Grain Size Fractions Of Sediments Research Articles

Evaluation of toxic metals in different grain size fractions of sediments of the southeastern Black Sea

Surficial marine sediment samples were collected along the southeastern Black Sea (Trabzon) coast. The sampling was conducted in June 2019 from eleven stations, with the depths varying between 8 and 30 m. Metal concentrations (Cu, Pb, Zn, Ni, As, and Cr) were evaluated in four different sediment size fractions; 0.063 mm (F1), 0.125 mm (F2), 0.25 mm (F3), and 0.5 mm (F4). Geoaccumulation Index (IGEO), Sediment Enrichment Factor (SEF), Ecological Risk (Er), and Potential Ecological Risk Index (RI) were used to determine potential anthropogenic hotspots. Temperature, pH, salinity, dissolved oxygen, and total organic carbon were determined to assess the variation across the sampling area. The highest metal concentrations (Cu:113.4 ± 45.1; Pb:85.9 ± 28.9; Zn: 138.6 ± 18.8; Ni:37.8 ± 7.6; As:14.1 ± 3.6; and Cr: 29.9 ± 5.4 ppm) were obtained in the smallest sediment fraction 0.063 mm (F1). The fractions of sediment structure were polluted by Cu, Pb, and As from moderate and severe levels according to IGEO and SEF.

Temporal constraints on lateral organic matter transport along a coastal mud belt

Constraints on timescales of lateral transport of sedimentary organic carbon (OC) over continental shelves and associated influences on the distribution and abundance of OC remain sparse. Preferential degradation of labile, young OC during lateral transport results in apparent “diagenetic aging” of OC. Additionally, sediment translocation can also result in “transport time-associated aging” of associated organic matter (OM) as a function of the lateral transport time (LTT). Here, we use a coupled thermal decomposition and radiocarbon (14C) approach to constrain timescales of lateral transport and concomitant loss of OC associated with different grain size fractions of sediments collected from two locations ∼275 km apart along a dispersal pathway on the inner shelf of the East China Sea. The 14C age contrasts between corresponding thermal fractions are used to distinguish these two components of sedimentary OM “aging”. To minimize interferences from hydrodynamic sorting and diagenetic aging of OC accompanying lateral transport, we assess 14C age differences of decomposition products from the most thermally-refractory OC components associated with specific grain size fractions between locations. We show that LTTs vary among different grain size fractions, and examine relationships between LTTs and sedimentary OC loss in order to assess the decomposition of OC as a consequence of lateral transport. We suggest that the decomposition of OC associated with protracted lateral transport exerts a strong influence on OC burial efficiency, with broad implications for carbon cycling over continental shelves.

Tidal inlet sediment bypassing at mixed-energy barrier islands

The large-scale littoral sediment drift along barrier island coasts involves alongshore sand transport at the islands’ surf zone and across tidal inlets. Mechanisms of sediment bypassing at non-migrating, mixed-energy tidal inlets are discussed based on process-based numerical modeling of sediment dynamics at an exemplary barrier island system in the southern North Sea. Residual transport pathways of distinct sediment grain-size fractions and morphological changes reveal the complexity of processes at tidal inlets driven by the non-linear interaction of competing tidal and wave forces. Sediment bypassing from the updrift to the downdrift shoreline of a tidal inlet is evaluated and the ratio of bypassed to recirculated sand volumes is estimated. Common inlet bypassing schemes are discussed and verified. It is shown that the different bypassing mechanisms can happen simultaneously and are related to the transport behavior of particular sediment grain-size fractions: Very fine to fine sand bypasses the inlet along the entire ebb-tidal delta periphery by wave-induced transport processes. Fine to medium sand is transported by the ebb-directed tidal currents in the inlet throat to the ebb-tidal delta where wave-driven transport processes and bar welding bypasses the sediments to the downdrift shore. For fine to medium and medium sands, a sediment recirculation cell at the downdrift ebb-tidal delta and reversal to the main inlet throat is identified.

Variation of the chemical composition of sediments under middle- and low-temperature hydrothermal conditions in the southern trough of Guaymas Basin, Gulf of California: Communication 2. Results of the study of grain size fractions of sediments

The chemical composition of grain size fractions of the Upper Pleistocene sediments in the southern trough of Guaymas Basin (Gulf of California) is studied based on materials from DSDP Hole 477 (191 m). The sediments are located in the upper part of the main long-lived hydrothermal system. Therefore, they were subjected to long-term reworking by the middle- and low-temperature solutions (100‒300°C) and short-term hydrothermal impact during the intrusion of basalt sills. The upper part of the main hydrothermal system is divided into three middle- to low-temperature hydrothermal alteration zones: lower (III), middle (II), and upper (I). In zone III (250‒300°C), hydrothermal alterations of sediments are most significant. The coarsegrained fractions are enriched in Fe, S, Ni, Cu, Zn, Mo, Co, Se, Cd, Bi, Pb, and Ag due to the formation of sulfides and precipitation of native metals. The silt fractions are enriched in Be, Sc, Nb, Ta, W, Th, U, Y, and REE. In contrast, the pelite fractions are depleted in most of these elements. The fine-dispersed (<0.001 mm) pelite fractions are appreciably enriched in Mg (due to the formation of the authigenic Mg-chlorite), as well as MnO, Cr, V, Ga, Pb, and Zr. Virtually all grain size fractions are depleted in K2O, Li, Rb, Cs, and Tl due to the dissolution of the K-bearing terrigenous minerals. In zones II (146‒170 m) and I (110‒146 m), where the temperature of hydrothermal solutions dropped successively from 250 to 180‒195 and 100°C, the sedimentary environment was unfavorable for the concentration of Fe, S, and a large group of ore elements that are typical for sediments in zone III. Intrusion of basalt sills and a short-term hydrothermal impact changed concentrations of several components in the sediments overlying the sill complex: CaO, K2O, Li, Rb, Cs, and Tl acquired a trend typical of the high-temperature lower zone III, whereas Fe, MgO, P2O5, TiO2, V, Sc, and Y distribution pattern became typical of the low-temperature upper zone I. Significant compositional variations in the grain size fractions of sediments are lacking beneath the sill base.

Regional environmental change and human activity over the past hundred years recorded in the sedimentary record of Lake Qinghai, China.

Environmental change and human activity can be recorded in sediment cores in aquatic systems such as lakes. Information from such records may be useful for environmental governance in the future. Six sediment cores were collected from Lake Qinghai, China and its sublakes during 2012 and 2013. Measurements of sediment grain-size fractions indicate that sedimentation in the north and southwest of Lake Qinghai is dominated by river input, whereas that in Lake Gahai and Lake Erhai is dominated by dunes. The sedimentation rates in Lake Qinghai were calculated to be 0.101-0.159cm/y, similar to the rates in other lakes on the Qinghai-Tibetan Plateau. Using these data and sedimentation rates from the literature, we compiled the spatial distribution of sedimentation rates. Higher values were obtained in the three main areas of Lake Qinghai: two in river estuaries and one close to sand dunes. Lower values were measured in the center and south of the lake. Measurements of total organic carbon (TOC), total nitrogen (TN), phosphorus concentrations, and TOC/TN ratios in three cores (QH01, QH02, and Z04) revealed four horizons corresponding to times of increased human activity. These anthropogenic events were (1) the development of large areas of cropland in the Lake Qinghai watershed in 1960, (2) the beginning of nationwide fertilizer use and increases in cropland area in the lake watershed after 1970, (3) the implementation of the national program "Grain to Green," and (4) the rapid increase in the tourism industry from 2000. Profiles of Rb, Sr concentrations, the Rb/Sr ratio, and grain-size fraction in core Z04 indicate that the climate has become drier over the past 100years. Therefore, we suggest that lake sediments such as those in Lake Qinghai are useful media for high-resolution studies of regional environmental change and human activity.

Hydrothermal alterations of the chemical composition in grain size fractions of sediments in the Guaymas Basin, Gulf of California

The paper presents data on the contents of macro- and microelements (rare earth elements included) determined in grain size fractions of the Upper Pleistocene hydrothermally altered and unaltered sediments from the Guaymas Basin (Gulf of California). Sediments subjected to high-temperature hydrothermal alteration were recovered by DSDP Hole 477A. In the finely dispersed fractions, which are mainly composed of clay minerals, alteration of the chemical composition was provoked by the hydrothermal transformation of terrigenous clay minerals. The concentration of microelements in these fractions takes place primarily at the cost of the hydrothermal finely dispersed ore minerals. Alteration of the chemical composition of the coarse-grained fractions is related to the replacement of clastogenic minerals by the secondary varieties and the formation of new minerals (including ore minerals and native metals) from the solutions. Hydrothermal alterations of the chemical composition of bulk samples depend on the degree of chemical element concentration in fractions and their content in samples.

Sediment characteristics and molluscan fossils of the Farasan Islands shorelines, southern Red Sea, Saudi Arabia

The Farasan Islands are located about 40 km offshore of Jizan area, southern Red Sea, Saudi Arabia. This is a preliminary study aiming to collect shoreline sediments from 17 stations to describe their main lithologic characters and identify the dominant molluscs that could help to evaluate the environmental conditions of these islands. Also, a sediment core FARA2 was collected from the intertidal area of Khor As Sailah Lagoon to see the development of shoreline sediments in this area with time. The results indicated that the shoreline sediments of the Farasan Islands comprised mainly of white, biogenic sand enriched in remains of corals, molluscs, calcareous algae, and benthic foraminifera. Thirty-four mollusc species were recorded from these sediments. Among them, Strombus fasciatus, Strombus tricornis, Chicoreus ramosus, Chicoreus virgineus, Tridacna maxima, and Tridacna squamosa were the most common molluscan in/near the shoreline sediments of Farasan Islands. Frequency abundances of sediment grain-size fractions in the core FARA2 indicated that the shoreline of the Khor As Sailah Lagoon is developing towards shallow intertidal setting due to high production of biogenic sediments by reefal communities. Metal concentrations (Fe, Mn, Cu, and Zn) in the sediment of the core FARA2 were stable throughout, showing no remarkable changes. This finding could indicate that flux of detrital components by fresh water runoff or wind-blown dust over the Farasan Islands was un-detectable during the deposition of these sediments.

Metal Contamination and Their Distribution in Different Grain Size Fractions of Sediments in an Industrial Development Area

Assessment of metal contamination and their distribution in different grain size fractions of the surface sediments of a lake in Kazipalli industrial development area has been investigated. Since the persistent toxic metals pose serious health risks, this research concentrated on investigating the concentrations and spatial distribution of metals in and around the Kazipalli Lake. Ten sampling points were selected and approximately 500 g of surface sediments were obtained from 1ft depth. Samples were sieved and four grain size fractions (>250, 110-250, 61-110, <61 μm) from each sample were selected for the analysis of metals. The average concentration of ten points for individual metals (As, Co, Cr, Cu, Ni, Pb and Zn) revealed data ranging from 9.6 to 131.4 mg/kg for As, 3.0-20.8 mg/kg for Co, 15.3-196 mg/kg for Cr, 13-40 mg/kg for Cu, 18-74 mg/kg for Ni, 51-328 mg/kg for Pb and 27-335.1 mg/kg for Zn. Enrichment factor and correlation analysis were also applied to the data set. The overall results indicate that sediment grain size played important role in controlling the distribution of heavy metals in surficial sediments of Kazipalli Lake.

Polycyclic aromatic hydrocarbon contamination and LUMIStox solvent extract toxicity of marine sediments in the North Aegean Sea, Greece.

Organic extracts of surface marine sediment collected from six sites within the bay of Kavala (north Aegean Sea, Greece) were used for determining priority pollutant polycyclic aromatic hydrocarbons (PAHs) and doing toxicity testing. PAH analyses and LUMIStox acute toxicity measurements were conducted in two sediment grain-size fractions: silt/clay (< 63 microm) and sand (63-2000 microm). Sixteen PAH concentrations were found at low- to moderate levels, ranging from 44 to 166 ng/g dry weight in the fine fraction and from 45 to 148 ng/g dry weight in the coarse fraction. Molecular indices revealed that PAHs in the bay sediment originate mainly from pyrolytic sources, but some petroleum influence was also evident. A comparison of sedimentary PAH levels with sediment quality guidelines (SQGs) indicated an absence of acutely toxic concentrations. However, all sediment extracts were found to be toxic with the LUMIStox acute toxicity test, with 15-min EC(50)s in the ranges of 1.0-4.0 and 1.1-4.5 mg of dry sediment/mL for the fine and the coarse fractions, respectively. No significant correlations between EC(50)s and concentrations of individual or total PAHs was found, suggesting that chemical analysis of PAHs alone cannot be considered a reliable indicator of sediment toxicity.

Sources of stream sediments in the granulite terrain of the Walawe Ganga Basin, Sri Lanka, indicated by rare earth element geochemistry

Thirty-eight samples of stream sediments draining high-grade metamorphic rocks in the Walawe Ganga (river) Basin, Sri Lanka, were analysed for their REE contents, together with samples of metamorphic suites from the source region. The metamorphic rocks are enriched in light REE (LREE) compared to heavy REE (HREE) and are characterised by high La/Lu ratios and negative Eu anomalies. The chondrite-normalised patterns for these granulite-grade rocks are similar to that of the average post-Archaean upper crust, but they are slightly enriched with La and Ce. The REE contents of the <63-μm fraction of the stream sediments are similar to the probable source rocks, but the other grain size fractions show more enriched patterns. The <63-μm stream sediments fraction contains lower total REE, more pronouncd negative Eu anomalies, higher Eu N/Sm N and lower La N/Lu N ratios relative to other fractions. The lower La N/Lu N ratio is related to the depletion of heavy minerals in the <63-μm fraction. The 63–125-μm and 125–177-μm grain size fractions of sediments are particularly enriched in LREE (average ΣLREE=2990 μg/g and 3410 μg/g, respectively). The total HREE contents are surprisingly uniform in all size fractions. However, the REE contents in the Walawe Ganga sediments are not comparable with those of the granulite-grade rocks from the source region of the sediments. The enrichment of REE is accounted for by the presence of REE containing accessory mineral phases such as zircon, monazite, apatite and garnet. These minerals are derived from an unknown source, presumably from scattered bodies of granitic pegmatites.

The distribution of radiocesium and plutonium in sea ice-entrained arctic sediments in relation to potential sources and sinks

Gamma counting of a range of grain size fractions of sediments entrained in Arctic Ocean sea ice indicate that the wide range of radiocesium activities that are observed in bulk samples are primarily a function of the geographical origin of the sediment, rather than mineral composition, or physical processes that increase the content of fine clays in sediments. Plutonium isotope ratios ( 240Pu: 239Pu) of sea ice sediments are consistent with an ultimate origin of the plutonium from bomb fallout ( 240Pu: 239Pu=∼0·18), and these sediment ratios differ significantly in plutonium isotope ratios from deep sea sediments of the Arctic Ocean. Much lower plutonium activities were observed in deep sea sediments relative to the sea ice entrained sediments. These differences in isotopic ratios indicate that on decadal scales, sedimentation of bomb fallout plutonium is not the sole source of plutonium to deep Arctic Ocean sediments. The large differences in total plutonium activity between some of the sea ice entrained sediments and all of the deep Arctic Ocean sediments also suggest that the total flux of plutonium from sea ice entrained sediments to the deep sea may be relatively small. Radiocesium activity in the sea ice entrained sediments is well correlated with total plutonium abundance, but the best-fit regression line does not pass through the origin, indicating that a small secondary source of cesium (3 to 9 Bq kg -1 dry weight) that is free of plutonium may contribute to the radiocesium activity observed in sediments entrained in Arctic Ocean sea ice. Based upon observations of carbon:nitrogen weight/weight ratios in excess of 20 in the organic carbon fraction, together with δ 13 C values less than −23%, several of the sea ice entrained sediments show indications of estuarine origin. However, these specific samples typically have low radionuclide burdens. Consideration of the low smectite content (<∼20% by weight) in all of the sea ice sediments and prevailing sea ice transport patterns suggest that a Siberian shelf origin west of the Lena River is improbable for any of the sea ice sediment samples. Nevertheless, in the absence of clear mechanisms for significantly increasing the radionuclide burden in sediments incorporated into sea ice, the radioactivity in the sediment source area appears to be the most crucial determinant of the ultimate radionuclide burden in sea ice sediments.

Modelling the dispersion of non-conservative radionuclides in tidal waters—Part 1: Conceptual and mathematical model

A 2D four-phase model to study the dispersion of non-conservative radionuclides in tidal waters, in conditions of disequilibrium for ionic exchanges, has been developed. At disequilibrium conditions, ionic exchanges cannot be formulated using distribution coefficients k d . Thus, kinetic transfer coefficients have been used. The model includes ionic exchanges among water and the solid phases (suspended matter and two grain size fractions of sediments), the deposition and resuspension of suspended matter and advective plus diffusive transport. In the second part of this work, which is presented in a separate paper, the model is applied to simulate 226Ra dispersion, discharged from a fertilizer processing plant, in an estuarine system in the south-west of Spain.

Origin, distribution and accumulation of organic carbon in the Skagerrak

Organic carbon contents have been determined in grain-size fractions of sediments from the Skagerrak southern slope and basin. C ORG concentrations were generally inversely related to grain size. The > 62; 63 μm fraction in surface sediments from deeper waters had higher contents attributable to agglutination of fine material by tube forming benthic organisms. Especially in the clay and fine silt fractions C ORG increased with increasing fraction content presumably as a result of higher “grazing pressure” on fine material in coarse sediments. A comparison of high resolution age ( 210Pb), porosity and grain-size composition profiles indicates that deviations in the 210Pb curves are due both to bioturbation and sedimentation events. Porosity profiles also show high regional variability on a small scale. When primary production, C ORG vertical fluxes and accumulation rates are compared an excess of organic carbon stored in Skagerrak sediments becomes apparent. Potential sources for this carbon such as river input, dumping or sea-floor erosion are examined.

Determination of the Origin of Suspended Matter and Sediments in the Elbe Estuary Using Natural Tracers

The clay mineral composition, the concentrations of carbonates, the proportions of carbon and oxygen isotopes in carbonates and organic matter, as well as the concentrations of different nonanthropogenic metals were used to determine the origin of different grain size fractions of sediments and suspended matter in the Elbe estuary. Analysis of the smectite/kaolinite proportion revealed that solid material ≤2 μm from the North Sea is transported up the river, about 40 km beyond the most upstream position of the salt wedge. In the 2–20 μm fraction, the16O/18O ratio in carbonates and the kaolinite/chlorite proportion demonstrate a transport of North Sea material between 40 and 20 km upstream of the marine water limit. The transport behaviour of the 20–63 μm grain size fraction could be determined by the hafnium concentration, representative for the heavy mineral zircon. In this case, the transport distance beyond the salt wedge was up to 20 km. No information was available on the origin of the fine organic matter, whereas the coarser fractions were derived primarily from debris of salt marsh vegetation. The results demonstrate that in the Elbe estuary mixing between marine and fluvial solid material occurs upstream of the salt wedge and is significantly responsible for the observed decrease in the concentration of various pollutants in sediments and suspended matter along the estuary. The cause of the upstream particle transport is probably a scour lag mechanism based on asymmetries of the flood- and ebb-tide current distribution, especially their differing maximum velocities.

Distribution of zinc, lead, cadmium and copper between different size fractions of sediments I. The Limski Kanal (North Adriatic Sea)

The distribution of zinc, cadmium, lead and copper in different grain-size fractions of sediment from the upper part of the Limski Kanal (North Adriatic Sea) has been studied. The results are discussed in relation to the textural, mineralogical and chemical characteristics of the sediments. Sediment particles <10 μm normally contained a high proportion of all studied metals. The coarser particles (> 63–300 μm), depending on the sampling site, incorporate metals in amounts similar to, or even higher than, the finest grains. Metal distributions are significantly correlated with the organic material in the sediments from the Limski Kanal. A significant difference was obtained for metal concentrations between sediments collected in June and December 1979.

Nutrition of Deposit-Feeding Holothuroids and Echinoids (Echinodermata) from a Shallow Reef Lagoon, Discovery Bay, Jamaica

Concentrations of organic carbon and nitrogen, ATP, and total plant pigment (chlorophyll a+ phaeophytin) were approximately twice as high in foregut contents of the deposit-feeding, aspidochirote holothuroids Isostichopus badionotus Selenka, Holothuria rnexicana Ludwig and H. arenicola Forskal, and spatangoid echinoids Meoma ventricosa Lamarck and Plagiobrissus grandis Gmelin than in the adjacent sediments. This suggests that holothuroids and spatangoids selectively ingest nutrient-rich grains, contrary to the conventional view that they show poor chemical discrimination. The availability of the organic food resources did not vary consistently between different grainsize fractions of sediment. This obviates any a priori expectation that discrimination on the basis of grain quality, demonstrated here, will be coupled to discrimination according to grain size, previously shown not to occur in these species. Assimilation efficiency of the ingested carbon averaged 42 %. Plant carbon, calculated from pigment concentrations and probably derived from diatoms, represented a major carbon resource in the available sediments, but only a small proportion of that ingested was apparently assimilated. Meiofauna, a minor component of the available carbon (ca. 1 %), were ingested in lower numbers than those at which they occurred in the sediment, and were not digested or assimilated. Bacterial biomass was not determined, but other studies suggest that its contribution to the sedimentary carbon pool is low. It is likely that at least half of the carbon assimilated by these deposit feeders is of detrital origin. This result, which contrasts with present understanding of the nutrition of deposit feeders, may be indicative of qualitative differences between detritus of coral reefs and that of other shallow, coastal ecosystems.