[en] Oil spilled onto water may eventually sink because it may be more dense than water (notably some Venezuelan crudes, heavy fuel oils, and residual products), lighter fractions of the oil may evaporate or burn off and leave a dense residue behind, or sediment particles may be incorporated into the oil in the surf zone of beaches. Some spill incidents are reviewed which indicate that oil sinking may be more widespread than is generally believed. The Haven incident at Genoa, Italy in 1991 involved explosions and a fire in a tanker carrying heavy Iranian crude. Surveys confirmed the presence of sunken oil offshore and along the coast. A series of test trawls recovered 1,435 kg of sunken oil, most of which was found in a rectangular area immediately southwest of the wreck measuring 141 km². A similar experience was found in the grounding of the Honam Jade off South Korea. The main part of the oil spill was set on fire, and the residue from the fire sank and affected the local crab fishery. The scope for recovering sunken oil is severely limited, largely to confined areas of sheltered water

[en] The lateral and vertical Gaussian plume dispersion parameters are estimated and compared with field tracer data collected at 11 sites. The dispersion parameter schemes used in this analysis include Cramer's scheme, suggested for tall stack dispersion estimates, Draxler's scheme, suggested for elevated and surface releases, Pasquill's scheme, suggested for interim use in dispersion estimates, and the Pasquill--Gifford scheme using Turner's technique for assigning stability categories. The schemes suggested by Cramer, Draxler and Pasquill estimate the dispersion parameters using onsite measurements of the vertical and lateral wind-velocity variances at the effective release height. The performances of these schemes in estimating the dispersion parameters are compared with that of the Pasquill--Gifford scheme, using the Prairie Grass and Karlsruhe data. For these two experiments, the estimates of the dispersion parameters using Draxler's scheme correlate better with the measurements than did estimates using the Pasquill--Gifford scheme. Comparison of the dispersion parameter estimates with the measurement suggests that Draxler's scheme for characterizing the dispersion results in the smallest mean fractional error in the estimated dispersion parameters and the smallest variance of the fractional errors

No abstract available

[en] Groundwater discharge represents a major pathway for the return to the biosphere of contaminants that are released to the subsurface environment. An understanding of the transport processes in groundwater discharge zones is therefore an important consideration in pathway analyses associated with the environmental assessment of proposed waste-management facilities. Shallow water tables are a common characteristic of groundwater discharge zones, particularly in humid climatic regions. In this paper, the results of field tests, laboratory tests and numerical simulations are used to show that under shallow water-table conditions, the zone of tension saturation can result in a rapid and highly disproportionate water-table response to precipitation. It is further shown that this response can result in complex migration patterns that would not be predicted by the classical approaches to solute transport modelling and that the response could result in large and highly transient inputs to surface water

No abstract available

No abstract available

[en] Environmental tritium concentrations will be measured near the Tokamak Fusion Test Reactor (TFTR) to help validate dynamic models of tritium transport in the environment. For model validation the database must contain sequential measurements of tritium concentrations in key environmental compartments. Since complete containment of tritium is an operational goal, the supplementary monitoring program should be able to glean useful data from an unscheduled acute release. Portable air samplers will be used to take samples automatically every 4 hours for a weak after an acute release, thus obtaining the time resolution needed for code validation. Samples of soil, vegetation, and foodstuffs will be gathered daily at the same locations as the active air monitors. The database may help validate the plant/soil/air part of tritium transport models and enhance environmental tritium transport understanding for the International Thermonuclear Experimental Reactor (ITER)

[en] Poster presentation

[en] Full text: The principal source of exposure to radiation for public in built-up areas is known to be the inhalation for radon its short-lived daughters.Most of this exposure occurs inside homes,where many hours are spent each day and where the volumic activity of radon is usually higher than outdoors. The compelling effects of radon and its short-lived decay products spread slowly but surely through a wide range of biological problems encountered in such areas as the mortality rates and lung cancer in uranium mines,the results of experimental work with animals, and the discovery of unsually high levels of radon in the living environments of the general population. As a way of prevention, we have measured the volumic activities of indoor radon-222 and we have calculated their effective equivalent dose in some dwellings and enclosed areas in Morocco. The obtained results show that the effective equivalent dose of activities measured indoor dwellings are inferior to the admissible annual limit fixed by ICRP for population, except in two twons situated in regions rich in phosphate deposits where the calculated doses are slightly upper than this limit. The results obtained for enclosed areas are inferior to the admissible annual limit fixed by ICRP for workers, except in the cave of geophysical observatory situated at depth of-12 meters where the obtained value don't present in risk for workers health because workers pass only a few minutes by day in this cave. The risks related to the volumic activities for indoor radon could be avoided by simple precautions such the continuous ventilation

[en] Full text: Since the beginning of the 90's, our laboratory has participated in routine programs on environmental and radiological surveillance of both wide and local areas. The programs include periodic radioactivity measurements in a different kind of sample : drinking water, milk, soils, aerosols, foodstuff, vegetation, etc, determining gross alpha- and beta-counting, and activity concentration of gamma- and alpha_emitters. Other particular measurements involve 3H and 90Sr activity concentration in the same kinds of samples. For these objectives, our laboratory has developed different radiochemical and measurement methods according to the kind of the sample and the radioisotopes of interest. In this paper, we will show the optimization and calibration performed of several radiometric systems for the low-level measurements of different radionuclides: a low-background gas proportional counter for measuring gross alpha- and beta-counting, and 90Sr-activity, a low-background liquid scintillation spectrometer for the measurement of 3H-, 226Ra- and 210Pb-activities, a low-level gamma-spectrometric system with thin-window Ge detector for the measurement of gamma emitters, etc. In addition, radiochemical procedures, which are needed for the measurement of the activity concentration of selected radionuclides (90Sr, 3H, 226Ra and 210Pb) will be also described in this contribution