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Occurrence of Different Forms and Implications of Compound Specific Sterols in Continental Sediments of the Northeast South China Sea

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Acta Geologica Sinica(English Edition) 2019年第2期93卷 420-429页

作者： QIU Hong ZOU Li ZHANG Minsheng ZHU Chaoqi JIA Yonggang College of environmental Science and engineering Ocean University of China Education key laboratory fo r marine environment and Ecology Ocean University of China The Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of China

The South China Sea(SCS) is one of the most productive and accumulative marginal shelves of organic carbon in the world. To expound the transformation and preservation of organic carbon in the Northeast SCS, where abundant oil and gas resources have been reported, compound specific sterols in free(FR), base hydrolytic(BH), and acid hydrolytic(AH) forms were analyzed in surface and columnar sediments in May, 2016. The results showed that the total contents of sterols detected ranged from 0.15 to 3.74 ppm dry weight in the surface sediments, and gradually decreased from 3.41 to0.17 ppm dry weight from surface to deep sediments, in which cholesterol(27^(△5)) was the most abundant component. Sterols mainly existed in the BH form(54.51%-74.20%), followed by the FR form(25.50%-45.49%) and then the AH form(0-3.77%) in turn, in the surface sediments. BH and FR sterols accounted for 0-49.08% and 50.92%-100% in the columnar sediments, while AH sterols were undetectable. The contents of specific sterols indicated that, the primary source of marine organic carbon was about 5 times as much as that from terrestrial input. More and more FR sterols transformed into BH sterols with increasing sedimentary depth, and BH sterols absolutely dominated in sediment depths under 25 cm. The forms of Sterols C27 were maintained at a relative consistence state, but Sterols C28 to C30 degraded gradually during the sedimentation process. It was suggested that the stability of sterols, based on the chemical structures, might be the primary factor controlling their degradation and preservation in deeper sediments. These results would help to understand the organic carbon(OC) transformation in a hydrate formation area in a marginal sea.

关键词： sterols sediments occurrence forms transformation northeast South China Sea

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Experiment and analysis of the formation,expansion and dissipation of gasbag in fine sediments based on pore water pressure survey

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Acta Oceanologica Sinica 2022年第4期41卷 91-100页

作者： Shiyun Lei Xiujun Guo Haoru Tang College of environmental Science and engineering Ocean University of ChinaQingdao 266100China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China key Lab of marine environment and Ecology of Ministry of Education Ocean University of ChinaQingdao 266100China

Deep-seated gas in seabed sediments migrates upwards from effect of external factors,which easily accumulates to form gasbags at interface of shallow coarse-fine sediments.Real-time monitoring of this process is important to predict disaster.However,there is still a lack of effective monitoring methods,so we attempt to apply multi-points pore water pressure monitoring technology when simulating forming and dissipation of gasbags in sediments through laboratory experiment.This study focuses on discussion of sensitivity of pore water pressure monitoring data,as well as typical changing characteristics and mechanisms of excess pore water pressure corresponding to crack generation,gasbag formation and gas release.It was found that the value of excess pore water pressure in sediments is negatively correlated with vertical distance between sensors and gas source,and the evolution of gasbag forming and dissipation has a good corresponding relationship with the change of excess pore water pressure.Gasbag formation process is divided into three stages:transverse crack development,longitudinal cavity expansion,and oblique crack development.Formation of gasbag begins with the transverse crack at the interface of coarse-fine sediments while excess pore water pressure attenuates rapidly and then drops,pressure remains almost unchanged when cavity expanses longitudinally,oblique crack appeared in final stage of gasbag evolution while excess pore water pressure accumulated and dissipated again.The variation curve of excess pore water pressure in gas release stage has saw-tooth fluctuation characteristics,and the value and time of pressure accumulation are also fluctuating,indicating the uncertainty and non-uniqueness of gas migration channels in sediments.

关键词： pore water pressure monitoring technology excess pore water pressure gasbag cracks gas migration

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The profile of sound speed and dissolved oxygen in the polymetallic nodules depositional area in the Western Pacific

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Journal of Oceanology and Limnology 2023年第6期41卷 2090-2100页

作者： Bowen LI Yonggang JIA Zhihan FAN Kai LI College of Oceanography and Space Information China University of PetroleumQingdao 266580China laboratory for marine Geology Qingdao National Laboratory for Marine Science and TechnologyQingdao 266100China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China

With the consumption of terrestrial metal resources,the exploitation of deep-sea polymetallic nodule minerals has been widely concerned around the world.Therefore,the environmental impact of deep-sea polymetallic nodule mining cannot be ignored.However,duo to the lacks in stable and safe deep-sea(the depth>1000 m)vertical profile observation systems and consequently in long-term in-situ observation data,the sound speed and dissolved oxygen and the other water environment factors in the deposition areas of polymetallic nodules remains poorly understood.In this study,a deep-sea in-situ observation system was designed and deployed,and the water environment data of the polymetallic nodule deposition area were collected and analyzed.Result shows that the dissolved oxygen in the depth of 0–600 m was mainly affected by biological factors,while that in the area deeper than 600 m was affected by physical factors.The sound speed in the water body was mainly affected by temperature and pressure.At depths below 840 m,the sound speed is mainly controlled by temperature,and at depths between 840 m and 5700 m,the sound speed is mainly controlled by pressure.The correlations of sound speed vs.pressure and vs.temperature were regressed into equation.The resuspension of sediments rich in various metals may result in the reduction of dissolved oxygen and the improvement of redox potential.This environmental impact caused by a single sediment resuspension could last for 24 h or more.These findings enrich the understanding of the background value of the water environment in the polymetallic nodule deposition area.

关键词： deep sea dissolved oxygen redox potential sound speed conductivity

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Dynamics of Bottom Boundary Layers in the Yellow River Subaqueous Delta Based on Long-Term In-Situ Observations

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Acta Geologica Sinica(English Edition) 2017年第1期91卷 369-370页

作者： ZHU Chaoqi JIA Yonggang WANG Zhenhao GUO Lei SHAN Hongxian LIU Xiaolei ZHANG Minsheng Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering (Ocean University of China) Qingdao 266100 Shandong China laboratory for marine Geology Qingdao National Laboratory for Marine Science and Technology Qingdao 266061Shandong China

Objective In geo-marine science,the generalized bottom boundary layer（BBL）represents a layer between sediments and seawater.The BBL plays an important role in geological,geobiochemical,geophysical and geotechnical r... 详细信息

关键词： Dynamics of Bottom Boundary Layers in the Yellow River Subaqueous Delta Based on Long-Term In-Situ Observations

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Experimental Researches on the Accuracy of Micro- Electromechanical Accelerometer-Array in Seafloor Failure Deformation Measurement

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Journal of Ocean University of China 2022年第5期21卷 1198-1204页

作者： WANG Zhenhao LIU Xiaolei ZHANG Shaotong WEN Mingzheng SHAN Hongxian JIA Yonggang First Institute of Oceanography Ministry of Natural ResourcesQingdao 266061China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China laboratory for marine Geology Qingdao National Laboratory for Marine Science and TechnologyQingdao 266061China Tianjin Center China Geological SurveyTianjin 300170China

At present,there are few technologies applied to in situ observation of seabed deformation,among which the micro-electromechanical accelerometer-array(hereinafter referred to as accelerometers array)is a very advantageous measurement method,with both commercial products and successful application cases.However,the coupling effect between accelerometer-array and sur-rounding soil and the linkage effect of accelerometer-array itself during the deformation may influence the accuracy and reliability of the measurement data.A simulation test chamber was designed and processed,and four groups of simulation tests were carried out to explore the coupling effect and linkage effect of accelerometer-array in the soil with different degree of consolidation.The results show that the accelerometer-array and the soil coupled well,and the coupling effect is positively correlated with the degree of soil consoli-dation.The ratio of accumulative deviation to soil lateral deformation is high at the initial stage of deformation(0-50 mm)and reduced with the continuous increase of deformation(>100 mm).In the process of liquefied soil deformation,the linkage effect of accelerometer array can be ignored,and is negatively correlated with the degree of soil consolidation.A concept to improve the measurement accu-racy of accelerometer-array in different seafloor failure deformation modes is proposed.The research results provide references for the modification of accelerometer-array and the improvement for other flexible rod-shaped deformation sensors.

关键词： micro-electromechanical accelerometer-array seafloor failure deformation in situ observation coupling effect linkage effect

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marine Geohazards： Review and Future Perspective

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Acta Geologica Sinica(English Edition) 2016年第4期90卷 1455-1470页

作者： JIA Yonggang ZHU Chaoqi LIU Liping WANG Dong Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering (Ocean University of China) Qingdao Shandong 266100 China laboratory for marine Geology Qingdao National Laboratory for Marine Science and Technology Qingdao Shandong 266061 China key laboratory of marine environment and Ecology Ministry of Education Ocean University of China Qingdao Shandong 266100 China

With offshore resource exploration moving to the deep water, marine geohazards have been attracting attention from the academic and industry. Research achievements of marine geohazards were reviewed in this paper. We analyzed and discussed typical issues among marine geohazards, including coastal erosion, submarine slope failure, turbidity current and special hazards induced by gas hydrate dissociation, in terms of their definition, distribution, characteristics and case studies. Major international projects on marine geohazards headed by the United States, Europe, Japan and other international organizations are introduced as well. Three marine geohazard survey methods, including geophysical survey, geotechnical exploration and in-situ observation, were summarized with a brief description of each approach, respectively. Especially, the history of marine geohazard researches in China is briefly reviewed, showing the disparity between China and developed countries in the study of marine geohazards narrows gradually. The potential research tendency in future was suggested.

关键词： marine geohazards submarine landslide gas hydrate coastal erosion in-situ observation

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Stress Path Analysis of Deep-Sea Sediments Under the Compression-Shear Coupling Load of Crawler Collectors

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Journal of Ocean University of China 2023年第1期22卷 65-74页

作者： ZHANG Ning MA Ning YIN Shiyang CHEN Xuguang SONG Yuheng School of Water Resources and Hydropower engineering North China Electric Power UniversityBeijing 102206China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China laboratory for marine Geology Qingdao National Laboratory for Maine Science and TechnologyQingdao 266100China

The mechanical properties of deep-sea sediments during the driving process of crawler collectors are essential factors in the design of mining systems.In this study,a crawler load is divided into a normal compression load and a horizontal shear load.Then,the internal stress state of sedimentary soil is examined through a theoretical calculation and finite element numerical simulation.Finally,the driving of crawlers is simulated by changing the relative spatial position between the load and stress unit,obtaining the stress path of the soil unit.Based on the calculation results,the effect of the horizontal shear load on the soil stress response is analyzed at different depths,and the spatial variation law of the soil stress path is examined.The results demonstrate that the horizontal shear load has a significant effect on the rotation of the principal stress,and the reverse rotation of the principal stress axis becomes obvious with the increase in the burial depth.The stress path curve of the soil is different at various depths.The spatial variation rule of the stress path of the shallow soil is complex,whereas the stress path curve of the deep soil tends to shrink as the depth increases.The stress path of the corresponding depth should be selected according to the actual research purpose and applied to the laboratory test.

关键词： deep-sea sediment crawler collector compression-shear coupling load stress path principal stress axis direction

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Spatial and temporal variation process of seabed dynamic response induced by the internal solitary wave

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Acta Oceanologica Sinica 2023年第2期42卷 142-149页

作者： Zhuangcai Tian Lei Jia Naili Hu Susheng Wang Mingwei Zhang Guoqing Zhou State key laboratory for Geomechanics and Deep Underground engineering China University of Mining and TechnologyXuzhou221116China key laboratory of Coastal Science and Integrated Management Ministry of Natural ResourcesQingdao266061China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao266100China

Internal solitary wave(ISW)is often accompanied by huge energy transport,which will change the pore water pressure in the seabed.Based on the two-dimensional Biot consolidation theory,the excess pore water pressure in seabed was simulated,and the spatiotemporal distribution characteristics of excess pore water pressure was studied.As the parameters of both ISW and seabed can affect the excess pore water pressure,the distribution of pore water pressure showed both dissipation and phase lag.And parametric studies were done on these two phenomena.Due to influenced by the phase lag of excess pore water pressure,the penetration depth under the site of northern South China Sea with total water depth 327 m,induced by typical internal solitary wave increased by 26.19%,53.27%and 149.86%from T_(0)to T_(0.5)in sand silt,clayey silt and fine sand seabed,respectively.That means the effect of ISW on seabed will be underestimated if we only take into accout the penetration depth under ISW trough,especially for fine sand seabed.In addition,the concept of“amplitude-depth ratio”had been introduced to describe the influence of ISW on seabed dynamic response in the actual marine environment.In present study,it is negatively correlated with the excess pore water pressure,and an ISW with smaller amplitude-depth ratio can wide the range of lateral impacts.Our study results help understand the seabed damage induced by the interaction between ISW and seabed.

关键词： internal solitary wave pore water pressure seabed dynamic response variation process

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Impact of seepage flow on sediment resuspension by internal solitary waves:parameterization and mechanism

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Journal of Oceanology and Limnology 2023年第2期41卷 444-457页

作者： Zhuangcai TIAN Chao LIU Ziyin REN Xiujun GUO Mingwei ZHANG Xiuhai WANG Lei SONG Yonggang JIA State key laboratory for Geomechanics and Deep Underground engineering China University of Mining and TechnologyXuzhou 221116China key laboratory of Coastal Science and Integrated Management Ministry of Natural ResourcesQingdao 266061China Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China

Sediment incipient motion is the first step in sediment resuspension.Previous studies ignored the effect of seepage flow on the mobility of sediment particles and simplified the seabed surface as a rigid boundary.A flume experiment was designed to innovatively divide the seabed into two parts to control the dynamic response of the seabed and control the seepage conditions.In the experiment,the seabed sediments and the amplitude of internal solitary waves(ISWs)were changed to compare and analyze the impact of seepage flow on the sediment resuspension by shoaling ISWs.Moreover,parametric research and verification were carried out.Results indicate that seepage flow can greatly influence fine sand,promote sediment resuspension,and increase the amount of suspension by two times on average.However,seepage flow had a little effect on the suspension of clayey silt and sandy silt.Besides,seepage force was added to the traditional gravity,drag force,and uplift force,and the parameterization of threshold starting shear stress of coarse-grained sediments was developed.The results of this parameterization were verified,and seepage force was critical to parameterization.The threshold starting shear stress was reduced by 54.6%after increasing the seepage force.The physical mechanism of this process corresponded to the vertical reciprocating transient seepage in and out the seabed interface caused by the wave-induced transient excess pore water pressure.This quantitative study on seepage flow for shear stress of coarse-grained sediments induced by ISWs is critical to geohazard assessment.

关键词： internal waves seepage flow sediment resuspension parameterization mechanism

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Microstructure Characterization of Bubbles in Gassy Soil Based on the Fractal Theory

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Journal of Ocean University of China 2024年第1期23卷 129-137页

作者： WU Chen LIN Guoqing LIU Lele LIU Tao LI Chengfeng GUO Zhenqi Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering Ocean University of ChinaQingdao 266100China key laboratory of Gas Hydrate Ministry of Natural ResourcesQingdao Institute of Marine GeologyQingdao 266237China College of environmental Science and engineering Ocean University of ChinaQingdao 266100China key laboratory of marine environment and Ecology Ministry of EducationOcean University of ChinaQingdao 266100China Qingdao National laboratory for marine Science and Technology Qingdao 266237China

The microscopic characterization of isolated bubbles in gassy soil plays an important role in the macroscopic physical properties of sediments and is a key factor in the study of geological hazards in gas-bearing strata.Based on the box-counting method and the pore fractal features in porous media,a fractal model of bubble microstructure parameters in gassy soil under different gas con-tents and vertical load conditions is established by using an industrial X-ray CT scanning system.The results show that the fractal di-mension of bubbles in the sample is correlated with the volume fraction of bubbles,and it is also restricted by the vertical load.The three-dimensional fractal dimension of the sample is about 1 larger than the average two-dimensional fractal dimension of all the slices from the same sample.The uniform porous media fractal model is used to test the equivalent diameter,and the results show that the variation of the measured pore diameter ratio is jointly restricted by the volume fraction and the vertical load.In addition,the measured self-similarity interval of the bubble area distribution is tested by the porous media fractal capillary bundle model,and the fitting curve of measured pore area ratio in a small loading range is obtained in this paper.

关键词： gassy soil bubble microstructure parameters fractal dimension vertical load

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