Ceramic processing of polluted dredged mud

About 45 million m³ of bottom sediment, with an estimated dry matter content of 30%, have to be dredged annually in the Netherlands, of which several million m³ are strongly contaminated with heavy metals and toxic organic substances. Contaminated dredged muds are dumped in special locations on land.The problems of severely polluted muds are likely to remain from many decades to come, and the present disposal reserve may not be adequate. In a densely populated country, large-scale disposal on land is not a satisfactory long-term solution, and a method of cleaning these muds has to be developed. This paper presents some of the results of an investigation into the feasibility of ceramically processing severely polluted dredged muds. Ceramic processing not only destroys the organic micro-pollutants; the leaching of heavy metals is reduced by ceramic bonding and the end-product is a hard, lightweight gravel-size particulate, useful as a building material. Extensive tests have been carried out on the leaching behaviour of the ceramic products and the results showed little or no differences in comparison with other commonly used building materials; the results are better than those of aggregates made from pulverized fuel ashes.     

A sensitive screening bioassay technique for the toxicological assessment of small quantities of contaminated bottom or suspended sediments

Biological impact assessment of sediment-bound contaminants is currently considered essential in addition to routine chemical characterization. Conventional methods of sediment bioassessment require relatively large quantities of the sample. When sample sizes are limited however, these methods become ineffective. To overcome this problem, the Limited Sample Bioassay (LSB) technique was developed. Bioassays conducted with bottom sediments and suspended particulates from western, central and Arctic regions of Canada indicated that the newly developed LSB technique successfully evaluated the contaminant/nutrient impact on laboratory-grown cultures of algae. The LSB method produced results which were comparable to those from standard elutriate bioassays conducted with natural phytoplankton size assemblages. The data suggest that the LSB can play an important role in providing a quick, simple, sensitive, and inexpensive screening technique for assessing the bioavailability of contaminants (or nutrients) from sediment of limited quantity.     

Development of a protocol for recognizing sulfidic sediments (potential acid sulfate soils) in freshwater wetlands

Summary   The presence of sulfidic sediments (potential acid sulfate soils) is an emerging problem in the management of inland wetlands. Using data from 81 wetlands in the Murray-Darling Basin, a simple protocol was developed to assess whether a wetland will contain sulfidic sediments at levels that could cause ecological damage. Risk factors include whether or not the wetland receives municipal waste or irrigation return water, elevated salinity in the overlying water (>1750 µS/cm) or sediment (400 µS/cm in a 1:5 soil : water extract) and high levels of sulfate in the water column (>10 mg/L). Neutral or basic sediment pH indicates that, even if the sediment does contain sulfidic sediments, there is a reduced likelihood of acidification if the sediments are oxidized.     

Probabilistic Risk Assessment and Risk Mapping of Sediment Metals in Sydney Harbour Embayments

Sediment metal concentrations in embayments of Sydney Harbour, acquired from the literature and from samples collected for this study, were used to generate contaminant probability density distributions using AQUARISK. The sediment metal concentrations often exceeded Australia's interim sediment quality guidelines. Similarly, estuarine spiked sediment toxicity test literature provided adverse biotic effects concentration data to generate species sensitivity distributions using AQUARISK. Although the harbor is subject to other inorganic and organic contamination, we have used sediment metals to demonstrate an approach for ecological risk mapping and environmental management prioritization. Sufficient spiked sediment toxicity test data were found for only three metals—Cd, Cu, and Zn—and some tests were likely to overestimate toxicity. The estimates of the hazardous concentration to 5% of species (the 50th percentile of the 95% species protection level) were 5, 12, and 40 mg/kg DW of total sediment metal for Cd, Cu, and Zn, respectively. These values were generally low when compared with the interim sediment quality guidelines due to the overestimation of toxic effects in the literature data. The parameters for the species sensitivity distributions have been combined with the measured sediment metal concentrations in Homebush Bay to generate risk maps of the estimated species impact for each metal as well as for all three metals collectively assuming proportional additivity. This has demonstrated the utility of comparing contaminants on a consistent scale—ecological risk.     

Influence of Emergent and Submerged Macrophytes on the Structure of Planktonic Ciliate Communities in Shallow Freshwater Lakes (Eastern Poland)

Data from two shallow macrophyte‐dominated lakes (Eastern Poland) sampled with standardized methods, were evaluated in order to examine the effects of various stands of macrophytes in predicting protozooplankton community structure. Differences in macrophyte structure led to two distinct groups of habitats having different patterns of ciliate distribution. The first group consists of two vegetated habitats of sparse stem density and of the open water zone, and the second of submerged macrophyte species, which were more dense and complex. The number of significant correlations was different in the studied habitats. In central zones of macrophyte habitats the number of ciliates had the strongest correlation with concentrations of total organic carbon and P_tot. On the other side in the border zone a significant correlation between the number of ciliates and the chlorophyll a concentration was found. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Bathymetric distribution of fossil foraminifera within marine sediment cores from the eastern part of Lützow-Holm Bay, East Antarctica, and its paleoceanographic implications

Faunal analysis of fossil foraminifera from marine gravity and piston cores collected by the Japanese Antarctic Research Expeditions (1981 and 1992) is used to estimate the impact of the latest Quaternary paleoceanography on coastal environments of the eastern part of Lützow-Holm Bay, East Antarctica.Accelerator Mass Spectrometry (AMS) carbon-14 ages produced from sedimentary organic carbon were less than 16 ka (non-corrected). Detailed correlation among submarine cores and Holocene elevated marine deposits exposed on the eastern shore of the embayment is difficult due to the indefinite reservoir correction value for marine organic matter and to upward-increasing abnormal ages for some cores.A local carbonate dissolution level can be delineated around the present depth of 300–400 m or shallower in the eastern part of Lützow-Holm Bay during the Holocene, based on distributional trends of arenaceous, calcareous benthic, and planktonic foraminifera recognized within a depth less than 600 m. Downcore recovery of calcareous foraminifera containing Bulimina aculeata from two cores obtained in a drowned glacial trough deeper than 600 m situated far beyond the dissolution depth of CaCO₃ indicates the incursion of warm, high-nutrient, and CaCO₃-saturated Circumpolar Deep Water (CDW) from the offshore area along the trough toward the southeastern coast of Lützow-Holm Bay during the Holocene. The intrusion of CDW impacted on the marine environments of the southeastern coast, thereby contributing to peripheral retreat of the ice sheet as well as increasing calcareous benthic foraminiferal productivity along the southeastern coast of Lützow-Holm Bay.     

Effects of Holocene Alnus Expansion on Aquatic Productivity, Nitrogen Cycling, and Soil Development in Southwestern Alaska

Numerous pollen records provide evidence for the widespread range expansion of Alnus throughout Alaska and adjacent Canada during the middle Holocene. Because Alnus can fix atmospheric N₂, this vegetational change probably had a profound effect on N availability and cycling. To assess this effect, we analyzed a sediment core from Grandfather Lake in southwestern Alaska for a suite of geochemical indicators, including elemental composition, biogenic silica (BSi) content, and carbon (C) and nitrogen (N) isotopes of organic matter. These data, in conjunction with a pollen record from the same site, are used to infer biogeochemical processes associated with the mid-Holocene Alnus expansion. The increase in Alnus pollen percentages from 10% to 70% circa 8000-7000 BP (¹⁴C years before present) suggests the rapid spread of Alnus shrub thickets on mountain slopes and riparian zones in the Grandfather Lake region. Coincident with this vegetational change, the mean value of the sediment BSi content increases from 20.4 to 106.2 mg/g, reflecting increased diatom productivity within the lake as a result of Alnus N₂ fixation in the watershed soils and the associated N flux to the lake. Elevated aquatic productivity at this time is also supported by increased percentages of organic C and N, decreased C:N ratios, and decreased values of δ ¹³C. Furthermore, the δ ¹⁵N values of sediments increase substantially with the establishment of Alnus shrub thickets, suggesting enhanced N availability and accelerated N cycling within the lake and its watershed. Superimposed on a general trend of soil acidification throughout the postglacial period, soil acidity probably increased as a result of the Alnus expansion, as can be inferred from decreasing ratios of authigenic base cations to allogenic silica (Si) and increasing ratios of authigenic aluminum (Al) to allogenic Si. The ultimate cause of these mid-Holocene ecosystem changes was an increase in effective moisture in the region. Received 21 July 2000; accepted 3 January 2001.     

The structure of micromycete complexes in permafrost and cryopegs of the arctic

A comparative study of the structure of micromycete complexes has been performed. The samples of micromycetes were taken by boring from unique habitats: cryopegs (lenses of non-freezing hypersaline water in ancient permafrost horizons) and permafrost Arctic sediments of different age enclosing these cryopegs. The possibility of characterizing the above habitats by the structure of specific complexes of microscopic fungi using qualitative and quantitative indices at extremely low numbers of these organisms was demonstrated.     

Vertical and lateral variations in coccolithophore community structure across the subtropical frontal zone in the South Atlantic Ocean

In this study the coccolithophore compositions of 11 plankton depth stations along a N–S transect from the South Atlantic Subtropical Gyre to the Subantarctic Zone were examined qualitatively and quantitatively. The lateral and vertical distribution patterns of not only the most abundant taxa but also of the morphotypes of distinct species complexes, such as Calcidiscus leptoporus, Emiliania huxleyi, and Umbellosphaera tenuis were the focus. Geographic variation among morphotypes mirrors different ecological affinities of the members of a species complex. Multivariate statistics were used to infer the relationship between a set of known environmental data and species concentrations. The results of the detrended Canonical Correspondence Analysis (CCA) revealed the presence of distinct species assemblages. The Subtropical Gyre assemblage within the upper 50 m of the photic zone is mainly composed of Umbellosphaera irregularis, U. tenuis types III and IV, Discosphaera tubifera, Rhabdosphaera clavigera, S. pulchra and E. huxleyi var. corona, adapted to warm and oligotrophic conditions. In the deeper photic zone abundant Florisphaera profunda, Gephyrocapsa ericsonii and Oolithotus spp. are encountered, benefiting from higher nutrient concentrations in the vicinity of the nutricline. A well-defined Subtropical Frontal Zone (STFZ) association is clearly dominated by E. huxleyi types A and C throughout the upper 100 m of the water column. Secondary contributors in the upper photic zone are Syracosphaera spp. (mainly S. histrica, S. molischii), Michaelsarsia elegans, Ophiaster spp. and U. tenuis type II. This assemblage is associated with cooler, nutrient-rich waters. E. huxleyi type B is found deeper in the water column. Here it is accompanied by Algirosphaera robusta, G. muellerae, and S. anthos indicating a tolerance of lower light availability in environments with elevated productivity. C. leptoporus spp. leptoporus shows relatively high cell numbers in all sampled water levels throughout the STFZ. Interestingly, its coccoliths are often smaller 5 μm in lith diameter. The mean coccolithophore assemblages of a station were compared to the underlying surface sediment assemblages. For the most part, the distribution of the morphotypes is reflected in the sedimentary archive, thus proving their potential as paleoecological proxies.     

Upper Holocene dry land vegetation in the Moravian–Slovakian borderland (Czech and Slovak Republics)

Five pollen diagrams representing the upper Holocene vegetation and its anthropogenic changes are presented and evaluated. They come from small spring fens in the Czech (Moravian) and Slovak borderland. The northern part of the region (the Beskydy Mts) had natural, precultural forests with either coniferous trees (Picea abies and Abies alba) or mixed with Fagus sylvatica. In the southern part of the region (the Bílé Karpaty Mts) forests dominated by Fagus mixed with Acer, Fraxinus and Ulmus prevailed, whereas conifers were almost absent, although in a central, transitional region (northern Bílé Karpaty Mts) Abies was locally abundant in relatively humid places. Medieval colonisation deforested their lower areas and foothills in the course of the 11th–13th centuries and transformed the original mixed oak forests into fields and meadows, but the mountain forests were little affected. In the Beskydy Mts in the north, the Walachian colonisation of the 16th and 17th centuries transformed parts of the mountain forests into meadows, pasture and farmlands. Most remaining woodlands were transformed during the last two centuries into spruce plantations. In the Bílé Karpaty Mts in the south, the Walachian transformation of mountain forests had already started by the 15th century. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.