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The article examines the differential responses of biomarkers in tissues of a freshwater mussel to the exposure of sediment extracts with different levels of contamination. The study exposes zebra mussels to extracts of sediments obtained from two sites, a contaminated lake and a relatively clean lake. The section aims to examine whether six selected biomarkers could discriminate between the two sediments. Control experiments were also conducted in which mussels were kept under the same experimental conditions as the test samples, but exposed only to Dutch standard water.

Aqueous solubilities, n-octanol/water partition coefficients (Kows), and Henry's law constants were determined for a range of polycyclic aromatic hydrocarbons (PAHs) using a generator-column, slow-stirring, and gas-purge method, respectively. The currently obtained data were compared to available literature data. For seven of the PAHs no Kows previously were determined with the slow-stirring method. For four of the PAHs the present study reports the first experimental Henry's law constants. Relationships between subcooled liquid solubilities, Kows and Henry's law constants as a function of molar volume are discussed. A consistent data set was obtained, for which an excellent correlation was found between subcooled liquid solubility and molar volume. A linear fit did not accurately describe the relationship between log Kow and molar volume. This is probably due to a decreasing solubility in n-octanol with increasing molar volume. Finally, a high correlation was found between Henry's law constant and molar volume. The presently obtained dataset can be used to predict the fate and behavior of unsubstituted homocyclic PAHs. [ABSTRACT FROM AUTHOR]

As an example of the importance and the potential of in situ structure/function studies, nitrifying aggregates from different zones of a lab-scale fluidised bed reactor were analysed by microelectrode measurements of O2, NH4+, NO2-, and NO3- and in situ hybridisationtargeting the 16S rRNA of the nitrifying bacteria. A shift from an ammonia oxidising to a nitrite oxidising community is present along the reactor. In the single aggregates an active nitrifying shell of about 100 5 m could be related to the maximum abundance of nitrifiers inthis zone. Interestingly, the main actors in this system are not representatives of the well described genera Nitrosomonas and Nitrobacter but some other ammonia oxidisers from the _ subclass of Proteobacteria and a thus far unknown nitrite oxidising population. ) 1998 IAWQ Published by Elsevier Science Ltd. [ABSTRACT FROM AUTHOR]