Hydrology and water quality aspects of rhine bank groundwater in The Netherlands

106 (1989) 341-363 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

Journal of Hydrology,

341

P. 3. STUY FZAND The Netherlands Waterworks’ Testing and Research Institute KIWA BB Nieuwegein (The Netherlands)

Ltd., P.O. Box 1072, ,%Y?

(Received May 5,1988; accepted after revision June 15,1988)

ABSTRACT Stuyfzand, P.J., 1989. Hydrology and water quality aspects of Rhine bank groundwater Netherlands. J. Hydrol., 106: 341-363.

in The

In deltaic areas with deep polders and in valleys or deltas with heavy groundwater exploitation, bank infiltration is a rapidly expanding mechanism of groundwater recharge. Rhine bank filtrate can be distinguished best from autochthonous groundwater in The Netherlands by way of its natural lower I80 content. Tritium is a good measure of the portion of water younger than 25 years, at least in well mixed Rhine bank filtrate. This portion carries the ive correlanninations originating from the Rhine, as evidenced by strong rding to the nd e.g. halogenated hydrocarbons, taste and mutagenic activity Ames test. The composition of Rhine bank filtrate is further governed by the redox level of the hydrogeochemical system, varying in The Netherlands from suboxic to anoxic with fermentation, and by the underground distance to the influent Rhine branch. Anoxic bank filtrate with strong SO,-reduction and CH,l > 1 mg 1-l exhibited a significantly anoxic bank filtrate without fermentation and without nt camp are involved llowing 09, total dissolved solids, SK),; MnO,-consumption, NH,, siderite, baryte and vivianite saturation indices, I, total hardness, total POs, Fe, dissolved organic carbon, ane, MO,VOCI, Mn, V, dichlorobenzene and 1,2=dichloroethane, in order of dec A longer underground detention time or travel d ante, leads to 8 small d Li, F, temperature, MO (only in anoxic, of bank filtrate, and a rather strong decrease in SO,-(metajstable bank filtrate), UV-extinction, AOCI, X,OCl and mutagenic activity. Coli bacteria and viruses could not be detected, not even in samples from wells at 50 m distance from the Rhine, with a minimum travel time of 30 days.

1. INTRODUCTION

ank infiltration, n asing mechanism water supply in probably collect 11 x 106m3 of bank filtrate 70 x lo6 m3, amounting to some that year. 9922.1694/89/$03.50

0 1989 Elsevier Science Publishers B.V.

By now the advantages of bank infiltration - less lowering of the groundwater table and less subsidence - hardly outweigh the disadvantages, due to the sever2 pollution of the Rhine. Complaints about the taste (De Groot and Visser, 1976; Zoeteman, 1978) compelled many water boards along the Rhine to introduce intensive purification techniques like ozonization and filtration by activated carbon (Kruithof, 1985). A faint positive point is, that the pollution supplies hydrologists ‘with useful tracers, e.g. for chemically visualizing flow patterns and dating groundwater (Stuyfzand, 1986, 1989). Since the early sixties water quality aspects of Rhine bank groundwater have been of serious concern to drinking water producers, particularly in Germany (Hopf, 1960; Koppe, 1965; Brinkhaus, 1967). There the situation differs from that in The Netherlands due to shorter underground travel times and less anaerobic conditions of the collected bank filtrate. Special attention is paid here to the aspects of “travel time” and “oxidation degree”. Both are important in the design of new pumping stations along river branches and in optimizing existing abstraction areas (Stuyfzand, 198713; Grakist et al., in prep.). This article is based on multidisciplinary research by several organizations in The Netherlands (KIWA, VEWIN and RIVM). Data referring to drinking water pumping stations along branches of the Rhine are recorded in KIWA Bulletin 89 (Van der Kooij, 1985), those referring to individual wells at various distances from the river and in various hydrogeochemical environments are in Stuyfzand (1987b). Findings from multilevel sampling devices n in Glasbergen et al. (1982), Grakist et al. (in prep.) and nitions of important concepts are given in Table 1.

2.19YDR0L06;ICAL

FRAMEWORK

In the hydrologically undisturbed situation, before about 1200AD, there will have been little bank groundwater in The Netherlands (Fig. l), because most of

TABLE 1

Important concepts and their definitions Concept

Definition

River water Bank filtrate Bank groundwater Groundwater Old watt.

Surface water in the river Pure river water underground (in practice: > 90%) Mixture of > 10% bank filtrate and “groundwater” Infiltrated rainwater with < 10% bank filtrate Water infiltrated before 1963 Water infiltrated since 1963

Young w t2r

343

the time the rivers had a draining function. Only river water overflowing the natural levees during flooding could have infiltrated and possibly have mixed with infiltrated rainwater. The higher sandy, hilly areas bordering the Rhine Valley, must have provided an ample supply of groundwater, able to penetrate very far into the fluvial plain, particularly due to the presence of several aquitards separating good aquifers. Ever since about 1200 AD the Dutch have interfered with the hydrological cycle. These activities have always favoured the development of bank groundwater. Construction of dykes along the major rivers vvascompleted around 1400 (De Cans and Schoute, 1973). Meantime a start had already been made on dewatering the peat bog wildernesses in the downstream parts of the fluvial plains. Then came the excavation of peat bogs to collect fuel, resulting in the formation of lakes. These were largely reclaimed during the period 1612-1852. The dykes raised the river level and on the other hand, behind the dykes the groundwater level became lower as a result of dewatering, reclamation, and drainage of lakes. After around 1900 groundwater exploitation in both the fluvial plain and the adjacen; sandy areas also contributed to this lowering. SO the rivers, once effluent, started to infiltrate around 1200and this process is still leading to a further spread of the bank groundwater at an ever increasing rate (Fig. 1). 50m I+ + 40 + 30 + 20 +10

I&dmlogicoll y undisturbed sifwt~on I before 1200 AD I natural

%levees

Rhine fluviol ploin

ice pushed midge

Hydrologic01 situation in 1985

ice pushed ridge

fL

dykes and recent alluvia

,;\\

MS1 - 10 -20 - 30 - 20 - 50 - 60 - 70 - 90 - 90 -100

Fig. 1. Diagram of the origin and expansion of bank groundwater. G = groundwater. MSL = mean sea level (from Stuyfzand, 1985a).

U = bank groundwater;

2.2 Preset2 t occurrertce

A cross section through the flood plain and a longitudinal profile along the Lek branch of the Lower Rhine illustrate the spatial spread of Rhine bank groundwater in The Netherlands (Fig. 2). Figure 3 shows the situation of both profiles and in addition all pumping stations along the branches of the Rhine which do or do not extract bank groundwater for drinking water supply. It can be concluded that Rhine bank groundwater is found in the first aquifer, above aquitard “C”, in a strip of a few to several kilometres wide along both sides of the downstream reaches of the Rhine branches (Engelen, 1969; Geirnaert, 1969, 1970, 1973). Here the rivers infiltrate even without groundwater extraction. Further upstream the rivers are usually still effluent, and bank groundwater is only found near places where heavy local groundwater exploitation causes such a drawdown that the river infiltrates. This is the case near Nijmegen (stations 42 and 43 in Fig. 2), for example (Stuyfzand, 1984a). 2.3 Spread of detention times The collection of bank groundwater introduces an enormous spread in detention times underground. This is shown for three well fields in operation along the Lek, by streamlines and isochrones of travel times to the extraction 4 and the related cumulative frequency distribution of detention y small spread in detention times at Schuwacht (Fig. 5) is partly connected with its location practically no flow from Q re of a well within 8 residence times, Co to well A at Tien oxbowlike flownet and to well D at N’euw-Lekkerland (Fig. 4). 3. RECOGNITION

Rhine ban roundwater can be distinguished from auto+thonous “groundwater” by uhing specific tracers (Stuyfzand, 1985a,1987a,b). se include e.g. Cl, the Br:Cl ratio, Mg, bischloro(iso)propylethers and the Fe ratio, each with its own range of application. The most reliable tracer is 180, the heaviest stable oxygen isotope in the water molecule. The essential contrast between Rhine bank filtrate ( - lY80 = 9.7-9.9 %KJ and groundwater in the Netherlands ( - PO = 7.6%) is due to the fact that about 45% of the Rhine water comes from Switzerland and about 3 from central and southern Germany. Precipitation there has a much lower content than in the Netherlands, because its concentration in th vapour phase

North

SOm

A

Old Rhine

Lek

Mouse

A’

Eind

IOkm

Am hem B

8’

SL

Fig. 2. Geohydrological sections AA’ and BB’ (Fig, 3) with the freshwater-brackish water interface (Cl = 300mg 1-l) and the spread of hine bank groundwater. Longitudinal section BE simplified after Stuyfzand (1985a). Numbering of pumping stations corresponds with Fig. 3 numbered alphabetically in geological order: Al = Westland Formation; AZ = 23 = Drente Form.; C = Kedichem Form.; D = Tegelen Form.; E = Maassluls F = Breda E’orm.

346

*

pumping

ti

idem, obondoned pumping

station station

groundwater,

0

idem,

Rhine bank fiUrute,octive

sandy hills outochtonous

octiw

obondoned

Pig. 3. Locutions of active and ablan with u distinction between “bank /iA’ = cross section through flood khine.

cloy ond peat towtonds

--geohydrologicol 9--- So--

= longitudinal

section

rotations ater” (fr profile along

is constantly lowered by raining out from oceanic air, moving inland and uphill. This process is illustrated by Fig. 6. content is normally given as the relative deviation of the I8 tio from an ocean water standard (V-SMOW = Vienna Standard an Water) in %4x

In absolute terms the l8 concentration in water samples is roughly 2000mgl-‘. he percentage of Rhine bank filtrate in a sample (%u) is calculated as: %

=

100;

-

e,>

r -

e,>

m

(2)

where Cm = aI8 or any other tracer content in the sample; Cg = ditto, in

Fig. 4. Groundwater flownet and isochrones of travel times to the extraction points for the well fields Echuwacht, Tiendweg and Nieuw-Lekkerland, pumping stations 11, 12 and 13 in Fig. 3 (adapted from Meinardi and Grakist, 1985).

102

46

10

12

14

Fig. 5. Cumulative frequency distribution of travel times for hine water (Lek and 3 well fields of Fig. 4 (adapted from Meinardi and Grakist, 1985).

:*: -: :.cl

n

a-6,5 -6,s tlJn_y,5

@g - 73 t/m-s,5 n-

eJ

A

c

8,5 t/‘/n-9,5

-9.5 t/m-xl,5

-HI,5 lmml

t/m-l il.5

A Fig. 6. Spatial variations of the lAQcontent of (A) precipitation in The Netherlands (weighted average for 1981to 1982inclusive, calculated from data in KNMI, 1982-1983). and (B) groundwater in Germany (from Fijrstel and I-I&en, 1984) From Stuyfzand (1985a).

awtochthonous groundwater; C, = ditto, in s;he influent, supplying Rhine ed to Rhine br

4, DATING MIXED WATER

n most cases the spread of detention times in the mixed water abstracted by a well or well field, is so wide that an average a ( = underground residence time) tells us nothing. More more informative knowing which fraction is younger, than, say 25 years and thus has filtrated within the 25 years protection zone around the well (field), as de w in The Neth This fraction can be determined in principle by measuring tritium ( least if we assumed mixing of two so-called “end members”: old (?I and young water (3 TU). The latter foll he tritium activity in Rhine water over t 5 years (Fig. 7), wh reasonably representative of infiltrated rainwater (see Stuyfzand, ). Old (bank) groundw must now be regarded as water over 32 years 01 will use 25 years as a 1

349 600

uncorrecte

I

J

corrected for rodiooctive decoy to 1983.0

/Y 1950

55

60

65

70

75

80

85

Fig. 7. Tritium activity over the period 1950-1985, for the Rhine near the German bo without correction for radioactive decay up to January 1, 1983 (reconstructed sources, see Stuyfzand, 1985a).

however, because this difference in time-span is not very activity has only markedly increased since 1963. For young water, the average is taken over the period from 1963up to a year of sampling,-after correction for radioactive decay. Table 2 shows some typical 3H activities of young Rhine water in various branches and of “groundwater”. Those for groundwater are based ntent of vertical profiles in various infiltrati fzand, 198413,and in prep.; Van e

calculated as follows:

= tritium activi

ted for radioactive

TABLE 2 Average tritium activity (TU) in the Rhine branches groundwater, for three periods within the end membe Period

Correction of radioactive

aal, Lek and fJs’;3eland (autochthonous)

360 sampling date; (3H)c = ditto, in groundwater, average over 1963 up to sampling date; (%U) = see eqn. (2). 4.2 Restrictions

It is obvious that the percentages of young water calculated by eqn. (3) are a rough estimate only. An importa t condition for using eqn. (3) is a very wide spread in detention times. If that is not the case, there will be a large error - e.g., if the sample contains considerable amounts of water infiltrated during periods with low (1958-1962)or high (1963-1966)activity. 4.3 Units and correction The 3H activity is usually given in TU (tritium units), equivalent to a concentration of one tritium atom per 1018hydrogen atoms or roughly 10-16mg1-‘. Th’is is equivalent to an activity of 324pCil’ @.118Bql-’ or 7.2 disintegrations per minute per litre water). For eqn. (3), all 3H analyses must be corrected for radioactive decay until a reference date in accordance with: 3H corz. =

3~,~

- [(ln2/12.35) (hi--

Ad)]

where: Rd - reference date; Ad = analysis date; both in decimal notation (e.g., 30 August 1984 = 1984.66). 6.GENERALQUALITYSURVEY

Table 3 shows the anor nit composition of averaged over the period parameters and individual c 3 and the quality development of the Rhine over the last 100years (Fig. how seriously e river is polluted, ality control measures in the since the beginning of the drainage basin of the hine, especially ta seventies, brought some improvement (e.g. in KMnQ- consumption, NH, and colour), but the overall situation is still extremely worrying. The number of isolated xenobiotic substances runs into the hundreds (Meijers, 1984),whereas reduced growth and mortality of trout in Rhine water (Poels et al., 1980) and mutageneity tests according to Ames (Van der Gaag et al., 1982) indicate ny harmful substances, in particular trace elements and heavy metals, are more or less silt-bound (Fig . 9). This bondage is of major importance for

their removal during underground passage. Finally the water temperature has been raised by about 2’6, due to the increased use of river water for industrial cooling processes.

351 TABLE 3 Inorganic composition of the Rhine, Rhine bank filtrate from individual wells (at a given cmistance in m from the Rhine branch and with mean underground residence time in years) and old, unsuspected groundwater ( = ref.); Rhine bank filtrate and “groundwater” are subdivided on the basis of their redox status (st 3section 6); based on data in Stuyfzand (1985a and b, 1987) Rhine 1850’

EC 20°C Temp. ClHCO, SOi-NO, PO, -tot FBrJPH

Na’ K’ Ca’ t

Mtt’

Fe Mn NH,’ SiO, Li B Al V Cr Ni Cu Zn Se As Rb Sr Mo Ba Pb U

@cm-’ OC mgl-’ mgl-’ mgl-’ mgl-’ mgl-’ mgl-’ mgl-’ CcgI-’

5 5 50 10 < 0.01 < 0.1 _. -

clsl ’ /rf$’ I4d ’ al-’ pg 1- ’ Id-* Pd-’ MC-’ Id-’ Id-” clfd-’ Pd-1

CH‘l H,S

pg1-’ PgI-’ mgl-’

7.77 83.9 5.8 76.2 11.7 < 0.01/j 0.05fl 0.57 4.9 18.48 1228 2.08 2.911 4.38 4.1/j 261)

lrgl 1

TU OmoPDB OhSMOW

--

773 12.8 145 161 71 17.2 1.68 0.24 0.23

10.8 12 160 35 c3 < 0.2 -

mgl-’ mgl-’ mgl-’ mgl-’ mgl-’ mgl-’ mgl-’ mgl-’ c1gi-’ clgi-’ 11gI-1

dH - s13c - s160

0,

1980-1983

-

4OO?P 1.2?/) 8611 1.561 O.S?P 4

85.3 10.8

9.8

9.8

< 100 -

-

11

8.8

Anoxic, SO,-(meta)stable

Anoxic, fermenting

25m GO.2yr

1020 m 8yr

ref. m

1lOm 0.5 yr

840

810 11.1

150

13.0 150 205 69 < 0.1 2.6 0.27 0.28 12 7.6 84 5.5 86 11.0 1.0 0.32 0.85 5.7 8.6 200 4 0.5 0.49 0.05 3.7 < 0.6 < 20 < 0.05 3.5 3.4 4’90 1.8

87 2.3 c 0.05 62.8 11.73 10.12 350 100 cl

z = partly from Molt (1961); fi = in filtered sample.

160 200 64 < 0.1 1.9 0.19

16 69

160 325

20 Cl -

15 < 0.1 5.0

0.08

0.25 11

0.06

7.3 81

7.45 8.5 0.9 23 2.6 2.60

6.4 0.74

0.19 0.02 12.0

2.7 16.0

-

1.5 7

65

2.6 520 1.1 148

6

< 0.05 c5 7.58

6.0 0.19 0.29 18

4.‘: 77 13.4 2.6 0.10 1.2

0.67

19.4 44.9 303

1.24 < 0.05 4.1 t5.9 c 20 c 0.05

510 c 0.2

530 1.3

365

264 2.0

< 0.05

< 0.05

90.5 9.53

61.8 10.84

9.80

9.36

cl

0.29

3.2 105 14.0 13.0

1.3


-

7.41 52.5

5.7

3900 150

0.19

7.2 63

5.6

Cl

332 < 0.2 cl

7 < 0.1

a 1.5

< 10

57

144 360

6.2 150 < 0.5

30
595

8.2 250 < 0.5

650

ref. r-

11.0

12.0 25.0

2.4


8yr

15.0 23.0

6.5 6 0.05

< 0.05

11.20 9.59

6.6 1.1

< 0.6

c 20

73.6

90 10.5

0.16 3.4

4.1 3.5

1.8

7.2 91 6.2

1.06

0.67 0.11

6.2

0.23 0.31 39

3.3 85 10.7

4.9 210 c 0.5

920 12.3

800m

5600 c 50 i 1

C6 ^_

40
-

<3 7.72

5600 3
352 TABLE 4 Organic group or sum parameters and individual components of the Rhine, Rhine bank filtrate and old, unsuspected groundwater ( = ref.); based on data in Puijker and Janssen (1985), Noordsij et al. (1985). Van der Kooij (1985, 1987) and KIVVA files Rhine

Anoxic, SO,,-(meta)stable

Anoxic, fermenting

198&1983

25 m G0.2yr

1lOm 0.5yr

4.6 10.4 9.9

mgl-* KMnO, -cons. mg I- ’ Em-’ UV-ext

DOC

1.2.dichloroethane dichloroethene dichlorobenzene c aromatics C bcps

pg 1-l flgl-’ pg 1-l /cg1-’ ,trgl-’ n

taste

ca.

2 ? 0.9 ?

ca. CR.

Co&bacteria 44O6‘: n I-’ AOC /1gc1-’

1.0

ref. 1 00

8yr

ref. 2 co

800m

1.7 6.5 18.7

1.9 7.5 LB

0.7 1.7 2.6

3.4 14.0 36.1

3.3 13.5 9.2

4.3 11.4 11.4

18 1.8 1.3

11. 0.4 1.4

<5 c 0.2 c 0.5

18 1.8 1.4

7 < 0.3 0.5

~5 < 0.2 < 0.5

0.1 1.8 1.3 G 0.05 0.2

0.8 3.3 < 0.05 0.05 1.1

< 0.05 < 0.05 < 0.05 0.66 c 0.02

65 6 ca. 8

figC11-’ pgCll-’ /fgCll-’

AOCI EOCl VOCl

1020m Byr

c 0.05 0.2 0.7 < 0.05 0.1 < 0.05 0.04 0.09 1.9 0.4

__

35

65,000 120

3 <2 8.1

<% 14.6

<2

:2 -

32 c2 13.4

< 0.05 < 0.05 < 0.05 < 0.02 < 0.02 1.5 <2 7.7

DO6 = dissolved organic carbon; AOCl, EOCl, VOCl = chlorinated hydrocarbons, resp. a able to activated coal, extractable in petroleum=ether and volatile; c aromatics = benzene =+toluene -I- ethylbenzene -+=dimethylbenzenes; c bcps = bis(chloroisopropy1) bis(chloropropyl)ether -I- di+opropylether + di-npropylether + methylisopropylether; easily assimilable organic carbon; ref, I = pumpin station Rhenen; ref. 2 = pumping statio;l

28 26 24 22 20 16 16 lb 12 10 8 6 L 2 1880

1

1920

1910

1960

1980

0 1880

1900

20

1940

1960

1980

Fig. 8. Quality development of the Rhine over the last 199 years. The 5 years moving average is plctted for each multiple of 5 years (from Stuyfzand, 1985b)

353 100

90 90

70

60

50 40

30 20

10

0

Fig. 9. Silt bondage of trace elements, Fe and Mn in the Rhine at Lobith in the period 1980 1983, arranged according to the silt bondage percentage (from Stuyfzand, 1985b).

5.2 Rhine bank filtrate our representative samples of young, untreated idual wells are included in Table 3 (inorgani cover a wide variation in distance fr de the two most comm ine bank filtrate in he anoxic, ferment the redox environment and t sections 6 and 7, respectively. Comparison with the river water If the four Rhine bank filtrates in (a) Abgeneral incr (lime solution and oxides, solution of

les 3 and 4 are compared with the river

354

nated hydrocarbons (AOCl, etc.: degradation and sorption) and coli bacteria (filtration and mortality). (c) Comparable concentrations of Cl, Br, Na, Mg, Ni, Pb (?), 3H, “‘0 and bis(chloro[iso]propyl)ethers (in the Rhine 0.1-2 pg I-‘, see further in Noordsij et al., 1985b). Noordsij et al. (1985a) found some 600 organic substances, in concentrations from 0.05 to a few pg I- ‘, of which 180could be identified. They originate mainly from the Rhine. Furthermore it follows from Van der Gaag et al. (1985) that, compared with river water, bank filtrate generally scores a lower but still significant mutageneity according to the Ames test. Viruses have not yet been detected in bank filtrate, even in samples from wells at short distances from the river, although the Rhine carries a large amount (Ir. M. van Olphen, KIWA, oral commun.). Comparison with clean “groundwater” Tables 3 and 4 also include the analyses of two samples of unsuspected, clean one in the redox category anoxic, SO, (meta)stable and one “groundwater”, anoxic, fermenting. Compared with these, the four young Rhine bank filtrates are characterized by their high concentrations of Cl, SO4, Na, Ca, Mn, NH4, Ba, ethers), Pb, 3H, by xenobiotic substances (such as A Cl, his-chloroisopropyl and by taste. Possibly also AOC, conductivity, and KMnO,:DQC ratio the presence of more unstabilized organic matter) are higher, content is lower in these bank filtrates. Relationships with tritium In the water obtained from wells extractin positive correlation have been demo (independent variab ) and various co groups of chlorinated o

cording to the Ames et al., 1985). Similar relationships were also demonstrated of Rhine bank filtrate in the abstracted water, which indicates that recently hine water (that is to say, younger than 25 years) is the main source of these contaminants. 6. EFFECTS

OF THE REDOX LEVEL

The redox level of eater largely indicates which organic and inorganic substances are mobile or can be mobilized in water (see e.g. Stumm and organ, 19 irect rr 2asurement of the redox potential is d and has virtually no ml.?aning indberg and Runnells, 198 It is therefore better to derive the redox lev from the presence or abs redox-sensitive co onents of water: 2, N03, SO,, Fe, Mn

355 -10~.

tvpicfl1

sub&l

0

-200

NO~,SO~.cH,

5

10

15

.;dLI++

20

--IMn,NH,,Fe;mg/lI-+

25

0

0.5

1.0

1.5

2.0 YttF--

z%

+200 +400 I600 +800 mV --Eh,--+

Fig. 10. Classification of the redox environment, based on the presence or absence of the main redox components of water (05, NO,, SO,, Fe, Mn and CH,). A progressive subsoil passage is assumed as plug flow in a bystem closed from the atmosphere at constant initial 0;) NO:, and SO,I concentrations of 10,20 and 25mg l-l, respectively. The indicative redox potentials at pH = ‘7 (Ek,?; crre derived from Stumm and Morgan (1981); from Stuyfzand (1989).

etherlands, mainly sub-oxic and the four types of anoxic ur. In general, the degree of reduction increases in the downstream direction along the Rhine branches. This is due to increasing .amounts of organic matter in the upper aquitards (Stuyfzand, 1987). The effects of redox level differences are not limited to the concentration levels of redox-sensitive main components as pictured in Fig. 10. This is demonstrated in Table 5 for the two dominating groups of anoxic Rhine bank filtrate, i.e. the SO,-(meta)stable cate y (still containing nearly all original sulfate), ich has lost most of the sulphate and contains and the fermenting category, ” -t- -t=” for the pa~am~ters examined in

saturation

in

shows the above filtrate due to: (1) mobilisation of biophile su of organic matter, leading to increases atter (DOC, 0, consu (2) further ution of

in

I *

/

UV-ext. CH, i& I Li

DQC

NH, SiO, _.KMnO,, -cons.

we+ Fe Mn

PO,-tot FBrJPH Na’ K’ Ca2 ’

istance Travel time

Pcgl--’ ccgl-’ ccgl-’ C(gl-’ ClgI” ccgl-* I&-’

R/M mgl-’

crgl-’ mgi-’ mgl-’ mgl-’ mgl-* mgl-’ mgl-* mg 1” mgl” mgl-r mg 1-r mgl-’

m yr mgl-* mgl-’ mgl-l mgl-’ mgl-’ mgl-’

551 4.0 148 192 ?0,7 1.12 0.1 0.26 7.4 7.61 79.9 5.04 83.2 11.1 2.17 0.60 1.53 9.2 6.5 1.6 13.5 0.24 46 7.4 242 0.25 0.97 0.04 4.2

Xl

Significance of differences between anoxic, SO,-(meta)st of difference; + = 95--W!! probability of difference; - variable; the degrees of freedom are 12 (n, = 9, n, = 5) (1987)

TABLE 5

6.4

95.4 12.7 6.92 1.15 1 21.6 14.9 4.6

3.8 148 339 13.4

432

x2 440 4.2 14.4 10.6 6.6 0.89 0.07 0.03 4.3 0.24 3.2 1.33 3.2 0.6 1.65 0.22 0.89 2.94 0.9 0.2 6.2 0.25 23 2.6 102 co.1 0.33 0.03 1.3

01 265 2.8 10.2 27.9 11.6 2.59 0.04 0.02 14.4 0.11 14.2 1.76 9.0 1.3 3.87 0.71 3.72 2.30 3.6 3.2 10.3 0.65 57 2.7 41 4.1 i.58 0.33 1.9

*2 0.54 0.10 0.07 - 14.43 11.91 - 3.97 - 0.38 - 2.13 - 4.88 2.66 - 0.02 0.32 - 3.76 - 3.21 - 3.27 - 2.25 - 7.04 - 8.07 - 7.12 - 3.06 - 1.13 - 18.66 - 0.38 0.69 0.92 - 1.56 - 2.03 - 1.64 - 0.85

T

+

+ ++ ++

Signif.

, fermenting Rhine Fank filtrate (x2, a*); + + = b 99% probability of difference. x = niean; CJ= standard deviation; 2’ = Students T on operating wells for drinking water supply; adapted from Stuyfzand

% OI

cu

flgl-’ flgl-’ pgl-l ccgl-’

pgCll-’ /IgCll-1 pgCll-1

TU !%IPDB ‘kkSMOW OC @cm-’ mgl-’ mmol1-’ mm011-l pm01l-’ /Inlo11-l pm011-l PmoII-’ pm011-l pm011-l

Cc&* MC” Pgl-p ld-L C(w Pkv PJz1--’

2.53 3.35 85 64 -40 113 - 19 -57 6.55 0.03 - 0.22 @.23 - 0.66 0.85 12.9 1.1 2.2 0.5 4.2 1.2 1.0

604

0.7 3.2 2.37 536 1.2 127 2.2 69.8 11.65 9.76 11.8 812

13.6 1.4

0.10 0.21 59 169 29 65 28 75 0.15 0.10 0.17 0.16 0.13 1.37 3.8 0.5 1.2 0.5 2.8 1.3 0.6

1.1 2.4 2.4 3.4 1.80 71 0.5 132 0.6 11.2 1.34 0.21 0.6 16 18 0.25 0.64 206 469 39 260 59 124 0.24 0.07 0.26 0.22 0.05 1.05 5.6 1.8 0.5 / 0.05 0.6 0.1 0.6 1.47 0.73 0.62 0.12 2.43 - 2.95 - 0.29 - 1.94 0.64 1.01 0.97 - 3.78 - 9.27 - 3.99 - 13.00 - 7.04 - 0.10 0.34 - 3.45 - 2.94 11.27 5.88 - 0.96 - 1.50 - 4.30 - 6.31 - 3.29 - 0.28 - 0.59 2.33 2.03 2.84 1.80 0.38

-

++

+

++ ++ ++ -

++ ++ ++ ++ -

++ ++ ++ ++ ++ -

+

++

-

-

TDS = Total DissolvedSolids; tot hh = total hardness; = HCO, + CO, + CO,; TIN = NO, + NO, + NH,; x* = x correctedfor Rhine salt contribution; §I-mineral = saturation index for flog IAP/Ks& C bcps = See Table 4.

1 bcps

dichloroethene 1,Zdichloroethane

temp. EC{20°) TDS tot hh TIC TIN Na* M* Ca* Mg* SO,* SI-barite S&calcite &rhodochrosite SI-siderite SZ-silica-glas S-vivianite AOCl EOCl VOCl

As Rb Sr MO Ba Pb 3H - 613C - a’“0

GzJ 3

358 organic

acids,

in connection

with continuing

oxidation

(Ca-increase,

pH-

decrease); (3) dissolution of minerals typical for this environment, i.e. siderite (FeCQ,), (MnCO,) and biogenic SiO, vivianite (Fe, [PO,], 8H,O), rhodochrosite (SiO, nH,O); (4) a decreased SO, concentration leading to solution of sulfate minerals - here only baryte (BaSO,) - on the one hand, and precipitation of sulphide minerals involving, among others, molybdenum, on the other; (5) an increased concentration of dissolved substances primarily due to points l-3, exhibited by increased conductivity and TDS; and finally: (6) bacteriologically catalyzed degradation, occurring specifically in this environment, of volatile, chlorinated hydrocarbons. This is in accordance with the literature (Verheijen, 1985;Smeenk, 1985; Hrubec et al., 1984). No unequivocal explanation could be found for the higher 3H, Br and Mg concentrations in anoxic, fermenting bank filtrate. l

l

7. EFFECTS

OF UNDERGROUND

DETENTION

TIME

longer underground detention time or travel distance apparently leads to: (a) a decreased share of bank filtrate and thus an increase in addition of infiltrated rain water. This is indicated by less negative values for aI80 (Fig. 11); (b) a decreased tritium activity, at least at average residence times of over 4 years (Fig. 12); (c) a decrease in K* ( = K corrected for river salt contributions), Li and F is process occurs in the first aquitard (A, e underlying aquifer; to heat sorption and exchan A

table bank file , 13). ‘She decre - -, 4

-

9

P y-

0

9.1

-I__--

--

.

.

d he

I-._

? ? ?

3

9.6

b

ih0

-a - 9.8 -

0 ? *

X

-10.0 0

= Rhine = matic. SO4- m&c&able = tmxic . ‘iwmenting

Fig. 11. Relationship between I’ 0 content and the modal underground branch to wells estracting bank filtrate (from Stuyfzand, 1987b).

travel. time from Rhine

359 --I

n t Rhine 0 = onoxic, SO&- metostoble 0 = ortoxic, fermenting

2

0 ~

4

6

6

10

12

f modal trove1 time ;yeors I-

Fig. 12. Relationship between noncorrected time from Rhine branch to wells extracting

tritium activity and the modal untierground bank filtrate (from Stuyfzand. 1987b).

travel

I

0

2.0 t

MO

c

40

~_

1

9 30

4 L & temperature

UV- eutiriction

20

i 1 10 2

4.1. 0

2 -

I.,‘,.,‘,.

4

I modal tram1

6

6

IO

trm@ ; yrorsk -

12

’

Fig. 13.Relationship between modal travel time from and/or physical properties of Rhine bank filtrate. x able Rhine bank filtrate; 0 = anoxic, fermenting

0

0

2

4

0

e

10

12

IA

and various components

360

explained in an anoxic, SO,-(meta)stable environment by MO adsorption from Rhine water or a gradually increasing MO content in the river water. In an anoxic fermenting environment, MO is already immobilized over the first few metres, probably by occlusion in iron sulphides, a process which was also found in anoxic Black Sea sediments (Volkov and Fomina, 1974). The water which is highly depleted of Mo and SO, then perhaps gradually gains MO from the porous medium during continuing underground passage; (f) a decrease in ultraviolet extinction (Fig. 13), i.e. mainly from dissolved humic compounds, at least after the first (tens of) metres underground passage. Microbiological degradation and adsorption are probably responsible for this phenomenon; (g) a decreased concentration of chlorinated hydrocarbons over the first metres of underground passage, illustrated by AOCl ( = halogenated hydrocarbons adsorbable to activated carbon, expressed as Cl) and X,OCl ( = halogenated hydrocarbons adsorbable to XAD-resin at pIl = 7) in Fig. 14, and lastly: (h) a rather sharp decrease over the first metres of underground passage of mutagenic activity according to the Ames test (Fig. 14). Except for MO, the findings seem to be independent of the redox state within the category “anoxic Rhine bank filtrate”. Furthermore, it is important that in the traverse of Fig. 14, no cholinesterase inhibitors (c 0.01 pglL), no PCBs ( < 0.01 r(lg1-l) and no bacteria of the Coli group ( < l/lOOcc-I) were detected, even close to the river (Puyker and Janssen, 1985; Grakist et al., in prep.). On

00 0

100

200 300 200 603 600 distancetmvofled;m _* I underground

J

700

Fig. 14. Relationship betweenACE1 ( = halogenated hydrocarbons adsordable to activated carbon expressed as Cl), &WI (ditto XAD-resin at pH = 7) as well as mutagenic activity according to the Ames test in anoxic, SO, -(mta)stable Rhine bank filtrate, and the underground distance travelled to a series of observation wells (based on data in Puj;ker and Janssen, 1985 and Van der Gaag et al., 19851.

361

the contrary organic microcontaminants with log&,, < 3.5(&, = octanol/ water distribution coefficient) were detectable at all measuring locations (Noordsij et al., 1985b). 8. CONCLUSIONS

The great underground expansion of Rhine bank filtrate in The Netherlands due to changed hydrological conditions is worrying in the context of the grave pollution of the Rhine. Using intensive and costly purification methods, drinking water of good quality can be prepared from the abstracted Rhine bank groundwater (Kruithof, 1985; Van der Kooij, 1985a), even though not all substances can be removed. Rhine bank filtrate without too much water discharged from low-lying polders, can be recognized most unambiguously with the aid of the natural tracer 180. By using tritium, it is possible to calculate the portion of water younger than 25 years in well-mixed Rhine bank groundwater. Due to strong positive correlations with various pollutants, this tracer (or the related % young water) indicates the presence of contaminations originating from the Rhine, such as various halogenated hydrocarbons and flavours, as well as mutageneity according to the Ames test. The degree of oxygenation of the hydrogeochemical system of bank filtration plays an important part in the composition of hine bank filtrate. To optimize existing well fields for drinking water supply or in planning new pumping stations along Rhine branches, it is better to avoid sites with a very low redox d their associated high concentrations of 2, Ba, methane and humic acids. concentrations compounds, seems

ACKNOWLEDGEMENT

oc~atio The project was conducted in close cooperat~o REFERENCES n de Appelo, C.A.J., Krajenbrink, G.J.W., Van erij, grondwaterkwaliteit in het infiltratieg VROM-Leidschendam, Ser. Bodembeacherming, 11, 144 pp. Brinkhaus, T., 1967. Erfahrungen mit uferfiltriertem Grundwasser am Mittelrhein. Abwasser, 108: 135-138. regio’s van ~ed~rlaud. Inst. De Gans, W. and Schoute, J.F.Th., 1973. ysisch-geografiscbe Aardwet., Vrije Univ., Amsterdam, 90 pp. De Groot, R. and Visser, A.J., 1976. Smaakbezwaren van het leidingwated in Zwolle en omtstreken. I-&O: (9): 52-56.

362 Engelen, G.B., 1969. Hydrochemistry as a tool for the determination of the origin of upward seepage in the polder area Alblasserwaard (Netherlands). Geol. Mijnbouw, 48(2): 226-239. Forstel, H. and Hutzen, II., 1984. Variation des Verhaltnisses der stabilen Sauerstoff-Isotope im Grundwasser der Bundesrepublik Deutschland. GWF, Wasser Abwasser, 125 (HI): 21-25. Geirnaert, W., 1969. Preliminary report on hydrochemical investigations in the western Netherlands. Geol. Mijnbouw, 48-2; 249-254. Geirnaert, W., 1970. Hydrogeologie. Toelichting Geol. Kaart Nederland, 1:60999, blad Gorinchem Oost (38--O),Rijks Geol. Dienst, Haarlem, pp. 91-101. Geirnaert, W. 1973. The hydrogeology and hydrogeochemistry of the lower Rhine fluvial plain. Ph.D. Thesis, L*eiden, Leidse Geol. Meded., 49: 59-84. Glasbergen, P., Grakist, G. and Maas, C., 1982. Winning van oevergrondwater: algemene hy drologische en hydrochemische aspecten. IODZH-Deelrapp., (14), Rijksinst. Drinkwatervoorziening, Leidschendam, 75 pp. Grakist, G., Uffink, G. and Boumans, L.J.M. (in prep.). Verkenning van mogelijkheden tot winning van oevergrondwater nabij Opperduit. RIVM-Rapp. Groennou, J.T., ‘1985.De smaakbepaling. In: D. Van der Kooij (Editor), Drinkwater uit Oevergrondwater. KIWA-Meded., 89: 7.1-7.22. Hopf, W., 1960. Versuche mit Aktivkohle zur Aufbereitung des Dusseldorfer Trinkwassers. GWF, Wasser Abwasser, 101: 330-336. Hrubec, J., Den Boer, A.C., Luijten, W.C.M.M., Van Oers, ,J. A.M. and Piet, G.J. 2984. Modelonderzoek betreffende het gedrag van verontreinigingen tijdens percolatie van voorgezuiverd oppervlaktewater door de zandbodem. RIVM-Rapp., Lab. Ecol. Water Drinkwater, No. 83-395-\/A/ HRU/mk, 50 pp. KNMI/RIV, 1982-1983. Chemical composition of precipitation over the Netherlands. Annu. Rep. KNMI 156=4and 156.5. Koppe, P., 1965. Identifizierung der Hauptgeruchsstoffe im Uferfiltrat des Mittel- und Niedtrrheins. Vom Wasser, 32: 33-68. Kruithof, J.C., 1985. Zuiv ngsprocessen voor de bcreiding van drinkwater u In: D. Van der Kooij ( itor), Drinkwater uit Oevergrondwater. KIWA-M Lindberg, R.D. and Runnells, D.D., 1984. Ground water redox reactions: an an state applied to Eh m ochemical modelin . Science, 225: 925-927. Meijers, A,P. 1984. De sa Rijnwuter in 1982 n 1983. S~nlenwerk~nd~ Rijn- en Maaswaterleidingbedr., Meinardi, CR., 1 83. De cahalten aan natuurlijke isotopen gemeten in het project “KwaliteitsRijks Inst, Drinkwatervoorziening, Leidschendam, hy.h., 8;~--24, Meinardi, C.R. and Grakist, G., 1985. Hydrology of bank groundwater withdrawals in the Netherlands. J. Hydrol., 78: 161-163, Molt, E.G., 1961. Verontreiniging van het Rijnwater. 33e Vakantiecursus Drinkwatervooniening, Rijks Inst. Drinkwatervoorziening, Leidschendam, pp. 46-71. Noordsij, A., Branch, A. and Speknijder, P., 1985a. Organische verbindingen in oevergrondwrter en in het dt?aruit bereide drinkwater. In: D. van der Kooii (Editor), Drinkwater uit Oevergrondwater. KIWA-Meded., 89: 5.1-5.64. Noordsij, A., Puijker, L.M. and Van der Gaag, M.A., 1985b. The quality of drinking water prepared from bank-filtered river water in the Netherlands. Sci. Total Environ., 47: 273-292. Peels, C.L.M., Van de Gaag, MA. and Van dt;r Kerkhoff, J.F.J., 1980. An investigation into the longterm effects of Rhine water on rainbow trout. Watar Res., 14: 192+1935. Puijker, L.M. and Janssen, H.M.J., 1985. ‘2roepsparamerers. In: 1). V.xn der ooij (Editor), grondwater. KIWA Meded., 89: 4.1-4.37. Grganische micr -erontreinigingen. In: P. J. Stuyfzan Duininfiltratie. I, YA Me&d., 81: 196-216. organ, J.J., 9,981: Aqua :i chemistry, an introduction emphasizing chemical equilibria in natural waters. Wiley, New York, N.Y., 2nd ed.., 786 pp.

363 Stuyfiand, P.J., 19’64a. Isotopenhydrologisch en hydrochemisch onderzoek rond het pompstation Nieuwe Marktstraat te Nijmegen. KIWA Rapp., SWO-84.209, 36 pp. Stuyfzand, P.J., 1984b. Groundwater quality evolution in the upper aquifer of the coastal dune area he western Netherlands. In: E. Eriksson (Editor), Hydrochemical Balances of Freshwater Systems. Proc. Uppsala Symp., IAHS Pub]., 150: 87-98. Stuyfiand, P.J., 1985a. Hydrologie, herkenning en datering van Rijnoevergrondwater. In: D. van der Kooij (Editor), Drinkwater uit Oevergrondwater. KIWA Meded., 89: 2.1-2.67. Stuyfzand, P.J., 19858. Anorganische bestanddelen van Rijnoevergrondwater. In: D. van der Ksoij (Editor), Drinkwater uit Oevergrondwater. KIWA Meded., 89: 3.1-3.57. Stuyfzand, P.J., 1986. Macroparameters bij duininfiltratie. Kwaliteitsveranderingen van oppervlaktewater bij kunstmatige infiltratie in de Nederlandse kustduinen: Macroparameters. Basisrapp. bij 5 deelrapp. (KIWA-SWE 366-370) KIWA Meded., 82, 336 pp. Stuyfzand, P.J., 1987. Anorganische chemie van Rijnoevergrondwater uit pompputten op diverse afstanden van de oever, in verschillende hydrogeochemische milieus. KIWA Rapp. SWE 87.665, 61 PP* Stuyfzand, P.J., 1989. Hydrochemische onderzoeksmethoden ter analyse van grondwaterstroming. H,O. (in press). Stuyfzand, P.J. (in prep.). Hydrochemistry and hydrology of the coastal dune area of the western Netherlands. Ph. D., Inst. Earth Sci., Vrije Univ., Amsterdam. Van der Gaag, M.A., Noordsij, il. and Oranje, J.P., 1982. Presence of mutagens in Dutch surface water and effects of water treatment processes for drinking water preparation. In: M. Sorsa and H. Vano (Editors), Mutagens in our Environment. Liss, New York, N.Y., pp. 277-286. Van der Gaag, M.A., Oranje, J.P. and Bolman, M.E.F. 1985. Mutageniteit. In: D. Van der Kooij (Editor), Drinkwater uit Oevergrondwater. KIWA Meded., 89: 8.1-8.24. Van der Kooij, D. (Editor), 1985. Drinkwater uit oevergrondwater: Hydrologie, kwaliteit en zuivering. KIWA Meded., 89. 1985. Microbiologische aspecten. In: D. Van der Kooij (Editor), Drinkwater uit Van der Koolj, er. KIWA Meded., 89: 6.1-6.24. Oevergrond Van der Kooij, D., 1986. Bacterien en AOC-gehalte in oevergrondwater in relatie tot de afstand n rivier en de watersamenstelling. KIWA Rapp. SWE 86-019. n, W,, 197% Diffuse en lokale verontreinigingsbronnen en hun effecten op het demverontreInigingen: transport van organische verbindinVerheijen, L.A.H.M., 1985. Cedrag door de bodem. MlWA Medcd. 86, 114 pp, mina, L.S., 1974. Influence of organic material and processes of sulfide formation of some trace elements in deepwater sediments of Black Sea. Am. Assoc. P&r. Geol. Mem., 20: 456-476. Wessels, H.R.A., 1984. De temperatuur van de 20, 17 (18): 396-399. Zoeteman, B.C.-J., 11978. Sensory assessment and chemical composition of drinking water. Diss., Van der Gar g, ‘s-Gravenhage.