109
• The TOC content is a good marker for PCA concentrations. Higher TOC levels
indicated usually also a higher PCA burden. This is e.g. demonstrated by the
samples from station 710 from 2001 and 2004. The concentration ratio of ca. 8.5 is
similar to that of the TOC (2001: 3.1 %, 2004: 0.48 %)
• Since the composition of the TOC can vary substantially due to the former history
(e.g. dump sites of sewage sludge indicated with the sample assignment KS), no
further interpretation was carried out.
• The highest PCA concentrations in the North Sea were found at the sites KS11
and KS8 in the Elbe estuary, where chemical waste and sewage sludge had been
dumped. Correspondingly high levels of hexachlorobenzene, PCBs, DDT and
hexachlorocyclohexanes were already reported during the monitoring campaign in
1997 and 1998 (BSH, 2002).
• Concentrations of mPCA (C14-16, 42-303 ng/g dw) were always higher than for
sPCA (Cio-13, 18-128 ng/g dw). The ratio mPCA/sPCA was between 1.7 to 3.2.
Studies of river and lake sediment from Germany and Switzerland found also 2-10
times higher mPCA concentrations (WHO, 1996). Reason can be the predominant
use of mPCAs in Europe (WHO, 1996). Figure 16 summarised the site-specific s-
and mPCA levels.
• The average chlorine content of sPCAs in sediments varied between 53-56 % and
for mPCAs between 46-50 %. Mean molecular weights were 334-391 g/mol for
sPCAs and 365-400 g/mol for mPCAs. Table 48 in appendix 2 summarises the
single sample values for future comparison.
