Sediments

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Recruitment is essential for the maintenance of populations, but far more is typically known about the more easily-observed adult stages than their smaller, often microscopic early life-history counterparts. This discrepancy can be particularly problematic for populations of foundation species that create biogenic habitat for a multitude of other taxa, but are themselves prime candidates for exploitation, fragmentation, and loss, and therefore become the focus of restoration eVorts partly or fully dependent on recruitment. The purpose of this study was to improve ecological understanding for early life-history stages of the habitat-forming marine alga Cystoseira barbata (Stackhouse) C. Agardh (Fucales: Sargassaceae), member of a genus that has experienced considerable fragmentation and population decline on European coasts. Using experimental manipulations of water temperature, light intensity, and sediment accumulation, we observed that sediment virtually precluded recruitment of C. barbata, and greatly impacted the survival of recently settled germlings (up to »83% mortality). Stronger intensities of light facilitated the growth of germlings, including the capacity for »50% of them to outgrow detrimental sediment and survive. Temperature (10 vs. 16°C) had no eVect on early recruitment, survival, or growth. This information helps to identify likely causes and locations of recruitment failure, and by extension, the conditions needed (either naturally or through human intervention) to facilitate recruitment and possible habitat restoration. Ultimately, this knowledge can increase our capacity to predict population persistence and the likely success of restoration eVorts. Communicated by S. D. Connell.

We investigated the sediment-related distribution of both nematodes and macrofauna on the Belgian part of the North Sea (Southern Bight of the North Sea) in order to evaluate whether both faunal groups reflect similar patterns in community composition and diversity. Fine-grained sediments (median grain size <200 mm) were inhabited by nematode communities characterised by a low diversity and dominated by non-selective deposit-feeding nematodes. Nematode communities from coarser sediments were significantly different in terms of community composition and diversity. Moreover, all nematode feeding types were present in coarser sediments. These differences were explained by the contrasting biogeochemical processes prevailing in both sediment types, rather than granulometry and food availability per se. Macrofaunal distribution patterns were different from those of the nematode communities and seem to be related to water column processes (SPM loading, food availability, hydrodynamic stress) that promote the establishment of diverse communities in the coarser sediments but not in the finest sediments. This suggests that data on nematodes and macrofauna reveal different, complementary aspects of the factors structuring the benthic ecosystem that can be of importance in assessing the ecological status of the seafloor.

The European beaver Castor fiber is well-known as an ecosystem engineer that greatly affects landscape structure, biodiversity as well as physical and chemical properties of surface water bodies. Beaver ponds alter surface water bodies by raising water elevation, decreasing flow velocity and altering the morphology of streams or drainage ditches, which can reduce the concentrations of organic carbon (OC) and nutrients (N, P). Recent studies indicated that mercury transforms into hazardous and neurotoxic methylmercury (MeHg) in beaver impoundments by biological processes in anaerobic conditions. However, the knowledge about nutrients and MeHg levels in impounded forest waterbodies is scarce in Lithuania. We aimed to ascertain the alteration in concentrations and stocks of OC, nutrients and MeHg in water and sediments from upstream and downstream, as well as within beaver dams and ponds during the growing seasons of 2016–2018. Results showed higher concentrations of dissolved organic carbon (DOC) and nutrients (P and N) in upstream water samples compared to those of downstream from beaver dams. Meanwhile, in sediments mean stocks of OC, P and N were the highest in the middle part of the ponds and in beaver dams. Moreover, the concentrations and stocks of MeHg in sediments were higher in beaver dams than in any other parts of beaver impoundments (upstream, mid-pond, pond periphery and downstream). We conclude that dam bottom sediments were rich in OC, N and P, and at the same time, contained toxic MeHg. Therefore, beaver dams could act as a trickle filter by improving water quality, in our case, DOC, N and P leaching, from riparian forests and soils, but may also act as hotspots of mercury methylation.

Slit-check dams are widely employed in mountain river control. However an analysis of their performance in the field is still lacking. In the present work a field verification to evaluate the interaction between solid discharge regime and four slit-check dams built in two subcatchments of ...

Measurement of seafloor microtopography is rapidly approaching the status as a standardized element of geoacoustic characterization of the sea floor. With the advent of underwater stereo cameras and, recently, multiple-megapixel digital cameras adapted for underwater use, more investigators are measuring seafloor roughness at high resolution for applications to high-frequency acoustic modeling. An assessment of the methodologies used to characterize seafloor roughness, the parameterizations of the characterization of seafloor roughness, and the predictability of seafloor roughness seems appropriate at this time. Use of the roughness power spectrum to characterize seafloor roughness has a wide applicability for acoustic modelers. Currently, the slope and intercept of the regression line through the roughness power spectrum are used to parameterize seafloor roughness for acoustic modeling. Recent availability of digital roughness height datasets allows computation of two-dimensional roughness power spectra at sub-cm resolution. Ideally, these 2-D spectra would make the estimation of 2-D roughness parameters from 1-D roughness parameters unnecessary. Although much seafloor microtopography has been characterized concomitantly with sediment grain size, empirical prediction of roughness from grain size remains problematic. The inherent problem in relating seafloor roughness parameters to grain size is that the sediment-water interface is dynamic. Although seafloor microtopography may be thought to evolve predictably through cycles driven by hydrodynamic and biological processes, the rates of these processes and the resultant bedforms are highly variable. Another aspect of seafloor roughness that needs to be addressed is the character of its power spectrum over several orders of magnitude of spatial dimensions.

One of the primary challenges of the Water Framework Directive (WFD) of the European Union is to provide a guide for the recovery of surface waters from pollution. However, few studies deal with reference conditions according to the WFD in coastal waters. Using the urbanised Laajalahti Bay (Helsinki, Finland) as an example, reference conditions and pollution history were defined using the stratigraphy of diatoms, sediment geochemistry, stable isotopes, sedimentary pigments, long-term monitoring results of water quality, and nutrient-loading. Principal components analysis was used to generate a multidimensional index of water quality on the basis of the sediment data. We distinguished 5 phases: (1) a pre-industrial phase (before ca. 1815); (2) a phase of slight human disturbance (ca. 1815 to 1900); (3) an onset of anthropogenic impact (ca. 1900 to 1955); (4) a severe pollution phase (ca. 1955 to 1975); (5) basin recovery and a phase of internal loading (from ca. 1975 onwards). Phase 2 was used to define reference conditions. Phase 1 was not used as it occurred before the formation of the semi-enclosed bay by post-glacial isostatic land-uplift. There was good agreement between the sedimentary record and the water-quality data during Phase 4. Despite an improvement in water quality after the local municipal treatment plant closed in 1986, Laajalahti Bay is still far from reference conditions due to internal loading.

Polycyclic aromatic hydrocarbon (PAH) concentrations in 34 surface sediments along the Susquehanna River were investigated in 2000. The total concentrations of PAHs in the surface sediments of Lake Clarke, Lake Aldred, the upper Conowingo Reservoir, and the lower Conowingo Reservoir were 3.3 ± 1.5 lg g À1 (n = 9), 1.6 ± 1.3 lg g À1 (n = 4), 9.8 ± 5.5 lg g À1 (n = 7), and 4.0 ± 1.2 lg g À1 (n = 14), respectively. These represent the first comprehensive measurement of PAHs in Susquehanna River surface sediments. Overall, total PAH concentrations were relatively lower in Lake Aldred, which is more shallow and sloped, and significantly higher in the upper Conowingo Reservoir. The sediment PAH levels were related to river flow rates, which are indirectly correlated with the particle size of the surface sediments. Total PAH levels in all the studied sites were below the effects range median (ERM) of 44.8 lg g À1 with 38% (13 of the 34 sampling sites) exceeding the effects range low (ERL) of 4.02 lg g À1 . Principal component analysis indicated that variations in the PAH compound patterns of each reservoir decreased from upstream to downstream, indicating that the surface sediments were mixed along the Susquehanna River. The PAH patterns in the lower Conowingo Reservoir sediments were a combination of those upstream sources. Source analysis using isomer ratios as indicators suggested that PAHs in the Susquehanna River surface sediment are derived from the combustion of fossil fuels such as coal and gasoline with coal as the major source of contaminants.

Two high performance flow atomic absorption (HPF-AAS) related techniques were chosen to assess their suitability for the determination of several trace elements in complex environmental and biological samples. The technique selected were the Hydraulic High Pressure Nebulization Atomic Absorption Spectrometry (HHPN-AAS), and the Hydraulic High Pressure Nebulization Flame Furnace Atomic Absorption Spectrometry (HHPN-FF-AAS), which were applied directly, or after using off line liquid-liquid separation-preconcentration-back extraction procedures. Analytical methodologies were developed for Be, Sr, Ba, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Cd, Ag, Al, Tl, Pb, and Bi, for a variety of samples such as river and seawater, river and marine sediments, soft tissue of mussels, tunicate siphons, aquatic plants, and human samples of clinical interest such as placentas, umbilical cords, and cardiovascular tissues from surgical procedures. The analytical efficiency of the techniques was also proved in a proposed trace metal fractionation approach for river and seawater samples. All samples collected in this work were obtained from the North of Chile, where the most important economic activity is the mining industry.

This paper reviews research that has taken place on physical oceanography and sedimentology on New Zealand's estuaries and the inner shelf since c. 1967. It includes estuarine sedimentation, tidal inlets, beach morphodynamics, nearshore and inner shelf sedimentation, tides and coastal currents, numerical modelling, short-period waves, tsunamis, and storm surges. An extensive reference list covering both published and unpublished material is included. Formal teaching and research programmes dealing with coastal landforms and the processes that shape them were only introduced to New Zealand M91078

Widespread drought and record maximum temperatures in eastern Australia produced a large dust storm on 23 October, 2002 which traversed a large proportion of eastern Australia and engulfed communities along a 2000 km stretch of coastline from south of Sydney (NSW) to north of Mackay (Queensland). This event provided an opportunity for a study of the impacts of rural dust upon the air quality of four Australian cities. A simple model is used to predict dust concentrations, dust deposition rates and particle size characteristics of the airborne dust in the cities. The total dust load of the plume was 3.35 to 4.85 million tones, and assuming a (conservative) plume height of 1500 m, 62-90% of this dust load was deposited in-transit to the coast. It is conservatively estimated that 3.5, 12.0, 2.1 and 1.7 kilotonnes of dust were deposited during the event in Sydney, Brisbane, Gladstone and Mackay, respectively. In the South East Queensland region, this deposition is equivalent to 40% of the total annual TSP emissions for the region. The event increased TSP, PM 10 and PM 2.5 concentrations and reduced the visibility beyond the health and amenity guidelines in the four cities. For example, the 24-h average PM 10 concentrations in Brisbane and Mackay, were 161 and 475 µg m −3 respectively, compared with the Australian national ambient air quality standard of 50 µg m −3. The 24-h average PM 2.5 concentration in Brisbane was 42 µg m −3 , compared with the national advisory standard of 25 µg m −3. These rural dusts significantly increased PM 10 /TSP ratios and decreased PM 2.5 /PM 10 ratios, indicating that most of the particles were between PM 2.5 and PM 10 .

Two related problems of sediment hydraulics are addressed: ͑1͒ Inception of sediment transport for nearly uniform flow of both uniform and nonuniform sediment beds for two different sediment densities and grain sizes ranging from sand to gravel, and ͑2͒ generalized inception conditions if elements are inserted in a plane sediment bed. The Shields' criterion is formulated with basic quantities involving gravity, viscosity, and densities of the two-phase flow. The results of the analysis relate to the viscous, the transition, and the fully turbulent regimes. The transition regime is verified with extended laboratory experiments. Then, these conditions are used as a basis for formulating a general stability criterion for loose bed hydraulics, and compared to detailed experiments involving pier and square elements located either at the channel side or at its axis. In addition, a generalized densimetric particle Froude number is introduced that accounts for both uniform sediments and mixtures. The engineering application of the present results is straightforward, given that basic parameters of hydraulics, sediment, and fluid are involved.

Résumé Le fjord du Saguenay est un laboratoire géoscientifique naturel exceptionnel. Sa physiographie et ses caractéristiques géomorphologiques, révélées par les levés multifaisceaux et de sismique-réflexion ainsi qu’une série de carottages, nous fournissent un éclairage nouveau sur l’évolution du fjord du Saguenay à partir du début de la déglaciation du fjord, il y a environ 11 000 ans, ainsi que sur l’enregistrement des différentes catastrophes naturelles majeures qui se sont produites dans la région. De plus, à cause de sa morphologie, le fjord du Saguenay est aussi un endroit de prédilection pour l’analyse des changements climatiques dans cette région du continent nord-américain. À partir de l’analyse morpho-sédimentologique du fjord du Saguenay, nous proposons de le subdiviser en trois parties : le supérieur, le moyen et l’inférieur. Le Saguenay inférieur correspond à la zone comprise entre Tadoussac (kilomètre zéro), à une profondeur d’environ 20 m, et jusqu’à environ 42 km en...

Determination of sediment erosion and deposition fluxes from direct measurements associated with a drifting buoy in a tidal estuary, an application to the Seine (France). A direct evaluation of erosion and settling sediment fluxes, at the bottom boundary, is determined by measurements in a water column associated with a drifting buoy. The data were acquired during a high tide coefficient in the Seine estuary. The bed shear stress and the vertical sediment fluxes are regarded as independent variables. A new relation is proposed for calculating the total mass load of a given water column in a tidal estuary by knowing the friction velocity. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS sediment erosion / sediment deposition / sediment transportation / lagrangian coordinates Résumé -Une nouvelle méthode permettant l'évaluation directe des flux d'érosion et de dépôt de sédiments dans un estuaire macrotidal est proposée. Elle consiste à suivre les caractéristiques physiques, dont la charge solide, d'une colonne d'eau associée au déplacement d'une bouée dérivant dans l'estuaire de la Seine durant un cycle de marée de vive-eau. Cette démarche permet de considérer la contrainte de cisaillement sur le fond et le flux vertical des sédiments comme des variables indépendantes. Une relation entre la variation de la charge d'une colonne d'eau en matières en suspension et la vitesse de frottement sur le fond est suggérée. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS érosion de sédiment / dépôt de sédiment / transport sédimentaire / coordonnées lagrangiennes Abridged version * Correspondance et tirés à part : brun-cottan@geos.unicaen.fr 265 C. R. Acad. Sci. Paris, Sciences de la Terre et des planètes / Earth and Planetary Sciences 331 (2000) 265-270

Although weakly hydrophobic chemicals such as volatile organic compounds (VOCs) tend not to persist in sediments, they may nevertheless be present in some sediments because of recent or ongoing releases. Standard methods are not available for assessing risks to benthic invertebrates due to VOCs in sediment. More strongly hydrophobic organic chemicals are frequently assessed by using the equilibrium partitioning (EqP) approach, which predicts the bioavailable fraction of chemical (the concentration dissolved in pore water) from the sediment-sorbed fraction, assuming that partitioning is at equilibrium. As typically applied, the EqP approach is ineffective for assessing VOCs in sediment, because the standard EqP equation fails to account for the contribution of dissolved chemical to the total chemical concentration in sediment. For chemicals with low organic carbon-water partition coefficients (KOCs), this results in nonsensical sediment-quality benchmarks that are more conservative (i.e., lower) than benchmarks calculated by assuming 100% bioavailability. A modified EqP equation is presented that accounts for the dissolved fraction of total chemical concentrations in sediment. Results of the standard and modified EqP equations converge with increasing KOC and are essentially identical at log KOC values exceeding approximately 3.5.

A large number of hazardous compounds can be expected to be present in landfill leachates, many of which have not yet been identified. Thus this study screened samples from 12 Swedish municipal landfill sites for 400 parameters and compounds. More than 90 organic and metal organic compounds and 50 inorganic elements were detected, some of which seem to have not been detected before. Compounds detected include halogenated aliphatic compounds, benzene and alkylated benzenes, phenol and alkylated phenols, ethoxylates, polycyclic aromatic compounds, phthalic esters, chlorinated benzenes, chlorinated phenols, PCB, chlorinated dioxins and chlorinated furans, bromated flame-retardants, pesticides, organic tin, methyl mercury and heavy metals. The presence of this large number of hazardous compounds in landfill leachates should have a significant impact on future landfill risk assessments and the development of leachate treatment methods. We propose that future research should pay more atte...

Copyright © 2015 Khoshravan and Jabbari, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article:

The quantification and monitoring of sediment dynamics in estuaries has received plenty of attention in recent years due to both economic and environmental interests. Numerical models have been widely applied for predicting the morphodynamic evolution of these areas. However, the degree of uncertainty of these models is often very high due to the lack of measurements necessary for a complete model calibration and validation. In this paper, different methods have been integrated to overcome these limitations. The hydrodynamics and suspended sediment transport in the IJzer estuary were estimated by means of field data and with the use of a two-dimensional hydrodynamic model coupled to a morphodynamic model. Tidal pumping was recognized as the main driving mechanism of sediments inside the estuary. Erosion-deposition areas calculated with the numerical model were compared to the locations and volumes of dredged material. Model results and measurements were generally in good agreement. Additional support for the morphodynamic model results came from airborne hyperspectral images acquired in 2001 and 2005.

Little information is currently available about water column microbial processes or mortality during Arctic winter. To address this paucity, we used epifluorescence microscopy and dilution experiments to determine the abundance of flagellates, bacteria and virus-like particles (VLP) and the rates of bacterial growth, bacterivory and virus-induced mortality in subzero-temperature bottom waters (≤ 230 m) of Franklin Bay during February and March 2004, when ice-covered surface waters were highly oligotrophic (maximum chlorophyll a value of 0.09 µg l -1 ). We focused on bottom waters due to the possible importance of sediment resuspension as a source of organic matter. While flagellates were present at low densities (1.5 to 3.1 × 10 2 ml -1 ), bacterial concentrations resembled those from other seasons in the region and increased over the 5 wk sampling period, from 1.4 × 10 5 to 3.0 × 10 5 ml -1 . VLPs were typically an order of magnitude more abundant than bacteria (range of 1.4 to 4.5 × 10 6 VLP ml -1 ) and, like the fraction of particle-associated bacteria (but not total bacteria), correlated with particulate organic carbon concentration (r s = 0.82, p < 0.04, n = 7). Grazing rates, whether measured in dilution experiments or calculated from flagellate abundance, were low or undetectable (maximum of -0.004 h -1 ). Of 3 parallel experiments, 2 yielded substantial virus-induced mortality (-0.006 to -0.015 h -1 ), comparable to or exceeding the intrinsic bacterial growth rate (0.010 h -1 in both experiments) and suggesting viruses were the more important agents of bacterial mortality under these conditions. Using a viral reduction approach, VLP production measured in the water column or ice-moored sediment traps was commonly low (0.3 to 7.7 × 10 4 VLP ml -1 h -1 ) or undetectable, highly variable among replicates and, when measurable, implied viral turnover times between 0.9 and 12 d. In general, our results show that, despite the oligotrophy of Arctic winter, bottom water bacterial communities can remain active and subject to viral predation.

Samples of intertidal surface sediments (0-2 cm) were collected in 17 stations of the Santander Bay, Cantabric Sea, Northern Spain. The concentrations of polycyclic aromatic hydrocarbons (PAHs), 16, were analysed by HPLC and MS detection. Surface sediments show a good linear correlation among the parameters of the experimental organic matter evaluation, where total carbon (TC) and loss on ignition (LOI) are approximately 2.5 and 5 times total organic carbon (TOC). A wide range of TOC from 0.08% to 4.1%, and a broad distribution of the sum of P 16PAHs, from 0.02 to 344.6 lg/g d.w., which can be correlated by an exponential equation to the TOC, has been identified.

Previous studies have provided prima facie evidence that runoff from the MI motorway, UK, affects both the quality of the receiving water and the biota living there, in sites short distances from point sources-i.e., possible worst-case situations. Because discharges contain a wide variety of contaminants, both the identification of toxicants and the establishment of causal relationships between observed changes in waterhediment quality and biology are often difficult. In this particular case, the problem was addressed by conducting a series of toxicity tests using the benthic amphipod Gummnruspulex. The abundance of this species was greatly reduced downstream of the point where motorway runoff entered the stream. Stream water contaminated with motorway runoff was not toxic to G. pulex. However, exposure to contaminated sediments resulted in a slight reduction in survival over 14 d, and sediment manipulation experiments identified hydrocarbons, copper, and zinc as potential toxicants. Spiking experiments confirmed the importance of hydrocarbons, and fractionation studies indicated that most of the observed toxicity was due to the fraction containing polycyclic aromatic hydrocarbons. Animals exposed to contaminated sediments and water spiked with sediment extract accumulated aromatic hydrocarbons in direct proportion to exposure concentrations.

WHAM (Windermere Humic Aqueous Model) is designed to calculate equilibrium chemical speciation in surface and ground waters, sediments, and soils. The model is suitable especially for problems where the chemical speciation is dominated by organic matter (humic substances). WHAM combines Humic Ion-Binding Model V with a simple inorganic speciation code for aqueous solutions. Precipitation of aluminum and iron oxides, cation-exchange on an idealized clay mineral, and adsorption-desorption reactions of fulvic acid also are taken into account. The importance of ion accumulation in the diffuse layers surrounding the humic molecules is emphasized. Model calculations are performed with a BASIC computer code running on a Personal Computer.

Multi-proxy approach was used to reconstruct the environmental conditions of remote lakes in the High Tatra Mountains (Slovakia) over the past few centuries (approximately 500-1000 years). Short sediment cores (*30 cm) taken from three morphologically similar glacial lakes distributed along altitudinal gradient (subalpine to alpine conditions) were analysed for organic matter content (LOI), diatoms and chironomids. Both descriptive and correlative approaches were used for analysing stratigraphical data. Predictive canonical correspondence analysis and co-correspondence analysis were applied to directly relate physical and biological proxies to each other. The relationship between LOI and biotic proxies was inconsistent across groups and lakes. Concordant patterns in diatom and chironomid composition were found in two non-acidified lakes. Common trends in those assemblages indicated major past environmental events such as the Little Ice Age, air pollution and lake acidification. In contrast, no relationship between the composition of diatom and chironomid assemblages was found in the formerly acidified lake, suggesting different responses of assemblages to acidification. While chironomids showed shifts that are attributable to recovery, diatoms assemblage remained relatively stable throughout the uppermost layers of the sediment record. On the other hand, climatic-driven changes in assemblages detected in the deeper layers were more pronounced in diatoms than in chironomids.

A new adsorbent based on the imprinting technique with high retention capacity and pre-concentration factor has been synthesized and tested for retention of inorganic and organotin compounds wtributyltinchloride (TBT), dibutyltindichloride (DBT), monobutylytintrichloride (MBT) and triphenyltinchoride (TPhT)x. The polymerization has been carried out in the presence of TBT, the target organotin compound of this work. These compounds can be quantitatively retained on this adsorbent over a wide pH range and after elution these compounds are determined by graphite furnace atomic absorption spectrometry (GFAAS). Only organotin compounds are eluted from the adsorbent with 0.1 M hydrochloric acid (HCl) in methanol (MeOH) solution whereas inorganic tin is eluted later on with a suitable complexing agent such as citric acid. Linearity is obtained in the concentration range 0.1-4 ng (5-200 mg l ) for each organotin compound with a correlation coefficient not less than 0.994 and relative y1 standard deviation -5% even for complex samples such as sediments and seawater samples. The detection limit has been found to be 30 ng l . Various parameters related to determination, pre-concentration and GFAAS conditions have been optimized. The y1 screening method proposed has been applied to the determination of organotin in natural sediments and seawater samples. The recovery is between 82 and 90% for TBT, DBT and TPhT and 50-55% for MBT in the case of sediment samples, while it is 97-103% for all the organotin compounds in seawater samples. The method has been conveniently validated using a standard sediment reference material. ᮊ

Unsteady two-dimensional Navier-Stokes equations and Navier-Stokes type model equations for porous flow were solved numerically to simulate the propagation of water waves over a permeable rippled bed. A boundary-fitted coordinate system was adopted to make the computational meshes consistent with the rippled bed. The accuracy of the numerical scheme was confirmed by comparing the numerical results concerning the spatial distribution of wave amplitudes over impermeable and permeable rippled beds with the analytical solutions. For periodic incident waves, the flow field over the wavy wall is discussed in terms of the steady Eulerian streaming velocity. The trajectories of the fluid particles that are initially located close to the ripples were also determined. One of the main results herein is that under the action of periodic water waves, fluid particles on an impermeable rippled bed initially moved back and forth around the ripple crest, with increasing vertical distance from the rippled wall. After one or two wave periods, they are then lifted towards the next ripple crest. All of the marked particles on a permeable rippled bed were shifted onshore with a much larger displacement than those on an impermeable bed. Finally, the flow fields and the particle motions close to impermeable and permeable beds induced by a solitary wave are elucidated.

River restoration practices aiming to sustain wild salmonid populations have received considerable attention in the Unites States and abroad, as cumulative anthropogenic impacts have caused fish population declines. An accurate representation of local depth and velocity in designs of spatially complex riffle-pool units is paramount for evaluating such practices, because these two variables constitute key instream habitat requirements and they can be used to predict channel stability. In this study, three models for predicting channel hydraulics—1D analytical, 1D numerical and 2D numerical—were compared for two theoretical spawning habitat rehabilitation (SHR) designs at two discharges to constrain the utility of these models for use in river restoration design evaluation. Hydraulic predictions from each method were used in the same physical habitat quality and sediment transport regime equations to determine how deviations propagated through those highly nonlinear functions to influence site assessments. The results showed that riffle-pool hydraulics, sediment transport regime and physical habitat quality were very poorly estimated using the 1D analytical method. The 1D and 2D numerical models did capture characteristic longitudinal profiles in cross-sectionally averaged variables. The deviation of both 1D approaches from the spatially distributed 2D model was found to be greatest at the low discharge for an oblique riffle crest with converging cross-stream flow vectors. As decision making for river rehabilitation is dependent on methods used to evaluate designs, this analysis provides managers with an awareness of the limitations used in developing designs and recommendations using the tested methods. Copyright © 2008 John Wiley & Sons, Ltd.

The structure of nematode assemblages was investigated in the sediments of two different tourist marinas in the Mediterranean Sea and related to pollution variables. Nematode densities and generic compositions were determined, as were concentrations of heavy metals, PAHs and organic matter. Results showed different assemblages at the two marinas, with a dominance of the genera Paralongicyatholaimus and Daptonema. Significant correlations between nematodes and concentrations of environmental contaminants were found. In particular, Paralongicyatholaimus showed a significant negative correlation with Cu concentrations and was almost absent at the stations where higher Cu concentrations were found. The presence of sensitive/tolerant nematode genera represents a promising tool to identify areas subjected to a higher level of disturbance and to define the correct environmental management strategy for harbors.

A review of the levels of polycyclic aromatic hydrocarbons (PAH) and tributyltin (TBT) in sediments from Mobile Bay, Alabama, shows that overall levels of PAH decrease from the upper bay (RI) to the lower bay (RIV). Analysis of PAH ratios indicate that pyrogenic sources such as fossil fuel combustion are dominant. There are so few data on TBT in sediments that spatial trends cannot be identified.Levels of PAHs in oyster tissues decrease from the upper bay (RI) to the lower bay (RIII). Although there is no significant temporal trend for PAH levels in bivalves for the US; in the bay, levels in Region II (RII) have decreased significantly and are currently below the national median. There is no trend in Region III (RIII), where levels remain below RII and the national median. RI and RIV had too few data for trend analysis.Mean levels of TBT in oyster tissues decrease from the upper bay (RI) to the lower bay (RIII). Temporal trend analysis indicates a significant decreasing trend for TBT in the US but no significant trend was detected for RII and RIII in Mobile Bay. TBT levels in RII are consistently higher than levels in the US and RIII, which are similar. Data from RI are too limited for analysis and there are no data for RIV.

The physical processes that control mineral sediment deposition on a mesotidal salt marsh surface on the Atlantic Coast of Virginia were characterized through a series of measurements of sediment concentration, flow velocity, turbulence, water surface elevation, marsh topography and particle size distributions of sediment deposited on the marsh surface. The comprehensive nature of the data set allowed assessment of the temporal and spatial variability in marsh surface deposition, the variability in depositional processes among tides of different amplitudes, as well as the specific processes that control deposition on this tidal marsh. Through three different types of measurements, it was found that sediment deposition occurred on the marsh surface during rising tides at tidal elevations ranging from those barely flooding the creek bank to high spring tides, and that sediment was not remobilized by tidal flows after initial deposition. Sediment deposition occurred on this marsh surface largely because fine sediment in suspension formed flocs. Analysis of inorganic grain size distributions of sediment deposited within 8 m of the tidal creek indicated that 70-80% of this sediment was deposited in a flocculated form. The rest (particles larger than 20 m) were deposited as individual particles. In the marsh interior, 25 m from the tidal creek, single grain settling predominated. Reduction of turbulence levels within the vegetation canopy on the marsh also promoted particle settling. The processes controlling sediment deposition did not vary among tides. However, suspended sediment concentrations near the creek bank increased with increasing tidal amplitude, consequently promoting higher rates of deposition on higher tides.

Previous studies have provided prima facie evidence that runoff from the MI motorway, UK, affects both the quality of the receiving water and the biota living there, in sites short distances from point sources-i.e., possible worst-case situations. Because discharges contain a wide variety of contaminants, both the identification of toxicants and the establishment of causal relationships between observed changes in waterhediment quality and biology are often difficult. In this particular case, the problem was addressed by conducting a series of toxicity tests using the benthic amphipod Gummnruspulex. The abundance of this species was greatly reduced downstream of the point where motorway runoff entered the stream. Stream water contaminated with motorway runoff was not toxic to G. pulex. However, exposure to contaminated sediments resulted in a slight reduction in survival over 14 d, and sediment manipulation experiments identified hydrocarbons, copper, and zinc as potential toxicants. Spiking experiments confirmed the importance of hydrocarbons, and fractionation studies indicated that most of the observed toxicity was due to the fraction containing polycyclic aromatic hydrocarbons. Animals exposed to contaminated sediments and water spiked with sediment extract accumulated aromatic hydrocarbons in direct proportion to exposure concentrations.

The present study deals with quantification of accumulated toxic heavy metals in sediments of Mithi River of Mumbai. The study was performed at three different sampling locations along the flow of Mithi River for two years from 2009-12. The different heavy metals studied were Al, As, Cd, Cr, Hg, Ni, Pb, Sr and Mn. The results of our study indicate that the concentration level of these toxic heavy metals for the two assessment years increases by the factor of 1.2-5.8 µg/g. The result is a clear indication of day by day increasing pollution level of the Mithi River, which is creating negative environmental impact on biological life of the river. The results emphasises the need of regular scientific monitoring of different pollutants adversely affecting the environment and to reframe the pollution control strategies already in existence.

Microplastics have been reported in marine environmen ts worldwide. Accurate assessment of quantity and type is therefore needed. Here, we propose new techniques for extracting microplastics from sediment and invertebrate tissue. The method developed for sediments involves a volume reduction of the sample by elutriation, followed by density separation using a high density NaI solution. Comparison of this methods' efficiency to that of a widely used technique indicated that the new method has a considerably higher extractio n efficiency. For fibres and granules an increase of 23% and 39% was noted, extraction efficiency of PVC increased by 100%. The second method aimed at extracting microplastics from animal tissues based on chemical digestion. Extraction of microspheres yielded high efficiencies (94-98%). For fibres, efficiencies were highly variable (0-98%), depending on polymer type. The use of these two techniques will result in a more complete assessment of marine microplastic concentrations.

Urine analysis is one of the most common tests for assessing urinary-tract and kidney diseases. In recent years there have been new developments in the automation of this test. The objective of the present study was to compare the performances of two urine sediment analysers, namely LabUMat with UriSed (77 Elektronika Kft, Budapest, Hungary) and iQ ® 200 (Iris Diagnostics, Chatsworth, CA, U.S.A.), with the KOVA ® method for manual urine measurement by evaluating the results in terms of similar parameters (cells or particles per lower-power field or highpower field). The results obtained using the UriSed and iQ ® 200 analysers were more reproducible (7.1-30.2 and 14.9-35.4 % respectively) than those obtained using the manual technique (17.9-44.4 %). Significant correlations were established among the three techniques in the evaluation of leucocytes, erythrocytes and epithelial cells. Although the UriSed, iQ ® 200 and visual-microscopic measurements were in agreement, confirmation of the results from automated methods by manual urine analyses is significantly useful, especially for pathological cases that were close to the limits of the techniques.

La construction de barrage hydro-agricole demeure une nécessité absolue dans un contexte de sécheresse persistante au Burkina Faso. Le futur barrage de Samendéni devant contenir 1 milliard de mètres cube d'eau se situe dans des formations constituées de grès très fins reposant en concordance sur des sédiments fins très altérés. Le site se situe à quelques centaines de mètres d'un accident majeur, faille décrochante dextre de près de 60 km. Les mesures électriques et électromagnétiques Max-Min ont mis en évidence deux intrusions de dolérites, de nombreuses failles qui recoupent la digue. Les failles les plus incisives sont celles qui mettent en contact les intrusions de dolérites et leur encaissant. L'existence des failles pose un problème d'étanchéité et de stabilité de la digue. De plus, la mise en eau de l'ouvrage pourrait faire rejouer la faille décrochante située en amont (séisme induit).

Oxygen and total dissolved inorganic carbon (DIC) fluxes at the water–sediment interface were measured using benthic chambers to assess the short-term variations of community respiration (CR) in the back reef sediments of Reunion Island (Indian Ocean). Benthic CR had a daily cycle of minimal (6:00 AM) and maximal values (6:00 PM), showing increases of oxygen and DIC fluxes of 2.8- and 3.8-fold, respectively. Average CR values were observed at midday and midnight. The evolution of fluxes was positively related to oxygen concentration in ambient water, but not to temperature changes. In the study area, high daytime primary production augments the amount of energy available for community metabolism and increases benthic respiration. The benthic communities are therefore subjected to short-term variable environmental conditions with oxygen supersaturation during the day, and moderately hypoxic conditions at the end of the night.

Emissions from combined sewer overflows have detrimental impact on water quality (Verbanck, 1990). Sewer sediments forming regularly increase emitting loads. One alternative to high pressure jetting, the mostly used method for sewer cleansing, is flushing. Many case studies and numerical investigations have already shown that flushing is able to erase sewer sediments if certain boundary conditions are respected. However, critics keep reminding that during the storage phase suspended solids will settle and form additive layers of sediments. In order to verify observations that such sediments will not last, measurements of velocity profiles were conducted. These profiles were transformed with the log-wall law into a times series of shear stress. This procedure was conducted with six different storage heights. Subsequently, these time series of bottom shear stress were applied to two different transport models. One transport model by Zanke (1999) bases on a probabilistic approach while the other by Torfs (1995) uses deterministic methods. The calculated transport rates and the probably distribution clearly show that the solids built up during the storage phase will not last. Also, it was demonstrated that the sunk wave generates sufficient shear stresses to remobilize these solids.