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A part of the Raša Bay (western Croatia) is an estuary that is fed by the sediment load from the Raša River. The local area had been affected by the former Raša coal industry. The aim of this study was to determine levels of hazardous trace elements (HTEs) in bottom estuarine sediments, fish and mussels collected from two sites downstream of the Raša River mouth, and a wild boar’s kidney donated by hunters. The pseudo-total concentrations of 21 HTEs in sediments were obtained by the X-ray fluorescence (XRF) technique. The results showed that sediment collected closest to the former Raša coal separation unit Štalije was enriched in V, Sr, Ni, Cu, and Pb. Concentrations of HTEs in flathead grey mullet, wild blue mussels, and wild boar were obtained by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that Pb, Cd and Hg in fish and wild mussels were not elevated compared to the Regulation levels of contaminants in food. Lead and Cd in the kidney of a wild boar exceeded the prescribed maximum values for food. This study warrants further geochemical investigations of the Raša Bay environment.

Estuarine sediments are increasingly contaminated by heavy metals as a result of urbanization and human activities. Continuous multi-heavy metal accumulation in the ecosystem can provoke new effects on top of the complex environmental interactions already present in estuarine ecosystems. It is important to study their integrated influence on imperative microbial communities to reflect on the environmental and ecological risks they may impose. Inductively coupled plasma optical emission spectroscopy analysis for five metals Cd, Cr, Cu, Pb, and Zn showed that Cr and Cu concentrations in intertidal sediments of the urbanized Yangtze River estuary in China have consistently exceeded respective threshold effect concentration (TEC) levels. The geo-accumulation and potential ecological risk index results of the five metals showed that all sampling sites were weakly to moderately polluted, and at considerable to high ecological risk, respectively. Redundancy and correlation analyses showed that Zn followed by Cr in the ecosystem were explanatory of the shifts in recorded microbial community structures. However, the spatial variation in metal concentrations did not correspond to the selection of metal resistance genes (MRGs). Unlike many other dominant bacterial taxa, most of the sulfate-reducing bacteria (SRB) and associated sulfate respiration as the dominant microbially contributed ecological function were found to negatively correlate with Zn and total heavy metal pollution. Zn concentration was proposed to be a potent indicator for heavy metal pollution-associated microbial community compositional shifts under urbanized estuarine conditions. The associations between heavy metals and estuarine microbial communities in this study demonstrate the influence of heavy metals on microbial community structure and adaptations that is often overshadowed by environmental factors (i.e., salinity and nutrients). Copyright © 2021 Yi, Lo, Liu, Qian and Cheng.

Frequent and unexplained iron enrichments have been localized in buried, Holocene, marine sediments in coastal areas. These buried sediments are nowadays often part of groundwater systems in densely populated deltas. Here, the Krabbenkreek intertidal/supratidal area in the Netherlands is considered as a present analogue for diagenetic processes in these near-shore sediments. We evaluate the role of tidally driven groundwater flow alternations on the transport and speciation of Fe in deep tidal sediments. This was achieved by examining geochemical sediment and porewater data in the context of 3-D geohydrological modelling results of the groundwater system. The Krabbenkreek area presents clear hydrologic and geochemical zonations across the supratidal/intertidal area. Due to the low hydraulic conductivity, groundwater flow and infiltration of rain water is limited in the mud-rich upper sediments of the supratidal flat. Despite tidal fluctuations of the hydraulic heads up to 1.5 m, the corresponding alternating groundwater flow is relatively minor in comparison to the net groundwater flow. Tidal variations in the groundwater force field alone did not lead to pronounced local enrichments in reactive Fe. Differences in reactive Fe contents in deep sediments can be related to textural differences, implying that no indications for local, diagenetic Fe enrichments were found in the sediments down to 5 m depth. Contents of FeS and amorphous Fe(III) are remarkably low indicating little current dynamics in Fe redox cycling in these deep sediments, while the porewater chemistry indicates that pyrite oxidation prevails. Long-term oxidation of pyrite is reflected by the presence of Fe(III) oxides in the high marsh sediments while pyrite still dominates in the middle marsh and the intertidal sediments. Absence of active Fe redox cycling can be attributed to low respiratory activity in the sediments. Previous studies reported that sedimentary organic matter in the vicinity of th

The globalization of the industrialization is being pointed out as the synchronous and global event that potentially marks the starting point of a current-proposed stratigraphic epoch: the ‘Anthropocene’. Its study makes necessary high-resolution (yearly) works on recent stratigraphic records such as estuarine sediments. Concerning industrialization, the Ria of Ferrol represents a paradigmatic example in the NW of the Iberian Peninsula. This area is under the impact of military shipyards since 1730. Their maximum activity happened after 1947, consequence of the industry restructuring and the implementation of civil shipbuilding (including oil super-tankers). The present study focused on a sediment core of 50 cm long that holds record since the beginning of the 20th century, according to Pb-210 dating. Trace metal contents were evaluated to identify the human imprint. Background levels established in nearby areas with similar mineralogical characteristics were considered. Three main periods can be distinguished based on the trace-element to Al ratios: (i) from the beginning of the 20th century until about 1970, when ratios increase usually about 1.5 to 2.4 times, (ii) between around 1970 to 1990, when these ratios decrease usually about 1.4 to 2.3 times, and (iii) from 1990 to 2010, when ratios maintained. The studied sediments reflect the human-environment relationship in the area during the 20th century: the metal to Al ratios, sediment accumulation rates, total metal fluxes and enrichment factors show a first period of increasing industrialization without environmental concern, followed by an industrial collapse and a subsequent reactivation while implementing environmental friendly processes and policies

Severe metal pollution due to industrial effluents releases has been documented in Jiulong River estuary, Southern China. However, integrated understanding of trace metal behavior in the sediment is lacking. In the present study, DGT (diffusive gradients in thin films) technique was employed together with sediment cores to study the porewater dynamics of trace metals as well as the benthic exchange fluxes from four sampling sites over three different months. The sedimentary environment showed distinct spatial and temporal variations due to effluent discharge and biological activities. Metal behavior was controlled by early diagenetic reactions below the interface, in suboxic layer and in deeper sediment. Precipitation as sulfides and adsorption onto Mn/Fe (hydr)oxides were important in scavenging trace metals. Estimated exchange fluxes at sediment-water interface in this estuary indicated that the overlying water was a major source for trace metals, whereas sediments could also be the source if surface remobilization (Mn/Fe reduction) dominated. Our results highlighted the impacts of both natural and anthropogenic processes on the source, fate and transformation of trace metals in this dynamic system. © 2017 Elsevier Ltd

The Baie de Somme is an infilling estuarine environment, controlled by intensive marine hydrodynamics forcing (megatidal tide and waves) and a small river flow. Morpho-sedimentary dynamics of this bay and sedimentary fluxes were studied at two spatial and temporal scales. I) At the scale of intertidal hydraulic dunes, studied during semi-diurnal and semi-lunar tidal cycles with neap tides (NT) and spring tides (ST). In this context, a strong forcing variability (winds, tide, waves) control sedimentary fluxes and morphodynamics evolutions of dunes (λ : 5-23 m ; H : 20-60 cm). These fluxes generally increase with tide and waves, inducing a net sediment transport to the east or west, according to the predominance of current (flood/ebb), which depends on the characteristics of wind and waves. Low tide morphology of dunes depends on hydrodynamic conditions and sediment transport : asymmetry eastwards under a threshold water depth of 2,64 to 2,73 m. ; asymmetry westwards above this threshold, during quiet or agitated tide (Hs max < 1,5 m) ; sub-symmetry and flattening dunes during very agitated ST ( Hs max ≥ 1,83 m) ; asymmetry eastwards during a storming ST. Migration of dunes crests is more intense during ST than during NT and is not always in accordance with net sediment transport directions. It is due to significant variations in dunes morphology and polarity. During a semi-lunar tide cycle with waves, net sediment transport and dunes migrations are in direction of internal area of the bay (eastward). II) At the scale of the bay, studied to seasonal, annual and multiannual time steps, infilling dynamics is significant. Superficial sedimentary cover of the bay, observed in 2013, show a filtering gradient of sediment « offshore-coast » and « central axis-shoreline », with internal borders characterized by an increase in muds and carbonates rates between 1980 and 2013. At recent historical scale (1947-2011), orthophotos show a strong progress of coastal barriers (sand du, La Baie de Somme est un environnement estuarien en comblement, contrôlé par des forçages hydrodynamiques marins intenses (marée de type mégatidal et houle) et un faible régime fluviatile. La dynamique morpho-sédimentaire de cette baie, ainsi que les flux sédimentaires responsables, ont été étudiés à deux échelles spatiales et temporelles. I) A l'échelle de champs de dunes hydrauliques intertidales, étudiés durant des cycles de marées semi-diurnes et semi-lunaires de mortes-eaux (ME) et de vives-eaux (VE). Dans ce contexte, il s'avère que la forte variabilité des forçages (vents, marée, houle) contrôle les flux sédimentaires et les évolutions morphodynamiques des dunes (λ : 5-23 m ; H : 20-60 cm). Ces flux augmentent globalement avec le coefficient de marée et les conditions d'agitation, induisant un transport sédimentaire net vers l'est ou vers l'ouest, selon la prédominance des courants (flot/jusant), qui dépend des caractéristiques de vent et de houle. Les dunes adoptent une morphologie à basse-mer qui est dépendante des conditions hydrodynamiques du milieu et du transport sédimentaire : asymétrie vers l'est sous un seuil de profondeur d'eau de 2,64-2,73 m ; asymétrie vers l'ouest au-dessus de ce seuil, lors des marées calmes à agitées (Hs max < 1,5 m) ; sub-symétrie et aplatissement des dunes lors de VE très agitées (Hs max ≥ 1,83 m) ; asymétrie vers l'est lors d'une VE de tempête. La migration des crêtes de dunes est plus intense en VE qu'en ME et ne présente pas toujours de similitude avec les directions de transport sédimentaire net, ceci étant dû aux variations importantes de morphologie et de polarité. Durant un cycle de marée semi-lunaire assez agité, le transport sédimentaire net ainsi que la migration nette des dunes s'effectuent vers les zones internes de la baie (vers l'est). II) A l'échelle de la baie, étudiée aux pas de temps saisonniers, annuels et pluriannuels, la dynamique de comblement est importante. La couverture sédimentaire superficielle de la

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Griffith School of Environment, Science, Environment, Engineering and Technology, Meiofauna are ubiquitous but poorly-studied components of soft-bottom marine communities around the world, including mangroves. However, information on the ecological role of the meiofauna in subtropical intertidal habitats is scarce compared to knowledge of the benthic macrofauna. The dynamic environmental conditions and heterogeneous sediments of mangroves present challenges to understanding the structure of mangrove meiofaunal assemblages at various spatial and temporal scales. This study was designed to elucidate the ecological role of the meiofauna in mangroves by studying their three main ecological elements: 1) assemblages structure; 2) top-down interaction with macrofauna; and 3) bottom-up interaction in terms of nutrient utilisation. Firstly, how meiofaunal assemblage respond to estuarine sediment conditions was described by analysing the assemblages associated with different mangrove species (Avicennia marina, Rhizophora stylosa and Aegiceras corniculatum) at three locations in sub-tropical Southeast Queensland, Australia. Secondly, the significance and nature of top-down control on the density of meiofauna based on their interactions with deposit- feeding crabs was investigated in a mangrove and the adjoining sandflat.

The purpose of this data file, which has been modelled after Hathaway (1971), is to make available most of the basic data that was collected as part of Woods Hole Oceanographic Institution's study of New Bedford Harbor. The New Bedford Harbor project, which was jointly funded by the Office of Sea Grant and Woods Hole, was designed to examine the past and present patterns of dispersal and accumulation of fine-grained sediments and waste materials in New Bedford Harbor and its approaches., Prepared for the Department of Commerce, National Oceanic and Atmospheric Administration, Office of Sea Grant under Contract 04-6-158-44016 and 04-6-158-44106.

This study examines the spatial and temporal distribution patterns of arsenic (As) in solid and aqueous materials along the mixing zone of an estuary, located in the south-eastern part of the Bothnian Bay and fed by a creek running through an acid sulfate (AS) soil landscape. The concentrations of As in solution form (<1 kDa) increase steadily from the creek mouth to the outer estuary, suggesting that inflowing seawater, rather than AS soil, is the major As source in the estuary. In sediments at the outer estuary, As was accumulated and diagenetically cycled in the surficial layers, as throughout much of the Bothnian Bay. In contrast, in sediments in the inner estuary, As concentrations and accumulation rates showed systematical peaks at greater depths. These peaks were overall consistent with the temporal trend of past As discharges from the Ronnskar smelter and the accompanied As concentrations in past sea-water of the Bothnian Bay, pointing to a connection between the historical smelter activities and the sediment-bound As in the inner estuary. However, the concentrations and accumulation rates of As peaked at depths where the smelter activities had already declined, but a large increase in the deposition of Al hydroxides and Fe phases occurred in response to intensified land-use in the mid 1960's and early 1970's. This correspondence suggests that, apart from the inflowing As-contaminated seawater, capture by Al hydroxides, Fe hydroxides and Fe-organic complexes is another important factor for As deposition in the inner estuary. After accumulating in the sediment, the solid-phase As was partly remobilized, as reflected by increased pore-water As concentrations, a process favored by As(V) reduction and high concentrations of dissolved organic matter. (C) 2015 Elsevier B.V. All rights reserved.

In sediments, manganese (Mn) is typically enriched in the form of authigenic Mn hydroxides at the water-sediment interface where intensive redox cycling of Mn occurs. Here we show, based on existing hydrochemical and geochemical (sediment core) data and new detailed chemical and mineralogical characterization of a 3.5 m long sediment core from a Boreal estuary, that the behavior of Mn can be profoundly different and more complex in estuarine settings receiving an abundance of terrestrial Mn. The most notable feature in the 3.5 m long sediment core is two depth intervals (60-155 cm and 181-230 cm) where there are strong fine-scale variations in Mn concentrations with peaks episodically reaching up to 10-25 g kg(-1) and 6.7-12 g kg(-1), respectively. X-ray absorption spectroscopy and sequential chemical extraction show that Mn occurs mainly as authigenic rhodochrosite at these two depth intervals and is mainly surface-sorbed in other sections with relatively low and stable Mn concentrations. The data suggests that the strong fine-scale variations in Mn concentrations are a reflection of the extent of formation and settling of Mn hydroxides, the precursors of the authigenic rhodochrosite (and also of the surface-sorbed Mn), rather than Mn input to the estuary or redox-related Mn translocation within the sediment. There was agreement between the results of linear combination fitting of extended X-ray absorption fine structure data and a 7-step sequential chemical extraction (SCE) in terms of quantification of surface-sorbed Mn species, whereas the SCE experiment failed to fractionate a majority of rhodochrosite into SCE step-2 (1M NH4-acetate at pH 6), which is frequently employed to dissolve carbonate. We ascribe this discrepancy to only partial dissolution of rhodochrosite in the weakly acidic (pH = 6) NH4-acetate leach. (C) 2016 Elsevier B.V. All rights reserved.

A range of chemostratigraphic and lithostratigraphic markers of human impacts can be recorded in four estuaries located in the eastern Cantabrian coast (northern Spain). Metal-enriched levels and stable Pb isotopic ratios in dated sediment cores allowed the recognition of an ancient local episode of Pb contamination associated with mining activities during Roman times, as well as the widespread fingerprint of the Industrial Revolution and the "Great Acceleration" of human pressure after the Second World War. Micropalaeontological data (variations in foraminiferal assemblages) provided key information to identify agricultural soils in previously reclaimed and currently regenerated salt marshes, whereas anthropogenic beachrocks offered an example of the incorporation of technofossils to the coastal sedimentary record.

Summary: Peat soils are known to be a significant source of atmospheric greenhouse gasses. However, the releases of methane and carbon dioxide gasses from peat soils are currently not well understood, particularly since the timing of the releases are poorly constrained. Furthermore, most research work performed on peatlands has been focused on temperate to sub-arctic peatlands, while recent works have suggested that gas production rates from low-latitude peat soils are higher than those from colder climates. The purpose of the work proposed here is to introduce an autonomous Ground Penetrating Radar (GPR) method for investigating the timing of gas releases from peat soils at the lab scale utilizing samples originating from Maine and the Florida Everglades, and at the field scale in a Maine peatland. Geophysical data are supported by direct gas flux measurements using the flux chamber method enhanced by timelapse photography, and terrestrial LiDAR (TLS) monitoring surface deformation., by William J. Wright., Thesis (M.S.)--Florida Atlantic University, 2013., Includes bibliography., Mode of access: World Wide Web., System requirements: Adobe Reader.

ERDC/CHL CHETN-XIV-23 September 2012 Approved for public release; distribution is unlimited. Destroy when no longer needed; do not return to the originator. Estuarine Sediment Budgets for Chesapeake Bay Tributaries by Julie D. Herman PURPOSE. This Coastal and Hydraulics Engineering Technical Note (CHETN) summarizes estuarine suspended sediment budgets developed for several estuaries of the Chesapeake Bay in Maryland and Virginia (Herman and Friedrichs 2010). These sediment budgets provide better understanding of sediment transport patterns and pathways, and will aid in improving Regional Sediment Management (RSM) practices in the US Army Engineer Districts, Baltimore and Norfolk. Sediment budgets were calculated for the Patuxent River, Maryland; York River, Virginia; and a partial budget was developed for the Potomac River, Maryland. BACKGROUND. Sediment Budgets. Sediment budgets account for the sources (areas of erosion) and sinks (areas of deposition) of sediment in a specified area over a specified time frame. The components of a sediment budget may vary depending on spatial and temporal scales, local variables, and available data. Sediment budgets can identify types and locations of missing data that could help direct future research needs for additional data collection. Also, sediment budgets may assist significantly in improving management decisions. The sources and sinks in a sediment budget are calculated as sediment loads, and the loads are related in a mass balance equation. Load is mass per unit of time. This study used metric tons per year (Mt/yr), where a metric ton is 1,000 kg. Figure 1 displays the conceptual model of the sediment budget for Chesapeake Bay estuaries. Study Areas. The York and Patuxent Rivers were chosen to represent Virginia and Maryland, respectively, because these well-studied river systems have the necessary data to calculate sediment budgets. The study revealed problems unique to datasets for each state during the first phase of t

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology [and the Woods Hole Oceanographic Institution] August 1987, Tidally forced circulation can cause a net near-bed transport of sediment when the tidal velocity is asymmetric about a zero mean (flood or ebb dominant) and the transport rate is nonlinearly related to velocity. The relationship between elevation and velocity is elucidated here to enable one to determine from tide gauge data and sediment transport relations whether tidal asymmetry may cause net sediment transport. Tidal elevation and tidal velocity are related through the equations of motion of the fluid. If the estuary is shallow, the change in cross-sectional area of the channel with the tide is significant with respect to total area: the equations become nonlinear and an exact solution does not exist. A relationship between elevation and velocity in a nonlinear system is derived through the continuity equation and shown to be significantly different than the linear relation. Finite difference numerical solutions of the one dimensional, shallow water nonlinear equations are compared to the continuity relation and are in good agreement. The relationship between elevation asymmetry and ratio of flood-to-ebb bedload transport is calculated for both the linear relation between elevation and velocity and the nonlinear relation. Results show that the ratio of flood·to-ebb bedload transport as calculated from the nonlinear relation between elevation and velocity is similar to the flood-to-ebb ratio calculated from the linear relation., This work is the result of research sponsored by NOAA National Sea Grant College Program Office, Dept. of Commerce, under grant number NA86-AA-D-SG090, WHOI Sea Grant Project Number R/M-16-PD, by the U.S. Army Engineer Waterways Experiment Station's Coastal Engineering Research Center

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 1999, This study uses geophysical and sedimentological data collected from the Lower Hudson River estuary to identify the depositional response of the estuary to high river discharge events. Erosional and depositional environments in the estuary are identified through the use of side-scan sonar, bottom penetrating sonar and surficial sediment sampling. Sediment cores are used to document deposit thicknesses and to obtain the spatial distribution of estuarine deposits. Results show a high degree of spatial and temporal variability in sedimentation within the estuary. Two primary deposits are identified underneath the turbidity maximum for the estuary. Approximately 300,000 metric tons of sediment were deposited within these two deposits during May and June of 1998. This short-term accumulation underneath the turbidity maximum of the estuary can account for 30 to 98 percent of the estimated, river-borne sediment load supplied to the estuary during the 1997-1998 water year. Both the tidally produced stratigraphy observed in sediment cores and the spatial distribution of identified deposits, support the theory that sedimentation underneath the turbidity maximum of the estuary is primarily the results of a convergence in bottom water flow, caused by the formation of a salinity front during ebb tide., This research was funded by the Hudson River Foundation and a National Science Foundation Coastal Trainee Fellowship.

Background - Global warming and the alteration of the global nitrogen cycle are major anthropogenic threats to the environment. Denitrification, the biological conversion of nitrate to gaseous nitrogen, removes a substantial fraction of the nitrogen from aquatic ecosystems, and can therefore help to reduce eutrophication effects. However, potential responses of denitrification to warming are poorly understood. Although several studies have reported increased denitrification rates with rising temperature, the impact of temperature on denitrification seems to vary widely between systems. Methodology/Principal Findings - We explored the effects of warming on denitrification rates using microcosm experiments, field measurements and a simple model approach. Our results suggest that a three degree temperature rise will double denitrification rates. By performing experiments at fixed oxygen concentrations as well as with oxygen concentrations varying freely with temperature, we demonstrate that this strong temperature dependence of denitrification can be explained by a systematic decrease of oxygen concentrations with rising temperature. Warming decreases oxygen concentrations due to reduced solubility, and more importantly, because respiration rates rise more steeply with temperature than photosynthesis. Conclusions/Significance - Our results show that denitrification rates in aquatic ecosystems are strongly temperature dependent, and that this is amplified by the temperature dependencies of photosynthesis and respiration. Our results illustrate the broader phenomenon that coupling of temperature dependent reactions may in some situations strongly alter overall effects of temperature on ecological processes

Passive sampling is a powerful tool for determining the concentrations of truly dissolved contaminants in pore waters as well as for measuring the size of the exchangeable contaminant fraction in the sediment phase. Application of passive sampling of nonpolar contaminants in sediments is technically easy, but conceptually difficult, compared with traditional batch water sampling. The sorption capacity of the samplers and the (equivalent) water sampling rate are the two parameters that are needed to conceptualize the sampling process. These parameters also determine the value of the detection limits and the rate at which passive samplers equilibrate with their environment. After discussing contaminant uptake by passive samplers in an infinite water volume, their behavior in sediments will be dealt with using two practical examples. Exposure to stagnant sediments will be contrasted with exposure to sediment slurries. Passive sampler exposure to sediment slurries at low sampler/sediment phase ratios allows concentrations of dissolved contaminants in the pore water to be estimated. Exposure at high sampler/sediment phase ratios yields information on the size of the contaminant fraction in the sediment that is easily exchangeable with the pore water. Guidelines for designing passive sampler exposures to contaminated sediments will be discussed, and sources of uncertainties in the results will be highlighted., Presented at the Annual Partners in Environmental Technology Technical Symposium & Workshop (15th), held on 30 Nov-2 Dec 2010, in Washington, DC. Sponsored by SERDP and ESTCP. U.S. Government or Federal Rights License

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1978., Microfiche copy available in Archives and Science., Bibliography: leaves 104-111., by Nathan Hawley., Ph.D.

New Bedford Harbor and its approaches form the estuary of the Acushnet River in southeastern Massachusetts. The estuary is weakly stratified and only partially mixed because river discharge is very small. It appears to be typical of the inlets of the coast of New England, and is a branch of a larger estuary - Buzzards Bay. Silt and clay are being transported into the estuary in suspension by landward-moving bottom currents that are driven by wave and tidal energy. These fine sediments come from Buzzards Bay, but may originate out on the continental shelf. Before the entrance to the harbor was almost completely blocked by a hurricane barrier, these sediments were accumulating in the harbor at rates of about 1-2 cm/yr in the deeps, and less than 0.5 cm/yr in the shallows. Construction of the barrier reduced the efficiency of tidal flushing, causing the rate of siltation to increase by a factor of 4-5. Outside the harbor, silt and clay accumulate in the drowned valley of the Acushnet and in related depressions at rates of 2-3 mm/yr. In the water column, silt and clay sized minerals are suspended together in organically bonded agglomerates. During sediment transport, the silt and clay become partially fractionated, probably by differential settling of the agglomerates. Because fractionation is more effective where wave and tidal energy are strongest, there is a smaller proportion of clay relative to silt in the harbor than there is seaward. Nevertheless, the net transport of clay is still landward. Fractionation due to differential settling also appears to have formed a very thin, soupy layer of clay-rich material at the sediment-water interface, that appears to carpet the study area. This layer seems to form a transition zone between the much more silty and less mobile subsurface sediments and the highly mobile suspensates of turbid near-bottom waters. Further study is needed to ascertain precisely the nature and persistence of this layer., Prepared for the Department of Commerce, National Oceanic and Atmospheric Administration, Office of Sea Grant under Contract 04-6-1 58-44016 and 04-6-1 58-441 06.

The effect of acid drainage on light rare earth elements (LREE) has been studied in the estuarine sediment of the Tinto and Odiel system, where the fluvial and marine water mixing cause an important pH and chlorinity gradient inside. Due to the high influence of pH over the LREE partitioning from dissolved toparticulate phases, an anomalous behaviour has been found on La content in these sediments. Large removal of LREE takes place at low chlorinity zones in unaffected estuaries, but in the studied system this natural process is moved out the outer zones of the estuary. So, the relative La depletion in the estuarine mixing zone is due to the low pH values (< 6) that prevents LREE removal in low chlorinity zones. Once the acid neutralization (pH ~ 7) occurs, some La enrichment can be observed in sediments of the marine estuary.

We compared behavioural (burrowing speed), biochemical (acetylcholinesterase [AChE] inhibition, activities of digestive enzymes) and physiological (feeding and egestion rates, condition) responses in Nereis diversicolor originating from a multipolluted estuary (Loire estuary) and a relatively clean site (Bay of Bourgneuf) on 3 occasions during spring 2008. Significant inhibition of AChE and digestive enzymes (amylase and carboxymethylcellulase) activities were recorded in individuals from the Loire estuary compared to the reference site. At the individual level no significant intersite differences in burrowing speed were observed when ragworms were exposed to their sediment of origin. No link between AChE activity and burrowing behaviour was found in worms from either site. Cross-tests revealed that behavioural disturbances in locomotion were not due to neurological dysfunction but to avoidance of contaminated sediments. Feeding and egestion rates were depressed significantly in worms originating from the Loire estuary compared to the reference site. These behavioural impairments were accompanied by changes in digestive enzyme activities, which can explain the generally poorer condition of ragworms from the Loire estuary. Temporal changes in responses reported in the present study underline the importance of the fluctuation of environmental factors and thus the need for more than one sampling series to assess the health status of a given site. Disturbances at the different levels of biological organisation are likely explained by environmental contamination either chronic in the Loire estuary or the result of a small oil spill.

Oyster reef restoration is currently receiving increased attention as a means of enhancing water quality and fisheries. Oyster reefs not only directly provide habitat for fish and invertebrates, but also may indirectly affect adjacent sandflat areas with broader ecological consequences. Aspects of reef morphology, including vertical and edge complexity, influence the degree of impact oyster reefs have on adjacent communities. This study examines the extent to which created reefs of varying vertical and edge complexity influence sediment nutrient fluxes, microphytobenthos biomass, sediment grain size, and sediment organic content in a southeastern North Carolina intertidal sandflat. An overall significant effect of reef edge complexity on microphytobenthos biomass, pore water nutrients, and sediment grain size was discovered, though some patterns varied seasonally. Reef surface complexity was associated with changes in sediment characteristics, including greater proportions of fine sediments and percent organic matter immediately adjacent to the reef. Seasonal trends were highly significant with strong differences among seasons. This study is significant in demonstrating linkages between intertidal oyster reefs and adjacent sandflat communities including changes in microphytobenthos biomass and sediment characteristics in the sandflat area. Moreover, the nature of these linkages is influenced by both edge and surface attributes of the reef.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environmental Engineering, An improved understanding of the geochemical partitioning of trace metals and tributyltin (TBT) in sediments is of great importance in risk assessment and remedial investigation. The aim of this thesis was to examine the distribution and partitioning behaviour of trace metals and TBT in benthic, estuarine sediments. This was achieved by a series of field- and laboratory-based studies investigating factors controlling the geochemical behaviour of trace metals and TBT in sediments from south-east Queensland, Australia. The distribution and enrichment of selected trace metals in benthic sediments of the Southport Broadwater (a semi-enclosed coastal body of water adjacent to the Gold Coast city, south-eastern Queensland, Australia) was studied. Sediment contamination for Cd, Cr, Cu, Ni, Pb, Sn and Zn was assessed by (1) comparison with Australian sediment quality guidelines, (2) calculation of the index of geoaccumulation based on regional background values, and (3) geochemical noi-malisation against Al (i.e. the abundance of alumino-silicate clay minerals). Based on this approach, several sites were found to be strongly enriched with Cu, Pb, Sn and Zn, arising from sources related to either urban runoff or vessel maintenance activities. The geochemical partitioning of Cu, Pb and Zn was examined in sediments collected from three of these sites of sediment contamination. Total Cu, Pb and Zn concentrations in coarse-textured (65 to 90 % sand sized particles), sub-oxic sediments (Eh + 120 to +260 mV) ranged from 8.3 to 194 mg/kg for Cu, 16.3 to 74.8 mg/kg for Pb and 30.1 to 220 mg/kg for Zn, and were related to vertical trends in sediment texture. The association of Cu, Pb and Zn with amorphous oxides, crystalline oxides and organic matter was linearly dependent on the abundance of each phase. For retention by amorphous oxide minerals, the trace metal retention ranged from 5.2 to 23.7 mgcjgFe oxide as Fe for Cu, 1 2.8 to 21 .5 mgpb/gFe oxide as Fe for Pb, and 23. I to 85.7

Coniothyrium-like coelomycetes are drawing attention as biological control agents, potential bioremediators, and producers of antibiotics. Four genera are currently used to classify such anamorphs, namely, Coniothyrium, Microsphaeropsis, Cyclothyrium, and Cytoplea. The morphological plasticity of these fungi, however, makes it difficult to ascertain their best generic disposition in many cases. A new genus, Paraconiothyrium is here proposed to accommodate four new species, P. estuarinum, P. brasiliense, P. cyclothyrioides, and P. fungicola. Their formal descriptions are based on anamorphic characters as seen in vitro. The teleomorphs of these species are unknown, but maximum parsimony analysis of ITS and partial SSU nrDNA sequences showed that they belong in the Pleosporales and group in a clade including Paraphaeosphaeria s. str., the biocontrol agent Coniothyrium minitans, and the ubiquitous soil fungus Coniothyrium sporulosum. Coniothyrium minitans and C. sporulosum are therefore also combined into the genus Paraconiothyrium. The anamorphs of Paraphaeosphaeria michotii and Paraphaeosphaeria pilleata are regarded representative of Paraconiothyrium, but remain formally unnamed. Paraconiothyrium species are phylogenetically distant from typical members of the other coelomycete genera mentioned above

A width-averaged two-dimensional (2-D) model and a three-dimensional (3-D) model have been developed for the Jiaojiang estuary which is a highly turbid and macrotidal estuary. The sediment-induced buoyancy effects and the consequent turbulence damping effects have been taken into account in these models. It is possible to consider the upper suspensions and fluid mud as a whole, without empirical exchanges between these two compartments, as in the so-called continuous approach. The Princeton ocean model (POM) with a generalized sigma-coordinate system has been used as the hydrodynamics module of the 3-D model with improvements on advection schemes for scalar variables, introducing the drying and flooding algorithm and the additional capacity to deal with the non-Newtonian effects of high-concentration mud suspensions. Simultaneous currents and SSC (Suspended Sediment Concentration) time series data from several elevations at a mooring site and from ship-born observations over a tidal cycle in April 1991 enable the calibrations of these models. From the simulations and observations, some important findings have been obtained. The effective hydrodynamic drag is reduced in the very turbid environment. Under conditions of strong stratification due to sediment, the overall hydraulic roughness will be further decreased. The total mass of suspended sediment in the estuary is around 1.2x106 tons. The asymmetry in tidal currents drives the outer sediment to enter the estuary during the simulated period. The magnitude and location of turbidity maximum vary in the tidal cycle. The SSC, salinity and current have obvious longitudinal variations, while they also have cross-channel variations. The lutocline almost occurs over the entire cycle except during the period around high water slack. The fluid mud generally concentrates in the deep portions of estuary and in the shallow zone separating the estuary and Taizhou Bay.

Concentrations, distributions and mobility of chemical elements were investigated in reduced sulfur-rich estuarine sediments located in western Finland. The main objective was to determine the possible extent of metal leaching when dredged masses of these sulfur-rich sediments are dumped on the land and thus exposed to air. When dredged, the reduced sulfur in the sediments oxidises resulting in a lowering of pH, which in turn is expected to leach metals. The study area is an artificial lake claimed from the Botnian sea in 1962. In this lake, several mass-kills of fish have occurred, believed partly to be due to dredging. Two sediment samples (0–50 and 50–100 cm) were taken from 39 sampling points in the lake. These samples were leached in aqua regia (2:2:2 HNO3/HCl/H2O) and analysed for Fe, Al, Mg, Ca, K, P, Na, Mn, Zn, Ba, V, Sr, Cr, Ni, Cu, Co, As, Pb, B, Mo and Cd with ICP-AES. Sulfur and organic carbon were analysed with Leco. In a controlled laboratory experiment, the sediments were allowed to oxidise for 1 year while moisturised with deionised water every month. The pH and conductivity were determined in the beginning of the experiment (reduced state) and in the end (oxidised state). In the supernatants in the oxidised states the amount of leached metals (Na, Al, Mn, Zn, Sr, Co, Ni, Cu, Cd, Cr, Pb, U, Li, Rb and As) were determined with ICP-MS. The sediments were found to contain low levels of toxic metals but, as expected, high concentrations of sulfur. In the experiment, pH was lowered (down to 3.0) and the conductivity increased in all samples due to oxidation and release of metal ions. The extent of leaching varied between 0.03% for As and 12.3% for Na. Critical pH values, at which high amounts of metals begin to leach, were obtained graphically. These values varied between 4.8 (Ni) and 3.3 (Cr). Not all elements were controlled by pH, e.g. Mn correlated well with its aqua regia leachable concentration. In a planned dredging operation in the area some 23 3

The overall goal of this study is to examine the role that energy regime and associated seabed dynamics (e.g., frequency and depths of resuspension) play in controlling the distribution of polycyclic aromatic hydrocarbons (PAHs) in estuarine sediments. Our objectives are to examine sediment PAH distributions in environments representing contrasting depositional regimes within the York River, VA, a sub-estuary of the Chesapeake Bay. Our study utilizes a suite of geochemical tools to quantify sediment processes influencing the distribution of dissolved and solid-phase PAHs. These tools will enable us to quantify particle residence times in surface sediments, determine rates of sediment accumulation and disturbance, and investigate the effects of sediment organic matter composition and diagenesis.

[EN] Bacterial activities and biomass in sediments at two stations (Sta. 2 and Sta. 3) in Alfacs Bay, Ebro Delta. Spain were determined on a monthly basis, from April 1986 to March 1987. Maximal respiratory activity (aerobic and anaerobic) was highest in summer, which implied active transformation of accumulated organic matter in the sediment. This accumulation of organic material was always higher at Sta. 2 (average: 77 mg g-1).than at Sta. 3 (average: 16 mg g-1) due to the proximity of freshwater allochthonous inputs. In Sta. 2 we observed temporal changes in the activities of bacterial functional groups implying a succession in time of different electron acceptors. e.g., from the use of molecular O2 to NO3 and, eventually, to SO4, as the redox potential decreased. Maximum rates of oxygen consumption, heterotrophic activity, denitrification and the presence of anoxic sediments occurred at the end of summer. These sediment conditions should favour the development of sulphate reducing bacteria and their participation in the global flow of electrons. Sta. 3 always showed lower values of bacterial activities and biomass than Sta. 2, as well as positive redox potential. Averages of oxygen consumed along the year were 1.12 mmol O2 g-1 d-1 at Sta. 2 and 0.37 mmol O2 g-1 d-1 at Sta. 3. Denitrification rates averaged 147.87 nmol N2 g-1 d-1 at Sta. 2 and 50.73 nmol N2 g-1 d-1 at Sta. 3, and heterotrophic activity averages were: 0.037 nmol 3H thymidine g-1 h-1 at Sta. 2, and 0.012 nmol g-1 h-1 at Sta. 3. Bacterial biomass (heterotrophs, denitrifiers, and sulphate reducing bacteria) presented values one or two orders of magnitude higher at Sta. 2 than at Sta. 3. Our results showed that the development of bacterial communities changed with time at these two stations, depending on the proximity of external inputs of organic material, [ES] Desde abril de 1986 a marzo de 1987, en la Bahía de "Els Alfaes" (Delta del Ebro, España), se determino, mensualmente, la actividad y biomasa bacteriana del sedimento, concretamente en dos estaciones (Sta. 2 y Sta. ·). La actividad respiratoria era máxima en verano, lo cual implica una transformación activa de la materia orgánica acumulada en el sedimento. Esta acumulación de materia orgánica era siempre mayor en la Sta. 2 (media anual: 77mg g1), que en la Sta. 2 (media anual: 16mg g1) debido a la proximidad de aportes alóctonos de las aguas continentales

Both biologically active and autoclaved sediments convert trimethyltin hydroxide to the volatile tetramethyltin. Larger amounts of tetramethyltin were formed in the bioactive sediments than in the sterile sediments. No volatile tin compounds were detected in the absence of trimethyltin hydroxide or from trimethyltin hydroxide in seawater or in seawater containing bentonite. The formation of tetramethyltin is slow, taking over 80 days at 16 deg C to reach a maximum. The extent of conversion, although significant, is not extensive. The formation of tetramethyltin occurs in estuarine sediments by both abiotic and biologically enhanced pathways. A redistribution mechanism accounts for at least the abiotic pathway and possibly both formation pathways., Published in Science, v213 p770-771, 14 Aug 1981.

The purpose of this data file, which has been modelled after Hathaway (1971), is to make available most of the basic data that was collected as part of Woods Hole Oceanographic Institution's study of New Bedford Harbor. The New Bedford Harbor project, which was jointly funded by the Office of Sea Grant and Woods Hole, was designed to examine the past and present patterns of dispersal and accumulation of fine-grained sediments and waste materials in New Bedford Harbor and its approaches.

New Bedford Harbor and its approaches form the estuary of the Acushnet River in southeastern Massachusetts. The estuary is weakly stratified and only partially mixed because river discharge is very small. It appears to be typical of the inlets of the coast of New England, and is a branch of a larger estuary - Buzzards Bay. Silt and clay are being transported into the estuary in suspension by landward-moving bottom currents that are driven by wave and tidal energy. These fine sediments come from Buzzards Bay, but may originate out on the continental shelf. Before the entrance to the harbor was almost completely blocked by a hurricane barrier, these sediments were accumulating in the harbor at rates of about 1-2 cm/yr in the deeps, and less than 0.5 cm/yr in the shallows. Construction of the barrier reduced the efficiency of tidal flushing, causing the rate of siltation to increase by a factor of 4-5. Outside the harbor, silt and clay accumulate in the drowned valley of the Acushnet and in related depressions at rates of 2-3 mm/yr. In the water column, silt and clay sized minerals are suspended together in organically bonded agglomerates. During sediment transport, the silt and clay become partially fractionated, probably by differential settling of the agglomerates. Because fractionation is more effective where wave and tidal energy are strongest, there is a smaller proportion of clay relative to silt in the harbor than there is seaward. Nevertheless, the net transport of clay is still landward. Fractionation due to differential settling also appears to have formed a very thin, soupy layer of clay-rich material at the sediment-water interface, that appears to carpet the study area. This layer seems to form a transition zone between the much more silty and less mobile subsurface sediments and the highly mobile suspensates of turbid near-bottom waters. Further study is needed to ascertain precisely the nature and persistence of this layer.

Tidally forced circulation can cause a net near-bed transport of sediment when the tidal velocity is asymmetric about a zero mean (flood or ebb dominant) and the transport rate is nonlinearly related to velocity. The relationship between elevation and velocity is elucidated here to enable one to determine from tide gauge data and sediment transport relations whether tidal asymmetry may cause net sediment transport. Tidal elevation and tidal velocity are related through the equations of motion of the fluid. If the estuary is shallow, the change in cross-sectional area of the channel with the tide is significant with respect to total area: the equations become nonlinear and an exact solution does not exist. A relationship between elevation and velocity in a nonlinear system is derived through the continuity equation and shown to be significantly different than the linear relation. Finite difference numerical solutions of the one dimensional, shallow water nonlinear equations are compared to the continuity relation and are in good agreement. The relationship between elevation asymmetry and ratio of flood-to-ebb bedload transport is calculated for both the linear relation between elevation and velocity and the nonlinear relation. Results show that the ratio of flood·to-ebb bedload transport as calculated from the nonlinear relation between elevation and velocity is similar to the flood-to-ebb ratio calculated from the linear relation.