Synergistic effects of 4-nitrophenol degradation using gamma irradiation combined with a advanced oxidation process

The radiation-induced degradation of 4-nitrophenol(4-NP) was performed in combination with a Fenton reagent, H_2O_2, and Ti O_2 nanoparticles to investigate the synergetic effects of radiolytical degradation combined with other advanced oxidation processes. The experimental results indicated that the degradation efficiency of 4-NP was 87.5, 57.4, and 41.0 % at a dose of 20 k Gy when its initial concentration was 100, 200, and 350 mg/L, respectively. Radiation combined with H_2O_2, the Fenton method,and Ti O_2 remarkably increased the degradation efficiency of 4-NP, showing the synergetic effects. Radiation may enhance the biodegradability of 4-NP, suggesting that it has the potential to be used as a pretreatment method in combination with the biological method for the treatment of industrial wastewater containing toxic organic pollutants. Major intermediates during the 4-NP degradation process were identified and a possible degradation pathway was tentatively proposed.

Comprehensive two-dimensional river ice model based on boundary-fitted coordinate transformation method

River ice is a natural phenomenon in cold regions,influenced by meteorology,geomorphology,and hydraulic conditions.River ice processes involve complex interactions between hydrodynamic,mechanical,and thermal processes,and they are also influenced by weather and hydrologic conditions.Because natural rivers are serpentine,with bends,narrows,and straight reaches,the commonly-used one-dimensional river ice models and two-dimensional models based on the rectangular Cartesian coordinates are incapable of simulating the physical phenomena accurately.In order to accurately simulate the complicated river geometry and overcome the difficulties of numerical simulation resulting from both complex boundaries and differences between length and width scales,a two-dimensional river ice numerical model based on a boundary-fitted coordinate transformation method was developed.The presented model considers the influence of the frazil ice accumulation under ice cover and the shape of the leading edge of ice cover during the freezing process.The model is capable of determining the velocity field,the distribution of water temperature,the concentration distribution of frazil ice,the transport of floating ice,the progression,stability,and thawing of ice cover,and the transport,accumulation,and erosion of ice under ice cover.A MacCormack scheme was used to solve the equations numerically.The model was validated with field observations from the Hequ Reach of the Yellow River.Comparison of simulation results with field data indicates that the model is capable of simulating the river ice process with high accuracy.

Hydraulic resistance of river ice jams

The hydraulic resistance of the river ice jams consists of the resistances due to the seepage flow through the jam and the shear stress on the undersurface of the jam. Existing empirical formulations consider only the the undersurface resistance of the jam, and come up with relations between the jam resistance and the jam thickness with very slight theoretical basis. Based on the analysis of the seepage flow resistance and the flow resistance of the undersurface of the jam, it is shown that the resistance due to the seepage flow is a dominating part of the jam resistance, except for the portion of the jam where the thickness is very small. This analysis also shows that the total jam resistance can be approximated by a linear function of the jam thickness or the ratio of the jam thickness to the flow depth under the jam.