Evaluation of the toxicity of marine sediments and dredge spoils with the Microtox bioassay

The Microtox^R bioassay was used to evaluate the toxicity of sediment and dredge spoil elutriates from several potentially-contaminated sites in Mobile and Pascagoula Bays. Elutriates were prepared using either local seawater or distilled deionized water (osmotically adjusted with NaCl prior to testing), and Microtox^R assays were performed with the elutriates and three reference toxicants. There were marked differences in the toxicity of several elutriates and reference toxicants in the two different waters, with the seawater generally resulting in the same or lesser toxicity than the osmotically-adjusted distilled deionized water.     

Toxicity and heavy metal contamination of surficial sediments from the Bay of Thessaloniki (Northwestern Aegean Sea) Greece

Surficial sediments (the fraction < 2000 microm) from the Bay of Thessaloniki, in the Northwestern Aegean Sea, Greece were examined for heavy metal and organic carbon contents, as well as for acute LUMIStox toxicity of pore waters (PWs), wet sediment elutriates (WSEs) and dry sediment elutriates (DSEs) obtained from the solid material remaining after PW extraction. WSEs where not toxic. EC20/50 values could be measured in some DSE and PW samples. In all sediment samples, the DSE toxicity was greater than the corresponding PW toxicity. Sediment concentrations of total and labile Cd, Pb, Cu, Cr, Zn, Mn, Ni and Fe were determined and evaluated in relation to sediment quality guidelines. Pollution levels ranged from low to high for certain metals. A misfit between sediment toxicities calculated from heavy metal concentrations and those biologically measured was observed. Toxicity values were in general poorly correlated with sediment's heavy metal or organic carbon content. As significant correlation was however found between the DSE toxicity with total Ni and labile Fe, as well as for the PW toxicity with total Ni, labile Fe and labile Cr.     

Urease inhibition: a tool for toxicity identification in sediment elutriates

A method for the detection and confirmation of heavy metal toxicants in sediment elutriates based on a urease inhibition assay, ICP-AES analysis and EDTA chelation in the frame of toxicity identification evaluation (TIE) is presented. Zinc was identified as the major toxicant in pHstat elutriates of sediments of the river Saale (Germany). Implications of natural and anthropogenic chelating agents, which are frequently present in environmental samples, on toxicity confirmation of heavy metals based on the toxic unit approach are discussed.     

The toxicity of composted sediments from Mediterranean ports evaluated by several bioassays

This work investigates the ecotoxicological evaluation of contaminated dredged sediments from French Mediterranean navy harbour (A), commercial port (B) and two composite specimens (C) and (D) coming from the mixture of A and B with other port sediments. The toxicity of elutriates from these sediments is estimated using embryo-toxicity test, Microtox® solid phase test, LuminoTox, phytotoxicity tests and genotoxicity test. Bioassay responses are not clearly correlated with chemical contamination in the whole sediment and vary as a function of tested organisms. The highest contaminated samples (A and C) are almost always more toxic than the less contaminated samples (B and D). Among composite sediments, the mixture effect with other sediments is not efficient to decrease toxicity in sample C, suggesting that other parameters influence toxicity level such as particle size or organic matter content. These parameters should be taken into consideration in order to improve the efficiency of the mixture process and produce composite sediments with low toxicity.     

The toxicity and concentrations of PAHs in creosote-contaminated lake sediment

Sediment samples, divided into three layers (0-10, 10-20 and 20-30 cm), were collected from 16 sites in Lake J?ms?nvesi, Central Finland. The acute toxicity of pore waters and elutriates (sediment + water 1:4 v/v) were studied by bioluminescence inhibition test and by immobilisation of water fleas (Daphnia magna Straus). Concentrations of polycyclic aromatic hydrocarbons (PAHs) in sediments and elutriates were measured by gas chromatography using flame ionization detection (GC/FID). The highest total PAH concentration was 3.3 mg/g dry weight in the sediment and up to 1.7 mg/l in the elutriate of the uppermost (0-10 cm) layer, also being the most toxic to photoluminencent bacteria and water flea. When sediment and water mix, like during dredging operations, toxic compounds may spread from the sediment to the water column and can pose on environmental risk.     

Effects of storage method and duration on the toxicity of marine sediments to embryos of Crassostrea gigas oysters

The objective of laboratory sediment bioassays is to estimate in situ toxicity. This goal is difficult to achieve, as one of the main limitations of sediment toxicity tests is disruption of sediment geochemistry during sampling, handling and preservation. The effects of storage on the estimation of marine sediment toxicity to Crassostrea gigas embryos and larvae were investigated. Three storage methods and four storage periods were compared with three different sediment types contaminated by heavy metals, polycyclic aromatic hydrocarbons (PAHs) and both contaminants. Freezing and freeze-drying considerably increased the toxicity of decanted sediments and their elutriates as compared to the toxicity obtained with fresh sediments. Concerning the elutriates, the toxicity found with frozen and freeze-dried sediments was correlated with DOC, ammonia and PAH contents. However, the toxicity of fresh sediments kept at 4 degrees C increased with increasing duration of storage and was also correlated with the amount of ammonia in the elutriates.     

Arsenic in marine sediments from French Mediterranean ports: Geochemical partitioning,bioavailability and ecotoxicology

This work investigates arsenic mobility, bioavailability and toxicity in marine port sediments using chemical sequential extraction and laboratory toxicity tests. Sediment samples were collected from two different Mediterranean ports, one highly polluted with arsenic and other inorganic and organic pollutants (Estaque port (EST)), and the other one, less polluted, with a low arsenic content (Saint Mandrier port (SM)). Arsenic distribution in the solid phase was studied using a sequential extraction procedure specifically developed for appraising arsenic mobility in sediments. Toxicity assessment was performed on sediment elutriates, solid phases and aqueous arsenic species as single substance using the embryo-toxicity test on oyster larvae (Crassostrea gigas) and the Microtox test with Vibrio fischeri. Toxicity results showed that all sediment samples presented acute and sub-chronic toxic effects on oyster larvae and bacteria, respectively. The Microtox solid phase test allow to discriminate As-contaminated samples from the less contaminated ones, suggesting that toxicity of whole sediment samples is related to arsenic content. Toxicity of dissolved arsenic species as single substance showed that Vibrio fischeri and oyster larvae are most sensitive to As(V) than As(III). The distribution coefficient (Kd) of arsenic in sediment samples was estimated using results obtained in chemical sequential extractions. The Kd value is greater in SM (450 L kg^?1) than in EST (55 L kg^?1), indicating that arsenic availability is higher for the most toxic sediment sample (Estaque port). This study demonstrates that arsenic speciation play an important role on arsenic mobility and its bioavailability in marine port sediments.     

Toxicity testing with luminescent bacteria – Characterization of an automated method for the combined assessment of acute and chronic effects

The luminescent bacteria test according to EN ISO 11348 is frequently applied in (eco) toxicity testing and is applicable for a huge variety of environmental and industrial samples. A big disadvantage of this method is the very short exposure time, which is expressed in a low sensitivity in regard to substances with a delayed effect. Chronic effects, i.e. interference with cell growth, cannot be assessed with this conventional standard method. The goal of this research was to develop an automated testing system for long term toxicity towards the luminescent bacteria Vibrio fischeri by implementing microtitration-based instrumentation. The optimized method, hereinafter referred to as “kinetic luminescent bacteria test”, can be described as a miniaturized combination of the conventional short-term luminescence inhibition test according to EN ISO 11348 and the Photobacterium phosphoreum growth inhibition test (DIN 38412-37). The validation procedure included the evaluation of six reference compounds (3,4-Dichloroaniline, 3,5-Dichlorophenol, Chloramphenicol, Streptomycin sulfate, Potassium dichromate, Zinc sulfate heptahydrate) and three different endpoints that are acute luminescence inhibition (acute LI) after 30 min, chronic luminescence inhibition (chronic LI) after 24 h and growth inhibition (GI) after 14 h. The optimized method allows the assessment of acute and chronic effects within one test, by what a misinterpretation of the toxicity of substances with delayed bacterial toxicity can be prevented, without abandoning most of the advantages of the conventional short-term test. Therefore, the kinetic luminescent bacteria test is exceptional as an initial screening test for environmental samples or substances with unknown (eco) toxicological characteristics.     

Applicability of the bioluminescence inhibition test in the 96-well microplate format for PAH-solutions and elutriates of PAH-contaminated soils

The use of conventional plastic microplates for a miniaturised luminescent bacteria test may result in an underestimation of the toxicity for poorly water soluble highly adsorbing toxicants such as PAHs. In this study, the suitability of microplates for testing elutriates of PAH-contaminated soils was investigated. The LUMIStox test was performed as the standard test in the miniaturised format using contaminated soil elutriates and aqueous solutions of four selected PAHs (viz. naphthalene (NAP), acenaphthene (ACE), fluorene (FLU), and phenanthrene (PHE)). For the aqueous PAH-solutions, we observed reduced light inhibition values for the miniaturised bioassay when using black microplates made of polypropylene (PP) and polystyrene (PS) compared to the standard LUMIStox test. This phenomenon was most likely due to adsorption of toxicants to the microplate surfaces with PAHs of lower water solubility being significantly more affected; however, after minimizing the exposure of samples to plastic surfaces, polystyrene microplates revealed equivalent performance (>80% 'relative' light inhibition) to the standard glass cuvette test system. For soil elutriates, black microplates again exhibited slightly lower light inhibition values while white plates made of PS and Barex resulted in a pronounced overestimation of toxicity for a coloured soil elutriate. In general, microplates were applicable for testing elutriates of PAH-contaminated soils. In cases where samples are coloured or turbid, the application of black microplates is recommended.     

Evaluation of the toxicity of two soils from Jales Mine (Portugal) using aquatic bioassays

Soil contamination can be one path for streams and groundwater contamination. As a complement of chemical analysis and total contaminants determination, bioassays can provide information on the bioavailable fraction of chemical compounds, focusing on the retention and habitat function of soils. In this study the evaluation of the toxicity of two soils from the abandoned Jales Mine (Portugal) regarded both functions. The buffer capacity of soils was tested with bioassays carried out using the cladoceran Daphnia magna and the marine bacteria Vibrio fischeri. The habitat function of soils was evaluated with the reproduction bioassay with the collembolan Folsomia candida. The Microtox solid-phase test was performed with V. fischeri using soil as test medium, and soil elutriates were extracted to perform the Microtox basic test, and an immobilization and reproduction bioassay with D. magna. The marine bacteria showed high sensitivity to the soil with low heavy metal content (JNC soil) and to JNC soil elutriates, while the soil with highest heavy metal content (JC soil) or soil elutriates exposure did not cause any toxic effect. In the bioassays with D. magna, organisms showed sensitivity to JNC and also to JC soil elutriates. Both mobilization and reproduction features were inhibited. The bioassay with F. candida did not reflect any influence of the contaminants on their reproduction. Although JNC soil presented lower heavy metal contents, elutriates showed different patterns of contamination when compared to JC soil and elutriates, which indicates different retention and buffer capacities between soils. Results obtained in this study underlined the sensitivity and importance of soil elutriate bioassays with aquatic organisms in the evaluation strategy in soil ERA processes.     

Potential impacts of water injection dredging on water quality and ecotoxicity in Limehouse Basin, River Thames, SE England, UK

The use of water injection dredging (WID) is increasing in the UK's inland waterways and marinas. Jets of water are injected under low pressure directly into bottom sediment creating a turbulent water-sediment mixture that flows under the influence of gravity. Many of these sediments are highly contaminated and little is known of the effects of contaminant release on water quality or the risk to biota living in both the sediment and the water column. Sediment cores were collected from Limehouse Basin, a proposed WID site in SE England and current sediment toxicity was assessed using a number of techniques. Comparison of metal data to US sediment quality guidelines indicated intermediate levels of toxicity while, calculation of acid volatile sulphide to simultaneously extracted metal ratios underestimated the potential toxicity to sediment dwelling organisms. In contrast, porewater ammonia concentrations were in excess of all published ecotoxicological guidelines and indicate serious risk to biota. Re-suspension experiments were used to mimic the effects of WID on overlying water quality and ecotoxicity tests were carried out on elutriates using Daphnia magna to examine the impacts on biota. Concentrations of a range of metals in the elutriates predict that adverse biological effects would be observed during WID, however only 10% of the elutriate samples caused an adverse effect on Daphnia. Limehouse Basin is a complex aquatic environment receiving predominantly fresh waters while the sediments have high porewater chloride concentrations reminiscent of previous tidal inputs to the basin, making the choice of test organism problematic.     

Effects of anthracene, pyrene and benzo[a]pyrene spiking and sewage sludge compost amendment on soil ecotoxicity during a bioremediation process

The fate of spiked anthracene, pyrene and benzo[a]pyrene in soil with or without sewage sludge compost was assessed during a 6-month bioremediation process simulating landfarming. Bioassays and physico-chemical analyses were employed to monitor toxicity change in soil samples and elutriates through ten sampling campaigns. Pearson product-moment correlation coefficient was determined to measure the strength of relationship between bioassays and physico-chemical analyses. The PAH dissipation in soil was enhanced after the first water addition, and the remaining amounts at the end of the experiment were positively correlated to the number of benzene rings and the presence of sewage sludge compost. Toxicity of soil elutriates to Daphnia magna was evident at early stages, originating exclusively from sewage sludge compost amendment. The lettuce root elongation was continuously inhibited by elutriates for all the treatments including control soil, probably due to high salinity or to unaddressed leachable phytotoxic compounds that were present in the experimental soil. The newly developed direct solid-phase chronic toxicity test using ostracod (Heterocypris incongruens) succeeded in evaluating the soil-bound PAH toxicity, as PAHs could not be detected in elutriates.     

Toxicity characterisation of sediment porewaters collected from UK estuaries using a Tisbe battagliai bioassay

The lethal toxicity of sediment porewater isolated from samples collected from six United Kingdom estuaries was tested using a Tisbe battagliai bioassay. A selection of Phase 1 toxicity identification evaluation (TIE) procedures was then used to characterise the substances responsible for the measured toxicity. In samples collected in 2000, cationic metals, ammonia, organic compounds were identified as the cause of toxicity in the most toxic sample collected. Some of the toxicity remained uncharacterised. It was shown that the toxicity in samples collected from the same locations in 2001 was due to ammonia. The successful application of the T. battagliai bioassay demonstrates that it is a suitable assay for marine sediment porewater TIE and that combined with simple characterisation procedures allow an initial assessment to be made on the type of substances responsible for the measured toxicity.     

Toxicity assessment through multiple endpoint bioassays in soils posing environmental risk according to regulatory screening values

Toxicity profiles of two soils (a brownfield in Legazpi and an abandoned iron mine in Zugaztieta; Basque Country) contaminated with several metals (As, Zn, Pb and Cu in Legazpi; Zn, Pb, Cd and Cu in Zugaztieta) and petroleum hydrocarbons (in Legazpi) were determined using a multi-endpoint bioassay approach. Investigated soils exceeded screening values (SVs) of regulatory policies in force (Basque Country; Europe). Acute and chronic toxicity bioassays were conducted with a selected set of test species (Vibrio fischeri, Dictyostelium discoideum, Lactuca sativa, Raphanus sativus and Eisenia fetida) in combination with chemical analysis of soils and elutriates, as well as with bioaccumulation studies in earthworms. The sensitivity of the test species and the toxicity endpoints varied depending on the soil. It was concluded that whilst Zugaztieta soil showed very little or no toxicity, Legazpi soil was toxic according to almost all the toxicity tests (solid phase Microtox®, D. discoideum inhibition of fruiting body formation and developmental cycle solid phase assays, lettuce seed germination and root elongation test, earthworm acute toxicity and reproduction tests, D. discoideum cell viability and replication elutriate assays). Thus, albeit both soils had similar SVs, their ecotoxicological risk, and therefore the need for intervening, was different for each soil as unveiled after toxicity profiling based on multiple endpoint bioassays. Such a toxicity profiling approach is suitable to be applied for scenario-targeted soil risk assessment in those cases where applicable national/regional soil legislation based on SVs demands further toxicity assessment.     

Inventory of marine biotest methods for the evaluation of dredged material and sediments

An inventory of marine biotest methods for the evaluation of dredged material and sediments was compiled on behalf of the Federal Environmental Agency of Germany. Relevant assays were identified from the literature and experts from several countries contributed to a questionnaire survey on established and developing procedures. The biotest methods are applicable to whole sediment, sediment suspension, sediment elutriate, porewater and/or sediment extract. The endpoints cover acute and long-term toxicity, bioaccumulation, endocrine effects, toxic effects on reproduction, carcinogenicity and mutagenicity. Comparative analyses and evaluation of the biotest methods were conducted with regard to their sensitivity, specificity, applicability (regional specificity, availability and suitability of the test organisms), variability (physicochemical factors, natural factors and factors related to sampling and testing), cost-effectiveness, aspects of animal ethics, standardization (guidelines, intercalibration) and application for monitoring purposes in the areas of the OSPAR and Helsinki Conventions. The available information was integrated to rate the validity of the methods, their relevance for assessing impacts on ecosystems and the suitability of the methods for the evaluation of marine sediments and dredged material. Based on the rating of the individual bioassays, a tiered testing is suggested in a hierarchical approach representing a variety in taxa, biological processes and exposure routes, thereby covering the cellular, species, population and community level with a wide discriminatory and sensitivity range. The toxicological significance and complexity increases with the tiers: (1) screening and detection of impacts, (2) characterization of toxic effects, (3) verification of in situ alterations.     

大型蚤标志酶用于城市二级出水毒性的评价

大型蚤是一种国际公认的标准实验生物,广泛应用于污水、地表水等水质毒性检测。毒性水平较低的城市二级出水,对大型蚤往往无急性毒性效应,而具有慢性毒性效应,但慢性毒性检测周期过长,因此探索一种更灵敏的指标,实现快速检测,对于控制二级出水的水质风险具有重要意义。本研究考察了大型蚤在短期暴露于城市二级出水条件下,其体内乙酰胆碱酯酶、超氧化物歧化酶、过氧化氢酶、ATP酶、羧酸酯酶和碱性磷酸酯酶的酶活变化特征,从中筛选出对二级出水毒性响应灵敏的标志酶指标。实验结果表明,碱性磷酸酯酶、过氧化氢酶对二级出水毒性响应相对较灵敏,具有成为标志酶的潜力,研究结果为城市二级出水生物毒性评价方法优化提供新的思路。     

Chemical and ecotoxicological analyses of sediments and elutriates of contaminated rivers due to e-waste recycling activities using a diverse battery of bioassays

A multi-trophic, multi-exposure phase assessment approach was applied to characterize the toxicity of sediments collected from two rivers in Guiyu, China, an e-waste recycling centre. Elutriate toxicity tests (bacterium Vibrio fischeri and microalga Selenastrum capricornutum) and whole sediment toxicity test (crustacean Heterocypris incongruens) showed that most sediments exhibited acute toxicity, due to elevated heavy metals and PAHs levels, and low pH caused by uncontrolled acid discharge. The survival rates of crustaceans were negatively (p < 0.05) correlated with total PAHs in sediments (411-1755 mg kg⁻¹); EC50s of V. fischeri on the elutriates were significantly correlated with elutriate pH (p < 0.01). Significant (p < 0.05) correlations between the induction of hepatic metallothionein in tilapia (Oreochromis mossambicus) and metal concentrations (Cu, Zn, Pb) in sediments were also observed, when fish were fed with diets containing sediment. The results showed that uncontrolled e-waste recycling activities may bring adverse effects to local aquatic ecosystem.     

Spore release by the green alga Ulva: a quantitative assay to evaluate aquatic toxicants

A toxicity test using spore release of the aquatic green alga, Ulva, was developed and evaluated by assessing the toxicity of different organic and inorganic chemicals and elutriates of sewage or waste sludge. The toxic ranking of four metals was: Cu (EC50 of 0.040mgL(-1))>Cd (0.095mgL(-1))>Pb (0.489mgL(-1))>Zn (0.572mgL(-1)). The EC50 for TBTO ranged from 24 to 63microgL(-1). The most toxic VOC was formalin (EC50 of 0.788microlL(-1)) and the least toxic was acetone. Spore release was significantly inhibited in all elutriates; the greatest and least toxic effects were for industrial sewage (3.29%) and filtration bed (10.08%), respectively. The bioassay is simple, inexpensive and sensitive. The cosmopolitan distribution of Ulva means that the test would have a potential application worldwide.     

Effect of sediment turbidity and color on light output measurement for Microtox Basic Solid-Phase Test

In this work, sediment samples collected from several Spanish harbours were tested with two toxicity procedures, designed for solid samples: the Microtox Basic Solid-Phase Test (BSPT) and a modified procedure of the previous test protocol (mBSPT). According to the BSPT procedure, after initial light readings, pure bacteria were exposed to sediment suspension dilutions and light production was directly measured on suspended sediments without any further manipulation. As measurements are likely to be affected by sediment turbidity and color, a variation in initial light measurement has been here suggested, in order to consider the sample effect at all time readings during the test. Firstly, when sediment suspensions at different concentrations were added to bacteria suspension, immediately the initial light output drastically decayed by more than 50% in signal difference, resulting in a false inhibition, as effect of sample turbidity/color. This effect was more evident at high EC50 values, when slightly or not toxic samples were assessed. Secondly, the comparison of the EC50 obtained with both procedures, demonstrated that the mBSPT produced higher EC50 values (less toxic) than those obtained with the standard procedure. The mBSPT procedure resulted rapid and effective and it could be applied simultaneously with BSPT, in order to better evaluate the toxicity.     

Evaluation of time-to-effects as a basis for quantifying the toxicity of contaminated sediments

Due to uncertainties as to appropriate procedures and dilution materials, most sediment tests are conducted only with undiluted, whole samples. Hence, it is not possible to use conventional concentration-response approaches to quantify toxicity of samples that elicit a 100% effect (e.g., mortality) at a preset test interval (typically 10 d). An alternative approach to quantifying the relative toxicity of test sediments is to determine time-to-effects. The objective of this study was to assess the utility of a time-to-effects approach for quantifying toxicity of freshwater sediments to the invertebrates Hyalella azteca and Chironomus tentans. Survival of both species and growth of C. tentans was determined using five sediments (four test samples and a control sediment) by destructively sampling replicate test chambers over the course of a "standard" 10-d assay. Studies with the control sediment and a non-toxic test sample indicated excellent recovery of test animals, even early in the test (e.g., <24 h) when individuals of both species are relatively small. Reasonable, typically monotonic, time-to-death relationships were observed for both H. azteca and C. tentans exposed to three comparatively toxic test sediments, all of which caused significant mortality by 10 d. Use of the time-to-effects approach allowed expression of toxicity of the three samples relative to one another, as well as documentation of decreases in toxicity of one of the sediments with increased storage time. These studies demonstrate the feasibility of use of time-to-effects as a basis for quantifying the relative toxicity of contaminated sediments.