Ecotoxicological characterisation of sediments from stormwater retention basins.

Retention-detention basins are important structures for managing stormwater. However, their long-term operation raises the problem of managing the sediments they accumulate. Potential uses for such sediments have been envisaged, but each sediment must be characterised beforehand to verify its harmlessness. In this paper we address this issue through the development of a battery of bioassays specifically adapted to such sediments. We tested the method on samples taken from four retention basins in the region of Lyon (France). This battery focuses on the toxic effects linked to both the solid phase (ostracod and Microtox(®) solid-phase tests) and the liquid-phase (interstitial water) of sediments (rotifer and Microtox(®) liquid-phase tests). The results obtained permit the sorting of sediments presenting little toxicity, and which could therefore be potentially exploitable, from those from more polluted areas presenting higher toxicity that limits their use.

Selection of a halophytic plant for assessing the phytotoxicity of dredged seaport sediment stored on land.

The filling of dry quarries in coastal areas with sediments dredged in seaports represents a potentially interesting method of recycling of these materials. However, this recycling requires the prior carrying out of an Environmental Risk Assessment of the scenario concerned. For this, the question arose as to the type of plants capable of developing on the surface of such a deposit and the method to implement for assessing the possible phytotoxicity of dredged sediments. To answer this question, we chose to work with halophytic plants to be free from the salt-related effect and to assess only the effect related to the toxic compounds present. Based on the objectives set, these works led to the use of common plants of the French coast, with direct seeding, and with pollution-sensitive plants. Three species of angiosperms, Armeria maritima, Anthemis maritima and Plantago coronopus, were finally tested. As a result of this work, Armeria maritima was retained as the most suitable plant for testing the possible phytotoxic effect of dredged marine sediments stored on land. The results obtained with this plant are as follows: germination of 40 % of the seeds in 31 days, produced biomass of 493 mg FW in 6 months and a capacity to bioaccumulate metal pollutants in roots with 350 and 720 mg/kg DW for Zn and Cu, respectively.

Assessment of the phytotoxicity of seaport sediments in the framework of a quarry-deposit scenario: germination tests of sediments aged artificially by column leaching.

The aim of the Sustainable Management of Sediments Dredged in Seaports (SEDIGEST) project is to assess the risks of treated port sediments for terrestrial ecosystems when deposited in quarries. We simulated the "ageing" of these sediments up to the "moment" when plants can germinate. Sediments were leached by water percolating through a laboratory column. Sediments 1 and 2, taken from the port of Toulon (France), were dried and aired. Sediment 3, taken from the port of Guilvinec (France), was stabilised with lime. Phytotoxicity was evaluated on the three artificially aged sediments using germination and early development tests (48 h to 7 days) by Phytotoxkit F(TM) bioassays. The three dilutions tested were performed with the reference "ISO substrate" and with Lolium perenne sp. (rye grass), Sinapis alba (white mustard), and Lepidium sativum (watercress). The tests performed with sediments 1 and 2 showed (1) a decrease of their toxicity to the germination of the species selected following leaching and (2) that L. perenne was the most sensitive species. The tests performed with sediment 3 showed that it was improper for colonisation even after leaching simulating 16 months of ageing. These germination tests on aged sediments identified the effects of leaching and made it possible to appreciate the capacity of the sediments to allow colonisation by plants.

Identification and prioritization of bioaccumulable pharmaceutical substances discharged in hospital effluents.

The consumption of pharmaceuticals and their excretion in wastewater is a continuous source of pollution for aquatic ecosystems. In certain cases these compounds are found in the environment at concentrations high enough to cause disturbance in aquatic organisms. Aware of this problem hospitals are giving increasing attention to the nature of their effluents and their impact on the environment, by implementing more efficient effluent management policies. This concern is justified in view of the large volumes of toxic products consumed (detergents, disinfectants, pharmaceuticals, chemical reagents, radioactive elements, etc.). Moreover, these effluents usually do not undergo any specific treatment before being discharged into urban sewage networks. In this article, we present a method for selecting the pharmaceuticals discharged in hospital effluents that have the worst impact on the aquatic ecosystem, primarily based on their bioaccumulation potential. This study focused on the pharmaceuticals consumed at the Hospices Civils de Lyon (HCL), the second largest hospital structure in France (5200 hospital beds). Of the 960 substances consumed in HCL hospitals, a shortlist of 70 substances considered as being potentially bioaccumulable was established. The use of aggravating factors of risk has then led to the final selection of 14 priority compounds. They include 4 compounds consumed in large quantities in HCL hospitals, 6 endocrine disruptors and 4 potentially ecotoxic compounds. For all these compounds, it is now advisable to verify their bioaccumulation potential experimentally and confirm their presence in the environment. In addition, in order to monitor the risk relating to possible contamination of the food chain, it will be necessary to measure accumulated dose levels in species of different trophic levels. Lastly, chronic ecotoxicity tests will permit evaluating the danger and risk that some of these substances may represent for aquatic ecosystems.

Benefits and limits of sediment toxicity tests as an aid to decision-making.

With respect to the management of dredged sediments, a crucial issue is whether the removed materials (watered and/or processed) are disposed of or reused in an environmentally sound manner. In this context, the number of studies dealing with hazard or risk assessment has exponentially increased. This emphasis has resulted in the promotion and application of a very large variety of ecotoxicological tests. As a consequence, there is a clear need to highlight the scope and limitations of these tests for their appropriate selection and interpretation. In this paper we discuss the choice, implementation and interpretation of laboratory tests carried out on aquatic organisms at various levels of biological organization. We examine some experimental tools and methods in order to determine how suitable they are in regard to the objectives for which they are employed. To make this discussion more consistent our paper is based on results from research programmes conducted for governmental organizations and industrial partners. The Laboratoire des Sciences de l'Environnement (LSE) was involved with Cemagref de Lyon in a first methodological programme on risk assessment of scenarios of dredged sediment deposition. Another programme for a chemical company was implemented to assess the benefits of a physico-chemical treatment applied to contaminated dredged sediments in a scenario of reuse or deposit in gravel pits. Currently, the LSE is working on a programme of risk assessment for road sediments in valorization scenarios. From these programmes, we expose how single-species tests, as well as more complex bioassays and microcosm tests, can be used in an iterative step of risk assessment. Concerning microcosm tests, we also introduce a more realistic system that has been designed to simulate natural hydraulic conditions of gravel pits to assess the effects of toxicants on gravel pit aquatic biota during the sediment immersion phase and the sediment post-deposition phase (paper in preparation). The benefits of these ecotoxicological approaches are underlined, but limits are discussed with regard to several criteria: ecological relevance, realism, use for decision-making, cost and complexity of methods involved.

Daily physicochemical, microbiological and ecotoxicological fluctuations of a hospital effluent according to technical and care activities.

The problem of hospital effluents falls into the framework of hazardous substances due to the specific substances used and discharged for the most part into urban drainage networks without prior treatment. This in-depth study has led to greater understanding of the effluents discharged by hospitals. The experimental program implemented consisted in carrying out parallel sampling of the effluents of one hospital: a 24 h-average sample and 5 periodic samples corresponding to fractions of times and hospital activities. The samples were characterized by physicochemical, microbiological and ecotoxicological analyses. The results highlight that the effluents contained very little bacterial flora and a moderate organic pollution. However, a numerous of specific pollutants were detected: AOX, glutaraldehyde, free chlorine, detergents, Freon 113 as well as alcohols, acetone, formaldehyde, acetaldehyde, ammonium, phenols and several metals. The battery of bioassays showed that the effluents had a high level of ecotoxicity partly linked to particles in suspension and, that pollution fluctuated greatly during the day in connection with hospital activities. Finally, the PNEC values compared to the concentrations of pollutants dosed in the effluents highlighted that their toxicity was mainly due to several major pollutants, in particular free chlorine. Some hypotheses require additional experiments to be carried out. They concern: reactions of fermentations likely to occur in the drainage network and to form secondary toxic compounds, retention of chlorine by particles and physicochemical characterization of suspended solids.

Effects of road runoff on biomass and metabolic activity of periphyton in experimental streams.

Aquatic ecosystems could be enriched with inorganic and organic matters after road runoff discharge. In this context, we studied the effects of road runoff on river biofilms (periphyton). To operate under controlled conditions the experiments were carried out in two indoor experimental streams. Glass slides were used as artificial substrates for the periphyton colonisation in the experimental streams. Current velocity was maintained at 12 cms(-1) (slow) in the first experimental stream and at 50 cms(-1) (fast) in the second one. The periphyton communities were periodically exposed to road runoff over 30 days. For this experiment, the road runoff was collected in settling basins of a motorway during rainfall events. The runoff was then characterised according to physical and chemical parameters. We tested two exposure durations (1 and 4 h) and two runoff dilutions (10% and 50%). Two laboratory experiments carried out during this study revealed that the biomass (AFDW: 0.92-2.83 g m(-2)), the chlorophyll a content (6.8-78.9 mg m(-2)) and the metabolic activity (net primary production: 61-334 m gO(2) m(-2)h(-1) and respiration: 17.2-68.3 mg O(2) m(-2) h(-1)) of the biofilms increased (p < 0.05). However, this was a function of current velocity, the runoff exposure duration, and the content in organic and inorganic elements present in the tested rainwater. Experimental streams constituted a simplified natural system, which did not allow the reproduction of all the environmental conditions. Thus, these experiments should be performed on natural sites.

Dynamics of toxicity within different compartments of a peri-urban river subject to combined sewer overflow discharges.

Combined Sewer Overflows (CSO) in small peri-urban streams and rivers are potentially toxic for their biocenosis. Improving the management of CSO discharges requires better knowledge of their dynamics and toxicity. In view to characterizing this toxicity, we sampled the different compartments (benthic and hyporheic zone) of a peri-urban stream located near the city of Lyon in France. The samples were taken at different distances from a CSO and at three period characteristic of different hydrological conditions. Their toxic effects were assessed by bioassays on the dissolved fraction (D. magna, V. fisheri and B. calyciflorus bioassays) and on the particle fraction (V. fisheri and H. incongruens bioassays). The results highlighted significant toxicity of the particulate fraction for the benthic and hyporheic samples, in particular downstream of the CSO, but with high spatio-temporal variability. This variability can first be attributed to the variability of CSO discharge sampling as a function of season and rainfall, and the dynamics of polluted particles (trapping of transported particles in infiltration zones, mobilization during floods). These parameters play a fundamental role in the distribution of pollutants according to the geomorphology of stream facies. Regarding dissolved pollutants, the chemical exchanges taking place at the "water-sediment" interface trigger the transfer of pollutants from one phase to another, after which the dispersion of these pollutants is governed by hydraulic flows. Finally, critical zones and periods are identified for the peri-urban river toxicity studied: benthic sediments under mean flow downstream; hyporheic sediments after a storm event downstream, close to the CSO. Recommendations are made on the basis of the knowledge obtained to optimize the management of these discharges.

Ecotoxicological risk assessment of hospital wastewater: a proposed framework for raw effluents discharging into urban sewer network.

In hospitals a large variety of substances are in use for medical purposes such as diagnostics and research. After application, diagnostic agents, disinfectants and excreted non-metabolized pharmaceuticals by patients, reach the wastewater. This form of elimination may generate risks for aquatic organisms. The aim of this study was to present: (i) the steps of an ecological risk assessment and management framework related to hospital effluents evacuating into wastewater treatment plant (WWTP) without preliminary treatment; and (ii) the results of its application on wastewater from an infectious and tropical diseases department of a hospital of a large city in southeastern France. The characterization of effects has been made under two assumptions, which were related to: (a) the effects of hospital wastewater on biological treatment process of WWTP, particularly on the community of organisms in charge of the biological decomposition of the organic matter; (b) the effects on aquatic organisms. COD and BOD5 have been measured for studying global organic pollution. Assessment of halogenated organic compounds was made using halogenated organic compounds absorbable on activated carbon (AOX) concentrations. Heavy metals (arsenic, cadmium, chrome, copper, mercury, nickel, lead and zinc) were measured. Low most probable number (MPP) for faecal coliforms has been considered as an indirect detection of antibiotics and disinfectants presence. For toxicity assessment, bioluminescence assay using Vibrio fischeri photobacteria, 72-h EC50 algae growth Pseudokirchneriella subcapitata and 24-h EC50 on Daphnia magna were used. The scenario allows to a semi-quantitative risk characterization. It needs to be improved on some aspects, particularly those linked to: long term toxicity assessment on target organisms (bioaccumulation of pollutants, genotoxicity, etc.); ecotoxicological interactions between pharmaceuticals, disinfectants used both in diagnostics and in cleaning of surfaces, and detergents used in cleaning of surfaces; the interactions into the sewage network, between the hospital effluents and the aquatic ecosystem.

Interactions between a polycyclic aromatic hydrocarbon mixture and the microbial communities in a natural freshwater sediment.

The toxicity of a polycyclic aromatic hydrocarbon (PAH) mixture was assessed on the indigenous microbial communities of a natural freshwater sediment. The fate and effects of the PAH mixture (phenanthrene, fluoranthene and benzo(k)fluoranthene) were studied over 28 days. Bacterial communities were described by bacterial counts (total bacteria and viable bacteria), and by some hydrolytic enzyme activities (beta-glucosidase and leucine-aminopeptidase), PAH concentrations were measured in the overlying waters and in the sediments. No effect of PAH was detected at 30 mg/kg for all bacterial parameters. At 300 mg/kg, the quantity of total bacteria and the proportion of viable bacteria markedly decreased, compared to the control (0 mg PAH/kg). At 300 mg/kg, an increase of the beta-glucosidase activity and a decrease of the leucine-aminopeptidase activity were observed. For all treatments, the benzo(k)fluoranthene concentration in the sediment was stable over 28 days whereas, in the same time, only 3-6% of the initial concentrations of phenanthrene and fluoranthene remained. This study shows that (1) PAH induce perturbations of sediment microbial communities in terms of density and metabolism (but not always as an inhibition), (2) indigenous bacteria of sediments might be used for toxicity assessment of specific organic pollutants, (3) native microorganisms of sediment seem to have a high capacity for PAH degradation, depending on the physico-chemical properties and the bioavailability of the substance encountered.

Methodological approach towards the definition of new storage conditions for inert wastes.

In 1997, the French Ministry of Environment launched studies aiming to define a specific regulation concerning inert waste disposal in order to limit potential impact of such facilities on the environment by fixing minimum requirements. A model (chemical model/hydrodynamic model) was developed to determine dumping conditions. This model was then applied on two defined scenarios (landfill surface, effective rainfalls...) in order to study the sulphate concentrations in aquifer system immediately downstream from the storage facility. Results allow us to determine in which conditions the sulphates concentrations are compatibles with the potentially drinkable character of the groundwater. They more specifically concern the nature of the waste disposed of, the efficient rainfalls and the landfill area.

Evaluation of phytotoxicity of seaport sediments aged artificially by rotary leaching in the framework of a quarry deposit scenario.

In the framework of an ecological risk assessment of seaport sediments for terrestrial ecosystems when deposited in quarries, we simulated the "ageing" of sediments exposed to rain. This experiment highlighted an inflection point at the solid/liquid ratio 1/25, after which the extraction of pollutants increases moderately. The raw sediments studied inhibited the germination of Lolium perenne and Armeria maritima (a halophytic species) seeds. Furthermore, they affected the early development of L.perenne. The same sediments, leached at a ratio of 1/25, presented a reduction of acute (germination) and chronic (growth) phytotoxicity. The bioconcentration factors of the metals studied decreased with the leached sediment, except for Cu which was still clearly identified in root parts. Thus rotary leaching tests and phytotoxicity bioassays can be used to provide an initial assessment of the ability of plants, particularly halophytes, to colonize deposits of dredged seaport sediments.

Assessment of sediment ecotoxicity and genotoxicity in freshwater laboratory microcosms.

One possible fate of dredged sediments is disposal in a submerged gravel pit, but this practice may be a source of contamination of the aquatic environment. In an attempt to assess the risks for the aquatic ecosystem, a microcosm test was conducted in the laboratory on three sediments of channel sections to be dredged. After a 3-day period of stabilization, pelagic organisms (microalgae, daphnids, duckweeds, pond snails) and benthic organisms (amphipods, chironomids) were introduced into microcosms. Survival and growth of organisms were monitored during 28 days. Genetic damage was measured weekly in pond snail hemocytes through the comet assay. The sediments contained high levels of metals (up to 740 mg copper/kg and 1220 mg zinc/kg), but were moderately contaminated by PAHs (total PAH content < 10 mg/kg) and PCBs (total PCB content < 0.6 mg/kg). Only moderate effects on the biota were observed, except for genetic damage on pond snail hemocytes which was significant in all microcosms. The absence of pronounced toxic effects on organisms was not expected since concentrations of some sediment toxicants were above threshold values reported in the literature, especially for metals in two sediments, and for PAHs in the three sediments. Speciation, influence of organic matter and presence of sulfides might explain the low toxicity observed. By contrast, assessment of DNA damage revealed to be more sensitive and enabled a ranking of sediments coherent with their toxic load. In the present work, the microcosm protocol previously set up with a formulated sediment appears to be fitted to natural sediments.