Release dynamic process identification for a cement based material in various leaching conditions. Part II. Modelling the release dynamics for different leaching conditions

This paper deals with process identification and model development for the case of a porous reference material leaching under certain hydrodynamic conditions. Four different dynamic leaching tests have been applied in order to take into account different types of solid/liquid contact conditions corresponding to various real leaching scenarios: monolithic and granular material with sequential eluate renewal, and granular material and continuously renewed eluate with different hydrodynamic conditions (dispersion, residence time). A coupled chemical-mass transfer model has been developed to describe the leaching behaviour under all experimental conditions. Diffusion has been considered as the mass transport mechanism inside the saturated porous material and dispersive convection as that in the leachate. Two specific phenomena have been identified and considered in the model: (i) the early surface dissolution of the material which results in high Ca concentration and (ii) the late weak dissolution of Na and K giving rise to a long-term residual release. The intrinsic material parameters such as the initial concentrations in the pore water and solid phases were determined by applying equilibrium leaching tests and geochemical modelling. Diffusion coefficients for different elements and the late solubility of alkalines have been found to reach the same values in the four tests. The estimated values of the surface dissolution kinetic constant have shown a dependence on leachate hydrodynamics when the thickness of the degraded layer is nearly the same in the four tests (intrinsic parameter of the material). The competition between the four main dynamic processes, i.e. diffusion, convection, late dissolution, and surface dissolution, has been emphasized and compared in the four leaching tests: the hydrodynamic dispersion and the residence time had no effect on the leaching behaviour of alkalines, which is controlled by diffusion, whereas the behaviour of calcium (a major element of the material) was strongly influenced. This has significant effects on eluate pH values and on the concentration of Pb (the monitored pollutant). The model was then applied to simulate a landfill scenario in the case of a stabilized/solidified incinerator residue containing heavy metals and chloride. A high rain infiltration level and the use of small blocs are favourable conditions for enhanced pollutant release.     

Radon concentration in soil gas around local disjunctive tectonic zones in the Krakow area

The purpose of this study was to investigate radon in the vicinity of geologic fault zones within the Krakow region of Poland, and to determine the influence of such formations on enhanced radon concentrations in soil. Radon ((222)Rn and (220)Rn) concentration measurements in soil gas (using ionization chamber AlphaGUARD PQ2000 PRO and diffusion chambers with CR-39 detectors), as well as radioactive natural isotopes of radium, thorium and potassium in soil samples (using gamma ray spectrometry with NaI(Tl) and HPGe detectors), were performed. Site selection was based on a geological map of Krakow. Geophysical methods (ground penetrating radar and shallow acoustic seismic) were applied to recognize the geological structure of the area and to locate the predicted courses of faults. Elevated levels of radon and thoron in soil gas were found in the study area when compared with those observed in an earlier survey covering Krakow agglomeration. For (222)Rn, the arithmetic mean of registered concentration values was 39 kBq/m(3) (median: 35.5 kBq/m(3)). For (220)Rn, the arithmetic mean was 10.8 kBq/m(3) and median 11.8 kBq/m(3).     

Estimates of (239+240)Pu inventories in Gdańsk Bay and Gdańsk basin

This paper presents and discusses the results of (239+240)Pu determinations in different components of Gdańsk bay and Gdańsk basin ecosystem, as well as estimated sources and inventories of plutonium in these basins. The total plutonium (239+240)Pu activities deposited in Gdańsk bay and Gdańsk basin sediments are 1.18 TBq and 3.77 TBq, respectively. Two rivers, the Vistula and Neman rivers, and atmospheric fallout were distinguished as the main sources of plutonium in these basins. In seawater (with suspended matter included) there is about 2.33 GBq (239+240)Pu (0.2% of total activity) in Gdańsk bay and 9.92 GBq (239+240)Pu (0.3% of total activity) in Gdańsk basin. In both cases, 56% of (239+240)Pu is associated with suspended matter. Organisms contain 3.81 MBq in Gdańsk bay and 7.45 MBq (239+240)Pu in Gdańsk basin. From this value in Gdańsk bay 82.1% of plutonium is associated with zoobenthos, 13.6% with phytobenthos, 1.6% with phytoplankton, 1.5% with zooplankton and 1.2% with fish. In Gdańsk basin, 83.2% is associated with zoobenthos, 7.5% with phytobenthos, 3.6% with phytoplankton, 3.2% with zooplankton and 2.5% with fish.     

Carpal tunnel syndrome in occupational medicine practice.

Work-related overload syndromes are chiefly associated with the upper limbs, where carpal tunnel syndrome (CTS) plays a leading role. This article analyses methods of diagnosing CTS, with special emphasis on those that can be used by physicians in early diagnosis of CTS in workers doing monotonous work. It also discusses occupational (e.g., assembly work, typing, playing instruments, packaging and work associated with the use of a hammer or pruning scissors) and extra-occupational factors (e.g., post-traumatic deformation of bone elements of the carpal tunnel, degenerative and inflammatory changes in tendon sheaths, connective tissue hypertrophy or formation of crystal deposits) leading to CTS; diagnostic methods (subjective symptoms, physical examination and manual provocative tests, vibration perception threshold, electrophysiological examination and imaging methods); and therapeutic and preventive management tools accessible in occupational medicine practice.     

Workers' active involvement in the improvement of occupational safety and health in a textile enterprise--a case study.

Part of the Polish-Swedish OSHMAN project was carried out in a textile company. It aimed at implementing and improving effective health and safety management with workers' active involvement at all levels of the enterprise. The two main problems to be solved during the project were decreasing occupational risk and improving workers' poor knowledge on occupational risk. Training courses, workshops and practical activities were undertaken. As expected, there were changes in work organisation and improvement in the way workstations were looked after, which led to a decrease in occupational risk. Workers were highly committed during the project. Nevertheless it seems that more training should be directed at middle management.     

Monitoring of platinum in the environment

Since the introduction of catalytic converters for the control of vehicle emission, a controversial discussion has begun on platinum emission and its eventual consequences for the environment. This brief overview covers the main aspects of anthropogenic emission of platinum and its bioavailability. Modern analytical methods for Pt determination in different environmental samples are also presented.     

The disposition and metabolism of 1,3-dibromobenzene in the rat

The distribution, excretion and metabolism of 1,3-dibromobenzene following a single i.p. administration to rats 100 or 300 mg/kg was investigated using radiotracer [3H] and GC-MS technique. After 72 hours about 74 to 90% were excreted in urine. The highest radioactivity was observed in the liver, kidneys and fat tissue. Later on a steady decline of radioactivity was apparent in all investigated tissues except for blood cells and the sciatic nerve, where constant levels were noted. In urine the following substances were identified and quantified by GC peak areas: unchanged 1,3-DBB (18%), dibromophenols (34%), dibromothiophenols (28%), dibromothioanisole (1.8%), bromophenol (5.5%), bromohydroxythiophenols (5%), and bromohydroxythioanisole (7.5%).     

Some Remarks About the Effect of Smoke from Charcoal Kilns on Soil Degradation

The charcoal kilns under study were situated in the Polish Western Carpathiens (Bieszczady). Aromatic hydrocarbon products of wood burning in the kilns were identified. The rate of decomposition of beech leaves was relatively high as environmental conditions enhanced decomposition. The intensity of soil metabolism is increasing during a long-term exposure to smoke, which is one of the indicators of anthropogenic disturbance resulting from organic factors.