Changes of Precipitation Infiltration Recharge in the Circumstances of Coal Mining Subsidence in the Shen-Dong Coal Field,China

Coal mining subsidence is a universal environmental-geological problem in mining areas. By selecting the Shen-Dong coal mining subsidence area as the research field, this paper studies the changes in precipitation infiltration recharge in the circumstances of coal mining subsidence by means of field geological investigation and laboratory simulation experiments, which is expected to provide a scientific basis for eco-environmental restoration in the mining area. The results indicate that at the unstable stage of subsidence, three types of subsidence in the Shen-Dong mining area have positive effects on the precipitation infiltration recharge, and the type of full-thickness bedrock subsidence has the greatest influence. In the stable stage of subsidence, the precipitation infiltration process after long- term drought and the moisture migration in the aeration zone undergo three different stages： evaporation-infiltration before precipitation, infiltration-upward infiltration-infiltration during precipitation and evaporation-infiltration after precipitation. During a heavy rainfall infiltration process, the wetting front movement in fine sand, coarse sand and dualistic structure of fine-coarse sand consists of two stages： the stage of wetting front movement during precipitation, in which the wetting front movement distance has linear relationship with the depth, and the stage of wetting front movement after precipitation, in which the wetting front movement distance has the power function relationship with the depth. The wetting front movement velocity is influenced by the rainfall amount and the lithology in the aeration zone. However, as the depth increases, the movement velocity will decay exponentially.

Spatiotemporal Evolution Characteristics Study on the Precipitation Infiltration Recharge over the Past 50 Years in the North China Plain

The spatiotemporal evolution characteristics of precipitation infiltration recharge during the past 50 years are discussed in this paper. This research is significant for groundwater resource rational utilization. The distribution of precipitation infiltration recharge coefficients in the 1960 s, 1980 s, and 2000 s can be obtained using unsaturated zone lithology and depth to water table at different times. The amount of precipitation infiltration recharge in the 1960 s, 1980 s, and 2000 s can be calculated using precipitation infiltration recharge coefficients and precipitation data from the Ministry of Water Resources of China. Results show that the change in the precipitation infiltration recharge coefficient is closely related to the water table decrease. From the 1960 s to the 1980 s, the precipitation infiltration recharge coefficient clearly increased in all units. From the 1980 s to the 2000 s, the value slightly increased in the ancient Yellow River alluvial-proluvial and eastern alluvial-marine plains and slightly decreased in the piedmont alluvial-proluvial and central alluvial-lacustrine plains. The piedmont alluvial-proluvial and ancient Yellow River alluvial-proluvial plains exhibited a large precipitation infiltration recharge coefficient for the coarse lithology. The amounts of precipitation infiltration recharges were 16.23×109（1960s）, 19.11×109（1980s）, and 19.42×109 m3/a（2000s）. The amount of precipitation infiltration recharge increased from the 1960 s to the 1980 s then decreased from the 1980 s to the 2000 s in the piedmont alluvial-proluvial and the central alluvial-lacustrine plains. However, this value increased from the 1960 s to the 2000 s in the ancient Yellow River alluvial-proluvial and eastern alluvial-marine plains.

Dissolution Precipitation Wave Structure of Hydrothermal Ore Zoning

Hydrothermal ore zoning is a transport-reaction problem in which infiltration is the principal Prcness of transport and dissolution/Precipitation is the Principal process of chemical reactions.Neglecting diffusion and ion exchange/adsorption would not affect the basic attributes of hydrothermal ore zoning. Hydrothermal ore zoning belongs essentially to infiltration metasomatic zoning, it results from the formation and propagation of dissolution/precipitation waves through Permeable media. The authors apply the theory of coupled infiltration and dissolution/precipitation reactions in Physicochemical hydrodynamics to studying the structural characteristics of dissolution/precipitation waves, and apply furthermore the coherence principle in dynamic theory of multicomponent coupled systems to revealing the dynamic mechanisms of their formation. The results of investigation verify and develop . C. 's theory of infiltration metasomatic zoning,on the one hand, raising it from the qualitative, equilibrium thermodynamic basis to the quantitative dynamic level;on the other hand, and more importantly, applying theories of Physicochemical hydrodynamics and dynamics of multicomponent coupled systems to bringing to light the dynamic mechanisms of formation of the structure of hydrothermal ore zoning, and advancing a theory of hydrothermal ore zoning, putting forward new ideas on the nature of the problem of hydrothermal ore zoning, the essence of hydrothermal ore zoning and the structural characteristics and mechanisms of formation of hydrothermal ore zoning.

Distribution characteristics of tritium in the soil in Beishan area of Gansu Province

Beishan region in Gansu was the preselected area for China's high-level radioactive waste(HLW) repository. In selecting and evaluating a new dump site, the tritium study is of great significance. The Xinchang-Xiangyangshan preselected area in the Beishan area was taken as an example. This paper selects typical unit and tries to use the distribution characteristics of tritium in the soil to study the atmospheric precipitation infiltration recharge in this area. The results show: In this region, the spatial variability of the tritium content in surface soil is large; it is feasible to use bound tritium tracer method to study the theory of atmospheric precipitation infiltration recharge; the atmospheric precipitation infiltration has close relationship with the soil particle composition, salt content, mineral composition, water content and organic matter content. These results can provide important basis for developing the atmospheric precipitation infiltration recharge, groundwater numerical simulation, nuclide migration study and so on.