The Difficult Assessment of Heavy Metal Contamination of Soils and Plants in Elbe River Floodplains

© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

F. Krüger et al.436 Acta hydrochim. hydrobiol. 31 (2003) 4–5, 436–443

DOI 10.1002/aheh.200300495

The Difficult Assessment of Heavy MetalContamination of Soils and Plants in Elbe RiverFloodplains

Frank Krügera,Alexander Gröngröftb

a ELANA Boden WasserMonitoring,Dorfstr. 55,39615 Falkenberg, Germany

b Universität Hamburg,Institut für Bodenkunde,Allende-Platz 2,20114 Hamburg, Germany

Correspondence: F. Krüger, E-mail: [email protected]

The investigations on total sums of heavy metals indicated that topsoils in the floodplains inthe German part of the river Elbe are in part markedly enriched.The contamination exceedsthe action values of the Federal Soil Protection and Contaminated Site Ordinance. Lookingon known concentrations of heavy metals in the pasture vegetation, however, threshold val-ues for fodder are not exceeded in most cases. As livestock takes up a part of contaminantsby inhalation and ingestion of soil particles and as the contamination in the vegetation is var-iable in space and time, the actual risk of heavy metal transfer in the food chain has needs tobe studied.

Die schwierige Bewertung der Schwermetallbelastung von Böden und Pflanzenin den Elbauen

Die Schwermetallbelastung der aktuell überfluteten Auenböden entlang der Elbe istteilweise derartig hoch, dass Maßnahmenwerte für die Grünlandnutzung der Bundes-Bo-denschutzverordnung überschritten werden. Andererseits liegen die Metallgehalte in derVegetation meistens unterhalb der Grenzwerte der Futtermittelverordnung. Dabei wird abernicht berücksichtigt, dass Weidevieh einen erheblichen Belastungsanteil durch Inhalationund Ingestion aufnimmt. Daher kann das Risiko des Schwermetalltransfers in die Nahrungs-kette nicht abschließend beurteilt werden und bedarf näherer Untersuchung.

Keywords: Vegetation, Pollution, Flood, Transfer

Schlagwörter: Elbe, Schwermetall, Vegetation, Boden, Aue


Heavy Metals in Elbe Floodplain Soils and PlantsActa hydrochim. hydrobiol. 31 (2003) 4–5, 436–443 437

Table 1: Percentiles of the heavy metal and arsenic contents of German Elbe River topsoils (exceedance of action values in bold).

Kennzahlen der Schwermetall- und Arsengehalte von Oberböden im deutschen Elbeabschnitt (Überschreitungen von Maßnah-menwerten in Fettsatz).

As Cd Cr Cu Hg Ni Pb Zn

Numerical value 122 199 202 205 184 189 205 205Unit µg/g µg/g µg/g µg/g µg/g µg/g µg/g µg/gMinimum 3 0.1 10 8.8 0.2 7 11 3410% 20 0.8 32 26 1 18 42 13525% 31 1.6 52 54 1.7 27 74 264Median 50 3.1 82 96 3.5 38 110 482Mean 64 4.4 98 117 5.6 41 126 58575% 91 5.7 126 156 8 48 160 74990% 130 9.4 185 252 13 65 224 1273Maximum 200 30 355 540 31 140 370 2500Action value for grassland [10] 50 20 – 1300; 200 for

sheep grazing2 1900 1200 –

1 Soils and sediments

In the past a number of studies have investigated the heavymetal contamination of floodplain soils along the Elbe River(ARGE GFE GmbH et al. [1], Köster and Merkel [2], Krüger [3,4], Küster [5], Landesamt für Umweltschutz Sachsen-Anhalt[6], Meissner et al. [7], Miehlich [8], Müller [9]). The investiga-tions showed that the topsoils are partly extremely enrichedwith heavy metals. Table 1 summarizes the contents of thetopsoils in the German part of the river (without tidal influ-ence) and gives percentiles of the heavy metal distribution incomparison to action values of the Federal Soil Protectionand Contaminated Site Ordinance [10].

The exceedance of action values for grasslands varies be-tween metals. Regarding arsenic (As), one half of all exam-ined samples shows transgressions of the action values. Forcadmium (Cd) only three of all samples (1.5%) exceeded theaction value. On 10...25% of the investigated sites grazing bysheep would not be permissible because of high copper (Cu)contents. The level of the mercury (Hg) load of the floodplaintopsoils is so high that at about 70% of all sites the actionvalue is exceeded.

The contamination along the Elbe River floodplains is notconstant. The example of Hg in Figure 1 shows that from theCzech border (km 0) to the mouth of the river Mulde (km 259)a maximum contamination of w (Hg) = 5 µg/g was detected.The enormous heavy metal load of Mulde (Elbe river km 259)and Saale (Elbe river km 290), however, have led to a muchhigher pollution of the Elbe River meadows situated down-stream with maximum values up to w(Hg) = 30 µg/g.

Dehner et al. [11] found highest concentrations of heavy met-als downstream of Magdeburg city (about km 330). The mix-ture of particles leads to a decrease of maximum values be-tween km 500 and km 600.

The monitoring of the metal contents in suspended matter bythe ARGE-Elbe [12] revealed a clear reduction of the Hg con-tents over the last two decades (Fig. 2) starting with annualmeans of w(Hg) = 55 µg/g in 1984 and ending with w(Hg) =3...5 µg/g in 200. With respect to the decline of river pollutionthe contamination of the meadow soils has to be interpretedas relictic. In comparison to the action values of the FederalSoil Protection and Contaminated Site Ordinance [10] the ac-tual Hg contents in suspended matter are still so high that cur-rent and future sedimentation will keep contamination of thealluvial soils above action values. As Figure 3 shows, thesources of river pollution with Cd are different from those re-sponsible for Hg. Also, the temporal development of Cd con-taminations linked to suspended matter is different from Hg(Fig. 3). A clear decrease can be observed during the last10 years so that the Cd contents of the fresh sediments nowlie below the action values (mean values in 2000: w(Cd) =6.7...8.5 µg/g). The current As (about w(As) = 30 µg/g in2000) and Cu (about w(Cu) = 110...120 µg/g in 2000) con-tents of suspended matter also lie below action values, sothat an improvement of topsoil quality concerning As and Cucan be expected in the long term.

2 Plants

The metal uptake by plants is so complex that it is always dif-ficult to find correlative interrelationships between soil and



Fig. 1: Hg contents of Elbe Riverfloodplain topsoils.

Quecksilbergehalte in Oberbödender Elbauen.

Fig. 2: Development of Hg contentsof particulate matter 1984–2000(ARGE-Elbe [12]).

Entwicklung der Quecksilbergehaltein schwebstoffbürtigen Sedimenten1984–2000.

Fig. 3: Development of Cd contentsof particulate matter 1984–2000(ARGE-Elbe [12]).

Entwicklung der Cadmiumgehalte inschwebstoffbürtigen Sedimenten1984–2000.



Table 2: Percentiles of the heavy metal and arsenic contents of German Elbe River green country vegetation (exceedance ofthreshold values in bold).

Kennzahlen der Schwermetall- und Arsengehalte der Grünlandvegetation im deutschen Elbeabschnitt (Überschreitungen vonGrenzwerten in Fettsatz).

As Cd Cr Cu Hg Ni Pb Zn

Numerical value 102 133 66 68 118 45 134 67Unit µg/g µg/g µg/g µg/g µg/g µg/g µg/g µg/gMinimum 0.01 0.04 0.2 0.8 0.01 1.1 0.06 2210% 0.1 0.1 0.7 9 0.01 2 0.25 4625% 0.2 0.2 1.5 11 0.02 2.2 0.3 70Median 0.3 0.4 2.6 13.4 0.03 3 0.5 109Mean 0.5 0.5 3.7 13.8 0.15 3.9 1.30 13475% 0.6 0.6 3.8 16 0.1 4.2 1.23 13690% 1 0.9 5.6 20 0.6 6.6 3 180Maximum 5.7 3 30 27 1.6 13.5 18.2 705Threshold value of food ordinancefor livestock [13]

2 1 0.1 40

plant contaminations.The grassland plant communities in thealluvial plains differ from each other especially in relation tohydrologic conditions. As plant contents vary with plant organand time, it would be necessary to repeatedly examine thesame species or the same species composition on varioussites and to compare the results with plant available soil con-centrations. As the sampling of plants and soils in most caseshas not been conducted in the same position and at the sametime, a comparison of both data sets is possible only with re-spect to statistical values. The pasture plant contaminationsare assessed with respect to the threshold values of the foodordinance for livestock [13]. However, the ordinance stipu-lates the sampling of a mixture of species and organs repre-sentative for the fodder vegetation.

In flooded areas the particular metal enrichment on plant sur-faces has to be taken into account in addition to the metal up-take by roots.The quantity of dry matter- and metal-sedimen-tation is dependent on the certain flood event. Data concern-ing plant metal load following strong flood events could not befound in the literature.Table 2 gives percentiles for metal con-tents in plants according to Köster and Merkel [2], Krüger [4],Küster [5], Landesamt für Umweltschutz Sachsen-Anhalt [6],LUFA [14], and Miehlich [8]. For the metals As, Cd, and Hg thedistribution of plant contamination along the Elbe River isshown in Figures 4–6.

There is only a limited correlation between soil and plant con-tamination. In the case of As three samples (3%) exceed thethreshold values of the fodder ordinance, in case of Cd lessthan 10%, and for Hg almost 25%. For Pb no exceedance

was found. The exceedance of food ordinance values oc-curred mostly between Elbe river kilometers 400 and 600.

Figure 7 shows the correlation of plant and topsoil Hg forsamples retrieved from the same position. For the elementsAs, Hg, and Pb no relationship between soil and plant loadwas found. Heavy metal enrichment in plants occurs on soilswith a high heavy metal load as well as on soils with low pollu-tion. This depends on the variable metal uptake of recordedplant species and compositions within one as well as in com-parison to several vegetation periods. Additionally, the lack ofcorrelation may be caused by plant contamination from par-ticulate matter and by the differences in the mobility of themetals due to varying pH and Eh values of the soils.

In contrast to As, Hg, and Pb, the root uptake for Cd has to betaken into account. The availability of soil Cd is comparablyhigh. Within the river plain soils can be shown that the plantavailable fraction depends on the pH value of the soil (Fig. 8).Furthermore, a weak correlation can be seen for the plantavailable Cd contents in the soils and the contents in the veg-etation (Fig. 9).The sediment-born fraction of the heavy metalload can hardly be assessed.

Regarding Cd, measurements below the action value of thesoil protection order [10] of 20 µg/g in the soil is no guaranteethat fodder concentrations will as well fall below the thresholdvalues [13]. It can be assumed that an exceedance of thresh-old values for fodder is possibly independent from the Cd con-tamination of the soil if the pH value is lower than 6 (Fig. 10).Cd is the most mobile element, its availability for plants is



Fig. 4: As contents in pasture vegeta-tion along the river Elbe.

Arsengehalte der Grünlandvegeta-tion entlang der Elbe.

Fig. 5: Cd contents in pasture vege-tation along the river Elbe.

Cadmiumgehalte der Grünlandvege-tation entlang der Elbe.

Fig. 6: Hg contents in pasture vege-tation along the river Elbe.

Quecksilbergehalte der Grünland-vegetation entlang der Elbe.



Fig. 7: Hg contents in Elbe River top-soils and plants.

Quecksilbergehalte von Oberbödenund Pflanzen der Elbe.

Fig. 8: Plant available Cd contents ofElbe River topsoils and pH values.

Pflanzenverfügbare Cadmiumge-halte und pH-Werte von Oberbödender Elbe.

Fig. 9: Plant available Cd contents ofElbe River topsoils and Cd contentsin plants.

Pflanzenverfügbare Cadmiumge-halte von Oberböden der Elbe undCadmiumgehalte in Pflanzen.



Fig. 10: Cd contents of pasture vege-tation and pH values of Elbe Rivertopsoils.

Cadmiumgehalte der Grünlandvege-tation und pH-Werte von Oberbödender Elbe.

regulated by the pH value and the Cd pollution is high enoughto cause a Cd enrichment in the pasture vegetation. Becauseof this the soil pH values along the Elbe River are very impor-tant for an evaluation of the soil contamination. Downstreamthe mouths of the Mulde and the Saale rivers pH values below4 were measured.

3 Conclusions

The evaluation of the metal contamination of the Elbe Riverfloodplains by two methods – threshold values of the food or-dinance for livestock and action values of the the soil protec-tion order – gives quite different results. Threshold values forfodder are exceeded although the soil contamination is low(Cd) and vice versa (As, Hg).

When the action values of the soil protection order were fixed,it was considered that the grazing cattle takes up a part ofcontamination directly by inhalation and ingestion of soil par-ticles, as it was already shown by Thornton et al. [15]. Al-though the vegetation load is below the fodder threshold val-ues a contamination and enrichment in the human food chaincannot be excluded by animals grazing on the contaminatedgrounds. The variation of plant contamination, howevermakes clear that the problem “fodder threshold value exceed-ance” could be solved by rarefaction with regard to the metalsdiscussed here.

This applies at least to the green fodder which is cut twice perannum and transported out of the flooded areas. Because ofthe thinning effects the production of hay in the Elbe Riverfloodplains seems to be possible. The grazing cattle couldpermanently be contaminated by soil particles inherent to

the vegetation. The exceedance of action values on largeareas shows the necessity of further investigations regardingthe land use by the fact that

– vegetation load is investigated directly after high floodevents (inherent load),

– soil particle uptake of grazing cattle is investigated,– the heavy metal enrichment in the cattle and its products is

examined.

For the future open questions have to be answered by re-search activities: On the one hand concerning the soil-plantmetal transfer and on the other hand concerning the livestockand product contamination. Field studies at the Elbe Rivershould be placed downstream as well as upstream of theMulde and Saale rivers mouths. Because of the fact that in-toxications and losses of animals are not known it is obviouslyclear that not acute toxic risks have to be estimated but thechronic ones – for livestock as well as for humans.

References

[1] ARGE GFE GmbH, CUI mbH, und TÜV Ostdeutschland

Sicherheit und Umweltschutz GmbH: Bodenzustand in den

Flußauen des Landes Sachsen-Anhalt. Raw data from the

Landesamt für Umweltschutz, Halle, 1997.

[2] Köster, W., Merkel, D.: Schwermetalluntersuchungen land-

wirtschaftlich genutzter Böden und Pflanzen in Niedersach-

sen. Landwirtschaftskammer Hannover, 1985.

[3] Krüger, F.: Unpublished Hg-measurements of topsoils. 1997.

[4] Krüger, F.: Unpublished data of soils and plants. 2001.



[5] Küster, J.: Bestimmung der pflanzenverfügbaren Schwer-

metallgehalte in ausgewählten Elbvordeichsböden unter

besonderer Berücksichtigung des Transfers Boden/Pflanze.

Diplomarbeit, Universität Hamburg, 1996.

[6] Landesamt für Umweltschutz Sachsen-Anhalt: Unpublished

measurements of Elbe river floodplains soils and plants.

2000.

[7] Meissner, R., Guhr, H., Rupp, H., Seeger, J., Spott, D.:

Schwermetallbelastung von Böden und Elbsedimenten in

ausgewählten Gebieten Ostdeutschlands. Z. Kulturtech.

Landentwickl. 35, 1–9 (1994).

[8] Miehlich, G.: Schwermetallanreicherung in Böden und

Pflanzen der Pevestorfer Elbaue. Abh. Naturwiss. Verein

Hamburg 25, 75–89 (1983).

[9] Müller, D.: Erfassung und Bewertung von Bodenbelastungen

durch anorganische Schadstoffe im Überflutungsgebiet

oberes Elbtal. Diplomarbeit, Martin Luther Universität Halle

Wittenberg, 1995.

[10] Bundes-Bodenschutz- und Altlastenverordnung

(BBodSchV) vom 12. Juli 1999. Bundesgesetzblatt I 1999,

1554 (1999) [Federal Soil Protection and Contaminated Site

Ordinance from the 12.07.1999].

[11] Dehner, U., Feldhaus, D., Villwock, G.: Zur Kennzeichnung

von Schwermetall-Hintergrundgehalten in Auenböden in

den Flusssystemen der Saale und mittleren Elbe. In: Friese,

K., Witter, B., Miehlich, G., Rode, M. (Eds.): Stoffhaushalt

von Auenökosystemen – Böden und Hydrologie, Schadstof-

fe, Bewertungen. Springer, Berlin, 2000, pp. 227–236.

[12] ARGE-Elbe: Tables of Measurements. Arbeitsgemeinschaft

für die Reinhaltung der Elbe, Hamburg, 1984–2000.

[13] Neufassung der Futtermittelverordnung (FutMV) vom 23.

November 2000. Bundesgesetzblatt I 2000 (51), 1605

(2000).

[14] LUFA: Unpublished data from the official food ordinance of

the Regierungspräsidium Halle. 1999.

[15] Thornton, J., Abrahams, P.: Soil ingestion – a major pathway

of heavy metals into livestock grazing contaminated land.

Sci. Total Environ. 28, 287–294 (1983).

[Received: 23 September 2002; accepted 12 May 2003]

The Difficult Assessment of Heavy Metal Contamination of Soils and Plants in Elbe River Floodplains

Documents

Transcript of The Difficult Assessment of Heavy Metal Contamination of Soils and Plants in Elbe River Floodplains