Chronic exposure to chlorpyrifos reveals two modes of action in the springtail Folsomia candida

Organophosphates are popular insecticides, but relatively little is known about their chronic effects on ecologically relevant endpoints. In this paper, we examine a life-cycle experiment with the springtail Folsomia candida, exposed via food to chlorpyrifos (CPF). The results for all endpoints (survival, growth and reproduction) were analyzed using the DEBtox model. Growth was unaffected by CPF, even at concentrations causing severe effects on survival and reproduction. Model analysis suggests that CPF directly affects the process of egg production. For the short-term response (45 days), this single mode of action accurately agreed with the data. However, the full data set (120 days) revealed a dose-related decrease in reproduction at low concentrations after prolonged exposure, not covered by the same mechanism. It appears that CPF interacts with senescence by increasing oxidative damage. This assumption fits the data well, but has little consequences for the predicted response at the population level.     

QSAR development and bioavailability determination: The toxicity of chloroanilines to the soil dwelling springtail Folsomia candida

Quantitative structure–activity relationships (QSARs) are an established tool in environmental risk assessment and a valuable alternative to the exhaustive use of test animals under REACH. In this study a QSAR was developed for the toxicity of a series of six chloroanilines to the soil-dwelling collembolan Folsomia candida in standardized natural LUFA2.2 soil. Toxicity endpoints incorporated in the QSAR were the concentrations causing 10% (EC10) and 50% (EC50) reduction in reproduction of F. candida. Toxicity was based on concentrations in interstitial water estimated from nominal concentrations in the soil and published soil–water partition coefficients. Estimated effect concentrations were negatively correlated with the lipophilicity of the compounds. Interstitial water concentrations for both the EC10 and EC50 for four compounds were determined by using solid-phase microextraction (SPME). Measured and estimated concentrations were comparable only for tetra- and pentachloroaniline. With decreasing chlorination the disparity between modelled and actual concentrations increased. Optimisation of the QSAR therefore could not be accomplished, showing the necessity to move from total soil to (bio)available concentration measurements.     

Development of zinc bioavailability and toxicity for the springtail Folsomia candida in an experimentally contaminated field plot

The influence of outdoor exposure conditions and ageing of contamination on the toxicity of zinc was investigated for the springtail Folsomia candida to evaluate the validity of a standardised soil toxicity test. In three successive years, animals were incubated in an experimentally contaminated field plot. During the first months after construction of the test field, total zine concentrations of the soil decreased rapidly due to leaching of excess zinc with rainwater, while increased sorption of the remaining residues resulted in a reduced bioavailability of the metal. Although variation between replicates was substantial, the EC50s for the effect of zinc on reproduction of F. candida determined in the field experiments differed by less than a factor of two from effect concentrations obtained in laboratory tests in which the same soil was used. Expression of the EC50s on the basis of water soluble zinc allowed for a comparison with effect concentrations estimated for other soil types. EC50s were comparable with literature data, which indicates that bioavailability of zinc is the main factor determining toxicity for F. candida. It is concluded that laboratory based toxicity data are suitable to predict effects of zinc for F. candida under outdoor conditions, provided that the bioavailability of zinc is determined accurately using water soluble concentrations.     

Ecotoxicity of nickel to Eisenia fetida, Enchytraeus albidus and Folsomia candida

Despite growing concern about the potential adverse effects of elevated nickel concentrations in the environment, only a few toxicity data are available for terrestrial invertebrates. Therefore, chronic toxicity of nickel was assessed for Eisenia fetida, Enchytraeus albidus and Folsomia candida, the three invertebrates for which standard test protocols are available. The 21 d EC50 for the cocoon production of E. fetida was 362 (241-508) mg Ni/kg dry wt. For the reproduction of E. albidus, a 42 d EC50 of 275 (217-346) mg Ni/kg dry wt was observed. The 28 d EC50 for the reproduction of F. candida was 476 (347-671) mg Ni/kg dry wt. The obtained toxicity data were very similar to those of related species reported in literature. Although the presented data can be considered as a step forward in the assessment of the potential risks of nickel in terrestrial environments, further research is needed to evaluate the influence of soil parameters on the toxicity of nickel and to quantify the effect of ageing on bioavailability.     

Decrease in catalase activity of Folsomia candida fed a Bt rice diet

Here we report the effects of three Bt-rice varieties and their non-Bt conventional isolines on biological traits including survival, reproduction, and the activities of three antioxidant enzymes superoxide dismutase, catalase and peroxidase, in the Collembolan, Folsomia candida. The reproduction was significantly lower when fed Kemingdao and Huahui1 than those feeding on their non-GM near-isogenic varieties Xiushui and Minghui63 respectively, this can be explained by the differences of plant compositions depended on variety of rice. The catalase activity of F. candida was significantly lower when fed the Bt-rice variety Kemingdao compared to the near-isogenic non-Bt-rice variety Xiushui. This suggests that some Bt-rice varieties may impose environmental stress to collembolans. We emphasize that changes in activity of antioxidant enzymes of non-target organisms are important in understanding the ecological consequences for organisms inhabiting transgenic Bt-rice plantations.     

Avoidance tests with Folsomia candida for the assessment of copper contamination in agricultural soils

The feasibility of assessing copper accumulation in agricultural soils using avoidance tests with a Canadian strain of Folsomia candida was investigated under laboratory conditions. The avoidance response to nominal copper sulfate concentrations of 0, 200, 800, 1600 and 3200 mg kg⁻¹ in OECD soil was inconsistent between trials with the standard plastic cup or a modified Petri dish method requiring less soil. However, combined results from three Petri dish trials decreased variability and provided a 75% avoidance level, close to the 80% criterion proposed for avoidance tests. A Copper avoidance EC_50s of 18 mg kg⁻¹was obtained using the Petri dish method whether tests were conducted with or without light. While Petri dish tests have potential as a cheap tool to distinguish metal contaminated soils from uncontaminated soils they would be unsuitable for tracking or quantifying changes in metal concentrations. throughout remediation. Advantages and limitations of the method have been presented.     

Compartmentation and effects of lead (Pb) in the collembolan,Folsomia candida

Environmental Science and Pollution Research - The impact of soil lead (Pb) pollution on survival, growth, and reproduction of the collembolan, Folsomia candida, and Pb compartmentation in its gut...     

Comparative toxicity of a zinc salt, zinc powder and zinc oxide to Eisenia fetida, Enchytraeus albidus and Folsomia candida

The pore water zinc concentration and the calcium chloride extracted zinc fraction are higher in the soils spiked with a zinc salt (ZnCl2) compared to soils spiked with zinc oxide or zinc powder. Based on total zinc concentrations in the soil, the acute toxicity of zinc salt to the compost worm Eisenia fetida, the potworm Enchytraeus albidus and the springtail Folsomia candida was lower compared to zinc oxide and zinc powder. However, when expressed on the basis of pore water concentrations or calcium chloride extracted fractions, acute toxicity was higher for zinc salt, which indicated that dermal uptake via the pore water is not the only route of uptake. Chronic toxicity of zinc salt, zinc oxide and zinc powder was similar when based on total concentrations in the soil which again indicates that the pore water route of uptake is not the only route of exposure but that oral uptake is also important.     

Chronic toxicity of ZnO nanoparticles, non-nano ZnO and ZnCl2 to Folsomia candida (Collembola) in relation to bioavailability in soil

The chronic toxicity of zinc oxide nanoparticles (ZnO-NP) to Folsomia candida was determined in natural soil. To unravel the contribution of particle size and free zinc to NP toxicity, non-nano ZnO and ZnCl₂ were also tested. Zinc concentrations in pore water increased with increasing soil concentrations, with Freundlich sorption constants K_f of 61.7, 106 and 96.4 l/kg (n = 1.50, 1.34 and 0.42) for ZnO-NP, non-nano ZnO and ZnCl₂ respectively. Survival of F. candida was not affected by ZnO-NP and non-nano ZnO at concentrations up to 6400 mg Zn/kg d.w. Reproduction was dose-dependently reduced with 28-d EC50s of 1964, 1591 and 298 mg Zn/kg d.w. for ZnO-NP, non-nano ZnO and ZnCl₂, respectively. The difference in EC50s based on measured pore water concentrations was small (7.94-16.8 mg Zn/l). We conclude that zinc ions released from NP determine the observed toxic effects rather than ZnO particle size.     

Assessing single and joint effects of chemicals on the survival and reproduction of Folsomia candida (Collembola) in soil

Chemicals are often found in the environment as complex mixtures. There has been a large effort in the last decade to assess the combined effect of chemicals, using the conceptual models of Concentration Addition and Independent Action, but also including synergistic, antagonistic, dose-level and dose-ratio dependent deviations from these models. In the present study, single and mixture toxicity of atrazine, dimethoate, lindane, zinc and cadmium were studied in Folsomia candida, assessing survival and reproduction. Different response patterns were observed for the different endpoints and synergistic patterns were observed when pesticides were present. Compared with the previously tested Enchytraeus albidus and Porcellionides pruinosus, the mixture toxicity pattern for F. candida was species specific. The present study highlights the importance of studying toxicity of chemicals mixtures due to the observed potentiation of effects and confirms that for an adequate ecologically relevant risk assessment different organisms and endpoints should be included.     

Mobility of antimony in soil and its availability to plants

In a historical mining area residual material has been filled on land and these locations are used today as agricultural soils or house gardens. The antimony concentrations in these soils are up to 500 mg/kg. Antimony transfer into 19 vegetable and crop species was investigated. In grain and other storage organs up to 0.09 mg Sb/kg were found, whereas maximum antimony concentrations in shoots and leaves were determined to be 0.34 mg Sb/kg and 2.2 mg Sb/kg, respectively. Despite the high antimony contamination of the soils, concentrations in the investigated plants in general corresponded to concentrations only reported for uncontaminated soils. NH4NO3 extraction of some of the soils indicated that the mobile fraction of antimony present was only 0.06-0.59%. In contrast, in leaves of spinach grown under controlled conditions in soils with a high mobile antimony content an accumulation of the element could be observed: a maximum value of 399 mg Sb/kg was detected, and a correlation between the mobile fraction in the soils and antimony in leaves was found.     

Toxicity of 56 substances to trees

Toxicity data of substances to higher plants is needed for the purpose of risk assessment, site evaluation, phytoremediation, and plant protection. However, the results from the most common phytotoxicity tests, like the OECD algae and Lemna test, are not necessarily valid for higher terrestrial plants. The willow tree toxicity test uses inhibition of transpiration (aside of growth and water use efficiency) of willow cuttings grown in spiked solutions or soils as end point to quantify toxicity. This overview presents results from 60 studies including 24 new unpublished experiments for 56 different chemicals or substrates. Highest toxicity (EC₅₀ < 1 mg/L) was observed from exposure to heavy metals like copper and cadmium. Also, organotins and free cyanide showed very high toxicity. The toxic effect of chlorophenols on willows was comparable to that on duck weed (Lemna) and green algae, while volatile compounds like chlorinated solvents or benzene, toluene, ethylbenzene, and xylene had less effect on trees than on these aquatic plants, due to volatilization from leaves and test media. In particular low (g/L range) toxicity was observed for tested nanomaterials. Effects of pharmaceuticals (typically weak acids or bases) depended strongly of the solution pH. Like for algae, baseline toxicity was observed for willows, which is related to the water solubility of the compounds, with absolute chemical activity ranging from 0.01 to 0.1, but with several exceptions. We conclude that the willow tree toxicity test is a robust method for relating uptake, accumulation, and metabolism of substances to the toxicity to trees.     

Toxicity of tributyltin to willow trees

BACKGROUND: Tributyltin is an organotin compound, used as an antifouling agent in ship paint, with heavy impact on the marine environment. Contaminated dredged harbor sludge is now dumped on land. The toxicity of tributyltin (TBT) to trees has not yet been quantified. Eventually, a vegetation cover on the dumped sludge could be established for the purpose of non-food cash crop production and phytoremediation. METHODS: The phytotoxicity of tributyltin chloride (TBTCl) and tributyltin hydride (TBTH) was measured at pH 4 and at pH 7 using the willow tree transpiration test. Different pH levels of the nutrient solutions were achieved by adding ammonium salt (low pH) or nitrate (high pH) as nitrogen source. RESULTS AND DISCUSSION: At low pH (pH 4), all trees showed symptoms of poor health. Transpiration decreased at concentrations above or equal to 0.1 mg TBTCl/l and 1 mg TBTH/L. The TBT toxicity was more pronounced at pH 7. The trees survived even the highest dose of 10 mg/l TBTCl or TBTH, although their growth and transpiration was strongly reduced. CONCLUSION: In contrast to other organisms, TBTCl and TBTH were less toxic to higher plants. RECOMMENDATIONS AND OUTLOOK: The toxicity of TBT is no hindrance for establishing vegetation on TBT-contaminated sludge. Phytoremediation and cash crop production could be possible with suitable plants.     

Toxicity of boron to the duckweed,Spirodella polyrrhiza

Boron is an essential nutrient for plants and the potential exists for efficient removal of this element by wetland treatment systems due to accumulation by plants. To evaluate the efficacy of using Spirodella polyrrhiza to treat boron-contaminated wastewater or to be a suitable species for removing other nutrients from boron-containing wastewater the toxicity of this micronutrient was determined using standard methods. Frond production is apparently a more sensitive endpoint than either growth rate or the presence of abnormal fronds. Frond production in S. polyrrhiza was significantly reduced at 3.55 mg B/l. Significant reductions in growth rate and the percentage of abnormal (chlorotic, necrotic, and dead) fronds were observed at 18.9 and 22.4 mg B/l, respectively. The EC50 for frond production, frond growth rate, and abnormal fronds were 14.3, 11.7, and 17.7 mg B/l, respectively. S. polyrrhiza did not remove significant amounts of boron from the treatment solutions under the conditions and concentrations existing in this study. The inability of S. polyrrhiza to remove even small amounts of boron from the test solutions indicates this species is not suitable for treating boron-containing wastewater, even those with low boron concentrations.     

Evaluation of different amendments to stabilize antimony in mining polluted soils

Soil pollution with antimony is of increasing environmental concern worldwide. Measures for its control and to attenuate the risks posed to the ecosystem are required. In this study the application of several iron and aluminium oxides and oxyhydroxides as soil amendments was evaluated in order to assess their feasibility to stabilize Sb in mining polluted soils. Mine soils with different pollution levels were amended with either goethite, ferrihydrite or amorphous Al oxide at various ratios (0–10%). The effectiveness of such treatments was assessed by both batch and column leaching tests. The use of ferrihydrite or amorphous Al oxide proved to be highly effective to stabilize Sb. Immobilization levels of 100% were found when doses of 5% ferrihydrite or 10% amorphous Al oxide were applied, regardless of the soil Sb load. Column leaching studies also showed a high Sb leaching reduction (>75%) when soils were amended with 1% ferrihydrite or 5% amorphous Al oxide. Moreover, such treatments proved to simultaneously immobilize As and Pb in a great extent when soils were also polluted with such toxic elements.     

Risk assessment of linear alkylbenzene sulphonates, LAS, in agricultural soil revisited: robust chronic toxicity tests for Folsomia candida (Collembola), Aporrectodea caliginosa (Oligochaeta) and Enchytraeus crypticus (Enchytraeidae)

To obtain robust data on the toxicity of LAS, tests with the collembolan Folsomia candida L., the oligochaetes Aporrectodea caliginosa Savigny (earthworm) and Enchytraeus crypticus Westheide and Graefe (enchytraeid) were performed in a sandy loam soil. Additionally limited tests with LAS spiked to sewage sludge, and subsequently mixed into soil, were performed. For the endpoint of interest, reproduction in soil, we found an EC10 of 205 mg LAS kg(-1) soil [8.6-401] [95% confidence limits] for F. candida and an EC10 of 46 mg LAS kg(-1) soil [13-80] for A. caliginosa after 28 days. E. crypticus was not affected by concentrations up to 120 mg LAS kg(-1) soil. When adding (low contaminated) non-spiked sludge to soil, high stimulation of reproduction was observed for E. crypticus and A. caliginosa but not for F. candida. We argue that this difference in stimulative response between the tested species is related to the difference in feeding behaviour. Sludge spiked with LAS did not significantly affect the reproduction of F. candida (fertility: number of juvenile offspring) and A. caliginosa (fecundity: number of cocoons) (dose equivalent to 181 g and 91 g LAS kg(-1) sludge, respectively). Significantly reduced reproduction was observed for E. crypticus (at 120 mg LAS kg(-1) soil+sludge corresponding to 72 g LAS kg(-1) sludge) compared to non-spiked sludge. The reproduction by E. crypticus was, however, comparable to the reproduction observed in the control soil without sludge. Compared to LAS directly spiked to soil, the reproductive output of organisms exposed to spiked sludge was either not significantly different (F. candida, E. crypticus) or significantly improved (A. caliginosa). More studies are needed in order to make firm conclusions on the potential effect of artificially contaminated sludge in soil systems.     

The use of directional traps for the assessment of short-term phenanthrene effects upon soil springtail communities

Directional traps, both horizontal and vertical, were used to assess the behavioural impact of phenanthrene application on soil springtail communities. Avoidance was not detected. Rather, a vertical attraction of the dominant species, Folsomia manolachei, was demonstrated, as well as a decrease in horizontal movements of Lepidocyrtus lanuginosus, another important species mainly captured at the soil surface. Ecological consequences of the results are discussed.     

Toxicity of selected chlorobenzenes to aquatic organisms

Acute toxicity tests with six chlorobenzenes were performed on several aquatic organisms at different trophic levels. Fertility impairment on Daphnia and photosynthesis inhibition on Selenastrum were also carried on. Results are discussed together with physico-chemical properties of the molecules in order to identify structure-activity relationships and to predict environmental distribution. A hazard ranking procedure is also applied.     

Toxicity of methyl-tert-butyl ether to freshwater organisms

Increased input of the fuel oxygenate methyl-tert-butyl ether (MTBE) into aquatic systems has led to concerns about its effect(s) on aquatic life. As part of a study conducted by University of California scientists for the State of California, the Aquatic Toxicology Laboratory, UC Davis, reviewed existing literature on toxicity of MTBE to freshwater organisms, and new information was generated on chronic, developmental toxicity in fish, and potential toxicity of MTBE to California resident species. Depending on time of exposure and endpoint measured, MTBE is toxic to various aquatic organisms at concentrations of 57-> 1000 mg/l (invertebrates), and 388-2600 mg/l (vertebrates). Developmental effects in medaka (Oryzias latipes) were not observed at concentrations up to 480 mg/l, and all fish hatched and performed feeding and swimming in a normal manner. Bacterial assays proved most sensitive with toxicity to Salmonella typhimurium measured at 7.4 mg/l within 48 h. In microalgae, decreased growth was observed at 2400 and 4800 mg/l within 5 days. MTBE does not appear to bioaccumulate in fish and is rapidly excreted or metabolized. Collectively, the available data suggests that at environmental MTBE exposure levels found in surface waters (< 0.1 mg/l) this compound is likely not acutely toxic to aquatic life. However, more information is needed on chronic and sublethal effects before we can eliminate the possibility of risk to aquatic communities at currently detected concentrations.