ECOPERSIA
Pre-Issue 1, 2011

Ground skidding on skid trails affects the physical properties of soil. The objective of this study was to evaluate changes in soil physical properties on skid trails formed due to traffic of metal-tracked skidders with regard to soil bulk density, total porosity, water content and penetration resistance. The studies were implemented on two levels of slope – <20% (SC1) and >20% (SC2) – and three levels of traffic (one, five and nine traffic cycles). The treatment plots with three replications, consequently, were 6 m long and 4 m wide. The measurement of soil penetration resistance was carried out using a cone penetrometer. The samples were taken from 10 cm of top soil at six points in each plot. The results indicated that the skidder traffic did not significantly affect the soil physical properties measured in three levels of traffic at SC1, whereas it was significant between one and five traffic cycles in SC2. Most of the changes in the measured properties in the skid trails occurred after the first loaded skidder traffic. Within all traffic of SC2, differences in the mean values of water content and soil porosity were greater compared with the mean values at the same traffic of SC1, although these differences were not significant. The bulk density and penetration resistance at five and nine traffics of SC2 were significantly different from the same traffic of SC1.

Histopathological and pathomorphological effects of 15 ppb mercuric chloride on Persian sturgeon, Acipenser persicus, were investigated using histological and electron microscopy observations. Light microscopy showed that the gill epithelial hypertrophy, wrinkling and hyperplasia in lamellar epithelia and lamellae fusion occurred after 48 h of exposure. Gill epithelia also showed occasional necrosis, which had almost been completed and blood emerged from the capillaries. However, occasional necrosis in some regions of the filament, both with blood emerging and with no bleeding, was observed by using electron microscopy. These injuries were well observed in inter-lamellar regions of the filament and also wrinkling of the lamellar epithelium. Ultrastructural observations showed some cellular disorders in gill epithelium of the Persian sturgeon, A. persicus, fry. In addition, increase in apical vesicles of the chloride cells and necrosis in apical surfaces of some chloride cells, hypertrophy and necrosis of the chloride cells’ mitochondrion and endoplasmic reticulum also were some of the other cellular disorders observed through transmission electron microscopy. In conclusion, the gills of A. persicus fry were sensitive to low concentrations of inorganic mercury (HgCl2).

A numerical model for two-phase debris flows is developed in this paper, on the basis of understanding of the physical characteristics of debris flows from field investigations and experiments. Employing a moving coordinate, the kinetic energy equation of gravel particles in unit volume in debris flow is developed by considering the potential energy of the particles, energy from the liquid phase, energy consumption due to inner friction-collision between the particles, energy dispersion through collisions between particles, energy for inertia force, energy consumption due to the friction with the rough bed and energy consumption at the debris front. The model is compared with measured results of two-phase debris flow experiments and the calculated velocity profiles agree well with the measured profiles. The gravel’s velocity at the debris flow head is much smaller than that of particles in the following part and the velocity profile at the front of the debris flow wave is almost linear, but the profile in the main flow shows an inverse ‘s’ shape. This is because the gravel particles in the main flow accelerate as they receive energy from the gravitational energy and flowing liquid and decelerate as they transmit the energy to the debris flow head and consume energy due to collision with the channel bed.