Gerard J. Stroomberg

Tenax extraction mimics benthic and terrestrial bioavailability of organic compounds

Biota to sediment accumulation factors (BSAFs) are widely used to describe the potential accumulation of organic contaminants in organisms. From field studies it is known that these BSAFs can vary dramatically between sediments of different origin, which is possibly explained by the variation in bioavailability of organic contaminants in sediments. In the present study it is shown that the variability in BSAF values for different sediment samples obtained at two Dutch freshwater sites could largely be explained by the variation in Tenax-extractable concentrations in these sediments. Variations of a factor of about 50 could be explained. The ratio between concentrations in biota and Tenax-extractable concentrations in sediment varied slightly between sediments and contaminant class, but was close to the theoretically expected value of 2. This is a strong indication that Tenax-extractable concentrations of contaminants in sediments are an excellent indicator of available concentrations.

Pyrene metabolites in the hepatopancreas and gut of the isopod Porcellio scaber, a new biomarker for polycyclic aromatic hydrocarbon exposure in terrestrial ecosystems

The object of this study was to investigate the formation of pyrene metabolites by the isopod Porcellio scaber as a possible tool in the environmental risk assessment of polycyclic aromatic hydrocarbon (PAH) exposure in terrestrial ecosystems. The formation of pyrene metabolites was studied after either pulse exposure to a single high dose, or prolonged exposure (14 d) to a lower dosage. Exposure studies were carried out with unlabeled or radiolabeled pyrene, ion pair chromatography was used for analysis, and reference conjugates were synthesized. We also measured pyrene metabolites in field—exposed animals, to explore their use as biomarkers of PAH exposure. Analysis of the hepatopancreas and gut of single isopods revealed the formation of five products, one of which was 1-hydroxypyrene. Four of the remaining products were identified as phase II metabolites of 1- hydroxypyrene, with UV absorption and fluorescence characteristics similar to that of pyrene. One metabolite was identified as pyrene−1-glucoside, which is in accordance with high rates of glucosidation, reported for these isopods. Another conjugate was identified as pyrene−1-sulfate. None of the metabolites coeluted with a pyrene−1-glucuronide reference obtained from fish bile. A fifth metabolite detected by on—line scintillation detection did not exhibit any absorption at 340 nm, possibly because one of the aromatic rings of pyrene had lost its aromatic character. Although pyrene is not known for its toxicity, it usually co—occurs with other PAHs that are transformed into toxic products. Investigating the metabolism of pyrene can provide information with regard to the biotransformation capacity of invertebrate species and uptake and elimination kinetics. Because pyrene is one of the most predominant PAHs in the environment, analysis of its metabolites provides an extra tool for the environmental risk assessment of ecosystems with regard to PAH exposure, bioavailability, and biotransformation.

Pyrene metabolites in the hepatopancreas and gut of the isopod porcellio scaber, a new biomarker for polycyclic aromatic hydrocarbon exposure in terrestrial ecosystems: Pyrene metabolites in the isopod Porcellio scaber

The object of this study was to investigate the formation of pyrene metabolites by the isopod Porcellio scaber as a possible tool in the environmental risk assessment of polycyclic aromatic hydrocarbon (PAH) exposure in terrestrial ecosystems. The formation of pyrene metabolites was studied after either pulse exposure to a single high dose, or prolonged exposure (14 d) to a lower dosage. Exposure studies were carried out with unlabeled or radiolabeled pyrene, ion pair chromatography was used for analysis, and reference conjugates were synthesized. We also measured pyrene metabolites in field-exposed animals, to explore their use as biomarkers of PAH exposure. Analysis of the hepatopancreas and gut of single isopods revealed the formation of five products, one of which was 1-hydroxypyrene. Four of the remaining products were identified as phase II metabolites of 1- hydroxypyrene, with UV absorption and fluorescence characteristics similar to that of pyrene. One metabolite was identified as pyrene-1-glucoside, which is in accordance with high rates of glucosidation, reported for these isopods. Another conjugate was identified as pyrene-1-sulfate. None of the metabolites coeluted with a pyrene-1-glucuronide reference obtained from fish bile. A fifth metabolite detected by on-line scintillation detection did not exhibit any absorption at 340 nm, possibly because one of the aromatic rings of pyrene had lost its aromatic character. Although pyrene is not known for its toxicity, it usually co-occurs with other PAHs that are transformed into toxic products. Investigating the metabolism of pyrene can provide information with regard to the biotransformation capacity of invertebrate species and uptake and elimination kinetics. Because pyrene is one of the most predominant PAHs in the environment, analysis of its metabolites provides an extra tool for the environmental risk assessment of ecosystems with regard to PAH exposure, bioavailability, and biotransformation.

Laser-induced fluorescence detection at 266 nm in capillary electrophoresis Polycyclic aromatic hydrocarbon metabolites in biota

The separation of five phenolic polycyclic aromatic hydrocarbon metabolites (hydroxy-PAHs) has been performed by cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) using a 30 mM borate buffer (pH 9.0) containing 60 mM sodium dodecyl sulfate and varying concentrations of gamma-cyclodextrin (gamma-CD). A concentration of 12.5 mM gamma-CD was found to provide a baseline separation of the five hydroxy-PAHs. We applied conventional fluorescence and laser-induced fluorescence (LIF) detection, using a new, small-size, quadrupled Nd-YAG laser emitting at 266 nm. The best limits of detection, in the low ng/ml range, were achieved using LIF detection. For all analytes, linearity was observed up to ca. 100 ng/ml. As an application, conjugated pyrene metabolites in hepatopancreas samples from the terrestrial isopods Oniscus asellus and Porcellio scaber were separated and detected. Finally, flatfish bile samples from individuals exposed to polluted sediment or crude oil, which were part of an interlaboratory study, were analyzed by CD-MEKC with conventional fluorescence and LIF detection to determine the 1-hydroxypyrene concentrations.

Metabolism of 1-fluoropyrene and pyrene in marine flatfish and terrestrial isopods

Monofluorinated polycyclic aromatic hydrocarbons (F-PAHs) are useful reference compounds for a broad spectrum of PAH studies. The pyrene metabolite 1-hydroxypyrene is often used as a biomarker of PAH exposure. Two species, isopod (Porcellio scaber) and flatfish (Platichthys flesus), that produce 1-hydroxypyrene as the major intermediary metabolite and have distinct phase-II conjugates, were selected to investigate the cytochrome P450 catalyzed metabolism of 1-fluoropyrene. The fluorine atom blocks one of the four most favored carbon atoms, yielding different metabolite patterns and the results obtained in the selected species were compared with metabolite profiles obtained for unsubstituted pyrene. Charge densities in 1-fluoropyrene measured with (13)C-NMR were used to predict possible positions of hydroxylation, which were confirmed by (19)F-NMR. Additionally, the retention behaviour of conjugated 1-fluoropyrene metabolite isomers in reversed-phase liquid chromatography on a polymeric alkyl-bonded phase was interpreted based on the slot model. Whereas three phase-I metabolites were found in isopod hepatopancreas, only two were observed in flatfish bile. Phase-II metabolism appeared unaffected by the fluorine substituent. It was concluded that the phase-I enzyme cytochrome P450 is non-regioselective in the isopod: the activation is mostly influenced by the electron density distribution. In contrast, the enzymatic oxidation in the flounder is more selective. These differences will affect to what extent pyrene metabolite measurements can be used to assess the impact of PAHs to different species.

Formation of pyrene metabolites by the terrestrial isopod porcellio scaber.

The formation of pyrene metabolites by the temestrial isopod Porcellio scaber (Latr.) was studied following exposure for 13 days to 100 μg/g pyrene in its food. An alkaline hydrolysis method with subsequent liquid-liquid extraction was developed to determine the metabolite content, especially 1-hydroxypyrene. Synchronous Fluorescence Spectroscopy (SFS) was explored as a fast screening method and HPLC was applied as a complementary method for confirmation of the SFS results. In Porcelho scaber the amount of 1-hydroxypyrene exceeded that of pyrene, which indicates that pyrene is being metabolized extensively. SFS and HPLC demonstrated that Porcellio scaber also forms a number of other fluorescent metabolites. These metabolites exhibit fluorescence at the same excitation wavelength as 1-hydroxypyrene, possibly indicating a similar fluorophore structure. Determination of 1-hydroxypyrene is considered as a first step towards an improved environmental risk assessment of PAH exposure, as pyrene is a predominant member of this class of environmental contaminants and 1-hydroxypyrene is its major metabolite.

Environmental risk assessment on aquatic-terrestrial gradients in a freshwater tidal area

Environmental risk assessments are generally performed for either terrestrial or aquatic systems, while these systems sometimes exist in close proximity. The objective of this study is to compare environmental risks along gradients from aquatic to terrestrial conditions. The assessment involved chemical analysis (including bioavailable fractions), as well as bioassays and bioaccumulation experiments using aquatic and terrestrial organisms. The results demonstrate that sediments and soils from neighbouring aquatic and terrestrial systems may render different assessments in terms of environmental risks. Metal availability for oligochaetes appeared to be limited in the aquatic environment as compared to the terrestrial environment, while the reverse was observed for organic contaminants. This paper aims to illustrate the use of various assessment techniques within a framework to compare ecological risks in aquatic and terrestrial environments. The obtained results are useful when considering (a prioritisation of) remedial actions.