Methods

19.3.1 Materials

Silica chromatography powder (SiO2), acetone, ethyl acetate, n-hexane, isooctane (Mallinckrodt Baker), methanol (Lab-Scan) aluminium oxide (Al2O3) (ICN Biomedicals, Boom BV, Meppel, The Netherlands) and C18-silica (Bakerbond, 40 mm, PrepLCpacking) were all obtained from Boom BV, Meppel, The Netherlands. All standard compounds used were obtained from different manufacturers, all ordered through Boom BV, Meppel. A list of compounds and their abbreviations is given in the Glossary. Thimbles for Soxhlet extraction were from Schleicher & Schuell MicroScience GmbH (Dassel, Germany). Sampler frame and other materials were tailor-made by a local workshop. Translucent sil-icone rubber sheeting (0.5 mm) was obtained from Technirub Vizo (Zeewolde, The Netherlands).

19.3.2 Mussels

19.3.2.1 Deployment of mussels

Mussels were obtained from a local mussel farm in the Eastern Scheldt. They were selected from a set of the same age and shell length (typically 45-50 mm). The selected 1100 mussels were randomly distributed into 40 subsets of 25 mussels (4 times 25 mussels are used for one station). Two samples of 100 mussels were frozen immediately to determine the concentrations of pollutants in the test organisms before deployment. The other portions were placed in holding nets and kept in aerated North Sea water until transport for deployment. For all stations an extra set of 10 mussels was packed to replace any mussels that died before deployment. During transport, the live mussels were placed in an isolated box with cooling elements maintaining adequate distance between mussels and cooling elements. When the deployment was delayed, e.g., in case of unsuitable weather, the mussels were stored in aerated seawater. The deployment frames were constructed from 12 mm stainless steel rod capable of mounting four mussel cages (Fig. 19.3). A mussel cage consists of two baskets, each containing 25 mussels, which were both mounted on a disc as shown in Fig. 19.2. Two cages were mounted at the lower position of the large frame using screws and safety nuts. Frames were fixed to a buoy or to the chain of the buoy at about 2 m below water surface.

After a period of 6 weeks the mussels were recovered. Any visible fouling was removed from the mussels and any mortality was recorded.

Fig. 19.2. Sampler frame for mussels and passive samplers. (a) fastening ring; (b) fixing eyes for and on samplers; (c) passive sampler; (d) mussels; (e) silicone rubber sheets; (f) U-shaped fixing rod; (g) cable strap, fixing the U-shaped fixing rod.

Dead mussels were not included in the sample. After collection the mussels were packed in bags, frozen immediately and transported to the laboratory. Until analysis, that usually took place within 6 weeks, samples were stored at —20°C. Water temperature was recorded at the start and end of the exposure.

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