Sortable Silt Variations on the Continental Slope of Campos Basin (Sw Atlantic): Implications in the Oceanographic Processes
Cíntia YamashitaGustavo Oliveira BritoRafaela Nogueira Mendonça MendesAna Cláudia Aoki SantarosaBruno Vanderlinde DamasioBeatriz DiasFabiane Sayuri IwaiThaisa Marques VicenteNancy Kazumi TaniguchiIsabel Montoya-MontesMichel Michaelovitch de MahiquesSilvia Helena de Mello e Sousa
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An indirect way to measure the speed of bottom currents may be using granulometric parameters such as the proxy sortable silt (). This proxy is associated with the sedimentation process and can estimate paleocurrents. This study aims to evaluate the range of the near-bottom current flow speed through the and related to oceanographic processes in the southeastern Brazilian continental slope. The values ranged from 17.08 to 26.23 µm, presenting a mean value of 19.87 µm. The flow speed values were obtained through Ledbetter's (1986) and Miller's (1977) formulas, varying from a minimum of 0.07 and 0.21 m s-1 to a maximum of 0.26 and 0.24 m s-1. The changes in bottom velocities observed in the Campos Basin are influenced by geomorphologic and hydrodynamic parameters, namely the off-shelf export of the sediment; the action currents (Brazil Current, Intermediate Western Boundary Current, and the Deep Western Boundary Current); and the geomorphological characteristics (island, ravine, and halokinesis movement).Keywords:
Silt
The study pertains to available water holding capacity of the 13 soil textural classes, ranging from sand to clay, occurring in the left and right ayacuts of Hirakud Command Area, Orissa. Texture, organic matter (OC) and bulk density (BD) were found to influence the water holding capacity, predictable from the equation, Y = 8.598+0.129 (silt+clay)+3.241(OC-4.678 (BD) with R2=0.93. Available water holding capacity though, in general, was significantly correlated with silt plus clay fraction, within the textural groups it was still more closely related to silt plus clay in coarse and moderately coarse textured soils, to silt in medium textured, and to the proportion of silt to clay in fine textured ones. Water retention was largely influenced by the nature of dominant clay mineral.
Silt
Soil texture
Water-Holding Capacity
Texture (cosmology)
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The minerals of the silt of the end of Three Gorges reservoir of Yangtze River were studied. Through the spectral analysis of the samples, the analysis of chemistry components and the content mensuration of main minerals, chemistry components and composition of the main minerals have been tested. The results show that: the silt of Three Gorges of Yangtze River in Chongqing is mainly composed of silicolites and quartz, containing Fe and Ti in small quantity and Yt, Yb and Sc in minim quantity. Main mineral in the silt contain Sc, and average content of Sc in the silt is 6.6g/t. Manufacture of building materials can be made of the trailing and lixiviation dreg by separating Sc from the silt. The silt may be utilized synthetically.
Silt
Yangtze river
Three gorges
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Weishan irrigation region is a large irrigated area of the lower reaches of the Yellow River which diverts water from the Yellow River. The silt deposit in the canals becomes so serious that it is difficult to deal with. In order to reduce the silt of the canals, some technological measures are taken, such as long-distance transporting the silt, disposing of the silt centralizedly, scattering the silt, reducing the silt by water saving and so on. Some good results have been achived by comprehensive utilization of the silt produced by disposing of the silt in the canals.
Silt
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Through analysis of the SEM experiment on the retem pering silt with di fferent clay contents and at different times, the writer introduces the variatio n law of silt's micro structure and the relationship between silt's micro stru ct ure and it's anti liquefaction. Through analyzing the silt's micro photo, the wr iter draws the conclusion that the micro structural characteristics of the silt with natural grains of clay varies when it's clay contents amount to Pc=9%, which is one of the turning points where the silt's characteristics change.
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A qualitative analysis is made on the dredged silt from Guangzhou,and then the examination results and the relevant impact factors are experimentally studied and discussed for the examination of the pH value of the solidified silt.The result shows that the dredged silt and its solidified silt should belong to soil,and different procedures and methods for the examination of the pH value have great impacts on the results concerned,therefore,and the actual examination must be made with the appropriately selected procedures and methods.
Silt
Value (mathematics)
Soil test
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In order to utilize the Yellow River sediments,silt is characterized by instruments for silt properties. The silt in the lower reaches of the Yellow River is also solidified using a hydrothermal processing method,and investigated the effect of addition content on flexural strength of solidified bodies and its hardening mechanism.The analytical results show that the particle size,chemical and mineralogical compositions of the silt in the upper,middle and lower reaches of the Yellow River are almost the same and the amount of heavy metals dissolved from the silt is below the regulatory levels for the environmental quality standards for soils of China.The flexural strength of solidified samples reaches 17MPa.The strength development is shown to depend on the formation of tobermorite,and the more the tobermorite,the higher the strength.
Silt
Tobermorite
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The overyear average amount of silt deposit in Dongting Lake is as high as 13×10~7 t, Long-term silt deposit contribute to special ecological environment. The special circumstance and destructive activities of people accelerated the speed of silt deposit broke the balance of ecological system, and formed secondary disastrous environment. Subsquently, the abnormal change of environment amplified the impact of silt deposit, result in the format and cocurrence of disasfrous chains in the final analysis, the gradual formation process of disastrous chains all originated from the long-term silt deposit.
Silt
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Silt
Settling
Granulometry
Deposition
Particle (ecology)
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In order to determine if there is any physiographic preference for sedimentary organic matter preservation, two gravity cores were collected off Gampo, East Sea: one from continental shelf and the other from continental slope. Concentrations of porewater nutrients and total were all higher in the continental shelf station, St. A, than the continental slope station, St. B. Meanwhile, concentrations of porewater sulfate decreased more rapidly at St. A than at St. B. Sedimentary organic carbon and nitrogen contents were lower and decreased more rapidly at St. A than at St. B. These data characters of porewater chemistry and sedimentary organic matter suggest that the organic matter is more actively decomposed at St. A than at St. B. At least over the study area, therefore, the sedimentary organic matter in the continental slope appears to be better preserved than that in the continental shelf.
Continental Margin
Sedimentary organic matter
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