Measurement of volatile organic compounds in sediments of the Scheldt Estuary and the Southern North Sea

The concentrations and distribution of 13 priority volatile organic compoun ds (VOCs) were determined in sediments of the Scheldt estuary and the Belgi an continental shelf, using a modified Tekmar LSC 2000 purge-and-trap syste m coupled to GC-MS. The method allows a sample intake of up to 50 g wet wei ght and detection limits are between 0.003 ng/g (tetrachloromethane) and 0. 16 ng/g (m- and p-xylene). The repeatability (n = 5) varied between 4% (ben zene) and 17% (toluene) and the recoveries ranged from 59% (1,1-dichloroeth ane) to 99% (tetrachloromethane). Because of the nature of the contaminants , special attention was paid to analyte losses and contamination of the sam ples during storage aboard the research vessel. Spiked sediment samples wer e prepared in the laboratory and stored aboard under the same conditions as the environmental samples. The recoveries for these samples varied between 94 and 130%, which suggests that storage had no adverse effect on the samp les. No detectable VOC concentrations were found for most of the sampling s tations. However, in the Antwerp harbour area, significant concentrations o f VOCs were found. The sorption behaviour as predicted from laboratory equi librium partitioning experiments gives an indication of the in situ partiti oning behaviour of VOCs. Although VOCs in sediments should, in general, not be regarded as a major problem in the marine environment, high local conce ntrations may be a cause of concern. (C) 2001 Elsevier Science Ltd. All rig hts reserved.