Chromatographic determination of aliphatic hydrocarbons and polyaromatic hydrocarbons (PAHs) in a sewage sludge

The Science of the Total Environment 220 Ž1998. 33]43

Chromatographic determination of aliphatic hydrocarbons and polyaromatic hydrocarbons Ž PAHs. in a sewage sludge J.M. Moreda, A. Arranz, S. Fdez De Betono, ˜ A. Cid, J.F. ArranzU Uni¨ ersidad del Pais Vasco, Facultad de Farmacia, Departamento de Quımica Analıtica, Apartado 450, ´ ´ Vitoria 01080, Spain Received 17 November 1997; accepted 15 June 1998

Abstract A simple chromatographic method, proposed by Aceves et al. Ž1988., for the determination of aliphatic hydrocarbons and polyaromatic hydrocarbons ŽPAHs. was used. The results from a study of the presence and temporal variability of the aliphatic hydrocarbons and polyaromatic hydrocarbons ŽPAHs. in sewage sludge are shown in this work. The sewage sludges originated from the Arazuri waste water treatment plant site in Pamplona ŽSpain.. The organic pollutants have been extracted from the sewage sludge by a Soxhlet apparatus. Aliphatic hydrocarbons and PAHs are separated from the rest of the pollutants on a chromatographic column. Flame ionization ŽFID. and mass spectroscopy ŽMS. detectors have been used. The results showed that aliphatic hydrocarbons concentration varied between 230 and 1420 mg kgy1 dry matter ŽDM.. The PAHs appeared in smaller quantitie of between 128 and 482 mg kgy1 ŽDM.. The factor analysis of the results allowed us to verify the different origin of the aliphatic hydrocarbons and the PAHs. Q 1998 Elsevier Science B.V. All rights reserved. Keywords: Aliphatic hydrocarbons; PAHs; Sludge; Pollutants

1. Introduction Inorganic, organic, pathogenic and microbiological pollutants frequently appear in sewage sludge generated by the treatment of urban and

U

Corresponding author. Universidad del Pais Vasco, Facultad de Farmacia, Departamento de Quımica Analıtica, Paseo ´ ´ de la Universidad, 7, 01006 Vitoria, Spain. Tel.: q34 945 183058; fax: q34 945 130756.

industrial waste water. They come from many sources: human excretion products, household chemicals, automobile fuels, lubricants, cleaning compounds, storm water run-off from highways, effluent from many different industries and fuel combustion products, which are deposited on urban soil and enter the waste water treatment station through the sewerage. In the depuration treatment, although the majority are retained in the sludge, these pollutants are implicated in several processes which have a

0048-9697r98r$ - see front matter Q 1998 Elsevier Science B.V. All rights reserved. PII S0048-9697Ž98.00238-1

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J.M. Moreda et al. r The Science of the Total En¨ ironment 220 (1998) 33]43

different dynamic nature. Some can evaporate and are subject to aerobic and anaerobic biodegradation, chemical transformation, etc ŽWild and Jones, 1992a.. Once the sludge has been treated in the depuration station it can be disposed of in different ways. The most commonly used procedures are: Ž1. the controlled waste landfill site; Ž2. application as a fertilizer; and Ž3. incineration and subsequent discharge to coastal systems. The first two options are the preferred choice in the European Union ŽCristobal, 1991.. The application of these sludges in agriculture can be advantageous to the soil because they modify soil structure and provide organic matter and nutrients. On the other hand, utilization as a fertilizer has some risks namely, the accumulation of pollutants in soils, plants ŽKampe, 1988., animal pastures ŽWild and Jones, 1992b. and the subsequent entry into the foodchain of dangerous compounds. The fixation of the organic pollutants by an agricultural soil and particularly their possible distribution among the soil particles and their dissolution, depends on climatic conditions and the soil’s physicochemical properties. For soils and sediments in which the clay content is relatively low, the fixation of the non-ionic organic compounds takes place fundamentally on the soil organic fraction. Microbial degradation is the most important mechanism for the elimination of many organic pollutants from the soil and depends upon several factors, such as temperature, humidity and the soil, etc. Simultaneously with these processes, abiotic degradation Žphotolysis, hydrolysis and oxidation. takes place. Other elimination pathways of soil pollutants are leaching and volatilization, which have special importance in the case of the most persistent pollutants. There are four main pathways through which a chemical from the soil can enter plants: Ž1. root uptake and subsequent transport in the transpiration stream; Ž2. foliar uptake of vapour from the surrounding air; Ž3. uptake by external contamination of shoots by soil and dust, followed by retention in the cuticle

or penetration through it; and Ž4. uptake and transport in oil channels which are found in some oil containing plants like carrots ŽWild and Jones, 1992a.. Considering these problems, it is necessary to control pollutant levels. Germany and the USA indicate maximum levels for these pollutants in sludges and soils ŽStark and Hall, 1992.. Other countries, such as Sweden are opposed to the use of the sludges as fertilizer in agricultural soil, while in Spain to date there are no regulations concerning the use of these sludges on agricultural soil. The organic contaminants present in the sewage sludge have been studied by a number of authors ŽCrathorne et al., 1989; Webber and Lesage, 1989; Leschber, 1992.. Among the most frequent contaminants found are: aromatic hydrocarbons, organochlorinated compounds, aliphatic hydrocarbons, amines, nitrosamines, phenols, esters, phthalates, etc. The origin of these pollutants is very diverse, coming from industrial processes ŽJunk and Ford, 1980; Gil, 1982; Kirton and Crisp, 1990; Guillem et al., 1992. and also from urban activities ŽTakada and Ishiwatari, 1990.. Among these sludges, the aliphatic hydrocarbons and PAHs have a high persistence in the environment, low biodegradability and high lipophility, some of them being highly toxic. Several aliphatic hydrocarbons and PAHs have a natural source as bacterium or terrestrial superior plants ŽClark and Blumer, 1967; Eglinton and Hamilton, 1967; Laflame and Hites, 1978; Wakeham et al., 1980; Saliot, 1981.. Other aliphatic and polyaromatic hydrocarbons have their origin in coal, petroleum and their derived products. They have also been formed from the combustion of coal, petroleum and wood ŽYoungblood and Blumer, 1975; Hites et al., 1980; Grimer et al., 1983; Prhal et al., 1984; Grimer et al., 1985.. The aim of this work is to characterize the aliphatic hydrocarbons and PAHs in the sludges from waste water treatment from the Arazuri Plant in Pamplona ŽSpain. and use of the sludge as a fertilizer.

J.M. Moreda et al. r The Science of the Total En¨ ironment 220 (1998) 33]43

2. Experimental 2.1. Sample collection and processing Nine sludge samples from the Arazuri sewage treatment plant were chosen, between September 1993 and July 1994. On first day of each month, a 3-kg sample of homogeneous wet sludge, was collected. Samples of 100 g were selected and stored in glass containers and then frozen to y308C until subsequent analysis. 2.2. Sample preparation and analysis The method used has been developed by Aceves et al. Ž1988. and it is described below. The following solvents were for residue analysis grade ŽMerck.: n-hexane, methanol, dichloromethane, isooctane and acetone. Analytical reagent grade ŽMerck. was used in these cases: potassium hydroxide pellets, potassium dichromate, copper fine powder, hydrochloric acid, sulfuric acid Ž96%. and alkaline detergent AP 13. Carburundum and cellulose extraction cartridges were provided by Carlo Erba and Albet, respectively. Neutral silica gel ŽKieselgel 40, 70]230 mesh. and alumina Žaluminium oxide 90 active, 70]230 mesh. obtained from Merck were used as adsorbents. They were cleaned by extraction with dichloromethane in a Soxhlet apparatus for 24 h and, after solvent evaporation, they were heated overnight for activation, at 120 and 3508C, respectively. After cooling in a desiccator they were deactivated by addition of milli-Q water Ž5%. and then homogenized. The adsorbents were kept in closed containers in a desiccator before use. Tetradecane Ž n-C 14 ., docosane Ž n-C 20 ., dotriacontane Ž n-C 32 . and hexatriacontane Ž n-C 36 . from Fluka were used as external standards for the aliphatic hydrocarbons. For the PAHs analysis phenanthrene, pyrene and perylene from Sigma were used as reference standards ŽGrimalt et al., 1984; Aceves et al., 1988.. All glass materials were first cleaned with a chromic acid mixture for 2 h and then rinsed with Milli-Q water. They were then, washed with alkaline detergent in ultrasonic bath for 10 min and they were rinsed several times using Milli-Q wa-

35

ter and dried in a oven at 1208C. The fine copper powder was activated using 6 M HCl, washed and finally rinsed with acetone which was carried out in an ultrasonic bath for 5 min. The KOH was washed with hexane in an ultrasonic bath. The paper paste cartridges and the carborundum were washed and then extracted with dichloromethane in a Soxhlet for 48 h ŽGrimalt et al., 1984.. Once the sample was unfrozen, 1 g of sludge was removed and placed into a paper paste cartridge for extraction in a Soxhlet apparatus with 150 ml of a dichloromethane-methanol Ž2:1. mixture for 48 h. The extract was then concentrated to a volume of 5 ml in a Turbo-Vap ŽVarian.. Later 50 ml of a solution of KOHrmethanol 6% was added and maintained for 12 h in the dark. The organic compounds were extracted using three 30-ml aliquots of hexane. Copper powder was added to the extract to desulfurise ŽGrimalt et al., 1986; Aceves et al., 1988. the sample and then the copper was eliminated by decantation and the sample was evaporated to 1 ml until its chromatographic separation. This operation was made in a 25-cm chromatographic column with an internal diameter of 0.9 cm. With the column filled by n-hexane, 8 g of silica gel and then 8 g of alumina were added. The aliphatic hydrocarbons were obtained in the first separation with 20 ml of n-hexane. Then, 20 ml hexanerdichloromethane Ž9:1. were passed through the chromatographic column and the second fraction was obtained. Finally, 40 ml hexanerdichloromethane Ž4:1. was added. These extracts were dried under a flow of nitrogen and then frozen to y308C until analysed ŽGrimalt et al., 1986; Aceves et al., 1988.. All samples were analyzed by gas chromatography ŽGC. with different detectors. The aliphatic hydrocarbons and PAHs analysis were performed with a Perkin Elmer Model 8310 equipped with a splitrsplitless injector and FID. The separation was carried out on a 30-m SPB-5 Žfilm thickness 0.25 m m. fused-silica capillary column ŽSupelco, USA. with an internal diameter of 0.32 mm. Injections were made in the splitless mode Žsplit valve closed for 40 s, hot needle technique. with the column held at 608C, then heated to 3008C at 68C miny1 . The carrier gas was hydrogen Ž1.5 ml miny1 .. The injector and detector were main-

J.M. Moreda et al. r The Science of the Total En¨ ironment 220 (1998) 33]43

36

tained at 300 and 3308C, respectively. Aliphatic hydrocarbons and PAHs resolved peaks of the chromatographic sample were quantified by reference to the response factor of the standards. PAHs were identified by gas chromatography]mass spectroscopy ŽGC-MS. in the Electron Impact spectra ŽEI. mode, with a HewlettPackard Model 5890 instrument coupled with a HP mass selective detector model 5971, in the scan mode. The electron energy was set at 70 eV. The temperature in the transfer line was 3008C and 3108C in the analyzer. Data were acquired by scanning from 30 to 400 mass units at 1.5 scan sy1 . Helium was used as the carrier gas with a flow-rate of 1.5 ml miny1 and the other chromatographic conditions were the same as described above. 3. Results and discussion Organic extracts were analyzed for 64 pollutants. The results are shown in Table 1 Žaliphatic hydrocarbons. and Table 2 ŽPAHs.. 3.1. Aliphatic hydrocarbons For a typical profile of these sludges, the aliphatic hydrocarbons identified and quantified are shown in Fig. 1. The chromatograms obtained for these pollutants are very similar, but quantitatively a change in the concentration levels exist; for example, the aliphatic hydrocarbons are between 227 and 1421 mg kgy1 DM ŽFig. 2.. In this case, a relation of carbon predominance as the ICP total Žindex of carbon predominance. has been proposed: ICPtotal s

SC 2 nq1 SC 2 n

for n s 7 y 20

The values obtained for this index indicates the source of the aliphatic hydrocarbons, thus, the bacterial activity that permits the degradation of aliphatic hydrocarbons in the same way that hydrocarbons which have a petroleum source, show ICPs near to unity ŽJhonson and Calder, 1973; Grimalt et al., 1985, 1988.. When the index of carbon predominance is calculated, we observe

Table 1 Concentration of aliphatic hydrocarbons found in the sludges Žmg kgy1 . Compound

n-C14 n-C15 n-C16 n-C17 Pristane n-C18 Phytane n-C19 n-C20 n-C21 n-C22 n-C23 n-C24 n-C25 n-C26 n-C27 n-C28 n-C29 n-C30 n-C31 n-C32 n-C33 n-C34 n-C35 n-C36 Total UCM

Mean Žmg kgy1 . 153 52.4 53.4 56.2 32.0 48.8 25.5 44.1 36.5 29.0 24.3 22.9 19.2 17.4 12.9 12.2 8.49 21.6 8.08 16.2 6.81 6.28 4.02 4.14 2.57 719 3693

Range

40.5]387 23.3]120 21.6]114 20.6]120 11.9]64.1 17.8]100 8.50]45.7 12.1]90.7 10.9]63.2 9.23]56.2 6.31]50.6 7.22]52.0 5.13]48.3 5.61]32.5 4.01]28.8 3.53]22.3 2.41]14.8 5.13]38.1 1.76]12.1 3.53]24.5 1.28]11.0 1.28]9.40 0.80]6.51 0.64]7.62 0.48]3.90 227]1421 844]6599

S.D.

113 35.0 35.8 32.1 16.2 26.9 12.1 23.5 15.4 12.6 11.9 12.4 12.1 7.57 6.88 5.81 3.97 11.2 3.70 7.39 3.39 2.97 1.82 2.12 1.19 361 2149

Detection limits 0.03 mg kgy1

levels close to one ŽFig. 3.. All the chromatograms show a UCM Žunresolved complex mixture. which is typical of spills with petroliferous derivatives ŽFarrington and Quinn, 1973; Farrington et al., 1977., with levels up to 6599 mg kgy1 as dry matter ŽDM.. These levels are very similar or higher than those found in marine sediments by different studies such as the one of Havana Bay, Cuba Ž1500]7500 mg kgy1 dry sediment. ŽRamos et al., 1989. and Southampton Ž350 mg kgy1 dry sediment. ŽGiger et al., 1980. which correspond to zones where petroliferous refineries occur. The UCM is more important in several sludge samples as observed in Fig. 3, where the ratio UCMrn-alkanes are shown. The higher val-

J.M. Moreda et al. r The Science of the Total En¨ ironment 220 (1998) 33]43

37

Table 2 Concentration of PAHs found in the sludges Žmg kgy1 . Compound

C1 -naphthalene C2 -naphthalene Dibenzofuran C3 -naphthalene Fluorene C1 -dibenzofuran C4 -naphthalene C1 -fluorene C2 -dibenzofuran Dibenzothiophene Phenanthrene Anthracene C1 -dibenzothiophene C1 -phenanthrene C2 -dibenzothiophene 2-phenylnaphthalene Ethylphenanthrene C2 -phenanthrene Fluoranthene C3 -dibenzothiophene Pyrene Benzow b xnaphthow2,3-d xfuran C3 -phenanthrene Benzow axfluorene Benzow b xfluorene Ethylmethyl-4H-cyclopentaw d,e,f x phenanthrene C2-fluoranthenerC2 -pyrene Benzow c xphenanthrene Benzow b xnaphthow1,2-d xthiophene Benzow axanthracene Chrysene q triphenylene Benzow axcarbazole C1-benzow axanthracenerC 1-chrysene Inedew1,2,3-c,d xpyrene Benzow g,h,i xperylene Coronene Dibenzofluoranthene Total PAHs UCM

Mean Žmg kgy1 .

Range

S.D.

15.5 41.2 2.88 51.3 7.48 12.3 7.67 16.8 10.2 2.99 7.20 1.15 7.24 22.2 3.28 2.94 4.06 11.2 3.42 3.13 2.83 1.70 5.34 2.56 0.87 0.93

1.98]27.2 12.0]80.0 1.27]4.89 25.2]104 3.78]16.7 6.03]24.6 3.33]16.9 8.44]31.2 5.00]17.7 1.39]5.42 3.23]16.0 0.46]2.92 2.95]13.1 9.28]48.0 1.49]5.29 1.32]5.06 1.58]6.27 4.18]21.0 1.09]6.00 1.15]5.06 1.03]4.63 0.57]2.30 1.83]8.47 0.29]7.05 0.23]1.54 0.34]1.61

9.59 24.8 1.40 27.6 4.14 6.35 4.44 7.91 4.87 1.48 3.73 0.72 3.42 12.2 1.16 1.00 1.71 5.30 1.39 1.15 1.19 0.54 2.28 2.47 0.47 0.40

0.56 0.54 0.48 0.40 0.99 1.13 0.97 1.79 0.71 0.49 0.92

0.11]1.11 0.11]0.92 0.17]0.92 0.11]0.66 0.23]1.38 0.29]1.81 0.23]1.35 0.11]6.74 0.06]1.61 0.06]0.99 0.11]1.80

0.30 0.25 0.20 0.19 0.33 0.45 0.33 2.11 0.57 0.28 0.55

257 1079

128]482 334]1685

123 379

Detection limits 0.03 mg kgy1

ues for the ratio correspond to samples which were affected by the impact of petroliferous derivatives. The evolution of the ratio UCMrnalkanes is very similar to the ICP. As well as the linear aliphatic hydrocarbons, two isoprenoid hy-

drocarbons have also been found as minor constituents: pristane and phytane, which show levels and an evolution very similar to their homologous n-C 17 and n-C 18 ŽFig. 4.. Natural input may be recognized from the pres-

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J.M. Moreda et al. r The Science of the Total En¨ ironment 220 (1998) 33]43

Fig. 3. ICP total and UCMrn-alkanes ratios. Fig. 1. Spectra of aliphatic hydrocarbons ŽSeptember 1993..

ence of pristane. However, since this hydrocarbon is also present in petroleum it can only be considered as a positive indicator of organisms such as zooplankton when the pristanerphytane ratio is higher than one. The low ratio is consistent with the predominance of petroleum inputs ŽGomez-Belinchon ´ et al., 1991.. In our study, the pristanerphytane ratio is near to unity. All these features are attributed to petroleum input ŽTissot and Welte, 1984.. The lighter n-alkanes constitute the group of compounds which are present in the greatest concentrations. As their molecular weight increases, their concentration decreases ŽFig. 1.. The alkane n-C 14 is found as a major constituent with a concentration of between 40.5 mg kgy1 and 387 mg kgy1 . The compounds n-C 29 and n-C 31 stand out among the heavier alkanes. This feature is

Fig. 2. Total concentrations for each identified compound group.

typical of hydrocarbons with a natural source, i.e. from terrestrial plants ŽEglinton and Hamilton, 1967.. Taking into account the results obtained by other authors ŽBlumer and Snyder, 1965; Farrington and Quinn, 1973; Jhonson and Calder, 1973; Giger and Blumer, 1974; Farrington et al., 1977; Giger et al., 1980; Grimalt et al., 1985, 1988; Ramos et al., 1989. and the studied features: chromatographic profile ICPs, isoprenoids, UCM and hydrocarbons levels, the petroleum or its derived products is the main source of these hydrocarbons. 3.2. PAHs In the third fraction, a total of 37 PAHs have been identified ŽTable 2.. The sample profiles are very similar, but quantitatively the differences are important. The presence of light PAHs and UCM is a feature of these samples. The methylated

Fig. 4. Concentrations for n-C 17 , n-C 18 , pristane and phytane.

J.M. Moreda et al. r The Science of the Total En¨ ironment 220 (1998) 33]43 Table 3 Ratios for several alkylated and non-alkylated PAHs Sample

1

2

3

4

September 1993 October 1993 November 1993 December 1993 January 1994 February 1994 March 1994 June 1994 July 1994

6.92 5.72 5.14 6.95 4.73 6.58 4.28 4.81 3.98

2.83 2.39 2.74 2.34 2.23 2.77 1.98 1.87 1.76

7.83 8.17 7.65 6.62 6.71 7.63 8.53 8.83 8.82

7.20 3.51 3.68 5.24 4.54 4.90 5.75 3.98 4.90

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with the ones obtained by other authors ŽGiger et al., 1980; Hites et al., 1980; Grimer et al., 1985; Ramos et al., 1989., for different products that origin PAHs, as Kuwait crude, Qatar crude, liquid pitch, gasoline combustion, coal combustion, lubricant oil and similar to those that have been obtained from petroliferous derivatives have been found. Although the PAHs with a petroliferous source are the majority, there are also other compounds whose source has been attributed, principally, to pyrolitic processes, such as chrysene, triphenylene, benzow axfluorene, benzow b x fluorene, indenew1,2,3-c,d xpyrene, benzow g,h,i x perylene, dibenzofluoranthenes and coronene. For example, the benzow g,h,i xperylene and coronene are typical of carburant combustions, which enter into the sewerage through stormwater run off from highways and streets. The levels found for the sewage sludges are summarized in Table 2. The mean total PAHs concentration for the nine sludges was 257 " 123 mg kgy1 , although these concentrations varied between 128 and 482 mg kgy1 ŽDM.. The alkylnaphthalenes are the most abundant, although the C 3-naphthalene was, on average, the most abundant individual polyaromatic hydrocarbon, ranging between 25.2 and 104 mg kgy1 ŽDM.. The PAHs concentrations obtained in this study are similar to those found in other sewage sludges ŽTable 4. ŽWild et al., 1990; Wild and Jones, 1992.. These authors have studied sewage sludges with an urban contribution as the main source and for which the com-

1, methylphenanthrenesrphenanthrene; 2, methylfluoranthenesrfluoranthene; 3, methyldibenzofuransrdibenzofuran; and 4, methyldibenzothiophenesrdibenzothiophene.

hydrocarbons have been found as the major group of compounds present in the samples. Among the light hydrocarbons, the methylated compounds are the most important. Thus, the alkylphenanthrenes, the alkylfluoranthenes, the alkyldibenzofurans and the alkyldibenzothiophenes constitute four groups of compounds in which the alkylated homologues were predominant compared with the non-alkylated species ŽTable 3. which is a typical feature of petroliferous derivatives ŽYoungblood and Blumer, 1975; Borwitzky and Sghomburg, 1979; Hites et al., 1980; Grimer et al., 1981, 1983; Prhal et al., 1984.. Moreover, other compound ratios, such as methylphenanthrenerphenanthrene, phenanthreneranthracene, fluorantener pyrene and benzow a xanthracenerchrysene q triphenylene have been calculated and compared

Table 4 Concentrations of PAHs Žmg kgy1 .: sludge samples ŽA and B. from the United Kingdom ŽWild et al., 1990; Wild and Jones, 1992. and sludge sample ŽC. from the Arazuri sewage plant Compound

Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benzow g,h,i xperylene Coronene

A

B

C

Mean Žmg kgy1 .

S.D.

Mean Žmg kgy1 .

S.D.

Mean Žmg kgy1 .

S.D.

0.5 4.7 0.6 8.1 6.8 10.5 ]

0.2 1.4 0.4 5.8 4.2 6.0 ]

2.40 3.00 0.33 1.50 2.00 2.50 0.64

0.03 0.08 0.00 0.14 0.15 0.08 0.09

7.10 7.20 1.15 3.42 2.83 0.71 0.49

4.65 3.70 0.72 1.39 1.19 0.57 0.28

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J.M. Moreda et al. r The Science of the Total En¨ ironment 220 (1998) 33]43

pounds with a major molecular weight are more abundant, whereas in our study, in which the industrial contribution is very important, the major contribution originated from the light PAHs. A pathway for the elimination of these sludges is by application to agricultural land, but one which increases the PAHs content of agricultural soils. There are possible loss mechanisms of PAHs in the soil, such as volatilization, abiotic degradation, biodegradation, transboundary transfer and via crops ŽWild and Jones, 1992a.. What could generate potential problems via human food-chain contamination; therefore, it is necessary to know the levels of these contaminants when applied as a fertilizer. Today, there are several countries which have control guidelines for organic soil contaminants, such as the Dutch Soil Protection Guideline ŽVegter, 1993., which has been followed by other countries. In this guideline, levels for a clean soil ŽTarget values. and a Intervention values have been marked. These last show values of 10 mg kgy1 for the benzow axpyrene, 50 mg kgy1 for naphthalene and indenew1,2,3y c,d xpyrene, 100 mg kgy1 for phenanthrene, anthracene, fluoranthene and benzow g,h,i xperylene. Considering that the sludges are diluted 50 times when they are added to the agricultural soil, the pollutant concentration of these sludges is low, even under the Target values. 3.3. Factor analysis More detailed information about similaritiesrdifferences among contaminants were obtained when factor analysis was applied; SPSS Windows Žversion 6.0.1. was used for this study. The individual normality of each variable has been checked using the Kolmogorov]Smirnov test. Factor analysis was performed by evaluation of principal components and computing the eigenvalues. The rotation of principal components was carried out by the Varimax method ŽHopke, 1983.. Those eigenvalues, higher than unity, were considered and four factors were obtained, which explain a large amount of the total variance Ž86.9%. of the variables used in the analysis. In

Fig. 5. Illustration with the most rotated factor loads for the PAHs.

general, the aliphatic hydrocarbons and PAHs showed a strong association with factor one Ž46.0% of variance., except the PAHs with a high molecular weight that did not have a significant loading in this factor. The first factor is likely associated with a petrogenic input ŽFig. 5.. The main loading compounds of the second and third factor in these sludges are also related with petroleum products. The second factor Ž20.1% of variance., was composed with the light aliphatic hydrocarbons Ž n-C 14 to n-C 24 , pristane and phytane. and this factor decreases when the molecular weight increases. The third factor Ž14.2% of variance. was composed mainly of the aliphatic hydrocarbons with a major molecular weight Ž n-C 25 to n-C 36 . and this factor increases with the molecular weight. Aliphatic hydrocarbons are separated into two groups ŽFig. 6.. Factors two and three are directly related to the molecular weight of aliphatic hydrocarbons or other physico-chemical properties related to molecular weight such as vapor pressure or degradation. The two groups of hydrocarbons can be differentiated by their vapor pressure, which dominates in the first group, associated with factor two. Even in the case where both groups enter into the sewerage systems in association with the same spillages, their residence times will be different which will be reflected in different concentration trends that are detected by factor analysis. The contributions by different factors of aliphatic hydrocarbons Žfactor two and three. and by the PAHs Žfactor one. show that they have different spillages. These last PAHs, such

J.M. Moreda et al. r The Science of the Total En¨ ironment 220 (1998) 33]43

Fig. 6. Aliphatic hydrocarbons with the most important rotated factor loads.

as chrysene, triphenylene, benzow a xfluorene, benzow b xfluorene, indenew1,2,3-c,d xpyrene, benzo w g,h,i xperylene and coronene, are associated with other factors which have an important contribution in factor four Ž6.70% of variance.. Principally, these compounds have their origin in combustions of petroleum derivates, coal and wood, hence factor four can be associated with pyrolitic contributions, probably arising from urban traffic. 3.4. Conclusions The results mainly show a variation in aliphatic hydrocarbons and PAH concentrations throughout the year, i.e. these temporal variances are quantitative, while the profiles of pollutants have the same morphology throughout the year. The urban and industrial sources are the main origins of these pollutants. The aliphatic hydrocarbons are more abundant than the PAHs. The higher concentrations were found for the n-C 14 Ž387 mg kgy1 . in November 1993. The higher concentrations were found taking into account all hydrocarbons; the total aliphatic hydrocarbons show the highest concentrations in the month of December, 1420 mg kgy1 ŽDM., while in June it was 482 mg kgy1 ŽDM. for the total. Some can be deleted by evaporation or degradation processes. The lighter PAHs are the most abundant, principally the methylated PAHs. Total PAHs are highest in the month of June, 482 mg kgy1 ŽDM., while in July it was 128 mg kgy1 ŽDM. for the total. The origin of aliphatic hydrocarbons and PAHs is principally of petroliferous derivatives, but it

41

seems that it comes from different industrial wastes. PAHs are other compounds with an pyrolitic origin, but their presence in the sludge is very low if it is compared with the other petrogenic hydrocarbons. The concentration levels of the PAHs found in these sludges Ž128]482 mg of PAHs kgy1 . and their dilution Ž50 to 10 times. when they are applied to agricultural lands, enable their use as fertilizer ŽStark and Hall, 1992.. The contaminant levels of the studied sludges are smaller than the proposed EPA ŽEnvironmental Protection Agency, 1989; WPCF, 1989. and Dutch guidelines ŽVegter, 1993..

Acknowledgements

Financial support for this work from Departamento de Educacion, ´ Universidades e Investigacion ´ of Gobierno Vasco ŽProject PI92r4. and Departamento de Agricultura y Pesca of Gobierno Vasco ŽProject IDT-3r93., is gratefully acknowledged. The author thanks A. Gonzalez ´ for text revision, to L. Canton ´ and Departamento de ŽUPVrEHU. Farmacia y tecnologıa ´ Farmaceutica ´ for technical support and to the Arazuri Waste Water Treatment Plant ŽPamplona, Spain. for sludges received.

References

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