Effect of two TiO2 nanoparticles on the growth of unicellular green algae using the OECD 201 test guideline: influence of the exposure system

This work aimed at assessing the influence of different exposure systems to perform the commonly used OECD 201 freshwater algal growth inhibition test in the context of nanoparticles hazard assessment. Two distinct TiO₂ nanoparticles were considered and three different exposure systems were investigated: Erlenmeyers flasks and 24-well microplates (both using an orbital shake system), and an alternative system using cylindrical vials and magnetic stirring. All three systems are in accordance with the OECD 201 test guideline recommendations. We concluded that the exposure systems applied to achieve the test can substantially affect the ecotoxicological results and the subsequent calculated ECx. The selected systems influenced both the interaction between algal cells and TiO₂ nanoparticles as well as the growth inhibition recorded. Disparities in ecotoxicity relative to the TiO₂ nanoparticles tested were also observed and are finally discussed.     

Pesticide and agro-ecological transition: assessing the environmental and human impacts of pesticides and limiting their use

Environmental Science and Pollution Research -     

Permanent sample plots for natural tropical forests: A rationale with special emphasis on Central Africa

Permanent sample plots (PSP), where trees are individually and permanently marked, have received increased interest in Central Africa as a tool to monitor vegetation changes. Although techniques for mounting PSP in tropical forests are well known, their planning still deserves attention. This study aims at defining a rationale for determining the size and number of replicates for setting up PSP in mixed tropical forests. It considers PSP as a sampling plan to estimate a target quantity with its associated margin of error. The target quantity considered here is the stock recovery rate, which is a key parameter for forest management in Central Africa. It is computed separately for each commercial species. The number of trees to monitor for each species defines the margin of error on the stock recovery rate. The size and number of replicated plots is obtained as the solution of an optimization problem that consists in minimizing the margin of error for every species while ensuring that the mounting cost remains below a given threshold. This rationale was applied using the data from the M’Baïki experimental site in the Central African Republic. It showed that the stock recovery rate is a highly variable quantity, and that the typical cost that forest managers are prone to devote to PSP leads to high margins of error. It also showed that the size and number of replicated plots is related to the spatial pattern of trees: clustered or spatially heterogeneous patterns favor many small plots, whereas regular or spatially homogeneous patterns favor few large plots.     

Offspring sex ratio in relation to parental structural size and body condition in the long-lived wandering albatross (<Emphasis Type="Italic">Diomedea exulans</Emphasis>)

Sex ratio theory is one of the most controversial topics in evolutionary ecology. Many deviations from an equal production of males and females are reported in the literature, but few patterns appear to hold across species or populations. There is clearly a need to identify fitness effects of sex ratio variation. We studied this aspect in a population of a long-lived seabird, the wandering albatross (Diomedea exulans), using molecular sex-identification techniques. We report that parental traits affect both (1) fledgling traits in a sex-dependent way and (2) chick sex: Sons are overproduced when likely to be large at fledging and, to a lesser extent, daughters are overproduced when likely to be in good body condition at fledging. Because for the same population, a previous study reported that post-fledging survival was positively affected by size in males and by body condition in females, our results suggest that wandering albatrosses manipulate offspring sex to increase post-fledging survival.     

The toxicity of composted sediments from Mediterranean ports evaluated by several bioassays

This work investigates the ecotoxicological evaluation of contaminated dredged sediments from French Mediterranean navy harbour (A), commercial port (B) and two composite specimens (C) and (D) coming from the mixture of A and B with other port sediments. The toxicity of elutriates from these sediments is estimated using embryo-toxicity test, Microtox® solid phase test, LuminoTox, phytotoxicity tests and genotoxicity test. Bioassay responses are not clearly correlated with chemical contamination in the whole sediment and vary as a function of tested organisms. The highest contaminated samples (A and C) are almost always more toxic than the less contaminated samples (B and D). Among composite sediments, the mixture effect with other sediments is not efficient to decrease toxicity in sample C, suggesting that other parameters influence toxicity level such as particle size or organic matter content. These parameters should be taken into consideration in order to improve the efficiency of the mixture process and produce composite sediments with low toxicity.     

Non-biological inhibition-based sensing (NIBS) demonstrated for the detection of toxic arsenic compounds

This work demonstrates the success of a recently developed technique in chemical amplification, non-biological inhibition-based sensing (NIBS), for the detection of toxic arsenic compounds. Screening for toxic arsenic compounds is especially important due to their prevalence in wastewater and water sources. The detection method presented in this work amplifies the chemical response of toxic arsenic compounds by developing a sensor chemistry where the analyte inhibits, rather than enhances, the rate of a catalytic reaction. This technique mimics the work done with enzyme inhibition; however, using non-biological molecules allows for selective detection without the shelf-life issue associated with biological molecules. Using NIBS we find that we can enhance the sensitivity of the system by two orders of magnitude with no apparent loss in selectivity. This work demonstrates the versatility of NIBS, showing that the technique can be of general use for the detection of toxic compounds.     

Same-sex pair-bonds are equivalent to male–female bonds in a life-long socially monogamous songbird

Same-sex sexual behaviors are well documented in both captive and wild animals. In monogamous species, these behaviors are often exclusive, each individual having only one same-sex partner. A bias in sex ratio has been proposed as a social context yielding same-sex pair-bonding, but this hypothesis has rarely been tested. Focusing on a life-long pair-bonding songbird, the zebra finch Taeniopygia guttata, we tested whether same-sex pairing results from a shortage of individuals of the opposite sex. By experimentally skewing the sex ratio towards members of one sex, we observed a greater proportion of same-sex pair-bonds of that sex. Moreover, we assessed whether the quality and stability of social interactions were equivalent in same-sex and male–female pairs. Male–male and female–female same-sex bonds display the same behavioral characteristics as male–female ones: they are intense, highly selective, and stable affinitive relationships involving the same behavioral displays already described in wild birds. Moreover, same-sex male bonds were sufficiently strong not to split up when individuals were given the opportunity to reproduce with females. Because the pair-bond in socially monogamous species represents a partnership that may give advantages for survival (e.g., resources defense, fighting against predators, etc.), we propose that same-sex pairing in the zebra finch may result from the pressure to find a social partner.     

A Method to Assess and Define Environmental Flow Rules for Large Jurisdictional Regions1

Snelder, Ton, Doug Booker, and Nicolas Lamouroux, 2011. A Method to Assess and Define Environmental Flow Rules for Large Jurisdictional Regions. Journal of the American Water Resources Association (JAWRA) 47(4):828‐840. DOI: 10.1111/j.1752‐1688.2011.00556.x Abstract: Hydrological rules of thumb are used across jurisdictional regions to set minimum flows and allocation limits that apply by default (i.e., when more detailed site‐scale studies have not been carried out). Uniform rules do not account for spatial variation in environmental characteristics, resulting in inconsistent consequences for the protection of ecosystems, and the reliability of water resources. We developed a method for assessing hydrological rules of thumb that describes their consequences for protection of the ecosystem (in terms of retention of physical habitat) and the reliability of the water resource. The method links regionalized flow duration curves, at‐station hydraulic geometry, and generalized physical habitat models to make assessments at many locations across a region. The method estimates, for a given set of rules, the retained physical habitat for specified taxa/life stages and the proportion of the time abstractions are restricted. We applied the method to assess a set of rules that are proposed as default minimum flows and allocation limits for New Zealand rivers. The assessment showed that the minimum flow rules had variable consequences. The method could be used to quantify the tradeoff between environmental protection and water resources availability and reliability.     

On the Performance and Applicability of Nonlinear Two-Equation Turbulence Models for Urban Air Quality Modelling

It is well known that the commonly used k- turbulence models yield inaccurate predictions for complex flow fields. One reason for this inaccuracy is the misrepresentation of Reynolds stress differences. Nonlinear turbulence models are capable to overcome this weakness while being not considerably more complex. However no comprehensive studies are known which analyze the performance of nonlinear turbulence models for three-dimensional flows around building-shaped structures. In the present study the predictions of the flow around a surface-mounted cube using three nonlinear two-equation turbulence models are discussed. The results are compared with predictions of the standard k- turbulence model and wind tunnel measurements. It is shown that the use of nonlinear turbulence models can be beneficial in predicting wind flows around buildings.     

TRLFS characterization of Eu(III)-doped synthetic organo-hectorite

Europium(III) was coprecipitated with the clay mineral hectorite, a magnesian smectite, following a multi-step synthesis procedure. Different Eu(III) species associated with the proceeding synthetic hectorite were characterized by selectively exciting the 5D0-->7F0 transition at low temperature (T < 20 K). Fluorescence decay times indicated that Eu(III) ions may be incorporated in the octahedral layer of the brucite precursor as well as in the octahedral sheet of the clay mineral. The excitation spectra indicated that the substitution of the divalent Mg by the trivalent Eu induced local structural deformation. This investigation implements the molecular-level understanding of the f element structural incorporation into the octahedral layer of sheet silicates by coprecipitation with clay minerals from salt solutions at 100 degrees C.