Sediment Partitioning Research Articles

Phosphorous partitioning in sediments by particle size distribution in shallow lakes: From its mechanisms and patterns to its ecological implications

This study revealed a general pattern of P partitioning onto sediment particles that has ecological implications for shallow lakes. Six individual sediment samples from two large shallow lakes in eastern China were sieved into five sediment particle size classes ranging from 0.5 μm to 50 μm. These particle size groupings were subjected to P fractionation and P adsorption isotherm analyses as well as bioavailable P bioassays. A P-adding experiment was used to validate the initial P partitioning onto the sediment particles. Multiple lines of evidence revealed that P partitioning onto the particles was dependent on the amounts of P adsorbents or P-containing compounds in the sediments, such as iron and aluminum oxides, organic matter, and calcium compounds. An exponential equation, c(x) = cmaxexp(−kdx), was proposed to describe the relationship between the partitioning of bioavailable P and particle size. In the equation, cmax represents the maximum P concentration adsorbed by the finest particles, and kd is a constant reflecting the decrease in the P concentration with particle size (x).

Collection and use of porewater data from sediment bioassay studies for understanding exposure to bioavailable metals.

The US Environmental Protection Agency Procedures for the Derivation of Equilibrium Partitioning Sediment Benchmarks (ESBs) for the Protection of Benthic Organisms: Metal Mixtures (Cadmium, Copper, Lead, Nickel, Silver and Zinc) equilibrium partitioning approach causally link metal concentrations and toxicological effects; they apply to sediment and porewater (i.e., interstitial water). The evaluation of bioavailable metal concentrations in porewater, using tools such as the biotic ligand model, provides an advancement that complements sediment-based evaluations. However, porewater characterization is less commonly performed in sediment bioassays than sediment chemistry characterization due to the difficulty and expense of porewater collection as well as concerns about interpretation of porewater data. This study discusses the advantages and disadvantages of different porewater extraction methods for analysis of metals and bioavailability parameters during laboratory sediment bioassays, with a focus on peepers and centrifugation. The purpose is to provide recommendations to generate bioassay porewater data of sufficient quality for use in risk-based decision-making, such as for regulated cleanup actions. Comparisons of paired data from previous bioassay studies indicate that metal porewater concentrations collected via centrifugation tend to be higher than those collected via peepers. However, centrifugation disrupts the redox status of the sediment; also, metal concentrations can vary markedly based on centrifugation conditions. Data to compare the concentrations of peeper- and centrifugation-collected bioavailability parameters (e.g., major ions, pH) are much more limited, but indicate smaller differences than those observed for metal concentrations. While peepers can be sampled without altering the redox status of the porewater, the small volume of porewater peepers collected is enough for metal concentration analysis, but insufficient for analysis of all metal bioavailability parameters. Given the benefits of metal collection via peepers, it is optimal to use centrifugation and peepers in tandem for bioassay porewater collection to improve bioavailability predictions. Environ Assess Manag 2022;18:1321-1334. © 2021 SETAC.

Occurrence and spatial-temporal distribution of atrazine and its metabolites in the aquatic environment of the Volturno River estuary, southern Italy

The present study assesses the spatial distribution and temporal trends of the water dissolved phase (WDP), suspended particulate matter (SPM) and sediment partitioning of atrazine (ATR) and its metabolites in the Volturno River estuary. The load contribution of ATR and its metabolites in this river to the Central Mediterranean Sea was estimated. Samples were collected in 10 sampling sites during the four seasons. The total concentrations of ATR and DPs detected ranged from 18.1 to 105.5 ng L−1 in WDP, from 4.5 to 63.2 ng L−1 in SPM, and from 4.6 to 18.6 ng g-1 in sediment samples, indicating high levels of these pollutants. Structural equation model and the ratio study indicated that the relationship between sediment and WDP pollutants occurred through the SPM. The pollutants load at the Volturno River in its mouth was evaluated in about 30.4 kg year-1, showing that this river is an important source of these analytes through discharge into Central Mediterranean Sea. Principal component analysis indicated that ATR and its metabolites pollution moves from Volturno River mouth southward and increased in the rainy season. The desethylatrazine-to-atrazine ratio was higher than 0.5 for all samples analyzed, indicating an historical discharge and a long residence time of ATR in sediment about two decades after its ban, and classifying ATR as a nonpoint source contaminant. This study makes up the first record of ATR and its metabolites in superficial water of Southern Italy and provides helpful data as starting point for future studies.

Sediment toxicity data and excess simultaneously extracted metals from field-collected samples: Comparison to United States Environmental Protection Agency benchmarks.

US Environmental Protection Agency (USEPA) Procedures for the Derivation of Equilibrium Partitioning Sediment Benchmarks (ESBs) for the Protection of Benthic Organisms: Metal Mixtures are based on the principle that metals toxicity to benthic organisms is determined by bioavailable metals concentrations in porewater. One ESB is based on the difference between simultaneously extracted metal (SEM) and acid volatile sulfide (AVS) concentrations in sediment (excess SEM). The excess SEM ESBs include a lower uncertainty bound, below which most samples (95%) are expected to be "nontoxic" (defined as a bioassay mortality rate ≤24%), and an upper uncertainty bound, above which most samples (95%) are expected to be "toxic" (defined as a mortality rate >24%). Samples that fall between the upper and lower bounds are classified as "uncertain." Excess SEM ESBs can, in principle, be improved by normalizing for organic carbon (OC). OC is a binding phase that reduces metals bioavailability. OC normalization should improve the accuracy of bioavailable metal concentration estimates, thus tightening uncertainty bounds. We evaluated field-collected sediments from 13 studies with excess SEM, OC, and bioassay data (n = 740). Use of the OC-normalized excess SEM benchmarks did not improve prediction accuracy. The ESB model predicts OC-normalized excess SEM exceeding the upper benchmark even when toxicity is not observed, because error in the OC normalization model increases at low OC concentrations. To minimize the likelihood of incorrectly identifying nontoxic samples as toxic, we recommend that OC normalization of excess SEM should not be considered for sediments with an OC concentration <1% and is questionable for sediments with an OC concentration of 1%-4%. Additional focused studies are needed to confirm or refine the minimum sediment OC concentrations that are applicable for reducing uncertainty in toxicity predictions due to excess SEM. Integr Environ Assess Manag 2022;18:174-186. © 2021 SETAC.

Timescale dependent sedimentary record during the past 130 kyr from a tropical mixed siliciclastic–carbonate shelf edge and slope: Ashmore Trough (southern Gulf of Papua)

AbstractIn tropical and sub‐tropical mixed siliciclastic–carbonate depositional systems, fluvial input and in situ neritic carbonate interact over space and time. Despite being the subject of many studies, controls on partitioning of mixed sediments remains controversial. Mixed sedimentary records, from Ashmore Trough shelf edge and slopes (southern Gulf of Papua), are coupled with global sea‐level curves and anchored to Marine Isotope Stage stratigraphy to constrain models of sediment accumulation at two different timescales for the past 130 kyr: (i) 100 kyr scale for last glacial cycle; and (ii) millennial scale for last deglaciation. During the last glacial cycle, carbonate production and accumulation were primarily controlled by sea‐level fluctuations. Export of neritic carbonate to the slopes was initiated during re‐flooding of previously exposed reefs and continued during Marine Isotope Stage 5e and 1 interglacial sea‐level highs. Siliciclastic fluxes to the slope were controlled by interplay of sea level, shelf physiography and oceanic currents. Heterogeneous accumulation of siliciclastic mud on the slope, took place during Marine Isotope Stage 5d to Marine Isotope Stage 3 sea‐level fall. Siliciclastics reached adjacent depocentres during Marine Isotope Stage 2. Coralgal reef and oolitic–skeletal sand resumed at the shelf edge during the subsequent stepwise sea‐level rise of the last deglaciation. Contemporaneous, abrupt siliciclastic input from increased precipitation and fluvial discharge illustrates that climate controlled deglacial sedimentation. Siliciclastic input persisted until ca 8.5 ka. Carbonate accumulation waned at the shelf edge after ca 14 ka, whereas it increased on the slopes since ca 11.5 ka, when previously exposed reef and bank tops were re‐flooded. When comparing the last sea‐level cycle sedimentation patterns of the southern Gulf of Papua with other coeval mixed systems, sea level and shelf physiography emerge as primary controls on deposition at the 100 kyr scale. At the millennial scale, siliciclastic input was also controlled by climate change during the unstable atmospheric and oceanic conditions of the last deglaciation.

Toxicity evaluation of Louisiana nearshore marsh sediments following the Deepwater Horizon oil spill

A crucial step towards understanding potential impacts of the Deepwater Horizon oil spill to marsh ecosystems was to quantitatively determine the toxicity of oil remaining in the sediment. The objective of this study was to assess the potential injury to benthic species using standardized toxicity bioassays. Sediments were collected from locations with differing degrees of oiling based on previous assessments. Less than 13% of the 315 toxicity tests resulted in toxicity to amphipods, mysid shrimp, or sea urchins. There was no relationship among toxicity test results, oiling category or measured total polycyclic aromatic hydrocarbons (PAHs). Equilibrium partitioning sediment benchmarks and additive toxic units (ESBTUs) were applied as an additional line of evidence to evaluate the potential adverse effects based on PAH concentrations in field sediments. The ∑ESBTUs based on 34 PAHs at the 64 nearshore sampling locations were <1, indicating PAHs in sediments were unlikely to cause adverse impacts.

Shoreline trajectory and stratal stacking patterns: Relation to sediment partitioning and types of deep-lacustrine deposits

This study utilizes drilling data to investigate shoreline trajectory, associated stratal stacking patterns and their relationships to sediment partitioning within the Lower Triassic in the Mahu Sag, northwestern Junggar Basin. Accretionary transgression occurred with changing of shoreline trajectory, sediment partition and basin-margin morphology. Two main types of shoreline trajectory and their associated stratal stacking patterns were recognized: (1) slightly rising trajectory, which has low trajectory angle (0.065°–0.072°) and is associated with retrogradational to aggradational back-stepping stacking patterns with low slope relief, and (2) moderately rising trajectory, which has relatively higher trajectory angle (0.09°–0.27°) and is associated with aggradational to retrogradational stacking patterns with moderate slope relief. The rising shoreline trajectory is associated with a fan-delta system with facies belts that migrate landward and are fining-upward, which is characterized by thick plain and thin front architecture. In vertical, the ascending trajectory developed with upward decreasing of sediment grain-size, muddy matrix changed to sandy matrix and even changed to clast supported in conglomerates. In planar, shoreline trajectory angle variations exist associated with different delta-front processes and different prodelta/deep-lacustrine deposits. Shoreline trajectory angle variations generated by sediment partition represents the relations between aggradation and retrogradation which determines the basin-margin growth pattern and morphology. It also indicates the vertical succession of basin-margin deposits and the preservation potential of deposits generated in various depositional environments. The results of this study show that shoreline trajectory could be a good indicator for basin-margin process and reservoir interpretation.

Biodegradation of third-generation organic antifouling biocides and their hydrolysis products in marine model systems

The environmental fate for some selected antifouling biocides, dichlofluanid, tolylfluanid, tralopyril, and medetomidine, is relatively poorly understood with nearly all data derived from the assessment reports. Water/sediment systems and biofilms were used to determine biodegradation of the antifouling biocides. Dichlofluanid and tolylfluanid are known to hydrolyze to form DMSA (N,N-dimethyl-N′-phenylsulfamide) and DMST (N,N-Dimethyl-N′-(4-methylphenyl)sulfamide), respectively. DMSA did not show biodegradation, but it was shown to transform abiotically into N,N-dimethylsulfamide (N,N-DMS). In contrast, the structurally similar DMST did show biodegradation with a half-life of 5.78 days. The resulting transformation product of the biodegradation of DMST is also N,N-DMS. N,N-DMS accounted for the majority of the mass balance after 27 days in the water/sediment systems. Moreover, the biofilm systems also degraded both DMSA and DMST to N,N-DMS. The hydrolysis product of tralopyril, called BCCPCA (3-bromo-5-(4-chlorophenyl)−4-cyano-1 H-pyrrole-3-carboxylic acid), was not metabolized in the experiments and remained persistent. For this compound, a new log Kow of 2.47 was determined since the previously reported Kow value seemed to overestimate sediment partitioning. Medetomidine was removed from the water/sediment system, though, not significantly more than the control. However, a transformation product (medetomidine-acid) was detected in the incubation but not in the control, pointing to limited biodegradation. These results show that tolylfluanid can be rapidly removed by biodegradation in the marine environment, while dichlofluanid, tralopyril, and medetomidine remained in the system for a longer period of time. The prolonged stability of these biocides could mean that there is potential for accumulation in the environment. This potential is also there for the DMSA (dichlofluanid) and DMST (tolylfluanid) derived transformation product N,N-DMS, which was recalcitrant.

Predicting Water and Sediment Partitioning in a Delta Channel Network Under Varying Discharge Conditions

AbstractChannel bifurcations control the distribution of water and sediment in deltas, and the routing of these materials facilitates land building in coastal regions. Yet few practical methods exist to provide accurate predictions of flow partitioning at multiple bifurcations within a distributary channel network. Herein, multiple nodal relations that predict flow partitioning at individual bifurcations, utilizing various hydraulic and channel planform parameters, are tested against field data collected from the Selenga River delta, Russia. The data set includes 2.5 months of time‐continuous, synoptic measurements of water and sediment discharge partitioning covering a flood hydrograph. Results show that width, sinuosity, and bifurcation angle are the best remotely sensed, while cross‐sectional area and flow depth are the best field measured nodal relation variables to predict flow partitioning. These nodal relations are incorporated into a graph model, thus developing a generalized framework that predicts partitioning of water discharge and total, suspended, and bedload sediment discharge in deltas. Results from the model tested well against field data produced for the Wax Lake, Selenga, and Lena River deltas. When solely using remotely sensed variables, the generalized framework is especially suitable for modeling applications in large‐scale delta systems, where data and field accessibility are limited.

Trace metal dynamics in an industrialized Brazilian river: A combined application of Zn isotopes, geochemical partitioning, and multivariate statistics

The Paraiba do Sul (PSR) and Guandu Rivers (GR) water diversion system (120 km long) is located in the main industrial pole of Brazil and supplies drinking water for 9.4 million people in the metropolitan region of Rio de Janeiro. This study aims to discern the trace metals dynamics in this complex aquatic system. We used a combined approach of geochemical tools such as geochemical partitioning, Zn isotopes signatures, and multivariate statistics. Zinc and Pb concentrations in Suspended Particulate Matter (SPM) and sediments were considerably higher in some sites. The sediment partition of As, Cr, and Cu revealed the residual fraction (F4) as the main fraction for these elements, indicating low mobility. Zinc and Pb were mostly associated with the exchangeable/carbonate (F1) and the reducible (F2) fractions, respectively, implying a higher susceptibility of these elements to being released from sediments. Zinc isotopic compositions of sediments and SPM fell in a binary mixing source process between lithogenic (δ66/64ZnJMC ≈ + 0.30‰) and anthropogenic (δ66/64ZnJMC ≈ + 0.15‰) end members. The lighter δ66/64ZnJMC values accompanied by high Zn concentrations in exchangeable/carbonate fraction (ZnF1) enable the tracking of Zn anthropogenic sources in the studied rivers. Overall, the results indicated that Hg, Pb, and Zn had a dominant anthropogenic origin linked to the industrial activities, while As, Cr, and Cu were mainly associated with lithogenic sources. This work demonstrates how integrating geochemical tools is valuable for assessing geochemical processes and mixing source effects in anthropized river watersheds.

Flow and sediment behaviours and morpho‐dynamics of a diffluence−Confluence unit

AbstractA diffluence‐confluence unit is an elementary component within a river system and presents a complex yet linked pattern of both flow and sediment transport in between. This study deals, by means of field investigations and numerical modelling, with morpho‐dynamics of such a unit on the lower Yangtze River reaches. The unit comprises, looking downstream, a secondary (left) course and a main (right) course. Field surveys are performed for measurements of flow discharge, sediment loads at selected locations and river bathymetry at certain intervals. The field data show that the reach is mainly composed of suspended load, whose amount exhibits a declining trend with the elapse of time. Simulations in 3D are made to complement the field data and clarify the basic features of the unit, especially the partitioning of flow and suspended sediment in the diffluence and their subsequent reciprocal adjustment in the confluence. The results indicate that approach flow variations have a bearing on the diffluence flow partition. To augment flow discharge in the left branch, a training wall is devised in the diffluence to modify the intake flow. Secondary flow structures are found to be more influenced by the thalweg curvature than the flow division. The “inlet step” or differential topography contributes to the unequal flow division. In the confluence, a two‐cell flow structure coexists, which may diminish along with the dynamical adjustment of the two waters. The classical bed discordance is also observed. With the typical flow and sediment features, the main course is prone to slight erosion, while the secondary branch faces up with gradual siltation. These findings contribute to the understanding of the alluvial behaviours of such units, and provide reference for studies in similar situations and river management.

Behavior of metallurgical zinc contamination in coastal environments: A survey of Zn from electroplating wastes and partitioning in sediments

The contamination of coastal environments by metallurgical wastes involves multiple biogeochemical processes; accordingly, understanding metal behavior and risk evaluation of contaminated areas, such as Sepetiba Bay (Rio de Janeiro, Brazil), remains challenging. This study coupled Zn isotopic analyses with sequential extractions (BCR) to investigate the mechanisms of Zn transfer between legacy electroplating waste and the main environments in Sepetiba Bay. This metallurgical waste showed a light bulk isotopic signature (δ66/64ZnbulkJMC = +0.30 ± 0.01‰, 2 s, n = 3) that was not distinct from the lithogenic geochemical baseline, but was different from signature of mangrove sediment considered as anthropogenic end member (δ66/64ZnJMC = +0.86 ± 0.15‰) in a previous isotopic study in this area. Zn isotopic compositions of sediment samples (ranging from +0.20 to +0.98‰) throughout the bay fit a mixing model involving multiple sources, consistent with previous studies. In the metallurgic zone, the exchangeable/carbonate fraction (ZnF1) exhibited high Zn concentrations (ZnF1 = 9840 μg g−1) and a heavy isotopic composition (δ66/64ZnF1JMC = +1.10 ± 0.01‰). This finding showed that, in some cases, the bulk isotopic signature of waste is not the most relevant criterion for evaluating trace metal dispersion in the environment. Indeed, based on the BCR, it was observed that part of the anthropogenic metallurgical Zn was redistributed from the exchangeable/carbonate fraction in the waste to the surrounding mangrove sediment. Then, this contaminated sediment with heavy δ66/64Zn values was exported to other coastal environments. In Sepetiba Bay, contaminated sediments revealed a large concentration of ZnF1 fraction (up to 400 μg g−1) with a heavy Zn isotopic signature. This signature also matched the Zn isotopic signature of oysters in Sepetiba Bay reported by other studies; hence, measurement of the isotopic exchangeable/carbonate fraction has important implications for tracing the transfer of anthropogenic Zn to biota.

Tidal amplification and along‐strike process variability in a mixed‐energy paralic system prograding onto a low accommodation shelf, Edgeøya, Svalbard

AbstractThe study describes the depositional development and sediment partitioning in a prograding paralic Triassic succession. The deposits are associated with the advance of large prism‐scale clinoforms across a shallower platform area. Approaching the platform, the limited accommodation and associated relative higher rates of deposition generated straighter clinoforms with lower foreset angles. The vertical restriction across the platform is interpreted to have amplified the tidal signature. Sediment was redistributed from the coast into increasingly sandy delta‐front deposits, compared to offshore equivalents. The deposits comprise extensive compound dune fields of amalgamated and increasingly clean sandbodies up‐section. Rapid deposition of significant amounts of sand led to differential subsidence and growth‐faulting in the delta front, with downthrown fault blocks further amplifying the tidal energy through funnelling. A mixed‐energy environment created along‐strike variability along the delta front with sedimentation governing process‐regime. Areas of lower sedimentation were reworked by wave and storm‐action, whereas high sedimentation rates preserved fluvially dominated mouth bars. A major transgression, however, favoured tidally dominated deposits also in these areas, attributed to increasing rugosity of the coastline. Formation of an extensive subaqueous platform between the coast and delta front dampened incoming wave energy, and tidally dominated deposits dominate the near‐shore successions. Meanwhile formation of wave‐built sand‐bars atop the platform attest to continued wave influence. The strong tidal regime led to the development of a heterolithic near‐shore tidally dominated channel system, and sandier fluvial channels up‐river. The highly meandering tidal channels incising the subaqueous platform form kilometre wide successions of inclined heterolithic stratification. The fluvially dominated channels which govern deposition on the delta plain are narrower and slightly less deep, straighter, generally symmetric and filled with cleaner sands. This study provides important insight into tidal amplification and sand redistribution during shallowing on a wide shelf, along with along‐strike process‐regime variability resulting from variations in sediment influx.

Primary Sources of Polycyclic Aromatic Hydrocarbons to Streambed Sediment in Great Lakes Tributaries Using Multiple Lines of Evidence.

Polycyclic aromatic hydrocarbons (PAHs) are among the most widespread and potentially toxic contaminants in Great Lakes (USA/Canada) tributaries. The sources of PAHs are numerous and diverse, and identifying the primary source(s) can be difficult. The present study used multiple lines of evidence to determine the likely sources of PAHs to surficial streambed sediments at 71 locations across 26 Great Lakes Basin watersheds. Profile correlations, principal component analysis, positive matrix factorization source‐receptor modeling, and mass fractions analysis were used to identify potential PAH sources, and land‐use analysis was used to relate streambed sediment PAH concentrations to different land uses. Based on the common conclusion of these analyses, coal‐tar–sealed pavement was the most likely source of PAHs to the majority of the locations sampled. The potential PAH‐related toxicity of streambed sediments to aquatic organisms was assessed by comparison of concentrations with sediment quality guidelines. The sum concentration of 16 US Environmental Protection Agency priority pollutant PAHs was 7.4–196 000 µg/kg, and the median was 2600 µg/kg. The threshold effect concentration was exceeded at 62% of sampling locations, and the probable effect concentration or the equilibrium partitioning sediment benchmark was exceeded at 41% of sampling locations. These results have important implications for watershed managers tasked with protecting and remediating aquatic habitats in the Great Lakes Basin. Environ Toxicol Chem 2020;39:1392–1408. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Quantifying sand delivery to deep water during changing sea‐level: Numerical models from the Quaternary Brazos Icehouse continental margin

AbstractSequence stratigraphy for clastic continental margins predicts the development of sand‐rich turbidite deposits during specific times in relation to base‐level cycles. It is now widely understood that deltas can extend to the shelf‐edge forced by high sediment flux and/or base level, providing a direct connection to transfer sediment and sand to the slope and basin floor even during high base level periods. Herein, we build a stratigraphic forward model for the last 120 kyr of the fluvio‐deltaic to deep‐water Brazos system (USA) where sediment partitioning along an Icehouse continental margin can be evaluated. The reduced‐complexity stratigraphic forward model employs geologically constrained input parameters and mass balance. The modelled architecture is consistent with the location of depositional units previously mapped in the shelf. Sand bypasses the shelf and upper slope between 35 to 15 kyr before present and only about 20%–30% of all the sediment and sand supplied to the system is transferred to deep water. Several scenarios based on the initial Brazos model investigate the relationships between base level and deep‐water sand ratio (DWSR). DWSR is defined as the relative amount of sand transferred to the deep‐water portions of the system subdivided by the total sand input to the model. Linear correlations between DWSR and base level change rates or base level are very poor. Short‐term variability due to local processes (for example avulsions) is superimposed to the long‐term trends and mask the base level signal. DWSR for an entire base‐level cycle is mainly controlled by the proportion of time the delta stays docked at the shelf‐edge. Stratigraphic forward models are useful to complement field observations and quantify how different processes control stratigraphy, which is important for making predictions in areas with limited information.

Tectono-sedimentary characteristics in the area with distributed normal faults: Lower Cretaceous Prosopis Formation in the northern slope of Bongor Basin, Chad

Based on an integrated database (e.g., core observations, well logs, and seismic data), the characteristics of depositional systems, as well as the response to tectonics, are systemically delineated in the Prosopis Formation of the Lower Cretaceous at Bongor Basin, Chad. The tectonic setting of this study area experienced multiple, active sub-basins with narrow-spaced intra-basinal normal faults. The multiple normal faults formed in the initial rifted stage leading to the development of a corridor-shaped basin consisting of small-scale sub-basins. As this basin is attracting increased attention due to further hydrocarbon exploration, deciphering the process of sediment partition, especially in the initial rifted stage, would provide a further understanding of the tectono-sedimentary evolution in lacustrine rift basins. Based on core observations, well logs, and three-dimensional seismic data, fan-delta and sub-lacustrine-fan depositional systems are widely developed in this area. Two depositional systems (e.g., fan-delta and sub-lacustrine-fan) and three categories of slope break belts (single-faulted, step-faulted, and flexure types) have been identified. Overall, during the initial rifted stage, the formation of multiple normal faults mainly dominates the geomorphology and sediment supplies that generate the spatio-temporal features of depositional systems in semi-closed lacustrine basins. Climatic perturbations, furthermore, regulated the composition of sediments (coarse versus fine deposits). For the economic perspective, this study highlights the significance of fault systems in further hydrocarbon exploration during the initial rifted stage of lacustrine basins.

Sequential extraction studies on the river Tisa sediments for the assessment of the metal pollution

The sequential extraction procedure was applied for partitioning of metals in river sediments collected along the course of the river Tisa (Serbia). Eight elements (Sb, Sn, As, Cd, Cu, Hg, Pb and Zn) from twenty-one sampling site were analyzed using the modified BCR sequential extraction procedure in combination with ICP-OES. The results of sequential extraction, statistical analyses and calculation of EF and lithogenic and anthro?pogenic ratio of metals are similar. In the river Tisa sediments Sn, Cd, Hg, Pb and Zn are of anthropogenic origin, while As, Cu and Sb are of lithogenic and anthropogenic origin. The sediments from the river Tisa show high risk for Cd, medium risk for Hg and Zn, low risk for Sn, As, Cu and Pb, whereas Sb does not show the risk for the aquatic environment.

Modelling scenarios of environmental recovery after implementation of controls on emissions of persistent organic pollutants.

Comparison of monitoring data with toxicologically-derived environmental quality standards (EQSs) forms the basis of assessments of the quality status of the water environment. Having established the status quo, the logical next step is to address instances of non-compliance with EQSs by applying remedial measures, including reducing the use or at least the emission of the substances of concern or by taking steps to reduce concentrations already present using technological solutions such as enhanced wastewater treatment. The selection of suitable remedial measures must be a compromise between cost, likely effectiveness and the timescale over which improvements might be acceptable. The decision on overall environmental management has also to take into account the need for demonstrable progress; this might mean that it is preferable to address some more readily achievable goal rather than to attempt to solve a more serious, but ultimately intractable problem. This paper describes the development and application of a generic modelling tool that provides a way of assessing the potential requirements for remedial actions and their likely outcomes over a timescale of up to forty years taking account of sediment partitioning, environmental degradation and biological accumulation. The tool was validated using a detailed UK wastewater treatment works effluent discharge dataset. Examples involving several chemicals that are of current concern are provided. Some substances (e.g. tributyltin, PFOS) are identified as likely to meet EQS values in sediments or biota in a relatively short timescale; others (PAHs, DEHP) appear to represent more intractable problems.

Alternating of aggradation and progradation dominated clinothems and its implications for sediment delivery to deep lake: The Eocene Dongying Depression, Bohai Bay Basin, east China

Abstract Sediment routing in deep-water settings can be significantly different in lacustrine basins from their well-studied marine counterparts, which has been largely overlooked during the past decades. The seismically well-imaged lacustrine clinothems in the Eocene Dongying Depression provide a good opportunity to bridge the deep-water sediment partitioning with clinothem architecture and shelf-edge trajectories, which have been studied through the integration of 3D seismic data and well-logging data. In the study area, the Eocene delta-complexes are architecturally manifested as alternating aggradation dominated (AC) and progradation dominated clinothems (PC). The Eocene Dongying clinothem architecture has been documented in terms of shelf–edge trajectory angle (θsht), edge-to-toe distance (ETT), aggradation height (Ah), progradation distance (Pd) and maximum foreset angle (γmfa). Aggradation dominated clinothems are characterized by ascending shelf-edge trajectories with thick and widespread sand-prone bottomsets, suggesting higher efficiency of sediment delivery into the outlying lake floor. Progradation dominated clinothems, in contrast, are characterized by flat to slightly descending trajectories and generally by a lack of bottomsets. Alternations of rising and flat to slightly descending trajectories accompanied with different clinothem types probably indicate frequent relative lake level changes (on time-scales of 100s of kyr). Further analysis of seismic images and extensive well-logs suggest the distal aggradational bottomsets are generally consist of sub-lacustrine channel-lobe systems, whereas sediment slide, slump blocks occur in slope to slope toe areas of progradation dominated clinothems, which indicate varied processes of deep-water sediment transport associated with different clinothem types and shelf-edge trajectories. Lake-level, sediment supply, water salinity and density change induced by humid-arid climate cycle are suggested to be main factors controlling clinothems stacking pattern and sediment dispersal into deep-lacustrine. Humid climate are considered to be related with strongly aggradational clinothems, during which sediment can be directly transported to the distant bottomset areas due to increased sediment concentration and energy in river discharge. Whereas during dry periods, progradation dominated clinothems start to build under stillstand or falling lake level conditions, sediment generally accumulates at river mouth and collapses due to sediment overload or fault activity. Therefore, a relationship between deep-lacustrine depositional process and climatic signature was established which may provide new thoughts in both the study of deep-water sequences and deep-water exploration in lacustrine basins.

Seawater, biota and sediment partitioning of 137Cs in the east coast of Peninsular Malaysia

Partitioning of 137Cs between marine compartments in the east coast of Peninsular Malaysia was studied with the objectives were to quantify the level of 137Cs in seawater, biota and sediment and to assess its partition coefficient of CF and Kd. The results found the level of 137Cs were low in all type of samples and seems to be not significant. Therefore, this can be concluded that the levels of 137Cs in those samples remain in the background level and there is no new input of 137Cs into this region. Moreover, the evidence discussed in this work is reasonable to highlight the possible reasons or factors affecting the partitioning of 137Cs in seawater, sediment and its accumulation in biota as well as its CF and Kd.