Study on the distribution characteristics of sediments on the mangrove beach of the sea-viewing promenade, Zhanjiang

Geotechnical properties and distribution characteristics of the Pacific seamount sediments, which coexist with cobalt‐rich manganese deposits (crusts and nodules), are essential data for the design of a seafloor mining system for the deposits. Samples were cored by a large‐diameter gravity corer during the research vessel Hakurei‐maru No. 2 survey cruises on the Pacific seamounts in 1991 and 1992. Various distribution characteristics of the sediments were studied. Analysis of the core samples showed that the geotechnical properties of the sediments become very important, in view of the new findings of debris‐flow‐like resedimentation of the cobalt‐rich manganese deposits and large shallow‐buried deposits beneath the sediments. These new findings are also very significant in terms of reserve reassessment Fundamental geotechnical properties of the sediments, such as size distribution, solid density, bulk density, water content, coefficient of internal friction, and cohesion are presented. Based on these data, their effects on the mining system design are also presented.

Based on the analysis of the distribution and characteristics of up-layer sediment in Lake Wuliangsuhai, its health status in terms of deposition rates were assessed. The results showed that: the distribution of deposition thickness significantly varied with sampling sites. These may be mainly controlled by the effects of landforms of the lake bottom, source of the sediment, hydrodynamic conditions, wind directions and speeds, aquatic vegetation etc. It deposited fluctuating larger in the southern area, relatively shallower in the northern, and less in the center and inlet area of the lake. Most of the areas in the lake are at the state of sub-healthy and un-healthy.

Fossil phytolith assemblages in lake sediments are widely used to reconstruct past vegetation patterns and dynamics, especially in subtropical environments. However, our understanding of how hydrodynamic conditions (river input and lake basin sedimentological processes) influence the transportation and taphonomy of phytoliths in lacustrine sediments is limited. The aim of this study is to use phytolith assemblage and grain size analyses of Qingshitan Lake surface sediments to identify the distribution characteristics and main transportation modes of phytoliths in lakes. Our results show that the grain size of surface sediments changes across different lacustrine areas of Qingshitan Lake. The median diameter (Md) and volume moment mean diameter (D(4,3)) of surface sediments gradually decreases with distance from the inlet river mouth. The phytolith assemblages of surface sediments vary between sampling locations in the lake. The percentage of woody dicotyledon phytoliths decreases from the estuary delta to the central lake basin, and correlates with the Md and D(4,3) of lake sediments. We find that phytolith assemblages in the riverine delta are mainly influenced by hydrodynamic (river input) processes and record the vegetation cover of the Gongping River catchment. Assemblages in the central lake basin are affected not only by riverine influences but also by eolian transport and similarly reflect the local vegetation. Investigating the relationships between the phytolith assemblages and sediment grain sizes in lakes may make it possible to identify the phytolith source area, which is crucial information to interpret assemblages and indices.

Tidal-dominated estuaries are a type of depositional system that is highly dynamic under the influence of tides. The interaction intensity between fluvial, tidal, and wave currents varies vertically along the coastline, resulting in a unique pattern of longitudinal gradient changes of facies associations and sediment distribution. Compared to river and delta sediments, research on ancient estuarine sediments is relatively limited. In this study, we analyzed observable data from the Late Cretaceous M1 Sandstone formation in the central northern region of the Oriente Basin, conducted in-depth research on its sedimentary characteristics, and proposed a tidal-dominated estuarine sedimentary model of this region. The rich core data provides reliable support for identifying sedimentary sequences of tidal environments, identifying a total of 14 lithofacies and 6 main types of facies associations, including tidal sand bars, tidal channels, and four types of tidal flats. These 6 types of facies associations correspond to the sediment accumulation characteristics in different sedimentary zones of the estuary, reflecting the differences in hydrodynamic conditions during the sedimentation process, such as strength, combination, and directionality. Furthermore, under the constraint of a dense well network, a detailed study of the stratigraphic pattern and deposit thickness was conducted to establish a matching relationship between sediment distribution characteristics and hydrodynamic characteristics in the entire region, providing sedimentary evidence for identifying tidal-dominated estuaries. Additionally, based on the combination relationships of tidal sequences, it was determined that there is a set of short-term sea level rise-fall cycles during episodic marine transgressions. The facies change of estuaries is sensitive to the response of sea level fluctuations. The results indicate that tidal sand bars are generally developed at the bottom of the tidal sequence. As the sea level decreases, the outer area is gradually covered by the tidal flat, of which the periodicity of the interior is clearer than that of tidal sand bars. Our research indicates a transition process from estuaries to deltas in the tidal system of M1 Sandstone formation under the influence of sea level fluctuations. The results provide evidence for a better understanding of the evolution of estuarine sediments in ancient strata.

Surface samples of bottom sediment from the Kuala Terengganu River, Terengganu were analysed to compare the distribution characteristics of sediment before and after monsoon season. Total of 8 stations were examined along the river as well as the estuary area. All the samples were analyzed base on its physical characteristics as: mean size, sorting, skewness and kurtosis. The results show that at the middle part of along the river, generally is dominated by very coarse sand before monsoon season ranges from 7.565 φ to - 0.1375 φ and has various type of particle sizes after monsoon season ranges from 7.495 φ to - 0.79 φ. At the left side of the river shows mean value ranged from 7.515 φ to -0.8305 φ before monsoon season. The mean values are changed after monsoon season between 7.525 φ to - 0.93 φ. While right side of the river indicates the mean value ranges from 7.74 φ to -0.919 φ before monsoon season and 7.5 φ to - 0.975 φ after monsoon season. The sorting, skewness and kurtosis are also indicated changes before and after the monsoon seasons. The statistical results show that the confidence interval contains the value 0.0, therefore it is not a statistically significant difference between sediment distribution before and after monsoon season. Thus, the characteristics of sediment distribution of 8 stations may not only depend on the monsoon effects but other factor such as dredging activity for this particular area of study.

Sediment dispersal and accumulation off the present Huanghe (Yellow River) delta as impacted by the Water-Sediment Regulation Scheme

It is of great significance to study the distribution characteristics and transport of heavy metals in complex sedimentary environments and areas with intensive human activities. This study analyzed sediment size, heavy metal contents (Cu, Zn, Cd, Cr, and Pb), organic carbon content, and sulfide content in surface sediments collected from 27 sites in Chengbei Sea. The main controlling factors of the distribution and transport of heavy metals were discussed from the perspective of sediment dynamics. The concentrations of Cu, Zn, Cd, Cr, and Pb in surface sediments were 7.9-20.5 mg/kg, 33.8-94.6 mg/kg, 0.08-0.26 mg/kg, 6.3-62.3 mg/kg, and 3-13.4 mg/kg, respectively. According to the geoaccumulation index, the study area was not polluted by the heavy metals, except for Cd, which did not pollute only areas with relatively coarse-grained sediments. Combining the results of correlation analysis, tidal residual current analysis, sediment transport trend analysis, and principal component analysis confirmed that Cu, Zn, and Cd originate from natural sources, and their distribution characteristics are mainly controlled by the grain size of surface sediments. Cr and Pb could be attributed to human activities, such as oil exploration, and their distribution characteristics were affected by sediment transport and tidal residual current. Zonation of the sedimentary dynamic environment also provided reference for the relationship between the distribution of heavy metals in surface sediments and sedimentary environments.

Changes in the distribution of surface sediment in Pearl River Estuary, 1975–2017, largely due to human activity

Two dams on the Elwha River, Washington State, USA trapped over 20 million cubic meters of sediment, reducing downstream sediment fluxes and contributing to erosion of the river's coastal delta. The removal of the Elwha and Glines Canyon dams between 2011 and 2014 induced massive increases in river sediment supply and provided an unprecedented opportunity to examine the response of a delta system to changes in sediment supply. The U.S. Geological Survey (USGS) developed an integrated research program aimed at understanding the ecosystem responses following dam removal. The research program included repeated surveys of beach topography, nearshore bathymetry, and surface sediment grain size to quantify changes in delta morphology and texture following the dam removals. For more information on the USGS role in the Elwha River Restoration Project, please visit http://walrus.wr.usgs.gov/elwha/. This USGS data release presents data collected during surveys of nearshore bathymetry, beach topography, and surface sediment grain size from the Elwha River delta, Washington. Survey operations were conducted between August 28 and August 30, 2012 (USGS Field Activity Number W-05-12-PS) by a team of scientists from the U.S. Geological Survey Pacific Coastal and Marine Science Center (PCMSC), Washington State Department of Ecology (WA DOE), and Washington Sea Grant. Nearshore bathymetry data were collected using the R/V Frontier and a personal watercraft (PWC), each equipped with single-beam echosounders and survey-grade global navigation satellite system (GNSS) receivers. Topography data were collected on foot with GNSS receivers mounted on backpacks. Positions of the survey platforms were referenced to a GNSS base station placed on a nearby benchmark with known horizontal and vertical coordinates. Depths from the echosounders were computed using sound velocity profiles measured with a conductivity-temperature-depth (CTD) sensor during the survey. A total of 116 km of nearshore bathymetric survey lines and 110 km of topographic survey lines were collected during the 3 days of survey operations. Environmental conditions were favorable, resulting in good coverage of the beach and nearshore region. Surface sediment was sampled using a small ponar, or 'grab', sampler from the R/V Frontier at a total of 57 locations in water depths between about 1 and 9 m around the delta. A continuous DEM surface of the primary survey area was produced from all available bathymetry and topography data using linear interpolation and a grid-spacing of 5 m. An additional DEM with 1-m resolution grid-spacing was produced using linear interpolation for for areas adjacent to the river mouth . Digital files containing the nearshore bathymetry data, beach topography data, derived DEMs, and grain-size data from this survey are available for download from the child item pages.

Based on the measured hydrological data and the established mathematical model of Xiaomiaohong channel, the current and sediment distribution characteristics are researched and analysed. Some conclusions are drawn as follows: (1) The maximum velocity and mean velocity of the measuring points in the groove were generally greater than those at points in the open waters; spring tide and neap tide strength difference is apparent, spring tide should play a major role in the beach evolution. (2) Suspended sediment concentration in the open sea is significantly lower than that in the tidal channel; the bottom sediment concentration is generally greater than surface, bottom surface sediment concentration is 1.12 ~ 1.66 times (3) Median particle diameter of suspension sediment is 0.005 ~ 0.017, mainly for fine silt and very fine sand.

Sediment distribution characteristics and environment evolution within 100 years in western Laizhou Bay, Bohai Sea, China

The sediment distribution characteristics and transport pattern in the eastern China seas

Seasonal distribution patterns of 7Be and 210Pb in surface sediments in the Changjiang Estuary, China and their implication

Spatial variability of phosphorus adsorption in surface sediment at channel confluences: Field and laboratory experimental evidence

Data on grain size and heavy mineral composition for surface sediments on the Prydz Bay continental shelf was analysed to identify sediment features and provenance. The grain size composition of surface sediments indicate spatial variations in the glaciomarine environment and the key factors influencing sedimentation, which on the shelf include topography/water depth, currents and icebergs. The study area was divided into two sections by Q-type factor analysis: section I included Prydz Channel, Amery Basin and Svenner Channel, and section II included Four Ladies Bank, Fram Bank and the area in front of the Amery Ice Shelf. Sedimentation in section I is mainly controlled by currents and topography/water depth. However, in section II, icebergs/floating ice masses, the Amery Ice Shelf and currents have prominent effects on sedimentation. The heavy mineral composition indicates that surface sediments on the eastern side of the bay, including Four Ladies Bank, are primarily derived from Princess Elizabeth Land. Sediments in the area in front of the Amery Ice Shelf, Svenner Channel, Amery Basin and Prydz Channel have a mixed source from the eastern regions around the bay, including the Prince Charles Mountains and Princess Elizabeth Land. The contribution from Mac. Robertson Land to sediment at Fram Bank is limited.