JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH
Part A—Toxic/Hazardous Substances & Environmental Engineering
Vol. A39, Nos. 11–12, pp. 2799–2815, 2004
The Concentration of Mild-Extracted Polycyclic
Aromatic Hydrocarbons in Sewage Sludges
Patryk Oleszczuk* and Stanisbaw Baran
Institute of Soil Science and Environmental Management,
Agriculture University, Poland
ABSTRACT
The present study evaluates the content of the mild-solvent extracted fraction of
the polycyclic aromatic hydrocarbons. Ten compounds from the US EPA list
(phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chryzene,
benzo[b]fluoranthene, benzo[a]pyrene, benzo[ghi]perylene oraz indeno[1,2,3-
cd]pyrene) were chosen. The compounds were extracted with n-butanol from
11 sewage sludges that differed both in the total PAH content and in their
physicochemical properties. On the basis of the results obtained, the influence of
the properties of the PAH and some properties of selected sludge on the content
of the mild-solvent extracted fractions of these compounds was determined.
The content of the fraction extracted with n-butanol within the total of 10 PAHs
ranged from 12.5 to 83.2% (mean 40.1%) depending on the type of sludge.
Similarly, as in the case of the total of the 10 PAHs, significant differences in the
content of PAHs extracted with n-butanol were also noted for the individual
compounds studied. In the case of most individual PAHs their mean share did
not differ statistically in relation to the PAH type and was close to 40%.
An evaluation of the relation between the share of the fraction extracted with
n-butanol from the different types of sludge and the properties of the PAHs
showed that statistically, there existed significant (P< 0.05) correlations between
log Koc (in the case of one sewage sludge) and between the nitrogen content,
*Correspondence: Patryk Oleszczuk, Institute of Soil Science and Environmental
Management, University of Agriculture, Lublin, Poland; E-mail: [email protected].
2799
DOI: 10.1081/LESA-200033835 1093-4529 (Print); 1532-4117 (Online)
Copyright & 2004 by Marcel Dekker, Inc. www.dekker.com
ORDER REPRINTS
the ratio of C/N, cations Mg2þ and Kþ (in the case of a few PAHs). A clear and
significant relation was found between the content of and the share of the fraction
of n-butanol extracted and the PAH fraction present in the sewage sludge pore
water (determined on the basis of an equilibrium partition model).
Key Words: Polycyclic aromatic hydrocarbons; Sewage sludges; Organic
contaminants; Bioavailability; Mild extraction.
INTRODUCTION
Polyaromatic hydrocarbons (PAHs) are listed as priority pollutants by the USEPA.[1] Some are toxic, mutagenic, and carcinogenic to humans[2] and are known topersist in the environment. The presence of PAH’s can be found in numerouselements within the natural environment (water, soil, sediments),[3–5] however, ithas been evaluated[6] that the main PAHs sink is the soil. One source of PAHs’ insoil is sewage sludge[7,8] resulting from a considerable PAH content in this typeof waste.[9–13]
As has been shown,[14] directly after sewage sludge has been introduced into thesoil, in the case of some PAHs there are quite significant disproportions between thecontent of these compounds forecast (as calculated theoretically) and their actualcontent as determined in soil fertilized with sewage sludge. Losses can be explainedby the biodegradation phenomenon, leaching, evaporation, and photodegradation.Evaluation of the bioavailable PAH fraction in sewage sludge could then be the basisfor the evaluation of the potential possibility of their quick degradation in the initialperiod after their introduction. In the literature, there are descriptions of the variousmethods used for the determination of the bioavailable fraction of polycyclicaromatic hydrocarbons. In order to evaluate the content of the bioavailableforms, the following methods have been proposed: supercritical-fluid extraction(SFE),[15–17] the application of passive samplers (tenax, semi-permeable membranedevices, octadecyl-modified silica disks),[18–22] persulphate oxidation,[23] the multi-column system,[24] the nonexhaustive cyclodextrin-based extraction technique[25] andselective chemical extractants.[22,26–28] Researchers from Cornell University[26,28]
using the mild-solvent extraction procedure with n-butanol achieved very goodresults in the prediction of the bioavailable PAH fraction in the soils.
In the studies presented, the content of mild-solvent extracted PAHs wasevaluated in sewage sludge. Evaluated were the extent of the influences of theamount of organic matter on the PAH fraction extracted with this method, theextent of the influence of the properties of the other types of sludge (pH, cationexchange capacity, the total of the exchangeable bases, the degree of the basesaturation, the total amount of nitrogen, ratio TOC/Nt, available forms of P and K,cations—Ca2þ, Mg2þ, Kþ, Naþ) and the properties of the PAHs themselves(molecular weight, solubility in water, log Koc, log Kow, Henry’s constant, molecularconnectivity index, and molecular surface area) on the scope of this process.The results obtained are the basis for further studies on the evaluation of the contentof the bioavailable PAH fraction in the various types of sewage sludge as well as inthose soils fertilized with sewage sludge and compost.
2800 Oleszczuk and Baran
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MATERIALS AND METHODS
Polycyclic Aromatic Hydrocarbons Analysis
The total content of PAHs was determined by a method described in more detailin Refs.[5,29,30] Sewage sludge samples (3 g) were extracted with dichloromethane(2� 40mL) in an ultrasonic bath (Sonic-3, Polsonic, Poland); the extract was thencentrifuged and purified by the solid phase extraction method in octadecyl C18
microcolumns (JT Baker-Mallinckrodt, Germany). A Spherisorb-PAH (SchambeckSFD GmbH, Germany) was used for PAH separation. The mobile phase(acetonitrile:water, 82:18, v/v) flow was set to 1mL/min. Detection was carriedout at 254 nm. The column was installed in a thermostated oven at 31�C (LCO 101,ECOM, Czech Republic). Recoveries for the total procedures (sample preparation,extraction, and SPE) ranged between 72 and 83% for individual PAHs.
Mild-solvent extraction was carried out by the extraction of samples of sewagesludge (10 g) with 30mL n-butanol; after which, the extracts were centrifuged andthe PAH content was determined in the residue after extraction in accordance withthe methodology described above. The differences between the total PAH content(as determined in the dichloromethane) and the residue (after extraction withn-butanol) was determined as an n-butanol fraction.
All reported concentrations of PAHs (total and n-butanol fractions) areexpressed on a dry-weight basis of sewage sludge (determined by drying thesewage sludge for 24 h at 105�C) and are the average of triplicate extractions.
Evaluation of PAH Concentrations in Sewage Sludge Water Phase
In the literature[31,32] the bioavailable fraction is often defined as the pollutantspresent mainly in the pore water. The concentration of investigated PAHs in thesewage sludge pore water phase was evaluated on the basis of an equilibriumpartition model[31,33]:
PAHwp ¼ PAHtot=ðKoc � focÞ ð1Þ
wherePAHwp—concentration of PAHs in the sewage sludge water phase (mg/L);PAHtot—concentration of PAHs in the sewage sludge (mg/kg);foc—fraction of sewage sludge organic carbon (kg/kg);Koc—water–carbon partition coefficient (L/kg).
Properties of Sewage Sludges
The physical–chemical properties of the soils studied were determined bymethods generally used in chemical-soil laboratories. pH was measured potention-metrically in 1M KCl after 24 h in the liquid/soil ratio of 10, the total of theexchangeable bases (TEB) and cation exchange capacity (CEC) were measured in
Concentration of Mild-Extracted Polycyclic Aromatic Hydrocarbons 2801
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the 0.1N HCl extraction[34] with calculating the degree of the base saturation (BS).The total amount of nitrogen (Nt) was determined by the Kjeldahl method[35]
without the application of Dewarda’s alloy (Cu–Al–Zn alloy-reducer of nitrites andnitrates), and it constituted the sum of organic and ammonium nitrogen. Availablepotassium and phosphorus forms were determined by the method of Egner et al.[36]
Cations (Ca2þ, Mg2þ, Naþ, and Kþ) were determined by Pallman methods in 1NNH4Cl.
[37]
Statistical Evaluation
The relationships between n-butanol fraction of polycyclic aromatic hydro-carbons and properties of sewage sludges (Table 1) and PAHs (Table 2) weredetermined by correlation analysis with Statistica 5.0. Significance was set at�p< 0.05. Statistically significant differences between the results were evaluated onthe basis of standard deviation determinations and analysis of variance method(ANOVA). Data with normal distribution were analyzed by the t-test forindependent samples (P< 0.05).
RESULTS AND DISCUSSION
The Total Content of PAHs
The total content of polycyclic aromatic hydrocarbons in the sewage sludgestudied varied greatly. The total content of the 10 PAHs ranged from 3012.0 to27954.8 mg/kg d.m. (Fig. 1). In the sewage sludges studied, fluoranthene and
Table 1. The physicochemical properties of sewage sludges used in the experiment.
Sewage
sludge pH TOC Nt Ca2þ Mg2þ Kþ Naþ CEC TEB BS P K
B-40 12.4 169.8 22.4 530.8 183.4 22.9 65.6 803 820 97.9 4.6 0.8
W-100 6.4 227.0 23.0 329.4 200.3 31.3 22.2 583 608 96.0 35.4 3.2
K-100 5.8 228.6 40.6 675.5 410.8 64.2 45.5 1196 1222 97.9 28.0 8.4
L-110 6.5 220.8 44.8 701.9 445.8 67.9 57.4 1273 1295 98.3 25.1 3.0
T-140 5.6 207.0 40.6 530.9 699.4 61.5 40.7 1333 1363 97.8 35.7 3.5
D-170 6.6 240.6 28.0 839.8 130.9 17.5 17.6 1006 1020 98.6 18.2 3.2
P-180 6.9 230.4 35.0 541.3 594.5 47.9 35.6 1219 1234 98.8 22.1 2.2
J-190 6.6 177.0 39.2 241.5 174.7 49.8 24.9 491 513 95.7 18.2 3.2
R-200 7.2 253.2 36.4 411.4 200.9 66.5 45.7 725 746 97.2 24.1 2.5
S-230 5.6 222.6 28.0 1057.0 297.1 18.8 34.3 1407 1425 98.7 12.3 1.2
R-250 6.9 184.2 19.7 295.7 804.4 89.0 34.5 1223 1241 98.6 25.8 5.6
pH-in KCl; TOC—total organic carbon content (g/kg); Nt—the total amount of nitrogen
(g/kg); CEC—cation exchange capacity (mmol/kg), TAB—the total of the exchangeable bases
(mmol/kg), BS—the degree of the base saturation (%); P and K—available forms of
phosphorous and potassium (mg/kg); cations—Mg2þ, Ca2þ, Naþ, Kþ (mmol/kg).
2802 Oleszczuk and Baran
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benzo[b]fluoranthene predominated, and in few cases, significant amounts of pyrene
and benzo[a]anthracene (>14%) were observed. Taking into consideration the PAH
content related to the number of rings, the widest group were 4-rings compounds
where the content in the different types of sewage sludges studied exceeded 50%.
Some authors attempt to identify the source of PAH in order to determine PAH the
origin based on the presence of individual compounds from this group or
Table 2. The physicochemical properties of PAHs.a
PAHs MW S logKow
log Koc
Hs1� MSAmin max mean
Phen 178 1.1 4.57 4.10 6.70 5.40 3.24 4.815 198.0
Ant 178 0.05 4.54 4.20 6.90 5.55 3.96 4.809 202.2
Fluo 202 0.13 5.22 4.60 6.70 5.65 0.92 1.220 218.6
Pyr 202 0.26 5.18 4.60 6.80 5.70 1.04 5.559 213.5
BaA 228 0.002 5.61 4.50 6.70 5.60 0.58 6.226 —
Ch 228 0.011 5.91 4.90 7.80 6.35 0.065 6.226 240.2
BbF 252 0.0038 6.60 5.70 7.50 6.60 — 6.976 —
BaP 252 0.0008 6.04 6.30 8.50 7.40 0.046 6.976 225.6
BghiP 276 0.0006 7.10 6.20 9.20 7.70 0.075 7.720 266.9
Ind 276 0.062 7.10 6.60 9.20 7.90 — 7.720 —
aData from Refs. [14,21,60–63]
MW—molecular weight; S—water solubility; log Kow—octanol water partitioning coefficient;
log Koc—organic carbon–water partitioning coefficient, Hs—Henry constant; 1�—molecular
connectivity index; MSA—molecular surface area.
B-40 W -100 K-100 L-110 T-140 D-170 P-180 J-190 R-200 S-230 R-250
Sewage sludges
0
4000
8000
12000
16000
20000
24000
28000
32000
PA
H c
onte
nt [µ
g/kg
]
Total PAHs contentMild-extracted solvent PAHs content
Figure 1. The mild-extracted solvent and total PAHs content in investigated sewage sludges.
Concentration of Mild-Extracted Polycyclic Aromatic Hydrocarbons 2803
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determining relations between the individual PAHs. The above method is usedmainly for soils[38] and sediments.[4,39,40] In the case of sewage sludge, the mostrepresentative seems to be the method proposed by Budzinski et al.[39] Further to thismethod, it is assumed that the value of the coefficient phenantrene/anthracene (Fen/Ant)>10 indicates that the source of the origin of PAHs are the processes to whichcrude oil is subjected, whereas the value of the phenantrene/anthracene coefficientlower than 10, points to the predominance of pyrolytic processes. In the case of thefluoranthene/pyrene coefficient, it is assumed that values higher than 1 are related topyrolytic processes, mainly coal burning.
The values of coefficients: phenantrene/anthracene and fluoranthene/pyrene inthe sewage sludge samples studied showed that the main share of PAHs in mostsewage sludge samples was related to pyrolytic processes. Only in the case of onesewage sludge sample (R-250) was the value of the fluoranthene/pyrene coefficientabove 1. At the same time, the highest value of the phenanthrene/anthracenecoefficient was found in this sample. On the basis of the above data, it can beassumed that discharges from the fuel industry could have contributed to thepollution of sewage sludge with PAHs. It would also confirm the high contributionof benzo[ghi]perylene when compared to other sludges studied as suggested byPerez et al.[11]
Potentially Bioavailable Content of PAHs
As can be seen in the data presented in Fig. 1, only in the case of one sludge(W-100) were the differences between the total PAH content and the content ofPAHs extracted with n-butanol found to be insignificant. In much of the sewagesludge, these differences were markedly higher and for more than half of the sewagesludge studied they exceeded 50%. Figure 2 presents the contribution of then-butanol fraction in the total PAH content in relation to the number of rings.The contribution of 4 and 5-rings PAHs extracted with n-butanol in relation to thetotal content of the compounds studied was characterized by a low relativelystandard deviation (RSD), i.e., 36.9 and 38.0%, respectively, whereas for theremaining PAHs groups (3 and 6-rings) the RSD values exceeded 50%.
Figure 3 presents the mean and the maximum contribution of the n-butanolfraction of the individual PAHs noted in the total content of these compounds. Inthe case of most PAHs, their mean share did not differ significantly, statisticallyspeaking, from the PAH type and was often close to 40%. Only in the case of thepyrene, did the mean share of the n-butanol fraction exhibit a clearly higher valuethan that of the remaining compounds at a level of about 55%. The lowest meanvalue was noted for chrysene (>30%) (Table 3).
On the other hand, the statistical analysis carried out did not show any clearinfluence of the properties of PAH and the properties of the various types of sludgeon the share of the fraction of the n-butanol extracted. Statistically significantrelations (P� 0.05) were only obtained between the nitrogen content and the share ofthe n-butanol fraction of benzo[b]fluorantene (�0.662), 5-rings PAHs (�0.696), andthe sum of the 10 compounds determined (�0.608). However, correlationsconcerning the same groups but characterized by a reverse direction of the influence
2804 Oleszczuk and Baran
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were also found for the C/N ratio (0.633; 0.725; 0.632). The remaining statisticallysignificant relations observed concerned Ca2þ cations (anthracene �0.608; fluor-anthene �0.687; indeno[1,2,3-cd]pyrene �0.611) and Kþ (benzo[a]anthracene�0.622; the total of the 10 PAHs�0.607 and 4-rings PAHs�0.699). As observedwith the Nt, they took on negative values.
Phen Ant Fluo Pyr BaA Ch BbF BaP BghiP Ind
PAHs
0
10
20
30
40
50
60
70
80
90
100
Con
trib
utio
n [%
]
Mean contribution of n-butanol fractionMaximum contribution of n-butanol fraction
Figure 3. Mean and maximum contribution of individual PAHs extracted by n-butanol.
Figure 2. Contribution of PAHs extracted by n-butanol in relation to number of rings.
Concentration of Mild-Extracted Polycyclic Aromatic Hydrocarbons 2805
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Table
3.
Totalandn-butanolextracted
contentofindividualPAHsin
investigatedsewagesludges.
PAHscontent(mg/kg)
Sew
agesludges
Phen
Ant
Fluo
Pyr
BaA
Ch
BbF
BaP
BghiP
Ind
B-40
Total
548�10
153�13
1470�10
1058�14
818�8
282�8
725�12
430�12
83�9
188�11
n-But
309�12
127�10
589�11
696�10
508�12
50�10
488�11
272�9
30�9
114�12
W-100
Total
648�8
546�7
478�16
223�15
45�24
479�31
241�11
594�5
545�5
632�4
n-But
576�13
522�15
311�13
223�10
345�12
409�9
134�11
445�11
486�9
575�10
K-100
Total
1144�12
333�7
3602�8
2070�11
1621�10
1046�13
3639�9
1602�9
668�11
1045�12
n-But
656�11
139�9
2617�9
1�14
416�12
156�9
659�10
1073�10
163�12
688�10
L-110
Total
253�9
80�11
1240�8
n.d.
560�12
553�12
392�9
247�11
109�9
177�13
n-But
26�10
14�12
342�10
n.d.
246�13
184�12
5�10
137�12
11�10
113�13
T-140
Total
245�8
46�6
678�11
574�13
176�14
120�8
628�12
297�9
99�10
150�11
n-But
33�12
5�9
18�9
482�13
74�12
41�9
183�11
6�11
10�12
24�9
D-170
Total
405�9
147�11
2315�8
2169�12
1078�13
917�11
2529�12
437�10
169�9
305�13
n-But
113�8
n.d.
793�10
1042�9
282�10
500�13
1625�8
n.d.
n.d.
59�9
P-180
Total
764�10
239�12
3469�11
2752�9
1420�8
847�13
3019�10
661�12
473�11
331�11
n-But
n.d.
12�11
951�9
1824�13
n.d.
n.d.
1517�10
279�10
373�12
120�12
J-190
Total
1149�9
318�12
5400�11
5051�9
2579�8
1869�12
7573�10
1786�9
835�13
1396�10
n-But
544�11
113�12
2457�10
2520�12
1024�9
n.d.
2729�12
798�10
n.d.
628�12
R-200
Total
1052�9
426�14
2827�8
n.d.
613�11
414�9
3512�9
370�13
261�10
316�14
n-But
811�9
277�13
1278�10
n.d.
n.d.
7�12
2524�8
257�13
198�11
262�13
S-230
Total
432�9
284�13
2271�13
1253�10
1493�8
866�10
2480�12
655�12
484�10
414�10
n-But
280�12
203�11
1539�14
663�11
1172�8
568�9
1663�12
384�14
223�9
225�11
R-250
Total
725�13
101�10
409�9
1904�11
802�12
760�14
289�10
376�13
61�9
139�11
n-But
322�11
111�12
416�11
840�9
36�9
113�12
122�12
189�11
16�10
n.d.
Total—
PAHsextracted
bydichloromethane;
n-But—
PAHsextracted
n-butanol;Phen—
phenantherene;
Ant—
anthracene;
Fluo—
fluoranthene;
Pyr—
pyrene,
BaA—
benzo[a]anthracene;
Ch—
chryzene;
BbF—
benzo[b]fluoranthene;
BaP—
benzo[a]pyrene,
BghiP—
benzo[ghi]perylene;
Ind—
indeno[1,2,3-cd]pyrene;�—
relativestandard
deviation(n¼3,%
).
2806 Oleszczuk and Baran
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It is difficult to relate the results obtained to the data presented by other authors.
The existing information concerns mainly those soils polluted with PAHs.[41–48] The
studies carried out so far show that the soil’s properties—such as the content of
organic matter,[41,43,45] the nanoporosity and hydrophobicity of the matrix,[49] as well
as the cation exchange capacity (CEC),[45]—play an important role in the
bioavailability of pollutants for the soil’s microorganisms and invertebrates.
Chung and Alexander[45] obtained a clear relationship between the content of
organic matter and the percentages of phenanthrene not extracted by n-butanol from
the soil. Nam et al.[41] found also that the amount of the phenanthrene fraction
extracted with n-butanol increased markedly with the decrease in the content of
organic carbon in the soil. The above observation points to the important role of the
organic fraction both in sequestering and in the bioavailability of phenanthrene. In
the present study, no significant statistic relations between TOC and n-butanol
fraction were noted, however there was a significant statistical relationship (0.603;
P� 0.05) between benzo[a]pyrene and the residue after the extraction of n-butanol.
It is surprising that in the present study, the share of n-butanol fraction in the various
types of sludge with a relatively low content of organic matter (J-190, R-250)
(Table 1), and in the case of most PAHs—as well as their sum total—was markedly
lower than in sludge with about a 20% higher content of organic carbon (W-100,
R-200, S-230) (Table 1). The above points to the existence of factors other than
organic matter, which determine the content of the bioavailable PAH fraction.
Significant correlations between the residue after the extraction of n-butanol and
CEC, TEB, and BS were also found in the case of chrysene (�0.651;�0.645;�0.803;
P� 0.05, respectively). A similarly high correlation but with a positive value,
however, was also observed by Chung and Alexander[45] in the case of phenanthrene.
Moreover, these last authors showed also that there exist high relations between the
content of TOC and CEC. In the present study, no such relation was noted which
could explain the opposite of the relation between CEC and PAHs as observed in the
studies by Chung and Alexander.[45]
The lack of relations between the content of the n-butanol PAH fraction and the
sewage sludge properties, even though it was noted in the case of the soils, could be
related to the properties of the sewage sludge matrix. Sewage sludge is characterized
by the clearly higher values of almost all the physico–chemical properties studied
(in some cases they were even several times higher); hence their influence on the PAH
desorption processes could be different than for soils. Other pollutant levels some
several degrees higher, both with respect to their amounts and diversification, were
found in the sludge. Some of them (for example surfactants), frequently noted in the
various types of sewage sludge,[50,51] can significantly increase the bioavailability and
desorption of the PAHs.[52,53]
Studies carried out by some other authors on PAH bioavailability and
sequestration showed that such factors as the concentration of contaminants,[42]
the wetting and drying of the soil,[47,48] soil moisture,[54] slurring,[52] the presence of
other PAHs[44,52] and the length of time that the soil and the pollutant are in
contact,[55] can also influence the scope of the above process along with the
properties of the soil mentioned above. All the factors enumerated above can also
influence the process of the bioavailability of pollutants in sewage sludge. A precise
Concentration of Mild-Extracted Polycyclic Aromatic Hydrocarbons 2807
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determination of the influence of the factors enumerated requires model studies to be
initially conducted on the technological line of the sewage treatment plant.Relations between the percentage content of the bioavailability of the PAH
fraction (in n-butanol) and the residue after the extraction of n-butanol were
evaluated with the following PAH properties (Table 2): Henry’s constant (Hs) related
to volatilisation ability,[56] water solubility (S) related to bio-availability,[57] the
octanol–water partition coefficient (logKow), the organic carbon–water partition
coefficient (log Koc), the first-order molecular connectivity index (1�) and the
molecular surface area (MSA) related to soil sorption affinity.[58–60] In the case of
one sludge only (S-230) was any statistically significant relation noted between the
share of the n-butanol fraction and log Koc (�0.674). These results suggest that
the properties tested were poorly correlated with the n-butanol fraction of PAHs.
It could be suspected that in the above process, the properties may be more
descriptive of bioavailability. Similar relationships between the PAH properties
studied and PAH bioavailability and sequestration were observed by Kottler and
Alexander.[61]
The content of the PAH fraction present in the sewage sludge pore water
(calculated according to Eq. (1) ranged from 0.00081 to 0.00385% for the sum of the
compounds studied. Much lower values were noted for individual PAHs (Table 4).
Interesting results were obtained during the evaluation of the relationships between
the content of PAHs extracted with n-butanol (Table 3) and content of PAHs
evaluated in pore water of sewage sludge. High and significant relationships were
observed both in the case of the content and percentage PAH share of the forms
selected (Fig. 4). In the case of the sum of the compounds studied, their respective
values were: 0.859 and 0.881 for the content and percentage share. In the case of
some individual PAH forms, high and statistically significant differences were also
noted. Only chrysene and benzo[ghi]perylene (for the content) and pyrene (for the
percentage share) were the exceptions in this case, no statistically significant relations
being noticed for them. The results obtained showed that the n-butanol fraction is
connected to a high degree with the PAH content determined in the sewage sludge
pore water. In order to discover the mechanisms responsible for the phenomena
observed, it is necessary to carry out additional studies, however, the information
presented above clearly shows that the PAH content in the sewage sludge pore water
can, indirectly, have a significant influence on the sequestration and bioavailability
of the pollutants.When analyzing the relations between the PAH content in sewage sludge pore
water and water solubility (S), it was found that in 5 types of sludge (K-100, D-170,
J-190, R-200, R-250) this property was significantly (>0.694, P� 0.05) statistically
correlated with the PAH fraction share potentially present in sewage sludge pore
water. Among the sludge types enumerated, two (J-190 and R-250) drew the
attention of the researchers earlier since despite the low content of organic matter,
they were characterized by the low content of the n-butanol fraction. The above
observation could mean that water solubility in the case of these sludge types
(decreased by the low content of the factors increasing solubility) limited the
bioavailability of the pollutants in them more than did the content of the organic
carbon.
2808 Oleszczuk and Baran
ORDER REPRINTS
Table
4.
TheconcentrationofPAHsin
sewagesludgepore
watercalculatedonthebasisofanequilibrium
partitionmodel
(1).
PAHsa
B-40
W-100
K-100
L-110
T-140
D-170
P-180
J-190
R-200
S-230
R-250
Phen
0.012838
0.011364
0.019920
0.004569
0.004715
0.006702
0.013192
0.025849
0.016543
0.007730
0.015670
Ant
0.002541
0.006779
0.004101
0.001025
0.000621
0.001724
0.002920
0.005057
0.004736
0.003595
0.001614
Fluo
0.019382
0.004714
0.035274
0.012568
0.007329
0.021538
0.033706
0.068299
0.024997
0.022836
0.004971
Pyr
0.012426
0.001960
0.018070
0.000000
0.005535
0.017986
0.023829
0.056932
0.000000
0.011230
0.020622
BaA
0.012104
0.004980
0.017812
0.006366
0.002132
0.011253
0.015480
0.036604
0.006084
0.016841
0.010929
Ch
0.000741
0.000943
0.002044
0.001119
0.000258
0.001702
0.001641
0.004717
0.000731
0.001737
0.001842
BbF
0.001072
0.000267
0.003998
0.000446
0.000762
0.002640
0.003291
0.010746
0.003484
0.002798
0.000393
BaP
0.000101
0.000104
0.000279
0.000045
0.000057
0.000072
0.000114
0.000402
0.000058
0.000117
0.000081
BghiP
0.000010
0.000048
0.000058
0.000010
0.000010
0.000014
0.000041
0.000094
0.000021
0.000043
0.000007
Ind
0.000014
0.000035
0.000058
0.000010
0.000009
0.000016
0.000018
0.000099
0.000016
0.000023
0.000010
PAHssum
0.061228
0.031194
0.101614
0.026158
0.021429
0.063648
0.094233
0.208798
0.056670
0.066952
0.056140
aDescriptionofPAHsin
Table
3.
Concentration of Mild-Extracted Polycyclic Aromatic Hydrocarbons 2809
ORDER REPRINTS
CONCLUSION
The issue presented in this study is relatively poorly described in the literature onthe subject, and the explanation of the relationships observed requires a series ofexaminations. The results obtained showed that the contribution of the PAHsfraction extracted with n-butanol in the total PAH content varies widely.The contribution of the n-butanol extracted fraction ranging from 0 to 100%could prove that the scope of degradation of the pollutants described in the soils
0 2000 4000 6000 8000 10000 12000
Content of PAHs in n-butanol fraction [µg/kg]
0
0.05
0.1
0.15
0.2
0.25
Con
tent
of P
AH
s in
sew
age
slud
ge p
ore
wat
er [µ
g/L]
0 20 40 60 80
Contribution of PAHs in n-butanol fraction [%]
0
0.001
0.002
0.003
0.004
0.005
Con
trib
utio
n of
PA
Hs
in s
ewag
esl
udge
por
e w
ater
[%]
A
B
Figure 4. Correlation between n-butanol extracted PAHs and PAHs in sewage sludge-pore
water. A—content [mg/kg]; B—contribution [%].
2810 Oleszczuk and Baran
ORDER REPRINTS
fertilized with sludge can vary considerably. The high discrepancies in the content of
the n-butanol fraction as well as the unclear relations between this fraction and PAH
properties and the properties of the various types of sewage sludge studied showed
that the amount of this fraction (as well as its scope) depend on other factors which
need further studies for clarification. The PAH content in sewage sludge pore water
in which a significant relation to the n-butanol fraction has been established could
be used as an example here.At the present stage of research, it is also important to determine to what degree
the bioavailability established on the basis of the above described examinations also
holds true for the bioavailability of these pollutants after fertilization of the soil
with sewage sludge.
ACKNOWLEDGMENTS
Financial support from the State Committee for Scientific Research (MNiI,
Warsaw). Project no. KBN 3 P06S 042 25 is gratefully acknowledged. P. Oleszczuk
is granted by the Foundation for Polish Science
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