La gestion de la qualité des connaissances intégrée à l'évaluation écotoxicologique des sols contaminés

Les méthodes d'évaluation -- Les outils écotoxicologiques -- Théorie de la gestion des incertitudes -- Évaluation des incertitudes dans une procédure d'évaluation écotoxicologique -- Gestion de la qualité des connaissances dans une procédure d'évaluation écotoxicologique -- Modèle d'aide à la décision pour l'évaluation écotoxicologique de sols contaminés -- Éré de sols contaminés par des substances énergétiques -- cas du 2,4,6- trinitrotoluène -- Validation du modèle d'aide à la décision

Assessment of soil quality using bioaccessibility-based models and a biomarker index

Bioavailability in heterogeneous media such as soils is a multi-factorial concept which ranges from soil chemistry to toxicity. The complexity of this factor has been tackled by various studies pinpointing its relevancy for laboratory to field extrapolation of toxicity data. As contaminant bioavailability on these sites is virtually unknown, a global assessment of this issue has been conducted on soils impacted by antitank firing from a Canadian Range and Training Area (RTA) and contaminated by energetic materials (EM) and metals. Yet, the descriptive results acquired from this survey require further in-depth analysis so as to enhance understanding of soil health status. Statistical models as well as an index integrating biomarker responses were derived from this database and are proposed as diagnostic, explanatory and possibly predictive tools for soil bioavailability and quality assessment. Relationships associating bioaccessible contaminant levels to soil properties allowed to clarify contaminant behaviour in energetic material (EM)-contaminated soils. Likewise, models expressing biomarker responses as a function of bioaccessible contaminant concentrations contributed to identify the contaminants causing toxicity in earthworms and to the comprehension of those toxic effects. The index of biomarker response was adapted from similar concepts applied in the aquatic environment and is an original contribution to terrestrial sites. The biomarker index data were in agreement with soil contamination profiles and represent therefore an interesting tool for soil quality appraisal. Such tools also offer a promising potential for the management of contaminated soils.Peer reviewed: YesNRC publication: Ye

Toxic effect of single walled carbon nanotubes combined with cadmium to the crustacean Daphnia magna

The aim of this study was to assess the impact of single-walled carbon nanotubes (SWCNT) on the toxicity of cadmium (Cd) using the crustacean Daphnia magna. LC50 of Cd and SWCNT alone and combined were calculated and compared. Sorption of Cd on SWCNT was also quantified in separate batch experiments. Results showed that the maximum adsorption of Cd onto SWCNT calculated by the Langmuir equation was 24.4 mg kg-1. LC50s for Cd and SWCNT alone were 252.3 µg L-1 and 1400 µg L-1, respectively. In the presence of 500 and 1000 µg L-1 of SWCNT, Cd LC50s were 127.2 and 120.1 µg L-1 respectively. Therefore, Cd toxicity increased when organisms were exposed to both contaminants which indicated that SWCNT induces a synergistic toxic effect on the survival of D. magna. It appears that even if SWCNT had a low adsorption capacity for Cd, toxicity of the metal can be increased. Our study shows the complexity of SWCNT toxicity and how the understanding of their interactions with other contaminants is crucial to determine the consequences of their release into the environment

Acute toxicity of bismuth to the earthworm Eisenia andrei

ABSTRACT: Bismuth (Bi) is increasingly used in several industrial applications including the production of alloys, drugs, cosmetics and munitions formulations. However, little information is available on the environmental fate and ecotoxicological effects of Bi. The present study describes 14 days acute toxicity of Bi, added as Bi citrate to a natural sandy soil, to the adult earthworm Eisenia andrei. Total measured Bi concentrations were 298.0, 399.5, 431.0, and 469.5 mg Bi/kg dry soil. Data indicates that Bi was toxic to Eisenia andrei, as determined by LC50 and LOEC, i.e., 416.0 and 399.5 mg Bi/kg dry soil, respectively. At 14 days in the presence of Eisenia andrei the bioaccessible fraction of Bi in soil, as determined in KNO3 aqueous soil extracts, increased by a factor ranging from 1.6 to 30.0 compared to those measured at the beginning of experiment. Moreover, this study shows that an increase in pH caused by the presence of earthworm in soil was accompanied by increase in Bi bioaccessibility and consequently toxicity. For example, when Bi bioaccessibility increased from 0.262 to 7.516 mg Bi/kg dry soil, the mortality rate increased from 0 to 79%. Assuming that there were at least two routes by which Eisania andrei enhanced Bi bioaccessibility; one route was guided by the mobility, the biochemical (mucus) and the biological (bacteria) interactions of Eisenia andrei with soil constituents, and the other route was marked by the death of earthworms and the release of the accumulated Bi from the carcass

Fine-Scale Mapping of the 4q24 Locus Identifies Two Independent Loci Associated with Breast Cancer Risk

Background: A recent association study identified a common variant (rs9790517) at 4q24 to be associated with breast cancer risk. Independent association signals and potential functional variants in this locus have not been explored. Methods: We conducted a fine-mapping analysis in 55,540 breast cancer cases and 51,168 controls from the Breast Cancer Association Consortium. Results: Conditional analyses identified two independent association signals among women of European ancestry, represented by rs9790517 [conditional P = 2.51 × 10−4; OR, 1.04; 95% confidence interval (CI), 1.02–1.07] and rs77928427 (P = 1.86 × 10−4; OR, 1.04; 95% CI, 1.02–1.07). Functional annotation using data from the Encyclopedia of DNA Elements (ENCODE) project revealed two putative functional variants, rs62331150 and rs73838678 in linkage disequilibrium (LD) with rs9790517 (r2 ≥ 0.90) residing in the active promoter or enhancer, respectively, of the nearest gene, TET2. Both variants are located in DNase I hypersensitivity and transcription factor–binding sites. Using data from both The Cancer Genome Atlas (TCGA) and Molecular Taxonomy of Breast Cancer International Consortium (METABRIC), we showed that rs62331150 was associated with level of expression of TET2 in breast normal and tumor tissue. Conclusion: Our study identified two independent association signals at 4q24 in relation to breast cancer risk and suggested that observed association in this locus may be mediated through the regulation of TET2. Impact: Fine-mapping study with large sample size warranted for identification of independent loci for breast cancer risk

Single-walled carbon nanotubes toxicity to the freshwater amphipod Hyalella azteca: influence of sediment and exposure duration

Carbon nanomaterials are present in various industrial applications and therefore their release into the environment including freshwater ecosystem is expected to increase. The aim of the present study was to investigate the influence of several parameters on the toxicity of single-walled carbon nanotubes (SWCNT) to the freshwater amphipod, <em>Hyalella</em> <em>azteca</em>. The effect of period of exposure, sediment presence and possible impurities released during SWCNT preparation on survival and/or growth of such organism was evaluated. We measured a reduction of survival at concentrations ranging from 10 to 40 mg/L after 96-h exposure, while no mortality was observed with the same concentrations and in the presence of artificial sediment after 14 days of exposure. It is possible that SWCNT are adsorbed on the organic matter from the artificial sediment leading to a decrease of SWCNT bioavailability. The survival and growth toxicity tests revealed a stronger effect at 28 days compared to the 14 days of exposure, and full mortality of organisms at 1000 mg/L for both exposure times. The presence of SWCNT in the gut of survived organisms was observed. The present study demonstrates that the interaction with sediment should be considered when carbon nanotubes toxicity through water exposure is investigated

Immunotoxicity and genotoxicity of single-walled carbon nanotubes co-exposed with cadmium in the freshwater mussel, Elliptio complanata

International audiencePotential immunotoxicity and genotoxicity of as-produced and purified single walled carbon nanotubes (SWCNT, 500 μg L-¹) with or without cadmium (20 μg L-¹) was investigated in hemocytes of the freshwater mussel, Elliptio complanata. Our results showed a decrease in hemocyte viability after 3, and 8 days of exposure and an increase of hemocyte phagocytic efficiency for organisms exposed to Cd. No modification of the cyclo-oxygenase (COX) activity was measured. An increase in DNA damage was measured after 1 day of exposure to Cd and a potentiating effect of combined exposures was observed

Life cycle assessment of kraft lignin for polymer applications

Purpose: Lignin is a by-product of wood pulping that is normally used as fuel on-site (black liquor), but also has some applications in the field of new biomaterials. This study focuses on the life cycle inventory of lignin originating from the kraft pulping process, for polymer applications. The system boundary includes lignin precipitation from black liquor, washing, and drying, but excludes subsequent application-specific compatibilization modifications. Lignin transportation is considered to rely exclusively on trucking. Methods: This work is based on the ecoinvent v2.2 database and the IMPACT 2002+ impact assessment method. Special attention is given to the net effect of lignin precipitation on the mass and energy balances of the kraft process. Because the kraft black liquor supply will far exceed the demand for non-fuel uses for the foreseeable future, it is considered appropriate to use either the marginal variation method of physical allocation or a system boundary expansion. Consequently, the system boundary includes natural gas as a substitute fuel (when applicable) but excludes wood harvesting and the pulping process. Results and discussion: The main impacts of kraft lignin come from the natural gas subsystem (fuel substitution and drying) despite a significantly cleaner combustion than for black liquor. Other significant contributors include the production of carbon dioxide for precipitation, sulfuric acid for washing, and sodium hydroxide to make up for sodium losses, all of which have some improvement potential. Conclusions: The environmental profile of kraft lignin tends to be preferable to synthetic organic compounds of similar molecular complexity because its initial transformation chain is relatively energy efficient. It is thus an environmentally sound choice for polymer applications as long as nearunity substitution ratios can be achieved without requiring compatibilization modifications that are too environmentally intensive and without affecting other stages of the product life cycle. In particular, the end-of-life performance depends on long-term lignin sequestration.Peer reviewed: YesNRC publication: Ye

Rapid isocratic HPLC quantification of metallothionein-like proteins as biomarkers for cadmium exposure in the earthworm Eisenia andrei

Metallothioneins (MTs) are regarded as sensitive biomarkers of cadmium (Cd) exposure in a number of organisms. An isocratic high-performance liquid chromatography (HPLC) method using the fluorophore ammonium-7-fluorobenz-2-oxa-1,3-diazole-4-sulfonate (SBD-F) and UV detection was developed for the quantification of MT-like proteins (MTLPs) in earthworm. This method was developed using a rabbit MT (MT-1) standard, and optimized concentrations of reagents including EDTA, SBD-F, and tris(2-carboxyethyl)phosphine (TCEP). The fluoro-tagged MT-1 (SBD-MT) and MTLP (SBD-MTLP) co-eluted at 7.2\ufffd7.3 min retention time on HPLC chromatograms. The optimized method was applied to quantify MTLPs in earthworms exposed to increasing concentrations of Cd (0, 2.7, 26.7, and 267.5 ?g g-1 of wet artificial soil) for 1\ufffd4 weeks. The amounts of MTLPs increased significantly in a dose- and time-dependent manner except in controls and in earthworms exposed to the lowest concentration of Cd. Since earthworm MTLPs are temporal- and dose-responsive to Cd exposure, they can be used as biomarkers to assess the impact of Cd contamination in soils. The method appeared to be rapid, sensitive, and suitable for direct quantification of total earthworm MTs.NRC publication: Ye

Bioavailability and chronic toxicity of bismuth citrate to earthworm Eisenia andrei exposed to natural sandy soil

International audienceThe present study describes bioavailability and chronic effects of bismuth to earthworms Eisenia andrei using OECD reproduction test. Adult earthworms were exposed to natural sandy soil contaminated artificially by bismuth citrate. Average total concentrations of bismuth in soil recovered by HNO3 digestion ranged from 75 to 289mg/kg. Results indicate that bismuth decreased significantly all reproduction parameters of Eisenia andrei at concentrations ≥ 116mg/kg. However, number of hatched cocoons and number of juveniles seem to be more sensitive than total number of cocoons, as determined by IC50; i.e., 182, 123 and > 289mg/kg, respectively. Bismuth did not affect Eisenia andrei growth and survival, and had little effect on phagocytic efficiency of coelomocytes. The low immunotoxicity effect might be explained by the involvement of other mechanisms i.e. bismuth sequestered by metal-binding compounds. After 28 days of exposure bismuth concentrations in earthworms tissue increased with increasing bismuth concentrations in soil reaching a stationary state of 21.37mg/kg dry tissue for 243mg Bi/kg dry soil total content. Data indicate also that after 56 days of incubation the average fractions of bismuth available extracted by KNO3 aqueous solution in soil without earthworms varied from 0.0051 to 0.0229mg/kg, while in soil with earthworms bismuth concentration ranged between 0.310-1.347mg/kg dry soil. We presume that mucus and chelating agents produced by earthworms and by soil or/and earthworm gut microorganisms could explain this enhancement, as well as the role of dermal and ingestion routes of earthworms uptake to soil contaminant