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Chen C.,Beijing Normal University | Chen C.,Chinese Research Academy of Environmental Sciences | Zheng B.,Chinese Research Academy of Environmental Sciences | Jiang X.,Chinese Research Academy of Environmental Sciences | And 5 more authors.
Journal of Environmental Sciences (China) | Year: 2013

Spatial distribution patterns of total mercury (THg) in 36 surficial sediment samples representing five regions of Lake Taihu were assessed using the ArcGis geostatistical analyst module. The pollution levels of THg were also evaluated from the same five lake regions. Concentrations of THg were in a ranged of 23-168 ng/g (mean 55 ng/g) in surfical sediments, which was significantly higher than those established baseline levels of the lake. Results of THg indicated that the northern region exhibited notably higher values, the bay regions showed elevated values relative to open areas, and the lakeside regions were higher than those observed in the central area. Lake Taihu suffered moderate to high Hg pollution, and expressed clear Hg enrichment status according to monomial pollution index Igeo and human activity factors. The concentrations of THg in the surficial sediments of Lake Taihu showed moderate-strong variation (coefficient of variation 52%). Geostatistical analysis indicated a weak spatial self-correlation, suggesting the contamination of Hg in Lake Taihu is primarily the result of anthropogenic activities. © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.

Xie J.,Hohai University | Xie J.,Shanghai Waterway Engineering Design and Consulting Co. | Yan Y.-X.,Hohai University
Journal of Hydrodynamics | Year: 2011

For the Hengsha East Shoal Promoting Siltation Project in the Yangtze River Estuary, this work developed a formula for calculating sediment carrying capacity based on variable coefficients and a mathematical model for suspended sedimentation using variable saturation recovery coefficients. Not only does the model yield good verification, preferably give the hydrodynamics and the sediment concentration, but also reach a good agreement between the simulation results and the measured topographical changes in the promoting siltation zone of the Hengsha East Shoal. Moreover, this article proposes a method for examing the net sediment transportation flux by tide for studying the effects of the project of promoting siltation and comparatively analyzes the current siltation of the Hengsha East Shoal and siltation mouth layouts, entrance widths, entrance bottom elevations, and the impact of the South Main Dike on promoting siltation through calculating the net sediment transportation flux by tide over the fixed bed and the direct movable bed numerical simulations. The results are in good agreement with each other, indicating that the method for calculating the net sediment transportation flux by the tide is also useful for assessing the project in promoting siltation. Finally, we use the modeling results to analyze the water and sediment diversion ratios and the changes in silting and scouring in riverbeds and draw the conclusion that the completion of the Hengsha East Shoal Promoting Siltation Project would not adversely affect the Yangtze River Estuary Deepwater Channel Project. © 2011 Publishing House for Journal of Hydrodynamics.

Guo Y.,Dalian University of Technology | Zhang J.-F.,Dalian University of Technology | Luan M.-T.,Dalian University of Technology | Liu G.-X.,Dalian University of Technology | Liu G.-X.,Shanghai Waterway Engineering Design and Consulting Co.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

By using the soil static and dynamic universal tri-axial and torsional shear apparatus, the stress-controlled undrained static torsional tests are performed on Dongying intact saturated silt of Shandong province and remolding saturated silt prepared by tamping method controlling three kinds of the initial sampling water contents. The conditions of the initial anisotropic consolidation are the initial mean principal stress of 100 kPa, the initial intermediate principal stress coefficient of 0.5, the initial deviator stress ratio 0.433 and the initial orientation angle of the principal stress respectively at 0°, 30°, 45°, 60°, 90°. During the undrained monotonic shearing process, the mean principal stress and the intermediate principal stress coefficient are fixed. The effects of orientation of the initial principal stress and initial sampling water content on the stress-strain relations, the pore pressure development as well as the effective stress paths are studied. The test results show that the effect degree of the initial principal stress orientation on deformation and strength behavior of intact silt is different from that of the remolding silt. The initial sampling water content has considerable influence on the test results of the saturated remolding silt.

Xia Y.-f.,Nanjing Hydraulic Research Institute | Xia Y.-f.,The State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering | Xu H.,Nanjing Hydraulic Research Institute | Xu H.,The State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering | And 5 more authors.
China Ocean Engineering | Year: 2011

In this paper, flume experiments are focused on sediment transport inside and outside the surf zone. According to the energy dissipation balance principle of sediment-laden flow and the similarity between energy dissipation of spilling breaking wave and hydraulic jump, formulas are proposed to predict time averaged suspended sediment concentration under both non-breaking and breaking waves. Assuming that the sediment diffusion coefficient, which is related with energy dissipation, is proportional to water depth, formulas are proposed to predict close-to-bed suspended sediment concentration and vertical distribution of suspended sediment under spilling breaking waves, and the prediction shows a good agreement with the measurement. © 2011 Chinese Ocean Engineering Society and Springer-Verlag Berlin Heidelberg.

Liu H.,East China Normal University | Liu H.,Shanghai Waterway Engineering Design and Consulting Co. | He Q.,East China Normal University | Weltje G.J.,Technical University of Delft | Chen J.,East China Normal University
Acta Geographica Sinica | Year: 2011

The suspended & surface sediments exchange processes under the high-turbidity and mixing estuarine environments were analyzed based on the grain size spectral calculation, to explore the rate and transport of suspended sediments in the Yangtze estuary-shelf systems. The results showed that: (1) approximately 47% of the sediments from the Yangtze River was accumulated in the mouth bar area and subaqueous delta, while the rest was transported to the Hangzhou Bay and southern Zhejiang and Fujian coasts. 122.5°-123°E was the important limits of the Yangtze suspended sediment diffusing eastward to the East China Sea. This method of grain size spectral calculation provided by this paper can be used for the study of quantitative calculation of sediment transport and deposition in other tidal environments. (2) Higher sediment exchange ratio (p > 0.6) occurred in the muddy area and Hangzhou Bay, and the ratio of the muddy areas outside the South Passage was higher than 0.9, which indicates that most suspended sediment contributed to the seabed evolution and sediment supply. On the decadal to centennial time scale associated with our results, a clearly defined depocenter of Yangtze sediment with the exchange rates greater than 2-3 cm/a is present in the muddy area and Hangzhou Bay. (3) Due to the impact of longshore currents and the Taiwan warm current, the suspended sediment from the Yangtze River deposited firstly in the muddy area, and then was transported to the inner Yangtze River Estuary, Hangzhou Bay and the south coasts by tidal current. Muddy area was the "sediment sink" of sediment processes in the estuary and moved southward. (4) Under the background of decrease in the Yangtze River sediment supply, the delta toward tidal flats was still deposited slowly, indicating that the sediments in the sediment sink made great contribution to the estuarine geomorphologic evolution.

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