Trace metal speciation and fluxes within a major French wastewater treatment plant: impact of the successive treatments stages

Seven metals (Cd, Co, Cr, Cu, Fe, Ni and Pb) were monitored at the Seine-Aval wastewater treatment plant during 6 sampling campaigns in April 2004. Particulate and dissolved metals have been measured in 24 h composite samples at each treatment stage (primary settling, secondary activated sludge and tertiary flocculation by FeCl₃). In addition, the diffusive gradient in thin film technique (DGT) was used to determine the dissolved inert and labile metal fraction. Although all treatment stages were able to decrease particulate metals concentrations in wastewater, most dissolved metals concentrations were mainly affected during primary settling. This unexpected result was attributed to tertiary sludge filtrate recirculation. Metals added via the FeCl₃ reagent at the tertiary treatment were shown to lower the overall Cr removal from wastewater and to enrich Ni in effluents. The plant operating conditions (recirculation and reagent addition) appear therefore as important as treatment processes for the metals removal. Total metal fluxes were highly decreased by the whole treatment plant for Cd, Cr, Cu and Pb and to a lesser extend for Co and Ni. However, the labile metal fluxes were poorly decreased for Cu (18%), not significantly decreased for Ni and increased for Fe. The labile fraction of Cd, Co and Cr was not detectable at any stage of the plant. Discharged labile fluxes, at least for Ni, were potentially significant compared to the labile metal fluxes in the river measured downstream the plant. Treated urban wastewater discharges should be carefully considered as a possible source of bioavailable trace metals.     

Organochlorine and organophosphorous pesticide residues in the Ouémé River catchment in the Republic of Bénin

The Ouémé River is one of the most important rivers in the Republic of Bénin. It is 510 km long and its catchment drains 75% of the country. In this study, organochlorine and organophosphorous pesticide residues were measured in more than 35 sediment samples collected on nine locations along the Ouémé River from upstream to downstream. Except for one location, Tanéka-Koko, all areas were contaminated by more than 20 pesticides. Organochlorine pesticides identified in sediment samples included pp'-DDE, op'-DDD, pp'-DDD, op'-DDT, pp'-DDT, alpha-endosulfan, beta-endosulfan, endosulfan sulphate, alpha-HCH, beta-HCH, lindane, aldrin, dieldrin, endrin, telodrin, isodrin, cis- and trans-heptachlorepoxide, hexachlorbutadiene, hexachlorobenzene and octachlorostyrene. The organophosphorous pesticide chlorpyrifos, used in a new formulation to protect cotton, was also identified. In some areas, the concentrations of organochlorine pesticides in the sediment of the Ouémé River exceeded environmental quality standards and are reason for concern.     

Contamination of fish by organochlorine pesticide residues in the Ouémé River catchment in the Republic of Bénin

In the Republic of Bénin, aquatic ecosystems are subject to poisoning risks due to the inappropriate use of pesticides, such as washing of empty bottles in rivers and using pesticides to catch fish. In some areas, cotton fields are located near riverbanks, increasing the probability of pesticide emission to the river. To assess contamination levels in the Ouémé River catchment area, different fish species were collected from different geographical areas along the river. DDT, its metabolites and isomers were the most frequently identified pesticides in fish flesh, alpha-endosulfan, beta-endosulfan, dieldrin, telodrin, lindane and octachlorostyrene were also detected. Concentrations of pesticide residues in fish ranged from 0 to 1364 ng/g lipid. A preliminary risk assessment indicated that the daily intake of chlorinated pesticides by people consuming fish from the Ouémé River still is rather low and does not present an immediate risk.     

Polybrominated diphenyl ethers (PBDEs) in mussels from selected French coastal sites: 1981-2003

The present study focused on the retrospective analysis of PBDEs in archived blue mussel (Mytilus edulis or Mytilus galloprovincialis) samples collected over the past 22 years (1981-2003) from coastal areas of France. We have found that PBDE levels in mussels from the English Channel increased markedly from 1981 to 1991-1995, doubling approximately every 5-6 years followed by a levelling off and a possible beginning of a decrease. The rate of the decline of hexa- and hepta-BDE congeners was more rapid than the decline of tetra- and penta-BDEs in these mussel samples. The difference in the course of time of lower and higher brominated PBDE concentrations suggests that the congener profile in the mussel samples changes over time. The increase in PBDE concentrations in the mussel samples contrasts with a concomitant constant decrease of chlorobiphenyls (CBs) in the same set of samples. However, pulse inputs of both groups of organohalogen compounds were determined for the mussel samples collected at the mouth of the Seine estuary and were probably related to riverine inundations and a flushing out of the deposited sediments from the internal estuary into the bay of the River Seine, as well as considerable dredging activities taking place during same years. In France, the highest PBDE concentrations were determined in the mussels from the English Channel, more precisely in the bay of the Seine, and the regional differences in PBDE levels were mainly connected to the difference in anthropogenic urban and industrial environmental pressures. Published data comparing PBDE levels in mussels have shown significant differences in concentrations between North/South America and Europe. This observation further confirms that the PBDE levels in the North American environment are higher than in Europe. However, the data used for this comparison of mussel contamination by PBDEs is still relatively sparse.     

Biomarker responses in European eel (Anguilla anguilla) exposed to persistent organic pollutants. A field study in the Vaccarès lagoon (Camargue, France)

A screening of relevant biomarkers was carried out in order to evaluate metabolic and cellular damages in European eels exposed to a non-point source contamination by persistent organic pollutants (POP) such as polycyclic aromatic hydrocarbons (PAH) and organochlorine compounds (OC) in a protected area, the Nature Reserve of Camargue (France). Investigations were focused on metabolic responses including detoxification mechanisms (biotransformation, antioxidant process), energy requirements and enzymatic membrane markers either involved in neuronal conduction (acetylcholinesterase, AChE) or in osmoregulation and energy metabolism (ATPases). The hepatic and muscular glycogen rates seemed to be suitable biomarkers as well as three hepatic activities involved in the protection against oxyradicals: catalase, glutathione peroxidase (SeGPx) and superoxide dismutases (SOD). The muscle and gill ATPases as well as the muscle and brain AChE showed more significant relevance in terms of biomarkers than the biotransformation enzymes: ethoxyresorufine-O-deethylase (EROD) and uridine diphospho-glucuronyl transferase (UDPGT). However, most of these enzymatic activities depend on numerous abiotic factors, which must be taken into account in such a biomarker assessment approach. Our study provides some conclusive elements to approve the use in situ of biomarkers developed from laboratory studies. It also raises a question regarding the location of contaminant impregnation in fish organ, in relation with age, development status or mode of contamination, and its influence on biomarker response. If the relevance of membrane indicators is confirmed, this study provides an original statement of the extent of the ecotoxicological threat for the aquatic species in a protected area, due to the occurrence of POP in the cell membranes.     

Functional recovery of biofilm bacterial communities after copper exposure

Potential of bacterial communities in biofilms to recover after copper exposure was investigated. Biofilms grown outdoor in shallow water on glass dishes were exposed in the laboratory to 0.6, 2.1, 6.8 micromol/l copper amended surface water and a reference and subsequently to un-amended surface water. Transitions of bacterial communities were characterised with denaturing gradient gel electrophoresis (DGGE) and community-level physiological profiles (CLPP). Exposure to 6.8 micromol/l copper provoked distinct changes in DGGE profiles of bacterial consortia, which did not reverse upon copper depuration. Exposure to 2.1 and 6.8 micromol/l copper was found to induce marked changes in CLPP of bacterial communities that proved to be reversible during copper depuration. Furthermore, copper exposure induced the development of copper-tolerance, which was partially lost during depuration. It is concluded that bacterial communities exposed to copper contaminated water for a period of 26 days are capable to restore their metabolic attributes after introduction of unpolluted water in aquaria for 28 days.     

Brain cortical assessment by MRI in fetuses with left congenital diaphragmatic hernia

Objective

To evaluate fetal brain development using MRI (magnetic resonance imaging) in CDH (congenital diaphragmatic hernia).

Methods

52 isolated left CDH and 104 control fetuses were imaged using MRI. Brain morphometry (Biparietal diameter—BPD, brain fronto-occipital diameter—BFOD, third ventricle, posterior ventricles, transcerebellar diameter—TCD, anteroposterior and craniocaudal cerebellar vermis diameter—AP and CC) and cortical structures (bilateral cingulate fissure—CF, insular fissure—IF, insular depth - ID) were compared with controls using Mann–Whitney test.

Results

Median gestational age at MRI (p = 0.95)and the median biparietal diameter (p = 0.737) were comparable. Among morphometric parameters, only the brain fronto-occipital diameter was significantly smaller in CDH (p = 0.001) and the third ventricle was significantly greater in CDH (<0.0001). Among cortical structures, the cingulate and insular fissures were significantly deeper in CDH fetuses (p < 0.0001) as the insular depth ID was smaller in CDH (p < 0.03).

Conclusions

CDH fetuses have a smaller fronto-occipital diameter, reduced insular depth, deeper cingulate and insular fissure, and greater third ventricle width as compared to controls. These findings suggest that left CDH may have an impact on fetal brain development with an overall reduction in brain volume.     

The toxicity of cadmium-copper mixtures on daphnids and microalgae analyzed using the Biotic Ligand Model

For the prediction of metal mixture ecotoxicity, the BLM approach is promising since it evaluates the amount of metals accumulated on the biotic ligand on the basis of water chemistry, i.e., species (major cations) competing with metals, and related toxicity. Based on previous work by Farley et al. (2015) (MMME research project), this study aimed at modeling toxicity of Cd:Cu mixtures (0:1 - 1:1 - 1:0 - 1:2 - 1:3 - 2:1 - 3:1 - 4:1 - 5:1 - 6:1) to the crustacean Daphnia magna(48-h immobilization tests) and the microalga Pseudokirchneriella subcapitata (72-h growth inhibition tests). The 2012 version of the USGS model was chosen, assuming additivity of effects and accumulation of metals on a single site. The assumption that EDTA could contribute to toxicity through metals complexing was also tested, and potential effects due to reduction of ions Ca²⁺ absorption by metals were considered. Modeling started with parameter values of Farley et al. (2015) and some of these parameters were adjusted to fit modeled data on observed data. The results show that toxicity can be correctly predicted for the microalgae and that the hypothesis of additivity is verified. For daphnids, the prediction was roughly correct, but taking into account CuEDTA led to more realistic parameter values close to that reported by Farley et al. (2015). However, It seems that, for daphnids responses, metals interact either antagonistically or synergistically depending on the Cu:Cd ratio. Furthermore, synergy could not be explained by additional effects linked to a reduction of Ca absorption since this reduction, mainly due to Cd, increased inversely to synergy. Finally, the USGS model applied to our data was able to predict Cu:Cd mixture toxicity to microalgae and daphnids, giving rise to estimated EC50s roughly reflecting EC50s calculated from observed toxicity.

     

Prevention or cure? Optimal abatement mix

Environmental Economics and Policy Studies - We develop a model for pollution abatement that distinguishes between prevention and treatment technologies, in order to better understand the optimal...     

Aquatic and terrestrial ecotoxicology considering the soil:water continuum in the Anthropocene context

Environmental Science and Pollution Research -