Sorting Coefficient Research Articles

Advances in the simulation and automated measurement of well‐sorted granular material: 2. Direct measures of particle properties

In this, the second of a pair of papers on the structure of well‐sorted natural granular material (sediment), new methods are described for automated measurements from images of sediment, of: 1) particle‐size standard deviation (arithmetic sorting) with and without apparent void fraction; and 2) mean particle size in material with void fraction. A variety of simulations of granular material are used for testing purposes, in addition to images of natural sediment. Simulations are also used to establish that the effects on automated particle sizing of grains visible through the interstices of the grains at the very surface of a granular material continue to a depth of approximately 4 grain diameters and that this is independent of mean particle size. Ensemble root‐mean squared error between observed and estimated arithmetic sorting coefficients for 262 images of natural silts, sands and gravels (drawn from 8 populations) is 31%, which reduces to 27% if adjusted for bias (slope correction between observed and estimated values). These methods allow non‐intrusive and fully automated measurements of surfaces of unconsolidated granular material. With no tunable parameters or empirically derived coefficients, they should be broadly universal in appropriate applications. However, empirical corrections may need to be applied for the most accurate results. Finally, analytical formulas are derived for the one‐step pore‐particle transition probability matrix, estimated from the image's autocorrelogram, from which void fraction of a section of granular material can be estimated directly. This model gives excellent predictions of bulk void fraction yet imperfect predictions of pore‐particle transitions.

Diagenesis of deep sandstone reservoirs and a quantitative model of porosity evolution: Taking the third member of Shahejie Formation in the Wendong Oilfield, Dongpu Sag, as an example

Abstract The diagenesis and porosity evolution in the deep 3rd member of Shahejie Formation of the Wendong Oilfield was analyzed using thin-sections, casting thin-sections, X-ray diffractometry, scanning electron micrograph observations, and other data. Sandstone reservoirs are currently at the late diagenetic period. Pores consist of primary pores and the inter-granular dissolved and intra-granular dissolved pores of feldspar, debris and carbonate cements. Physical properties are mainly controlled by carbonate cementation and dissolution, and distribution of abnormally high fluid pressure. The evolution of porosity parameters shows that primary porosity is 36.75%, the porosity loss rate is 40.49% during the process of mechanic compaction, the porosity loss rate is 37.25% during the process of cementation and metasomasis, and the porosity increase rate is 17.88% during the process of dissolution. The proportion of primary porosity is 55.03%, and that of the secondary porosity is 44.97%. The error rate in the quantitative study of porosity is 0.96%, and the main influencing factor of the error rate is sorting coefficient of detrital rock (S0).

Distributions of sediments of the tidal flats in response to dynamic actions, Yangtze (Changjiang) Estuary

Sediment samples with high spatial resolution (432 samples in total) and flow data were collected on the tidal flats in the mouth-bar region of the Yangtze Estuary. The data was collected in July 2005, July 2006 and May 2007. The samples were analyzed with a particle sizer, resulting in the sediment distribution. The grain sizes and related parameters were analyzed. The results were presented in a ternary diagram. The sediment mainly consisted of sand, silty sand, sandy silt, sand-silt-clay, silt and clayey silt. And sand skeletons and clay matrices were found. At Nanhui Shoal, silt skeletons could be identified as well. Furthermore, the results were discussed per shoal. Although some depth dependencies were found per shoal, no general relation was found. The results are as follows: sediment located at these tidal flats of the Yangtze Estuary was mainly composed of sand, silty sand and silt. The median grain size in sediment was relatively complex with a range from 2.5 φ to 8 φ. The distributions of sorting coefficients ranging from 1 to 2 were in agreement with median sizes. It was suggested that sediment of the tidal flats was coarser and better sorted or finer and worse sorted. The skewness in sediment distribution varied from 0.1 to 0.8. In addition, the distributions of sorting coefficient and skewness in sediment at Chongming Eastern Shoal, Hengsha Eastern Shoal and Jiuduan Shoal were of similar characteristics because there were closely positive correlated relationships among these parameters. However, due to the location difference between Nanhui Southern Shoal and Eastern Shoal, the values of sorting coefficient and skewness had relatively large distinctions. The tracks of sediment transport could be described based on the distributions of sediment, which might reveal sediment transport controlled by two dominant hydrodynamic factors of current and wave. It was appreciable that coarser sediment with lower sorted coefficient was affected by dominant ebb current action and intense wave action resulted from rapidly dissipated wave energy. Moreover, due to the effects of obstructed branches, guided current and broken wave actions of the Deep Water Channel Project, grain-size in sediment located at two sides of the groyne was of uneven distribution characteristics.

Non-uniformity and layering in sediment transport modelling 1: flume simulations

The development and validation of an integrated numerical sediment transport model capable of solving both uniform and non-uniform transport equations while calculating grain size distributions is presented. The model is coupled with external hydrodynamic codes which provide flow field and bed shear stress patterns. Transport equations are solved for an unlimited number of sediment size fractions. Two validation experiments involving unsteady flow in a channel bend and steady flow in a flume with lateral contraction were considered. Good agreement with measured bed deformations was found for non-uniform calculations with an exchange layer, whereas both uniform and non-uniform computations without the exchange layer resulted in comparably larger differences. In the channel bend experiment, the presence of an exchange layer was essential for achieving accurate modelling results, while its role was less pronounced in the lateral contraction experiment. Moreover, the sorting coefficient of the bed material was found to be a suitable indicator for estimating the applicability of uniform transport equations.

Porosity and particle shape changes leading to shear localization in small-displacement faults

A microstructural study of shear localization in fault gouge was carried out in small-displacement faults so there would be minimum masking effects from a complex deformation history. We studied particle size, shape, and porosity changes in gouge adjacent to zones of shear localization in natural and synthetic gouges subjected to shear displacements δ, of up to 1.2 m. Scanning electron microscope images were used for estimating image porosity Φ I, and measuring particle size of the deformed and undeformed gouges. The particle size data were used for calculating simulated porosity Φ S from computer-generated simple fractal gouge model of each sample. Modeled microstructures contained round grains and a fractal distribution matched to that of the measured natural samples. Changes in Φ I, Φ S, and Φ I/ Φ S with increasing δ were used for tracking changes in particle shape and porosity of the gouges precursory to shear localization. The Φ I and Φ S values for the natural and synthetic gouges converge at δ ∼ 0.1 m, suggesting that gouge particles adjacent to shear localization sites tend to become rounded. Porosity for such densified regions of the gouge adjacent to Y-shear zones was determined to be <1% at large displacements. In the same regions, the porosity reductions were also associated with decreased sorting coefficient and fractal dimensions D > 2.6. The study suggests that brittle shear localization may involve favorably-oriented micro porous pockets of gouge that result from competing changes in particle shape and particle size, which tend to affect gouge porosity in different ways.

An automatic microturbidostat for bacterial culture at constant density

We have developed a microturbidostat for long time bacterial culture at constant density controlled by optical detection and integrated pneumatic valves. The device was fabricated by multilayer soft lithography and in-situ formation of an agarose filter. The culture chamber of bacteria was connected in one side to a single bacterial input-output channel and in another side to a nutrient channel in which the agarose filter was formed to ensure the diffusion of nutrients and metabolites without bacterial loss. The bacterial number in the culture chamber was determined by measuring the fluorescence intensity of GFP proteins of the bacteria and the redundant bacteria could be exported automatically through the input-output channel with integrated micro-valves. In order to optimize the operation performance, we investigated the bacterial exportation efficiency with different input-output channel widths. As expected, the bacterial sorting coefficient was proportional to the input-output channel width. The results also showed that with a 20 microm channel-width, a long time culture was possible with a constant bacterial number in the chamber in the range from 400 to 700.

The application of geostatistics in grain size trend analysis: A case study of eastern Beibu Gulf

There are 71 surface sediment samples collected from the eastern Beibu Gulf. The moment parameters (i.e. mean size, sorting and skewness) were obtained after applying grain size analysis. The geostatistical analysis was then applied to study the spatial autocorrelation for these parameters; while range, a parameter in the semivariogram that meters the scale of spatial autocorrelation, was estimated. The results indicated that the range for sorting coefficient was physically meaningful. The trend vectors calculated from grain size trend analysis model were consistent with the annual ocean circulation patterns and sediment transport rates according to previous studies. Therefore the range derived from the semivariogram of mean size can be used as the characteristic distance in the grain size trend analysis, which may remove the bias caused by the traditional way of basing on experiences or testing methods to get the characteristic distance. Hence the results from geostatistical analysis can also offer useful information for the determination of sediment sampling density in the future field work.

Studying the Morphologic Maturation of Aeolian Sand Grains During Transportation Process of Wind Erosion (Case study: Khartouran Erg)

Wind, in the duration of its erosional process, affects considerable changes in a grain's morphologyfrom its removal (detachment) step to sedimentation. In other word, a grain undergoes its gradualevolution during the transit process. In this project, the maturation of Aeolian sand grains had beenstudied upon as based on texture maturity indicator which includes: sorting, mean size grain, roundness aswell as abrasion coefficient parameters. The study area is the transport region of Khartouran Ergsediments, which founded on the basis of ground of wind erosion. According to these indicators,the direction of prevailing strong winds is notably mentioned. In a later step, four transects are selectedin different area in alignment with wind direction. Samples of sediment grains are taken at varieddistances in any one of the transects. The samples were taken from the windward slope of Rebdoulandform. The samples were evaluated to using granulometry and morphoscopy techniques. Grain sizeanalysis of was done using dry sieve analysis while morphoscopy of grains carried out by studying thequartz grains of 150 to 300 μm diameter by using binocular microscope. Results indicate a gradualmaturity (evolution) in sediment texture in all transects starting from the upper parts (near sand source)toward the lower parts (in transportation area).Also, results indicate that from among the four indicatorsof grain maturity namely: sorting, grain size, roundness and abrasion coefficient the respective factors ofeither abrasion coefficient index or roundness in the first value and then sorting and finallygrain’s mean size index are the ones accounted for validation for determination of maturity.

Parasitism as a determinant of community structure on intertidal flats

The burrowing and movement ability of the New Zealand cockle Austrovenus stutchburyi is reduced when infected by echinostome trematodes. Previous experimental evidence from a single site suggests that this parasite-induced behavioural change of a key bivalve can affect the structure of the surrounding benthic community. By using multiple regression analyses on data collected from 17 intertidal flats, we here show that cockle parasitism is associated with macrozoobenthic community structure on a larger spatial scale. Regressions were performed for animal abundance, biomass, species diversity and species richness separately, entering cockle parasitism (infection intensity), presence/absence of ghost shrimps (Callianassa filholi), cockle density, primary producer abundance and organic content, particle size, sorting coefficient and gravel content of the substrate as predictors. Next to ghost shrimps, cockle parasitism was the best predictor of animal abundance by affecting (mainly positively) 8 of the 49 most widespread species significantly. Cockle parasitism was also associated with the biomass of anthozoans (positively), nemerteans (negatively) and bivalves (positively), whereas overall animal biomass was positively related to the sorting coefficient of the substrate. Species diversity was positively associated with cockle parasitism and gravel content of the substrate. Species richness was significantly associated with cockle parasitism (positively), ghost shrimps (negatively) and abundance of primary producers (positively) in combination. The impact of cockle parasitism on benthic community structure is believed governed directly or indirectly by (1) reduced sediment disturbance, (2) increased surface structural complexity and (3) availability of larval trematodes as an additional food source.

Flow resistance in steep mountain streams

AbstractResistance to flow at low to moderate stream discharge was examined in five small (12–77 km2 drainage area) tributaries of Chilliwack River, British Columbia, more than half of which exhibit planar bed morphology. The resulting data set is composed of eight to 12 individual estimates of the total resistance to flow at 61 cross sections located in 13 separate reaches of five tributaries to the main river. This new data set includes 625 individual estimates of resistance to flow at low to moderate river stage. Resistance to flow in these conditions is high, highly variable and strongly dependent on stage. The Darcy–Weisbach resistance factor (ff) varies over six orders of magnitude (0·29–12 700) and Manning's n varies over three orders of magnitude (0·047–7·95). Despite this extreme range, both power equations at the individual cross sections and Keulegan equations for reach‐averaged values describe the hydraulic relations well. Roughness is divided into grain and form (considered as all non‐grain sources) components. Form roughness is the dominant component, accounting for about 90% of the total roughness of the system (i.e., form roughness is on average 8.6 times as great as grain roughness). Of the various quantitative and qualitative form‐roughness indicators observed, only the sorting coefficient (σ = D84/D50) correlates well with form roughness. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Diversity and spatial distribution of sediment ammonia-oxidizing crenarchaeota in response to estuarine and environmental gradients in the Changjiang Estuary and East China Sea

Ammonia-oxidizing archaea (AOA) have recently been found to be potentially important in nitrogen cycling in a variety of environments, such as terrestrial soils, wastewater treatment reactors, marine waters and sediments, and especially in estuaries, where high input of anthropogenic nitrogen is often experienced. The sedimentary AOA diversity, community structure and spatial distribution in the Changjiang Estuary and the adjacent East China Sea were studied. Multivariate statistical analysis indicated that the archaeal amoA genotype communities could be clustered according to sampling transects, and the station located in an estuarine mixing zone harboured a distinct AOA community. The distribution of AOA communities correlated significantly with the gradients of surface-water salinity and sediment sorting coefficient. The spatial distribution of putative soil-related AOA in certain sampling stations indicated a strong impact of the Changjiang freshwater discharge on the marine benthic microbial ecosystem. Besides freshwater, nutrients, organic matter and suspended particles, the Changjiang Diluted Water might also contribute to the transport of terrestrial archaea into the seawater and sediments along its flow path.

Polychaete assemblages of the northwestern Ross Sea shelf: worming out the environmental drivers of Antarctic macrobenthic assemblage composition

We have limited understanding of which environmental factors structure the distribution patterns and composition of Antarctic macrobenthos assemblages, and the spatial scales on which such factors operate. In 2004, the “BioRoss Survey” was conducted on the northwestern Ross Sea shelf between Cape Adare and Cape Hallett in depths of 50–750 m to describe and quantify the assemblage patterns of benthic macroinvertebrates. In order to determine the influence of primary productivity, disturbance and habitat heterogeneity on the distribution and composition of the macrofaunal assemblages, polychaete data derived from 52 grab samples were analysed. Although differences in the composition of polychaete assemblages among different sampling transects and depth strata were not particularly pronounced (yet statistically significant), the results suggested that large-scale differences in both primary productivity and iceberg disturbance influence distribution patterns. The combination of sediment chl a content, sorting coefficient, sponge spicule content and distance to the nearest iceberg scour best explained polychaete assemblage patterns. This finding supports previous contentions that multiple environmental drivers working at varying scales influence Antarctic shelf assemblages. The results do not supply support for a pronounced decoupling of pelagic and benthic systems, as has been suggested by another study of deeper water benthic assemblages on the Ross Sea shelf.

砂粒子画像を用いた底質粒径の計測法の妥当性に関する研究

A method for determining grain size from digital images of sediment proposed by Rubin was applied to field data and experimental data. Its accuracy is poor under sediments with the high sorting coefficient because fine-grained sand may be burned under coarse-grained sand. It is possible to estimate the grain size unless water permeates the sediment surface for the wet grained sand. But the grain size measured by digital images is nearly equal to that by sieving, The experimental data showed that the sorting process would be generated in a short period, and then fine-grained sand is deposited on the offshore side and coarse one on the onshore side under depositional wave actions.

CONSEQUENCES OF HYDRAULIC DREDGING FOR A RAZOR CLAM &lt;i&gt;Ensis siliqua&lt;/i&gt; (L.) BED IN THE NORTH-WEST IRISH SEA

The Gormanstown razor clam bed, which measured 21km2 in extent in 1998, provided more than half the razor clams harvested in Europe for three years, 1999–2001. Exploitation of the bed commenced in late 1997. As a result of hydraulic dredging, the sediments have higher sorting coefficients and some larger grades were added in the form of shell fragments in the intervening years. The macrobenthos of the bed was monitored over a period of seven years, beginning one year after exploitation commenced. Throughout that time the dominant species, Ensis siliqua , which had accounted for up to 90% of the biomass in the first year of the study, declined to approximately 50% in 2005. Ensis siliqua displays the characteristics of a K-selected species: heavy standing biomass, type one survivorship curve and slow replication. Coinciding with exploitation, the bed was invaded by other deposit and suspension-feeding bivalves, notably Pharus legumen and Lutraria lutraria, whose population expansion can be traced to the early dredge fishery. The ratio of Ensis to Lutraria sampled weights was 124:1 in 1998, but it steadily advanced to 1.2:1 in 2005. Thus Lutraria , another suspension feeder, has displaced the razor clam. The Shannon-Wiener index of diversity rose as exploitation of the bed progressed, and in 2005 (eight years after dredging commenced), it had not returned to its 1998 level. However, the trend over the period was downwards, suggesting that a new stability involving a different species composition may be achieved. An age length key applied to length–frequency distributions of E. siliqua indicated that no age class older than age eleven has accounted for 10% of the population since 2001, although that was usually the case in the four preceding years.

The influence of stream age and environmental variables in structuring meiofaunal assemblages in recently deglaciated streams

The influence of stream age and environmental variables on meiofaunal assemblages were examined for 15 streams across a temporal gradient of 200 yr in Glacier Bay National Park, southeast Alaska. Meiofaunal assemblages were found in all streams but varied in diversity and abundance. Copepod species found had a wide range of habitat affinities and good dispersal abilities; we argue that the observed copepod assemblage in a given Glacier Bay stream is determined by habitat availability rather than dispersal constraints. Two-way indicator species analysis (TWINSPAN) classified the meiofaunal assemblages largely according to stream age. Stepwise multiple regressions were performed on environmental variables and meiofaunal species richness or abundance, and predictors differed between taxa. The sorting coefficient, a measure of the diversity of particle sizes in the sediment, best explained the variation in both total harpacticoid copepod abundance and meiofaunal taxon richness (together with stream gradient). Harpacticoids were more abundant in relatively well-sorted streams and declined as the range of particle sizes within the streams increased; the opposite pattern to that found in the marine environment. The abundance of Bryocamptus spp. was best explained by models incorporating stream age and indicators of habitat complexity, whereas abundance of Tardigrada, Chaetogaster, and Moraria affinis increased with increasing substrate stability. A habitat templet was developed for the meiofaunal assemblages in Glacier Bay streams. Stream age (incorporating stream habitat complexity) formed one axis and the second axis was the sorting coefficient.

Spatial and Environmental Factors Affecting the Distribution of the Main Decapod Crustacean Prey Species in the NW Mediterranean

The decapod crustaceans Alpheus glaber, Calocaris macandreae, Processa canaliculata and Solenocera membranacea are some of the most common prey items for both fish and other decapod crustaceans in the muddy bottom communities of the lower continental shelf and upper slope in the western Mediterranean Sea. Despite their high densities and key ecological role, these species are often neglected in scientific studies due to their relatively small size and the associated difficulties in adequately sampling them, so little information is available on their biological and ecological characteristics. We studied the spatial distribution of these four main crustacean prey species in an area off the Ebro Delta (W Mediterranean), using non-linear geostatistics. We performed log-normal kriging, considering depth as a covariate in the spatial model (universal kriging with external trend). All semivariograms were fitted to a spherical model, but with different relationships to depth. All species were more abundant in a sub-area characterised by a gentler slope and the presence of submarine canyons. The spatial correlation between densities of all species and sediment variables were analysed. All species except Solenocera membranacea were negatively correlated with sorting coefficient (IGSD), showing a preference for well sorted, homogeneous sediments corresponding to low energy areas. Further, Calocaris macandreae higher densities were associated with areas of coarser grain size (Φ) and Processa canaliculata density was negatively correlated with carbonate content of the sediment (CO3).

Polychaete Fauna of Seagrass Beds (Halodule wrightii Ascherson) Along the Coast of Rio de Janeiro (Southeast Brazil)

Abstract. The polychaete community structure from six Halodule wrightii seagrass beds along the Rio de Janeiro coast (Southeast Brazil) was investigated. Variations in species diversity, overall density and species composition in relation to sediment grain size, seagrass biomass and selected plant structural features such as root and shoot length from the study sites were analysed. Ten core samples (0.02 m2) were randomly collected from each site. Three additional samples were taken for grain size analysis of sediment. Sixty‐eight species of polychaetes belonging to 24 families were found. The dominant species as well as species composition varied greatly among sites, showing that a typical polychaete community does not exist. The number of species was positively correlated with the silt‐clay percent and sorting coefficient of the sediment. A positive correlation between polychaete density and plant biomass was also obtained. Multivariate analysis indicated that polychaete communities were influenced greatly by seagrass plant features: plants with longer shoots harbour mainly surface‐deposit feeders such as Magelona papillicornis, whereas plants with a higher root‐shoot length relation sheltered mainly suspension or interface feeders like Fabricia filamentosa. This study demonstrates that granulometric properties as well as plant architecture play an important role in structuring the polychaete community. As the community‐level response can reflect changes in local seagrass beds, the structure of the polychaete community can be an important indicator for management plans and the restoration of seagrass ecosystems.

Comparative Study of Sand Porosity and a Technique for Determining Porosity of Undisturbed Marine Sediment

Porosity is a fundamental property of marine sediment from which wet bulk density can be easily determined and used in a variety of geoacoustic, geotechnical, and sedimentological studies, analyses, and models. However, methods of sampling marine sands suffer from the common problem of core disturbance making the in situ porosity difficult to obtain. Embedding the sediment within an epoxy resin matrix will minimize the disturbance to the microfabric and preserve the in situ sedimentary structure for subsequent study. Image analysis can then be used on thin sections to study the microfabric and porometry. A comprehensive review and analysis of published data on the porosity of predominantly clean sands has been completed and a simple, accurate, and nondestructive technique is described for preparing and measuring the porosity of marine sediment (siliciclastic sand) that has been infiltrated aboard ship immediately upon sample collection and chemically fixed and infiltrated with epoxy shortly thereafter. The average porosity of 36 samples of marine sand collected offshore Fort Walton Beach, Florida, and embedded with resin was determined to be 41.30%. From the review of published data the average porosity of sand was determined to be 37.7%, 42.3%, and 46.3% for packed, natural (in situ), and loose packing conditions, respectively, for a range of sorting coefficients and grain sizes.

The coast evolution and regulation in Wanquan River Estuary, Hainan Island

In this paper, sediment samples were collected along the Wanquan beaches and sieved in the laboratory in order to obtain the grain size distributions and associated parameters, i.e. mean grain size, sorting coefficient and skewness. Furthermore, we have calculated the longshore drift sediment transport rates and equilibrium cross-sectional areas of the entrance channel by using the method of sedimentary dynamics. The results indicate that the longshore drift sediment transport is dominated by waves with a direction from south to north, which result in rapid changes of the entrance channel. Therefore, some suggestions were proposed for improving the water quality and restoring the ecosystem of estuary. The engineering method includes increasing the sea-route of entrance channel, tidal prism and water exchanges in Shamei Lagoon.

Small-scale non-linear geostatistical analysis of Liocarcinus depurator (Crustacea: Brachyura) abundance and size structure in a western Mediterranean population

The small-scale spatial distribution of density and biomass of the crab Liocarcinus depu- rator off the Ebro delta was analysed using universal kriging (non-linear geostatistics), considering depth as an external trend. In order to understand the spatial distribution of crab size, a third variable was created from the residuals of the non-linear regression between biomass and density. Variogram analysis of crab density and residuals of the biomass/density relationship presented a quadratic rela- tionship with depth, while biomass showed a linear relationship with depth. All experimental vario- grams were fitted to spherical models. The patch size (range) found was 10.64 km for density, 14.53 km for biomass and 20.49 km for the residual variables. The spatial distribution of 8 sediment variables (temperature, redox potential at 1 and 6 cm depth (R1 and R6), carbonate content (CO3), median grain size (ϕ), sediment sorting (IGSD: inclusive graphic standard deviation) and organic matter content (OM)) was studied. The maps obtained were compared with those calculated for the biological variables of L. depurator using Mantel and partial Mantel tests. Distribution characteristics of this species were significantly affected by most sediment variables considered, particularly by tem- perature, organic matter content and redox potential, although overall the correlation level was low, coinciding with the generalist ecological role and opportunistic behaviour of the species. Density and biomass, as well as residuals, presented a negative correlation with the sorting coefficient (IGSD) and with carbonates. In relation to IGSD, high densities of L. depurator were found in homogeneous sed- iments. Residuals (size structure of the population) were significantly correlated with grain size (ϕ), with larger individuals occurring in finer sediments, while juveniles were preferably found in areas with very fine sand sediments. Both density and biomass presented significant positive correlations with the redox potential, indicating that the species favoured well-oxygenated sediments with a low organic content.