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  • SpringerLink  (5)
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  • 1
    Language: English
    In: Environmental Science and Pollution Research, 2013, Vol.20(10), pp.7341-7347
    Description: Although generally misunderstood, the p value is the probability of the test results or more extreme results given H 0 is true: it is not the probability of H 0 being true given the results. To obtain directly useful insight about H 0 , the positive predictive value (PPV) and the negative predictive value (NPV) may be useful extensions of null hypothesis significance testing (NHST). They provide information about the probability of statistically significant and non-significant test outcomes being true based on an a priori defined biologically meaningful effect size. The present study explores the utility of PPV and NPV in an ecotoxicological context by using the frequently applied Daphnia magna reproduction test (OECD guideline 211) and the chemical stressor lindane as a model system. The results indicate that especially the NPV deviates meaningfully between a test design strictly following the guideline and an experimental procedure controlling for α and β at the level of 0.05. Consequently, PPV and NPV may be useful supplements to NHST that inform the researcher about the level of confidence warranted by both statistically significant and non-significant test results. This approach also reinforces the value of considering α , β , and a biologically meaningful effect size a priori.
    Keywords: Sample size ; Bayesian ; Power analysis ; Effect size ; Type I error rate ; Type II error rate
    ISSN: 0944-1344
    E-ISSN: 1614-7499
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  • 2
    Language: English
    In: Environmental Science and Pollution Research, 2015, Vol.22(5), pp.3955-3957
    Description: We argued recently that the positive predictive value (PPV) and the negative predictive value (NPV) are valuable metrics to include during null hypothesis significance testing: They inform the researcher about the probability of statistically significant and non-significant test outcomes actually being true. Although commonly misunderstood, a reported p value estimates only the probability of obtaining the results or more extreme results if the null hypothesis of no effect was true. Calculations of the more informative PPV and NPV require a priori estimate of the probability ( R ). The present document discusses challenges of estimating R .
    Keywords: Sample size ; Bayesian ; Power analysis ; Effect size ; Type I error rate ; Type II error rate
    ISSN: 0944-1344
    E-ISSN: 1614-7499
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  • 3
    Language: English
    In: Environmental Science and Pollution Research, 2018, Vol.25(21), pp.20911-20919
    Description: The impact of titanium dioxide nanoparticles (nano-TiO 2 ) on the bioavailability of metals in aquatic filter-feeding organisms has rarely been investigated, especially in the presence of algae as a food source. In this study, we quantified the accumulation and subcellular distribution of arsenate ( As V ) in Daphnia magna in the presence of nano-TiO 2 and a green alga ( Scenedesmus obliquus ) food source. Results showed that S. obliquus significantly increased the accumulation of total arsenic ( As ) and titanium ( Ti ) in D. magna . The presence of this food source increased As in metal-sensitive fractions (MSF) and as biologically detoxified metals (BDM), while it decreased Ti levels in MSF but increased levels as BDM. The difference in the subcellular distribution of As and Ti demonstrates the dissociation of As from nano-TiO 2 during digestion at subcellular partitioning irrespective of food availability. In turn, the presence of algae was shown to increase metal-based toxicity in D. magna due to the transfer of As from BMD to MSF. Furthermore, S. obliquus significantly increased the concentration of As and Ti in soluble fractions, indicating that As and nano-TiO 2 ingested by D. magna could be transferred more readily to their predators in the presence of S. obliquus . Our study shows the potential of algae to increase the toxicity and biomagnification of As V . Furthermore, it highlights food as an important factor in the toxicity assessment of nanomaterials and co-existing pollutants.
    Keywords: Nanoparticles ; Arsenic ; Bioavailability ; Subcellular distribution ; Algae
    ISSN: 0944-1344
    E-ISSN: 1614-7499
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  • 4
    Language: English
    In: Journal of Nanoparticle Research, 2016, Vol.18(10), pp.1-10
    Description: CeO 2 nanoparticles with various characteristics find an increasing number of applications in the electronic, medical, and other industries and are therefore likely released in the environment. This calls for investigations linking the physicochemical properties of these particles with their potential environmental impacts. In this study, CeO 2 nanoparticle powders were prepared using three different precursors [Ce(NO 3 ) 3 , CeCl 3 , and Ce(CH 3 COO) 3 ] and annealing temperatures (300, 500, and 700 °C). This procedure resulted in nine different types of nanoparticles with differing size (5–90 nm), morphology, surface Ce 3+ /Ce 4+ ratio, and slightly different crystal structures as characterized using transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, and X-ray diffraction measurements with Rietveld refinement. These CeO 2 nanoparticles underwent toxicity testing at concentrations up to 64 mg L −1 using Daphnia magna . Toxic effects were observed for three particle types with EC50 values between 5 and 64 mg L −1 . No clear correlation was observed between the physicochemical properties (size, shape, oxygen occupancy, Ce 3+ /Ce 4+ ratio) of the nanoparticles and their toxicity. However, toxicity was correlated with the amount of Ce remaining suspended in the test medium after 24 h. This indicated that toxic effects may depend on the colloidal stability of CeO 2 nanoparticles during the first day of exposure. Therefore, being readily suspended and remaining stable for several days in the aquatic media increases the likelihood that CeO 2 nanoparticles will cause unwanted adverse effects.
    Keywords: CeO ; Ecotoxicity ; Daphnia magna ; XPS ; XRD ; Health and environmental effects
    ISSN: 1388-0764
    E-ISSN: 1572-896X
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  • 5
    Language: English
    In: Bulletin of Environmental Contamination and Toxicology, 2019, Vol.102(3), pp.303-309
    Description: The leaf-shredding crustacean Hyalella azteca , which is indigenous to Northern and Central America, is used to assess environmental risks associated with (metal-)contaminated sediments and to propose sediment quality standards also in Europe. Yet, it is unknown if H. azteca is protective for European crustacean shredders. We thus compared the sensitivity of H. azteca with that of the European species Asellus aquaticus and Gammarus fossarum towards copper- and cadmium-contaminated sediments (prepared according to OECD 218) under laboratory conditions employing mortality and leaf consumption as endpoints. H. azteca either reacted approximately fourfold more sensitive than the most tolerant tested species (as for cadmium) or its sensitivity was only 1.6 times lower than the highest sensitivity determined (as for copper), which should be covered by safety factors applied during risk assessments. Therefore, the results for the sediment type and the two heavy metals tested during the present study in combination with the existence of standardized testing protocols, their ease of culture, and short generation time, suggest H. azteca as suitable crustacean model shredder for assessing the toxicity of sediment-associated metals in Europe.
    Keywords: Body burden ; Ecosystem functioning ; Metals ; Sediment toxicity tests ; Shredders
    ISSN: 0007-4861
    E-ISSN: 1432-0800
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