Sediment-rejection mechanisms of 42 species of Australian scleractinian corals

1992 ◽  
Vol 43 (4) ◽  
pp. 683 ◽  
Author(s):  
MG Stafford-Smith ◽  
RFG Ormond
Keyword(s):  
Tissue Expansion ◽  
Fine Sand ◽  
Coarse Sand ◽  
Energy Budgets ◽  
Sediment Size ◽  
Sediment Loads ◽  
Organic Sediment ◽  
Acropora Hyacinthus ◽  
Neutrally Buoyant

Mechanisms of sediment rejection by 42 species of Scleractinia from 31 genera, all with wide Indo-Pacific distributions, were investigated in situ and in the laboratory at Lizard Island, northern Great Barrier Reef. Rejection mechanisms of flat tissues (generally six replicates plus controls) were studied in response to a single rapid influx of 50 mg cm-2 of 70/30% calcium carbonate/quartz sediment of each of four particle sizes: silt (<63 pm), fine sand (63-250 μm), coarse sand (500 μrn to 1 mm), and granules (1-3 mm). Additional observations were made of responses to variations in sediment loads (to a maximum of 1000 mg cm-2) , to individual sediment particles, and to less-dense organic sediment and food, as well as of the effects of tissue angles, colony morphology, and in situ environmental conditions. Ciliary currents, tissue expansion, and mucus entanglement occur in all of the species studied. Direct tentacle manipulation and pulsed partial contraction of the polyp or coenosarc also occur but were not observed in all species. Mesenteries may play a subsidiary or incidental role. Active-rejection mechanisms are consistent within species and, with the principal exception of some Faviidae species, are similar for the congeneric species studied. Species are categorized according to their observed active-rejection capability. This capability is positively correlated with calice size: all species with large calices (> 10 mm in diameter) are capable of rejecting influxes of up to at least 50 mg cm-2 of the tested sediment sizes with comparative ease; those species with small calices (<2.5 mm in diameter), particularly the two Porites species and the three Montipora species, are poor active rejectors; and other species, notably Acropora hyacinthus and Pocillopora darnicornis, though having some active-rejection capability, exhibit morphologies that make active rejection mostly redundant. Species with calices between 2.5 and 10 mm in diameter show more variation, but all very active rejectors in this size class have strong ciliary mechanisms. There are differences in the area of a colony involved in the rejection of sediment influxes, depending on sediment size and density. Rejection of heavy influxes of all sediment sizes is principally restricted to flat or concave surfaces, whereas individual particles of silt and fine sand as well as light influxes of silt and almost neutrally buoyant particles of larger sizes frequently require active rejection from strongly inclined, and even near-vertical, surfaces. The significance of these findings in terms of energy budgets is discussed.

scholarly journals Formation and remediation simulation of an in-situ reactive zone with nanoiron for a nitrobenzene-contaminated aquifer

2018 ◽  
Vol 18 (6) ◽  
pp. 2071-2080
Author(s):  
Li Hui ◽  
Zhang Xue-qing
Keyword(s):  
Fine Sand ◽  
Coarse Sand ◽  
Water Yield ◽  
Permeability Change ◽  
Contaminated Aquifer ◽  
Permeability Constant ◽  
Sand Box ◽  
Reactive Zone ◽  
The Media

Abstract A two-dimensional simulated sand box was built to investigate the formation and remediation of an in-situ reactive zone (IRZ) of nanoscale zero-valent iron (NZVI) for a nitrobenzene-contaminated aquifer, and the permeability change of the zone was calculated through the loss of waterhead. The experimental results demonstrated that the remediation area in coarse sand was obviously larger than that in fine sand. The nitrobenzene concentration reached a stable level of 87.24 and 170.24 mg/L in coarse and fine sand by 50 d and 40 d, respectively; after 60 d, the concentration of aniline as the reduction end-product of nitrobenzene was 97.02 and 49.40 mg/L, corresponding to a mean production rate of 40.1% and 20.8%, respectively. This indicated that a wider zone will be formed in the media with a larger size, which is beneficial for pollution remediation. The water yield of the aquifer declined by 13.8% and 11.9% in coarse and fine sand after 60 d, and the final permeability constant was 22.94 and 1.82 m/d (declining by 60.9% and 70.6%), respectively. The reactive zone remained stable and the injection of NZVI slurry could not cause any dramatic changes in the aquifer permeability.

scholarly journals Análise Montante-Jusante da Granulometria dos Sedimentos de Fundo e Suspenso do Rio Negro e Tributários (Bacia Amazônica, Brasil)

2021 ◽  
Vol 14 (2) ◽  
pp. 997
Author(s):  
Rogério Ribeiro Marinho ◽  
Antonio Fábio Sabbá Guimarães Vieira ◽  
Feliciano De Souza Maciel
Keyword(s):  
Sediment Transport ◽  
River Basin ◽  
Amazon Basin ◽  
Suspended Sediments ◽  
Fine Sand ◽  
Large River ◽  
Coarse Sand ◽  
Sediment Size ◽  
Negro River ◽  
Rio Negro

O conhecimento das características físicas de sedimentos transportados por grandes sistemas fluviais possui significativa importância para o entendimento de processos geomorfológicos e hidrológicos. O nível de conhecimento dos grandes sistemas fluviais da Amazônia e sua relação com o transporte de sedimentos ainda é limitado, resultando em lacunas de conhecimento sobre a dinâmica da paisagem nesta complexa região. Este trabalho teve como objetivo avaliar a distribuição espacial da granulometria de sedimentos de fundo e suspenso do Rio Negro e tributários. Realizou-se análise da distribuição do tamanho dos sedimentos em seções amostrais localizadas no alto, médio e baixo curso do Rio Negro. Os resultados da análise granulométrica da carga de fundo indicam a predominância de sedimentos com tamanho variando de 0,25 a 1,0 mm (principalmente areia fina, areia média e areia grossa) enquanto no baixo curso as amostram oscilaram de areia fina a partículas lamosas (< 0,50 mm). No Rio Negro os sedimentos suspensos são compostos principalmente de partículas finas de silte (90% menor que 80 µm) com diâmetro mediano (D50) de 25 µm. As características granulométricas apresentadas neste trabalho fornecem subsídios para o entendimento de processos hidrodinâmicos de transporte e deposição dos sedimentos de fundo e suspenso neste gigante sistema fluvial.    Upstream-downstream Granulometry Analysis of bed and suspended sediments in the Negro River Basin (Amazon Basin, Brazil)A B S T R A C TThe knowledge of the physical characteristics of sediments transported by large river systems has significant importance for the understanding of geomorphological and hydrological processes. The level of knowledge of the large rivers of the Amazon basin and their relationship with sediment transport is limited, resulting in gaps about the dynamics of the landscape in this complex region. This article analyzes the spatial distribution of granulometry of bed and suspended sediments in the Negro River and tributaries. An analysis of the sediment size distribution was carried out in sample sections located in the upper, middle and lower reaches of the Negro River. The results of the granulometric analysis of the bed load indicate the predominance of sediments with sizes ranging from 0.25 to 1.0 mm (mainly fine sand, medium sand and coarse sand) while in the low course they showed oscillated from fine sand to muddy particles (<0.50 mm). In the Negro River basin the suspended sediments are composed mainly of fine silt particles (90% less than 80 µm) with a median diameter (D50) of 25 µm. The granulometric characteristics presented in this work provide subsidies for the understanding of hydrodynamic processes of transport and deposition of bed and suspended sediments in this huge fluvial system.Keywords: sediment transport, Amazon floodplain, multichannel river, anabranching

scholarly journals Study On Critical Temperatures For Naphthalene And Chlorobenzene Removal During In Situ Steam Injection Remediation

2021 ◽  
Author(s):  
Ru xue Liu ◽  
Xinru Yang ◽  
Yongsheng Zhao
Keyword(s):  
Critical Temperature ◽  
Organic Pollutants ◽  
Organic Contaminants ◽  
Fine Sand ◽  
Steam Injection ◽  
Coarse Sand ◽  
Critical Temperatures ◽  
Factors Affecting ◽  
Remediation Process

Abstract Steam injection is an effective technique for the in situ remediation of volatile and semi-volatile organic contaminants. In this study, the influence of temperature and media on the removal of organic pollutants, such as naphthalene and chlorobenzene, was investigated in the remediation process through batch and remediation experiments, and the solid, liquid, and gaseous phase migration and transformation of organic pollutants during remediation were evaluated. The results demonstrated that the temperature significantly influenced the removal of organic pollutants. It was found that the critical temperatures for naphthalene and chlorobenzene were 50°C and 30°C, respectively. When the temperature was higher than the critical temperature, the final removal rates of naphthalene and chlorobenzene reached over 94% and 96%, respectively. The remediation area of chlorobenzene determined according to the critical temperature has a good result; the error compared with the actual remediation area in both coarse sand and fine sand was approximately 8.7%. In the simulation tank, the temperature changes can be divided into three stages: the ambient temperature stage, the temperature rapid rise stage, and the stable stage. Moreover, we found that the remediation effect of aquifers is not only related to temperature, but also to the location of the SVE well (soil vapour extraction). These findings reveal the main factors affecting the application of hot steam technology and the relationship between the temperature field and contamination field in the remediation process.

scholarly journals Marine substrate response from the analysis of seismic attributes in CHIRP sub-bottom profiles

2017 ◽  
Vol 65 (3) ◽  
pp. 332-345 ◽  
Author(s):  
Larissa Felicidade Werkhauser Demarco ◽  
Antonio Henrique da Fontoura Klein ◽  
Jorge Antonio Guimarães de Souza
Keyword(s):  
Grain Size ◽  
Seismic Reflection ◽  
Ground Truth ◽  
Fine Sand ◽  
Seismic Attributes ◽  
Coarse Sand ◽  
Unconsolidated Sediments ◽  
Shallow Gas ◽  
Size Classes ◽  
Seismic Reflection Profiles

Abstract This paper presents an evaluation of the response of seismic reflection attributes in different types of marine substrate (rock, shallow gas, sediments) using seafloor samples for ground-truth statistical comparisons. The data analyzed include seismic reflection profiles collected using two CHIRP subbottom profilers (Edgetech Model 3100 SB-216S), with frequency ranging between 2 and 16 kHz, and a number (38) of sediment samples collected from the seafloor. The statistical method used to discriminate between different substratum responses was the non-parametric Kruskal-Wallis analysis, carried out in two steps: 1) comparison of Seismic Attributes between different marine substrates (unconsolidated sediments, rock and shallow gas); 2) comparison of Seismic Attributes between different sediment classes in seafloors characterized by unconsolidated sediments (subdivided according to sorting). These analyses suggest that amplitude-related attributes were effective in discriminating between sediment and gassy/rocky substratum, but did not differentiate between rocks and shallow gas. On the other hand, the Instantaneous Frequency attribute was effective in differentiating sediments, rocks and shallow gas, with sediment showing higher frequency range, rock an intermediate range, and shallow gas the lowest response. Regarding grain-size classes and sorting, statistical analysis discriminated between two distinct groups of samples, the SVFS (silt and very fine sand) and the SFMC (fine, medium and coarse sand) groups. Using a Spearman coefficient, it was found that the Instantaneous Amplitude was more efficient in distinguishing between the two groups. None of the attributes was able to distinguish between the closest grain size classes such as those of silt and very fine sand.

The late Wisconsinan olistostrome of the lower Coppermine River valley, Northwest Territories

1986 ◽  
Vol 23 (11) ◽  
pp. 1700-1708 ◽  
Author(s):  
Denis A. St-Onge ◽  
Jean Lajoie
Keyword(s):  
Debris Flows ◽  
Late Quaternary ◽  
Fine Sand ◽  
Coarse Sand ◽  
Coarse Fraction ◽  
River Valley ◽  
Glacial Lake ◽  
The North ◽  
Geologic Record ◽  
Coppermine River

The late Quaternary olistostrome exposed in the lower Coppermine River valley fills a paleovalley that ranges in apparent width from 150 to 400 m and was cut into Precambrian bedrock before the last glaciation. The olistostrome is here named the Sleigh Creek Formation. The coarse fraction of the formation is matrix supported; beds are massive or reversely graded and have sharp, nonerosive contacts. These characteristics suggest deposition of the coarse fraction by debris flows. The olistostrome sequence is bracketed by, and wedged into, a marine rhythmite sequence, which indicates that deposition occurred in a marine environment.About 10 500 years BP glacier ice in the Coronation Gulf lowland dammed the valley to the south, which was occupied by glacial Lake Coppermine. Sediments accumulated in this lake in a 30 m thick, coarsening upward sequence ranging from glaciolacustrine rhythmites of silt and fine sand at the base to coarse sand alluvium, and deltaic gravels at the top. As the Coronation Gulf lowlands became ice free, the Coppermine River reoccupied its former drainage course to the north. The steep south to north gradient and rapid downcutting by the river through the glacial lake sediments produced unstable slope conditions. The resulting debris flows filled a bedrock valley network below the postglacial sea level, forming the diamicton sequence.The interpretation of the Sleigh Creek Formation raises questions concerning silimar diamicton deposits usually defined as "flowtills." More generally, the results of this study indicate that care must be used when attempting paleogeographic reconstructions of "glaciogenic" deposits in marine sequences in any part of the geologic record.

scholarly journals Live-Scale Testing of Granular Materials Stabilized with Alkali-Activated Waste Glass and Carbide Lime

2021 ◽  
Vol 11 (23) ◽  
pp. 11286
Author(s):  
Marina Paula Secco ◽  
Débora Thaís Mesavilla ◽  
Márcio Felipe Floss ◽  
Nilo Cesar Consoli ◽  
Tiago Miranda ◽  
...  
Keyword(s):  
Portland Cement ◽  
Mechanical Performance ◽  
Raw Materials ◽  
Sodium Hydroxide Solution ◽  
Fine Sand ◽  
Field Application ◽  
Natural Soil ◽  
In Situ Tests ◽  
Alkali Activated

The increasingly strong search for alternative materials to Portland cement has resulted in the development of alkali-activated cements (AAC) that are very effective at using industrial by-products as raw materials, which also contributes to the volume reduction in landfilled waste. Several studies targeting the development of AAC—based on wastes containing silicon and calcium—for chemical stabilization of soils have demonstrated their excellent performance in terms of durability and mechanical performance. However, most of these studies are confined to a laboratory characterization, ignoring the influence and viability of the in situ construction process and, also important, of the in situ curing conditions. The present work investigated the field application of an AAC based on carbide lime and glass wastes to stabilize fine sand acting as a superficial foundation. The assessment was supported on the unconfined compressive strength (UCS) and initial shear modulus (G0) of the developed material, and the field results were compared with those prepared in the laboratory, up to 120 days curing. In situ tests were also developed on the field layers (with diameters of 450 and 900 mm and thickness of 300 mm) after different curing times. To establish a reference, the mentioned precursors were either activated with a sodium hydroxide solution or hydrated with water (given the reactivity of the lime). The results showed that the AAC-based mixtures developed greater strength and stiffness at a faster rate than the water-based mixtures. Specimens cured under controlled laboratory conditions showed better results than the samples collected in the field. The inclusion of the stabilized layers clearly increased the load-bearing capacity of the natural soil, while the different diameters produced different failure mechanisms, similar to those found in Portland cement stabilization.

scholarly journals Relationship between Grain Size Distribution and Radon Content in Surficial Sediments of Wadi Arar, Saudi Arabia

2018 ◽  
Vol 8 (1) ◽  
pp. 2447-2451 ◽  
Author(s):  
M. A. M. Alghamdi
Keyword(s):  
Grain Size ◽  
Saudi Arabia ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Fine Sand ◽  
Coarse Sand ◽  
Negative Slope ◽  
Surficial Sediments ◽  
Fourth Degree ◽  
Radon Content

Surficial sediments with low radon content are desirable materials in construction applications. In this study, the relationship between grain size and radon content was investigated in sediments collected from seven sites in Wadi Arar, Saudi Arabia, with the intent of determining whether grain size analysis could be used for rapidly assessing the suitability of potential construction materials. Thirty-five samples were collected (five per site) and the grain size distribution was determined using sieves. Radon contents were measured on composite samples with a RAD7 radon detector. Among the sediment types (gravel, coarse sand, medium sand, fine sand, and silt and clay), the best linear correlations between grain size and radon contents were found for the coarse sand (negative slope, r=0.82) and fine sand (positive slope, r=0.78). Polynomial relationships were also tested. A fourth-degree polynomial equation effectively described the correlation between grain size and radon content (R2 = 0.933). As shown by this model, the highest correlations with radon contents were detected at grain sizes smaller than 2.0 mm. Thus, grain size may be useful for preliminary site assessment work.

scholarly journals Compositional and industrial assessment of Isua-Akoko, Akure, Ayadi and Lafe (Ode Aye) clay deposits of Ondo state, Nigeria

1970 ◽  
Vol 21 (1) ◽  
pp. 41-49
Author(s):  
O Adegbuyi ◽  
GP Ojo ◽  
AJ Adeola ◽  
MT Alebiosu
Keyword(s):  
Chemical Properties ◽  
Fine Sand ◽  
Coarse Sand ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
Medium Sand ◽  
Southwestern Nigeria ◽  
Firing Test ◽  
Clay Deposits ◽  
Ondo State

The physical and chemical properties of clay deposits around Isua-Akoko, Akure, Lafe and Ayadi in Ondo State southwestern Nigeria have been examined. The results have shown that Isua-Akoko, Akure and Lafe Clays are plastic fire clays while Ayadi clay is kaolinite. Grain size analysis reveals that Isua Akoko Clay contains 45% of clay, 18% silt, 12% fine sand,14% medium sand and 11% coarse sand and no gravel; Akure clay contains 42% clay, 14% silt, 13% fine sand, 20% medium sand and 8% coarse sand with 1% gravel. Lafe Clay contains 21% clay, 8% silt, 25% fine sand, 37% medium sand and 8% coarse sand with 1% gravel while Ayadi clay contains 83% clay and 17% silt. The liquid limits of these clay samples range from 41% to 73%% and plastic limits range from 18% to 26% respectively. The chemical analysis reveals that the most abundant mineral is silica (60.97%) and aluminum was next in abundance (23.69%) while other oxides are low. The results show that Isua-Akoko and Akure are residual while Lafe and Ayadi are sedimentary and transported Clays. The firing test, PH, and bleaching tests of the clays are also discussed. The chemical and physical characteristics of the clay deposits are strongly indicative of their industrial importance in the production of ceramics, refractories, paving bricks, paint and pharmaceutical products.KEYWORDS: Kaolinite, fire clay, gravel, ceramics and alumina.

scholarly journals Heavy metal distribution in sediments around the offshore tin mining area of Central Bangka Regency, Indonesia

2021 ◽  
Vol 926 (1) ◽  
pp. 012027
Author(s):  
Irvani ◽  
S Adibrata ◽  
M Yusuf ◽  
M Hudatwi ◽  
A Pamungkas
Keyword(s):  
Heavy Metals ◽  
Spatial Distribution ◽  
Active Surface ◽  
Fine Sand ◽  
Mining Area ◽  
Pollution Load Index ◽  
Coarse Sand ◽  
Sieve Analysis ◽  
Marine Animals ◽  
Type Composition

Abstract Vary heavy metals scattered in suspension loads and re-sedimentation from the tailing of the offshore-alluvial tin mining at Tanah Merah and its surroundings, Central Bangka Regency. Research is needed to determine the type, composition, spatial distribution of heavy metals, and potential pollution. The active surface-sediments were taken from shallow marine systematically around the offshore tin mining area in the east season. Geochemical analysis of sediment using x-ray fluorescence, coupled with minerals and sieve analysis, and support by spatial analysis. These sediments have dominant the sand-size (range very-fine sand to coarse sand) and silt, contained predominantly large quantities of quartz minerals and shell fragments of marine animals. The metals are in the following decreasing order: Cr>Zn>Pb>Ni>Cu>As>Co>Cd. The spatial distribution of heavy metals generally has a relatively south, east, and north position, with concentrations occurring along the coastline and showing the degradation composition towards the open sea. The marine sediments are uncontaminated to moderately contaminated by Cd and Pb, indicate both natural and anthropogenic enrichment, low the pollution load index (PLI), and have various potential ecological risks index (RI) (low to very high RI).

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