Temporal variability of organic micropollutants in suspended particulate matter of the River Elbe at Hamburg and the River Mulde at Dessau, Germany

The compound classes of n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and a number of chlorinated hydrocarbons (CHs) in the River Elbe and its t ributary Mulde were investigated on the basis of monthly mixed samples of s uspended particulate matter (SPM). Covering the period from September 1994 to August 1995, samples from the River Elbe were taken at Hamburg, those fr om the River Mulde at Dessau. The samples were extracted by supercritical f luid extraction (SFE). Analysis of all substance groups were performed by h ighperformance liquid chromatography (HPLC), followed by gas chromatography with mass spectrometric detection (GC/MSD). As a statistical approach for the interpretation of data, hierarchical cluster analysis of the individual compound classes were performed to determine differences or similarities b etween the sampling sites Hamburg and Dessau to find spatial and seasonal c oncentration patterns. These analysis showed that, with a high significance , the concentration patterns of n-alkanes, PAHs, and CHs were sampling site -specific in both the Elbe and Mulde throughout the entire sampling period. In all cases, clustering of mostly consecutive months indicated continuous , slow changes of input, which moreover showed a constancy with respect to annual cycles. Correlation analysis of pollutant loads with different hydro graphic parameters showed a number of linear dependencies of the contaminan ts with temperature, SPM content, and water discharge. Annual fluxes of par ticle-bound pollutants were calculated for each sampling site, taking into account the average monthly SPM levels and the water discharge. The particl e-bound pollutant loads for the River Elbe at Hamburg were estimated to 13. 4 t/a n-alkanes, 4.1 t/a PAHs, and 175.8 kg/a CHs. The pollutant loads for the River Mulde at Dessau amounted 0.55 t/a n-alkanes, 0.14 t/a PAHs, and 1 5.5 kg/a CHs during the monitoring period. The input of n-alkanes originate d from different sources. The n-alkane pattern of samples of the River Elbe showed a predominance of odd-numbered compounds in the range of C-20 and C -30 originating from terrestrial plants and, depending on the season, high concentrations of C-15 and C-17 due to aquatic organisms. Only a small prop ortion of n-alkane input originated from petroleum sources. Samples from th e River Mulde showed high amounts of the n-alkanes C-12 to C-15, indicating the input of light oil throughout the entire sampling period, constituting approximately 25% of the total n-alkane concentration. PAHs, which are con sidered combustion products, were widely distributed in all samples. Althou gh the major inputs of PAHs were probably combustion sources and urban runo ff, unusually high concentrations were found for some PAHs, which can be ex plained by point sources. A comparison of the standardized PAH patterns in samples from both stations clearly showed that higher fused ring systems, w hich mainly originate from combustion processes (four- to six-ring systems) , had considerably higher relative concentrations in SPM from the Elbe than from the Mulde, where higher relative concentrations of the two- and three -ring systems were measured. This confirms findings that petroleum input wa s higher in the Mulde than in the Elbe. Concentrations of chlorinated hydro carbons in SPM samples from the river Mulde had comparatively high levels. The largest differences were found for p,p'-DDT and its metabolites p,p'-DD D and p,p'-DDE. On average, concentrations of p,p'-DDT, p,p'-DDD, and p,p'- DDE in the Mulde were about 10, 15, and 25 times higher, respectively, than in the Elbe. Concentrations of HCB, which in the samples from Hamburg had the highest co ncentrations of all CHs, were found to be higher by about a factor of 3 in the Mulde River. The PCB levels in samples from the Mulde and Elbe were abo ut equal, although there were differences in the pattern of PCB congeners.