Solvent toxicity to amphibian embryos and larvae

Organic micropollutants are often damaging for aquatic organisms. Being usually hydrophobic compounds, they are often dissolved in an organic co-solvent which increases their solubility in water. The aim of this study was to study the toxicity of various solvents on embryos (protected or not by jelly coat) and on tadpoles of the common frog (Rana temporaria). Tested solvents were methanol (MeOH), methylene chloride (CH(2)Cl(2)), dimethyl sulfoxyde (DMSO), acetone (Ac) and ethanol (EtOH). Embryos exhibited higher mortality rates than tadpoles. Embryos with jelly were more sensitive to high concentration of solvents than embryos without jelly (except for acetone). According to these results, Ac, DMSO and CH(2)Cl(2) can be used as co-solvents in water to help the dissolution of micropollutants at concentration equal to or lower than 0.001 ml/l for frog embryos, and EtOH, Ac and CH(2)Cl(2) at concentration equal to or lower than 0.01 ml/l for Rana temporaria tadpoles.     

Indicators for hydraulic and pollution retention assessment of stormwater infiltration basins

Infiltration basins are frequently used for stormwater management even though their long-term evolution is not well understood nor controlled. The two main problems encountered are clogging which compromises the hydraulic capacity of the basin and possible contamination of underlying soil and groundwater. This paper defines a framework for evaluating the hydraulic and pollution retention performance of infiltration basins in the long-term. Sets of context and performance indicators are proposed, along with two complementary modes of evaluation. Context indicators are identified in order to define the clogging and contamination states of the basins. Performance indicators are developed to assess several aspects of basin performance: drainage duration, overflow frequency, predictive life period, particle filtration and pollution trapping. Modes of evaluation include field investigation and long-term simulation modeling. Indicators are tested on five infiltration basins in suburban Lyon (France). Both context indicators and hydraulic performance indicators are reliable and their evaluation is representative of basin behavior. This is not the case for pollution retention performance indicators. Their assessment is difficult because of data quality. Field data has high uncertainties. The model is satisfactory for the hydraulic simulation and the evolution of clogging. Improvements are necessary for pollution flow simulation and the acquisition of better quality data is required.     

Herbaceous Covers to Control Tree Invasion in Rights-of-Way: Ecological Concepts and Applications

In northeastern America, thousands of kilometers of utility rights-of-way (ROWs) have to be managed to prevent the establishment of a tall vegetation cover that does not comply with safety and maintenance regulations. Recent decades have seen the emergence of ecologically based vegetation control strategies to reduce environmental impacts as well as maintenance costs. One such strategy is to take advantage of competitive herbaceous covers to limit tree invasion. This approach, however, as well as its fundamental underlying principles, has been little scrutinized. In this article, (1) we present the main ecological concepts supporting the use of a herbaceous cover to limit tree invasion, emphasizing naturally forested ecosystems of northeastern America. They include reported evidence of stable plant communities and an overview of potential underlying mechanisms of inhibition. (2) We then review field applications, specifically testing the ability of seeded herbaceous covers to control tree invasion in ROWs. (3) We discuss unresolved issues relevant to management and research. The available evidence suggests that seeding herbaceous covers in ROWs can help control tree invasion, but many issues still limit broad-scale applications. The various interactions that govern plant community dynamics are far from being fully understood, so selecting species still largely depends on an empirical approach. Patterns of resistance to tree invasion must be investigated over a wide range of spatial, historical, and environmental contexts to determine effective management and seeding practices that will lead to broad-scale applications. We suggest establishing communities rather than single dominant species and using as much as possible native species to limit risks of invasion.Published online