No abstract

We investigated whether polychlorinated biphenyls (PCBs) partitioning between the dissolved and particulate phases in two high altitude alpine lakes was determined by the quantity, size structure, or composition of suspended particles. Within- and between-lakes differences in water-particulate phase partition coefficient (Kp) were not related to total suspended matter, phytoplankton biomass, or taxonomic composition. Yet, a seasonal relationship between Kp and Kow was detected for both lakes, revealing equilibrium of PCBs partition when lakes were ice covered. On the contrary, PCBs partitioning between particles and water appeared kinetically limited during the open water season. Partition is therefore mainly governed by thermodynamic laws during the ice-covered period, while none of the tested physical or biological parameters seemed to explain the distribution of these particle-reactive contaminants in the open water period. PCBs were always mainly associated with particulate matter, but partitioning within different particulate size-fractions varied between seasons and between years during open water periods. When ice cover is absent, PCBs were mainly adsorbed on microplankton, the largest phytoplanktonic size fraction, which is the least likely to get grazed by pelagic microconsumers.

Monodisperse copolymer latex particles with aldehyde groups at the surface have been prepared by a two-step process, comprising first a soap-free emulsion polymerization of styrene using potassium peroxodisulfate as an initiator and secondly a surface functionalization of the seed particles by copolymerizing p-formylstyrene (system. name: 4-vinylbenzaldehyde) using various addition methods. The final latices were characterized with respect to monomer conversion, copolymer composition, particle size and distribution. Particular attention was paid to the characterization of surface aldehyde groups using two different analytical methods such as X-ray photoelectron spectroscopy (XPS) and radioactive labelling by coupling with (l-3H,)-2-aminoethanol.

Cold aquatic ecosystems such as high altitude alpine lakes are expected to act as long-term sinks of polychlorinated biphenyls (PCBs), the burden of which might even be intensified by global warming. Because the physical, chemical, and biological structures of high altitude lakes are highly responsive to climate change, both PCB exposure and bioaccumulation are likely to be strongly altered in the near future. Yet, in the absence of mechanistic knowledge of the processes regulating fish contamination with PCB in such ecosystems, their fate cannot be predicted. The aim of this study was to investigate the relative roles of biomagnification and bioconcentration on the individual, seasonal, and between-site variability of fish PCB contamination in 2 alpine, high altitude lakes. The intra-and within-lake variability of fish PCBs was not related to differences in fish physiology (size, age, or lipid content) and only marginally tied to fish feeding habitats (assessed from fatty acid composition and δ 13 C) or trophic position (δ 15 N). These results suggested that the trophic pathway and biomagnification contributed little to the observed differences in fish PCB concentrations between lakes, seasons, and individuals. Moreover, the fish PCB levels did not depend on the total PCB concentration in the water, but the fish contamination dynamics during the spring thaw pointed to a significant role of dissolved PCBs during this season in both lakes. In high altitude lakes, low temperatures might contribute to kinetically limit equilibrium with dietary PCBs, thereafter favouring bioconcentration over biomagnification pathways by which fish become contaminated with PCBs.