Sediment contamination assessment in urban areas based on total suspended solids

David Andrew Barry, Nathalie Chèvre Rossi, Romuald Curdy, Jonas Margot, Luca Rossi
Elsevier, 2013
Article

Résumé

Sediment represents an important compartment in surface waters. It constitutes a habitat or spawning site for many organisms and is an essential trophic resource for higher level organisms. It can be impacted by anthropogenic activities, particularly through urban wet-weather discharges like stormwater and combined sewer overflows. An approach was presented for assessing the risks caused by urban wet-weather discharges to the sediment compartment based on total suspended solids (TSS). TSS is routinely measured in field surveys and can be considered as a tracer for urban wet-weather contamination. Three assessment endpoints linked with TSS were proposed: a) siltation of the riverbed, b) oxygen demand due to organic matter degradation and c) accumulation of ecotoxic contaminants on the riverbed (heavy metals, PAHs). These criteria were translated in terms of the maximal TSS accumulation load and exposure time (percentage of time exceeding the accumulation criteria) to account for sediment accumulation dynamics and resuspension in streams impacted by urban wet-weather discharges. These assessment endpoints were implemented in a stochastic model that calculates TSS behavior in receiving waters and allows therefore an assessment of potential impacts. The approach was applied to three Swiss case studies. For each, good agreement was found between the risk predictions and the field measurements confirming the reliability of the approach.

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https://infoscience.epfl.ch/record/182378?ln=fr

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David Andrew Barry, Nathalie Chèvre Rossi, Romuald Curdy, Jonas Margot, Luca Rossi
Elsevier, 2013
Article

Résumé

Official source

https://infoscience.epfl.ch/record/182378?ln=fr

À propos de ce résultat

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Assessing toxic impacts on aquatic ecosystems in life cycle assessment (LCA)

Jérôme Payet

In the last decade, several Life Cycle Assessment (LCA) methods for assessing impact of products on living resources have been developed. Beyond the quantified assessments of impacts on living systems, it also checked the feasibility of the impact assessment on human health and ecosystems quality and helps to identify the limits of such methods. Among the different impact categories, that of toxic substances on ecosystems occupies an important place. The extent of these impacts has been stressed on many occasions and the necessity of preserving ecological areas and biodiversity has become a major issue on an international level. By focusing on aquatic ecosystems, this thesis aims at identifying constraints connected with assessment of the impact of chemical substances on ecosystems in LCA and setting up a method for assessing impacts of toxic substances on aquatic ecosystems which meets the requirements of a comparative approach like Life Cycle Assessment. The overall purpose of the thesis is to propose a comparative method for the Life Cycle Impact Assessment of toxics on aquatic ecosystems. With that aim, the dissertation is going throughout 6 major issues: The feasibility of the comparative impact assessment on ecosystems and the identification of associated constraints. The development of a statistical method for comparing impact on ecosystems; The review of the data availability for calculation of Effect Factors. The choice of the most relevant ecotoxicity measure (ECxs1, NOECs2 and LOECs3) for a comparative purpose. The development of best-estimate extrapolation factors for assessing chronic effects based on acute data. The analysis of the ecological realism of the comparative assessment method. These points are analysed throughout the 7 chapters of the thesis. Chapter 1 aims at introducing the thesis. A general presentation of Life Cycle Assessment is proposed, following by a detailed description of the Life Cycle Impact Assessment on ecosystems. This description covers the state of the art of researches and identifies the development needed. Therefore the scope of the thesis and the main points that must be addressed by this research are presented. Chapter 2 starts with a review of existing methods for Life Cycle Impact Assessment on ecosystems (LCIA), the chapter presents the parametric version of the AMI method (Assessment of the Mean Impact), which has been developed during the PhD for the assessment of impact on aquatic ecosystems. For this purpose, a framework and the main requirements for the development of this method are presented. For a comparative assessment, the Hazardous Concentration of a toxic affecting 50% of the species over their chronic EC50 (Effect Concentration affecting 50% of tested individuals), also called HC50EC50, is selected for the calculation of Effect Factors to be implemented in current LCIA methods. The Confidence Interval on the HC50EC50 is provided, enabling comparison between the impact values obtained as results of a Life Cycle Assessment study. The choice of EC50s is based on review of the main ecotoxicological databases, and analysis of the availability and reliability of test results. Moreover, bearing in mind that mostly acute data are available, while LCA deals mainly with chronic exposure, best-estimate extrapolation factors for the HC50EC50 and the associated uncertainty are provided for inorganics, nonpesticide organics, and pesticide organics. Concerning the method itself, in order to find the best methods for calculation of a toxicity indicator, several statistical estimators, parametric and non-parametric approaches are compared, identifying their properties and respective strengths for a comparative method. The analysis relates to both the reliability of the estimator and its Confidence Interval, especially in terms of statistical robustness and Effect Factor stability. Based on these findings, the AMI method is described in detail, and an example of application comparing two wheat crop scenarios differing by the pesticides used is presented. Chapter 3 presents in detail the four methods currently used for the development of Effect Factors for the Life Cycle Impact Assessment (LCIA) on Ecosystems: the parametric version of AMI (Assessment of the Mean Impact) based on HC50EC50s; the Eco-Indicator based on HC50NOECs; USES-LCA based on both HC5NOECs and the Most sensitive species, and the PNEC (Predicted No- Effect Concentration) based on the Most sensitive species. After presentation of the LCIA framework and its main divergences from Environmental Risk Assessment for chemical regulation, the four methods are detailed and applied for the calculation of Effect Factors for 83 substances, covering inorganics, non-pesticide organics, and pesticide organics. Each method is therefore analysed concerning three key points: applicability in the LCA framework, environmental relevance, and statistical reliability. Particular attention is paid to possible bias and the uncertainty, highlighting the following findings: (1) HC5NOECs are on average 50 times higher than the most sensitive species, and this difference in conservatism introduces a bias in the analyses for the method mixing HC5NOECs and most sensitive species. (2) Effect Factors based on the most sensitive species increase the relative weight of the most toxic chemicals by two orders of magnitude, depending on whether the study is based on US or European ecotoxicity databases. (3) the methods based on HC50EC50s and HC5NOECs are the only ones able to provide a Confidence Interval on the Effect Factor, but the Confidence Interval on the HC5NOECs can be more than 10 orders of magnitude greater than that of the HC50EC50s. (4) compared with the Confidence Interval on the HC50EC50s, the most sensitive species cannot be distinguished from HC50EC50s for chemicals characterised by fewer than 5 species, and the HC5NOECs cannot be distinguished from the HC50EC50s for chemicals characterised by fewer than 8 species. Chapter 4 compares two statistical estimators, aiming at calculate the average toxicity of substances on biological species. The two methods provide an estimation of the HC50EC50 and the associated Confidence Interval. On the one hand, parametric method using the geometric mean and a calculation of the confidence interval with Student is considered. On the other hand, a distribution-free method calculates the HC50EC50 based on the median response of species and the confidence interval based on bootstrap. In order to facilitate the use of the non-parametric method, a table linking the number of species tested and the size of the confidence interval is provided for samples from 5 to 500 species. The comparison is based on actual data concerning 191 substances covering inorganics, non-Pesticide organics, and Pesticide organics. The mean and width of the chronic EC50s samples for all the substances are presented. The Shapiro-Wilk test is performed for the 191 EC50s samples and the assumption of log-normality of the distribution failed in more than 20% of the cases. Two causes of this non Log-normality are identified; (1) the skewness, which is shown to be an important issue for the assessment of the average toxicity of chemicals while (2) the multi-modal distributions, which are not likely to influence considerably the final result. A detailed application of the two methods is done with the comparison of two herbicides, the Sulfosulfuron and the Prosulfuron, where the distribution-free method appears to be more powerful than the parametric for a substance-to-substance comparison. Nevertheless, the distribution-free method requires a minimum of 5 chronic EC50s, that cannot be satisfied in most cases. Chapter 5 aims at illustrating the previous chapter in using the nonparametric version of the AMI method for the comparative assessment of the impacts of metals on aquatic ecosystems. This chapter briefly describes the method, then it focuses on the comparative analysis of 9 metals sometimes tested with different salts and speciations. Two interesting results can be highlighted: (1) the toxicity of metals covers the whole range of toxicity of chemicals; (2) the confidence interval of the HC50EC50 for metals is on average twice as great for metals compared with other chemicals. This increase in the variability of ecotoxicological responses from species is likely to be due to the change in bioavailability of metals associated with a change of test conditions (e.g. pH, or Organic Matter). Chapter 6 reviews and analyses the reliability of existing aquatic toxicity databases which can be used for the calculation of Effect Factors for Life Cycle Impact Assessment (LCIA). For that purpose, the main LCIA methods are presented focusing on their data requirement. It concerns: EDIP4 (based on the PNEC); AMI5 (based on parametric HC50EC50); Eco-Indicator (based on the HC50NOEC); USES-LCA (based on the HC5NOEC). Moreover 6 ecotoxicity databases available in an electronic format are analysed: Aquire; Pesticide Ecotoxicity Database (PED); IUCLID; Acute Toxicity Database (ATD); Fathead Minnow database (FMD); and ECETOC Aquatic Toxicity Database (EAT). The analysis especially focuses on the identification of the substances and organisms, the definition of the tests conditions, and the control procedure of the database. A selection of tests is done, retaining a dataset of 128,864 tests results, acute, sub-chronic and chronic. A description of the data availability on the basis of the selected test is performed, considering the available EC50s (Effect Concentration affecting 50% of the individuals tested), LOECs and NOECs (Lowest or No Observed Effect Concentration). The number of covered substances is also analysed regarding the number of species or phyla considered. On that basis, an estimation of the maximum number of possible Effect Factors is performed. The results highlight the discrepancy between the large number of test results available (128,864), and the relatively restricted number of Effect Factors (betweeen 34 and 4959 depending on the method)) that can be calculated for a comparative purpose like LCIA. Chapter 7 provides a conclusion to the work, answering the points underlined in introduction. Then, the fey features of the AMI method are restated and the perspectives and output of the work are presented. In the last part of the thesis, the AMI HC50EC50 database is presented. It provides acute and chronic HC50EC50 data calculated with the parametric version of AMI (geometric mean of the EC50s and confidence interval based on Student) for 522 susbtances. ------------------------------ 1 ECx: concentration of susbtance that affects 50% of the individuals tested for a given effect. 2 NOEC: No Observable Effect Concentration 3 LOEC: Lowest Observable Effect Concentration 4 EDIP: Environmental Design for Industrial Product 5 AMI : Assessment of the Mean Impact

EPFL2004

Chargement

Eukaryotic microorganisms are an essential component of the Earth's global diversity. It is believed that the number of protistan taxa far outnumbers the one of viruses and bacteria. The taxonomic classification of these organisms, which also represent the major part of the total eukaryotic diversity, is still not very well known. It is only lately that the main phylogenetically consistent eukaryotic super assemblages (also called "kingdoms") have been defined. Inside these kingdoms, lateral branches represent the main multicellular taxa, the plants, animals and fungi. Protists are present in virtually all environments; in this thesis, attention was focused on the soil as habitat for the eukaryotic microorganisms. The communities inhabiting soil are characterized by adaptations to drought (the capacity to form cysts). Moreover, certain groups are found exclusively in this environment, to which they are morphologically adapted, whereas others are absent and exclusively found in aquatic systems. Detailed studies on the ecology of certain groups have been performed, and it is possible to define amongst them typical fast reproducing, early colonizers for new environments (r-specialists), whereas others can be found only in stable and highly productive habitats (K-specialists). All these organisms are distributed in a heterogeneous manner in the soil, being usually more frequent in the top horizon and around hotspots such as, for instance, root tips. Prokaryotes have drawn most of the attention of microbial ecologists, who almost neglected the eukaryotic microbes with the exception of fungi. Ecologists usually define four categories ("guilds") of protists in soil: Flagellates, naked amoebae, testate amoebae and ciliates. The importance of protistan activity in soil ecosystems has been shown with the concept of microbial loop: nutrients, produced by autotrophic organisms, are taken up by decomposers (bacteria and fungi) to produce their own biomass. Heterotrophic protists, by preying on them, release these compounds in a form which can be directly used by the autotrophs ("mineralization"), thus closing the loop. This phenomenon is of major significance, because protistan grazing controls the composition and activity of the prokaryotic community, and also the growth of the autotrophs. In soil, this phenomenon takes mainly place at the tip of the roots of vascular plants, where exudates are released. When soils are exposed to an organic pollution, the protistan communities and thus also their impact on the microbial loop, are influenced in two different ways: either by the direct toxic effects of the pollutant and or the indirect effects on their bacterial preys. A detailed study on the negative effects of environmental pollution, however, requires reliable methods to study protists. Molecular approaches offer the possibility to study protists in situ without the limitations inherent to cultivation dependent approaches. The aim of this thesis was to develop molecular methods and to apply these in combination with classical approaches for the characterization of protistan communities in a polycyclic aromatic hydrocarbon contamined and a non-contaminated control soil (PAH). The eukaryotic communities in a PAH polluted and a non-polluted control soil were first compared by amplifying total soil DNA with eukaryotic domain-specific primers targeting the 18S rRNA genes, cloning and sequencing the resulting PCR products. Using non-specific eukaryotic primers proved to be non-applicable for a reliable analysis of the 18S rRNA gene pools in soil, since protistan 18S rRNA gene sequences were (with the exception of the genus Acanthamoeba) underrepresented in the clone libraries obtained.. The biased picture obtained in the first chapter of the thesis was clearly shown when protist were cultivated from both soils: enrichment and cultivation of protists confirmed that members of the genus Acanthamoeba were indeed the most common protists in polluted soils, whereas they were completely absent from the control soil. Additionally, a diverse protistan community was recovered, which could not be detected by the molecular 18S rRNA-based approach. Twenty-two isolates of flagellates and naked amoebas were obtained, and characterised morphologically as well as by 18S rRNA gene sequence analysis. The diversity of cultivated organisms from the polluted soil was lower as compared to the control soil; however, the total number of protists was higher. Some of the cultures obtained in this cultivation dependant approach were used for further detailed studies; a jakobid isolate was described using light and electron microscopy, thus providing new insights into the knowledge of a relatively unknown group of excavates, i.e. the group of Jakoba incarcerata. Other cultures belonging to the kineoplastea were used to design a set of 18S rRNA-targeting fluorescently labelled oligonucleotide probes for fluorescence in situ hybridization. These probes are specific for the detection of the class Kinetoplastea and four genera within the class, i.e. Bodo, Parabodo, Rhynchomonas and Dimastigella and were applied to pure cultures and to environmental samples obtained by the so-called coverslip method. The effect of the PAH-pollution on a selected soil protistan guild, the ciliates, was further analyzed by applying ciliate-specific PCR based techniques. A specific primer set was used to amplify ciliate 18S rRNA genes from the environment and to conduct comparative sequence analysis of environmental clone libraries. This study indicated that the ciliate 18S rRNA gene pools present in the polluted soil were less diverse than those of the control soil. They contained mainly representatives of the class Colpodea, a clade of r-selected ciliates, typical for unstable environments. The control soil was characterized by a variety of trophic specialists, including carnivores, cyanobacteria and diatom feeders, in contrast to the polluted soil, which harboured mainly sequences affiliating to bacterivores and generalists. Based on these results, we could deduce that the trophic webs are less complex in a PAH polluted soil in comparison to a pristine control. This observation was further confirmed when we studied a larger number of samples using a fingerprinting technique, i.e. denaturing gradient gel electrophoresis (DGGE) with ciliate specific PCR primers. The profiles obtained showed again a dominance of the members of the class Colpodea in polluted soils.

EPFL2005

Chargement

Endocrine disruption in soil invertebrates

Sophie Campiche

In the past years, it has been observed that some compounds present in our environment can disturb the reproduction and development of animals like fishes, birds, or reptiles by interfering with their endocrine system. Indeed, these endocrine disrupting compounds (EDC) can mimic or antagonize the effects of hormones, alter the pattern of synthesis and metabolism of hormones or modify hormone receptor levels. These substances represent a risk for wildlife, and possibly for humans. Up to now, endocrine disruption was mainly evaluated for vertebrates and aquatic organisms and for oestrogeniclike substances. However, soil invertebrates, which play an important role in soil functioning, have rarely been considered. Moreover, as their endocrine system differs substantially from those of vertebrates (estrogens do not seem to regulate endocrine functions in invertebrates), other substances than can mimic invertebrate hormones should be taken into account. In this sense, insect growth regulators (IGR), which are third generation insecticides specially developed to interfere with insect endocrine system, are interesting compounds. These substances are supposed to have a high specificity for insect pest and a low toxicity for non-target organisms. In the first part of this study, the sublethal effects of six IGR (methoprene, fenoxycarb, precocene II, tebufenozide, hexaflumuron and teflubenzuron) were evaluated on the non-target soil arthropod Folsomia candida. The collembola F. candida represents an integral and beneficial part of the soil ecosystem. It is an euedaphic (subsurface) species which plays an important role in soil respiration and decomposition processes and is therefore vulnerable to the effects of soil contamination. This ecologically relevant organism is one of the most appropriate invertebrate test species for the assessment of environmental quality. It is recommended as test organism by the international standard ISO 11267. The 28-days reproduction tests conducted according to this protocol show that F. candida is affected by the chosen IGR. The most toxic compounds were the two chitin synthesis inhibitors, teflubenzuron and hexaflumuron, with an EC50 of 0.05 mg/kg (dw) for teflubenzuron and an EC50 of 0.6 mg/kg for hexaflumuron. These concentrations are probably environmentally relevant (toxicity/exposure ratios

EPFL2006

Chargement

Assessing toxic impacts on aquatic ecosystems in life cycle assessment (LCA)

Jérôme Payet

EPFL2004

Endocrine disruption in soil invertebrates

Sophie Campiche

EPFL2006

EPFL2005