开发建设项目水蚀量预测方法研究

开发建设项目中水蚀量的预测方法研究对于防治新的水土流失具有十分重要的意义。在查阅已编报部审的水保方案和国内外有关此研究文献的基础上,对我国目前水保方案中用到的预测方法进行了介绍和评价,同时对国内外开发建设项目水蚀预测方面的研究进展进行了综述。

松辽流域土壤水蚀量与下垫面各因素的关系

通过对松辽流域土镶侵蚀资料的收集整理，运用线性模型理论，对流域土壤水蚀规律进行了综合分析。找出了在影响土壤水蚀量的诸因子中，植被覆盖度及坡度起主导作用。防止土壤水蚀应以生物措施为主。在该流域中，受人为活动影响较大的台地、丘陵、低山区应是防治土镶水蚀的重点地区。

Effect of water content on corrosion inhibition behavior of self-assembled TDPA on aluminum alloy surface

Self assembled monolayers （SAMs） of 1-tetradecylphosphonic acids （TDPA, CH3（CH2）13P（O）（OH）2 ） were formed on the 2024 aluminum alloy surface in TDPA-containing ethanol-water solutions with different water content. The adsorption and corrosion protection properties of the SAMs for 2024 alloy in 0.1 mol/L H2SO4 solution were examined and characterized by potentiodynamic polarization, electrochemical impedance spectrum （EIS）, Fourier transformed infrared spectroscopy （FTIR）, Auger electron spectra （AES） and atomic force microscopy （AFM）. FTIR and AES results show that the TDPA molecules were successfully adsorbed on the 2024 aluminum alloy surface, and the density of the SAMs increased with the increasing water content in the assembly solution. The results of electrochemical studies and corrosion morphologies observed by AFM show that a 4 h modification resulted in maximal inhibition efficiency, and the higher the water content in the assembly solution is, the better the inhibition performance of the SAMs can be achieved. The effect of water content in TDPA solutions on the performance of the SAMs is related to the hydration reaction of the metal surface.

The runoff characteristics and harmonic analysis of the soil moisture dynamics in Robinia pseudoacacia stand

Robinia pseudoacacia stands act as a typical ecological protection forest in hilly semi-arid area of China. Two fields of surface runoff were separately set up in R. pseudoacacia stand and its clearcut area in the western Liaoning Province (1850-12225 E, 4024-4234 N) for measuring the characteristics of runoff and sediment as well as soil moisture dynamics. Contractive analysis of the two land types showed that there existed a significant difference in volumes of runoff and sediment between the sites of R. pseudoacacia stand and its clearcut area. The runoff volume and sediment volume in clearcut area were much bigger than those in R. pseudoacacia stand, with an increase amount of 40%-177% for runoff and 180%-400% for sediment. Hydrograph of surface runoff of typical rainfall showed that the peak value of runoff in R. pseudoacacia stand was decreased by 1.0-2.5?0-3m3s-1 compared with that in its clearcut area, and the occurring time of peak value of runoff in R. pseudoacacia stand was 10-20 min later than that in its clearcut area. Harmonic analysis of soil moisture dynamics indicated that the soil moisture in R. pseudoacacia stand was 2.3 % higher than that in clearcut area, and the soil moisture both in R. pseudoacacia stand and its clearcut area could be divided into dry season and humid season and varied periodically with annual rainfall precipitation. It was concluded that R. pseudoacacia stand plays a very important role in storing water, increasing soil moisture, and reducing surface runoff and soil erosion.

Corrosion behavior of porous Ti_3SiC_2 in nitric acid and aqua regia

Porous Ti3SiC2with high purity was synthesized using TiH2,Si and C powders with mole ratio of Ti to Si to C being3:1.2:2by reactive synthesis method.The corrosion behaviors of porous Ti3SiC2in nitric acid and aqua regia were investigated byimmersing test.Scanning electron microscope(SEM),X-ray diffractometer(XRD),energy dispersive spectrometer(EDS)and X-rayphotoelectron spectroscopy(XPS)were used to analyze the morphology,compositions and element contents of the samples beforeand after corrosion to determine the corrosion product and corrosion mechanism.The mass loss values of porous Ti3SiC2are26.9and132.5μg/cm2,respectively after immersing in nitric acid and aqua regia for600h.The results indicate that Ti3SiC2transforms toTi5Si3which has better corrosion resistance in nitric acid and aqua regia with mass loss values of9.34and7.06μg/cm2under thesame immersing time,respectively.The dramatic dissolution of porous Ti3SiC2in the acids is due to its special microstructure.

A damage constitutive model of rock-like materials containing a single crack under the action of chemical corrosion and uniaxial compression

To describe the deformation and strength characteristics of the corroded rock-like specimens containing a single crack under uniaxial compression,a damage constitutive model combining hydro-chemical damage with coupling damage of micro-flaws and macro-cracks is proposed.Firstly,based on phenomenological theory,the damage variable of the rock-like specimens subjected to water environment erosion and chemical corrosion is obtained.Secondly,a coupled damage variable for cracked rock-like specimens is derived based on the Lemaitre strain equivalence hypothesis,which combines the Weibull statistical damage model for micro-flaws and the fracture mechanics model for a macro single crack.Then,considering the residual strength characteristics of the rock-like materials,the damage variable is modified by introducing the correction coefficient,and the damage constitutive model of the corroded rock-like specimens with a single crack under uniaxial compression is established.The model is verified by comparing the experimental stress−strain curves,and the results are in good agreement with those provided in the literature.Finally,the correction coefficient of the damage variable proposed in this paper is discussed.The damage constitutive model developed in this paper provides an effective method to describe the stress−strain relationship and residual strength characteristics of the corroded rock-like specimens with a single crack under uniaxial compression.

Soil Erosion and Sediment Control Effects in the Three Gorges Reservoir Region, China

The Three Gorges Reservoir, the world’s largest hydropower reservoir, receives a significant sediment yield from soil erosion. Sloping farmland is the main source, exacerbated by changes in land use from relocating the inhabitants, and from engineering projects related to dam construction. Related geo-hazards, including landsliding of valley-side slopes, will further increase the sediment yield to the completed reservoir. Integrated watershed management, begun extensively in 1989, has effectively controlled soil erosion and sediment delivery to date. What is described here as the Taipinxi Mode of integrated watershed management, based on its application in the 26.14 km2 watershed of that name in Yiling District, has been successful and is recommended for the entire region. The effects of this set of erosion-mitigation measures are assessed, using experienced formulas for soil and water conservation and information from remote sensing. The amount of soil erosion, and of sediment delivery to the reservoir were reduced by 43.75–45.94 × 106 t y-1, and by 12.25–12.86 × 106 t y-1, respectively, by 2005, by which time the project had been operative for 16 years.

Excellent long-term reactivity of inhomogeneous nanoscale Fe-based metallic glass in wastewater purification

Metallic glasses(MGs)have attracted great attention in wastewater treatment because of their high reactivity arising from amorphous structure,large residual stress and high density of low coordination sites.However,the reactivity of MGs would gradually slow down with time due to the passivation of active sites by corrosion products,resulting in limited long-term reactivity,which is also an unsolved key issue for established crystalline zero valent iron(ZVI)technology.Here,such problems are successfully overcome by introducing nanoscale chemical inhomogeneities in Fe-based MG(Fe-MGI),which apparently contributes to local galvanic cell effect and accelerates electron transfer during degradation process.More importantly,the selective depletion of Fe0 causes local volume shrinkage and crack formation,leading to self-peeling of precipitated corrosion products and reacted regions.Thereby fresh low coordination sites could be continuously provided,counteracting the mass transport and reactivity deteriorating problem.Consequently,Fe-MGI demonstrates excellent long-term reactivity and self-refreshing properties even in neutral solution.The present results provide not only a new candidate but also a new route of designing ZVI materials for wastewater treatment.