transport of creosote compounds in a large, intact, macroporous clayey till column

Ž .Journal of Contaminant Hydrology 39 1999 309–329www.elsevier.comrlocaterjconhyd

Transport of creosote compounds in a large, intact,macroporous clayey till column

Kim Broholm a,), Peter R. Jørgensen b,c, Asger B. Hansen d,Erik Arvin a, Martin Hansen e

a Department of EnÕironmental Science and Engineering, Technical UniÕersity of Denmark, Building 115,DK-2800 Lyngby, Denmark

b Danish Geotechnical Institute, MaglebjergÕej 1, DK-2800 Lyngby, Denmarkc Geological Institute, UniÕersity of Copenhagen, ØsterÕoldgade 10, DK-1350 Copenhagen, Denmarkd National EnÕironmental Research Institute, FrederiksborgÕej 399, Postbox 358, DK-4000 Roskilde,

Denmarke Geological SurÕey of Denmark and Greenland, ThoraÕej 8, DK-2400 Copenhagen NV, Denmark

Received 30 October 1997; received in revised form 28 January 1999; accepted 12 April 1999

Abstract

The transport in macroporous clayey till of bromide and 25 organic compounds typical ofcreosote was studied using a large intact soil column. The organic compounds represented the

Ž .following groups: polycyclic aromatic hydrocarbons PAHs , phenolic compounds, monoaromaticŽ .hydrocarbons BTEXs , and heterocyclic compounds containing oxygen, nitrogen or sulphur in the

Ž . Žaromatic ring structure NSO-compounds . The clayey till column 0.5 m in height and 0.5 m in.diameter was obtained from a depth of 1–1.5 m at an experimental site located on the island of

Funen, Denmark. Sodium azide was added to the influent water of the column to preventbiodegradation of the studied organic compounds. For the first 24 days of the experiment, the flowrate was 219 ml dayy1 corresponding to an infiltration rate of 0.0011 m dayy1. At this flow rate,the effluent concentrations of bromide and the organic compounds increased very slowly. Thetransport of bromide and the organic compounds were successfully increased by increasing theflow rate to 1353 ml dayy1 corresponding to 0.0069 m dayy1. The experiment showed that thetransport of low-molecular-weight organic compounds was not retarded relative to bromide. Thehigh-molecular-weight organic compounds were retarded significantly. The influence of sorptionon the transport of the organic compounds through the column was evaluated based on theobserved breakthrough curves. The observed order in the column experiment was, with increasingretardation, the following: benzenespyrroles tolueneso-xylenesp-xylenesethylbenzenes

) Corresponding author. VKI, Agern Alle 11, DK-2920 Hørsholm, Denmark. Tel.: q45-45169200; Fax:q45-45169292; E-mail: [email protected]

0169-7722r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved.Ž .PII: S0169-7722 99 00040-6

( )K. Broholm et al.rJournal of Contaminant Hydrology 39 1999 309–329310

phenolsbenzothiophenesbenzofuran-naphthalene-1 -methylpyrrole-1 - methylnaphthalenes indoleso-cresolsquinoline-3,5 -dimethylphenols2,4 -dimethylphenol-acridine- carba-zole - 2-methylquinoline - fluorene - dibenzofuran - phenanthrene s dibenzothiophene. Thisorder could not be predicted from regularly characteristics as octanolrwater-distribution coeffi-cients of the organic compounds but only from experimentally determined data. The resultsindicate that a thin clayey till cover of the type described in this paper does not protectgroundwater against contamination by low-molecular-weight organic compounds. q 1999 ElsevierScience B.V. All rights reserved.

Keywords: Migration; Transport; Creosote; Coal tar; Biopores; Clayey till; Column experiment

1. Introduction

Ž .Creosote or coal tar contaminated soil and groundwater is a widespread problem inŽindustrialized countries Korsgaard et al., 1989; Raven and Beck, 1992; Lotimer et al.,

.1992 . Creosote has been used intensively for wood preservation and at asphalt factories.ŽIn addition, it is a waste product from the production of gas from coal Korsgaard et al.,

.1989 . Creosote consists of hundreds of different organic compounds of which only asmall number have been identified. The composition of the organic compounds increosote varies considerably depending upon the actual production technique. Usually,

Ž .polycyclic aromatic hydrocarbons PAHs constitute between 70 and 85% of the organiccompounds in creosote, phenolic compounds about 10%, monoaromatic hydrocarbonsŽ .BTEXs less than 3%, and heterocyclic compounds containing oxygen, nitrogen or

Ž . Žsulphur in the ring structure NSO-compounds between 3 and 15% Mueller et al.,.1989; Danish EPA, 1990; Environment Canada, 1993 .

With groundwater contamination originating from creosote contaminated sites, thephenolic- and NSO-compounds represent a larger problem than the PAHs, although theyconstitute a small fraction of the creosote. This is due to their high aqueous solubilities

Ž .relative to those of most of the PAHs Table 1 . This has been observed at threegasworks sites in Denmark where the NSO-compounds were found to constitute50–70% of the sum of GC-detectable organic compounds in groundwater sampled

Ž .approximately 50 m down gradient from the source Johansen et al., 1997 .

Notes to Table 1:a Ž .Mackay et al. 1992a .b Ž .Shiu et al. 1994 .c Ž .Mackay et al. 1992b .d Ž .Pearlman et al. 1984 .e Ž .Hansch and Leo 1979 .f Ž .Katritzky 1963 .g Ž .Hassett et al. 1980 .h Ž .Broholm et al. 1999b . The distribution coefficients were measured for mixtures with all the compoundspresent simultaneously.i pK -values for the protonated species.a

The time for breakthrough and the recovery has been explained in the text.K is the octanol–water distribution coefficient, pK is the acid dissociation constant and K is the linearow a d

sorption distribution coefficient.

()

K.B

roholmet

al.rJournalof

Contam

inantHydrology

391999

309–

329311

Table 1Relevant physicalrchemical properties of the organic compounds used in this study, their average influent concentrations, the time for 50% breakthrough, and theirmass recovery

h y1Ž . Ž .Compound Aqueous pK log K K l kg Influent conc. Time for 50% Recoverya ow dy1Ž .solubility mg l breakthrough

y1Ž . Ž .mg l days

Bromide – – – – – 36.5 0.77a Ž .Benzene 1780 – 2.13 0.23 2.75 "0.32 36.5 0.97a Ž .Toluene 515 – 2.69 0.32 4.13 "0.45 36 0.90

a Ž .Ethylbenzene 152 – 3.13 0.46 4.72 "0.45 36.5 0.87a Ž .p-Xylene 215 – 3.18 0.4 4.75 "0.50 36.5 0.87a Ž .o-Xylene 220 – 3.15 0.38 5.11 "0.51 36.5 0.88

b Ž . Ž .Phenol 88,360 9.89 1.46 0.08 3.23 "0.21 36.5 0.63b Ž .o-Cresol 26,000 10.26 1.98 0.12 4.42 "0.53 43–53 0.55

b Ž .2,4-Dimethylphenol 8795 10.6 2.35 0.43 3.63 "0.47 55–78 0.33b Ž .3,5-Dimethylphenol 5500 10.2 2.35 0.2 3.39 "0.42 55–78 0.42

c Ž .Naphthalene 31 – 3.37 0.63 2.47 "0.26 38–48 0.71c Ž .1-Methylnaphthalene 28 – 3.87 1.61 1.95 "0.39 48–51 0.66

c Ž .Fluorene 1.9 – 4.18 4.38 0.36 "0.14 0.2 0.20c Ž .Phenanthrene 1.1 – 4.57 14.0 0.28 "0.11 0.06 0.04

f e Ž . Ž .Pyrrole 58,800 – 0.75 1.81 3.41 "0.41 36 0.63Ž . Ž .1-Methylpyrrole – – – 3.12 2.57 "0.36 42–46 0.88

d e Ž .Indole 1875 – 2.00 1.14 2.31 "0.28 39–62 0.57d f,i e Ž .Quinoline 6330 4.94 2.03 0.45 3.77 "0.59 48–65 0.80

f,i e Ž .2-Methylquinoline – 5.41 2.59 1.58 1.93 "0.56 0.45 0.28d e Ž .Carbazole 1.2 – 3.72 2.92 0.24 "0.11 71–76 0.32d f,i e Ž .Acridine 46.6 5.6 3.40 1.52 0.33 "0.13 63–72 0.57

d e Ž .Benzothiophene 130 – 3.12 0.59 3.51 "0.33 37 0.73d g Ž .Dibenzothiophene 1 – 4.38 12.31 0.19 "0.09 0.05 0.04

f eFuran 28,600 – 1.34e Ž .Benzofuran – – 2.67 1.4 2.53 "0.41 37 0.66

c Ž .Dibenzofuran 4.75 – 4.31 4.53 1.32 "0.27 0.18 0.15


Clay-rich tills have often been considered to be efficient protection layers forunderlying aquifers, due to their low hydraulic conductivity. However, within the lastdecade the presence of fractures in clayey tills has been documented at differentlocations. Excavations at sites in Denmark have revealed visible fractures in tills to

Ž .depths of 4–6 m Jørgensen and Fredericia, 1992; Klint and Fredericia, 1995 . A tritiumprofile measured at Havdrup, Denmark, indicated that transport into the till was not onlycontrolled by diffusive and convective transport, but also by the presence of fractures to

Ž .a depth of 6–10 m Jørgensen and Fredericia, 1992 . A pump test demonstrated theŽpresence of hydraulically active fractures to a depth of 18 m in Canada Keller et al.,

.1986 . Furthermore, the results of other pump tests have indicated that extensive clayeyŽtill layers have been penetrated by hydraulically conductive fractures D’Astous et al.,

.1989; Thomson, 1990; Rudolph et al., 1991; Ruland et al., 1991 . Fractures originatefrom desiccation, freezerthaw events, and glacial tectonics. Other macropores, such asworm holes and decayed root channels, are usually abundant in the upper portion of tills.Those pores are named biopores in the rest of this paper.

The presence of fractures in clayey till may impose a major control on the till’shydraulic properties. The bulk hydraulic conductivity, which may increase several orders

Ž .of magnitude due to the presence of fractures Fredericia, 1990 , will depend on thefracture aperture and spacing and on the fracture-interconnection.

Previous experiments have revealed that the transport of bacteriophages, varioustracers, some pesticides, and some creosote compounds is enhanced significantly due to

Žthe presence of fractures in clayey tills Jørgensen and Fredericia, 1992; McKay et al.,1993a,b,c; Jørgensen and Foged, 1994; Broholm et al., 1995; Hinsby et al., 1996;

.Jørgensen et al., 1998b . Water velocities in fractures ranging between 10 and 50 mdayy1 have been estimated for some column experiments at hydraulic gradients of

Ž .0.1–1 Jørgensen and Foged, 1994; Hinsby et al., 1996, Jørgensen et al., 1998b . Thisresulted in a breakthrough of bacteriophages in a clayey till column with a length of 0.5

Ž .m in approximately 10 min Hinsby et al., 1996 .Ž .For this study, 25 organic compounds listed in Table 1 representing the differentŽgroups of chemicals typical of creosote five BTEXs, four phenolic compounds, four

.PAHs, and 12 NSO-compounds were chosen. A large number of NSO-compounds wereincluded due to sparse information regarding their behaviour relative to the other groupsof chemicals. Among the NSO-compounds, quinoline, 2-methylquinoline, and acridine

Ž .are bases with pK -values between 4.9 and 5.6 for their protonated species Table 1 .aŽThe phenolic compounds are weak acids with pK -values between 9.9 and 10.6 Tablea

.1 . At neutral pH, the bases and the acids used in this study are in their neutral forms.However, the pH in the bulk liquid may be 3–4 pH-units higher than the pH very close

Ž . Žto clay minerals Bailey et al., 1968 . Consequently, a portion of the bases quinoline,.2-methylquinoline, and acridine may be present as their protonated species near the

minerals, depending on the actual pH, which may affect the transport of the bases.Sorption to the minerals and diffusion into the matrix affect the transport of

chemicals in bioporousrfractured clayey till. The sorption of a mixture of 25 organiccompounds onto clayey till similar to that used in this study has been investigatedŽ .Broholm et al., 1999a,b . The results revealed that at low concentrations, the sorption ofthe organic compounds could be adequately fitted with linear sorption isotherms. The

( )K. Broholm et al.rJournal of Contaminant Hydrology 39 1999 309–329 313

sorption distribution coefficients for linear isotherms are listed in Table 1. However, athigh concentrations the sorption of the most strongly sorped organic compoundsincreased significantly. This behaviour was attributed to multiple layer sorption orcondensation in the sorbed phase which may have been induced by the presence of the

Ž .basic compounds in the mixture quinoline, 2-methylquinoline and acridine .The purposes of this biologically inactive column experiment at saturated flow

Ž .conditions were: 1 to study the transport of 25 organic compounds through macrop-Ž . Ž .orous clayey till and compare the results with the transport of a tracer bromide ; 2 to

compare the observed behaviour of the organic compounds with the results of sorptionŽ .and diffusion experiments conducted on similar clayey till; and 3 to study the

protective characteristics of the clayey till.A second column obtained from the same field site was biologically active and used

to study the combination of transport and biodegradation of the same organic com-pounds. The results from the biologically active column experiment are presented in

Ž .Broholm et al. 1999d .

2. Materials and methods

2.1. Experimental set-up

ŽA cylindrical sample of undisturbed clayey till 0.5 m in height and 0.5 m in.diameter was collected from a depth of 1–1.5 m in an excavation at Ringe on the island

of Funen, Denmark. The technique for obtaining an undisturbed column in the field andŽ .installing it in the laboratory has been described by Jørgensen et al. 1998b . The

technique ensures that the column is intact with respect to the bioporesrfractures, andthat the temperature and confining pressure during the laboratory experiment are similarto the field situation. Fig. 1 shows an outline of the column set-up. The flow through thecolumn was driven by a peristaltic pump. The temperature of the column varied between

Ž .11 and 138C, and the confining pressure was approximately 0.3 bar 30 kPa .After the conclusion of the dissolved creosote compounds infiltration experiment the

Ž .column was infiltrated with a dense non-aqueous phase liquid trichloroethylene , andfinally, the column was dismantled and dissected to map the fracturesrbiopores and the

Ž .flow pattern of trichloroethylene Jørgensen et al., 1998a .

2.2. Characterisation of the clayey till

The geology and fracturerbiopore structure at the field site have been described byŽ .Klint and Fredericia 1995 . The characteristics of the clayey till are listed in Table 2.

The till was carbonate free and relatively soft.The structure of the clayey till column was characterised by biopores and it was not

possible to recognize any distinct fracture system. At the field site, at a depth of 0.8 mbelow ground surface 500 biopores my2 with diameters between 2 and 5 mm were


Fig. 1. Set-up of the column experiment.

Ž .counted Klint and Fredericia, 1995 . In the laboratory, 186 biopores were counted in a2 y2 Ž0.2 m cross-section of the column corresponding to 950 pores m Jørgensen et al.,.1998a . In both cases, the numbers have been found from counting the pores on small

subareas.The bulk hydraulic conductivity of the column was measured as 2.75=10y6 m sy1

prior to the injection of chemicals. During that hydraulic test, steady state flow rateswere measured at different applied hydraulic gradient. A straight line relationshipbetween flow rate and applied gradient was observed from which the bulk hydraulic

Ž .conductivity was calculated Jørgensen et al., 1998a .

2.3. Influent water

The influent water was tap water originating from a limestone aquifer. The relevantchemicals in the tap water are listed in Table 3. The following chemicals were added to

y1 Ž .the tap water: 2 g l of sodium azide NaN to poisonrinhibit the bacterial activity in3y1 Ž .the column, 200 mg l of sodium sulfite Na SO to reduce the oxygen in the water,2 3

y1 Ž .100 mg l of lithium bromide LiBr as a conservative tracer, and the organiccompounds. Sodium azide at a concentration of 2 g ly1 has been shown to be sufficient

Ž . y1to inactivate the bacteria in soil and water Lyngkilde et al., 1992 and 23 mg l has


Table 2Characterisation of the clayey till in the column

Ž .Sampling depth m 1–1.5b dpH 6.95

y1 a,e dŽ Ž . .CEC m.equi. 100 g soil 8.8a dŽ .Content of org. matter % 0.09

cŽ . Ž .Clay content -0.002 mm % 19.0cŽ . Ž .Fine silt 0.02–0.002 mm % 11.7

cŽ . Ž .Coarse silt and sand 2–0.02 mm % 66.2cŽ . Ž .Small stones and gravel )2 mm % 3.1

2 y1 a dŽ .Specific surface area m g 14.1cPorosity 0.35

a dMineralogy dominated by quartz and feldsparDominating features biopores

cNumber of biopores 186 in totaly6Bulk hydraulic conductivity measured 2.75=10

y1 cŽ .before the experiment m sy8Bulk hydraulic conductivity measured 5.4=10

y1Ž .during the experiment m s

a Ž .Broholm et al. 1999a .b Ž . Ž y1 .Broholm et al. 1999a , pH was measured in a solution of CaCl 0.01 mol l using a soil to liquid ratio of2

1 to 2.5.c Ž .Jørgensen et al. 1998a .dAverage values for samples obtained at a depth of 1.2 and 1.75 m.eCEC is the cation exchange capacity.

Ž .been shown to inhibit nitrification in activated sludge by 75% Henze et al., 1995 .Sodium sulfite at a concentration of 200 mg ly1 can reduce 25.3 mg O ly1, hence2

sulfite was present in surplus to remove any oxygen that might contaminate the influentwater.

The influent water was prepared in a 5-l glass bottle filled with 5 l of tap water. Theinorganic compounds were added to the water, and subsequently, a 5-ml aliquot of theorganic stock solution, prepared by dissolving the organic compounds to knownconcentrations in methanol, was added. The bottle was then closed with a rubberstopper, and shaken until the organic and inorganic compounds were completelydissolved. The water was then transferred from the bottle and into a Tedlar w bag via a

Ž .tube. The filled bag was placed in a cooler at approximately 18C to prevent bio de-gradation. The bag was connected to the influent system of the column via a pump andTeflonw tubes. Since water samples were taken directly from the bag the possible lossduring preparation and handling are not important.

The column was infiltrated with water containing only sodium azide and sodiumsulfite for 5 days prior to the injection of organic compounds in order to poisonrin-activate the bacteria in the column. During this acclimatization period, the flow rate was

Ž y1 .low, and significant concentrations of oxygen 1.2–5.7 mg O l were detected in the2

effluent from the column. However, since the column was abiotic this did not influencethe experiment, and the injection of organic compounds was initiated although oxygenwas still detectable in the effluent.


Table 3Ž .Measured flow and inorganic parameters during the experiments average"standard deviation

Influent Effluent

Ž . Ž .pH 7.86 "0.12 6.80 "0.19y y1 aŽ . Ž .NO mg N l 0.5–0.8 0.29 "0.273y y1Ž .NO mg N l -0.012q y1Ž . Ž .NH mg N l 0.22 "0.064

y1Ž .O mg l 02y y1Ž . Ž .Br mg l 93.2 "12.1 see Fig. 3qq y1 aŽ .Ca mg l 94–96qq y1 aŽ .Mg mg l 22–25

q y1 aŽ .K mg l 4.3–5.2q y1 a,bŽ .Na mg l 33–105qq y1 aŽ .Fe mg l 0.04–0.06

qq y1 aŽ .Mn mg l -0.005–0.01yy y1 aŽ .SO mg l 14–234

y y1 aŽ .HCO mg l 378–3913y1Ž .Flow rate ml day 219

1353

a Ž . Ž .From Gentofte Community 1997 and Lyngby–Tarbæk Community 1998 .˚bConcentration before addition of chemicals to the water.

The different phases of the column experiment are listed in Table 4. All subsequentreferences to time are relative to the time when the addition of organic compounds wasinitiated.

2.4. Sampling procedures

Bromide samples were collected in 16-ml glass vials which were capped withTeflonw-coated septa. Samples for oxygen were collected in 12-ml volumetric glassvials with no head space. The samples were analyzed within a day after they were taken.

Effluent water for analysis of organic compounds was sampled in preweighed 100- orw Ž .250-ml Pyrex glass bottles containing 20 ml of predistilled dichloromethane CH Cl .2 2

The effluent water samples were collected using a flow-through pipette. The flow-throughpipette was a 200-ml pipette installed vertically, that the effluent water passed. Analuminium valve was located just below the pipette which allowed sampling of water

Table 4Important phases of the experiment

Phase Days after injectionof organic compounds

The injection of the anaerobic water started y10The injection of sodium azide started y5The injection of LiBr and the organic compounds started 0The flow rate increased 24The injection of LiBr and the organic compounds stopped 106Conclusion of the experiment 139


from the pipette. Thus, samples were obtained in less than 1 min. The influent watersamples were collected from the Tedlar w bag via an aluminium valve. This also alloweda sampling time of less than 1 min. The bottles were tightly closed with screw caps withTeflonw-coated septa, shaken to extract the organic compounds from the aqueous phaseinto the solvent phase, and subsequently stored in the dark at 18C until analyzed.

2.5. Analytical procedures

Ž . ŽThe samples were spiked with approximately 1 ml internal standard IS solution l.y1water sample prior to extraction of the aqueous phase. The IS solution consisted of

Ž .y1approximately 10 mg 1-methyl-4-tert-butyl-benzene l predistilled CH Cl . The2 2

water and organic phases were separated after spiking in a separating funnel. The waterphase was further extracted using another two portions of 15 and 10 ml predistilledCH Cl . The combined CH Cl phases were concentrated to about 1 ml using a rotary2 2 2 2

evaporator and a gentle stream of air, in succession.The concentrated extracts were analyzed by gas chromatography using a HPw 5890

Ž .gas chromatograph equipped with a flame ionisation detector FID, 3258C , an on-col-Žumn injector, and a JW-DB5 fused silica capillary column 60 m=0.23 mm i.d.=0.1

. Ž .mm film . Helium was used as the carrier gas 1.75 bar . The organic compounds in 0.3ml injected sample were separated by applying the following temperature program: 308Cfor 10 min, 30–1208C at 7.58C miny1, 1208C for 10 min, 120–2208C at 208C miny1,2208C for 8 min, 220–3108C at 208C miny1 and finally, 3108C for 5.5 min.

Data acquisition and integration of peaks was accomplished using a HP ChemSta-w Ž y1 .tion . Peak areas were converted to concentrations mg l by normalising to the

known amount of IS in the sample.Furan has been excluded from this discussion because it could not be separated from

the solvents peak during the analysis.ŽDissolved oxygen was measured using the Winkler Azide modified method Eaton et

. Ž .al., 1995 modified for smaller sample volume approximately 12 ml instead of 118 ml .Bromide was measured by ion-chromatography on a Dionex w 2010i equipped with

w Ž . w Ž .an Ionpac AG4A 10–32 guard column, an Ionpac AS4A 10–32 column and aconductivity detector. The eluent was water containing 1.8 mmol carbonate ly1 and 1.7mmol bicarbonate ly1.

ŽThe pH was measured by a pH-electrode and a pHrmV-meter JK 9200 Buch and.Holm .

The organic and inorganic compounds used for preparation of solutions and forextractions were all of analytical grade.

3. Results

3.1. Flow

The flow rate, the accumulated flow, and the hydraulic heads in the column as afunction of time are shown in Fig. 2. The average flow rate was 219 ml dayy1


Ž . Ž . Ž .Fig. 2. Flow rate e , influent head B and effluent head l as a function of time and accumulated flowŽ .I .

Ž y1 .corresponding to an infiltration rate of 1.1 mm day for the first 24 days, and wasincreased to about 1800 ml dayy1 because the observed increase in effluent concentra-tions of bromide and the organic compounds was slow. The figure reveals that the flowrate varied considerably due to pump instabilities. The average flow rate during the

y1 Žperiod of high flow rate was 1353 ml day corresponding to an infiltration rate of 6.9y1 . Ž .mm day Table 3 .

Based on the flow rate and the hydraulic heads, the bulk hydraulic conductivity of thecolumn was calculated as 5.4=10y8 m sy1, which is 50 times lower than the bulk

Žhydraulic conductivity measured prior to the injection of chemicals Jørgensen et al.,.1998a . A detailed discussion of the changes in hydraulic conductivity of the column has

Ž .been included in Jørgensen et al. 1998a .

3.2. Bromide

The relative concentration of bromide as a function of time is shown in Fig. 3. Therelative bromide concentration is the measured bromide concentration divided by the

Ž .average influent concentration Table 3 . For the first 24 days of the experiment, theaverage flow rate was 219 ml dayy1. During this period, the bromide concentrationincreased gradually and slowly. In order to increase the transport, the flow rate wasincreased, and after approximately 60 days the relative bromide concentration ap-proached one. At 106 days after the start of the experiment, bromide was removed fromthe influent water and the column was leached with bromide free water. The relativebromide concentration decreased within a day from approximately 1 to 0.25, whereaftera leaching tail was observed. Due to a relatively high detection limit for bromide, thelowest relative concentration of bromide shown in the figure is approximately 0.1.

It appears that the increase in the relative concentration of bromide was much slowerthan the corresponding decrease in relative concentration. However, flow disturbances at


Ž . Ž .Fig. 3. Relative concentrations of bromide v and p-xylene e as a function of time.

Ž .the time of the flow increase to the column Fig. 2 may explain the bromideconcentration behaviour at that time.

3.3. Organic compounds

The average measured concentrations and the standard deviations of the organiccompounds in the influent water are listed in Table 1. The influent concentrations of theorganic compounds were relatively constant with relative standard deviations between 6and 14%, except for some of the PAHs and the high-molecular-weight NSO-compounds,especially acridine, carbazole, and dibenzothiophene, which had higher relative standarddeviations. The average influent concentrations were based on analysis of 23 watersamples. The relative standard deviations were based on the sum of variation includingvariations in preparing stock solutions, adding the stock solution to the influent water,sampling and analysis.

The relative effluent concentrations as a function of time for 20 of the 24 organiccompounds are shown in Figs. 3–8. The relative concentrations of the organic com-pounds are the concentrations in the effluent divided with the average influent concen-trations. For comparison, the relative concentration of bromide is also shown in thefigures. The curves have been characterised by the time to reach a relative concentrationof 0.5. Those times are shown in Table 1. For the organic compounds that did not reacha relative concentrations of 0.5 during the experiment, the concentrations they reached atDay 106 when the injection of organic compounds ended are shown in Table 1 instead.

The breakthrough curve for p-xylene, shown in Fig. 3, reveals that it behavedsimilarly to bromide except that the relative concentration of bromide decreased morerapidly than the relative concentration of p-xylene. Benzene, toluene, ethylbenzene, and

Ž .o-xylene behaved similarly to p-xylene observations not shown in the figure . The time


Ž . Ž . Ž . Ž .Fig. 4. Relative concentrations of bromide v , naphthalene B , 1-methylnaphthalene I , fluorene l ,Ž .and phenanthrene e as a function of time.

to reach a relative concentration of 0.5 was 36–36.5 for the BTEXs compared to 36.5Ž .for bromide Table 1 .

Ž .Among the four PAHs Fig. 4 , naphthalene and 1-methylnaphthalene were slightlyattenuated relative to bromide based on the time to reach a relative concentration of 0.5of 38–48 and 48–51 days. Fluorene and phenanthrene were significantly attenuated,since they reached only a maximum relative concentration of 0.2 and 0.06 after 106days.

Ž . Ž . Ž . Ž .Fig. 5. Relative concentrations of bromide v , phenol B , o-cresol I , 2,4-dimethylphenol l , andŽ .3,5-dimethylphenol e as a function of time.


Ž . Ž . Ž . Ž .Fig. 6. Relative concentrations of bromide v , benzothiophene I , benzofuran B , dibenzofuran l , andŽ .dibenzothiophene e as a function of time.

The phenolic compounds were attenuated relative to bromide in the following order:Ž .phenol-o-cresol-3,5-dimethylphenols2,4-dimethylphenol Fig. 5 . The relative

concentrations of the phenolic compounds reached a maximum of 0.5–0.8 at Day 106.There are considerable variations especially on the breakthrough curves for the dimeth-ylphenols. These were due to uncertainty in the extraction efficiency and analysis of thephenolic compounds.

Among the SO-compounds, benzothiophene and benzofuran were slightly attenuatedwhereas dibenzofuran and especially dibenzothiophene were significantly attenuated

Ž . Ž . Ž . Ž .Fig. 7. Relative concentrations of bromide v , quinoline B , 2-methylquinoline I , and acridine l as afunction of time.


Ž . Ž . Ž . Ž .Fig. 8. Relative concentrations of bromide v , indole l , pyrrole B , 1-methylpyrrole I , and carbazoleŽ .e as a function of time.

Ž .Fig. 6 . The relative concentration of dibenzofuran reached 0.18 and the relativeconcentration of dibenzothiophene was 0.05 at Day 106.

The basic N-compounds shown in Fig. 7 were attenuated in the following order:quinoline-acridine-2-methylquinoline. The breakthrough curves for these com-pounds also showed considerable variation caused by uncertainty in the recovery andanalysis of the basic N-compounds.

Among the neutral N-compounds shown in Fig. 8, pyrrole behaved like bromidewhereas 1-methylpyrrole and indole were slightly attenuated and carbazole was signifi-cantly attenuated.

ŽSummarizing the breakthrough curves for all the organic compounds as listed in.Table 5 the following order of break through was observed: benzenespyrroles

toluene s o-xylene s p-xylenesethylbenzenesphenolsbenzothiophenesbenzofu-ran-naphthalene-1-methylpyrrole-1-methylnaphthalenes indoleso-cresolsqui-noline-3,5-dimethylphenol s 2,4-dimethylphenol - acridine-carbazole - 2-meth-ylquinoline- fluorene-dibenzofuran-phenanthrenesdibenzothiophene. The indi-vidual order of indole, o-cresol, and quinoline is uncertain.

3.4. Mass balances

The influent and effluent masses were calculated by integration of the measuredconcentrations with time multiplied with the corresponding average flow rate. Therecovery defined as the effluent mass relative to the influent mass is listed in Table 1.The recoveries are estimated to 0.88–0.97 for the BTEXs, 0.33–0.63 for the phenoliccompounds, 0.20–0.71 for the PAHs, 0.28–0.88 for the N-compounds, and 0.04–0.73


Table 5The order of retardation based on the column, batch sorption and diffusion experiments

Column experiment Batch sorption experiment Diffusion experiment

Benzene Phenol BenzenePyrrole o-Cresol TolueneToluene 3,5-Dimethylphenol Benzofurano-Xylene Benzene Phenolp-Xylene Toluene o-XyleneEthylbenzene o-Xylene p-XyleneBenzothiophene p-Xylene EthylbenzeneBenzofuran 2,4-Dimethylphenol o-CresolPhenol Quinoline 2,4-DimethylphenolNapthalene Ethylbenzene 3,5-Dimethylphenol1-Methylpyrrole Benzothiophene Benzothiophene1-Methylnaphthalene Naphthalene NaphthaleneIndole Indole Quinolineo-Cresol Benzofuran 1-MethylnapthaleneQuinoline Acridine 2-Methylquinoline2,4-Dimethylphenol 2-Methylquinoline Flourene3,5-Dimethylphenol 1-Methylnaphthalene DibenzofuranAcridine Carbazole CarbazoleCarbazole Flourene Phenanthrene2-Methylquinoline Dibenzofuran DibenzothiopheneFlourene DibenzothiopheneDibenzofuran PhenanthrenePhenanthreneDibenzothiophene

for the SO-compounds. A similar mass balance of bromide showed that 0.77 of theŽ .injected mass of bromide was recovered from the column Table 1 .

4. Discussion

4.1. Mass balances

Among the organic compounds the mass balances of the BTEXs revealed recoveriesŽ .of 0.87–0.97, which show that the BTEXs were not bio degraded. In contrast, the mass

balances of the phenolic compounds revealed recoveries of 0.33–0.63. Low recoveriesof -0.20 were observed for phenanthrene, dibenzothiophene, dibenzofuran, and fluo-rene. The low recoveries observed for some of the organic compounds may be caused byinsufficient time for leaching of the organic compounds after they were removed from

Ž .the influent, or explained by bio degradation. As an example, the breakthrough curvesfor phenanthrene and fluorene show that during the leaching period of 33 days, theeffluent concentrations of these organic compounds did not decrease significantly.Therefore, a significant mass of at least the high-molecular-weight organic compoundswere still in the column at the conclusion of the experiment.


Biodegradation may occur if the addition of sodium azide does not inhibit or kill thebacterial activity. However, since oxygen was absent from the influent water, the onlyoxygen present in the system was oxygen initially dissolved in the pore water. Assumingan oxygen concentration of 10 mg O ly1 in the column’s pore water, this amount is2

only sufficient to biodegrade -5% of the organic compounds injected. The influentwater contained less than 1 mg NOy–N ly1 which is not sufficient to sustain a3

significant removal of organic compounds. Other electron acceptors like iron andsulphate are abundant in the clayey till and the influent water, and may sustainbiodegradation of the organic compounds. However, only some of the organic com-pounds have been shown to be biodegradable at iron- and sulphate-reducing conditions.

The observed difference in the recoveries between the BTEXs and the phenoliccompounds is unexpected since those organic compounds have similar characteristicswith respect to diffusion and sorption, the two processes which control the transport ofthe organic compounds in bioporous medium. However, biodegradation is unlikelybecause it has to occur with iron, sulphate or carbon dioxide as electron acceptors. Some

Žphenolic compounds have been shown to be biodegradable under iron- Nielsen et al.,. Ž .1995 , sulphate-reducing Mort and Dean-Ross, 1994 , and methanogenic conditions

Ž .Godsy et al., 1992 , but also some BTEXs are biodegradable under those conditions.Therefore, a low recovery of some of the BTEXs should also have been observed in casethat biodegradation occurred.

Abiotic degradation of the phenolic compounds may also occur. The phenoliccompounds may have been polymerized, in which case they would not have beendetected by the analysis technique applied here, or they may have been convertedabiotically to smaller molecules. However, both processes require different catalysts

Žandror high temperatures Thornton et al., 1991; Li and Shieh, 1994; Ikeda et al., 1996;.Atwater et al., 1997 . It is not possible to determine whether some of the necessary

catalysts were present in the clayey till. Consequently, a plausible explanation for theobserved removal of the phenolic compounds can not be given but it is not likely to be aresult of biodegradation.

4.2. Retardation

The influence of sorption on the transport of the organic compounds through thecolumn was evaluated based on the observed breakthrough curves. The observed orderin the column experiment was as listed in Table 5. As the organic compounds have

Ž .similar diffusion coefficients in water Broholm et al., 1999c , the difference inretardation of the organic compounds in the column is primarily a result of differences

Žin their sorption to the soil material which is reflected by their retardation factors Table.1 .

Multi-solute batch sorption experiments were carried out with the same mixture oforganic compounds and clayey till from the same site, but using two different clayey tillŽ . Ž . Ž . Ž .solid to aqueous phase liquid ratios s:l-ratios by Broholm et al. 1999b . At highs:l-ratio, sorption isotherms close to linear isotherms were observed. The order ofretardation based on the sorption distribution coefficients of the best fit linear isotherms


Ž .K -values was: phenol s o-cresol - 3,5-dimethylphenol - benzene - toluene sd

o-xylene s p-xylenes2,4 - dimethylphenol squinoline s ethylbenzene - benzothio-phenesnaphthalene- indolesacridine-1-methylnaphthalenes2-methylquinolines

Ž . Ž .benzofuran - pyrrole - carbazole - 1-methylpyrrole - fluorene s dibenzofuranŽ .-dibenzothiophenesphenanthrene Table 5 . The ranking of the two organic com-

pounds in brackets is unreliable due to inaccurate determination of the distributioncoefficients. At low s:l-ratio, highly non-linear sorption isotherms with a dramaticincrease in sorption at high total solute concentrations were observed for 2-methyl-quinoline, carbazole, fluorene, dibenzofuran, dibenzothiophene, and phenanthrene. Thisbehaviour would influence the retardation of these organic compounds and might resultin a different order of retardation.

Diffusion experiments were carried out with the same compound mixture on twoŽ .clayey till cores from the same site by Broholm et al. 1999c . The resulting diffusion

profiles in the clayey till cores revealed increased sorption of 2-methylquinoline,carbazole, fluorene, dibenzofuran, dibenzothiophene, and phenanthrene, and decreasedsorption of BTEXs, the phenolic compounds, benzofuran, benzothiophene, and naph-thalenes at high total solute concentration. The apparent retardation of the organiccompounds based on the diffusion experiment was derived from the total masses of theindividual organic compounds diffused into the cores and the concentrations of thecompounds in the reservoirs. The order of the apparent retardation was: benzenestoluenesbenzofuran-phenolso-xylenesp-xylenesethylbenzeneso-cresol-3,5-dimethylphenol s 2,4 - dimethylphenol - benzothiophene - naphthalene s quinoline-1-methylnaphthalene -2-methylquinoline s fluorenesdibenzofuranscarbazole -

Ž .phenanthrene-dibenzothiophene Table 5 . The apparent retardation of pyrrole, 1-methylpyrrole, indole, and acridine could not be quantified with sufficient accuracy bythe method employed. The ranking of organic compounds was the same in the two

Ž .cores, except for 2-methylquinoline and carbazole less significant . The diffusionexperiments indicated less retardation of 2-methylquinoline compared to fluorene anddibenzofuran based on one core, and greater retardation based on the other core, andvisa versa for carbazole. The results of the diffusion experiment indicate a shift in theorder of retardation of polar organic compounds relative to neutral organic compounds,with relatively higher retardation of the polar organic compounds. For example, phenolhas changed position relative to benzene and toluene, and 2-methylquinoline is retardedrelative to 1-methylnaphthalene, and 2-methylquinoline is retarded as much as fluoreneand dibenzofuran.

The order of retardation based on the observed breakthrough curves from the columnexperiment reported in this paper differs from the expected order based on the linear

Ž .sorption isotherm partitioning coefficients Table 5 . The order of retardation is similarto what might be expected based on the apparent retardation observed in the diffusionexperiment, i.e., the polar compounds has shifted relative to the neutral compoundsŽphenolic compounds later relative to the BTEXs, N-compounds later relative to the

.naphthalenes the first compounds break through very fast and the latest much later. Thisstrongly indicates that the transport of the organic compounds was influenced by thecomplex mixture of organic compounds at high total solute concentrations which causedincreased sorption of some organic compounds and decreased sorption of others.


4.3. Sorption kinetic

The experiment using another column from the site showed that only five of theŽorganic compounds carbazole, dibenzofuran, fluorene, dibenzothiophene, and phenan-

. Ž .threne were retarded Broholm et al., 1999d , whereas about 18 of the organiccompounds in the present experiment were retarded relative to bromide. One differencein the two column experiments was that the flow rate was lower for the first 24 days inthis experiment. Another difference was that the clayey till in the column experiment

Žreported here was bioporous whereas the till in the other column was fractured Broholm.et al., 1999d . In the fractured clayey till the dominant flow is in the fractures.

Therefore, the velocities in the fractures will be high and the time for sorption will berelatively low. In bioporous clayey till, the number of pores is numerous and thevelocity in them will therefore be lower, consequently the time for sorption will be

Ž .higher. This is consistent with column experiments by Jørgensen et al. 1998b whichshowed similar kinetic effects on pesticide sorption at high flow rates. Therefore, thestructure of the clayey till may be important for sorption. Additionally, the water flux inthe fractured clayey till column was larger than the flux in the bioporous clayey tillcolumn for the first 24 days resulting in decreased time for sorption. Experiments withthe clayey till from the field site have revealed that the time required to reach sorption

Ž .equilibrium is 3–4 days for dibenzofuran Broholm et al., 1999a . Other studies havestated the time required for quinoline sorption onto different soils to reach equilibrium is

Ž .4 h Zachara et al., 1986 and PAH sorption onto different sediments and soils reachesŽ .equilibrium in less than 20 h Means et al., 1980 . The average water velocity in the

fractures of the column has been estimated to be 14 m dayy1 at a hydraulic gradient ofŽ0.4 corresponding to a residence time in the column of less than 1 h Jørgensen et al.,

.1998a . Therefore, it is not likely that sorption in the fractures is at equilibrium.Transport in the matrix is controlled by diffusion resulting in much higher residencetimes than in the fractures, consequently matrix sorption is likely at equilibrium.

5. Conclusions

Sorption of organic compounds during transport was studied using a large undis-turbed column of clayey till which was supplied with sodium azide to prevent biodegra-dation.

The column experiment has shown that transport of the low-molecular-weight organiccompounds through fractured clayey till is almost as rapid as bromide-transport.

Based on the observed breakthrough curves the following order of retardation wasŽ .observed increasing retardation : benzenespyrroles tolueneso-xylenesp-xylenes

ethylbenzene s phenol s benzothiophenesbenzofuran-naphthalene-1-methylpyr-role-1 -methylnaphthalene s indole s o-cresol s quinoline-3,5 -dimethylphenols2,4 -dimethylphenol-acridine-carbazole-2 -methylquinoline- fluorene-dibenzo-furan-phenanthrenesdibenzothiophene. This order was unexpected based on theoctanol–water distribution coefficients of the organic compounds, and based on theresults of batch sorption experiments. However, the order compared reasonably wellwith the order of retardation observed in the diffusion experiments.


As a consequence of the fast transport, a thin clayey till cover of the type described inthis paper does not protect groundwater against contamination by low-molecular-weightorganic compounds.

Acknowledgements

This project was funded through the Strategic Environmental Research Programme,Denmark. The present paper constitutes part of a larger research programme focusing ontransport and biodegradation of creosote compounds in fractured clayey tills.

References

Atwater, J.E., Akse, J.R., McKinnis, J.A., Thompson, J.O., 1997. Low temperature aqueous phase catalyticoxidation of phenol. Chemosphere 34, 203–212.

Bailey, G.W., White, J.L., Rothberg, T., 1968. Adsorption of organic herbicides by montmorillonite: role ofpH and chemical character of adsorbate. Soil Sci. Soc. Am. Proc. 32, 222–234.

Broholm, K., Arvin, E. Hansen, A.B., Jørgensen, P.R., Hinsby, K. 1995. The fate of dissolved creosotecompounds in an intact fractured clay column. In: Proceedings of the International Conference on

Ž .Groundwater Quality: Remediation and Protection GQ95 . Prague, May 15–18, pp. 115–123.Broholm, M.M., Broholm, K., Arvin, E. 1999a. Sorption of heterocyclic compounds on natural clayey till. J.

Ž .Contam. Hydrol. submitted .Broholm, M.M., Broholm, K., Arvin, E. 1999b. Sorption of heterocyclic compounds from a complex mixture

Ž .of coal-tar compounds on natural clayey till. J. Contam. Hydrol. submitted .Broholm, M.M., Broholm, K., Arvin, E. 1999c. Diffusion of heterocyclic compounds from a complex mixture

Ž .of coal-tar compounds in natural clayey till. J. Contam. Hydrol. submitted .K. Broholm, A.B. Hansen, P.R. Jørgenen, E. Arvin, M. Hansen, 1999d. Transport and biodegradation of

Ž .dissolved creosote compounds in an intact fractured clayey till column. J. Contam. Hydrol. submitted .ŽDanish EPA, 1990. Risikovurdering af Forurenede Grunde. Miljøprojekt nr. 123. Risk Assessments of

. Ž .Contaminated Sites, in Danish , Miljøstyrelsen Danish Environmental Protection Agency , Copenhagen,Denmark.

D’Astous, A.Y., Ruland, W.W., Bruce, J.R.G., Cherry, J.A., Gillham, R.W., 1989. Fracture effects in theshallow groundwater zone in weathered Sarnia area clay. Can. Geotech. J. 26, 43–56.

Eaton, A.D., Clesceri, L.S., Greenberg, A.E., 1995. Standard Methods in Examination of Water andWastewater, 19th edn., APHA, AWWA, WEF.

Environment Canada, 1993. Creosote-impregnated Waste Materials. Canadian Environmental Protection Act,Priority substances list, Assessment report, Government of Canada, Environment Canada, and HealthCanada, Ottawa, Ontario.

Fredericia, J., 1990. Saturated hydraulic conductivity of clayey tills and the role of fractures. Nord. Hydrol. 21,119–132.

Gentofte Community, 1997. Unpublished water quality data for Sjælsø waterworks.Godsy, E.M., Goerlitz, D.F., Grbic-Galic, D., 1992. Methanogenic degradation kinetics of phenolic com-´ ´

pounds in aquifer-derived microcosms. Biodegradation 2, 211–221.Hansch, C., Leo, A., 1979. Substituent Constants for Correlation Analysis in Chemistry and Biology. Wiley,

New York, NY, USA.Hassett, J.J., Means, J.C., Banwart, W.L., Wood, S.G., Ali, S., Khan, A., 1980. Sorption of dibenzothiophene

by soils and sediments. J. Environ. Qual. 9, 184–186.Henze, M., Harremoes, P., Jansen, J.L.C., Arvin. E., 1995. Wastewater Treatment. Biological and Chemical¨

Processes. Springer, Berlin, Germany.


Hinsby, K., McKay, L.D., Jørgensen, P.R., Lenczewski, M., Gerba, C.P., 1996. Fracture aperture measure-ments and migration of solutes, viruses, and immiscible creosote in a column of clay-rich till. GroundWater 34, 1065–1075.

Ikeda, R., Sugihara, J., Uyama, H., Kobayashi, S., 1996. Enzymatic oxidative polymerization of 2,6-dimethyl-phenol. Macromolecules 29, 8702–8705.

Johansen, S.S., Hansen, A.B., Mosbæk, H.M., Arvin, E., 1997. Characterization of heteroaromatic and otherorganic compounds in groundwater at creosote-contaminated sites in Denmark. Ground Water Monit. Rem.17, 106–115.

Jørgensen, P.R., Fredericia, J., 1992. Migration of nutrients, pesticides, and heavy metals in clayey till.Geotechnique 42, 67–77.

Jørgensen, P.R., Foged, N., 1994. Pesticide leaching in intact blocks of clayey till. In: XIII ICSMFE. NewDelhi, India, pp. 1661–1664.

Jørgensen, P.R., Broholm, K., Sonnenborg, T.S., Arvin, E., 1998a. DNAPL transport through macroporousclayey till columns. Ground Water 36, 651–660.

Jørgensen, P.R., McKay, L.D., Spliid, N.H., 1998b. Evaluation of chloride and pesticide transport in afractured clayey till using large undisturbed columns and numerical modeling. Water Resour. Res. 34,539–553.

Ž .Katritzky, A.R. Ed. , 1963. Physical Methods in Heterocyclic Chemistry, Vol. 1: Nonspectroscopic Methods.Academic Press, New York.

Keller, C.K., van der Kamp, G., Cherry, J.A., 1986. Fracture permeability and groundwater flow in clayey tillnear Saskatoon Saskatchewan. Can. Geotech. J. 23, 229–240.

Ž .Klint, K.E., Fredericia, J., 1995. Parameters for fractures in clayey till In Danish . Vand & Jord 2, 208–214.Korsgaard, T., Petersen, C.R., Nielsen, C., Andersen, L., Michaelsen, O., Skaarup, J., Borg, D., Andersen, J.,

Bjerre, B., Henriksen, P., 1989. Forurenede gasværksgrunde. Report no. U4, Danish EnvironmentalŽ .Protection Agency, Copenhagen In Danish .

Li, K.-T., Shieh, D.-T., 1994. Polymerization of 2,6-dimethylphenol with mixed-ligand copper complexes. Ind.Eng. Chem. Res. 33, 1107–1112.

Lotimer, A.R., Belanger, D.W., Whiffin, R.B. 1992. Occurrence of coal tar and contaminated groundwater atŽ .three sites in Canada. In: Weyer Ed. , Subsurface Contamination by Immiscible Fluids, International

Conference on Subsurface Contamination by Immiscible Fluids, the International Association of Hydroge-ologist, Galgary, Alberta, Canada, April 18–20, 1990. Balkema, Rotterdam, pp. 411–416.

Lyngby–Tarbæk Community, 1998. Unpublished water quality data for Dybendahl waterworks.˚Lyngkilde, J., Christensen, T.H., Gillham, R.W., Larsen, T., Kjeldsen, P., Skov, B., Foverskov, A. and

O’Hannesin, S., 1992. Degradation of specific organic compounds in leachate-polluted groundwater, Chap.Ž .4.3. In: Christensen, T.H., Cossu, R., Stegman, R. Eds. , Landfilling of Waste: Leachate. Elsevier,

London, pp. 485-495.Mackay, D., Shiu, W.Y., Ma, K.C., 1992a. Handbook of Physical–chemical Properties and Environmental

Fate for Organic Chemicals, Vol. 1, Monoaromatic Hydrocarbons, Chlorobenzenes, and PCBs. LewisPublisher, London, UK.

Mackay, D., Shiu, W.Y., Ma, K.C., 1992b. Handbook of Physical–chemical Properties and EnvironmentalFate for Organic Chemicals, Vol. 2, Polynuclear Aromatic Hydrocarbons, Polychlorinated Dioxines, andDibenzofurans. Lewis Publisher, London, UK.

McKay, L.D., Cherry, J.A., Bales, R.C., Yahya, M.T., Gerba, C.P., 1993a. A field example of bacteriophageas tracers of fracture flow. Environ. Sci. Technol. 27, 1075–1079.

McKay, L.D., Cherry, J.A., Gillham, R.W., 1993b. Field experiments in a fractured clay till: 1. Hydraulicconductivity and fracture aperture. Water Resour. Res. 29, 1149–1162.

McKay, L.D., Cherry, J.A., Gillham, R.W., 1993c. Field experiments in a fractured clay till: 2. Solute andcolloid transport. Water Resour. Res. 29, 3879–3890.

Means, J.C., Wood, S.G., Hassett, J.J., Banwart, W.L., 1980. Sorption of polynuclear aromatic hydrocarbonsby sediments and soils. Environ. Sci. Technol. 14, 1524–1528.

Mort, S.L., Dean-Ross, D., 1994. Biodegradation of phenolic compounds by sulphate-reducing bacteria fromcontaminated sediments. Microb. Ecol. 28, 67–77.

Mueller, J.G., Chapman, P.J., Pritchard, P.H., 1989. Creosote-contaminated sites. Their potential for bioreme-diation. Environ. Sci. Technol. 23, 1197–1201.


Nielsen, P.H., Albrectsen, H.J., Heron, G., Christensen, T.H., 1995. In situ and laboratory studies on the fateof specific organic compounds in an anaerobic landfill leachate plume: I. Experimental conditions and fateof phenolic compounds. J. Contam. Hydrol. 20, 27–50.

Pearlman, R.S., Yalkowsky, S.H., Banerjee, S., 1984. Water solubilities of polynuclear aromatic andheteroaromatic compounds. J. Phys. Chem. Ref. Data 13, 555–562.

Ž .Raven, K.G., Beck, P., 1992. Coal tar and creosote contamination in Ontario. In: Weyer Ed. , SubsurfaceContamination by Immiscible Fluids, International Conference on Subsurface Contamination by Immisci-ble Fluids, the International Association of Hydrogeologist, Galgary, Alberta, Canada, April 18–20, 1990.Balkema, Rotterdam, pp. 401–410.

Rudolph, D.L., Cherry, J.A., Farvolden, R.N., 1991. Groundwater flow and solute transport in fracturedlacustrine clay near Mexico City. Water Resour. Res. 27, 2187–2201.

Ruland, W.W., Cherry, J.A., Feenstra, S., 1991. The depth of fractures and active groundwater flow in aclayey till plain in southwestern Ontario. Ground Water 29, 405–417.

Shiu, W.-Y., Ma, K.C., Varhanı . . . kova, D., Mackay, D., 1994. Chlorophenols and alkylphenols: a review and´ ´correlation of environmentally relevant properties and fate in an evaluative environment. Chemosphere 29,1155–1224.

Thomson, D. 1990. Identification of Open Wisconsinan Age Fractures in a Deep Clayey Till. MS thesis,Department of Earth Science, University of Waterloo, Waterloo, Ontario, Canada.

Thornton, T.D., LaDue, D.E. III, Savage, P.E., 1991. Phenol oxidation in supercritical water: formation ofdibenzofuran, dibenzo-p-dioxin, and related compounds. Environ. Sci. Technol. 25, 1507–1510.

Zachara, J.M., Ainsworth, C.C., Felice, L.J., Resch, C.T., 1986. Quinoline sorption to subsurface materials:role of pH and retention of the organic cation. Environ. Sci. Technol. 20, 620–627.

transport of creosote compounds in a large, intact, macroporous clayey till column

Documents