated were 99Mo, 103Ru, 106Ru, 110mAg, 125Sb, 129mTe, 132Te, 131I, 134Cs, 137Cs, 140Ba, 141Ce and 144Ce. After 8 May, 99Mo, 110mAg, 125Sb, and the Ce isotopes were below the detection limits. Considerable temporal variations of the above radionuclides, relative to 137Cs, were observed in air as well as in deposition. In air the temporal variations reflect the arrival of different parts of the reactor plume with different elemental composition. In deposition, the temporal patterns were quite different from those in air for a given radionuclide. This is explained by varying contributions of dry and wet deposition. Until 8 May, the washout ratios of the above radionuclides covered a range from 240 to 5600, with smaller variations for all radionuclides within one event (e.g. 460-910), and larger variations from one event to another (e.g. 460-3300 for 137Cs). The dry deposition velocity of 137Cs was found to be 0.27 cm s-1, similar to that of 110mAg, aerosol 131I and 140Ba (0.37, 0.13 and 0.15 cm s-1). Another group of radionuclides includes 103Ru, 106Ru, 125Sb, total 131I and 132Te with dry deposition velocities of 0.08, 0.10, 0.07, 0.03 and 0.08 cm s-1 and with temporal variations in deposition which are quite different from those of the first group. From 8 May to the end of June, the washout ratios increased to values between 1500 and 24,000, with the exception of iodine, which had considerably lower washout ratios of between 37 and 4400. These later effects are explained by resuspension and, in the case of iodine, by remobilization of gaseous species.

Accidents↗
PubMedDate not supplied

Contaminant transport in fractured chalk: laboratory and field experiments.

Laboratory experiments were performed on chalk samples from Denmark and Israel to determine diffusion and distribution coefficients. Batch tests were used to define sorption isotherms for naphthalene and o-xylene. Linear sorption isotherms were observed and described with Henry-isotherms. Because of the high purity and low contents of clay minerals and organic carbon, Danish and white Israeli chalk generally have low retardation capacities. Contrarily, gray Israeli chalk, with organic carbon fractions as high as 1.092%, remarkably retards organic contaminants. The K(OC) concept is not applicable to predicting distribution coefficients based on the organic carbon content in the chalk samples. Effective diffusivities of o-xylene, naphthalene, and several artificial tracers were determined using through-diffusion experiments. Based on measured diffusion coefficients and available literature values, a chalk specific exponent of 2.36 for Archie's law was derived, allowing a satisfactory estimate of relative diffusivities in chalk. A field-scale tracer test with uranine and lithium was performed in the Negev desert (Israel) to examine the transferability of diffusivities determined on small rock samples in the laboratory. Due to low recovery rates of the tracer, a modified single fissure dispersion model was used for inverse modeling of the breakthrough curves. Resulting diffusivities deviate insignificantly from the laboratory values, which are considered to be representative for the investigated part of the aquifer and applicable in transport models.

Calcium Carbonate↗