Resonant ion-pair formation in electron recombination with HF^+

The cross section for resonant ion-pair formation in the collision of low-energy electrons with HF^+ is calculated by the solution of the time-dependent Schrodinger equation with multiple coupled states using a wave packet method. A diabatization procedure is proposed to obtain the electronic couplings between quasidiabatic potentials of ^1Sigma^+ symmetry for HF. By including these couplings between the neutral states, the cross section for ion-pair formation increases with about two orders of magnitude compared with the cross section for direct dissociation. Qualitative agreement with the measured cross section is obtained. The oscillations in the calculated cross section are analyzed. The cross section for ion-pair formation in electron recombination with DF^+ is calculated to determine the effect of isotopic substitution.Comment: 12 pages, 12 figure

Perfluorinated alkyl substances (PFASs) in northern Spain municipal solid waste landfill leachates

Landfill leachates have been recognized as significant secondary sources of poly- and perfluoroalkyl substances (PFASs). This study presents data on the occurrence and concentration of 11 perfluoroalkyl carboxylates (PFCAs) and 5 perfluoroalkyl sulfonates (PFSAs) in leachates from 4 municipal solid waste landfill sites located across northern Spain. To the best of our knowledge, this is the first report of the presence of PFASs in Spanish landfill leachates. Two of the landfill sites applied on-site treatment using membrane bioreactors (MBR), and its effect on PFASs occurrence is also reported. Total PFASs (∑PFASs) in raw leachates reached 1378.9 ng/L, while in treated samples ∑PFASs was approximately two-fold (3162.3 ng/L). PFCAs accounted for the majority of the detected PFASs and perfluorooctanoic acid (PFOA) was the dominant compound in raw leachates (42.6%), followed by shorter chain PFHxA (30.1%), PFPeA and PFBA. The age of the sites might explain the PFASs pattern found in raw leachates as all of them were stabilized leachates. However, PFASs profile was different in treated samples where the most abundant compound was PFHxA (26.5%), followed by linear perfluorobutane sulfonate (L-PFBS) (18.7%) and PFOA (17.7%). The overall increase of the PFASs content as well as the change in the PFASs profile after the MBR treatment, could be explained by the possible degradation of PFASs precursors such as fluorotelomer alcohols or fluorotelomer sulfonates. Using the volume of leachates generated in the landfill sites, that served 1.8 million people, the discharge of 16 ∑PFASs contained in the landfill leachates was estimated as 1209 g/year.The authors thank financial support from the Spanish Ministry of Economy and Competitiveness (Project CTM2013-44081-R)

Seasonal dynamics of PCBs in the plankton of Lake Erie

L’importante masse des données et documents disponibles pour les cher- cheurs dans les corpus de lettres et sciences humaines implique aujourd’hui de créer de nouveaux dispositifs de visualisation de l’information et d’aide à l’édition critique. La nécessité pour les chercheurs de devoir critiquer les sources qui seront au cœur de leurs travaux induit de pouvoir rechercher, visualiser, annoter, et constituer des corpus de références bibliographiques dans des processus de recherche de plus en plus collectif et collaboratifs. C'est la proposition faite avec ISIDORE Table (ou ISIDORE tactile)

Quantitative biomonitoring of PAHs using the barnes mussel (Elliptio complanata)

The elimination rate constants (k2) of nine polycyclic aromatic hydrocarbons (PAHs) were examined for the freshwater mussel Elliptio complanata. The concentrations of fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, and indeno[1,2,3-c,d]-pyrene revealed a significant inverse relationship with time and their k2 values ranged from 0.10 to 0.22 day-1. The k2 values of these significantly cleared PAHs were similar to k2 values observed for nonmetabolized organochlorines in mussels previously reported in the literature. The inverse relationship between k2 and Kow provides evidence that the nine PAHs were being passively eliminated from the mussels and that they can be used to calibrate the mussel as a quantitative biomonitor. A general expression relating elimination rate constants and chemical Kow is derived for hydrophobic contaminants in E. complanata. The k2 versus log Kow regression equation for mussels developed herein was similar to other studies documenting the elimination of PCBs and PAHs in a number of bivalve species