Bengt Erlandsson

A 10-year study of the 137Cs distribution in soil and a comparison of Cs soil inventory with precipitation-determined deposition.

During a 10-year period, 1988-1998, surface soil samples have been collected at Blentarp in southern Sweden and analysed for 137Cs from the Chernobyl accident and from the nuclear weapons tests. The distance between the sampling plots on the different sampling occasions has been no more than 3 m. The results show that the depth distribution of 137Cs is very similar for each of the sampling occasions, indicating that the caesium migration at this site is very small. The total activity measured in the soil cores is in agreement with the calculated activity of 137Cs deposited at the site after nuclear weapons tests and the Chernobyl accident, based on air activity concentration and the amount of precipitation. The calculated deposition of 137Cs originating from the bomb tests amounts to 1.41 kBq m-2 for the period 1962-1986, which is in agreement with the activity of nuclear weapons fallout measured in the soil samples (1.60 kBq m-2 as a mean value of the first four years of sampling). The calculated activity of 137Cs of Chernobyl origin was 0.79 kBq m-2, which agrees well with the value of 0.79 kBq m-2 measured in the soil samples in 1988.

Experimental determination of the vertical and horizontal distribution of 137Cs in the ground

Abstract The activity of 137 Cs in soil was determined by gamma-spectroscopic measurements on several bore cores, sliced in 2–3 cm layers, taken at four places in Sweden. A method of taking the bore cores in a triangular pattern for the dual purpose of minimizing the number of samples as well as the analysis time was investigated and used to determine the vertical and horizontal behaviour of the distribution of 137 Cs in soil. It was found that cross contamination and compression of the soil during sampling was negligible. The depth distribution of 137 Cs activity, from fallout as well as that from Chernobyl, was found by fitting the experimental points to an exponential function, which was found not to be a simple function of depth. The method of sampling also made it possible to express the depth as linear depth in cm in spite of large variations in soil density. The activity at a given site was shown to be well approximated by a general sample composed of soil from the three bore cores, and the activity uncertainty obtained was about 17%.

Hair Cell Damage In The Guinea Pig Due To Different Kinds Of Noise

Guinea pigs were exposed in groups of five animals to intense pure-tones or impulse noise, where either the intensity or the exposure duration was varied. The damage to the inner ear was analysed histologically and the loss of outer hair cells was used as damage parameter. The intensity in the pure-tone experimets was varied from 102 to 120 dB sound pressure level. The hair cell damage was not increasing proportionally over the entire intensity range. Above a certain critical level of intensity the damages started to increase more rapidly. This could be explained by theories stating that different mechanisms are responsible for the damage below and above the critical level. When the animals were exposed to impulse noise and the duration of the exposure was doubled the hair cell damage was also doubled up to an exposure time of 24 hours. At longer durations the increase of the damage seemed to level off. Animals exposed to impulse noise for 6 hours and with an equivalent sound level of 102 dB showed slightly higher mean damages than animals exposed to a corresponding continuous pure-tone. The results indicate that the total energy concept is a too simplified hypothesis concerning inner ear damage.

Comparison of the Hearing Threshold Measured by Manual Pure-Tone and by Self-Recording (Békésy) Audiometry

The hearing threshold of 115 subjects aged 25--63 years and working on a shipyard were determined both by Békésy sweep audiometry and by conventional manual octave pure-tone audiometry at fixed audiometric frequencies. The attenuation rate was 2.5 dB s-1 with pulsed-tone presentation and the sweep time from 0.25 to 10 kHz was 400 s for the Békésy audiometer. Manual pure-tone audiometry was performed in 5-dB steps. The Békésy method gave the lowest values for the hearing thresholds. It has been possible to find a useful linear relation between pure-tone and Békésy hearing thresholds. With the help of a retest experiment, it has been established, that the standard deviations of hearing thresholds obtained under similar conditions in a pure-tone investigation are about twice as large as those obtained in a Békésy investigation.

Long-term study of 99Tc in the marine environment on the Swedish west coast

The activity concentration of (99)Tc in brown seaweed (Fucus vesiculosus and Fucus serratus) and seawater were analysed in samples collected in 1991, 1995 and 2001 at several stations along the Swedish west coast. In addition to these locations, a well-defined site (Särdal, 56.76 degrees N, 12.63 degrees E) was included with (99)Tc activity concentration data in seaweed from 1967 to 2000. Over the years, the major source of (99)Tc in the coastal waters of western Sweden has been the radioactive liquid discharge from the nuclear fuel reprocessing plant in Sellafield (UK) transported via ocean currents in the North Sea. The (99)Tc activity concentration in seaweed at the Särdal site increased from approximately 30 Bq kg(-1) up to 230 Bq kg(-1) (dry weight) between 1997 and 2000 due to the Sellafield EARP (Enhanced Actinide Removal Plant) discharges in 1995-1996, yielding an approximate transport time of 4-5 years between the Irish Sea and the Kattegat. Due to the very sharp gradient in (99)Tc concentration between the Baltic Sea and the North Sea, (99)Tc is presently one of the best transit tracers for the recent ventilation events in the Baltic Sea.

Radioactivity concentrations in non-nuclear industries

Abstract Radiation and radionuclides are natural phenomena. Small quantities of radionuclides, for example, are always released into the environment when materials are burnt or heated. Large-scale conventional energy sources such as coal and nuclear power have been well investigated for many years with regard to the emission of radionuclides, while emissions from the combustion of peat and wood and from other non-nuclear industries have not been investigated to the same extent. For the nuclear industry in Sweden, the annual dose limit to the public arising from regulated outlets to air and water must not exceed 0.1 mSv year −1 and the global collective effective dose must not exceed 5 person Sv year −1 per GW. A proposed radiation limit for peat power plants in Sweden is also 0.1 mSv year −1 . Like most human pursuits, power-generating and other industrial activities affect the environment negatively but the radiation hazard is generally small compared with other hazards and natural radiation.

Studies of the radon concentration in drinking water from the horst Söderåsen in southern Sweden.

The radon activity concentration in ground water from drilled and dug wells on the horst Söderåsen in Southern Sweden has been determined with two different methods, gamma activity measurements with a germanium HPGe detector and alpha activity measurements with plastic track detectors. The results are consistent. High activity concentration is connected to granite bedrock. Dug wells have low concentrations and no trivial correlation between concentration and depth of the well is found. Large local variations exist. Activity concentrations > 700 Bq/l appear to be associated with leakage from layers of volcanic origin. The concentration from drilled wells is found to be quite constant over a 3 year period but short time variations appear to be significant. Evaporation from the open surface of a normal cooking vessel is slow with an activity gradient delta A/A of about 0.1-0.2 per hour at room temperature whereas even modest heating of water in e.g. a coffee machine is very efficient and reduces the radon activity concentration by > 90% in one process.

Application of accelerator mass spectrometry (AMS) for high-sensitivity measurements of 14CO2 in long-term studies of fat metabolism

Long-term measurements of 14C in CO2 expired after ingestion of 14C-labelled triolein were performed using accelerator mass spectrometry (AMS). About 30% of a given amount of 14C-labelled triolein was catabolized rapidly, while the remaining 70% had a very slow turnover. The study shows the potential of the AMS technique for the study of the long-term biokinetics of 14C-labelled pharmaceuticals. The AMS technique allows the administered activity to be reduced by several orders of magnitude without compromising the study. It may also allow studies of rare drug metabolites.

Transmission of Square Wave Pressure Pulses through the Perilymphatic Fluid in Cats

The inner ear hydrodynamics have been studied in a series of experiments on cats. A detailed analysis has been made of the perilymphatic pressure response to square wave pressure pulses applied to the ear canal and middle ear. It was found that the initial pressure response was followed by a rebound pressure response of the opposite phase. It was also found that in most cases each phase of the pressure response could be expressed in terms of two time constants. When the cochlear aqueduct was patent, the perilymphatic pressure response showed almost equal positive and negative pressure changes. However, when the cochlear aqueduct was surgically blocked, the perilymphatic pressure response consisted almost exclusively of the first phase of the response, while the rebound phase disappeared almost completely. The possibility of influencing the inner ear fluid balance in Menieres disease by external pressure changes is discussed in the light of the present experimental results.

Relation between the air activity and the deposition of Chernobyl debris

Abstract Related and periodical observations of air concentrations and the wet and dry eposition of a large number of radioactive nuclides from the Chernobyl accident have been made at Lund in southern Sweden. Measurements of dry deposition velocities of particles from the explosive first phase of the accident give particle diameters between 2 and 7.5 μm. The total deposition, dry and wet, is in good agreement with in situ measurements. Wet deposition and washout ratios have been calculated from measurements of activity concentrations of radioactive particles in both air and precipitation. A linear relation was found between activity in the air and in precipitation, ranging from μBq m −3 to Bq m −3 .