A Novel Particle Contact Assay with the Yeast Saccharomyces cerevisiae (8 pp)

Goal, Scope and Background   Numerous xenobiotics released into surface waters are transferred to suspended particulate matter and finally attached to sediments. Aquatic organisms may be exposed to them by direct particle feeding, by physical contact with contaminated surfaces as an exposure route, and by the uptake of dissolved contaminants after equilibration via the free water phase. In order to assess potential sediment toxicity, each of these exposure routes has to be addressed. This paper presents a newly developed particle contact assay that uses the fermentation performance of a specific Saccharomyces cerevisiae strain for the assessment of toxic effects in sediments. The test procedure is based on the characteristic feature of growing yeast cells to attach to sediment particles, which are also relevant for the accumulation of contaminants. The physical contact with lipophilic contaminants mirrors an exposition pathway for the direct uptake into the cells. In order to quantitatively characterize the toxic effects of particle attached pollutants on the fermentation performance, unpolluted native reference sediment was spiked with representatives for widely distributed anthropogenic contaminants. Methods   Saccharomyces cerevisiae was established as sensitive eukaryotic microorganism for the ecotoxicological assessment of particle attached anthropogenic contaminants in freshwater sediments. For this purpose, yeast cells were cultivated in sediment samples and the resulting fermentation performance was continuously measured. Sediments artifically spiked with HCB, PCB, g-HCH, DDT, and benzo(a)pyrene and solutions of each contaminant were comparatively investigated by means of their adverse effects on yeast fermentation performance. Additionally, four native river sediments characterized by increasing levels of pollution were assessed by the yeast particle contact assay, and simultaneously by standard aquatic tests with algae, daphniae, and luminescent bacteria using pore water and elutriates. Results of the bioassays were related to specific sediment contamination with respect to metals and organic priority pollutants. Results and Discussion   In sediments spiked with PCB and benzo(a)pyrene fermentation, performance was affected extensively below concentrations inhibiting fermentation in contaminant solutions. This suggests a high efficiency of the exposure route by physical contact. The fermentation performance was only slightly affected by single lipophilic pollutants, whereas mixtures of individually spiked sediments caused critically reduced fermentation performance suggesting additive synergistic effects. Native river sediments modestly to critically polluted by hazardous organic compounds lead to a slightly to dangerously reduced fermentation performance in the yeast contact assay. These inhibitory effects were much less pronounced in the standard bioassays conducted with algae, daphniae and luminescent bacteria, applying pore waters and elutriates as sample matrices. Using pore water, inhibition was measured only in the most polluted sediment, elutriates lead to a slight inhibition of the algal growth in the undiluted sample only. These results indicate an improved sensitivity of the yeast particle contact assay compared to the standard assays, due to uptake and physical cell contact as additional routes of exposure. Conclusion   The yeast particle contact assay is a valuable tool for the assessment of ecotoxicological potential in freshwater sediments. Since the assay addresses physical contact as an exposure route, it indicates bioavailability of lipophilic compounds in sediments. Outlook   The sensitive indication of bioavailable contaminants associated to sediment particles by the newly developed yeast particle contact assay recommends it as a complementary microbial bioassay in a test battery for assessing major pathways of contaminants in whole sediments.     

洪水对河流底泥有机污染物分布的影响

文章结合我国１９９８ 年遭受特大洪水灾害的情况,介绍了美国密西西比河洪水对底泥有机污染物分布影响的研究成果。结果表明洪水前后所有底泥样品中都存在粪醇、多环芳烃（ 包括芘） 、直链烷基苯磺酸盐、多氯联苯和有机氯农药等污染物,浓度一般小于１ ｍｇ／ｋｇ ,其中上游浓度最高。洪水前后各种污染物浓度变化较大。洪水发生后,上游段底泥中芘和多氯联苯的浓度降低而粪醇浓度升高,这表明城市和农业水域中的污染底泥被洪水冲刷至河内并稀释或覆盖原来的底泥。并列举了这一成果给予我们的启示。     

Sediments in the Catchment-coast Continuum (7 pp)

-  Dedicated to Prof. Dr. Ulrich Förstner on his 65th birthdayBackground   Sediments pose problems at their deposition sites when there is too little sediment (e.g. wetlands) or too much sediment (e.g. navigable waterways) and, additionally, when they are contaminated. These problems often have their origin upstream in the river catchment. Objective   Global aspects of changes concerning sediment quantity and quality, as they affect downstream areas, are reviewed. A case study of estuarine sediments demonstrates how a holistic approach helps in understanding and predicting their present and future quality. Results and Conclusions   Globally, large reservoirs intercept between 25 and 30% of the sediment and consequently supply the coast with impacts on wetlands and coastal morphology. In estuaries, the composition of sediments is determined by the mixing of marine sediments supplied from the coast and the supply by rivers. Natural tracers can be used to predict mixing ratios of marine to fluvial sediments in estuaries, and hence their contamination. Scenarios on implementation of pollution abatement, the implementation of regulations as well as climate change are needed to predict future sediment quality in downstream areas. The results show, even for a ‘green’ scenario, that sediment quality in the Rhine catchment will pose future problems due to the temporal storage of contaminants in soils and sediments.Recommendations and Outlook   The current methods applied make use of existing models linking sediment transport with point and diffuse sources in the river catchments and scenarios on the development of strength of point and diffuse sources. However, more effort is needed to come to a uniform framework which includes land use changes and links with more advanced scenario methodology for long to medium-term management of sediment quality and quantity in river catchments.     

Evaluation of two bacterial delivery systems for in-situ remediation of PAH contaminated sediments

Intention, Goal and Background  Contaminated sediments represent a significant, worldwide environmental problem since they contain a mixture of different xenobiotics and heavy metals. The presence of mixed contamination presents a unique set of obstacles for remediation efforts. Often sediment remediation occurs as an ex-situ application (i.e., after dredging) in an attempt to minimize some of the problems. However, dredging poses it’s own issues. It does not address contaminated water and often material is not completely removed thereby leaving a long-term residual contamination source in the waterway. Objective  The potential of bio remediation to treat sediments contaminated with polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, and heavy metals was addressed. The primary objective was to assess two delivery mechanisms for microbial inoculation to facilitate in-situ remediation of PAH contaminated sediments. Methods  Simulated river beds were constructed to mimic the Mahoning River. Contaminated sediment from the river was added to each reactor at a uniform depth, followed by the addition of river water. Fifteen inoculation points were used in each simulated river bed to ensure adequate microbial populations. One tank was inoculated with an acclimated bacteria solution as a free suspension. The other tank was inoculated with an attached growth biofilm system. Sediment samples were taken throughout the experiment and the percent PAH degradation determined. Water characteristics (DO, pH, bacterial activity, etc.) were also tracked as corroborating evidence. Results and Discussion  The monitoring sites indicated that an attached growth system was more effective, and achieved a 99% PAH degradation efficiency at some of the sampling sites. Tracking individual PAH compounds also indicated a higher overall microbial activity with the attached growth system. This activity was evident by the formation and subsequent biodegradation of lower molecular weight degradation byproducts. However, more of the sediment area was treated by the free suspension inoculum due to the ease of microbial migration. Conclusions  The applicability of using an aerobic microbial consortium composed ofMycobacterium sp., Pseudomonas aeruginosa, andPseudomonas flourescens to treat contaminated sediment was demonstrated. In addition, it was found that introducing the consortium as an attached growth was more effective than when delivered as a free suspension. Recommendation and Outlook  The results demonstrated that the consortium was effective at treating the PAHs present in the contaminated soil. An additional study to evaluate the consortium’s effectiveness at remediating the PCB present in the sediment is warranted. Optimization of the consortium-nutrient combination could enable a treatment approach to effective for all the organic contaminants present. Although this would not address the heavy metals present in the sediment, it would afford a great opportunity at remediating a severely contaminated sediment system.     

Evaluation of a Multi-species Test System for Assessing Acute and Chronic Toxicity of Sediments and Water to Aquatic Invertebrates: Effects of Pentachlorophenol on Daphnia magna and Chironomus prasinus (6 pp)

Background, Aims and Scope   Single-species toxicity tests are currently used as main tools for assessing effects in ecological risk assessments. Nevertheless, in higher-tier evaluations, alternative ecotoxicological methods can be required. Alternative methods should cover more realistic exposure conditions and/or additional species or endpoints. Water/sediment systems can be considered for covering additional exposure routes. A typical feature of water/sediment systems is the modification of exposure levels with time. The simultaneous exposure of different species within the same system can cover differences in sensitivity and relevance of exposure routes. The aim of this study was to develop a water/sediment test that could detect relevant effects on two selected species and explore the relevance of sediment and waterborne exposure routes. This alternative method may provide relevant information facilitating the design of microcosm and mesocosm studies.Methods   A multi-species water/sediment system was designed using two invertebrates: Chironomus prasinus a benthic detritivore invertebrate and Daphnia magna a pelagic filtering invertebrate was designed. Seven static water/sediments systems were built up: two controls and five treatments where sediments were spiked with NaPCP at nominal concentrations of 1.25, 2.5, 5, 10 and 20 mg/kg, respectively. Each system contained caged and free (unrestrained) Daphnia magna organisms to consider differences in the exposure route (through sediment and/or water column) and Chironomus prasinus organisms. Fate and partitioning of PCP within the water/sediment compartments were assessed. Acute (lethality) and chronic effects (reproduction) for Daphnia magna were monitored after 48 h and 16 days of exposure, respectively. Adult emergence and oviposition success of Chironomus prasinus were monitored at the end of test (16 days).Results and Discussion   Mortality and reproduction inhibition of Daphnia magna occurred at the two higher doses, corresponding to maximum measured PCP water concentrations of 1.95 and 0.746 mg/l, respectively. Chironomus prasinus was less sensitive to PCP than Daphnia magna. Concentrations inhibiting reproduction and provoking almost 100% adult mortality in D. magna only reduced slightly the emergence and reproduction of chironomids. The experimental design focussed on suitability of the system for assessing simultaneously assessing effects on D. magna and C. prasinus instead of calculations of toxicity endpoints for PCP. The results indicate that this experimental design can be useful to the field of sediment/aquatic toxicity testing, particularly through the comparison with single- species results. Assessment of relative contribution of two exposure routes for Daphnia magna and complementary chronic endpoints derived from two different species can be achieved. Another advantage is that differences in reproduction strategies of selected species (sexual vs. parthenogenetic) should permit one to detect mechanisms of action associated to with endocrine disrupters.Conclusion   The feasibility of a two-species test built-up in an artificial sediment/water system has been demonstrated. This experimental design represents a cost/effective test which can assess effects through water and sediment pathways and incorporates several relevant chronic endpoints in a single assay. Recommendation and Outlook   By building on the experience gained, improvements for further test designs are discussed. Test validation with a set of model chemicals will contribute to address the effectiveness of the test developed as comparing compared to single- species tests.     

Chronic toxicity of unresolved complex mixtures (UCM) of hydrocarbons in marine sediments

Background, Aim and Scope  Unresolved complex mixtures (UCM) of hydrocarbons, containing many thousands of compounds which cannot be resolved by conventional gas chromatography (GC), are common contaminants of sediments but little is known of their potential to affect sediment-dwelling organisms. Evidence exists for reduced health status in mussels, arising from aqueous exposure to aromatic UCM components acting through a narcotic mode of action. However, UCM contaminants in sediments may not be sufficiently bioavailable to elicit toxic effects. The aim of our study was therefore to measure the sublethal effects of chronic exposure to model UCM-dominated oils at environmentally realistic concentrations and compare this to effects produced by a UCM containing weathered crude oil. A further aim was to determine which, if any, fractions of the oils were responsible for any observed toxicity. Materials and Methods  Whole oils were spiked into estuarine sediment to give nominal concentrations of 500 μg g⁻¹ dry weight. Juveniles of the estuarine amphipod Corophium volutator were exposed to the contaminated sediment for 35 days and their survival, growth rate and reproductive success quantified. Using an effect-directed fractionation approach, the oils were fractionated into aliphatic and two aromatic fractions by open column chromatography and their toxicity assessed by further chronic exposures using juvenile C. volutator. Results  The growth rates of amphipods were reduced following exposure to the oils although this was only statistically significant for the weathered oil; reproductive success was reduced by all oil exposures. Sediment spiked with UCM fractions also caused reduced growth and reproduction but no particular fraction was found to be responsible for the observed toxicity. Survivorship was not affected by any oil or fraction. Discussion  The study showed that chronic exposure to sediments contaminated by UCM-dominated oils could have population level effects on amphipods. The observed effects could not be explained by hydrocarbons resolved by conventional GC and effects were similar for both UCM-dominated and weathered oils. All of the fractions appeared to contribute to the observed effects; this is in contrast to previous research which had shown that an aliphatic UCM did not cause adverse effects in mussels. Conclusions  To our knowledge, this is the first study to demonstrate population-level effects arising from exposure to sediments contaminated by realistic environmental concentrations of UCM hydrocarbons. The results are consistent with many compounds, at very low individual concentrations, contributing towards the overall observed toxicity. Recommendations  Risk assessments of contaminated sediments should take into account the contribution towards the potential for toxic effects from UCM hydrocarbons. Studies into sediment contamination should report both aliphatic and aromatic UCM concentrations to aid risk assessments. ESS-Submission Editor: Henner Hollert (hollert@uni-heidelberg.de) This paper has been developed from a presentation at SETAC Europe 16^th Annual Meeting 2006 held at the The Hague, The Netherlands.     

A geochemical analytical approach for the evaluation of heavy metal distribution in lagoon sediments

Background, Aim, and Scope  Italian lagoon environments are of great importance due either to their frequency and distribution along the coasts or to their management. Agriculture, urban and industrial activities in lagoon catchments can be sources of heavy metal (HM) pollution by direct waste dumping, atmospheric deposition of fumes or, simply, as a consequence of a lack of natural water recharge. HM concentration in lagoon sediments is a tool of HM monitoring in the surrounding environment. Application of sequential extraction procedures (SEP) to sediments makes it possible to study the HM distribution among the main geochemical phases and to assess their potential mobilization as a consequence of environmental condition variations. In the present study, the three-step SEP (0.11 m HOAc; 0.1 m NH₂OH·HCl; 8.8 m H₂O₂ and then 1 m NH₄OAc), developed by the Measurement and Testing Programme of the European Commission (BCR), was combined with information on the chemical and mineralogical properties of the sediments in order to assess the level and risk of mobility of HM (Cu, Cr, Cd, Pb, Ni, Zn) in sediments from the Fusaro volcanic coastal lagoon of southern Italy. The effect of sediment air drying and physico-chemical properties on the metal distribution in various geochemical forms and fractions was considered. Materials and Methods  Surface (5 cm depth) sediment samples were collected from twenty-one sites on the Fusaro lagoon. Moisture, pH, organic carbon, carbonates, particle-size distribution and HM total content were determined on the dried sediment samples. The mineralogy of the clay fraction was determined at room temperature on random and oriented samples. The different forms of Al, Si and Fe in the bulk sediment (< 2 mm) were analyzed after oxalate, dithionite-citrate and pyrophosphate extractions. The BCR-SEP was used to fractionate trace element chemical forms in nine selected sediment samples. Effects of sediment air-drying on HM fractionation were analyzed. Results  Middle (Cu, Cr) and low (Cd, Pb, Zn) concentrations of heavy metals in sediment samples from the deeper central part of the lagoon were observed. Cadmium resulted in mainly being associated with carbonate forms (∼60%), whereas Cr and Ni occurred primarily as residual mineral phases (>50%). Zn appeared uniformly distributed among the main geochemical forms. Considerable presence of Cr, Cu and Pb was found in the oxidizable fraction (∼50%), indicating organic matter and/or sulphides major sinks for these metals. Differences of heavy metal distribution among sediment samples were observed, depending on the total metal content and on sediment properties. Modifications in metal speciation induced by sediment air drying mainly consist of a transfer of the actual and potentially mobile fractions towards immobile fractions (mineral residue) by oxidation and formation of Fe and Mn oxides. Discussion  Both total content and sequential extraction results did not show an environmental critical situation: the only possible risk, associated with heavy element mobility, could occur in consequence of a drastic pH and redox equilibria variation at the water-sediment interface. Conclusions  Despite all limitations, the BCR-SEP combined with information on the chemical and mineralogical properties of the sediment solid matrix provides a valuable approach to describe the risks related to the potentially toxic HM occurring in sediments (in this paper the case of the Fusaro lagoon is examined). HM distribution among the sequentially extracted geochemical forms is affected by sediment properties, such as pH (Zn), clay (Cd), Fe easily reducible oxides (Pb) and organic matter (Cu) content. Recommendations  Political managers, usually facing limitations of time and resources, have to optimize the cognitive phases, selecting the most useful information to make ‘effective and correct decisions’ in the environmental field. Therefore, although conscious of the limits of the adopted quality assessment, we believe it represents a good compromise between time and resource availability (i.e. type and quality of information). Outlook  The complementary use of the simple and rapid European fractionation scheme with information on the chemical and mineralogical properties of the sediments provides more awareness about the nature of the sediment components involved and offers a more reliable way for studying HM speciation in sediments.     

Towards an Optimized Protocol for Measuring Global Dehydrogenase Activity in Storm-Water Sediments (10 pp)

Background, Aim and Scope   Microorganisms play an important role in the biogeochemical cycles of soils and sediments; hence the microbiological quality of these environments can be evaluated by measuring microorganism population densities, diversity and enzyme activity. For example, dehydrogenase activity is known to be sensitive to pollutants, such as heavy metals, and to correlate with the carbon cycle. This article presents an optimized protocol for measuring dehydrogenase in a range of different sediments and, more precisely, in urban storm-water sediments. The influence of blank preparation, ratio substrate/sediment and time of formazan extraction was studied on sediments coming from urban sewage works, or lakes and rivers. Materials and Methods   After a microbial and chemical characterization of the sediments studied, the initial protocol of dehydrogenanse measurement consited in incubating 2 g of dry sediment with 2 μmol of INT (the substrate) at 37°C for 24 hrs. It was carried out on three different urban storm-water sediments. Once an optimum dehydrogenase activity was obtained, the new protocol was tested on six other sediment materials. Results   The results for all the sterilized samples were significantly different to those obtained for the corresponding, non-sterilized sample, with the exception of the St Vallier sediment, which was treated with formaldehyde or the maximum dose of gamma radiation. Sediments that are rich in organic matter must be treated with high concentrations of INT in order to reach, or approach, substrate excess, especially if it is intended to compare formazan measurements. In order to more easily achieve excess substrate, we investigated the possibility of reducing the quantity of solid matter used for the tests. For the two samples tested, and especially for the road basin sample, tests carried out using a ratio of sediment mass (in g) to INT quantity (in μmol) of 0.05 (0.5 g of sediment/10 μmol INT) produced values of 2000-2200 μg of formazan/g of sediment/24 hrs. Activities are much lower (between 1.5 and 3 times lower) when the ratio is equal to 0.2. Sonication should increase formazan extraction as it separates aggregates, thereby improving the contact between the acetone and the sediment. Sonication has an effect on the extraction of formazan. For sample EC2, 30% more formazan was extracted with sonication than without. Discussion   Sterilization by formaldehyde and by autoclaving demonstrated very different levels of activity. Autoclaving is the least satisfactory sterilization method, as the modifications it causes, especially to the sediment texture, are too great (Trevors 1996). The main advantage of sterilization by irradiation is the minimal disturbance of the sediment structure (Trevors 1996, McNamara et al. 2003). The quickest and most economic sterilization method is the use of formaldehyde. Therefore, blanks sterilized using formaldehyde were used in the tests of the different methods. Organic matter absorbs INT salts, so they are no longer bioavailable for the microorganisms. Sediments that are rich in organic matter must be treated with high concentrations of INT in order to reach, or approach substrate excess, especially if it is intended to compare formazan measurements. Based on our results, the results reported in the literature and practical considerations, such as the solubility of INT and the toxicity of INT with respect to bacteria (Hatzinger et al. 2003), we decided to use a quantity of INT equivalent to 10 μmol (i.e. 2.5 mM in a final concentration in the test) for our subsequent experiments, even though we realized this would not produce saturation conditions for the highly organic sediments. In order to more easily achieve excess substrate, we investigated the possibility of reducing the quantity of solid matter used for the tests. The literature shows that previous work has often been carried out using 1 g samples of dry soil or dry sediment (Merlin et al. 1995, Taylor et al. 2002, Benitez et al. 2004, Plaza et al. 2004). Here, we find a direct relation between the amount of sample and the reduction of the substrate. To ensure that samples remained representative, it was decided not to test samples of less than 0.5g dry weight. Acetone was chosen as the extractant, as it has been used by many other workers (Brohon 1998, Engelen et al. 1998). Sonication has an effect on the extraction of formazan. Kruskal and Wallis tests, at p=0.05, show that the increase of INT extraction is significant for EC2 at 10 minutes, but not for EC1. EC2 is much coarser (around 75% sand and 25% silt) than EC1 (40% sand and 60% silt) (data not shown). This difference in grain size distribution may be one explanation for the different behavior of the two matrices when subjected to sonication .This pretreatment is known to destroy aggregates. Therefore, in order to measure the maximum activity, the acetone extraction time, with or without ultrasound, must be chosen to suit the matrices being studied. So, depending on the characteristics of the sediment (mostly the grain size distribution), it may be useful to use ultrasound in order to achieve a good level of formazan extraction. The method to be used must be determined for each sediments. Conclusions   When tested on different types of sediment (river, urban sewage, etc.) the optimized protocol (0.5 g sediment and 10 μmol of INT) gave higher activity measurements than the initial protocol and appears to provide a useful test method for comparative studies or for monitoring sediment quality. The organic matter content appeared to be one the most important parameter controlling the measurement and playing an important part on the different contact and extraction steps of the experiment. The best method for preparing blanks is sterilization using gamma radiation, as this has the lowest impact on sediment structure. However, if cost and time considerations render this method impracticable, samples can be sterilized using formaldehyde. Recommendations and Perspective  : The final protocol can be used to monitor the spatial (in terms of the different vertical and horizontal zones at the surface) and temporal (monitoring changes in activity over time using surface samples taken after different rain events) evolution of this activity within sediment samples from rainwater infiltration basins.     

Dynamics of arsenic-containing compounds sorption on sediments

Background  River and lake sediments constitute complex and difficult analytical samples. On the other hand, sediments play a fundamental role in the distribution of toxic compounds in aquatic systems and in the evaluation of the current state and the course of changes taking place in the environment. Among elements present in the environment in trace concentrations, but having well-elaborated toxic properties, one of most dangerous is arsenic. The element occurs in the environment in several chemical forms, predominant are inorganic forms of As(V) and As(III), and methylated forms such as monomethylarsonic acid (MMAA) and dimethylarsinic acid (DMAA). Objectives  Reported herein are experiments, which were undertaken with the aim of examining the dynamics of arsenic sorption in sediments and its dependence on speciation of the element and the pH in the environment. Simultaneously, influence of organic matter content and chemical composition of the sediments on As sorption, were investigated. Methods  Sediment samples (upper 10 cm layer) were collected from three sites located in the vicinity of Cracow:

Determination of Thallium and Other Elements (As,Cd, Cu,Mn, Pb,Se, Sb,and Zn) in Water and Sediment Samples from the Vicinity of the Zinc-Lead Smelter in Poland (3 pp)

Background, Goal and Scope   The aim of this study was to check the concentration of some elements in water samples collected near Pb-Zn mining and smelting works and comparison of the obtained data with results achieved for sediment samples originated from the same reservoirs. Objective   Here, 8 water samples and 3 bottom sediments collected from water reservoirs in the vicinity of 3 big Polish Pb-Zn smelters were analysed.Methods   Water analysis was performed after filtration through a 0.45 &#181;m filter and pH adjustment to 2. For decomposition of dried sediment samples, microwave assisted digestion with total dissolution of silicate matrix was applied. The elements studied were determined using ICP-MS and ICP-OES methods. Results and Discussion   The concentrations of most studied elements in water samples were on the 0.X &#181;g/L level, while only the contents of Tl, As, Mn, Cd, Pb and Sb in two water reservoirs were above the limits established for drinking water. The content of studied metals in sediments was in a wide range from X mg/kg (Se and Sb) to X000 mg/kg (Pb and Zn).Conclusions  and Recommendation. The study indicates that the impact of Tl, As, Cd, Cu, Mn, Pb, Zn, Se and Sb on bottom sediments is much more extensive than on the water in ponds located in the vicinity of a post-flotation waste heap. Monitoring of surface and underground waters, if limited only to the dissolved elements, can lead to faulty conclusions about environmental pollution. The bottom sediments mainly contain easily mobilised phases, and water-sediment equilibrium could be changed easily.     

Contamination history of suspended river sediments accumulated in oxbow lakes over the last 25 years

Background, aims, and scope  Embankment of meandering river systems in many industrial areas results in the formation of artificial oxbow lakes that may act as perennial or intermittent traps for river sediments. Their deposits can be dated using a combination of historical and stratigraphic data, providing a good means to study historical records of contamination transported by rivers. Contamination history over the last few decades is of special significance for Central and Eastern Europe as it can reflect high pollutant levels in the second half of the twentieth century and the subsequent improvement after the fall of the Iron Curtain. The purpose of this study was to investigate recent sediments of an oxbow lake of the Morava River, Czech Republic, their stratigraphic records, sediment architecture, and history of contamination. Materials and methods  Seven ground-penetrating radar (GPR) profiles and three sediment cores up to 4 m deep were studied. The stratigraphy of the cores was inferred from visible-light spectrophotometry, X-ray radiography, grain size analysis, and semiquantitative modal analysis of sandy fractions. The sediments were dated using the ¹³⁷Cs mass activity and combinations of stratigraphic and historical data. The cores were sampled for concentrations of heavy metals and persistent organic pollutants. Wet sampled, lyophilized, and sieved sediments were extracted and analyzed for heavy metals by inductively coupled plasma mass spectrometry (ICP-MS) of aqua regia leachate and for persistent organic pollutants by gas chromatography (GC-ECD and GC-MS). Results  Three distinct sedimentary sequences (S1, S2, and S3) were identified. The basal sequence S1 represents river channel sediments deposited before the formation of the oxbow lake, most likely before the 1930s. The boundary between the S1 and S2 sequence correlates with the level of sediment dredging from 1981 evidenced from historical data. The overlying sequences S2 and S3 represent a postdredging sediment wedge, which progrades into the lake. ¹³⁷Cs dating revealed a distinct Chernobyl 1986 peak at ∼150 cm depth inferring sedimentation rates up to 7.7 cm/year. Sediment contamination abruptly increased from the pre-1930s deposits to the post-1981 deposits. The concentration levels increased two to five times for Pb, As, Zn, and Cu, about 10 to 15 times for Cr, Sb, and Hg, up to 34 times for Cd, and 25 to 67 times for DDTs, PCBs, and PAHs. The concentrations of most contaminants remained approximately constant until the late 1980s when they started to decrease slowly. The decreasing trends were most prominent for heavy metals and anthracene, less prominent for DDTs, and almost absent for PCBs and most PAHs. Discussion  Different temporal and spatial patterns for various contaminants make it possible to distinguish between anthropogenic point sources from local industry (anthracene, Cr, Cd), possible diffuse sources (most PAHs), and geological background (V, Co, Ni, and Mo). The observed recent trends in heavy metal and persistent organic pollutant contamination are generally consistent with data from other Central European rivers. The roughly balanced contamination levels in sediments from the lake and the adjacent river channel suggest that the oxbow lake deposits reflect immediate levels of the contamination bound to suspended particulate matter passing through the river. Conclusions  The investigated oxbow lake accumulated suspended sediment from Morava River, developing a thick sedimentary body. The sediments offer a good time framework to study historical contamination of the river on a decade time scale. Continuous contamination trends can be traced back to the early 1980s. The results show that stratigraphic analysis of cores has a good potential for identification of uninterrupted historical trends and unconformities, e.g., due to dredging. Recommendations and perspectives  Oxbow lakes may provide an alternative to floodplains and reservoir deposits when studying river contamination history. High sedimentation rates of up to 7.7 cm/year offer a very good stratigraphic resolution, making it possible to study contamination patterns on annual or even seasonal time scales. On the other hand, oxbow lakes may represent long-term contamination stores, which are unlikely to be redistributed by river erosion and, hence, may possess significant environmental risks for the farther future.     

A new plant-based bioassay for aquatic sediments

Background, Goal and Scope  To date, standardised bioassays for the assessment of the ecotoxicological potential in sediments and dredged material use test organisms like bacteria, algae and crustaceae. This paper presents the development and application of a novel sediment contact test (whole sediment) withMyriophyllum aquaticum, a representative of rooted aquatic macrophytes. The aim of the present study is to demonstrate the value of a sediment contact test with rooted macrophytes as a supplement to existing test batteries in order to improve the assessment of sediment toxicity. Methods  The newly developed sediment contact test withMyriophylhim aquaticum was applied to natural whole sediments. For performing the test, whorls ofMyriophyllum aquaticum were directly planted in the native sediment and incubated in the light at 24°C (cf. section results and discussion). The end points of the test were the number of the shoots and the fresh weight of the whole plants. The duckweed growth inhibition test withLemna minor according to ISO/DIS 20079 was performed in pore waters from sediment samples. The results of the sediment contact test withMyriophyllum aquaticum were compared with each other and with those of the aquatic duckweed test. Results and Discussion  A test protocol for the new plant-based sediment contact test using the aquatic plantMyriophyllum aquaticum as an indicator was developed. The best control sediment proved to be the OECD sediment (OECD 207). A test period of 10 days appeared to be sufficient for the test. The increase of biomass and the derived growth rate were found to be the most suitable evaluation parameters. The growth behaviour ofMyriophyllum aquaticum differed depending on the origin of sediments. Therefore, plant-affecting contamination, that is bound in sediments, was indicated. Conclusions  The novel sediment contact test withMyriophyllum aquaticum can indicate phytotoxic effects in sediments. Therefore, it allows a better assessment of the overall-toxicity in whole sediments. Recommendations and Outlook  The sediment contact test withMyriophyllum aquaticum is a valuable tool for the evaluation of the ecotoxicological risk potential of waters and sediments. It should become a complement to a standardised test battery generally used for the assessment of sediment toxicity.     

Determining the bioavailability of contaminants and assessing the quality of sediments

Background, Aims and Scope  

Our study determined if and when an avoidance or attraction behavioural response would be displayed by Ilyanassa obsoleta when presented with a choice between harbour and reference sediments. Our goal was to develop a non-lethal approach that could be used in future assessments of the environmental quality of field sediments.     

Composition,distribution and sources of polycyclic aromatic hydrocarbons in sediments of the western harbour of alexandria,egypt

Aim and Background  Little data are available on the levels of polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Mediterranean Sea Coast of Egypt in general and the Alexandria coastal zone in particular. It was therefore deemed necessary to set up a monitoring programme to determine the current concentrations of PAHs in bottom sediments, and to identify any area where high concentrations of these potential hazardous contaminants were present in the Western Harbour of Alexandria. Methods  The composition, distribution and the source of PAHs in surficial sediments of the harbour were investigated. To document the spatial PAH input, surficial sediment samples from 23 locations throughout the harbour were analysed. as]Results and Discussion The total PAH load determined in the surficial sediment samples ranged from 8 to 131150 ng g¹ dry wt, generally with most of the samples having total concentrations of PAHs greater than 5000 ng g¹ dry weight. The highest concentration of total PAHs was recorded in sediments of the inner harbour. Ratio values of specific compounds such as phenanthrene to anthracene, fluoranthrene to pyrene, methyl-phen-anthrene to phenanthrene, methyl-dibenzothiophenes to dibenzothiophenes, alkylated to non-alkylated and high molecular weight to low molecular weight PAH, were calculated to evaluate the possible source of PAH contamination in the harbour sediments. Conclusions  Two main sources of PAH in the study area have been found: pyrolytic and petrogenic. Interferences of rather petrogenic and pyrolytic PAH contaminations were noticed for most samples. The dominant sources of PAH appear to be the combustion processes through run-off, industrial and sewage discharges, and atmospheric input. The concentrations of PAHs were generally above levels expected to cause adverse biological effects. Recommendations and outlook  Information from this study and any other relevant studies should be useful in designing future strategies for environmental protection and management of the harbour.     

A New Microbial Contact Assay for Marine Sediments (7 pp)

-  Dedicated to Prof. Dr. Ulrich Förstner on his 65th birthdayBackground, Aims and Scope   The number of microbiological contact tests for marine sediments is low, although microorganisms enable a rapid screening and monitoring of sediment quality and a high resolution of hazard assessment. As no single biotest can provide reliable answers concerning the potential hazard of environmental samples, a combination of bioassays needs to be applied to serve this purpose. In order to cover as many potential effects as possible, test organisms should have different sensitivities; assays should cover different exposure pathways, and measure the effect on various physiological functions. Methods   3 different Vibrio species (V. proteolyticus, V. natriegens, V. gazogenes) were tested for their suitability as test organisms in a contact assay on the basis of their activity, sensitivity and their spectrum of salinity tolerance. As a test endpoint, dehydrogenase activity over an incubation time of 2 hours (~ 3 generations) was chosen, quantified by resazurine reduction. The test was miniaturized to 96 well plates, including a dilution series, and quality criteria were established. The assay was then tested on natural sediments from a contaminated site in the Lübeck Bight.Results and Discussion   Vibrio proteolyticus proved to be the best suited test organism out of those tested for this bioassay. The miniaturized test system revealed a coefficient of variation of positive controls in 16 tests of 17.8 %. Its application to contaminated sediments from the Lübeck Bight showed a good differentiation of samples from different depths and zones, which reflected the general contamination pattern and capping activities in that area. Conclusion   The miniaturized test system that has been developed for V. proteolyticus is suited to assess toxic effects of brackish and marine sediments. Due to an increased number of replicates and an extensive sediment dilution series, the degree of certainty of hazard assessment is elevated.Recommendations and Outlook   The integration of this sediment contact assay as a complementary test in a microbiological test battery is recommended.     

Application of a new sediment contact test with <Emphasis Type="Italic">Myriophyllum aquaticum</Emphasis> and of the aquatic <Emphasis Type="Italic">Lemna</Emphasis> test to assess the sediment quality of Lake Skadar

Goal, Scope and Background  Situated in the transboundary belt between Montenegro and Albania, Lake Skadar is the largest freshwater reservoir in Southeastern Europe. Because of the wide range of endemic, rare or endangered plant and animal species it supports, Lake Skadar and its extensive adjacent wetlands are internationally recognised as a site of significance and importance (Ramsar site). Within the last 10 to 20 years, Lake Skadar was exposed to intensive pollution. For the assessment of the ecotoxic load of the sediments sampled in Lake Skadar, a triad approach was recently applied. Overall, a complex spectrum of ecotoxic loads was elucidated. The aim of the present study was to use plant-based bioassays for assessing the sediment quality of Lake Skadar in order to facilitate and complement the triad test battery. The newly developed sediment contact test with Myriophyllum aquaticum and the aquatic growth inhibition test with Lemna minor were applied to native sediments and pore water, respectively, allowing the investigation of different toxicity-effects caused by particle-bound pollutants as well as pollutants in the interstitial water. This investigation is the first application of the novel sediment contact test with Myriophyllum aquaticum to lake sediments. Methods  Sediment samples were taken from nine selected sites at Lake Skadar and investigated by the sediment contact assay with Myriophyllum aquaticum. The pore water was extracted from these sediment samples to be analysed in the aquatic growth inhibition test with Lemna minor. The results of the sediment contact tests were compared with each other and with those of the aquatic growth inhibition test. Results and Discussion  Both applied macrophyte biotests revealed distinct changes in the growth behaviour of the two macrophytes subsequent to the exposure to the investigated natural sediments of Lake Skadar. The Myriophyllum sediment contact test revealed significant toxicity in the sediment samples from Radus and Kamenik, whereas the aquatic Lemna test showed inhibition effects for the samples from Sterbeq, Plavnica and Kamice. Data obtained with the newly developed Danio rerio contact test and the Arthrobacter globiformis contact test confirmed the Myriophyllum results. Analyses of the heavy metal content in the sediments revealed low or moderate contamination levels. Correlation analyses between the content of heavy metals in the sediments and growth inhibition of Myriophyllum aquaticum showed a significant correlation between Cr concentrations and growth inhibition. Comparable findings are available for a German river system. In contrast, no significant correlation between inhibition rates and concentration of metals could be observed with Lemna minor. Conclusions  It was shown that the newly developed sediment contact test with Myriophyllum aquaticum is applicable to lake sediments. In both the sediment contact test with Myriophyllum aquaticum on whole sediments and the aquatic growth inhibition test with Lemna minor on pore water, plant growth was influenced by the natural sediments and its components. Therefore, both test systems were found to be suitable for the detection of phytotoxic effects upon exposure to sediments. Myriophyllum aquaticum as test organism of the contact test grows directly in the sediment without an additional water-layer. Thus, it is able to detect toxicity caused by particle-bound phytotoxic substances as well as pore water-related contamination, while the floating Lemna minor can only detect effects emanating from pore water. Significant differences of the results were observed between these two test systems and, accordingly, the two different exposure scenarios. Hence, none of the tests can replace the other one and, as a consequence, both should be included into a test battery for the assessment of sediment toxicity. Recommendations and Perspectives  Both plant assays were shown to be reliable tools for the evaluation of the eco-toxicological risk potentials of pore water and solid-phase sediment. They should become a complement to the standardised test battery generally used for comprehensive hazard assessment. ESS-Submission Editor: Dr. Ulrike Kammann (ulrike.kammann@ifo.bfa-fisch.de)     

Anaerobic sediment potential acidification and metal release risk assessment by chemical characterization and batch resuspension experiments

Background, Aim and Scope  Sediments act as a sink for toxic substances (heavy metals, organic pollutants) and, consequently, dredged materials often contain pollutants which are above safe limits. In polluted anaerobic sediments, the presence of sulphides and redox potential changes creates a favorable condition for sulphide oxidation to sulphate, resulting in potential toxic metal release. The oxidation reaction is catalyzed by several microorganisms. Some clean up measures, such as dredging, can initiate the process. The aim of the present work is to assess the acidification and metal release risk in the event of sediment dredging and also to compare two different acid base account techniques with the resuspension results. The oxidation mechanism by means of inoculation with an Acidithiobacillus ferrooxidans strain was also evaluated. Methodology  The sediments were chemically characterized (pH; organic oxidizable carbon; acid volatile sulphides; total sulphur; moisture; Cr, Cu and Zn aqua regia contents). A metal sequential extraction procedure (Community Bureau of Reference, BCR technique) was applied to calculate the Acid Producing Potential (APP) and Acid Consuming Capacity (ACC) of the sediment samples through Fe, Ca²⁺ and SO₄ ²⁻ measurements. The acid base account was also performed by the Sobek methodology (Acid producing potential — AP — calculated with total sulphur and neutralization potential — NP — by titration of the remaining acid after a reaction period with the sample). Fresh sediments were placed in agitated shake flasks and samples were taken at different times to evaluate pH, SO₄ ²⁻ and Cr, Cu, Zn and Fe²⁺ concentration. Some of the systems were inoculated with an Acidithiobacillus ferrooxidans strain to assess the biological catalysis on sulphide oxidation. Results  Sediment chemical characterization showed high organic matter content (5.4–10.6%), total sulphur (0.36–0.86%) and equivalent CaCO₃ percentages (4.5–8%). pH was neutral-alkaline for all of the samples. AVS content was high except for sample 5. The acid base account obtained with the two methods gave different results for the acid generating risk of the samples. A decrease of 0.4 to 3.1 pH units was measured in the agitated shake flasks. In all of the systems, sulphate concentration increased (2,100–2,200 mg L⁻¹ to 2,500–3,000 mg L⁻¹), and positively correlated with the initial total sulphur content of the samples in the inoculated flasks. Cu and Cr in solution were not detected in most of the sampling occasions (<0.5 mg Cu L⁻¹ and <0.5 mg Cr L⁻¹). Zn reached high concentrations (up to 11.8 mg L⁻¹). For every system — except sediment 1 — the lowest pH registered was similar in comparison to inoculated and control systems. The inoculation effect was mostly evidenced in the systems by a higher sulphate release rate compared to the control systems. Discussion  The BCR method categorized all of the samples as potentially acid generating material. The Sobek method using NPR (NP/AP) criteria classified sample 3 as a possible acid generator and samples 1, 2 and 5 with a low acid generation potential. Despite this, all the samples acidified the media in the kinetic tests in at least one of the conditions employed in this work. It would seem that NPR and NNP (NP-AP) risk classification criteria should not be directly used with anaerobic sediments. Appropriate classification levels for sediments should be developed considering the different sulphide reactivity between rock and sediments. Sediment oxidation can cause acidification, which is partially explained by sulphide oxidation. In the samples studied, we found a positive correlation between sulphate increase in solution after oxidation and total sulphur content in the inoculated systems. Significant amounts of Zn could be released to solution while Cr and Cu remained insoluble despite the pH decrease observed. The low Cu and Cr mobility could be explained by the very low solubility of their hydroxides and high affinity for organic matter and iron oxides/hydroxides that might form during sediment oxidation. Dredged sediment management and disposal should be carefully planned. Conclusions  All of the sediment samples lowered the pH media in the laboratory batch resuspension experiments. However, both risk classification criteria (NNP, NPR) from Sobek acid base account were not able to predict the samples’ behavior as accurately as the BCR derived base account. The inoculation effect was mostly associated with a higher sulphate release and not to a lower pH due to acid base equilibrium. Recommendations and Perspectives  Appropriate risk classification levels for sediments should be developed considering the different sulphide reactivity between rock and sediments. ESS-Submission Editor: Dr. Sabine Ulrike Gerbersdorf (sug@st-andrews.ac.uk)     

Nitrogen and Phosphorus in Coastal Sediments Covered by Cyanobacteria Mats (9 pp)

Background   Biocommunities of phototrophic microorganisms (principally cyanobacteria) developing on the surface sediments of shallow, warm and semi-isolated coastal environments, bind or trap small particles on their polysaccharide sheaths creating organosedimentary structures. Those structures are called algal mats and they are commonly flat and laminar in shape. They are also called recent stromatolites due to their remarkable similarity to the fossil ones. Objectives   Not many geochemical studies exist concerning cyanobacterial mats in Mediterranean coasts, in comparison with the biological ones. Considering the importance of nitrogen and phosphorus in the cyanobacteria mat development, the present study aims to contribute to the knowledge of their chemical behaviour in such environments. Methods   Sediment cores of about 10 cm length along with water samples were collected during the course of a year from two Greek coastal areas. Sediments were fractionated in three distinct layers according to their structure. A wet oxidation method for the simultaneous determination of total nitrogen and total phosphorus was applied to all sediment samples. The total organic carbon (TOC), the total inorganic phosphorus and the natural pigment content in the sediment samples were also determined. Standard spectrophotometric methods were used for the determination of the concentration of dissolved nutrients. In situ measurements of pH, temperature and salinity were also carried out. Results and Discussion   The sampling areas were found to be in the mesotrophic level. The group of aerobic filamentous cyanobacteria dominated the sediment biocommunities. The pH of the sediment showed a gradual reduction downwards. The highest content of TOC, total nitrogen and total phosphorus were detected in the surface layer of the sediment samples. The contribution of organic phosphorus to the total phosphorous ranged between 0% and 50% with an average value of 26.6%. A depletion of organic phosphorus in the anoxic middle layer of the sediment was detected. A good positive correlation between total nitrogen and chlorophyll-a, as well as total nitrogen and TOC in the surface sediment layer, was observed. A good negative correlation between total phosphorous in sediments and dissolved phosphates in seawater was also observed. Conclusions   The high content of total nitrogen recorded in the surface sediments indicate that cyanobacteria accumulate nitrogen acquiring it from the sediment, the marine environment and the air (in the form of N2). A proportional accumulation in phosphorus also happens, although to a lesser degree. The temporal fluctuation of nitrogen content in the sediment's surface layer agrees with the temporal fluctuation of primary production. The cyanobacterial mat acts as a natural pump that transfers phosphorus from seawater to the surface of the sediment. Recommendations and Outlook   A further, more extensive, multidisciplinary study of cyanobacterial mats is needed for the determination of the biogeochemical processes that take place there and for the effective environmental management of the areas where these forms develop.     

Source apportionment of lake bed sediments to watersheds in an Upper Mississippi basin using a chemical mass balance method

Sediment samples were collected from three known sources contributing to a depositional basin of the Upper Mississippi River, USA. The heavy silt fraction (2–63 μm, density >2.95) isolated from the sediments was analyzed for 42 elements by inductively coupled plasma-mass spectrophotometry (ICP-MS) to give signature profiles characteristic of each source catchment. Known proportions of heavy silt fractions from each source were mixed and the composite samples analyzed in the same way. The proportions of components in the composite samples were compared to their apportionments calculated statistically using the US Environmental Protection Agency (USEPA) chemical mass balance (CMB) air quality receptor model. This showed that the CMB technique can apportion sediments to their catchment sources reliably. The technique was then applied to dated sediments of Lake Pepin, in the Upper Mississippi basin, to apportion them to their contributing catchments. The results show that almost all the recent sediments deposited in the basin originated in the Minnesota River catchment, and that the sediment load increased over time as anthropogenic impacts increased. This technique could be used elsewhere to determine sediment provenance and identify changes in sediment sources over time.