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Tidal marshes provide numerous ecosystem services, but are threatened by recent increases in global sea level rise (SLR). Marsh restoration and creation are important strategies for mitigating marsh loss, restoring ecosystem services, increasing coastal community resilience, and providing much needed habitat for threatened species. Dredged material resulting from navigation channel maintenance can provide a substrate for these restoration projects. Few studies, however, have addressed the sustainability of these marshes. The Paul S. Sarbanes Ecosystem Restoration Project at Poplar Island, where fine-grained, nutrient-rich dredged material from upper Chesapeake Bay is being used to create > 302 ha of tidal marshes, provides a case study. The low supply of inorganic sediment is counteracted by abundant nutrients, stimulating high rates of organic matter production and elevation change. Using > 10 years of data from 39 surface elevation tables, we found that the mean low marsh rate of elevation change (7.7 ± 3.21 mm year−1) was double the mean high marsh rate (3.6 ± 0.47 mm year−1) and exceeded the natural reference marsh (3.0 ± 2.28 mm year−1) and relative SLR (5.7 mm year−1). By stimulating organic matter production, the high nutrient substrate appears to offset the low inorganic sediment inputs in mid-Chesapeake Bay. Spatial variability was correlated with initial elevation, but was also influenced by local factors that may affect sediment redistribution within the marshes. [ABSTRACT FROM AUTHOR]

The motion of particle clouds (i.e., sediment clouds) usually can be found in engineering applications such as wastewater discharge, land reclamation, and marine bed capping. In this paper, a series of laboratory tests are conducted on coral sand to investigate the shape feature of the single particle and the mixing processes of the coral sand particle clouds. The shape of coral sand particle is measured and quantified. The experimental results demonstrate that the shape of coral sand particles tends to be spherical as the particle size decreases, and empirical equations were established to explain the variation of D50 and fS,50 of coral sand. Compared with the silica sand, the evolution of the coral sand particle cloud still experiences three stages, but the threshold for the Reynolds number of particle clouds entering the next stage changes. Further, the normalized axial distance of the coral sand particle clouds is 58% smaller. The frontal velocity exhibits similar varying tendency for the coral sand particle cloud. Considering the difference in shape between coral sand particles and silica sand particles, a semi-empirical formula was proposed based on the original silica sand prediction formula by adding the shape factor and the experimental data of 122 µm⩽D50⩽842 µm. It can predict the frontal velocity of the coral sand particle clouds. [ABSTRACT FROM AUTHOR]

In natural tidal marshes, nutrient fertilization stimulates complex responses, bringing into question the suitability of nutrient-rich dredged material as a substrate for tidal marsh restoration. We examined vegetation and elevation trends in the constructed tidal marshes at Poplar Island, Maryland where fine-grained dredged material (high nutrient) and locally dredged sand (low nutrient) were used as substrates. Macrophyte production was higher and root:shoot ratios lower in dredged material marshes. Measured vertical accretion was similar in dredged material (7.4 ± 0.6 mm y−1) and sand (6.4 ± 0.9 mm y−1) marshes, and is keeping pace with local sea-level rise. A detailed carbon budget was developed for one dredged material marsh to examine carbon dynamics under high nutrient availability. High annual macrophyte production combined with small exports via tidal exchange and methane emissions resulted in an annual carbon burial of 206 g C m−2 y−1, and calculated vertical accretion of 6.5 mm y−1 from organic matter. This is attributed to the contribution of organic matter from aboveground biomass due to protection from perimeter dikes constructed to contain dredged material during placement, reducing marsh exposure and organic matter export. With appropriate design and management, fine-grained, high-nutrient dredged material makes a suitable substrate for tidal marsh restoration. [ABSTRACT FROM AUTHOR]

Soil physical, chemical and bio-geochemical properties of a back barrier island coastal marsh restored by low pressure hydraulic dredging were monitored and analyzed from 2005 to 2009. A 109 ha restored marsh located at Port Fourchon, Louisiana, was divided into five habitats based on elevation. The habitats were classified as high (knoll), flat (swale), upper intertidal, intertidal and open water (submerged soils). The higher habitats were created nearer the dredged material source by deposited dredged coarser sediment mainly sand and oyster shells in mounds. Material with higher clay and silt content in the slurry were found in the habitats located at greater distances from the dredged material source. Soil elemental contents were statistically significantly different among habitats. Soil redox potential was also significantly different among habitats with the higher elevations having more oxidized redox values. Soil elevation was a strong influence on soil physical and chemical properties for several years post construction. Uneven distribution of dredged materials during the construction phase resulted in distinct variation in elevation and soil properties and the conclusion was that marsh creation would be more effective if dredged materials were uniformly distributed. [ABSTRACT FROM AUTHOR]

This article deals with the legal and practical recommendations for the management of dredged material in the riparian countries of the Baltic Sea. The recommendations are contained in three conventions: LC, 2000. London Convention (1972), Convention on the Protection of the Marine Environment of the Baltic Sea area (Helsinki Convention) (1992), the OSPAR Convention (1972). Different approaches to evaluating the contamination level of dredge spoils, used by the Baltic Sea riparian countries, have been characterized. The differences in those approaches manifest themselves by various concentration limits for contaminants, which form a basis for the classification of dredged material as either contaminated or non-contaminated, and thus determine how the spoils will be processed further. Based on the collected information about the concentration limits for contaminants of surface sediments in the coastal ports, it was pointed out that it is necessary to conduct routine monitoring of heavy metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, tributyltin, and petroleum hydrocarbons in dredged sediments in all the Baltic Sea states. On the other hand, the monitoring of polychlorinated dibenzo-p-dioxins/furans, organochlorine, and organophosphoric pesticides is only needed in locations that are suspected of historical or being the local contamination sources. Due to significant economic limitations of chemical determinations, it is important to consider a simple screening test of sediment that would say whether sediment may be 'contaminated' and qualifies for more detailed and costly chemical research. It may be typical basic physical-chemical analysis of sediments or ecotoxicological classification of sediments. Despite environmentally friendly tendencies, the practical application of dredged material within the Baltic Sea area is very limited. Dredged material is most frequently stored at the specifically designated sites. From among the practical uses of dredge spoils, beach nourishment is of the highest significance. In the conclusion, the new proposed management procedure of dredged material was presented. [ABSTRACT FROM AUTHOR]

The availability of steelmaking slag, an industrial by-product, was examined as a component of a basal medium for the creation and regeneration of shallow habitats in coastal ecosystems. We investigated nutrient dynamics in sediments prepared with slag and dredged materials by conducting a core incubation experiment for 379 days. Silica sand was used as the reference material. Although slag caused alkalization of pore water, the pH in the surface layer recovered within a few days. The use of slag had limited influence on the dissolved inorganic nitrogen content, but pore water phosphate concentrations were considerably suppressed in slag-based media, especially when the pH was high. Nutrient diffusion fluxes from slag- and sand-based sediment cores were comparable to those in natural coastal environments. After 379 days, more than 90 % of the nutrients remained in the top 5 cm of the cores. Moreover, the sustained release of nutrients from basal media prepared with slag may play an important role in sustaining the productivity of macrophytobenthic ecosystems, including seagrass meadows. The mesocosm-scale experiment we proposed could evaluate long-term variations of nutrient dynamics in the artificial basal media. Because of wide variations in chemical properties among the different types of slag and dredged materials, approaches similar to this study may be essential before any large-scale application to marine environments. [ABSTRACT FROM AUTHOR]

Sediment is a natural resource that provides the foundation for living, working and building in lowland delta areas. A sustainable society, therefore, reuses dredged material as a valuable resource. Such reuse matches perfectly to the philosophy of a circular economy. However, it is not yet a common practice. Why is this, what are the bottlenecks and how do we overcome them? Here, we use the Netherlands as an example to illustrate possible solutions to these questions, although we believe that our messages and recommendations can be applied generically. [ABSTRACT FROM AUTHOR]

In many coastal regions, the disposal of dredged material constitutes the largest (albeit often localised) anthropogenic disturbance to the seabed. Impacts can be minimised by reducing the amount of sediment overburden on the bed at any one time allowing short-term recovery to proceed via the vertical migration of resident species. However, there is currently a limited understanding of the ability of such species to successfully vertically migrate. This study presents the findings of a field experiment to investigate the vertical migratory capability of temperate macroinvertebrate species following the placement of simulated dredged material. The relationships between vertical migration success with sediment characteristics (organic carbon and sand content) and placement depth were explicitly examined. While the polychaete worms Tharyx sp. A. and Streblospio shrubsolii showed poor vertical migration with only 6 cm of sediment overburden, the oligochaete Tubificoides benedii showed some recovery while the gastropod mollusc Hydrobia ulvae exhibited good migratory success, even with 16 cm of sediment overburden. While increases in sand content from 16% to 38% had no noticeable effect on vertical migration, increased sediment organic content from 0.8% to 3.3% detrimentally affected vertical migratory activity. The results support the theory that species' survival following sediment burial is trophic group-related. The relevance of these findings with respect to dredged material disposal management is discussed. [ABSTRACT FROM AUTHOR]

This paper presents a harmonised framework of sediment quality assessment and dredging material characterisation for estuaries and port zones of North and South Atlantic. This framework, based on the weight-of-evidence approach, provides a structure and a process for conducting sediment/dredging material assessment that leads to a decision. The main structure consists of "step 1" (examination of available data); "step 2" (chemical characterisation and toxicity assessment); "decision 1" (any chemical level higher than reference values? are sediments toxic?); "step 3" (assessment of benthic community structure); "step 4" (integration of the results); "decision 2" (are sediments toxic or benthic community impaired?); "step 5" (construction of the decisionmatrix) and "decision 3" (is there environmental risk?). The sequence of assessments may be interrupted when the information obtained is judged to be sufficient for a correct characterisation of the risk posed by the sediments/dredging material. This framework brought novel features compared to other sediment/dredging material risk assessment frameworks: data integration through multivariate analysis allows the identification of which samples are toxic and/or related to impaired benthic communities; it also discriminates the chemicals responsible for negative biological effects; and the framework dispenses the use of a reference area. We demonstrated the successful application of this framework in different port and estuarine zones of the North (Gulf of Cádiz) and South Atlantic (Santos and Paranaguá Estuarine Systems). [ABSTRACT FROM AUTHOR]

Sediment toxicity of different areas of Spanish littoral was evaluated using an internationally recommended 10 day acute toxicity test with the amphipod Ampelisca brevicornis. Sediment samples from Santander Bay (N Spain), Las Palmas of Gran Canaria (SW Spain), Algeciras Bay (S Spain) and Ría of Huelva (SW Spain) were collected and organic carbon, fines, metals Zn, Cd, Pb, Cu, Ni, Co and Hg, PAHs and PCBs were analyzed for their characterization. Significant toxic effects compared with control site (P<0.05) were observed after exposure to the sediments from Las Palmas of Gran Canaria port, from 83.3% of the sites studied in Algeciras Bay and from Ría of Huelva. These effects were associated (P<0.05) with PCBs and metals Zn, Cd, Pb and Cu in Ría of Huelva and to Ni and Co in the rest of sites. Chemical measurements were compared with international sediment quality guidelines and site-specific guidelines were derived. [ABSTRACT FROM AUTHOR]

Artificial sediment enhancement using a thin layer of dredged material has been suggested as a means to increase elevation and create soil conditions conducive to increased marsh structure and function in deteriorating marshes. Using a chronosequence approach, we examined the effects of sediment enhancement in deteriorating marsh and open-water pond habitats located in six brackish marshes. Sediment enhancement of both marsh and interior pond sites had significant, immediate, and long-lasting effects on physical soil properties and nutrient status with increased bulk density and inorganic nitrogen. Vegetative cover and productivity response were minimal for deteriorating vegetated marshes with the short- term response data showing no significant impact of sediment enhancement and long-term trends indicating decreasing productivity over time. In contrast, trajectory models of vegetative cover and productivity in interior pond sites showed increases over time indicating that, for restoration of interior ponds, sediment enhancement may prove valuable. The use of trajectory models emphasizes the need for long- term monitoring to determine restoration success of projects. [ABSTRACT FROM AUTHOR]

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The effect of salinity on the concentration of metals in Spartina alterniflora tissues and excreted salts and the distribution of metals between these compartments was tested in a greenhouse experiment. S. alterniflora stems were planted in pots of dredge sediment that was amended with a suite of six metals (Cd, Cr, Cu, Ni, Pb, and Zn). The overlying water of individual pots was maintained at treatment salinities of 0, 15, or 30 practical salinity units. The proportion of total metal distributed to the tissues and excreted salt of S. alterniflora was not significantly influenced by salinity for any of the metals. The concentration of Pb in root and leaf tissues and in excreted salt was influenced by salinity, as was the concentration of Zn in root tissue and excreted salt. Contrary to expectations, the concentration of Pb and Zn in excreted salts decreased as salinity increased. Although the influence of salinity on the concentration of Pb and Zn in S. alterniflora tissue has not been previously reported, the influence of salinity on the tissue concentrations of Pb agrees with previous research on dicots. [ABSTRACT FROM AUTHOR]

Recent research efforts in sediment and dredged material assessment research have focused on the inclusion of sublethal endpoints (biomarkers) in acute and long-term bioassays for dredged material characterisation and management. The incorporation of biomarkers as a new line of evidence in a weight of evidence approach allows the determination of more sensitive, longer-term biological information for use in laboratory and in situ sediment/tissue quality guidelines. [ABSTRACT FROM AUTHOR]

Background. Under anoxic conditions typically prevailing in disposal sites for dredged sediment, methanogenesis is the terminal step during microbial degradation of sediment organic matter. Sediment gas production may pose several problems to site management and post-closure utilisation. Depending on the magnitude of gas/methane formation and the intended utilisation of the site, countermeasures will have to be effected during and after deposition of the dredged material. For this purpose it may be of interest to pre-estimate the extent of gas formation from simple sediment variables. Therefore, the aim of the investigations presented here was to analyse the interrelations between gas formation and sediment physical, chemical and biological qualities. Methods. Freshly sampled riverbed sediment from nine German federal waterways was analysed for standard solid physical and chemical parameters, pore water composition, cell counts of methanogenic and sulfate-reducing bacteria, and gas formation over a period of 500 days. Particle size and density fractionation were carried out in order to characterise organic matter quality. Correlations between methane formation and sediment chemical, physical and microbiological characteristics were tested using linear and multiple correlation analysis. Results and Discussion. The selected sediments, including two with marine influence, differed strongly regarding texture, chemical parameters, pore water composition, and methanogen cell counts. The course of methane formation was found to follow distinct phases. The commencement of methane formation was preceded by a lag phase of variable duration. The lag phase was followed by a strong increase of the methane formation rate up to a sediment-characteristic maximum of 5–30 nmol CH4 h-1 g dw-1. Eventually, the rate of methane formation decreased and reached a more stable, long-term level. The extent and amplitude of each phase varied strongly between sediments and could be correlated well with only a few standard analytical parameters, despite the strong heterogeneity of sediment with respect to chemical, physical, and biological characteristics. Lag phase duration depended strongly on the content of inorganic electron acceptors and also on the number of methanogens present at the beginning of the experiment. Maximum and steady state methanogenesis were mainly determined by sediment total nitrogen. As analysis of sediment density fractions revealed that total nitrogen reflected the share of readily degradable macroorganic matter. Conclusion and Outlook. The results imply that the observed methane formation is a function of the temporally changing balance of the availability of electron acceptors and H2, and the share of easily degradable organic matter. For fresh riverbed sediments, the latter may be deduced from total nitrogen content. Overall, the results showed that methane formation by freshly dredged material may well be pre-estimated from standard analytical data within the first few years of deposition. However, the differently degradable organic matter pools will change over time with respect to size, chemical nature and association with the sediment mineral phase. It can thus be expected that the correlations found in this study will not be readily transferable to older materials. Further studies on the gas formation and organic matter quality by older sediments, e.g. from older dredged material disposal sites of known age, should be conducted and results should be combined with existing organic matter degradation models in order to improve the prediction of sediment gas formation over time. [ABSTRACT FROM AUTHOR]

Dredged material levees in coastal Louisiana are normally associated with pipeline canals or, more frequently, canals dredged through the wetlands to allow access to drilling locations for mineral extraction. The hydrologic impact on marshes behind the levee is of concern to coastal resource managers because of the potential impact on sediment transport and deposition, and the effect on estuarine organism access to valuable nursery habitat. This study examined the effects of gaps in dredged material levees, compared to continuous levees and natural channel banks, on these two aspects of marsh function. Field studies for sediment deposition were conducted biweekly for a year, and nekton samples were collected in spring and fall. Variation in nekton density among study arears and landscape types was great in part because of the inherent sampling gear issues and in part because of differences in characteristics among areas. Nekton densities were generally greater in natural compared to leveed and gapped landscapes. Differences in landscape type did not explain patterns in sediment deposition. The gaps examined appear to be too restrictive of marsh flooding to provide efficient movements of floodwaters onto the marsh during moderate flooding events. The “trapping” effect of the levees increases sediment deposition during extreme events. Gapping material levees may be an effective method of partially restoring upper marsh connection to nekton, but this method may work best in lower elevation marshes where nekton use is greater. [ABSTRACT FROM AUTHOR]

Data from the Elbe River and its tributaries indicate, despite extensive improvement in water quality during the last 15 years, that the respective sediment situation of many priority pollutants has not reached an acceptable level. For the coming decades, risks for downstream sites and stakeholders will persist, mainly due to secondary sources originating from historical pollution of soils and sediments in the catchment area. In practice, a catchment-wide assessment of historical contaminated soil and sediment should apply a three-step approach: (i) Identification of substances of concern (s.o.c.) and their classification into ’hazard classes of compounds’; (ii) identification of areas of concern (a.o.c.) and their classification into ‘hazard classes of sites’; (iii) identification of areas of risk (a.o.r.) and their assessment relative to each other with regard to the probability of polluting the sediments in the downstream reaches. The conversion of this concept has to consider the underlying philosophy of the EU Water Framework Directive, particularly with respect to the analysis and monitoring of priority substances in solid matrices. However, major deficiencies are still in the assessment and prognosis of resuspension processes, and potential approaches to fill this gap are described both in theory and from examples of the Elbe River. The sediment stability testing facilities consist of a unique triple set developed by innovative experimental laboratory and field research. The instrumental facilities consisting of a tube corer and a pressurized channel allow one to measure not only the onset of erosion (critical bed shear stress), but also the erosion rate for different sediment layers. Undisturbed sediment samples were taken from contaminated sites, e.g. in near-bank groyne fields and floodplains, using (i) core sampler (diameter 14 cm, length 150 cm) for sediment erodibility depth profiling and (ii) box sampler (30*70 cm2 top view area, 28 cm depth) for comparing and upscaling the results from the laboratory to the field. Sediment properties such as grain size spectrum (laser beam attenuation), water and gas content were analyzed by a non-intrusive, high frequency, capacity measurement method and bulk density by γ-ray. Sediment core samples from flooded areas in the Middle Elbe indicate, that, except from the uppermost 5 cm and at a depth of from 47 to 48 cm, where the critical shear stress is very low (0.5 Pa), the critical bottom shear stress is between 1.2 Pa and 3.4 Pa, i.e. at a moderate level. Major reasons for the distinct heterogeneity of the erosion stability are differences in consolidation processes, grain size distribution and in the composition of stabilizing exudates in the individual sediment layers. Similar to the erosion stability depth profile, the metal data exhibit short-range heterogeneities; the variations in the individual layers can be explained by different proportions of fine grained components and by an improvement of suspended matter quality in the course of time. A comparison of the metal contents of embanked alluvial soils and unembanked alluvial areas suggests the following causal chain: Recent floodplain areas at low mean water levels exhibiting high concentrations of organic carbon represent the most highly contaminated sites. On the other hand, insignificant pollution has occurred on alluvial areas, which were embanked already at pre-industrial times. In the case of flood events, due to the combination of flooding probability and flow conditions, the most favorable conditions for the deposition of nutrient- and contaminant-rich suspended particulate matter are found in the low level depressions with low current... [ABSTRACT FROM AUTHOR]

The disposal of maintenance dredged material constitutes one of the most important problems in coastal zone management. To minimise ecological impacts, a number of ‘beneficial use’ options have developed whereby the material is regarded as a potential resource and used to recharge or recreate intertidal habitats. This paper presents the results of a sampling programme to investigate the macrofaunal recovery rates, and the underlying mechanisms responsible for them, following a beneficial use scheme involving the placement of fine-grained dredged material on a salt marsh in southeast England. Three stations in the recharge area and three reference stations, located within the same salt marsh system, were selected. These stations were sampled prior to recharge (recharge stations only) then 1 week, 3, 6, 12 and 18 months after the recharge. Sediment redox potentials (1, 2 and 4 cm sediment depths) were also measured on each sampling occasion. The results indicated a rapid recolonization of the fauna typical of the surrounding salt marsh channels. All univariate parameters had recovered after 3 months after the recharge. Active post-juvenile immigration is likely to have been the predominant recovery process. Multivariate data analysis revealed that the community structure of the recharge stations, however, did not progress towards those of the reference sites. Natural spatial variability in community structure at the scale of the recharge-reference station distance, and differences in eventual tidal elevations are factors responsible for these differences. The need to carefully assess reference site suitability in monitoring beneficial use schemes is discussed. [ABSTRACT FROM AUTHOR]

Disposal of dredged material in subaqueous depots is increasingly considered an economic and ecologically sound option in managing contaminated dredged material. The concept of subaqueous disposals capped with active barrier systems has been developed to minimize this risk of contaminant release. As such a depot represents a permanent installation within a sensitive ecosystem, it requires a thorough monitoring concept. It is the goal of this work to develop such a concept regarding general considerations and results of laboratory and field investigations. In addition to the state-of-the-art techniques developed for other under-water constructions, this monitoring concept is developed with particular respect to the chemical isolation of the dredged material from the overlying water body. It comprises the use of seepage meters, dialysis samplers, and DGT gel probes for determining the migration of selected target solutes. The capability of the dialysis samplers is demonstrated by comparing field results with model calculations. The appropriateness of DGT probes to assess the impact of humic substances on trace metal speciation and on copper toxicity is demonstrated with the aid of laboratory experiments. The experimental results show that, by using dialysis samplers, the temporal changes in concentration-depth-profiles of heavy metals in the pore solution can be monitored. Additionally, the application of DGT probes facilitates the in situ detection of labile species of a metal in the presence of dissolved humic substances, which serves to reflect its toxicity. Conclusions. Three subsequent monitoring phases are distinguished on the basis of both general considerations and the findings from field results: A hydraulic phase that is characterized by compaction and pore water expulsion, a geochemical phase in which the demobilization of pollutants can occur due to substantial changes in the physico-chemical conditions (pH, EH), and a steady-state-phase where pore water flow and geochemical conditions are approaching their minimum. The monitoring concept suggested here provides a versatile tool to assess the chemical isolation of subaqueous sediment depots and other contaminated sediment sites. This is of great importance as subaqueous disposal is increasingly considered a future management strategy as space for upland disposal is limited and treatment, in general, proves to be too costly. [ABSTRACT FROM AUTHOR]

In the Netherlands about 40 million m3 of sediment has to be dredged annually for both maintenance and environmental reasons. Temporary upland disposal is the most widely adopted alternative for dredged sediments worldwide. For good management of temporary disposal sites, knowledge is needed on the processes controlling the behavior of the sediments during disposal. Therefore, a review of the literature was made to get an integrated overview about processes that take place during temporary disposal. After disposal of clayey sediments, the following spontaneous dewatering processes can be distinguished: sedimentation, consolidation, and ripening. Sedimentation and consolidation are relatively fast processes, whereas ripening can take up to several years. In a remediation perspective, the ripening of sediments is the most important dewatering process. Ripening, which may be subdivided into physical, chemical, and biological ripening, transforms sediment into soil. Physical ripening is the irteversible toss of water and results in the formation of soil prisms separated by shrinkage cracks. Continuing water loss causes a breaking up of the prisms into aggregates. The aggregates produced by this ongoing desiccation process usually remain quite large (>50 mm) and can only be further broken down by weathering processes like wetting and drying or by tillage. As a result of the aeration caused by physical ripening, also chemical and biological ripening take place. Chemical ripening can be defined as the changes in chemical composition due to oxidation reactions and leaching of soluble substances. Biological ripening is the result of the activity of all kinds of soil fauna and flora that develop as a result of aeration, including both the larger and the microscopic forms of life. Decomposition and mineralization of soil organic matter caused by micro-organisms can be seen as the most important aspect of biological ripening. Many interactions exist between the different ripening processes. Oxygenation of the dredged sediment is improved as a result of the natural ripening processes: the air-filled porosity increases, the aggregate size decreases, and the initially high respiration rates caused by chemical and biological ripening decreases. Therefore, conditions in the disposal site become more favorable for aerobic biodegradation of organic pollutants like Polycyclic Aromatic Hydrocarbons (PAH) and mineral oil. It is concluded that the naturally occurring process of ripening can be used as a bioremediation technique. Ripening in an upland disposal site is an off-site technique, and therefore, the process could be enhanced by means of technological interference. However, it is concluded that the knowledge currently available about upland disposal is not sufficient to distinguish critical process steps during the ripening and bioremediation of PAH and mineral oil polluted sediments because of the complex relationships between the different ripening processes and bioremediation. [ABSTRACT FROM AUTHOR]

Industrial activities in the river basin of the Elbe have a very long tradition, and have been resulting in the contamination of sediments for centuries. Contamination lasted until the fall of the iron curtain; since then, the situation has improved significantly. In the transition zone between freshwater systems and the marine environment, ports like Hamburg still have to bear this burden of history. An overall (contaminated) management strategy should be developed in the context of the European Water Framework Directive with the emphasis on source control. [ABSTRACT FROM AUTHOR]

After three decades ofexperience, environmental managers continue toquestion the use of dredged material for creation andrestoration of Spartina alternifloramarshes. Different uses of the term `success' have led to someconfusion, and poor recognition of the limitations ofresearch design have contributed to confusion instudies comparing dredged material and naturalmarshes. This paper uses data from a number ofsources to compare dredged material and naturalmarshes. Quantitative analyses based on dataavailable in the scientific literature suggest thatmean values for aboveground and belowground biomass,organic carbon in sediments, polychaete densities, andcrustacean densities may differ in dredged materialand natural marshes. There is not sufficient evidenceto conclude that differences are present for othervariables, such as densities of stems, oligochaetes,or fish. Cumulative quantitative data do not supportthe contention that dredged material sites becomeincreasingly similar to nearby natural marshes overtime as a general rule, although some attributes ofindividual dredged material marshes may becomeincreasingly similar to some natural marshes. Although it is clear that dredged material marshesprovide habitat for birds, limited data suggest thatdredged material marshes may provide habitat for adifferent community of birds than natural marshes. Similarly, limited data suggest that geomorphologicalfeatures found in natural marshes are not duplicatedin dredged material marshes. In short, datasummarized from the literature suggest that dredgedmaterial marshes provide some of the functions ofnatural marshes but probably do not replace all of thefunctions of lost natural marshes. [ABSTRACT FROM AUTHOR]

Approximately 35 hectares of Spartina alterniflora marsh has, over a 14-year period, developed naturally on unconfined dredged material placed within the intertidal zone of Winyah Bay, South Carolina. The above-and below-ground vegetative structure, benthic macrofauna, and resident fish and shellfish assemblages of two varying-aged zones (4 and 8 years) of this marsh were evaluated and compared in September 1988. Vegetative structure (stem height, density, percent cover, and biomass) in both zones was within the range reported for natural sites, with a trend toward greater below-ground development with age. The macrofaunal assemblages of both zones were similar in both species composition and numbers of species (17-21 species), with oligochaetes and polychaetes dominating both assemblages. Overall density of macrofauna in the 8-year-old zone (19,943 individuals per m) was significantly greater than that in the 4-year-old zone (4,628 individuals per m). Differences between zones (particularly the presence of large-bodied molluscs in the older site) seemed to reflect age. The fish and shellfish assemblage collected from the younger site was dominated by Fundulus heteroclitus and Palaemonetes pugio. Gut contents of F. heteroclitus included a variety of marsh-surface prey, similar to that reported elsewhere. Overall, both zones seemed to represent well established, viable, low intertidal marsh habitat. [ABSTRACT FROM AUTHOR]

Windmill Point (WP) is an 8-ha dredged material island site in the intertidal reach of the James River. This fine-textured, freshwater site was one of the first habitat development projects built by the U. S. Army Corps of Engineers (CE). Long-term physical, chemical, and biological monitoring has been conducted since 1974. Three nearby natural wetlands have been used for comparison purposes in order to document site success or failure and the speed of wetland development. With the exception of some herbaceous plantings on the WP containment dikes, vegetation has colonized naturally. Over time, predominant species have been Peltandra virginica, Pontederia cordata, and Sagittaria latifolia. Wild-life and fish populations and species diversity have been consistently greater at WP than at the 3 reference wetlands. Benthos regained pre-disposal levels within 6 months. Five heavy metals and 14 PCBs were examined in soil and plant samples. Only DDE was found to translocate to wetland plant shoots, and kepone was found to be relatively stable. WP was broken into 2 smaller islands by flooding in 1983 and now consists of as much shallow aquatic habitat as emergent wetlands. The CE recognizes that active site management of such riverine wetlands through placement of additional dredged material and dike repair is needed to ensure long-term site integrity. [ABSTRACT FROM AUTHOR]

A numerical model to predict the migration rate of submerged mound constructed by dredged materials due to waves is developed in this paper. The model is based on Bailard's sediment transport rate formula, Stokes' second-order wave theory, and the sediment balance equation. Particularly, the suspended load is included into the present numerical model, so that it may be possible to estimate the migration of mound composed of the mixture sediment accurately. The numerical model is satisfactorily verified by comparison of the numerical results with the field data measured both at Silver Strand mound and at Tauranga mound. The convection-dispersion processes, by which the crest of mound is flatted and moved shoreward at the same time, are generated by the present numerical model very well. In addition, it is found that the migration of mound depends directly on the wave height, the sediment size and the wave period through the analyses on the characteristics of mound migration. The dependence of mound migration on the wave height and the sediment size is relatively stronger than that on the wave period. [ABSTRACT FROM AUTHOR]