Editorial

Floodplains and areas of low water movement as the linking partin the transport of suspended particulate matter and sediments along

lowland rivers

The transport of several pollutants in rivers is directlylinked to the transport of suspended particulate matter(SPM) and sediments. So far, contamination of river sedi-ments has been discussed in relation to harbour sedi-ments and the impact of coastal ecosystems. In order tomonitor and model the behaviour of pollutants in riversystems it is essential to know the dynamics of the sedi-ment transport in the system including the sources, path-ways and in-between storages of the sediments. Despitethese facts the European Water Framework Directive(WFD) does not consider sediment quality and quantityas a major issue (Salomons and Brils 2004). Nevertheless,the implementation of monitoring programs until 2006and the establishment of a program of measures until2009 (WFD article 16) have to consider sediment qualityat the catchment scale (F�rstner 2004, F�rstner and Heise2006).

Whereas in the last decades considerable work was doneto identify the sources, pathways, and behaviour of SPMand sediments within river systems (e.g. F�rstner 2002,2004; F�rstner et al. 2000, 2004) the areas where SPM andsediments are stored in-between, on their way from thesource to the sea, were not in the focus of research. Thisview changed in the last 10 years in Europe when dra-matic flood events eroded and transported hugeamounts of sediments and associated high loads of pollu-tants from these storage zones back into the rivers (e.g.River Rhine 1993, 1995; River Odra 1997; River Danube1999, 2002, 2006; River Vistula 2001; River Elbe 2002,2006; for more details about the Odra flood 1997 see spe-cial issue Acta hydrochim. hydrobiol. 27 (5) (1999), andabout the Elbe flood 2002 see special issue Acta hydro-chim. hydrobiol. 33 (5) (2005)). Another source of cata-strophic flooding and dispersion of highly contaminatedsediments in floodplain areas in the recent past was thefailure of mine tailing dams due to extreme rainfall (e.g.Aznalc�llar/Spain 1998, Baia Mare/Romania 2000). Theresult is a long lasting contamination of river sedimentsand floodplain soils.

Whereas the latter source depends on actual contamina-tion, the first one, the erosion of polluted sedimentsfrom in-between storage zones, also includes historicallycontaminated sediments, which could have been stored

in the areas of low water movement for considerabletime. The primary input factors for a re-suspension ofthese sediments are hydraulic processes (Westrich andF�rstner 2005). The potential risk through historicallypolluted sediments depends on the chemical mobiliza-tion of pollutants, the threshold of sediment erosion,and the erosion rate. All these information as well asbroad information about water volumes and morphol-ogy of rivers and of storage zones are necessary for model-ling pollutant transport on a river-basin scale or even fora small target area. Different geochemical and biologicalfactors are critical for the understanding and estimationof erosion, transport, and bioavailability of contami-nated sediments from in-between storage zones. In thefuture, sediment core studies may play a key role in asses-sing the emission-immission relationships of a riverbasin because they exhibit, under continuous undis-turbed sedimentation, a powerful tool to differentiatebetween the natural background levels and the anthro-pogenic accumulation of substances over an extendedperiod of time (F�rstner and Heise 2006).

Consequently, floodplain areas, groyne fields, river andflood barrages, or locks and weirs, as the most predomi-nant zones of in-between storages for sediments andtheir associated pollutants, were more and more consid-ered when studying the role and behaviour of sedimentsfor the transport of pollutants within river systems. Toexemplify the increasing attention for these storagezones as well as for the dynamic behaviour of sedimentsand their associated pollutants in river basins in therecent past three projects in Germany financed by theGerman Federal Ministry for Education and Research(BMBF) should be mentioned here:

– From 1996 to 1999 the influence of floods on the pollu-tion of floodplain areas and their soils were studied atthe river Elbe in Germany and the river Oka in Russia(“Wirkung von Hochwasserereignissen auf die Schadstoffbe-lastung von Auen und kulturwirtschaftlich genutzten B�denim �berschwemmungsbereich von Oka und Elbe”, FKz 02WT 9617/0). http://tws.gbv.de/DB=2.63/SET=2/TTL=141/SHW?FRST=149.

– The transport and turnover of substances withingroyne fields of the river Elbe was investigated by the

i 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Acta hydrochim. hydrobiol. 2006, 34, 171 – 173 171

172 Editorial Acta hydrochim. hydrobiol. 2006, 34, 171 –173

project “Stofftransport und -umsatz in Buhnenfeldern derElbe” (FKz 0339801/7) from 2000 to 2003. http://elise.bafg.de/servlet/is/3584/Ockenfeld_Endbericht.pdf.

– In the cooperative program SEDYMO (“Fine sedimentdynamics and pollutant mobility in rivers”) the interdisci-plinary approach focuses on the release of DOC, nutri-ents, and pollutants into the open water due to hydro-dynamic processes in rivers and estuaries. Three topicswere studied: ,experimental techniques’, ,processesand properties’,

,

development/validation of models’.http://www.tu-harburg.de/ut/sedymo/.

My own work about the role and function of floodplainareas as in-between storage zones for river sediments(Friese et al. 2000 a, b and references therein), the Elbeflood 2002 with the following joint-project of 14 institu-tions (http://www.ufz.de/hochwasser/), and the discus-sions within the working group “Sediments and WaterQuality” of the Water Chemical Society – a Division of theGerman Chemical Society led to the idea of editing thisspecial issue of Acta hydrochimica et hydrobiologica.

The following 10 papers cover different aspects of sedi-ment transport and in-between storage along lowlandrivers in Germany, Hungary, and Brazil. Most papersabout rivers in Germany focus on the river Elbe but onepaper also deals with results from the river Rhine (Jacouband Westrich), and one from the river Weiße Elster (Zer-ling et al.). The issue starts with a methodological contri-bution of Kr�ger et al. (“Methods to calculate sedimenta-tion rates of floodplain soils in the middle region ofthe Elbe River”) who focused in their paper on differentmethods available to calculate sedimentation rates inflood plain areas. The authors compared radiometric dat-ing (137Cs) with surface elevation differences, sedimenttrap analysis, load balancing, trace metal accumulation,b-HCH or Pb-isotope profiles. The paper is followed by 4contributions about groyne fields and their sedimentsshowing the importance of that kind of in-between stor-age zones for the sediment transport in the river Elbe.Kozerski et al. (“Tracer measurements in groyne fieldsfor the quantification of mean hydraulic residencetimes and of the exchange with the stream”) estimatedthe flow regime and hydraulic connectivity of the riverwith typical groyne fields by using dissolved dye. Theyfound residence times between 15 and 69 minutes.Another approach to study the flow behaviour withingroyne fields is presented by B�hme (“Distribution ofwater quality parameters in two cross-sections of theriver Elbe measured with high local, temporal, and ana-lytic resolution”), who studied groyne fields at two cross-sections at Schnackenburg and Lauenburg for the mixingbehaviour of several physical and chemical parameters

(e.g. temperature, pH, oxygen, electric conductivity, tur-bidity, fluorescence). Van der Veen et al. (“Spatial distri-bution and bonding forms of heavy metals in sedi-ments along the middle course of the river Elbe (km287…390)”) sampled sediment cores from 8 groyne fieldsand did a thorough mineralogical and geochemicalstudy on it (e.g. mineralogical composition, pH, grainsize distribution, carbon and sulfur content, main andtrace element concentrations). The special focus of thepaper was the estimation of the potential mobility andecological availability of the heavy metals by bondingform analysis. In the paper of Schwartz (“Geochemicalcharacterisation and erosion stability of fine-grainedgroyne field sediments of the Middle Elbe River”)results on sediment cores from a typical groyne field aredescribed in detail for their physical and physico-chemi-cal conditions, the nutrient and metal load, and their dis-tribution with depth. Also erosion stability tests were per-formed and calculations made for the total amount ofmatter stored in a typical groyne field of the river Elbe.

The importance of floodplain areas as storage zones forriver sediments is demonstrated by a contribution aboutthe heavy metal input into floodplains at the inflow ofthe river Weiße Elster into the river Saale (Zerling et al.“Heavy metal inflow into the floodplains at the mouthof the river Weiße Elster (Central Germany)”). Theauthors summarize investigations from 1998 to 2002 ona 5 km2 floodplain area considering flood sediments, sus-pended particulate matter, and floodplain soils. Between34 and 55% of the annual SPM load is stored in this stor-age zone depending on water discharge which corre-sponds to 5 000 to 40 000 tons or 1 to 8 kg/m2 of depos-ited sediment.

Floodplain and river sediments are excellent archives forrecent and historical pollution. This property was usedby the papers of Costa et al. and Kraft et al. In the paper ofCosta et al. (“Sediment contamination in floodplainsand alluvial terraces as an historical record of goldexploitation in the Carmo River basin, Southeast Quad-ril�tero Ferr�fero, Minas Gerais, Brazil”) floodplain soilsand alluvial sediments of the river Carmo were used todetect and evaluate the historical contamination by goldexploitation in the Iron Quadrangle of Minas Gerais inBrazil. The main pollutant associated with the goldmining is arsenic which showed maximum concentra-tions in the sediments and soils of 2 000 mg/kg. The con-tribution of Kraft et al. (“The effects of mining in North-ern Romania on the heavy metal distribution in sedi-ments of the rivers Szamos and Tisza (Hungary)”) wasconducted as a consequence of the Baia Mare (NW Roma-nia) gold mines’ dam breaking in January 2000. Besides

i 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www3.interscience.wiley.com/cgi-bin/jhome/5007772

Acta hydrochim. hydrobiol. 2006, 34, 171 – 173 Editorial 173

cyanide, which caused immediate toxic effects on fish,huge amounts of heavy metals like Pb, Cd, Cu, and Znwere discarded and deposited in the floodplains down-stream. Binding form analyses revealed that especiallyCd and Zn were deposited in easily available form to theenvironment.

The second and final part of this special edition presentstwo contributions about modelling of sediment trans-port in a floodplain area of the Elbe and in a lock andweir system of the Rhine. B�ttner et al. (“Numerical mod-elling of floodplain hydraulics and suspended sedi-ment transport and deposition at the event scale in themiddle river Elbe, Germany”) modelled the flow andsediment transport within a detailed mapped floodplainarea of the middle course of the river Elbe. The modelswere calibrated and validated by detailed measurementof the surface water elevations, the velocities at six pro-files, and the suspended sediment concentration anddeposition. The authors found a considerable good agree-ment for the modelled and measured flow velocities andcalculated an average sediment input of 35 g/(m2 d). Thehighest sedimentation rate estimated was 700 g/(m2 d)(dry density 90 kg/m3).

A 2D numerical transport model was developed byJacoub and Westrich (“Modelling transport dynamics ofcontaminated sediments in the headwater of a hydro-power plant at the Upper Rhine River”) to analyse thedynamics of erosion and sedimentation processes in theheadwater of a cross dam at the Upper Rhine. As the weiris operating only for flood management, a huge amountof sediment highly contaminated with the hexachloro-benzene (HCB) was deposited in the weir zone. Therefore,numerical simulations were performed by the authors todetermine the spatial and temporal distribution ofdeposited contaminated sediments.

I believe that this collection of papers points out theimportance of storage zones such as floodplains, groynefields, or locks and weirs as well as the hydrodynamic fac-tors for the transport behaviour of sediments in lowlandrivers. In my opinion, taking in account erosion thresh-old factors, historically contaminated sediments as amain part of the emission-immission situation withinthe catchment should gain more consideration on theirrisk for downstream abutter.

Kurt Friese Magdeburg, March 2006

References

F�rstner, U. (2002): Sediments and the European WaterFramework Directive. J. Soils Sed. 2, 54.

F�rstner, U. (2004): Traceability of sediment analysis. TrendsAnal. Chem. 23, 217–236.

F�rstner, U., Heise, S. (2006): Assessing and managing contami-nated sediments: Requirements on data quality – from mo-lecular to river basin scale. Croatica Chemica Acta 79, inpress.

F�rstner, U., Jirka, G. H., Lang, C., Meyer, E. I., Meyer-Reil, L. A.,Steinberg, C., Symader, W., Westrich, B. (2000): Significance ofsediments in aquatic eco-systems – interdisciplinary processstudies on fine sediment dynamics and pollutant mobilityin flowing waters [in German]. In: Advisory Board for the As-sessment of Chemicals. 8th BUA-Colloquium (Ed.): Assess-ment of Chemicals – Concepts for Sediments and MarineEcosystems. Gesellschaft Deutscher Chemiker (German Che-mical Society), Frankfurt/Main, GDCh-Monograph Vol. 17,pp. 75–109.

F�rstner, U., Heise, S., Schwartz, R., Westrich, B., Ahlf, W. (2004):Historical contaminated sediments and soils at the river ba-sin scale – examples from the Elbe River catchment area. J.Soils Sed. 4 (4), 247–260.

Friese, K., Miehlich, G., Witter, B., Brack, W., B�ttner, O., Gr�n-gr�ft, A., Kr�ger, F., Kunert, M., Rupp, H., Schwartz, R., van derVeen, A., Zachmann, D. W. (2000 a): Distribution and fate of or-ganic and inorganic contaminants in a river floodplain – re-sults of a case study on the river Elbe, Germany. In Wise, D. L.,Trantolo, D. J., Cichon, E. J., Inynag, H. I., Stottmeister, U. (Eds.):Remediation Engineering of Contaminated Soils. 2nd Edition.Marcel Dekker, New York, pp. 375–428.

Friese, K., Witter, B., Miehlich, G., Rode, M. (Eds.) (2000 b): Stoff-haushalt von Auen�kosystemen – B�den und Hydrologie,Schadstoffe, Bewertungen. Springer, Berlin.

Salomons, W., Brils, J. (Eds.) (2004): Contaminated Sedimentsin European River Basins. SedNet European Sediment Re-search Network. EC Contract No. EVK1-CT-2001-20002. TNO,Den Helder, NL.

Westrich, B., F�rstner, U. (2005): Sediment dynamics and pollu-tant mobility in rivers (SEDYMO). Assessing catchment-wideemission-immission relationships from sediment studies.Soils Sed. 5, 197–200.

i 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www3.interscience.wiley.com/cgi-bin/jhome/5007772