Umweltprobenbank des Bundes - Auswertung der Analysen von Schwebstoffproben aus den Jahren 2005 bis 2009
Weinfurtner, Karlheinz; Fliedner, Annette
Schmallenberg: Fraunhofer-Institut für Molekularbiologie und Angewandte Oekologie, 2012. - 65
Executive summary
Since 2005 suspended particulate matter (SPM) is sampled monthly at sampling sites in six German rivers (Rhine, Elbe, Danube, Saar, Saale, and Mulde). Samples of SPM (sieved as fraction < 2 mm) of one year and sampling site eventually are combined to annual samples and stored at -150°C in the archive of the German Environmental Specimen Bank (ESB).
Prior to storage the SPM samples are characterized physically and chemically and analyzed for a set of elements (As, Cd, Co, Cr, Cu, Fe, Hg, Ni, P, Pb, Se, Tl, Zn) and organic compounds (PAH and chlorohydrocarbons). In this report results of the investigation period 2005 to 2009 are compiled and discussed.
Chemical and physical parameters
The data show that the physical and chemical parameters (e.g., texture, carbon content, and pH) at each sampling site are quite constant over time and show no trends. This indicates that the mode of sampling, i.e., monthly sampling and pooling of the samples to obtain yearly homogenates, obviously yields representative and reproducible samples that are not or only slightly influenced by single events like floods.
Element concentration
Element concentrations in SPM differ significantly between sampling sites. Generally, elements are lowest in SPM from the rivers Rhine and Danube. In both rivers a downstream increase can be observed. Highest element levels are detected in the Elbe tributaries Saale and Mulde. Mining activities are the most likely source here. Relatively high element loads are also found at the sampling sites of the upper Elbe. These are partly imported from the Czech Republic and decrease downstream of the border. In many cases, however, levels increase again as the Elbe passes the river Saale mouth.
No temporal trends are observed for elements at any site during the study period.
Organic compounds
SPM contamination with organic compounds also differs significantly between rivers and sampling sites. PAH concentrations are highest in the rivers Saar, Elbe and Saale while relatively low levels are detected in SPM from the rivers Rhine and Danube. In the Rhine, PAH levels increase downstream as the river flows through the densely populated area around Cologne and the Ruhr conurbation. In contrast, a downstream decrease is found in the Danube which is probably related to dilution effects by the river Inn which enters the Danube near the most downstream sampling site Jochenstein.
The organochlorine pesticides DDX (DDT and degradation products) and HCH (hexachlorobenzene) are highest in SPM from the rivers Mulde and Elbe. This may be explained by the fact that both compounds were used longer and more extensively in the former German Democratic Republic compared to the western part of Germany. Lowest levels of DDX and HCH are found in the Danube.
Highest concentrations of PCB (polychlorinated biphenyls, sum of seven congeners) are usually detected in SPM from the rivers Elbe and Saar while lowest levels are observed in the Danube and at the Rhine sampling site Weil.
In the Elbe, no downstream trends are apparent for PCB, DDX and HCH and only little differences are observed between the sampling sites. The only exemption is the most downstream sampling site Blankenese where the dilution effects of the North Sea water result in significantly lower SPM contaminations. In the rivers Rhine and Saar PCB, DDX and HCH increase downstream. In contrast, lowest concentrations in the river Danube are found at the downstream sampling site Jochenstein which may be a result of dilution effects of the confluence with the river Inn.
In contrast to the findings for elements, temporal trends can be observed for the levels of several organic compounds although these trends are mostly not statistically significant because of the short study period. Examples are the decreasing concentrations of some PAH (e.g., benz[a]anthracene, benzo[a]pyrene and benzo[e]pyrene) in SPM from the Rhine and of the PCB congeners 101 and 118 in the Saar.
Conclusion
A direct comparison of ESB results with data of other monitoring programmes is complicated due to differences in samplings methods, sampling intervals and sampling sites. However, basic inconsistencies could not be observed and the archived material seems particular suitable for the retrospective monitoring of emerging substances.