Contribution of priority PAHs and POPs to Ah receptor-mediated activities in sediment samples from the River Elbe Estuary, Germany

Abstract

The estuary of the River Elbe between Hamburg and the North Sea (Germany) is a sink for contaminated sediment and suspended particulate matter (SPM). One major concern is the effect of human activities on the hydrodynamics, particularly the intensive dredging activities in this area that may result in remobilization of sediment-bound pollutants. The aim of this study was to identify pollutants contributing to the toxicological risk associated with re-suspension of sediments in the Elbe Estuary by use of an effect-directed analysis that combines chemical and biological analyses in with specific fractionation techniques. Sediments were collected from sites along the Elbe Estuary and a site from a small harbor basin of the Elbe Estuary that is known to be polluted. The sixteen priority EPA-PAHs were quantified in organic extracts of sediments. In addition, dioxin equivalents of sediments were investigated by use of the 7-ethoxyresorufin O-deethylase assay with RTL-W1 cells and the Ah receptor-mediated luciferase transactivation assay with H4IIE-luc cells. Quantification of the 16 priority PAHs revealed that sediments were moderately contaminated at all of the sites in the Elbe River Estuary (<0.02-0.906 µg/g dw). Sediments contained relatively small concentrations of dioxin equivalents (Bio-TEQ) with concentrations ranging from 15.5 to 322 pg/g dw, which were significantly correlated with dioxin equivalents calculated based on toxicity reference values and concentrations of PAH. The concentration of Bio-TEQ at the reference site exceeded 200,000 pg/g dw. In a potency balance the 16 PAHs explained between 47 and 118% of the Bio-TEQ in the luciferase assay, which can be explained by the constant input of PAHs bound to SPM from the upper course of the Elbe River into its estuary. Successful identification of a significant portion of dioxin-like activity to priority PAHs in complex environmental samples such as sediments has rarely been reported.

Figure 1. Sampling sites along the lower part of the Elbe River between the North Sea and Hamburg harbor.

Areas shaded in light grey are municipalities. Sampling was done in autumn 2006.

Figure 2. Dose-response curves of the luciferase assay (A) and the RTL-W1 assay (B) to the 2,3,7,8-tretrachlorodibenzo-p-dioxin (TCDD) standard.

Figure 3. Dioxin-like activity of the crude sediment extracts in the RTL-W1 (grey bars; n = 3) and H4IIE.luc (black bars; n = 3) assays expressed as biological toxicity equivalents (Bio-TEQ; pg/g dw).

If no grey or black bar is given, no Bio-TEQ was detectable. River kilometers and the known highly contaminated reference site are given on the x-axis.

Figure 4. Comparison of the total biological response in the RTL-W1 assay (Bio-TEQs) of crude sediment extracts, the calculated contribution of the measured PAH toxic equivalents (TEQs) and the TEQs of non-acid-degradable compounds (e.g. PCB and PCDD/PCDF) out of the biological response to the multilayer fraction.

The unknown portion (in percent) of the overall activities is given in regard to the Bio-TEQs of the crude extracts. PAH-TEQs were calculated using the relative potency factors taken from Bols et al. 1999 and are given in pg/g dw . (n.d. = not detectable).

Figure 5. Comparison of the total biological response in the H4IIE.luc assay (Bio-TEQs) of crude sediment extracts, the calculated contribution of the measured PAH toxic equivalents (TEQs) and the TEQs of non-acid-degradable compounds (e.g. PCB and PCDD/PCDF) out of the biological response to the multilayer fraction.

The unknown portion (in percent) of the overall activities is given in regard to the Bio-TEQs of the crude extracts. PAH-TEQs were calculated using the relative potency factors taken from Machala et al. 2001 and are given in pg/g dw. (n.d. = not detectable).