The sorption and desorption of uranium on two different clay samples which are obtained from the deposit located in Turgutlu and Kula have been studied by application of a batch technique. The two types of clay materials are Ca-montmorillonite. The uranium concentration range was between 200–3000 ppm. Experimental procedures are outlined and results for uranium contacted with montmorillonite are reported and discussed. The sorption/desorption isotherms were reversible and non-linear for this concentration range. The relative importance of test parameters e.g., pH, clay particle size, temperature, ground water composition, contact — time, solid/water ratio which require definition in order to arrive at meaningful distribution coefficients were carried out. The sorption coefficients varied between 0.65–1.45 and 0.45–1.14 for Kula clay and for Turgutlu clay, respectively. The data could be fitted to Freundlich and Langmuir isotherms. The quantity of the sorbed and desorbed uranium ions was much lower than its theoretical CEC's. This was attributed to a blocking of montmorillonite's CEC by uranium islands sorbed in interlayer. The results have shown that the test parameters can have a marked effect on sorption and the present work provides further evidence of the need to take account of the presence of such materials in safety assessment modeling.
Authors:S. Taysi, N. Oztasan, H. Efe, M.F. Polat, K. Gumustekin, E. Siktar, E. Canakci, F. Akcay, S. Dane and M. Gul
The aim of this study was to investigate whether an 8-week treadmill training attenuates exerciseinduced oxidative stress in rat liver. Male rats were divided into untrained and trained groups. Endurance training consisted of treadmill running at a speed of 2.1 km/h, 1.5 h/day, 5 days a week for 8 weeks. To see the effects of endurance training on acute exhaustive exercise induced oxidative stress, untrained and trained rats were further devided into two groups: animals killed at rest and those killed after acute exhaustive exercise, in which the rats run at 2.1 km/h (10% uphill) until exhaustion. Acute exhaustive exercise increased malondialdehyde level in untrained but not in trained rats. It decreased the activity of glutathione peroxidase and total (enzymatic plus non-enzymatic) superoxide scavenger activity in untrained rats and catalase activity in trained rats. However, it did not affect glutathione S-transferase, glutathione reductase, superoxide dismutase and non-enzymatic superoxide radical scavenger activities in both trained and untrained rats. On the other hand, endurance training decreased glutathione peroxidase and glutathione S-transferase activities. The results suggested that endurance training attenuated exercise-induced oxidative stress in liver, probably by preventing the decreases in glutathione peroxidase and total superoxide scavenger activities during exercise.