SAMPLING AND ANALYSIS OF POLYCYCLIC AROMATIC HYDROCARBONS IN URBAN AND RURAL ATMOSPHERES: SPATIAL AND GEOGRAPHICAL VARIATIONS OF CONCENTRATIONS

Atmospheric sampling (gas and particles) of PAHs (naphthalene, acenaphthene, fluorene, anthracene, phenanthrene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[ghi]perylene, dibenz[a,h]anthracene, indeno[1,2,3-cd]pyrene, coronene) on XAD-2 resin (20 g) and glass fiber filters respectively, were performed in 2002 by using Digitel DA80 high-volume samplers equipped with a PM10 head. Samplings were performed in Strasbourg (east of France) and its vicinity (Schiltigheim and Erstein). Sites were chosen to be representative of urban (Strasbourg), suburban (Schiltigheim), and rural (Erstein) conditions. Field campaigns were undertaken simultaneously in urban, and suburban, urban and rural sites during spring and autumn during 4 h at a flow rate of 60 m³/h^?1 which gives a total of 240 m³ · h^?1 of air per sample. The period of sampling varied between 06:00 to 10:00, 11:00 to 15:00, 17:00 to 21:00 in order to evaluate a variation of concentration during automobile traffic between urban, suburban, and rural areas. Gas and particle samples were separately Soxhlet extracted for 12 h with a mixture of CH₂Cl₂/n-hexane (50:50 v/v), concentrated to about 1 mL with a rotary evaporator and finally dried under nitrogen. Dry extracts were dissolved in 1 mL of CH₃CN before analysis. Before use, traps were Soxhlet cleaned for 24 h with the same mixture as used for the extraction. Analysis of each extract was performed by reverse phase HPLC, and fluorescence detection and quantification was done with respect to triphenylene used as internal standard. Results shows that automobile traffic seems to be the main source of PAHs in urban areas whatever the period (autumn and spring) while in autumn other sources, especially coming from combustion, influence the atmospheric contamination by PAHs.     

POLYCYCLIC AROMATIC HYDROCARBONS ANALYZED IN RAINWATER COLLECTED ON TWO SITES IN EAST OF FRANCE (STRASBOURG AND ERSTEIN)

Polycyclic Aromatic Hydrocarbons (naphtalene, acenaphtene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[j]fluoranthene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylène, indeno[1,2,3-c,d]pyrene and coronene) have been consecutively analyzed in rainwater sampled in Strasbourg (urban site) and Erstein (rural site) between January 2002 and June 2003 and between April 2002 and June 2003 on a weekly basis respectively. For the sampling of rainwater, a wet-only rainwater sampler was used together with an open collector to take the measurements of precipitation.

PAHs in rainwater were extracted by using SPE cartridges and analyzed by HPLC-fluorescence following a method developed in the laboratory.

Mean concentrations of all PAHs (Σ 16 HAPs) varied between 0.15 and 79.60 ng·L^?1 in Erstein, and between 3.70 and 1596.45 ng·L^?1 in Strasbourg. Naphtalene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[j]fluoranthne and benzo[a]pyrene were the most concentrated PAHs analyzed. Benzo[a]pyrene was frequently detected. Seasonal effects were observed with a maximum of concentrations of PAHs during cold periods. Some spatial influences were also reported. The calculation of some PAH ratios show that diesel exhaust could be the main source of PAHs in rainwater on the two sites.     

Major gaseous and PAH emissions from a fluidized-bed combustor firing rice husk with high combustion efficiency

This experimental work investigated major gaseous (CO and NO_x) and PAH emissions from a 400 kW_th fluidized-bed combustor with a cone-shaped bed (referred to as ‘conical FBC’) firing rice husk with high, over 99%, combustion efficiency. Experimental tests were carried out at the fuel feed rate of 80 kg/h for different values of excess air (EA). As revealed by the experimental results, EA had substantial effects on the axial CO and NO_x concentration profiles and corresponding emissions from the combustor. The concentration (mg/kg-ash) and specific emission (μg/kW h) of twelve polycyclic aromatic hydrocarbons (PAHs), acenaphthylene, fluorene, phenanthrene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene and indeno[1,2,3-cd]pyrene, were quantified in this work for different size fractions of ash emitted from the conical FBC firing rice husk at EA = 20.9%. The total PAHs emission was found to be predominant for the coarsest ash particles, due to the effects of a highly developed internal surface in a particle volume. The highest emission was shown by acenaphthylene, 4.1 μg/kW h, when the total yield of PAHs via fly ash was about 10 μg/kW h.     

The Supercritical Fluid Extraction of Anthracene and Pyrene from a Model Soil: An Equilibrium Study

Abstract

Supercritical carbon dioxide (SC-CO₂) is used to extract two polycyclic aromatic hydrocarbons (PAHs), anthracene and pyrene, from a model soil at conditions ranging from 35 to 55 [ddot]C and 7.79 to 24.13 MPa. Equilibrium partition coefficients and Freundlich isotherm constants are determined for the two PAHs on white quartz sand and the model soil. The effect on equilibrium of additional water in the soil phase is also examined.     

Determination of Carcinogenic Polycyclic Aromatic Hydrocarbons (PAHs), Aflatoxins,and Nitrosamines in Processed Fish from the Winam Gulf Area of Kenya and Estimated Potential Exposure in Human

PAHs, aflatoxins and nitrosamines were analyzed in fish samples obtained from various markets and locations within the Winam Gulf area and processed by various methods often used in Kenya. The mean concentrations of total PAHs (TPAHs) in the smoked, charcoal-grilled and fresh tilapia muscle samples ranged from 22.27–44.58, 20.36–28.51, and 11.43–16.53 μg/kg wet weight, respectively. The concentrations of individual PAHs decreased in the order smoked>charcoal-grilled>fresh fish. Of the USEPA 16 PAHs, benzo(a)pyrene, dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene, and benzo(g,h,i)perylene were not detected in all samples analyzed. Fluoranthene, acenaphthene, anthracene, phenanthrene, and acenaphthylene were not detected in fresh tilapia muscles but were generated in significant amounts on the samples during smoking and charcoal-grilling. The risk of exposure to human was estimated to be 0.67 μg/day through consumption of tilapia. The TPAHs levels in fresh fish, smoked and grilled tilapia were higher than the maximum allowable concentrations as per the WHO standards. Aflatoxins were found to be generated in sun-dried Dagaa during handling and storage with total mean concentrations ranging from 0.33–1.58 μg/kg wet weight but none were detected in the fresh samples. The daily intake of aflatoxins through consumption of Dagaa was estimated to be 0.0079 μg/day during the rainy season when the drying process is less efficient. None of the nitrosamines were detected in both fresh and the deep-fried tilapia muscle samples (frying temperatures ranging from 110–170°C) after exposure to nitrites and nitrates in water, in concentrations ranging up to 10 μg/L (NO₂^?) and up to 160 μg/L (NO₃^?).     

Synthesis of FeBr3-cyclodextrin complexes in non-aqueous solution

Mixing FeBr₃ either solid or dissolved in ethyl ether, in acetonitrile or in dichloromethane with solid β-cyclodextrin, form different type of FeBr₃-cyclodextrin complexes as indicated by their stoichiometric composition and thermal and spectroscopic properties. The complexes are stable under usual atmospheric conditions. Water solutions of FeBr₃ at pH 12 containing cyclodextrin are stable over 24 h. The solid complexes were characterized by DSC and TGA analysis as well as by IR spectroscopy. It is shown that the complexes obtained from the reaction of solid cyclodextrin with FeBr₃ dissolved in ethyl ether, acetonitrile, or dichloromethane catalyze the oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide although in different yields. The best complex for this purpose is the one prepared in CH₂Cl₂ which afforded the sulfoxide in good yield.     

Desorption kinetics of polycyclic aromatic hydrocarbons in soil using lab-scale rotary desorber

Thermal desorption of fluorene, anthracene, pyrene, and benzo(a)pyrene in soil contaminated with PAHs was performed using a rotary desorber at temperatures of 300–500 °C, and the dependency of the PAH removal efficiency on the percentage water content, residence time, and thermal desorption temperature was investigated. The removal efficiencies were inversely proportional to the boiling points of PAHs, and the removal efficiencies decreased with decreasing residence time and heating temperature. The reaction rate constant and activation energies (E _A ) were estimated to determine the thermal desorption properties of each substance, and the activation energies were found to be 29.50–34.48 kJ mol^?1. Freeman-Carroll’s law was applied along with the Arrhenius equation to extract the thermal desorption properties from the data obtained in this experiment.     

Indoor Polycyclic Aromatic Hydrocarbon Concentration in Central India

The indoor burning of different materials like fuels, incense, mosquito coil, candles etc. results in generation of polycyclic aromatic hydrocarbons (PAHs) in an uncontrolled manner. The PAH, i.e., Benzo(a)pyrene (BaP) is considered as most toxic or carcinogenic and the toxicity of other PAHs is related to this compound. Therefore, the concentration and emission fluxes of polycyclic aromatic hydrocarbons (PAHs) emitted during burning of commonly used indoor materials, i.e., 15 fuels (i.e., biomass (BM), coal (C), cow dung (CD), kerosene (K)), 4 incense (IS) and mosquito coil (MC) in Raipur district, Chhattisgarh, central India is described. The samples were taken in September 2013 in indoor environments and respective smoke emitted were collected using high volume United State of America (USA) air sampler on quartz fiber filters. The concentration of total 13 PAHs (∑PAH₁₃) (i.e., phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)-pyrene, dibenz(ah)anthracene, benzo(ghi) perylene, indeno1,2,3-(cd)pyrene, and coronene) in particulate matter (PM₁₀) in the indoor air during burning of the fuels, IS and MC materials ranged from 367–92052 ng m^?3, 4089–14047 ng m^?3, and 66–103 ng m^?3 with mean values of 7767 ± 11809 ng m^?3, 9977 ± 4137 ng m^?3, and 74 ± 20 ng m^?3, respectively. The mean concentration of the ∑PAH₁₃ present in indoor environment is much higher than the WHO limit value of 1.0 ng m^?3. The sources and toxicities of PAHs are discussed.     

FORMATION OF SULFATE CONJUGATES METABOLITES IN THE DEGRADATION OF PHENANTHRENE,ANTHRACENE, PYRENE AND BENZO[A]PYRENE BY THE ASCOMYCETE ASPERGILLUS TERREUS

Abstract

The metabolism of four PAHs (phenanthrene, anthracene, pyrene and benzo(a)pyrene) by an Aspergillus terreus strain, isolated from a polluted soil, was investigated in liquid submerged culture. The main metabolites identified by the HPLC-MS technique, after solvent extraction of the fermentation broth and mycelium, were aryl-sulfates and hydroxyl-aryl-sulfates. A metabolic pathway was identified involving in sequence: the hydroxylation by a monooxygenase of the PAHs, the conjugation with a sulfate ion, followed by a further hydroxylation to hydroxyl-aryl-sulfates compounds. PAHs degradation by A. terreus yielded a different number of metabolite isomers depending on the type of the parent PAH. The environmental fate and ecotoxicity of the metabolite 9-phenanthrenesulfate was also investigated by a respirometric test of ready biodegradability and by a Vibrio fischeri acute toxicity test respectively. This compound was easily degradable by microbial consortia derived from polluted soil and capable of thriving on phenanthrene as its sole carbon source. Moreover the sulfate conjugate resulted in 2 orders of magnitude less toxic than its precursors phenanthrene.     

Levels and Origin of PAHs in Some Big Lakes

This study was designed to assess the contamination of a very special lake, Lake Baikal in Siberia, and two big lakes, Ladoga and Onega in the European part of Russia, by polycyclic aromatic hydrocarbons (PAHs). PAH compounds were analyzed by HPLC and the target PAH, benzo[ a ]pyrene (B a P), by using the spectral-luminescence (Shpol'skii) method. Elevated levels (to 96 w g kg m 1 ) of B a P in sediments of Lake Baikal reflected proximity to potential sources of emission, situated either on shore (a paper and pulp mill in Baikalsk) or upstream river systems. The concentration of B a P in sediments decreased with the distance from outlet and the depth. The sediment samples contained several representatives of PAHs. The total content of identified compounds reached 873 w g kg m 1 (less than four nuclear representatives not included). Dominating heavy PAHs were dibenz[ a,j ]anthracene, dibenz[ a,h ]anthracene, dibenzo[ a,e ]pyrene, and dibenzo[ a,l ]pyrene. The concentration of B a P in sediments of northeastern Baikal was more than two times less than that for the southern part of the lake and corresponds to the background level. The B a P levels estimated for sediments close to paper and pulp mills of the Lake Ladoga exceeded 160 w g kg m 1 , being two orders of magnitude higher than that for other areas of these lakes. The contamination of sediments of Lake Onega by PAHs is affected by pulp and paper mills as well as other sources. Our results clearly demonstrate the contribution of specific industrial sources like paper and pulp mills to the content of PAHs in the Baikal, Ladoga, and Onega water ecosystem.     

Analysis by GC-MS of Polycyclic Aromatic Hydrocarbons in a Cream Containing Coal Tar

Qualitative and quantitative PAHs composition of a cream containing coal tar (5%), used in cutaneous diseases treatment, was studied. Eleven PAHs were analysed in pure coal tar and in the cream by GC-MS, after ultrasonic extraction by pyridine. Ten PAHs were found in pure coal tar: naphthalene, biphenyl, acenaphthylene, fluorene, phenanthrene, anthracene, carbazole, fluoranthene, pyrene and benzo[a]pyrene. No traces of 2,3-benzofluorene were detected. Seven PAHs were identified in the cream: naphthalene, biphenyl, acenaphthylene, fluorene, phenanthrene, fluoranthene and pyrene. 2,3-benzofluorene was also absent in the cream. Anthracene, carbazole and benzo[a]pyrene (one of the most toxic) were present in coal tar and not detected in the cream.

The seven PAHs found in the cream and in coal tar were quantified. Hydrocarbons concentrations were between 0.107 ± 0.0038 mg.g^?1 (for biphenyl) and 0.734 ± 0.0438 mg.g^?1 (for phenanthrene) in the cream and between 4.31 ± 0.23 mg.g^?1 (for biphenyl) and 21.9 ± 0.57 mg.g^?1 (for fluorene) in coal tar.     

Polycyclic Aromatic Hydrocarbons Determination in Grilled Beef and Chicken

ABSTRACT

Polycyclic aromatic hydrocarbons (PAHs) are principally formed as a result of thermal treatment of food, especially grilling or barbecuing. In the present study, two types of Iranian popular grilled beef and chicken dishes (kebab) were analyzed for toxic PAHs, i.e., naphthalene, fluoranthene, phenanthtrene, anthracene, pyrene, and benzo(a)pyrene applying GC/MS. The differences in PAHs concentrations among grilled beef and chicken (kebab koobide and juje kebab) were found to be significant (p < 0.05), ranging from 0.29 to 21.95 ng·g^?1. Benzo(a)pyrene was found in nearly all samples; the maximum concentration of total PAHs was 21.95 ng·g^?1 found in grilled beef (koobide Khalij fars) and the lowest was 0.29 ng·g^?1 in grilled chicken (juje kebab) of Sahel restaurant.     

Photodegradation Products of Polycyclic Aromatic Hydrocarbons in Water and Their Amenability to Biodegradation

Saturated water solutions of anthracene, pyrene, benz[ a ]anthracene, and dibenz[ a,h ]anthracene were UV-irradiated in the presence of oxygen and their photodegradation products were identified. The products were then individually photolyzed. Several products of photolysis were identified chromatographically. Furthermore, the biodegradation of two photoproducts, 9,10-anthracenedione and benz[ a ]anthracene-7,12-dione, was studied separately and in the presence of the original polycyclic aromatic hydrocarbons (PAHs). The irradiation of anthracene first produced 9,10-anthracenedione and continuous illumination yielded additionally 1-hydroxy-9,10-anthracenedione, 1,4-dihydroxy-9,10-anthracenedione, 9-anthrone, and 1(3H)-isobenzofuranone. Photolysis of benz[ a ]anthracene produced benz[ a ]anthracene-7,12-dione and 1(3H)-isobenzofuranone. By irradiation of pyrene and dibenz[ a,h ]anthracene mainly diones of the original compounds were formed. In batch vial experiments, the biodegradation of 9,10-anthracenedione alone started with no lag phase whereas biodegradation of anthracene alone had a lag of 40 days. The lag for benz[ a ]anthracene biodegradation was, in the presence and absence of benz[ a ]anthracene-7,12-dione, 17 and 35 days, respectively.     

OPTIMIZATION OF LARGE VOLUME INJECTION FOR IMPROVED DETECTION OF POLYCYCLIC AROMATIC HYDROCARBONS (PAH) IN MUSSELS

Detection of PAH of six benzene rings is somewhat troublesome and lowering the limits of detection (LODs) for these compounds in food is necessary. For this purpose, we optimized a Programmable-Temperature-Vaporisation (PTV) injection with Large Volume Injection (LVI) with regard to the GC-MS detection of anthracene, benz[a]anthracene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and dibenzo[a,e]pyrene. The optimization of PTV-LVI for GC-MS analysis included the choice of liner, solvent venting, splitless time, split flow and initial inlet temperature for injection of 25 μ L standard solution and spiked mussel samples. Samples were extracted with Accelerated Solvent Extraction (ASE) followed by two semi-automatic clean-up steps; gel permeation chromatography (GPC) on S-X3 and solid phase extraction (SPE) on pre-packed silica columns, prior to gas chromatography-mass spectrometry (GC-MS) detection. In comparison to traditional splitless injection, LODs were lowered for eighteen PAHs by the use of PTV-LVI ranging from 0.05 μ g kg ^?1 to 1.0 μ g kg^?1 fresh weight. In particular, the LOD of dibenzo[a,e]pyrene was improved by a factor of ten when using the validated PTV-LVI method.     

Degradation of Pyrene Contaminated Soil with Spiked <Superscript>14</Superscript>C Pyrene by Hemoglobin Catalysis

Hemoglobin (Hb) is a member of the hemeprotein family that undergoes non-specific catalytic chain reactions in the presence of hydrogen peroxide (H₂O₂). The catalytic ability of Hb to degrade the carcinogenic polycyclic aromatic hydrocarbon pyrene was demonstrated using soil contaminated with ¹⁴C pyrene. Three bench-scale laboratory tests were performed using ¹⁴C pyrene in the presence of a buffer, H₂O₂, and a combination of Hb and H₂O₂. The initial pyrene concentration of the contaminated soil was set to 11 mg/kg, with 5,500,000 dpm of ¹⁴C pyrene. After a catalytic reaction for 24 h, the results showed that 17% of pyrene was degraded by H₂O₂, 38% of pyrene was degraded by Hb in combination with H₂O₂, and 0.13 and 1.2% of ¹⁴C pyrene were mineralized by H₂O₂ and Hb in combination with H₂O₂, respectively. An analysis of the products from the reaction involving Hb in combination with H₂O₂ revealed that 15.9% of the ¹⁴C intermediates in the acetonitrile fraction were polar products. After the catalytic reaction, 21 intermediate compounds were found via fraction analysis. The results suggested that Hb catalysis could be used to treat pyrene-contaminated soil as a novel catalytic technology for the remediation of hazardous materials in soil.     

Contamination of Soil by Polycyclic Aromatic Hydrocarbons in Some Urban Areas

The contamination by 16 polycyclic aromatic hydrocarbons (PAHs) in surface soils, sampled at a 0-5 cm depth in the urban areas of Tallinn, Helsinki, Vilnius, Chicago, London is reported. All samples were analyzed using the same protocol. The median concentrations ( w g/kg) were found to be 117, 539, 127, 3,263, 1,728 for pyrene; 62, 236, 43, 1,634, 1,652 for benzo[ a ]pyrene; 86, 304, 92, 2,295, 2,068 for benzo[ a ]pyrene toxic equivalents, calculated using the benzo[ a ]pyrene toxic equivalency factors; 467, 1,471, 392, 8,981, 6,837 for a total of seven probable human carcinogenic PAHs: benzo[ a ]anthracene, chrysene, benzo[ b ]fluoranthene, benzo[ k ]fluoranthene, benzo[ a ]pyrene, dibenz[ ah ]anthracene, indeno[1,2,3- cd ]pyrene; 911, 2,941, 672, 16,183, 13,718 for the total of 16 PAHs, recommended by the U.S. Environmental Protection Agency: naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[ a ]anthracene, chrysene, benzo[ b ]fluoranthene, benzo[ k ]fluoranthene, benzo[ a ]pyrene, dibenz[ ah ]anthracene, benzo[ ghi ]perylene, indeno[1,2,3- cd ]pyrene in Tallinn ( n = 3), Helsinki ( n = 3), Vilnius ( n = 15), Chicago ( n = 4), London ( n = 3), respectively. The size of the population is a statistically significant factor in urban soil contamination by high-molecular-mass PAHs.     

The electrochemical oxidation of dimethyl disulfide—Anodic methylsulfanylation of phenols and aromatic ethers

The electrochemical oxidation of dimethyl disulfide was investigated in acetonitrile and dichloromethane. The nature of the oxidation strongly depends on the nucleophilicity of the solvent. In acetonitrile a one-electron oxidation is observed and the consecutive species did not exhibit any reactivity towards aromatic compounds subject to electrophile substitution. On the contrary, the oxidation of dimethyl disulfide in methylene chloride afforded a two-electron process with the formation of a species consistent with CH₃S⁺. Its reactivity towards phenols and aromatic ethers was confirmed and showed a selective monomethylsulfanylation in most of the cases.     

DETERMINATION OF DIBENZO[A,L]PYRENE AND OTHER FJORD-REGION PAH ISOMERS WITH MW 302 IN ENVIRONMENTAL SAMPLES

Polycyclic aromatic hydrocarbons (PAHs) occur in the environment as complex mixtures including compounds with mutagenic and carcinogenic activity. The PAH profile routinely determined in environmental samples at present encompasses isomers with molecular weight (MW) not greater than 300. However, PAHs with MW >300 have been demonstrated for several matrices to contribute up to 50% of the total activity when tested for carcinogenicity in experimental animals. Recent studies indicate that among the dibenzopyrenes with MW 302 dibenzo[a,l]pyrene, possessing a fjord region, is by far the most carcinogenic PAH hitherto identified. To further elucidate the environmental relevance of this compound we have applied the isotope dilution GC/MS technique as analytical procedure to determine this compound and the related fjord region PAH naphtho[1,2-a]- and naphtho[1,2-e]pyrene in various matrices. Identification was based on comparison of UV and mass spectra as well as retention times of authentic reference materials. Determination of these PAHs was achieved after clean-up by several chromatographic steps including fractionation on a modified TABA-silica gel column. Quantitative data for matrices such as two cigarette smoke condensates, motor vehicle exhaust condensate (Otto-type engines), and tar-cork are reported. Based on toxic equivalent factors the relative contribution of dibenzo[a,l]pyrene (5.4–42.3%) to the total carcinogenic activity of a PAH profile will be discussed comprising 14 selected isomers (benzo[b]naphtho[2,1-d]thiophene; cyclopenta[cd]pyrene; benz[a]anthracene; chrysene/triphenylene; sum of benzo[b]-, benzo[k]-, and benzo[j]fluoranthene; benzo[a]pyrene; indeno[1,2,3-cd]pyrene; dibenz[a,h]anthracene; benzo[ghi]perylene; anthanthrene; dibenzo[a,l]pyrene determined in these matrices.     

Evaluation of drum bioreactor performance used for decontamination of soil polluted with polycyclic aromatic hydrocarbons

A laboratory‐scale drum bioreactor system was used to study engineering aspects of soil bioremediation. Polycyclic aromatic hydrocarbons (PAHs) were chosen as contaminants in soil. In the operation of the reactor, different mixing strategies were applied according to the size of soil without separate washing of sand. The effect of the water content of the soil mixture on solid mixing time and phenanthrene degradation rate was of particular interest. At 20% water content, which was below the saturation level, the mixing efficiency of soil and the degradation rate of phenanthrene was lower than those at 30% or 40% water content. Optimal water content was variable according to the soil texture. The drum bioreactor was operated under optimal water content and PAH concentration (fluorene, phenanthrene, anthracene, pyrene) and microbial numbers were measured in each soil phase (sediment and suspension). Over 95% of PAHs with three or four rings (fluorene, phenanthrene, anthracene, pyrene) were degraded at 270 mg kg⁻¹ soil within 20 days. The degradation rate of PAHs in the suspension phase was higher than that in sediment phase. © 1999 Society of Chemical Industry