Georg Streck

Polycyclic aromatic hydrocarbon (PAH) contamination of surface sediments and oysters from the inter-tidal areas of Dar es Salaam, Tanzania

Surface sediment and oyster samples from the inter-tidal areas of Dar es Salaam were analyzed for 23 polycyclic aromatic hydrocarbons (PAHs) including the 16 compounds prioritized by US-EPA using GC/MS. The total concentration of PAHs in the sediment ranged from 78 to 25,000 ng/g dry weight, while oyster concentrations ranged from 170 to 650 ng/g dry weight. Hazards due to sediment contamination were assessed using Equilibrium Partitioning Sediment Benchmarks and Threshold Effect Levels. Diagnostic indices and principle component analysis were used to identify possible sources. Interestingly, no correlation between sediment and oyster concentrations at the same sites was found. This is supported by completely different contamination patterns, suggesting different sources for both matrices. Hazard assessment revealed possible effects at six out of eight sites on the benthic communities and oyster populations. The contribution of PAH intake via oyster consumption to carcinogenic risks in humans seems to be low.

How to confirm identified toxicants in effect-directed analysis

AbstractDue to the production and use of a multitude of chemicals in modern society, waters, sediments, soils and biota may be contaminated with numerous known and unknown chemicals that may cause adverse effects on ecosystems and human health. Effect-directed analysis (EDA), combining biotesting, fractionation and chemical analysis, helps to identify hazardous compounds in complex environmental mixtures. Confirmation of tentatively identified toxicants will help to avoid artefacts and to establish reliable cause–effect relationships. A tiered approach to confirmation is suggested in the present paper. The first tier focuses on the analytical confirmation of tentatively identified structures. If straightforward confirmation with neat standards for GC–MS or LC–MS is not available, it is suggested that a lines-of-evidence approach is used that combines spectral library information with computer-based structure generation and prediction of retention behaviour in different chromatographic systems using quantitative structure–retention relationships (QSRR). In the second tier, the identified toxicants need to be confirmed as being the cause of the measured effects. Candidate components of toxic fractions may be selected based, for example, on structural alerts. Quantitative effect confirmation is based on joint effect models. Joint effect prediction on the basis of full concentration–response plots and careful selection of the appropriate model are suggested as a means to improve confirmation quality. Confirmation according to the Toxicity Identification Evaluation (TIE) concept of the US EPA and novel tools of hazard identification help to confirm the relevance of identified compounds to populations and communities under realistic exposure conditions. Promising tools include bioavailability-directed extraction and dosing techniques, biomarker approaches and the concept of pollution-induced community tolerance (PICT). FigureToxicity confirmation in EDA as a tiered approach

Toxicity assessment of sediments from three European river basins using a sediment contact test battery

The toxicity of four polluted sediments and their corresponding reference sediments from three European river basins were investigated using a battery of six sediment contact tests representing three different trophic levels. The tests included were chronic tests with the oligochaete Lumbriculus variegatus, the nematode Caenorhabditis elegans and the mudsnail Potamopyrgus antipodarum, a sub-chronic test with the midge Chironomus riparius, an early life stage test with the zebra fish Danio rerio, and an acute test with the luminescent bacterium Vibrio fischeri. The endpoints, namely survival, growth, reproduction, embryo development and light inhibition, differed between tests. The measured effects were compared to sediment contamination translated into toxic units (TU) on the basis of acute toxicity to Daphnia magna and Pimephales promelas, and multi-substance Potentially Affected Fractions of species (msPAF) as an estimate for expected community effects. The test battery could clearly detect toxicity of the polluted sediments with test-specific responses to the different sediments. The msPAF and TU-based toxicity estimations confirmed the results of the biotests by predicting a higher toxic risk for the polluted sediments compared to the corresponding reference sediments, but partly having a different emphasis from the biotests. The results demonstrate differences in the sensitivities of species and emphasize the need for data on multiple species, when estimating the effects of sediment pollution on the benthic community.

Polar Compounds Dominate in Vitro Effects of Sediment Extracts

Sediment extracts from three polluted sites of the river Elbe basin were fractionated using a novel online fractionation procedure. Resulting fractions were screened for mutagenic, aryl hydrocarbon receptor (AhR)-mediated, transthyretin (TTR)-binding, and estrogenic activities and their potency to inhibit gap junctional intercellular communication (GJIC) to compare toxicity patterns and identify priority fractions. Additionally, more than 200 compounds and compound classes were identified using GC-MS/MS, LC-MS/MS, and HPLC-DAD methods. For all investigated end points, major activities were found in polar fractions, which are defined here as fractions containing dominantly compounds with at least one polar functional group. Nonpolar PAH fractions contributed to mutagenic and AhR-mediated activities while inhibition of GJIC and estrogenic and TTR-binding activities were exclusively observed in the polar fractions. Known mutagens in polar fractions included nitro- and dinitro-PAHs, azaarenes, and keto-PAHs, while parent and monomethylated PAHs such as benzo[a]pyrene and benzofluoranthenes were identified in nonpolar fractions. Additionally, for one sample, high AhR-mediated activities were determined in one fraction characterized by PCDD/Fs, PCBs, and PCNs. Estrone, 17β-estradiol, 9H-benz[de]anthracen-7-one, and 4-nonylphenol were identified as possible estrogenic and TTR-binding compounds. Thus, not only nonpolar compounds such as PAHs, PCBs, and PCDD/Fs but also the less characterized and investigated more polar substances should be considered as potent mutagenic, estrogenic, AhR-inducing, TTR-binding, and GJIC-inhibiting components for future studies.

Automated fractionation procedure for polycyclic aromatic compounds in sediment extracts on three coupled normal-phase high-performance liquid chromatography columns

Polychlorinated biphenyls, naphthalenes, dibenzo-p-dioxins and furans, as well as polyaromatic hydrocarbons (PAHs), hydroxy-, keto- and nitro-PAHs and sulphur, oxygen and nitrogen heterocycles represent major groups of toxicants in contaminated sediments. The identification of toxic substances in effect-directed analysis is often based on a group-specific fractionation of these polycyclic aromatic compounds (PACs). Several fractionation steps using different methods, solvent exchange and concentration steps are generally necessary to achieve this aim increasing the risk of losses and artefact formation. In order to avoid these disadvantages and to enhance the throughput, an automated on-line fractionation method was developed using coupled and automatically connected columns, including cyanopropyl- and nitrophenylpropyl-bonded silica and porous graphitised carbon stationary phases. Exploiting the potential of each column, compounds are separated mainly according to their polarity, number of aromatic carbons and planarity. Excellent group-specific resolution, high reproducibility and good recoveries suggest that this method is suitable for the fractionation of a multitude of major sediment contaminants in one HPLC-run.

Active bio-monitoring of contamination in aquatic systems—An in situ translocation experiment applying the PICT concept

The environmental risk assessment of toxicants is often derived from chemical monitoring, based on single species tests performed in the laboratory. However, to provide ecologically relevant information, community approaches are required. The aim of this study was to causally link prometryn exposure to community-level effects in complex field situations and to identify response times of adaptation to pollution and recovery from pollution. For this reason sensitivity shifts in communities were detected and related to structural changes within the periphyton community. Furthermore, it was intended to illustrate the possibility of a combined approach of community translocation and sensitivity assessment for active monitoring of polluted sites. Periphyton was grown at a reference (R) and at a polluted (P) site of the river Elbe basin for 26 days, was subsequently transferred from the polluted site to the reference site and vice versa. Sensitivity of communities to prometryn was determined according to the pollution-induced community tolerance (PICT)-concept in short-term tests by measuring photosynthesis inhibition and was related to structural changes in algal class and diatom species composition. Exposure to prometryn was determined using polar organic integrative samplers (POCIS), giving time-weighted average concentrations. Environmental concentrations of prometryn were significantly higher at the polluted site compared to the reference site. Communities grown at the polluted site showed a higher tolerance to prometryn in comparison to the reference site. 17 Days after the translocation to the reference site, EC(50) decreased 2-fold compared to the non-translocated P-community of the same age. By contrast, EC(50) of the community grown at the reference site was 5 times higher after 17 days exposure at the polluted site. Furthermore, P-R communities were less sensitive to prometryn (higher EC(50)) than R-P communities, 24 days after translocation. These changes in sensitivity to prometryn were consistent with changes in species composition and clearly indicate that the exposure history of communities is defining the time-response of recovery and adaptation. In conclusion, the PICT-concept is shown to be a suitable tool for analysis of recovery and adaptation processes of communities under natural conditions. Therefore, it improves the link between cause and effect in field situations. In situ translocation studies provide an ecological relevant assessment of pesticide effects under field conditions and could be used as a diagnostic tool in active monitoring for decision-making frameworks as used in the implementation of the European Water Framework Directive (WFD).

Identification of a phytotoxic photo-transformation product of diclofenac using effect-directed analysis

The pharmaceutical diclofenac (DCF) is released in considerably high amounts to the aquatic environment. Photo-transformation of DCF was reported as the main degradation pathway in surface waters and was found to produce metabolites with enhanced toxicity to the green algae Scenedesmus vacuolatus. We identified and subsequently confirmed 2-[2-(chlorophenyl)amino]benzaldehyde (CPAB) as a transformation product with enhanced toxicity using effect-directed analysis. The EC(50) of CPAB (4.8 mg/L) was a factor of 10 lower than that for DCF (48.1 mg/L), due to the higher hydrophobicity of CPAB (log K(ow) = 3.62) compared with DCF (log D(ow) = 2.04) at pH 7.0.

Characterizing field sediments from three European river basins with special emphasis on endocrine effects - A recommendation for Potamopyrgus antipodarum as test organism

The assessment of endocrine disrupting potentials of field sediments has until now been mostly limited to classical chemical analysis, in vitro assays and in vivo bioassays performed with vertebrates. There is an urgent need for easy, cheap and reproducible invertebrate tests which may be applied in certain monitoring activities. Since the mudsnail Potamopyrgus antipodarum is known to be tolerant to natural stressors, but also sensitive to endocrine disrupting chemicals, it is very likely that this organism could be suitable for the assessment of endocrine effects of e.g. field sediments. Within this study the endocrine potential of sediments in three European river basins was assessed. The yeast estrogen screen (YES) and a sediment contact test with P. antipodarum were performed. Furthermore, analyses of physico-chemical properties and concentrations of heavy metals, PAHs, organotins, natural steroids and alkylphenols were done. In the sediment contact test, the reproduction of the snail was promoted by a part of the sediments. This phenomenon could not be explained by their physico-chemical properties. However, at some of those sites a high estrogenic activity was detected in the YES, leading to the assumption that endocrine disrupting compounds could be responsible for those effects. This assumption could be confirmed to some extent with partially high concentrations of xeno-estrogens (e.g. nonylphenol) at the certain sites. Our study demonstrates the applicability of the test with P. antipodarum for a variety of sediments and once again points out the need of suitable in vivo biotests for the risk assessment of field sediments.

Effect-directed analysis of contaminated sediment from the wastewater canal in Pancevo industrial area, Serbia

Wastewater canal (WWC) in Pancevo industrial area in Serbia, whose main environmental receptor is the River Danube, is a well known hot-spot of contamination. WWC sediments have been assessed by UNEP based on chemical target analysis. However, integrative biological data on exposure to hazardous compounds are only provided by the present study which aims at evaluating whether the monitored compounds sufficiently reflect potential hazards and to suggest additional compounds to include in monitoring and hazard assessment by applying effect-directed analysis (EDA) based on arylhydrocarbon receptor-mediated activity and cytotoxicity. Multistep NP-HPLC fractionation provided 18 fractions co-eluting with polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polycyclic aromatic hydrocarbons (PAHs) and more polar compounds. PAHs fractions exhibited great potencies to induce ethoxyresorufin-o-deethylase (EROD) in H4IIE rat hepatoma cell line expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ) (0.1-34.6 x 10(3) pg g(-1)dry weight). Chemical analysis of the most active fractions revealed great concentrations of PAHs (up to 292 x 10(2)ngg(-1) sediment equivalents (SEQ)), methylated PAHs (up to 900 x 10(2) ng g(-1) SEQ), and other alkyl-substituted PAHs. Only minor portions of biologically derived TCDD-EQs could be attributed to monitored PAHs with known relative potencies (REPs). We hypothesize that a major part of the activity is due to non-monitored alkylated and heterocyclic PAHs. Results of the cell cytotoxicity/proliferation assay on H4IIE cell line suggest the presence of sediment pollutants with pronounced potency to disturb cell growth.

Effect directed analysis of riverine sediments—The usefulness of Potamopyrgus antipodarum for in vivo effect confirmation of endocrine disruption

In vivo tests are not commonly used in effect directed analysis (EDA) approaches. In the present study, a novel methodology was developed whereby Potamopyrgus antipodarum, which is known to be sensitive to endocrine disrupting compounds, was used as test organism. Field sediments from a polluted site in the north of Belgium were extracted and fractionated using three coupled and automatically switched normal-phase HPLC columns. Part of the fractions were spiked to artificial sediments and tested in a sediment contact test with P. antipodarum. The other part was used for an in vitro effect confirmation with the ER-LUC and anti-AR CALUX assays. Two of the six tested fractions stimulated the reproduction of the snails, while two others inhibited the reproduction. The fractions that caused an increase in reproduction also showed an increased estrogenic potency in the ER-LUC assay. Chemical analysis revealed that one of the most prominent compounds in those fractions was bisphenol-A, which has already been reported to have a stimulating effect on the reproduction of P. antipodarum by other authors. Due to the fact that previous studies have shown that this snail is also present in the field at this certain site, it was possible to directly link the results with effects that were observed in the field. This study indicates that effect directed analyses, supported by in vivo biotests, are very useful tools in order to identify the compounds that cause adverse effects on organisms or even population level.