The physico-chemical speciation of polycyclic aromatic hydrocarbons (PAH) in aquatic systems

Summary Physico-chemical speciation is presented as a concept to describe the environmental chemistry of organic compounds in aquatic systems, using polycyclic aromatic hydrocarbons as an example.Survey data and experimental results are reported which demonstrate the presence of different physico-chemical species of PAH in the Tamar Estuary, UK.The degree, and hence chemistry of binding of PAH to particulates in the Tamar is shown to be incompatible with current sorption modelling techniques. This finding has extensive repercussions on prediction of the aquatic chemistry of PAH, including availibility of the compounds for fates such as photo-oxidation and biological uptake/ toxicity.

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Die physikalisch-chemische Speziation polycyclischer aromatischer Kohlenwasserstoffe (PAH) in aquatischen Systemen

Zusammenfassung Die physikalisch-chemische Speziation wird dargestellt zur Beschreibung der Umweltchemie organischer Verbindungen in aquatischen Systemen. Dabei dienen die PAH als Beispiel. Es werden Meßergebnisse und experimentelle Befunde gegeben, die die Anwesenheit verschiedener physikalisch-chemischer Spezien von PAH in der Mündung des Tamar-Flusses (UK) demonstrieren. Es wird gezeigt, daß der Grad und damit der Chemismus der Teilchenbindung von PAH im Tamarfluß nicht den üblichen Sorptionsmodellen entspricht. Diese Feststellung hat beträchtliche Auswirkungen auf die Voraussehbarkeit des aquatischen Chemismus der PAH einschließlich der Verfügbarkeit dieser Verbindungen für Photooxidation und biologische Aufnahme (Toxizität).

     

An ordered array of cadmium clusters assembled in zeolite A

We report the assembly of a cubic array of cationic cadmium clusters encapsulated in zeolite A, and its characterization through Rietveld analysis of powder synchrotron X-ray diffraction data and high resolution transmission electron microscopy.     

Adaptive disturbance transmission decoupling in active vehicle suspensions

With active vehicle suspension, one can tailor a vehicles response to load and inertial without affecting the vehicle response to road disturbances. This decoupling is achieved in [1] and [2] using a filtered combination of measured signals. These filters require exact knowledge of certain vehicle parameters including vehicle mass to achieve the desired decoupling. Here we propose a parameter adaptive version of these filters which does not require knowledge of vehicle parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Initial applications of phospholipid-coated mercury electrodes to the determination of polynuclear aromatic hydrocarbons and other organic micropollutants in aqueous systems

Mercury electrodes coated with di-oleoyl lecithin are described for the determination of polynuclear aromatic hydrocarbons (PAHs) and other micropollutants in aqueous solutions. The coated electrodes give a characteristic response in the capacitance/voltage curve to three-, four- and five- ring PAHs. The extent of the negative potential shift in the reversible capacitance peaks (and thus sensitivity) is related to the number of aromatic rings and substituents on the PAH. The capacitance/voltage curves were recorded by phase-sensitive a.c. voltammetry. The response is quantitatively related to the concentration of PAH in solution. Detection limits are about 0.4 μg l^?1 and the reproducibility (RSD) for separate samples is 7%. Intercalibration of the method with fluorescence spectrophotometry of pyrene-spiked sea-water samples, showed recoveries of 80%. The analytical system is useful for sea water and tap water. Bovine serum albumin (1 mg l^?1) enhances the sensitivity to pyrene. The monolayer is sensitive to oil-contaminated waters ( > 40 μg l^?1). The capacitance peaks respond selectively to other groups of compounds and to individual compounds within a group. The monolayer appears highly sensitive to the solution behaviour of PAHs because only soluble unbound PAHs penetrate the monolayer. Humic acid added to the solution decreases the response to PAH presumably by binding a fraction of PAH in the solution.     

Imaging the Atomic Position of Light Cations in a Porous Network and the Europium(III) Ion Exchange Capability by Aberration‐Corrected Electron Microscopy

In the present work, ETS‐10 microporous titanosilicate has been synthesized and its structure characterized by means of powder XRD and aberration corrected scanning transmission electron microscopy (C_s‐corrected STEM). For the first time, sodium ions have been imaged sitting inside the 7‐membered rings. The ion‐exchange capability has been tested by the inclusion of rare earth metals (Eu, Tb and Gd) to produce a luminescent material which has been studied by atomic‐resolution C_s‐corrected STEM. The data produced has allowed unambiguous imaging of light atoms in a microporous framework as well as determining the cationic metal positions for the first time, providing evidence of the importance of advanced electron microscopy methods for the study of the local environment of metals within zeolitic supports providing unique information of both systems (guest and support) at the same time.