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Linking Structural Equation Modeling with bayesian Network and Its Application to Coastal Phytoplankton Dynamics in the bohai bay

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China Ocean Engineering 2016年第5期30卷 733-748页

作者： XU Xiao-fu SUN Jian NIE Hong-tao YUAN De-kui TAO Jian-hua Tianjin bohai Sea Fisheries Research Institute Tianjin 300457 China Department of Hydraulic Engineering Tsinghua University Beijing 100084 China School of Marine Science and Technology Tianjin University Tianjin 300072 China Department of Mechanics Tianjin University Tianjin 300072 China

bayesian networks （BN） have many advantages over other methods in ecological modeling, and have become an increasingly popular modeling tool. However, BN are flawed in regard to building models based on inadequate existing knowledge. To overcome this limitation, we propose a new method that links BN with structural equation modeling （SEM）. In this method, SEM is used to improve the model structure for BN. This method was used to simulate coastal phytoplankton dynamics in the bohai bay. We demonstrate that this hybrid approach minimizes the need for expert elicitation, generates more reasonable structures for BN models, and increases the BN model＇s accuracy and reliability. These results suggest that the inclusion of SEM for testing and verifying the theoretical structure during the initial construction stage improves the effectiveness of BN models, especially for complex eco-environment systems. The results also demonstrate that in the bohai bay, while phytoplankton biomass has the greatest influence on phytoplankton dynamics, the impact of nutrients on phytoplankton dynamics is larger than the influence of the physical environment in summer. Furthermore, although the Redfield ratio indicates that phosphorus should be the primary nutrient limiting factor, our results show that silicate plays the most important role in regulating phytoplankton dynamics in the bohai bay.

关键词： structural equation modeling bayesian networks ecological modeling bohai bay phytoplankton dynamics

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Heavy metal pollution in tidal zones of bohai bay using the dated sediment cores

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Journal of Environmental Sciences 2006年第3期18卷 610-615页

作者： QIN Yan-wen MENG Wei ZHENG Bing-hui SU Yi-bin River and Coastal Environment Research Center Chinese Research Academy of Environmental Sciences Beijing 100012 China

Three sediment cores were collected in November 2003 from Dagu estuary to Qikou estuary. The main polluted heavy metals in the sediment of tidal zones for the bohai bay have been found by analyzing the relationship among the contents of heavy metals, the contents of geochemical elements （Fe, AI and Mn） and the size of grain. The dominating contaminative elements in tidal sediments of bohai bay are Pb, Zn and Cd. Their contents are higher than the corresponding upper limit of environmental background values and they have very faint correlation with the corresponding contents of geochemical elements and the size of grain, indicating the anthropogenic enrichment. Especially, the preliminary study on the pollution sources and the history of heavy metals in the Dagu estuary has been done using the dated results. The contamination by Zn and Cd also started in the middle 1950s, while the contamination by Pb appeared in the early 1940s. The pollution by Zn and Cd mainly originate from sewage discharge, while the pollution by Pb has many sources, like atmosphere deposition and industrial discharRe.

关键词： bohai bay tidal zone the dated sediment core heavy metal pollution

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Short-and long-term sediment transport in western bohai bay and coastal areas

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Chinese Journal of Oceanology and Limnology 2010年第3期28卷 583-592页

作者：冯桓张卫国贾丽 Michael P.WEINSTEIN 张秋丰袁德奎陶建华俞立中 Department of Earth and Environmental Studies Montclair State University State Key Laboratory of Estuarine and Coastal Research East China Normal University Institute for Sustainability Studies Montclair State University Marine Environmental Monitoring and Forecasting Center Department of Mechanics Tianjin University

Sediment cores （-40-100 cm） were collected at 12 locations in the western bohai bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be and ^210pb activities. Due to localized hydrodynamic patterns and frequent disturbance from dredging activities, steady-state sedimentation features were not observed in this study. As demonstrated in the VBe and ^210pb profiles, the temporal and spatial variations of these radionuclides support a non-steady state depositional environment in the study area. By comparing ^7Be and ^210pb inventories in the sediments with those of the atmospheric source, we found that： 1） sediments dredged from the Tianjin Harbor or eroded from nearby estuarine and coastal areas are retained in the western bohai bay for relatively short intervals （several months）, as reflected in the relatively high ^7Be inventories in the western bohai bay; 2） over the long-term （years to decades）, ^210Pb inventories in the sediments imply that there is a net on-shore transport of sediments, and the sediments are mass-balanced in the entire study area. Overall, our results suggest that the sediments are retained in the estuaries and the western bohai bay despite local variability in sediment dynamics and disturbance due to human activities.

关键词： bohai bay estuary sedimentation sediment transport radionuclide

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Geochemistry of Clayey Aquitard Pore Water as Archive of Paleo-Environment, Western bohai bay

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Journal of Earth Science 2015年第3期26卷 445-452页

作者： Jing Li Xing Liang Menggui Jin Guoqiang Xiao Jishan He Yandong Pei School of Environment Studies China University of Geosciences State Key Laboratory of Biogeology and Environmental Geology China University of Geosciences Tianjin Institute of Geology and Mineral Resources

The record of paleo-environment in clayey aquitard pore water is much more effective relative to aquifer groundwater owing to the low permeability of clayey aquitard. Oxygen-18（18O）, deuterium（D）, and chemical patterns were determined in pore water samples extracted from two 500 m depth boreholes, G1 and G2, in western bohai bay, China. Shallow pore water samples（depth〈102 m） are saline water, with the TDS（total dissolved solids） of 3.69–30.75 g/L, and deeper ones（depth=102–500 m） are fresh water, with the TDS〈1 g/L. Content of major ions（i.e., Cl-, Na＋, K＋, Mg2＋, SO2-4, Ca2＋） is high in marine sediment pore water samples and gradually decrease towards to terrestrial sediment pore water, together with the Cl/Br and Sr/Ba ratios changing significantly in different sedimentary facies along the study profile, indicating that pore water may be paleo-sedimentary water and not replaced by modern water. δ18O profile and positive correlation between δ18O and Cl- of shallow saline pore water indicated diffusion as the main transport mechanism, and distinguished four transgressive layers since Late Quaternary（i.e., Holocene marine unit, two Late Pleistocene marine units and Middle Pleistocene marine unit）, further supporting the finding that pore water retained the feature of paleo-sedimentary water. Climate was identified as the main influence on the isotopic signature of aquitard pore water and four climate periods were determined by δ18O profile.

关键词： aquitard pore water paleo-environment geochemistry bohai bay

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Evaluation of estimation methods for meiofaunal biomass from a meiofaunal survey in bohai bay

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Chinese Journal of Oceanology and Limnology 2010年第1期28卷 82-87页

作者：张青田王新华胡桂坤 College of Life Sciences Nankai University Tianjin Key Laboratory of Marine Resources and Chemistry Tianjin University of Science and Technology

Studies in the coastal area of bohai bay,China,from July 2006 to October 2007,suggest that the method of meiofaunal biomass estimation affected the meiofaunal *** estimation methods that use a unique mean individual weight value for nematodes to calculate total biomass may cause deviation of the results.A modified estimation method,named the Subsection Count Method (SCM),was also used to calculate meiofaunal *** entails only a slight increase in workload but generates results of greater *** gained using each of these two methods were compared in the present *** results show that the conventional method generally estimates a meiofaunal *** difference between the two estimation methods was highly significant (P<0.01) for the spring and winter ***,the estimation method for meiofaunal biomass affected the analysis of horizontal distribution and correlation with environmental *** findings highlight the importance of estimation methods for meiofaunal biomass and will hopefully stimulate further investigation and discussion of the topic.

关键词： meiofaunal biomass Subsection Count Method estimation method bohai bay China

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Numerical simulation of hydrodynamic and water quality effects of shoreline changes in bohai bay

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Frontiers of Earth Science 2018年第3期12卷 625-639页

作者： Han JIA 1Yongming SHEN Meirong SU Chunxue YU State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology Dalian 116024 China School of Environment and Civil Engineering Dongguan University of Technology Dongguan 523808 China

This study uses the HD and Ecolab modules of MIKE to simulate the hydrodynamic and water quality and predict the influence of shoreline changes in bohai bay, China. The study shows that shoreline changes weaken the residual current and generate a counter-clockwise circulation south of Huanghua Port, thereby resulting in weak water exchange capacity and low pollutant-diffusing capacity. Shoreline changes reduce the area of bohai bay, resulting in a smaller tidal prism and further weakening the water exchange capacity. This situation is not conducive to the diffusion of pollutants, and therefore may lead to increased water pollution in the bay. Shoreline changes hinder the spread of runoff, weaken the dilution effect of the river on seawater, and block the spread of coastal residual Current, thereby resulting in increased salinity near the reclamation area. Shoreline changes lead to an increase in PO4-P concentration and decrease in DIN concentration. The value of N/P near the project decreases, thereby weakening the phosphorus-limited effect.

关键词： bohai bay shoreline changes hydrodynamic water quality

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Field Observation and Analysis of Wave-Current-Sediment Movement in Caofeidian Sea Area in the bohai bay, China

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China Ocean Engineering 2014年第3期28卷 331-348页

作者：左利钦陆永军汪亚平刘怀湘 State Key Laboratory of Hydrology Water Resources and Hydraulic EngineeringNanjing Hydraulic Research Institute School of Geographic and Oceanographic Sciences Nanjing University

In order to study the mechanism of flow-sediment movement, it is essential to obtain measured data of water hydrodynamic and sediment concentration process with high spatial and temporal resolution in the bottom boundary layer （BBL）. Field observations were carried out in the northwest Caofeidian sea area in the bohai bay. Near 2 m isobath （under the lowest tidal level）, a tripod system was installed with AWAC （Acoustic Wave And Current）, ADCP （Acoustic Doppler Current Profilers）, OBS-3A （Optical Backscatter Point Sensor）, ADV （Acoustic Doppler Velocimeters）, etc. The accurate measurement of the bottom boundary layer during a single tidal period was carried out, together with a long-term sediment concentration measurement under different hydrological conditions. All the measured data were used to analyze the characteristics of wave-current-sediment movement and the BBL. Analysis was performed on flow structure, shear stress, roughness, eddy viscosity and other parameters of the BBL. Two major findings were made. Firstly, from the measured data, the three-layer distribution model of the velocity profiles and eddy viscosities in the wave-current BBL are proposed in the observed sea area; secondly, the sediment movement is related closely to wind-waves in the muddy coast area where sediment is clayey silt： 1） The observed suspended sediment concentration under light wind conditions is very low, with the peak value generally smaller than 0.1 kg/m^3 and the average value being 0.03 kg/m^3; 2） The sediment concentration increases continuously under the gales over 6-7 in Beaufort scale, under a sustained wind action. The measured peak sediment concentration at 0.4 m above the seabed is 0.15-0.32 kg/m^3, and the average sediment concentration during wind-wave action is 0.08-0.18 kg/m^3, which is about 3-6 times the value under light wind conditions. The critical wave height signaling remarkable changes of sediment concentration is 0.5 m. The results show that the suspended

关键词： field observation wave-induced sediment suspension wave-current interaction bottom boundary layer (BBL) Caofeidian bohai bay

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The Middle and Late Holocene climate change in bohai bay revealed by diatom proxy

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Journal of Oceanology and Limnology 2024年第5期42卷 1493-1506页

作者： Zhiwen SHANG Jianfen LI Fu WANG Hong WANG Tianjin Centre China Geological SurveyTianjin 300170China Key Laboratory of Coastal Geo-environment China Geological SurveyTianjin 300170China Tianjin Key Laboratory of Coast Geological Processes and Environmental Safety Tianjin 300170China

A total of 98 samples from two boreholes in shallow sea area and two oyster reefs in adjacent coastal plain in the northwestern coast of bohai bay were collected for diatom analyses and species *** ratio of the marine species Thalassionema nitzschioides to the intertidal-coastal species complex Cyclotella striata/stylorum serves as a novel proxy for assessing the strength of marine *** data,corrected for the local residence time effect,facilitated the construction of a diatom proxy-based marine influence curve for the study *** curve delineates the dynamics of marine influence and their correlations with paleo-climate fluctuations and the East Asian monsoon variability,as well as their role in chenier *** include:(1)eight periods of intensified marine influence have been documented since 7000 a BP in the study *** peak of each period,as determined by the diatom proxy,corresponds closely to the warm climatic phases and stronger East Asian summer monsoons,suggesting that the peaks marine influence indicate typically the periods of climatic warmth and monsoon activity intensification in the region;(2)a strong correlation exists between the development of cheniers and marine influence,and chenier formation began with the increasing marine influence and terminated at the end of warm periods as marine influence *** climatic changes in the coastal area,as indicated by the diatom proxy,hold significant potential for future related research endeavors.

关键词： bohai bay diatom diatom-based marine influence curve paleo-climate Holocene

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Reliability-Based Load and Resistance Factors Design for Offshore Jacket Platforms in the bohai bay:Calibration on Target Reliability Index

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China Ocean Engineering 2009年第3期23卷 15-26页

作者：金伟良胡琦忠沈照伟时忠民 Institute of Structural Engineering Zhejiang University Research Centre of China National Offshore Oil Corporation

The target reliability index has been effectively used as the best solution to deal with the relationship between the structural safety and the optimal economy in any structural design. However, the target reliability index for offshore jacket platforms based on different sea areas in China has never been calibrated. This paper presents an approach for its calibration, and suggests many kinds of associated load cases. The uncertainties of loads and structural resistance are mainly in- vestigated. The target reliability index for structural components, tubular joints and piles of offshore jacket plaffortns are discussed respectively in detail. Finally, through the calibrated results from the offshore jacket platforms of QK18-1, JZ20-2, SZ36-1 and BZ28-1 in the bohai bay, it is proposed to adopt 2.8 as the target reliability index of offshore jacket platforms in the bohai bay for a 25-year design period. The results provide significant reference for the design of offshore jacket platforms.

关键词： offshore jacket platform target reliability index calibration bohai bay

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Coastline changes and tidal current responses due to the large-scale reclamations in the bohai bay

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Journal of Oceanology and Limnology 2023年第6期41卷 2045-2059页

作者： Zhe HUANG Haijue XU Yuchuan BAI Fengshuo SHI Zhichao WEN State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300350China Institute for Sedimentation on River and Coastal Engineering Tianjin UniversityTianjin 300350China

China’s bohai bay has experienced large-scale land reclamation since *** reclamation projects create a nearshore ecological imbalance and shift sediment transport by changing the tidal ***,these tidal current changes are not comprehensively *** this paper,the coastline changes in bohai bay due to reclamation are investigated and the responses of the tidal current are calculated through numerical *** results show that the coastline length of the bay increases by more than 500 km from 2000 to 2015 with the largest reclamation rate of 150.9 km^(2)/***,the current velocity changes with an uneven distribution near the reclamation due to construction masking and dike *** tidal symmetry also changes in most nearshore areas,with opposite variations in the current velocity at peak flood and ebb *** addition,the tide direction deflects to bypass the reclamation and is usually consistent with the *** analysis of the dominant M2 tidal constituent shows that the range of the reciprocating current is widely *** total influence of the reclamation can reach the-8-m isobaths in bohai *** in the tidal current are the main causes of water environment ***,the arrangement and structural optimization of reclamation projects should be considered in the future.

关键词： bohai bay reclamation coastline tidal current

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