Problems of reservoir sedimentation in China

As there are many heavily sediment-laden rivers in China, with high sediment concentration and a large quantity of sediment load, the sedimentation problems of the reservoirs built on those rivers are so serious that the amount of sediment deposited in the reservoirs is great and the rate of sedimentation is accelerated. According to the statistics, up to the end of 1981, a total amount of 11.5×10⁹m³ of sediment were accumulated in those reservoirs, i.e. 14.2% of the total designed capacity were lost. The average annual loss in storage capacity reached 2.3 percent, being the highest in the world. Silting of impounding lakes not only has an effect on the benefits of the reservoirs and seriously threatens the life of reservoirs, but also results in many environmental problems which were not fully estimated in the planning of the reservoirs. In this paper, the situation of reservoir deposition in China are described from the following aspects: 1) the characteristics of hydrology and sediment of the rivers; 2) the seriousness of reservoir sedimentation in China; 3) problems caused by reservoir deposition; 4) the methods of minimizing sediment deposition, etc.     

Multivariate canonical correlation techniques: An economic approach for evaluation of pollutants in soil and sediments of Bombay region, India

Multivariate canonical correlation analysis has been carried out taking physical variables (mean, standard deviation, skewness, kurtosis) as predictors and chemical variables (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) as responses from the soils and sediments of Thane Creek and Ulhas River areas in Bombay, India. Soil samples provide the first canonical correlation to the presence of more clay fractions, which controls the concentration of trace elements such as Co, Fe, and Ni. In sediment samples, the first canonical correlation explains the role of mean particle size in controlling the concentration of Pb and Ni. The second correlation shows the role of clay minerals in controlling the concentration of the trace elements such as Fe and Zn. The plot of transformed scores of first canonical correlation for soil illustrate the high correlation between sets of variables as all points are grouped closely within an ellipsoidal field. The plot of transformed scores of first canonical correlation illustrate that there is a clear distinction between the type of sediments collected from Thane creek and the Ulhas river region.     

Stochastic models for the completeness of stratigraphic sections

Properties of stratigraphic completeness are determined here from a Brownian motion model of sediment accumulation. This avoids flaws inherent in application of a discrete-time random walk to the time span, rather than thickness, of sediment layers. Both discrete and continuous models show that the concept of stratigraphic completeness is meaningful only when the time scale is specified. From the discrete model, not surprisingly, completeness improves with increasing relative frequency and average thickness of depositional increments and the error of completeness estimation should decrease for longer sections. The continuous model shows that two dimensionless products determine the probability that a given time interval will be recorded by some preserved sediment. The first is the ratio of the age of the interval to its time span; the second is the product of the square root of the time span and ratio of the mean to the standard deviation of accumulation rate. Expected completeness is the average of these probabilities for all successive intervals of the given time span. For long sections, completeness may be estimated from the second dimensionless product alone. The two dimensionless products are sufficient to predict the relationship of accumulation rate to time span, the distribution of bed thickness, and the weak association of completeness and section thickness.     

Dreissena polymorpha (Bivalvia: Dreissenidae) in the Neva Estuary (eastern Gulf of Finland, Baltic Sea): is it a biofilter or source for pollution?

The zebra mussel Dreissena polymorpha, a ponto-caspian byssate bivalve, forms permanent dense populations along the shoreline in the northern part of the inner Neva Estuary. Its total biomass along a 17 km transect reached 4980 tons (mean 1060 g m(-2)) in 2000 and 6510 tons (mean 1385 g m(-2)) in 2001. Being persistent and abundant, the zebra mussel populations played an important role in benthic-pelagic coupling in inner Neva River Estuary. The D. polymorpha population released up to 514 kg day(-1) of dissolved inorganic phosphorus and was, therefore, a major source of bioavailable nutrients in the area. Mussel beds were also efficient biofilters and precipitate 15,020 kg day(-1) of particulate organic matter during the warm season. About 50% of precipitated matter had a relatively long retention time, being utilized within zebra mussel populations, while the rest was deposited as faeces and pseudofaeces and served as a source for organic pollution to the eastern Gulf of Finland.     

马海盐湖高含泥、低品位地表固体钾矿矿浆絮凝沉降试验研究

研究了非离子聚丙烯酰胺、阴离子聚丙烯酰胺、阳离子聚丙烯酰胺、聚氧化乙烯、聚合氯化铝等絮凝剂对马海盐湖泥湖高不溶物矿浆的絮凝沉降效果,给出了研究结果。此项研究对高不溶物可溶盐矿物母液的回收利用有一定的参考价值。     

Sedimentary processes on the Crimean continental margin in the Black Sea

Structural specific features of the sedimentary succession on the continental margin of the South Crimea in the Black Sea have been examined in the Yalta Area using geomorphologic, acoustic, and lithologic methods. Alternation of regressive and transgressive sequences has been ascertained in sediment sections formed on the shelf and in the Yalta deep-sea fan due to Quaternary oscillations of the basin level. The analysis of sediment sections resulted in revealing a leading role of sedimentary material transference from upper hypsometric levels to lower ones in the sediment accumulation.     

Quantifying sedimentation patterns of small landslide-dammed lakes in the central Oregon Coast Range

Understanding sedimentation patterns in small coastal watersheds due to landscape perturbations is critical for connecting hillslope and fluvial processes, in addition to managing aquatic habitats for anadromous fish and other aquatic species in the Oregon Coast Range (OCR). Changes in sedimentation patterns spanning the last 250 years are preserved in two landslide-dammed lakes in small watersheds (< 10 km²) underlain by the Tyee Formation in the central OCR. Dendrochronology of drowned Douglas-fir stumps in both lakes provided precise timing of the damming and formation of the lakes, with Klickitat Lake forming in winter ad 1751/52 and Wasson Lake in winter ad 1819/20. Perturbations from wildfires, logging and road development, and previously underappreciated snow events affect sedimentation rates in the lakes to different degrees, and are identified in the sediment record using cesium-137 (¹³⁷Cs), high-resolution charcoal stratigraphy, local fire records, and aerial photography. Each lake has variable sedimentation accumulation rates (0.05–4.4 cm yr⁻¹) and mass accumulation rates (0.02–1.42 g cm⁻² yr⁻¹). Sedimentation rates remained low from the landslide-damming events until the mid-19th century, when they increased following stand-replacing wildfires. Aside from a sediment remobilization triggered by human modification of the landslide dam at Klickitat Lake around 1960, the largest peaks in mass accumulation rates in the mid-20th century at both lakes in the early 1950s precede major road construction and logging activity in the watersheds. Subsequent sedimentation rates are lower, but variable, and possible effects of logging and road development might be exacerbated by abnormal precipitation and heavy snow events. A comparison of previous studies of landslide-dammed lakes in larger watershed of the OCR are consistent with our findings of increased sedimentation in the mid-20th century, as well as higher sedimentation rates in the debris-flow dominated southern Tyee Formation than in the lower-relief northern Tyee Formation.     

同构造沉积分析反演逆冲构造变形过程--燕山东段凌源南部中生代逆冲构造变形过程研究

介绍了同构造沉积分析的基本概念、研究思路、主要研究方法及其在区域构造变形过程研究中的重要作用。基于对辽西凌源南部区域构造变形、晚侏罗世土城子组同构造沉积粗碎屑沉积物成分变化规律的研究 ,获得如下主要认识 :( 1)同构造沉积始于髫髻山组火山活动之后 ;沉积物成分变化及古水动力特征表明 ,同构造沉积物源区主体位于盆地西侧褶皱隆起区 ,而不是来自南东方向的大型逆冲断层上盘的前渊沉积 ;而且显示了正常层序的物源区倾斜岩层的剥蚀和揭顶过程 ;当时的剥蚀作用已达中元古界蓟县系雾迷山组上部。 ( 2 )分布于郭家店盆地和邓杖子盆地之间的中元古界长城系地层“残片” ,与其东侧北票组间为向SEE逆冲的断层接触 ,而西侧与土城子组 (原邓杖子组 )之间为不整合接触 ;在老虎沟东南长城系地层“残片”不复存在的区域 ,土城子组不整合于北票组之上。该“残片”很可能是髫髻山组火山活动之前指向SEE的逆冲构造变形形成的飞来峰构造的残余部分。( 3 )凌源南部中生代逆冲构造变形可以区分为 :早侏罗世北票组之前 (印支期 )由北向南的逆冲作用、北票组之后髫髻山组之前向SEE的冲断推覆、髫髻山组之后的逆冲褶皱变形与同构造沉积作用以及九佛堂组之后局部的逆冲作用。指向SEE的主要逆冲作用以及伴生褶皱变形     

Lithologic Hydrocarbon Deposits in Rift Lake Basins in Eastern China

The rift lake basins in the eastern China have abundant hydrocarbon resources of lithologic deposits, which resulted from excellent source rocks and multi-type sandbodies developed during strong rifting. Vertically, the lithologic deposits are mainly distributed in the lowstand, lacustrine invasion and early highstand systems of third-order sequence corresponding to a secondary tectonic episode of strong rifting, and laterally they are closely related to various fans and turbidite sandbodies controlled by syn-sedimentary faults. A variety of lithologic traps have been developed in the rift lake basins, and they generally have favorable conditions of source-reservoir-seal assemblage and hydrocarbon accumulation dynamics, indicating that there is a great exploration potential of lithologic deposits in the rift lake basins. In order to obtain satisfactory effects of lithologic deposit exploration, it is required to combine new theories with advanced technical methods.