7-Ethoxyresorufin-O-deethylase (EROD), benzo[a]pyrene hydroxylase (BaPH), and cytochromes P-450 (cyt-P450) and b(s) (cyt-b(s),) varied annually in winter flounder (Pleuronectes americanus) collected in August of 1987, 1988, and 1989 from a coal tar contaminated estuary (Sydney, Nova Scotia, Canada). For August 1989, with fish available from all estuary areas, these indices correlated strongly with a spatial (along estuary) gradient in PAH in bottom sediments (7.19 +/- 6.59-191 +/- 184 mu g g dry weight(-1)). Mean EROD activities in flounder near the coal tar source were up to seven times those in other estuary areas and paralleled sediment PAH loadings; however, standard deviations were high. Correlations for all MFO indices and sediment PAH were obtained in female flounder (P < 0.01: EROD, cyt-b(s), cyt-P450; P < 0.02: BaPH). For male flounder the trend was similar, but only cyt-P450 correlated with sediment PAH (P < 0.017). BaPH activity was highest near the coal tar source but was more variable and less sensitive to pollutant levels than EROD activity. Somatic indices in fish from Sydney estuary and St. George's Bay were similar. Winter flounder are vulnerable to PAH-induced MFO activities from coal tar contaminated sediments, but MFO induction does not occur equally in all fish; single-season or single-year data must be interpreted with caution.

Les stations d'épuration d'eaux résiduaires sont une des étapes du cycle du sélénium dans l'environnement et contribuent à sa redistribution dans le milieu naturel. Très peu étudié jusqu'à présent dans ces milieux, le sélénium n'en est pas moins un élément très important du point de vue écotoxicologique, sa teneur dans les boues de stations d'épuration destinées à l'épandage agricole faisant par ailleurs l'objet d'une norme. Nous avons mis au point des techniques permettant la détermination spécifique de l'élément total dans ce type d'échantillon, par minéralisation classique ou assistée par micro-ondes et dosage par Voltamétrie de Redissolution Cathodique Différentielle Pulsée (DPCSV) et Spectrométrie d'Absorption Atomique ElectroThermique (ETAAS). Le contrôle qualité a été effectué sur deux échantillons certifiés fournis par le Bureau Communautaire de Référence (BCR) : la boue CRM 145 R et la boue CRM 007. Cependant, lorsqu'on parle de risque toxicologique, il est important de s'intéresser à la détermination des différentes formes sous lesquelles cet élément peut être présent. Nous avons pour cela réalisé des extractions parallèles (spéciation de phases) du sélénium contenu dans les boues afin de déterminer quel pourcentage du sélénium total est réellement et potentiellement disponible pour les végétaux lors d'un épandage sur sol agricole. La spéciation d'espèces a été brièvement abordée dans le but de déterminer les teneurs en Se(IV) et Se(VI), espèces les plus toxiques.

The determination of total selenium by ETAAS in complex matrices such as sewage sludge has always been a challenge owing to the problems encountered with the solubilization of selenium species and the interferences observed during their determination. The use of a microwave oven in order to shorten the digestion step can lead to the solubilization of larger amounts of elements that can behave as interferents in the determination of Se by ETAAS. This study has shown the particular influence of Fe on the determination of Se by ETAAS. A correction procedure was developed and applied successfully to different digested samples of sewage sludge.

Many studies have been devoted to the fate of heavy metals in waste water treatment plants and their impact on the environment. Some elements, such as selenium and tin, have more complex chemical properties. They can form organic compounds, be metabolized and transformed. Their behaviour in sewage treatment works is still almost unknown, although norms exist on due to their potential high toxicity for living organisms. Our study concerns natural samples from French representative sewage treatment plants. The analytical methods developed for the speciation of Se (phase and species speciation) and Sn (species speciation) in that kind of medium have been checked by the use of two different analytical techniques and certified samples from the BCR.

Selenium is both essential and toxic for living organisms (including human beings) in a relatively narrow range and at trace level. Its presence in sewage sludge can be positive in the case of land application when concentrations are relatively low, but can also lead to a Long-term hazard to plants, water resources, animals, and human beings.We have then developed a method for the wet digestion of sewage sludge and the determination of their total selenium concentration by DPCSV and ETAAS. Quality assurance was made by the analysis of two BCR certified sewage sludge reference materials (CRM 145R and CRM 007) and tested on a natural sample from a representative French sewage treatment plant.However, knowledge of speciation is necessary when speaking of the toxicological risk represented by an element. Different techniques of soft extraction, applied to CRM 007 and respecting species distribution, are discussed.

Liver microsomes were prepared from parr and smolt of Atlantic salmon (Salmo salar), and optimal assay conditions (pH, temperature, incubation time) were established to measure basal activities, and kinetic constants (Km, Vmax) of three CYP1A-dependent mixed function oxygenases—benzo-a-pyrene hydroxylase (BAPH), 7-ethoxyresorufin-O-deethylase (EROD), and ethoxycoumarin-O-deethylase (ECOD), cytochromes P-450 and b5 content, and NADH- and NADPH-cytochrome c reductase activities. Using the determined assay conditions, we measured basal MFO activities in parr and smolt over a one-year period. Mean basal activities were as follows: EROD 0.033–0.104 nmol min−1 mg−1, BAPH 0.022–0.223 nmol min−1 mg−1, cyt-P450 0.063–0.353 nmol mg−1, NADH-cyt c reductase 45.25–71.99 nmol min−1 mg−1, NADPH-cyt c reductase 34.01–46.27 nmol min−1 mg−1, cyt-b5 0.079–0.587 nmol mg−1. There was a consistent development-related shift in basal EROD and BAPH activities in Atlantic salmon juveniles as they proceeded through smoltification.

The transport of atrazine in the surface or underground water bodies has been the object of important work devoted to the unsaturated zone and to the kinetic aspects of these phenomena (Brusseau, 1989; Weber, 1991). However, results do not allow a full explanation of atrazine concentrations found in natural water bodies. In order to account for atrazine concentrations as measured in natural aqueous systems, two phenomena are often referred to: biodegradation and adsorption. Recent studies pointed out that biodegradation had a negligible effect. The present report summarizes results found for two major aquifer formations of the Parisian region (Senonian chalkstone and Champigny limestone) which show that for atrazine and for the kind of formation studied adsorption-desorption phenomena in the saturated zone have a negligible effect as well. The authors consider that future work on this topic should be devoted to the assessment of adsorption-desorption kinetic rates in biofilms, poorly crystallized phases and oxide and oxy-hydroxide surfaces.

Parr of Atlantic salmon Salmo salar were exposed to two sublethal flow-through concentrations (averaging 0.2 and 1.0 mg/L) of Hibernia oil-water mixture for up to 40 d to determine relative importance of loss of feeding and food conversion for this juvenile life stage. Oiled parr showed reduced growth for 14 d before growth rates approached those of controls. There were also more weight-losing parr in oiled groups than in control groups. Reduction in growth coincided with reduced food conversion efficiency rather than reduced food intake. Food conversion efficiency was lowest for parr experiencing the higher oil exposure. Net efficiencies in both oiled groups returned to control levels within 2 to 3 weeks, although overall efficiencies in oiled groups lagged behind the control group. Liver glycogen levels were generally lower in oil-exposed parr, whereas liver protein content and the liver-somatic index were higher in parr exposed to the highest concentration of oil. Energy reserves were lower in parr that lost weight during the experiment in comparison with weight-gaining parr. Results suggest that medium-term (2 weeks to 1 month) exposure to low concentrations of oil may have-transitory effects on Atlantic salmon parr, but that chronic oiling may impair growth and may influence the timing of length-dependent smoltification.

Dibenzothiophene (DBT) and related methylated derivatives are known to be among the most persistent and probably the most toxic PAH in the marine environment. Their analysis and their fate by photo-oxidation and biodegradation were studied. The methylated DBT isomers, provided that they are resolved by high resolution GC, were used as organic markers of oil pollution in oysters. The determination of the relative distribution of the four monomethyl DBT allowed to characterize the source of pollution in an oyster-area in the North Brittany (France). The fate of methylated DBT compounds was studied in a controlled sea-water enclosure where Arabian light oil was spilled. Analysis of the weathered oil showed that: (i) oil was degraded by photo-oxidation at a rate of 0.004% day; (ii) the half-lives of photolysis of methylated DBT was dependent upon the number of methyl groups on the aromatic nucleus: 8 days for DBT, 20 days for methyl-1 DBT and more than 2 years for trimethylated DBT. Compounds solubilized in the water column were identified as methyl-substituted dibenzothiophene sulfoxides and sulfones by HPLC with synchrofluorescence and GC-flame photometric detection. The metabolic pathway of DBT was established in vitro. Rat microsomes transformed this substrate to DBT-5-oxide and subsequently to DBT-5-dioxide. Such an enzymatic S-oxidation was shown to be principally Cytochrome-P-450 dependent. It is suggested that the mixed-function oxidase (MFO) activity of marine species could be evaluated by this S-oxidation test in addition to the usual aryl hydrocarbon hydroxylase.

Dibenzothiophene (DBT) was used as a model substrate of hepatic microsomal mixed-function oxidases. Liver microsomes from Aroclor-induced rats oxidatively transformed this substrate to DBT-5-oxide and subsequently to DBT-5-dioxide. These metabolites were identified by mass spectrometry after incubation of perdeuterated DBT. A simple and fast h.p.l.c. method for determination of the metabolites using u.v. detection at 225 nm is described. Optimal reaction conditions were determined. The apparent Km and the Vmax were, respectively, 85 microM and 8.25 nmol of DBT-5-oxide/min per mg protein. The effects of the inducers phenobarbitone, 3-methylcholanthrene and DBT itself on hepatic DBT-metabolizing activity in rats were determined. DBT, an important constituent of petroleum products, might serve as a useful substrate of aromatic hydrocarbon mono-oxygenase.

Analytical methods are described for identification and monitoring of the oxygenated metabolites of dibenzothiophene. Since such compounds are thermolabile, GC analysis is seen to be hardly feasible with conventional injectors such as all-glass moving needle or splitless injectors. Only on-column injection gives no degradation products. In addition, reversed-phase HPLC is particularly suitable for the analysis of the sulfone or sulfoxides of dibenzothiophenes.