抢救“土壤水库”实为黄土高原生态环境综合治理与可持续发展的关键——四论黄土高原国土整治28字方略

现在全国上下深切关注着黄河的重大问题及其对策。其实问题的根源都出自人们对黄河流域尤其黄土高原自然资源的掠夺式开发 ,形成了“3个恶性循环”:广种薄收 ,薄收更广种 ,虽是罪魁祸首 ,但常反被忽视 ,致使生态环境脆弱 ,人民长期贫困 ;只有下游河床越淤越高 ,防洪大堤越筑越高 ,越高越险和断流历时越来越长 ,上溯速度越来越快 2个恶性循环的危害才使人惊恐。不难看出 ,这是恰与形成黄土高原自然规律完全相悖的人为地质过程的结果。可惜它还未引起人们深入充分的认识 ,难怪一向短缺一个为各家合力共识的治本对策。当今国家将经济发展的重点向中、西部转移 ,并要求重建一个山川秀美的大西北 ,黄土高原的持续开发与治理对策就显得更为举足轻重。由此其各项对策都将面临着转变观念、调整思路、实事求是地进行科学分析和抉择。笔者最近从陆地生态的发生发展及其整个地质历史演变过程的研究中发现 :“土壤水库”的发生发展及其演变是陆地生态发生发展的关键和“动力”,只要维护土壤水库的正常发展就能更好地保卫生态环境。黄土高原地区由于得天独厚的降尘堆积环境条件和持续的成壤过程 ,可使降水具有直接渗入“地下水库”的特殊功能。只要维护住高入渗土壤水库的存在就...

Nutrient characteristics in the Yangtze River Estuary and the adjacent East China Sea before and after impoundment of the Three Gorges Dam

From November 2002 to 2006, five cruises were undertaken in the Yangtze River Estuary and the adjacent East China Sea to compare the nutrient concentrations, ratios and potential nutrient limitation of phytoplankton growth before and after impoundment (June 2003) of the Three Gorges Dam (TGD). Concentrations of dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP) and total nitrogen (TN) exhibited an increasing trend from 2002 to 2006. In contrast, total phosphorus (TP) concentration exhibited a decreasing trend. The mean concentrations of DIN, SRP, and TN in the total study area increased from 21.4 mu M, 0.9 mu M, and 41.8 mu M in 2002 to 37.5 mu M, 1.3 mu M. and 82.2 mu M in 2006, respectively. while TP decreased from 2.1 mu M to 1.7 mu M. The concentration of dissolved reactive silica (DRSi) had no major fluctuations and the differences were not significant. The mean concentration of DRSi in the total study area ranged from 52.5 to 92.3 mu M. The Si:N ratio decreased significantly from 2.7 in 2002 to 1.3 in 2006, while TN: TP ratio increased from 22.1 to 80.3. The area of potential P limitation of phytoplankton growth expanded after 2003 and potential Si limitation appeared in 2005 and 2006. Potential P limitation mainly occurred in an area of salinity less than 30 after 2003, while potential Si limitation occurred where the salinity was greater than 30. By comparison with historical data, the concentrations of nitrate and SRP in this upper estuary during November 1980-2006 increased obviously after impoundment of TGD but DRSi decreased. Meanwhile, the ratios of N:P, Si:N and Si:P decreased obviously. (c) 2009 Elsevier B.V. All rights reserved.

Size-fractionated phytoplankton biomass in autumn of the Changjiang (Yangtze) River Estuary and its adjacent waters after the Three Gorges Dam construction

A cruise was undertaken from 3rd to 8th November 2004 in Changjiang (Yangtze) River Estuary and its adjacent waters to investigate the spatial biomass distribution and size composition of phytoplankton. Chlorophyll-a (Chl-a) concentration ranged 0.42-1.17 mu g L-1 and 0.41-10.43 mu g L-1 inside and outside the river mouth, with the mean value 0.73 mu g L-1 and 1.86 mu g L-1, respectively. Compared with the Chl-a concentration in summer of 2004, the mean value was much lower inside, and a little higher outside the river mouth. The maximal Chl-a was 10.43 mu g L-1 at station 18 (122.67 degrees E, 31.25 degrees N), and the region of high Chl-a concentration was observed in the central survey area between 122.5 degrees E and 123.0 degrees E. In the stations located east of 122.5 degrees E, Chl-a concentration was generally high in the upper layers above 5 m due to water stratification. In the survey area, the average Chl-a in sizes of > 20 mu m and < 20 mu m was 0.28 mu g L-1 and 1.40 mu g L-1, respectively. High Chl-a concentration of < 20 mu m size-fraction indicated that the nanophytoplankton and picophytoplankton contributed the most to the biomass of phytoplankton. Skeletonema costatum, Prorocentrum micans and Scrippsiella trochoidea were the dominant species in surface water. The spatial distribution of cell abundance of phytoplankton was patchy and did not agree well with that of Chl-a, as the cell abundance could not distinguish the differences in shape and size of phytoplankton cells. Nitrate and silicate behaved conservatively, but the former could probably be the limitation factor to algal biomass at offshore stations. The distribution of phosphate scattered considerably, and its relation to the phytoplankton biomass was complicated.

降雨条件下碎石土滑坡稳定性研究

Debris Landslide is one of the types of landslides with the widest distribution, largest quantity, and the closest relationship with engineering construction. It is also one of the most important types of landslides that can cause disaster. This kind of landslide often occurs in the loose slopes which are made up of loose congeries formed by earth filling, residual soil, slope wash, dilapidation, landslide or full weathered material of hard rock. Rainfall is always the chief inducing factor of debris Landslide. Therefore, to research stability of debris Landslide during rainfall not only has important theoretical significance for understanding developing law and deformation and failure mechanism of debris landslide, but also has important practical significance for investigating, appraising, forecasting, preventing and controlling debris landslides. This thesis systematically summarized the relationships between rainfall and landslide, the method to survey water table in the landslides, the deformation and failure mechanism of debris landslide, and the progress in the stability analysis of landslides based on the analyses of data collected widely at home and abroad. The problems in the study of the stability of debris landslide during rainfall was reviewed and discussed. Due to the complicated geological conditions and the random rainfall conditions, the research on the landslides' stability must be based on engineering geological qualitative analysis. Through the collection of the data about the Panxi region and the Three Gorges Reservoir region, the author systematically summarized the engineering geological conditions, hydro-geological condition, distribution characteristics of stress field in the slope, physical and mechanical properties and hydro-mechanical properties of debris. In the viewpoint of dynamics of soil water and hydromechanics, physical process of rainfall to supply groundwater of debris landslides can be divided into two phases, i.e. non-saturated steady infiltrating phase and saturated unsteady supplying phase. The former can be described by mathematical model of surface water infiltration while the latter can be described by equivalent continuous medium model of groundwater seepage. With regard to specific hydrological geology system, we can obtain the dynamic variation law of water content, water table, landslide stability of rock and soil mass, along with quantity and duration of rainfall after the boundary condition on hydrological geology has been ascertained. This is a new way to study the response law of groundwater in the landslides during rainfall. After wet face of rock and soil mass connects with ground water table, the raising of water table will occur due to the supply of rainfall. Then interaction between ground water and rock and soil mass will occur, such as the action of physics, water, chemistry and mechanics, which caused the decrease of shearing strength of sliding zone. According to the action of groundwater on rock and soil mass, a concise mechanical model of debris landslide’s deformation was established during rainfall. The static equilibrium condition of landslide mass system was achieved according to the concise mechanical model, and then the typical deformation and failure process and failure mode of debris landslide during rainfall were discussed. In this thesis, the former limiting equilibrium slice method was modified and improved based on shearing strength theory of , a stability analysis program of debris landslide was established and developed taking account of the saturated-unsaturated seepage, by introducing the shearing strength theory of unsaturated soil mass made by (1978). The program has reasonable data storage and simple interface and is easy to operate, and can be perfectly used to carry out sensitivity analysis of influencing factors of landslides' stability, integrated with the program of Office Excel. The design of drainage engineering are always bases on empirical methods and is short of effective quantitative analysis and appraise, therefore, the conception of critical water table of debris landslide was put forward. For debris landslides with different kinds of slide face in the engineering practice, a program to search the critical water table of debris landslide was developed based on native groundwater table. And groundwater table in the slope should be declined below the critical water table in the drainage works, so the program can be directly used to guide drainage works in the debris landslide. Taking the slope deformation body in the back of former factory building of Muli Shawan hydroelectric power station as an example, a systematic and detailed research on debris landslides' stability during rainfall was researched systematically, the relationship among quantity of rainfall, water table and stability of slope was established, the debris landslides' stability in process of rainfall from dynamic viewpoint was analyzed and researched.