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C R Janssen

Publications and source records attributed to C R Janssen.

At least 37 records · Page 2Linked to original sources
PubMed2003

Influence of ageing on zinc bioavailability in soils.

Currently, soil quality criteria or soil risk assessments of metals are based on laboratory toxicity tests which are carried out in soils freshly spiked with metal salts. With these data, species sensitivity distributions are fitted, from which hazardous concentrations and predicted no effect concentrations are derived. However, due to long-term processes, called ageing, soil metal availability decreases with time. Here we show that pH is the most important parameter determining the effect of ageing on zinc partitioning in soils, with the effect of ageing becoming more important with increasing pH. Furthermore, zinc bioavailability, expressed as the internal zinc concentrations in red clover (Trifolium pratense) is closely related to pore water zinc concentration. In addition, there is a clear dose-response relationship between the survival of the earthworm Eisenia fetida and the calcium chloride-extracted zinc fraction. These results indicate that zinc partitioning can be used to predict zinc bioavailability to terrestrial organisms. However, the use of spiked soils in toxicity assays can result in an over-estimation of the effects of zinc, especially at a high pH.

Animals↗
PubMed2003

Geo-referencing of probabilistic risk of new chemicals in rivers.

The characterisation of the risk of (new) chemicals to species/communities, when both the exposure/environmental concentration and effects (species sensitivity) are variable and uncertain, is the central issue in Probabilistic Environmental Risk Assessment. The spatial variability is one of the largest components of the total variability. This paper tries to explicitly account for this spatial variability by geo-referencing the exposure, effect and finally probabilistic risk. Geo-referencing makes the risk assessment more refined and realistic. In addition, it is also highlighted that geo-referencing the effects of chemicals (species sensitivity distribution) is still a large unexplored area but has large potential to improve probabilistic ecological risk assessments.

Environmental Exposure↗
PubMed2002

Ecotoxicity of chromium (III) to Eisenia fetida, Enchytraeus albidus, and Folsomia candida.

Despite growing concerns about the potential adverse effects of elevated chromium concentrations in the environment, only a few terrestrial toxicity data are available. Therefore, chronic toxicity of chromium(III) was assessed for Eisenia fetida, Enchytraeus albidus, and Folsomia candida, the three invertebrates for which standard test protocols are available. The 21-day EC(50) for the cocoon production of E. fetida was 892 (679-1110) mg Cr/kg dry weight. Based on the reproduction, a 42-days EC(50) of 637 (355-791) mg Cr/kg dry weight was observed for E. albidus, while for F. candida a 28-day EC(50) of 604 (254-3380) mg Cr/kg dry weight was noted. Although the presented data can be considered a step forward in the assessment of the potential risks of chromium(III) in terrestrial environments, further research is needed to evaluate the influence of soil parameters on the toxicity of chromium and to quantify the effect of aging on bioavailability.

Animals↗
PubMed2002

Mixture toxicity of zinc, cadmium, copper, and lead to the potworm Enchytraeus albidus.

Central composite designs were used to develop surface response relationships for predicting the chronic toxicity of mixtures of zinc, cadmium, copper, and lead to the potworm Enchytraeus albidus. Surface response relationships were obtained for all binary mixtures of zinc, cadmium, copper, and lead as well as for mixtures with all four metals. For the binary mixture of zinc and cadmium, this approach and the toxit unit approach gave similar results. However, with the toxit unit approach no such surface response models can be developed. The experimental results indicated that effect predictions based on the concentration addition model were always higher than those obtained with the independent action model. The observed effect was lower than the effect predicted by the concentration addition model for all metal mixtures. Therefore it can be concluded that the concentration addition model represents a reasonable worst-case scenario for the risk assessment of metal mixtures in terrestrial ecosystems.

Animals↗
PubMed2002

Embryo-larval toxicity tests with the African catfish (Clarias gariepinus): comparative sensitivity of endpoints.

Embryo-larval toxicity tests with the African catfish (Clarias gariepinus) were performed to assess the comparative sensitivity of different endpoints. Measured test responses included embryo and larval survival, hatching, morphological development, and larval growth. Chromium, cadmium, copper, sodium pentachlorphenol (NaPCP), and malathion were used as model toxicants. Hatching was not affected by any of the chemicals tested, and embryo survival was only affected by chromium at > or = 36 mg/L. The growth of larvae was significantly reduced at > or = 11 mg/L Cr, > or = 0.63 mg/L Cu, > or = 0.03 mg/L NaPCP, and > or = 1.25 mg/L malathion. Morphological development of C. gariepinus was affected by all of the toxicants tested. Different types of morphological aberrations were observed, i.e., reduction of pigmentation in fish exposed to cadmium and copper, yolk sac edema in fish exposed to NaPCP and malathion, and deformation of the notochord in fish exposed to chromium and malathion. The sensitivity of the endpoints measured can be summarized as follows: growth > abnormality > larval survival > embryo survival > hatching.

Animals↗
PubMed2002

The effect of lindane on terrestrial invertebrates.

Acute and chronic ecotoxicity tests with lindane were carried out using the soil invertebrates Eisenia fetida, Enchytraeus albidus, and Folsomia candida. To assess the influence of soil type on the bioavailability, these tests were carried out in a standard artificial OECD soil and in sandy and loamy field soil. For each species, differences in lindane toxicity were observed for the three soil types. These differences were, however, not related to the organic matter content. The relative differences in lindane toxicity between the soils was species-specific. These results therefore indicate that the pore-water hypothesis, i.e., the pore-water contaminant fraction being the toxicological bioavailable fraction, is not always applicable for organic substances. NOEC, NEC, as well as EC10 data were subsequently used to calculate hazardous concentrations for 5% of the species; this methodology, aimed at setting environmental quality criteria, is discussed.

Animals↗
PubMed2002

Accumulation and regulation of zinc in Daphnia magna: links with homeostasis and toxicity.

Zinc accumulation in Daphnia magna was investigated, and the results were linked to the previously established optimal concentration range for zinc and D. magna. It was observed that organisms cultured in this optimal range (300-600 microg Zn/L) contained 212 +/- 57 to 254 +/- 79 microg Zn/g dry weight. Lower and higher zinc contents were obtained after acclimation to previously established culture concentrations inducing deficiency and toxicity, respectively. The calculation of bioconcentration factors indicated that zinc was actively regulated, at least up to a concentration of 600 microg Zn/L. Zinc uptake and elimination are rapid processes; major increases and decreases in body content occurred within 1 day. Zinc concentrations in daphnids exposed to 600 microg Zn/L fluctuated with 2- to 3-day intervals, suggesting a role of molting in the regulation and elimination of zinc.

Adaptation, Physiological↗
PubMed2002

Bioavailability of zinc in runoff water from roofing materials.

Corrosion and runoff from zinc-coated materials and outdoor structures is an important source for the dispersion of zinc in the environment. Being part of a large inter-disciplinary research project, this study presents the bioavailability of zinc in runoff water immediately after release from the surface of 15 different commercially available zinc-based materials exposed to the urban environment of Stockholm, Sweden. Runoff water was analysed chemically and evaluated for its possible environmental impact, using both a biosensor test with the bacteria Alcaligenes eutrophus (Biomet) and the conventional 72 h growth inhibition test with the green alga Raphidocelis subcapitata. Chemical speciation modelling revealed that most zinc (94.3-99.9%) was present as the free Zn ion, the most bioavailable speciation form. These findings were confirmed by the results of the biosensor test (Biomet) which indicated that all zinc was indeed bioavailable. Analysis of the ecotoxicity data also suggested that the observed toxic effects were due to the presence of Zn2+ ions. Finally, regression analysis showed that, for this type of runoff samples, the rapid screening biosensor was capable of predicting (a) the total amount of zinc present in the runoff samples (R2 of 0.93-0.98; p < 0.05) and (b) the observed 72 h-EbC50s (R2 of 0.69-0.97; p < 0.05).

Biological Assay↗
PubMed2002

The effect of ageing on the toxicity of zinc for the potworm Enchytraeus albidus.

Different extractable zinc fractions and the ecotoxicity of zinc in Enchytraeus albidus were assessed using freshly spiked artificial soils and spiked soils which had been aged for 8 weeks. Standard artificial Organization for Economic Cooperation and Development (OECD)-soils were aged in four different ways: (1) storing at 20 degrees C; (2) percolation followed by storing at 20 degrees C; (3) alternately heating at 60 degrees C and storing at 20 degrees C; and (4) alternately freezing at -20 degrees C and storing at 20 degrees C. Ageing had no clear influence on the pore water concentration, the water soluble and the calcium chloride extractable fraction of zinc in the artificial soils. Similarly, the 21d LC50 and the 42d EC50(reproduction) for E. albidus were not influenced by the different treatments. This absence of zinc fixation in the artificial soil during ageing was probably due to the use of kaolinite clay in OECD-soil.

Animals↗
PubMed2002

Multi-generation toxicity of zinc, cadmium, copper and lead to the potworm Enchytraeus albidus.

In standard chronic terrestrial toxicity tests with invertebrates, adult organisms are exposed to the contaminants and the number of offspring is quantified. These procedures do not allow the assessment of possible effects on all life stages of the organism, which may lead to an underestimation of the toxicity of the test substance. To evaluate the importance of this issue, the potworm Enchytraeus albidus was exposed to zinc, cadmium, copper and lead for two subsequent generations. Juvenile production was assessed for both generations. Considering the variability of metal toxicity data reported in the literature, it is concluded that the two generation assay did not markedly increase the sensitivity of the standard E. albidus test for the tested metals. Therefore, toxicity data obtained with the proposed test guideline with E. albidus are protective for all life stages.

Animals↗
PubMed2002

Biotic ligand model development predicting Zn toxicity to the alga Pseudokirchneriella subcapitata: possibilities and limitations.

Biotic ligand models have been developed for various metals (e.g. Cu, Ag, Zn) and different aquatic species. These models incorporate the effect of physico-chemical water characteristics (major cations, pH, dissolved organic carbon) on the bioavailability and toxicity of the metal. In this study, the individual effects of calcium, magnesium, potassium, sodium and pH on zinc toxicity to the green alga Pseudokirchneriella subcapitata (formerly and better known as Selenastrum capricornutum and Raphidocelis subcapitata) were investigated. Stability constants for binding to algal cells (K(BL)) were derived for those cations affecting zinc toxicity, using the mathematical approach proposed by De Schamphelaere and Janssen [Environ. Sci. Technol. 63, (2002) 48-54]. Potassium proved to be the only cation tested that did not alter zinc toxicity to algae significantly. Log (K(BL)) values for Ca, Mg and Na, derived at pH 7.5, were 3.2, 3.9 and 2.8, respectively. Toxicity tests performed at different pH values (5.5-8.0) indicated that competition between H(+) and Zn(2+) reduces zinc toxicity. However, the observed relationship between (H(+)) and the 72h-EbC(50) [expressed as microM (Zn(2+))] is not linear and suggests that pH affects the physiology of the biotic ligand. Although, in general, our findings seem to suggest that zinc toxicity to algae can be modelled as a function of key water characteristics, the results also demonstrate that the part of the conventional BLM-hypothesis-i.e. that the binding characteristics of the biotic ligand are independent of the test medium characteristics-is not valid for algae. The observed pH-dependent change of stability constants should therefore be further investigated and incorporated in future BL-modelling efforts with algae.

Chlorophyta↗
PubMed2001

Tolerance changes of the potworm Enchytraeus albidus after long-term exposure to cadmium.

Cadmium tolerance in Enchytraeus albidus was assessed for non-acclimatised organisms, as well as populations acclimatised for 18 months to 32, 100 and 320 mg Cd/kg dry wt. of standard artificial soil. Despite the increased concentration of metallothionein-like proteins in the acclimatised potworms, no changes in sensitivity to acute and chronic (juvenile production) cadmium toxicity could be observed. The 21-day LC50s ranged from 627 for the non-acclimatised enchytraeids to 748 mg Cd/kg dry wt. for the organisms acclimatised for 18 months to a cadmium concentration of 320 mg/kg dry wt. The 42-day EC50s varied from 96.2 (73.6-115) for the organisms acclimatised to 32 mg Cd/kg dry wt. to 234 (186-290) mg Cd/kg dry wt. for those acclimatised to 100 mg Cd/kg dry wt., while the value was intermediate for the non-acclimatised organisms and those acclimatised to the highest cadmium concentration. The elevated content of metallothionein-like proteins apparently only served for the detoxification of the increased cadmium body burdens.

Adaptation, Physiological↗
PubMed2001

Ecotoxicity of zinc in spiked artificial soils versus contaminated field soils.

Metal bioavailability is influenced by soil characteristics and aging period. In the present study, both factors were modeled by comparing metal bioavailability in spiked artificial soil and historically contaminated field soils. The chronic toxicity of zinc to Folsomia candida in spiked artificial soils could be predicted with a model based on pH, cation exchange capacity, and total zinc concentration. However, this model could not adequately predict chronic zinc toxicity in contaminated field soils. Porewater concentration and water- and calcium chloride-extracted zinc fractions of the contaminated field soils were lower than those predicted using models developed for spiked artificial soils, indicating that the effect of aging on metal bioavailability should be taken into account. The reproduction of F. candida in contaminated field soils was lower than predicted with models developed using zinc concentration in the porewater and the water- and calcium chloride-extracted fractions in spiked artificial soils. This suggests that these fractions are not the only bioavailable zinc fractions and that dietary metal exposure might also be an important route of uptake under environmentally relevant conditions. Aging and dietary uptake should be studied urgently in order to be able to perform effect-based risk assessments of metal contaminated soils.

Animals↗
PubMed2001

Runoff rates and ecotoxicity of zinc induced by atmospheric corrosion.

Initiated by regulatory restrictions on the use of zinc for various building and construction applications, together with a lack of knowledge related to the release of zinc induced by atmospheric corrosion, a major interdisciplinary research project was implemented to generate data to be used in future risk assessment. Runoff rates from a large number of commercially available zinc-based materials have been determined on panels inclined 45 degrees from the horizon, facing south, during a 1-year atmospheric exposure in an urban environment in Sweden. Possible environmental effects of runoff water immediately after leaving the surface of the various materials have been evaluated during two different sampling periods of varying season and zinc concentration, using the standard growth inhibition test with algae. Raphidocelis subcapitata (formerly Selenastrum capricornutum). Zinc-specific biosensors with the bacterial strain of Alcaligenes eutrophus, and computer modeling using the water-ligand model MINTEQA2 and the humic aquatic model WHAM, have been used to assess the bioavailability and chemical speciation of zinc in the runoff water. An excellent consistency between the different methods was observed. The results show considerably lower runoff rates of zinc (0.07-3.5 g m(-2) year(-1)) than previously being used for regulatory restrictions, and the concentration of zinc to be predominantly responsible for the observed toxicity of the runoff water towards the green algae. The majority of the released zinc quantity was found to be present as free hydrated zinc ions and, hence, bioavailable. The data do not consider changes in bioavailability and chemical speciation or dilution effects during entry into the environment, and should therefore only be used as an initial assessment of the potential environmental effect of zinc runoff from building applications. This interdisciplinary approach has the potential for studies on the environmental fate of zinc in soil or aquatic systems.

Biological Assay↗
PubMed2001

The use of biomarkers in Daphnia magna toxicity testing V. In vivo alterations in the carbohydrate metabolism of Daphnia magna exposed to sublethal concentrations of mercury and lindane.

Aspects of the carbohydrate metabolism of Daphnia magna exposed for 48 and 96 h to sublethal concentrations of mercury and lindane were investigated. General as well as toxicant-specific perturbations in the intermediary metabolism were observed. Both model toxicants caused an increase in glycolytic and hexose-monophosphate shunt activity. Mercury exposure increased lactate dehydrogenase and isocitrate activity (only after 96 h), while lindane exposure, on the contrary, inhibited the cellular lactate formation and increased the Krebs' cycle activity (only after 48 h). Daphnids exposed to sublethal mercury concentrations clearly exhibited increased glycogenolytic activity, while in lindane-exposed organisms mainly glycogen phosphorylase inhibition was detected. The short-term enzyme-based effect levels (48--96 h LOEC and EC(10) values) were compared with the effects on the population dynamics. This evaluation for both model toxicants suggests that threshold levels (LOEC or EC(10) values) based on pyruvate kinase activity after 48 and 96 h of exposure could be potential early warning signals for long-term effects. A set of enzymatic endpoints, based on the intermediary metabolism, is suggested to characterize the metabolic state of the daphnids.

Animals↗
PubMed2001

Effect of clay and organic matter type on the ecotoxicity of zinc and cadmium to the potworm Enchytraeus albidus.

Clay and organic matter are considered as important parameters influencing bioavailability and ecotoxicity of metals in soils. As there exists a large variation in the type of clay and organic matter in field soils, the quantity of these variables alone may not be good indicators of metal bioavailability. To test this hypothesis, toxicity experiments with the potworm Enchytraeus albidus were conducted in artificial soils with three types of clay and seven types of organic matter, while the soil pH was kept constant. The 14d LC50 of zinc and cadmium varied from 83.0 to 1,140 mg Zn/kg D.W. and from 55.2 to 704 mg Cd/kg D.W., respectively, depending on the type of clay and organic matter that were used. Simultaneous measurements of the cation exchange capacity showed that this soil parameter is a better indicator of the bioavailability as it takes into account the type of clay and organic matter as well as other adsorption phases such as metal oxyhydroxides.

Adsorption↗
PubMed2001

Zinc acclimation and its effect on the zinc tolerance of Raphidocelis subcapitata and Chlorella vulgaris in laboratory experiments.

The effect of zinc acclimation of Raphidocelis subcapitata (syn. Selenastrum capricornutum) and Chlorella vulgaris on their sensitivity towards this metal was examined in a series of laboratory experiments. These two commonly used algal species were acclimated to 65 microg Zn/l and changes in zinc tolerance were monitored using standard growth inhibition tests. The chemically defined ISO medium was used as a control culture medium. Both species demonstrated a maximum increase in zinc tolerance of a factor of 3 after 100 days of acclimation. Shifts in the shape of the concentration-response curve due to acclimation were observed for R. subcapitata. Compared to non-acclimated algae, acclimated R. subcapitata exhibited higher growth rates in all zinc treatments as well as in the controls. This suggests that the use of ISO-medium results in sub-optimal growth due to zinc deficiency. These effects could not be demonstrated for C. vulgaris. The zinc tolerance of both species decreased significantly one week after returning the acclimated algae to control (ISO) medium. 72hEC50 values based on growth rate were two to four times higher than those calculated using biomass measurements. Algal toxicity test results, particularly if used for metal risk assessments, must not be conducted using nutrient deficient media.

Acclimatization↗