depth distribution of chlorinated and polycyclic aromatic hydrocarbons in floodplain soils of the...

Acta hydrochim. hydrobiol. 31 (2003) 4–5, 411–422 411

© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimDOI 10.1002/aheh.200300501

Depth Distribution of Chlorinated and PolycyclicAromatic Hydrocarbons in Floodplain Soils of theRiver Elbe

Barbara Wittera,b,Marcus Winklera,Kurt Friesea

a UFZ – Center forEnvironmental ResearchLeipzig-Halle,Department of Inland WaterResearch Magdeburg,Brückstr. 3a,39114 Magdeburg, Germany

b Present address:Otto-von-Guericke-University ofMagdeburg,Medical FacultyLeipziger Str. 44,39120 Magdeburg, Germany

Correspondence: B. Witter, E-mail: [email protected]

Depth profiles of various organic micropollutants were measured in floodplain soils of theriver Elbe, Germany. The study area lies in the former East Germany (GDR) and displayselevated concentrations of pesticides and polycyclic aromatic hydrocarbons. Depth distribu-tions were found to vary at different sampling points and among the individual compounds,which could only partly be explained by comparing normalized concentrations (organic car-bon). Metabolization, mobilization, and effects of sedimentation and erosion also need to betaken into account to understand the contaminant patterns found in the different profiles.

Tiefenverteilung von chlorierten und polycyclischen aromatischenKohlenwasserstoffen in Auenböden der Elbe

Es wurden Tiefenverteilungen verschiedener organischer Spurenstoffe in Auenböden derElbe bestimmt. Das Untersuchungsgebiet befindet sich am Mittellauf des Flusses und zeigterhöhte Konzentrationen an Pestiziden und polycyclischen aromatischen Kohlenwasser-stoffen. Unterschiedliche Tiefenverteilungen wurden an den verschiedenen Probenahme-stellen und für die verschiedenen Verbindungen gefunden, die sich nur teilweise nach einerNormierung auf den organischen Kohlenstoffgehalt erklären lassen. Metabolisierung, Mobi-lisierung sowie Sedimentations- und Erosionseffekte müssen zusätzlich berücksichtigt wer-den, um die unterschiedlichen Schadstoffmuster zu verstehen.

Keywords: Organic Micropollutant, Pesticide, Sediment, Depth Distribution, PAH, DDT

Schlagwörter: Organischer Spurenstoff, Pestizid, Sediment, Tiefenverteilung, PAK, DDT

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

B. Witter et al.412 Acta hydrochim. hydrobiol. 31 (2003) 4–5, 411–422

Fig. 1: Location of investigationareas.

Lage der Untersuchungsgebiete.

1 Introduction

The contamination of floodplain soils has recently begun toattract growing attention; previously, interest was mainly fo-cused on river water, sediments, and various types of aquaticanimals [1–3].Yet, while polluted rivers slowly become clean-er once the source of pollution has been removed, floodplaincontamination persists for much longer because contaminat-ed sediments, once deposited in a floodplain are not removedeasily after they have been covered by vegetation. Flood-plains can be regarded as a huge depot of anthropogenic pol-lutants that may assume a new level of significance if they areredistributed, for example by serious flooding events [4] orhuman activity.

Sediments in the river Elbe show the results of several dec-ades of uncontrolled pollution of the river by industry in theformer states of East Germany and Czechoslovakia. Howev-er, the situation is far more perceptible in the soils of the Elbemeadows [5, 6].

The Elbe is the only river in Germany that still has its originalmeadow forests to a certain extent. These beautiful land-scapes with their great diversity of fauna and flora are protect-ed as national parks and natural reserves in all the Germanfederal states where the Elbe flows. About 84 % of the areasalongside the river are protected on either one or both

sides [7]. During the last few years several large projects onthe formation of soils, hydrology, and the input, distributionand fate of inorganic and organic pollutants have been con-ducted on the Elbe floodplains. An overview on recent flood-plain research in Germany was given by Friese et al. [6].

This paper presents some findings concerning the depth dis-tribution of organic micropollutants obtained during a Russo-German project ‘Impact of high flood events on the pollutionof agricultural soils in the flooding area of the rivers Oka andElbe’. Investigations into the depth distribution of organic con-taminants in floodplain soils are few and far between [8, 15].Some additional information is available in the work of Frieseet al., albeit only in the German [6].

2 Study area

The area under investigation is in the German state of Saxo-ny-Anhalt, near the town Wittenberge between Elbe kilometer435 and 440 in the village of Schönberg (Fig. 1). Some com-parisons are drawn with the meadow of Pevestorf in LowerSaxony, which is located a few kilometers downstream (km484–486) and the concentrations in suspended particulatematter (SPM), sampled in Magdeburg, the capital of Saxony-Anhalt.


CHCs and PAHs in Floodplain SoilsActa hydrochim. hydrobiol. 31 (2003) 4–5, 411–422 413

Fig. 2: Photos of the profiles underinvestigation SD 45 and SD 48.

Photos der untersuchten ProfileSD 45 und SD 48.

3 Materials and methods

3.1 Sampling

In order to gain an impression of the spatial distribution of pol-lutants in the floodplain, two transects through the wholemeadow, from the dike to the bank, were selected and topo-graphically mapped out. Soil properties were mapped alongthese transects (about 100 profiles [10]) and at selectedpoints the levels of heavy metals were determined in the up-per soil layers [11]. Six positions showing elevated concentra-tions of heavy metals were selected for more detailed analy-sis, including the determination of pollution with depth notonly for inorganic but also for organic contaminants.

The profiles were dug out to a depth of 1.5 m so that samplingcould take place directly from the open profile into glass bot-tles with stainless steel spatulas. The samples were kept fro-zen until analyzed. Sample preparation included homogeni-zation, sieving (< 2 mm), and freeze drying.

3.2 Description of the profiles

All the profiles studied except one lie in valley positions andare therefore potential accumulation sites. At the bottom ofthe profiles, meadow loam is occasionally found –, a specificmaterial deposited during the Middle Ages as a result of the

intensive clearing of forests at that time. Younger depositsmostly consist of sandy materials. Only in areas where theflow speed of the water during flooding is reduced are moresludgy materials found, i.e., in small valleys or hollows in themeadow’s topography.

Four profiles (SD04, SD32, SD42, NK03) were only investi-gated with a fast survey technique and are not describedhere in more detail because they only showed moderatelevels of contamination. The profile SD 45 is classified as a‘Gley-Vega’ (according to the German soil classification sys-tem [12]), consisting of meadow loam above meadow sand.It is in a position of recent sludge sedimentation. Below20 cm the organic carbon content (OC) is only about 1 %(Table 6). Heavy metal concentrations decrease withdepth.

SD 48 lies in a flood channel behind the first levee. The pro-file has many thin layers whose grain size distribution variesbetween sandy and sludgedominated materials. The input ofrecent materials there is expected to be high. It is classifiedas a Gley-Paternia [12] consisting of meadow sand andmeadow sludge. Sand is the predominant material, whilethe OC varies greatly, reaching 12% in a small layer be-tween 30 cm and 40 cm (see also Table 6). The sludgy hori-zons have elevated heavy metal concentrations. In order toobtain an impression of the two profiles, photos of both areshown in Figure 2. Some properties are summarized inTable 1.



Table 1: Properties of profiles SD 45 and SD 48 [10].

Eigenschaften der Profile SD 45 und SD 48 [10].

Depthcm

Sand%

Znmg/kg

Pbmg/kg

SD 45 0...20 19 776 19020...60 18 225 7660...80 89 69 24

80...110 37 142 45

SD 48 0...30 90 208 5230...55 67 529 12855...80 91 87 4580...90 62 120 83

90...110 97 57 29

Table 2: Compounds under investigation.

Untersuchte Verbindungen.

ChlorinatedhydrocarbonsCHCs

DDX (p,p�-DDE, p,p-DDD, p,p�-DDT,o,p�-DDE, o,p-DDD)hexachlorocyclohexane-isomers (α-, β-,γ-, δ-HCH)chlorinated aromatics (hexachlorobenzeneHCB, pentachlorobenzene QCB, octachlo-rostyrene OCS)polychlorinated biphenyls (PCB 28, 52,101, 138, 153, 180)

PolycyclicaromatichydrocarbonsPAHs

as recommended for investigations bythe US EPA (Environmental ProtectionAgency):naphthalene (Naph), acenaphthylene(AcYlen),acenaphthene (Acen), fluorene (Fluo),phenanthrene (Phen), anthracene (Anth),fluoranthene (FluA), pyrene (Pyr), benz-(a)anthracene (BaA), chrysene (Chry),benzo(b)fluoranthene (BbF), benzo(k)-fluoranthene (BkF),benzo(a)pyrene (BaP), dibenz(a,h)anthra-cene (DahA), benzo(ghi)perylene (BghiP),indeno(1,2,3-cd)perylene (IncdP)

Synthetic muskfragrances

musk ketone (1-tert-butyl-3,5-dimethyl-2,6-dinitro-4-acetylbenzene), ADBI (4-acetyl-1,1-dimethyl-6-tert-butylindane),AHTN (7-acetyl-1,1,3,4,4,6-hexamethyl-tetralin),HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8,-hexamethylcyclo-penta-(g)-2-benzopyran)

3.3 Analysis

The samples were investigated for chlorinated hydrocarbons(CHC), polycyclic aromatic hydrocarbons (PAH), and artificialmusk fragrances (Table 2). Chlorinated compounds were an-alyzed by gas chromatography with electron capture detec-tion (GC-ECD) after extraction with supercritical carbon diox-ide (SFE). The other compounds were analyzed by gas chro-matography-mass spectrometry (GC-MS) after soxhlet ex-traction (16 h, dichloromethane). SFE was carried out by twodifferent methods: first with a rather fast technique withoutusing any modifier to obtain cleaner extracts that could beanalyzed without a clean-up procedure (method A); after-wards we used a stronger method (method B) with 5 % meth-anol in the fluid to achieve more complete extraction with ayield comparable to soxhlet extraction. This entailed clean-upwith silica and copper powder. Details are contained in Table3. For more details of analysis see Witter et al. [8] for theCHCs and Winkler et al. [13] for the PAHs and musk fra-grances. Additionally, the OC was determined using a com-bustion technique.

4 Results and discussion

4.1 Preliminary survey

In order to gain an overview of the contamination of theSchönberg meadow, six profiles that showed elevated levelsof heavy metals were selected for organic compound analy-sis. The extractions were performed with the SFE method Aon samples representing the depth between 0 cm and 60 cm.Results for selected compounds are given in Table 4.

As can be seen, most profiles show levels decreasing withdepth, with contents in the top sample ranging from 66 to436 µg/kg for HCB and from 19 to 460 µg/kg for p,p�-DDD.Only two profiles show a different picture. SD 45, which hasthe highest levels for HCB, shows the maximum for this com-pound at a depth of 10…20 cm. HCB is the main contaminantin some but not all profiles. In SD 48, HCB as well as the pes-ticide p,p�-DDT and the pesticiderelated compounds p,p�-DDD and β-HCH show a maximum at a depth of 30…40 cm.Here HCB is clearly of less significance than the other com-pounds.

The concentrations reported should be carefully interpreted,because of the greater uncertainties of the data obtainedsolely by our fast survey method A. In some cases co-elutionof substances in the chromatogram might have appeared, re-sulting in excessive concentrations. In order to obtain a moreaccurate impression, SD 45 and SD 48 were investigated fur-ther with the SFE method B (providing a more exhaustive ex-traction), as well as for other compounds, PAHs and muskfragrances.



Table 3: Conditions of supercritical fluid extraction (SFE).

Bedingungen für die überkritische Fluidextraktion (SFE).

patm

T°C

ϑmin

FlowmL/min

Methanol(modifier)

Method AStatic extraction 450 100 20 –Dynamic extraction 450 100 45 1.5 –

10 mL plastic tubes, trapping in hexane (10 mL, 0 °C), 2 g sample

Method BStatic extraction 450 100 20 5 %Dynamic extraction 450 100 30 1 5 %

2 mL steal tubes, trapping in acetone (15 mL, 0 °C), 0.5 g sampleremoving of sulfur by the addition of copper powder [14]

Table 4: Contents of chlorinated hydrocarbons in the Schönberg meadow – preliminary results.

Gehalte an chlorierten Kohlenwasserstoffen in der Schönberger Aue – Voruntersuchung.

µg/kg Depth/cm

HCB β-HCH p,p�-DDD

p,p�-DDT

µg/kg Depth/cm

HCB β-HCH p,p�-DDD

p,p�-DDT

SD 04 0...10 145 38 286 0 SD 45 0...10 436 135 289 43210...20 6 0 3 0 10...20 753 24 176 15820...30 2 1 2 0 20...30 287 0 11 630...40 2 1 2 0 30...40 43 0 2 140...50 3 1 2 0 40...50 10 0 2 150...60 2 0 2 0 50...65 4 0 2 0

SD 32 0...10 100 3 19 32 SD 48 0...5 66 15 33 1710...20 54 0 4 8 5...10 32 8 21 3020...30 30 0 1 2 10...15 41 13 28 1630...40 8 0 2 0 15...20 57 6 22 1640...50 3 0 0 1 20...30 96 14 34 2250...60 7 0 0 1 30...40 238 815 296 1693

40...50 60 19 105 2250...60 60 18 81 11

SD 42 0...15 290 92 460 90 NK 03 0...10 321 84 150 015...25 287 24 35 8 10...20 161 36 97 1625...35 8 0 4 0 20...30 7 0 3 035...45 3 0 0 0 30...40 4 0 0 045...55 0 0 0 0 40...50 2 0 1 155...65 0 0 1 0 50...60 2 0 1 0



4.2 Depth profiles

The profiles SD 45 and SD 48 were investigated further withthe SFE method B for CHCs and with Soxhlet extraction forPAHs and synthetic musk fragrances.

The profiles for CHCs are shown in Figure 3. They generallyconfirm the results from the preliminary survey.The profile SD45 shows decreasing concentrations by depth for most com-pounds except the chlorinated aromatics, which have a maxi-mum peak between 10 cm and 20 cm. Levels reach about 850µg/kg for HCB, around 400 µg/kg for p,p�-DDT and p,p�-DDD,and 130 µg/kg for β-HCH. PCBs show a completely differentpicture with nearly equal contents between 0 cm and 40 cm(sum of the six compounds studied about 120 µg/kg), a breakof 40 cm with no PCBs, and again certain amounts between80 cm and 105 cm.

Among the DDX compounds, p,p�-DDT and p,p�-DDD havequite similar concentrations, with o,p�-DDD making up about1/4 to 1/5 of all DDX. Of the HCH isomers, the most unpolarisomer, β-HCH, was found at the highest level (up to 130µg/kg), followed by α-HCH and, in the deeper samples, alsoby the most polar isomer γ-HCH.

Profile SD 48 shows something like a pesticide layer between30 cm and 40 cm with especially large amounts of the non-metabolized p,p�-DDT and β-HCH. However, the high con-centration of β-HCH found in the preliminary survey could notbe confirmed. This might have been an analytical artifact dueto co-elution of substances in the chromatogram. In this layerthe non-metabolized p,p�-DDT is clearly the dominating com-pound among the DDX, with a content of about 1100 µg/kg.

β-HCH reaches a level of 240 µg/kg and is the dominant iso-mer in this depth layer; in the 10...15 cm sample, where wealso find elevated concentrations of HCHs, the α- and δ-iso-mers have similar concentrations. This first enrichment ofCHCs between 10...15 cm can be seen for the HCHs and forthe DDX as well, albeit to a smaller extent.

The chlorinated aromatics play a much less important rolehere compared to the profile SD 45. HCB is found with rough-ly 300 µg/kg in the top sample and again between 30 cm and40 cm; the other two compounds are virtually non-existenthere.The PCBs show a pattern comparable to the chlorinatedaromatics, with maxima in the top sample and for 30...40 cm(about 100 µg/kg in total).

The investigation of musk fragrances, included in the projectbecause of the relatively high levels in the river Elbe seston[13], only indicated contents in the range of the blank(10...20 µg/kg), whereas in Elbe seston levels reach up to800 µg/kg for AHTN and HHCB.

The profiles of five more important PAHs are shown in Figure4. The sum of these five compounds (phenanthrene, fluoran-thene, pyrene, benzo(a)anthracene, and benzo(a)pyrene)represents more than half of the sum of the 16 USEPA PAHs.The picture is similar to that of the DDX, with continuously de-creasing levels in SD 45 and with a pronounced maximum be-tween 30 cm and 40 cm in SD 48. All the results for PAHs aresummarized in Table 5.

The SD 45 profile shows much higher concentrations of PAHsin the top sample than are measured in actual seston sam-ples investigated in Magdeburg [13].The top sample of SD 48is less contaminated with levels equivalent to the seston.Looking at the CHCs we find the same effect: higher levels inSD 45, comparable results in SD 48.

4.3 Earlier investigations

To compare the results of the Schönberg meadow with previ-ous investigations, Figure 5 shows profiles obtained in 1994in the meadow at Pevestorf [8, 15]. It is a profile in a similarposition as SD 48, behind the first levee in an area of highsedimentation. We also find a maximum for the compoundsinvestigated at a certain depth, although in contrast to SD 48this depth varies for the different groups of substances.Thereis no particular contaminated layer in a small area; insteadthere are more or less continuously increasing concentra-tions down to 60 cm. We suspect this to be caused by mobili-zation. HCB is the compound with the highest levels of up to2200 µg/kg here, which is nearly 3 times the level of SD 45and about 9 times the level of SD 48 .

4.4 Patterns of CHCs and PAHs

In order to compare the variability of compounds in the differ-ent profiles and in certain layers, Figure 6 shows patterns ofselected CHCs and PAHs. As was already visible from theprofiles, the patterns of CHCs vary greatly between the differ-ent profiles, and also even in one profile over the differentdepth layers.

Two main patterns can be distinguished. Some soil sampleshave a pattern quite similar to the actual pattern in Elbe ses-ton (average of 40 samples (1996/1997); Pev. 50...60 cm,SD 45 10...20 cm, SD 48 0...5 cm), where HCB is the pre-dominant component with a share of more than 50%.

Pev. 30...40 cm and SD 48 30...40 cm show a different pic-ture: a relatively larger amount of p,p�-DDT and p,p�-DDD.The main difference between these two is that in SD 48 morenon-metabolized DDT is found, while in Pevestorf DDD andDDT occur in nearly equivalent concentrations. The degrada-tion of CHCs hence varies between the different soils investi-gated.



Fig. 3: Depth profiles of CHCs in the investigation area “Schönberg”.

Deich-Tiefenprofile der CHCs im Untersuchungsgebiet „Schönberg Deich“.



Fig. 4: Depth distribution of selected PAHs in the investigation area “Schönberg Deich”.

Tiefenprofile ausgewählter PAK im Untersuchungsgebiet „Schönberg Deich“.

Table 5: PAHs contents in the Schönberg meadow.

PAK-Gehalte in der Schönberger Aue.

SD 45 0...10 ...20 ...30 ...40 ...50 ...65 ...80 ...90 ...105 ...115µg/kg cm cm cm cm cm cm cm cm cm cm

Naph 383 117 39 9 2 4 2 3 3 3Acen 127 58 6 1 – – – – – –AcYlen 82 40 12 11 6 10 8 4 5 4Fluo 157 71 7 2 – – – – – –Phen 1934 1295 174 40 10 15 13 11 9 18Anth 629 330 15 – – – – – – –FluA 3097 1875 246 40 9 14 17 18 15 23Pyr 2424 1401 201 34 9 12 12 12 12 16BaA 1818 1128 148 25 5 7 7 4 1 6Chry 1711 1091 157 24 6 6 7 3 2 6BbF + BkF 1248 866 149 28 6 6 6 3 2 3BaP 1358 889 119 20 3 4 4 1 – 2DahA 152 145 19 – – – – – – –IncdP 875 707 135 22 – – 3 – – –BghiP 682 557 112 20 – 4 4 – – –

SD 48 0...5 ...10 ...15 ...20 ...30 ...40 ...50 ...60 ...65 ...75 ...85 ...95 ...105µg/kg cm cm cm cm cm cm cm cm cm cm cm cm cm

Naph 27 25 95 81 145 197 56 41 26 37 28 26 –Acen 12 4 17 11 18 177 14 13 6 6 – – –AcYlen 13 10 19 20 15 49 16 18 2 4 – – –Fluo 25 9 21 28 24 126 15 14 6 – – –Phen 269 159 358 394 515 2131 349 274 61 82 46 26 12Anth 42 17 47 57 109 630 48 36 14 14 8 – –FluA 282 158 321 422 606 3409 332 351 133 129 83 36 15Pyr 247 124 247 375 514 2527 260 297 99 93 75 28 17BaA 208 95 216 302 391 2040 217 259 68 56 33 15 –Chry 189 89 184 275 313 1655 227 245 117 103 55 18 –BbF + BkF 187 82 167 242 271 1323 201 246 92 83 47 19 –BaP 204 75 169 289 278 1514 157 199 71 64 42 13 –DahA 24 14 20 42 39 200 33 40 20 – – – –IncdP 148 70 135 226 235 1077 160 224 75 81 50 18 –BghiP 122 62 121 201 217 858 139 196 79 72 43 18 –



Fig. 5: Depth profiles in the Elbe floodplain near Pevestorf [8, 15], observe different scaling!

Tiefenprofile in der Elbaue nahe Pevestorf [8, 15].

Fig. 6: Patterns of selected CHCsand PAHs.

Muster ausgewählter CHC undPAK.



Table 6: Organic carbon content in profiles SD 45 and SD 48.

Gehalt an organisch gebundenem Kohlenstoff in den Profilen SD 45 und SD 48.

SD 45 0...10 ...20 ...30 ...40 ...50 ...65 ...80 ...90 ...105 ...115mg/kg cm cm cm cm cm cm cm cm cm cm

Organiccarbon

103 54 23 13 11 4 4 6 5 <0.1

SD 48 0...5 ...10 ...15 ...20 ...30 ...40 ...50 ...60 ...65 ...75 ...85 ...95 ...105mg/kg cm cm cm cm cm cm cm cm cm cm cm cm cm

Organiccarbon

75 20 26 20 29 122 21 15 4 5 5 3 1

Sample SD 45 0...10 cm has a pattern somehow between theother two groups. The shares of the individual CHCs variedgreatly over the deposition time recorded by these profiles.

The PAHs have quite similar distributions in all the samplesstudied, which indicates a constant source of pollution – eventhough the concentrations vary strongly.

4.5 Normalization on the organic carboncontent

To find out whether the organic carbon content (OC) helps toexplain the depth distribution, we analyzed all the samples ofthe profiles SD 45 and SD 48 for the OC (Table 6) and calcu-lated a normalization of the levels of contamination on theOC. In the profile SD 45 we found quite similar pictures with orwithout normalization, i.e., the OC alone does not explain thedistribution of contaminants. By way of example, Figure 7shows the normalized depth distribution for chlorinated aro-matics (QCB, OCS, and HCB) and for selected PAHs.

The strong enrichment of compounds in the layer between30 cm and 40 cm in SD 48 largely disappears after normali-zation on the OC.This is especially obvious for the DDX com-pounds (Figure 8). Here we now see a permanent alterationof higher and lower concentrations, which tallies with the visi-ble impression of the profile, where we can also see manysmall layers of more sandy and more sludgy material (seeFigure 2). Because of the low OC in the deeper layers below60 cm, we have an effect of an apparent increase in p,p�-DDTconcentration between 65 cm and 105 cm.

For the HCHs the effect is similar: there is still a smaller maxi-mum between 30 cm and 40 cm, and a more pronounced one

in the layer between 10 cm and 15 cm (data not shown). ThePAHs exhibit a slow increase from the surface until 20 cm, aplateau until 65 cm, and a slow decrease below 65 cm; seeFigure 8.

To obtain a mathematical proof for the relationship betweenthe pollutant concentration and the OC content, we calculat-ed Spearman rank correlations. The correlation coefficientsfor both the PAHs and the CHCs are around 0.8 with a signifi-cance level around 0.5, i.e., the correlation is mathematicallysignificant. In other words, the OC has at least some influenceon the distribution of organic contaminants in the samples in-vestigated.

5 Conclusions

All in all, the different results produce a complex picture. Wefind accumulations in both top samples and in deeper layers,the predomination of one compound or another, indications ofefficient metabolization and the absence of metabolization,patterns comparable to Elbe seston and quite different pat-terns, and the influence of the OC varying from weak tostrong.

One major conclusion to be drawn is that the most chief char-acteristic of Elbe meadow soils (and floodplain soils in gener-al) are their enormous variability and the presence andeclipsing of several different processes that are evidently notyet completely understood. We know that the pollution offloodplain soils depends greatly on the deposition of riversediment and so we can appreciate that contamination variesover depths since the amount of sedimentation varies fromone place to another within the floodplain. Moreover, changesin the meadow’s topography due to human activity or be-



Fig. 7: Depth distribution of selected compounds in SD 45 normalized on the OC. Content is given as microgram pollutant per gramC.

Tiefenverteilung ausgewählter Verbindungen in SD 45, normiert auf den OC. Schadstoffgehalt angegeben in Mikrogramm proGramm C.

Fig. 8: Depth distribution of selected compounds in SD 48 normalized on the OC. Content is given as microgram pollutant per gramC.

Tiefenverteilung ausgewählter Verbindungen in SD 48, normiert auf den OC. Schadstoffgehalt angegeben in Mikrogramm proGramm C.

cause of high flood events may change an area of sedimenta-tion into one of erosion and vice versa, resulting in a profileexhibiting an accumulation of older polluted sediments nowcovered by somewhat cleaner sandy material, or a sandy un-derground covered by younger sediments with perhaps a low-er degree of pollution and a different contaminant pattern.

Other aspects are of interest and are worthy of further investi-gation. It seems that in some places metabolization worksbetter than in other places (example p,p�-DDT → p,p�-DDD).Microbiologists need to study this in more depth.

The results obtained in Pevestorf during our first investigationof floodplain soils [8] indicated the possible vertical move-ment of certain substances, because maximum concentra-tions lay in different depth layers for different groups of com-pounds.This could not be confirmed in the meadow at Schön-berg. Why are some compounds apparently mobile in oneprofile and immobile in another with seemingly similar proper-ties?

Concentrations of organic pollutants are high in the flood-plain soils investigated. There is a great spatial variability



both vertically and horizontally. Our present level of knowl-edge does not allow us to tell conclusively what effects con-tamination at lower might have. Unfortunately there are al-most no investigations of depth profiles of organic micropol-lutants in other river floodplains. It remains a moot point forthe time being whether meadow soils are just a sink forpollutants and help to clean up the river over time, whetherthese depots are slowly leaking out into groundwater orriver water, or whether erosion and redistribution are themain risks [4]. Investigation of soil pore water should there-fore be the next step for Elbe floodplain research into organ-ic pollutants and we hope that these studies will be contin-ued.

Acknowledgements

The financial support kindly provided by the BMBF (GermanMinistry of Education and Research) is gratefully acknowl-edged (02-WT 9617/0). We would also like to thank Mrs.Stein and Mr. van der Heide for their laboratory assistance.

References

[1] Knauth, H.-D., Gandraß, J., Sturm, R.: Vorkommen und

Verhalten organischer und anorganischer Mikroverunreini-

gungen in der mittleren und unteren Elbe. Erich Schmidt,

Berlin, 1993.

[2] Franke S., Hildebrandt, S., Schwarzbauer, J., Link, M.,

Francke, W.: Organic compounds as contaminants of the

Elbe river and its tributaries. Fresenius J. Anal. Chem. 353,

39–49 (1995).

[3] Heininger, P., Pelzer, J., Claus, E., Tippmann, P.: Contami-

nation and toxicity trends for sediments – case of the Elbe

river. Water Sci. Technol. 37, 95–102 (1998).

[4] Malmon, D. V., Dunne, T., Reneau, S. L.: Predicting the fate

of sediment and pollutants in river floodplains. Environ. Sci.

Technol. 36, 2026–2032 (2002)

[5] Miehlich, G.: Schwermetallanreicherungen in Böden und

Pflanzen der Pevestorfer Elbaue (Kreis Lüchow-Dannen-

berg). Abh. Naturwiss. Ver. Hamburg 25, 75–89 (1983).

[6] Friese, K., Witter, B., Miehlich, G., Rode, M. (Eds.): Stoff-

haushalt von Auenökosystemen. Springer, Berlin, 2000.

[7] IKSE – Internationale Kommission zum Schutz der Elbe:

Entwicklung der Unterschutzstellung der Elbtalaue. http:/

/www.ikse.de/ikse/deutsch/index_themen.htm, 1999.

[8] Witter, B., Francke, W., Franke, S., Knauth, H.-D., Miehlich,

G.: Distribution and mobility of organic micropollutants in

river Elbe floodplains. Chemosphere 37, 63–78 (1998).

[9] Gocht, T., Moldenhauer, K.-M., Püttmann, W.: Historical

record of polycyclic aromatic hydrocarbons (PAH) and

heavy metals in floodplain sediments from the Rhine River

(Hessisches Ried, Germany). Appl. Geochem. 16, 1707–

1721 (2001).

[10] Friese, K., Krüger, F.: Unpublished report for the German

ministry BMBF. 1998.

[11] Friese, K., Witter, B., Brack, W., Buettner, O., Krueger, F.,

Kunert, M., Rupp, H., Miehlich, G., Groengroeft, A.,

Schwartz, R., van der Veen, A., Zachmann, D. W.: Distribu-

tion and fate of organic and inorganic contaminants in a

river floodplain – results of a case study on the river Elbe,

Germany. In: Wise, D. D., Trantolo, D. J., Cichon, E. J., In-

yang, H. I., Stottmeister, U. (Eds.).: Remediation Engineer-

ing of Contaminated Soils. Marcel Dekker, New York, 2000,

pp. 373–424.

[12] AG Boden (Ed.): Bodenkundliche Kartieranleitung.

Schweizerbart’sche Verlagsbuchhandlung, Hannover,

1994.

[13] Winkler, M., Kopf, G., Hauptvogel, C., Neu, T.: Fate of arti-

ficial musk fragrances associated with suspended particu-

lar matter (SPM) from the river Elbe (Germany) in compari-

son to other organic contaminants. Chemosphere 37,

1139–1156 (1998).

[14] Boewadt, S., Johansson, B.: Analysis of PCBs in sulfur-

containing sediments by off-line supercritical fluid extrac-

tion and HRGC-ECD. Anal. Chem. 66, 667–673 (1994).

[15] Witter, B.: Untersuchung organischer Schadstoffe in Auen

der mittleren und unteren Elbe unter Anwendung der su-

percritical fluid extraction. Dissertation, Universität Ham-

burg. GKSS Report, ISSN 0344-9629, 1995.

[Received: 16 August 2002; accepted: 22 July 2003]

depth distribution of chlorinated and polycyclic aromatic hydrocarbons in floodplain soils of the...

Documents