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A study on textural characteristics,heavy mineral distribution and grain-microtextures of recent sediment in the coastal area between the Sarada and Gosthani rivers,east coast of India

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International Journal of sediment Research 2020年第5期35卷 484-503页

作者： Ali Mohammad Parvathaneni Bhanu Murthy Edupuganti Naga Dhanamjaya Rao Hari Prasad Department of Geology Andhra University

The current study aimed to describe textural characteristics,heavy mineral composition,and grain microtextures of the sediment from three micro-environments(foreshore,berm,and dune).A total of forty-one(41) representative surficial sediment samples have been collected from fifteen(15) locations along the beach area between the Sarada and Gosthani rivers on the east coast of India,where the length of the stretch is more than 100 *** study reveals that most of the coastal sediment is medium to fine sand with relatively high ratios of coarse sand at Yarada beach,and the nature of the sediment is moderately to well *** characteristics indicate a high energy *** heavy mineral analysis of the sediment in the current study was done for coarse(+60#) and fine(+230#) size *** the weight percentage(WT%) reveals that a high percentage of heavy minerals is associated with fine ***,sillimanite,garnet,zircon,and rutile are the major heavy minerals identified in the current *** concentrations of these heavy minerals show great variations from south to north of the study *** an economic point of view,a considerable amount of heavy minerals(average 48.41%) are present on both sides(north and south) of the Gosthani River *** the Sarada Estuary,the concentration of the economic heavy minerals was found under the minimum economic *** grain microtextures of the major heavy minerals from the different locations along the study area demonstrate the variation in grain microtextures,which is controlled by the chemical and mechanical *** microtextures reflect moderate to high wave energy on the beach area,in addition to high mechanical impact on the grains from the estuary point.

关键词： Textural characteristics Heavy minerals Grain microtexture coastal sediment Visakhapatnam Coast

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Characterization and seasonal distribution of microplastics in the nearshore sediments of the south-east coast of India,Bay of Bengal

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Frontiers of Environmental Science & Engineering 2022年第1期16卷 129-139页

作者： K.Dhineka M.Sambandam S.K.Sivadas T.Kaviarasan Umakanta Pradhan Mehmuna Begum Pravakar Mishra M.V.Ramana Murthy National Centre for coastal Research(NCCR) Ministry of Earth Science(MoES)Chennai 600100India*

In view of increasing Microplastics(MPs)contamination in the marine environment and dearth of baseline data,a study was conducted on the abundance,characterization,and seasonal distribution of MPs in the nearshore sediments of the south-east coast of *** samples(n=130)were collected at a distance of 1 km and 10 km from the shore region at varying depths(8–45 m)along the Chennai to Puducherry coast(165 km stretch),representing two seasons,i.e.,south-west(July 2019 and July 2020)and north-east(January 2020)*** average abundance of MPs at the 22 offshore sites along the Chennai to Puducherry coast varied from 9±4.3 to 19±12.9 particles/50 g dry weight,in July 2019 and January 2020,*** 2020 had an average abundance of 10±4.5 particles/50 g dry ***,high levels of MPs were found at 1km stations and transects in proximity to the river inlets,and temporally,the north-east month recorded the maximum *** dominant morphotype was the filament,and the major polymers were polyethylene and *** Electron Microscope(SEM)images revealed the surface irregularity and degradation of MPs due to *** study highlights that high sediment contamination by MPs occurs during heavy rainfall and accumulates closer to river ***,this study suggests that appropriate management of plastic wastes on the landside will reduce MP contamination in the marine environment.

关键词： Microplastics coastal sediment Characterization Bay of Bengal India

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Growth patterns and dynamics of mud cracks at different diagenetic stages and its geological significance

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International Journal of sediment Research 2014年第1期29卷 82-98页

作者： Zhen-yu ZHAO Yan-ru GUO Yan WANG Hong LIU Qing ZHANG Research Institute of Petroleum Exploration and Development Research Institute of Petroleum Exploration & Development of Changqing Oilfield

This paper discusses the growth stages,spatial structures,quantitative fitting relationships among various parameters,growth patterns and influencing factors of mud cracks by field survey,core observation and SEM *** study shows that:(1) Mud crack growth can go through three stages,*** syndiagenetic stage,the burial diagenetic stage(including early diagenetic stage,middle-late diagenetic stage) and the epidiagenetic stage.(2) Quantitative fitting relationships among various parameters allow a great significance to describe the spatial structure,the regional distribution and the growth environment of mud cracks.(3) Mud crack growth has three models,such as the unilateral growth model including the linear growth pattern,the curvilinear growth pattern and the bifurcation growth pattern,the multilateral growth model including the inteisectional growth pattern,the join growth pattern and the dispersed growth pattern,and the mixed growth model including the combination of any patterns listed above.(4) Modern mud crack growth usually undergoes four *** beds in sand-mud rhythmic strata can play a lubricative role on crack growth and provide enough sandy deposits for filling cracks.(5) Mud crack growth usually produces bifurcation and bifurcation angles which are mostly 120° or 90° that are related to sediment heterogeneity and released energy.(6)Factors affecting mud crack growth cover many aspects:clay content and salinity can control the number of mud cracks in different areas;terrain can control mud crack morphology;and different sedimentary cycles can control the growth patterns and filling models of mud cracks.

关键词： Mud crack Growth pattern Geological model Lagoon coastal sediment

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Diverse Asgard archaea including the novel phylum Gerdarchaeota participate in organic matter degradation

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Science China(Life Sciences) 2020年第6期63卷 886-897页

作者： Mingwei Cai Yang Liu Xiuran Yin Zhichao Zhou Michael WFriedrich Tim Richter Heitmann Rolf Nimzyk Ajinkya Kulkarni Xiaowen Wang Wenjin Li Jie Pan Yuchun Yang Ji-Dong Gu Meng Li Shenzhen Key Laboratory of Marine Microbiome Engineering Institute for Advanced StudyShenzhen UniversityShenzhen 518060China Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province College of Optoelectronic EngineeringShenzhen UniversityShenzhen 518060China Microbial Ecophysiology Group Faculty of Biology/ChemistryUniversity of BremenBremen D-28359Germany MARUM Center for Marine Environmental SciencesUniversity of BremenBremen D-28359Germany Laboratory of Environmental Microbiology and Toxicology School of Biological SciencesThe University of Hong KongHong Kong 99077 China Department of Microbe-Plant Interactions Faculty of Biology/ChemistryUniversity of BremenBremen D-28359Giermany

Asgard is an archaeal superphylum that might hold the key to understand the origin of eukaryotes, but its diversity and ecological roles remain poorly understood. Here, we reconstructed 15 metagenomic-assembled genomes from coastal sediments covering most known Asgard archaea and a novel group, which is proposed as a new Asgard phylum named as the "Gerdarchaeota".Genomic analyses predict that Gerdarchaeota are facultative anaerobes in utilizing both organic and inorganic carbon. Unlike their closest relatives Heimdallarchaeota, Gerdarchaeota have genes encoding for cellulase and enzymes involved in the tetrahydromethanopterin-based Wood–Ljungdahl pathway. Transcriptomics showed that most of our identified Asgard archaea are capable of degrading organic matter, including peptides, amino acids and fatty acids, occupying ecological niches in different depths of layers of the sediments. Overall, this study broadens the diversity of the mysterious Asgard archaea and provides evidence for their ecological roles in coastal sediments.

关键词： Asgard archaea Gerdarchaeota coastal sediment metagenome metatranscriptome

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INITIATION OF SHELL MOTION ON SAND BEDS: AN EXPERIMENTAL STUDY

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International Journal of sediment Research 2002年第4期17卷 286-297页

作者： Subhasish DEY,Alok KUMAR Department of Civil Engineering Indian Institute of Technology Department of Civil Engineering Indian Institute of Technology Associate ProfessorKharagpur 721302 WestBengal India.Fax:+*** Student Kharagpur 721302 West Bengal India

Experimental study on initiation of bivalve shell motion on a horizontal sand bed, under a unidirectional flow of water, is presented. Experiments were carried out in a flume with three types of bivalve shells, namely Coquina Clam, Cross-barred Chione and Ponderous Ark, to test the condition for initiation of motion. The shape parameters of bivalve shells are defined appropriately. Experiments were conducted in a flume with a horizontal bed, and the critical shear stresses were estimated using Vanoni's side-wall correction. The characteristic parameters affecting the initiation of shell motion on a horizontal bed in rough-turbulent regime identified based on the physical reasoning and dimensional analysis are the Shields parameter (nondimensional critical shear stress), nondimensional competent mean velocity, nondimensional sand roughness, nondimensional flow depth and shape parameter. Equations of Shields parameter and nondimensional competent mean velocity for the initial movement of shells on a horizontal sand bed with convex upward and downward conditions are obtained using experimental data.

关键词： Bivalve shells Incipient motion sediment transport coastal sediment Hydrodynamics Threshold motion

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Geology and Geochemistry of Recent sediments from the Mediterranean Sea:sediment Texture of Northeastern Mediterranean Basin

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Open Journal of Geology 2013年第6期3卷 371-378页

作者： Semal Yemenicioglu Sakir Cagan Tunc Institute of Marine Sciences Middle East Technical University(METU)MersinTurkey Geomarine Kara ve Deniz Arastirmalari MersinTurkey

Surface sediment samples collected from the north-eastern Mediterranean were analysed for their geochemical and sedimentological properties. The sediment texture of the studied area represents a wide variety of sediment types (extending from sandy gravel to mud) and is characterized by relatively high mud content with varying silt and clay fractions. Due to the rich presence of biogenic materials, several coarse-grained sediment patches displaying high CaCO3 content occur. The organic carbon content of the sediments mainly reflects the standard Mediterranean production of organic matter. There are some exceptional areas in coastal zones which result from pollution by perennial river discharge.

关键词： Geochemistry coastal sediment Grain Size Carbonate Organic Carbon North-Eastern Mediterranean

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