Application of solid-phase extraction to determination of polycyclic aromatic hydrocarbons in sewage sludge extracts

Application of sulfur-coated magnetic carbon nanotubes for extraction of some polycyclic aromatic hydrocarbons from water resources

In the present work, novel sulfur-coated magnetic carbon nanotubes (MCNTs-S) material was fabricated by S coating on the MCNTs using a simple heating procedure. TGA, EDX, XRD, TEM, and VSM were employed to characterize the as-prepared composite. Using HPLC-UV system, the produced superparamagnetic sorbent was employed for the extraction and measurement of trace levels of five polycyclic aromatic hydrocarbons (PAHs) in environmental waters. The synergistic effect of the sulfur layer and CNTs substrate is primarily responsible for the remarkable extraction efficiency of the MCNTs-S sorbent towards PAHs. The experimental factors including MCNTs-S dosage, sorption time, elution solvent, ionic strength and solution pH were explored and optimized. Considering that the ionic strength and pH do not have any impact on the PAHs extraction, as a result, there is no need the unnecessary adjustment of the water samples. The linear dynamic ranges and detection limits under optimal conditions were in the range of 0.05-0.11 ng mL^-1 and 0.2-150 ng mL^-1, respectively. The analysis of PAHs in the real samples (sea water and river water) using this approach was successfully assessed with appropriate recovery values (94.6%-99.0%).

The Determination of Polycyclic Aromatic Hydrocarbons (PAHs) with HPLC-DAD-FLD and GC-MS Techniques in the Dissolved and Particulate Phase of Road-Tunnel Wash Water: A Case Study for Cross-Array Comparisons and Applications

Accelerated solvent extraction (ASE) and solid phase extraction (SPE) protocols tailored to either gas chromatography mass spectrometry (GC-MS) or high-performance liquid chromatography coupled to diode-array and fluorescence detection (HPLC-DAD-FLD) were developed for the determination of EPA 16 polycyclic aromatic hydrocarbons (PAHs) in the particulate and dissolved phase of road-tunnel wash water. An analytical approach was developed, assessed, and applied on environmental samples collected from five road tunnels in Norway. The absolute recoveries ranged from 57 to 104% for the particulates, and from 42 to 79% for the dissolved water phase. The target PAH compounds were separated in 34.75 min using the GC method and in 22.50 min by HPLC. In the particulate phases, higher molecular weight PAHs were detected in the range of 0.043 to 0.93 µg/g, and lower molecular weight PAHs were detected in the range of 0.020 to 1.0 µg/g, while the intermediate ones were present in the range of 0.075 to 2.0 µg/g. In contrast to the particulates, the dissolved phase mainly contained lower molecular weight PAHs in the range of 0.0098 to 0.50 µg/L. GC-MS demonstrated lower detection limits (LODs) than HPLC-DAD-FLD for 13 out of the 16 PAHs. A cross-array comparison of the two analytical techniques indicated that some target PAHs were detected solely or in higher concentrations with HPLC-DAD-FLD, indicating the occurrence of false positive peaks or/and co-eluting components. The resulting concentrations in the road tunnel wash water samples were used to calculate specific PAH forensic ratios to pinpoint the potential sources of PAH pollution. These ratios revealed that there are several potential sources for the origin of PAHs in tunnel wash water.

A sensitive microextraction by packed sorbent-gas chromatography-mass spectrometry method for the assessment of polycyclic aromatic hydrocarbons contamination in Antarctic surface snow

For the first time an eco-friendly method involving microextraction by packed sorbent (MEPS) coupled to gas chromatography-mass spectrometry (GC-MS) was developed for the determination of the 16 US-EPA priority pollutant polycyclic aromatic hydrocarbons (PAHs) as indicators of anthropogenic contamination in snow samples collected in polar regions. MEPS was carried out by using C8 sorbent material packed in a barrel insert and needle (BIN) and integrated in the eVol® semi-automatic device. For optimization purposes a Face Centred Design and the multicriteria method of the desirability functions were performed to investigate the effect of some parameters affecting the MEPS extraction efficiency, i.e. the number of loading cycles and the number of elution cycles. The developed MEPS-GC-MS method proved to be suitable for PAHs analysis at ultra-trace level by extracting small sample volumes achieving detection limits for 16 PAHs in the 0.3-5 ng L^-1 range, repeatability and intermediate precision below 11% and 15%, respectively, and good recovery rates in the 77.6 (±0.1)-120.8 (±0.1)% range for spiked blank snow samples. Enrichment factors in the 64 (±7)-129 (±18) range were calculated. Finally, the proposed method was successfully applied to the determination of PAHs in surface snow samples collected in 2020-2021 from four locations of Northern Victoria Land, Antarctica. Local emission sources such as ships and research stations were found to influence PAHs concentrations in the surface snow.

Solid phase extraction of 16 polycyclic aromatic hydrocarbons from environmental water samples by π-hole bonds

Through theoretical computation, it was demonstrated that perfluorobenzene can form π-hole⋅⋅⋅π bonds with polycyclic aromatic hydrocarbons (PAHs). Then, the π-hole bond was firstly introduced in solid phase extraction in which perfluorobenzene-bonded silica sorbent was synthesized and used for the solid phase extraction of sixteen PAHs in water. Compared with the traditional octadecyl silica sorbent, the perfluorobenzene-bonded silica sorbent showed higher adsorbabilities for the PAHs with 4-6 benzene rings, for which the recoveries increased by approximately 20%. Under the optimized conditions, the proposed SPE-HPLC-FLD/UV method was successfully applied for the analysis of 16 PAHs in river water and waste water samples with the limits of detection ranged from 0.002 to 0.08 μg⋅L^-1. In addition, when the perfluorobenzene-bonded silica sorbent compared with the phenyl-bonded silica sorbent, the results indicated that π-hole⋅⋅⋅π bonds between perfluorobenzene and PAHs were stronger than the π-π interactions between the PAHs and benzene in hexane solution, which highlights the remarkable potential for the application of the π-hole bond in the SPE field.

Concentrations, distributions, sources, and risk assessment of polycyclic aromatic hydrocarbons in topsoils around a petrochemical industrial area in Algiers (Algeria)

Fifty-five samples were collected from topsoils around a petrochemical industrial area at the east of Algiers (Algeria) and analyzed for 16EPA priority PAHs in the aim to determine the concentrations, the distributions, and the possible sources of polycyclic aromatic hydrocarbons (PAHs). The results of the quantification are then devoted to the assessment of the potential risks as the toxicity, the risk for the ecosystem, and the risk for the human health. The sampling sites were classified into four categories: rural, suburban, urban, and industrial-urban. A new extraction method based on the insertion of a preliminary step, using hot water, was proposed to improve the extraction efficiency. Principal component analysis (PCA) and selected diagnostic ratio of PAHs were used to investigate the source apportionment of these PAHs. The potential toxicity, the ecological, and human health risk of PAHs in soil were estimated using the toxic equivalent quotient, the risk quotient, and the total lifetime cancer risk (TLCR) methods, respectively. The proposed new protocol gave improved recovery rates for the sixteen EPA PAHs particularly for low molecular weight PAHs, with satisfactory repeatability (RSD < 10%). The Σ16PAHs concentrations were varied from 143.73 to 4575.65 μg kg^-1 with a mean value of 1209.56 μg kg^-1. Σ16PAH concentrations found for the industrial areas would be 2 times higher than for urban soils and 3 times higher than for the rural soils. The biplots of PCA and the five diagnostic ratios suggested that the most sources of PAHs in the rural, the suburban, and the urban areas are traffic emissions, biomass burning, and coal combustion sources. Some points of the urban-industrial area are from the petroleum source. The found Σ16PAH concentrations and theirs calculated TEQs showed the following trend: industrial-urban > urban > suburban >rural. The potential cancer of human health risks calculated through TLCR results indicated that the exposure to the 7EPA PAH-contaminated soils produces negligible cancer risk to human health.

Performance of metal-organic framework as an excellent sorbent for highly efficient and sensitive trace determination of anthracene in water and food samples

Polycyclic aromatic hydrocarbons are a class of highly toxic and unremitting organic pollutants that are widely distributed in the natural environment. In this work, a metal-organic framework (MOF) designated as HKUST-1 [Cu₃(BTC)₂] was synthesized, characterized, and applied as a solid-phase extraction sorbent for the determination of a trace polycyclic aromatic hydrocarbon, anthracene (Ant) as model compound, in various real samples by spectrofluorimetry. The synthesized MOF exhibited large surface areas and high extraction ability, making it excellent candidate as sorbent for enrichment of trace anthracene. The effects of influential parameters on the performance of the dispersive micro-solid-phase extraction (Dμ-SPE) process, such as the initial anthracene concentration, pH, sorbent dosage, and shaking time, were investigated and optimized by the experiment design method. Under the optimized experimental conditions, good linearity in the range of 3-85 ng mL^-1 with correlation coefficient 0.997 and good sensitivity with low detection limit 0.5 ng mL^-1 for Ant was achieved. The method has been validated in the analysis of real tap water, soft drink, and vegetable juice samples with recoveries in the range of 86.33-103.00% and relative standard deviations in the range of 1.94-3.77%. The as-prepared HKUST-1 was used for at least four times without any obvious decline of extraction capability. The results of this study show the great potential of MOFs as sorbents in Dμ-SPE procedures for the separation and determination of trace Ant in complicated matrices.

Effective solid phase extraction using centrifugation combined with a vacuum-based method for ambient gaseous PAHs

The developed SPE clean-up procedure provides much better efficiency for a group of low molecular weight PAHs than the conventional procedure. It is therefore appropriate for extraction of gaseous PAHs from ambient air samples.

Assessment of direct exposure and leaching risk from PAHs in roadway and stormwater system residuals

Wastes generated from municipal cleaning activities such as street sweeping, ditch cleaning, stormwater pond maintenance, and catch basin sediment removal require appropriate management. Beneficial use of these types of waste is a good alternative to landfilling; however, there are genuine concerns about possible soil and groundwater contamination by pollutants such as polycyclic aromatic hydrocarbons (PAHs). This study assessed the potential risks associated with beneficial use of roadway and stormwater system residuals collected from 14 cities across the state of Florida, USA. Total and leachable concentrations of 16 priority PAHs in the residual samples were measured and compared to appropriate risk-based regulatory threshold values. The bioaccessibility of the PAHs found in the waste streams was also determined using in vitro gastrointestinal leaching test. Of the PAHs studied, benzo [a] pyrene measured concentrations were above appropriate risk-based regulatory threshold values for soil and groundwater, while all other detected PAHs measured concentrations were below. Benzo [a] pyrene concentration (mg/kg) in street sweepings was 1.2 times higher than residential threshold values and 6 times lower than industrial threshold values. The in vitro study found PAH bioaccessibility to range from 1.7% to 49% in six roadway and stormwater system residual samples.

A nanocomposite consisting of silica-coated magnetite and phenyl-functionalized graphene oxide for extraction of polycyclic aromatic hydrocarbon from aqueous matrices

In this study, graphene oxide was covalently immobilized on silica-coated magnetite and then modified with 2-phenylethylamine to give a nanocomposite of type Fe₃O₄@SiO₂@GO-PEA that can be applied to the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples. The resulting microspheres (Fe₃O₄@SiO₂@GO-PEA) were characterized by Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), CHNS elemental analysis, and vibrating sample magnetometry (VSM) techniques. The adsorbent possesses the magnetic properties of Fe₃O₄ nanoparticles that allow them easily to be separated by an external magnetic field. They also have the high specific surface area of graphene oxide which improves adsorption capacity. Desorption conditions, extraction time, amount of adsorbent, salt concentration, and pH were investigated and optimized. Following desorption, the PAHs were quantified by gas chromatography with flame ionization detection (GC-FID). The limits of detection (at an S/N ratio of 3) were achieved from 0.005 to 0.1μg/L with regression coefficients (R²) higher than 0.9954. The relative standard deviations (RSDs) were below 5.8% (intraday) and 6.2% (inter-day), respectively. The method was successfully applied to the analysis of PAHs in environmental water samples where it showed recoveries in the range between 71.7% and 106.7% (with RSDs of 1.6% to 8.4%, for n=3). The results indicated that the Fe₃O₄@SiO₂@GO-PEA microspheres had a great promise to extraction of PAHs from different water samples.

Biochar production increases the polycyclic aromatic hydrocarbon content in surrounding soils and potential cancer risk

The objectives of the study were the identification of the source of contamination of soils and estimation of the potential cancer risk that may be caused by contact with soils situated in the vicinity of biochar production sites. Samples of soils collected in the immediate vicinity of traditional biochar-producing plants, located within the area of the Bieszczady National Park (Poland), were analysed for the content of polycyclic aromatic hydrocarbons (PAHs). The sum of the content of 16 PAHs varied within the range of 1.80-101.3 μg/g, exceeding the norms permitted in many European countries. The calculated coefficients on the basis of which one can determine the origin of PAHs (molecular diagnostic ratios) demonstrated that the potential source of PAHs in the soils may be processes related with the production of biochar. Estimation on the basis of the results of incremental lifetime cancer risks (ILCRs) within the range of 2.33 · 10(-4)-1.05 · 10(-1) indicated that the soils studied may constitute a significant cancer risk for persons who have contact with them. The values of ILCRS should be considered as at least high, which permits the conclusion that sites of that type may create a hazard to human health.

Determination of Polycyclic Aromatic Hydrocarbons in Wastewater by Single-Drop Microextraction Coupled to Capillary Gas Chromatography

This study describes an analytical method employing capillary gas chromatography (GC) using flame ionization detection (FID) that has been developed for the simultaneous determination of polycyclic aromatic hydrocarbons (PAHs) in wastewater, including naphthalene, 1-naphthol, 2-naphthol and anthracene. For this purpose, single-drop microextraction (SDME) was applied as a sample preparation technique. The SDME parameters such as types of extractants, volume of the microdroplet size, extraction time, stir rate and immersion depth of needle point were investigated and optimized. The method was linear in the ranges from 2.3 ×10-3to 70.0 μg·mL-1for naphthalene, 1-naphthol and anthracene, and 2.2 ×10-3to 50.0 μg·mL-1for 2-naphthol withR2≥ 0.9990. The SDME procedure allowed efficient recovery of the investigated PAHs ranging between 94 % and 104 % with a relative standard deviation (RSD) ≤4.2 for actual wastewater sampes spiked with 5, 10 and 20 μg·mL-1of PAHs, respectively. These results showed the potential of this technique for PAHs monitoring in wastewater samples. Furthermore, the investigated methods are simple, reliable, reproducible, and not expensive.

Influence of activated carbon and biochar on phytotoxicity of air-dried sewage sludges to Lepidium sativum

The goal of the research was to determine the phytotoxicity (using Lepidium sativum) of two activated carbon/biochar-amended sewage sludges. Apart from the impact of the AC/biochar dose, the influence of biochar particle diameter (<300, 300-500 and >500 μm) and the influence of the contact time (7, 60, 90 days) between AC/biochar and sewage sludges on their phytotoxicity was also assessed. No negative impact of sewage sludges on seed germination was observed (P>0.05). The application of AC or biochar to the sludges positively affected root growth by reducing the harmful effect by 7.8 to 42% depending on the material used. Furthermore, the reduction range clearly depended on the type of sewage sludge. No differences were observed in the inhibition of the toxic effect between both biochar types used and the biochar particle size. The extension of the contact time between AC/biochar and sewage sludges had a negative impact on root growth.

Optimization of a solid-phase extraction method using centrifugation for the determination of 16 polycyclic aromatic hydrocarbons in water

A fast and reliable method for the determination of polycyclic aromatic hydrocarbons (PAHs) in water samples by solid-phase extraction (SPE) using centrifugation has been developed and optimized. A silica-based C18 cartridge was used; parameters affecting the extraction procedure such as type and volume of the elution solvent, breakthrough volume of the percolated water sample, drying of the sorbent, and evaporation of the elute have been studied. The innovation of this work was the examination of the use of a centrifugation technique in both the drying and elution steps. When combined with centrifugation, the volume of the elution solvent was reduced to 1 mL and the time for sorbent drying decreased also to 10 min under vacuum. Under optimal conditions, recoveries for the 16 U.S. EPA PAHs were between 70 and 85% and the relative standard deviation varied between 1 and 14%. Surrogate standard recoveries were similarly between 61 and 94% with a relative standard deviation between 2 and 15%. The simplicity of the described method, use of less of organic solvent, short procedure time, and good recoveries demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples.

TiO2 nanotubes as solid-phase extraction adsorbent for the determination of polycyclic aromatic hydrocarbons in environmental water samples

An analytical method based on TiO2 nanotubes solid-phase extraction (SPE) combined with gas chromatography (GC) was established for the analysis of seven polycyclic aromatic hydrocarbons (PAHs): acenaphtylene, acenaphthene, anthracene, fluorene, phenanthrene, fluoranthene and pyrene. Factors affecting the extraction efficiency including the eluent type and its volume, adsorbent amount, sample volume, sample pH and sample flow rate were optimized. The characteristic data of analytical performance were determined to investigate the sensitivity and precision of the method. Under the optimized extraction conditions, the method showed good linearity in the range of 0.01-0.8 microg/mL, repeatability of the extraction (RSD were between 6.7% and 13.5%, n = 5) and satisfactory detection limits (0.017-0.059 ng/mL). The developed method was successfully applied to the analysis of surface water (tap, river and dam) samples. The recoveries of PAHs spiked in environmental water samples ranged from 90% to 100%. All the results indicated the potential application of titanate nanotubes as solid-phase extraction adsorbents to pre-treat water samples.

Occurrence and distribution of polycyclic aromatic carbons in sludges from wastewater treatment plants in Guangdong, China

In this study, the occurrence and distribution of polycyclic aromatic hydrocarbons (PAHs) were investigated in six sludge samples collected from Guangdong Province, China. Concentrations of PAHs varying from 2,534.1 to 6,926.6 microg kg(-1) (dry sludge) were observed in three municipal wastewater treatment plants with phenanthrene (Phe), fluoranthene, and pyrene being the main compounds. In addition, 682.6 microg kg(-1) PAHs were detected in one sludge sample from a food processing plant, with fluorene, Phe, and chrysene being the main components. No PAHs were detected in sludge samples obtained from two cosmetic plants. The levels and distributional characteristics of PAHs, polychlorinated biphenyls (PCBs), and polycyclic musks (PMs) from the samples were also compared. The results of this comparison indicated that petrochemical refineries and road traffic played important roles in the PAH loads in sludge, while PMs primarily originated from domestic wastewater and industrial wastewater from cosmetic plants. Finally, the presence of 98.8 microg kg(-1) PCBs in sludge suggested diffusional emission sources from electrical components containing PCBs.

Testing of different plants to determine influence of physico-chemical properties and contaminants content on municipal sewage sludges phytotoxicity

This study attempts to evaluate the Phytotoxkit as a tool for measuring the toxicity of municipal sewage sludges using 10 common plants: mustard, turnip, cress, red clover, cucumber, tomato, radish, sorrel, and spinach. The results were used to determine a germination index (GI) and a median effective concentration (EC) value for each plant. The trace metal and polycyclic aromatic hydrocarbon (PAH) contaminant content and the physical-chemical properties were examined. Most sewage sludges were characterized by an unfavorable electrical conductivity value of about 5.2 mS/cm(-1). The most abundant trace metals were zinc (Zn) at 871-1680 mg kg(-1), manganese (Mn) at 245-661 mg kg(-1), and copper (Cu) at 88.2-161.0 mg kg(-1). The lowest values were determined for cobalt (Co) at 2.9-3.8 mg kg(-1) and cadmium (Cd) at 0.7-3.7 mg kg(-1). The PAH sum was based on 10 individual compounds (USE EPA), and the PAH content ranged from 4.76 to 27.95 mg kg(-1), most of the sewage sludges showing a predomination by carcinogenic PAHs. The GI values, based on seed germination and root growth inhibition bioassays, showed increasing plant sensitivity to the tested sewage sludges in the following order: cress > turnip > mustard > sorrel > tomato > sorgo > red clover > radish > cucumber > spinach. The EC50 sewage sludge values lay in the range 31-404 g/kg of soil, and significant relationships were found for most of the plants between EC50 and the magnesium content (Mg(2+): alpha = 0.888-0.924, P = 0.05), calcium content (Ca(2+): alpha = 0.813-0.911, P < or = 0.05), and pH (alpha = -0.913-0.948, P = 0.05). In the case of sewage sludge pollutants, significant relationships were found for trace metals such as: strontium (Sr: alpha = 0.851-0.948, P < or = 0.05), chromium (Cr: alpha = 0.858, P < or = 0.05), and nickel (Ni: alpha = 0.955, P = 0.05), as well as pyrene (PAHs).

The Tenax fraction of PAHs relates to effects in sewage sludges

In the present study a toxicity evaluation (Heterocypris incongruens, OstracodToxKit FTM Test) was carried out for ten municipal sewage sludges in relation to polycyclic aromatic hydrocarbon (PAH) contents in these sludges. PAHs content in the sewage sludges was determined by a vigorous extraction method and solid phase extraction with Tenax-TA. The main aim of the evaluation was establishing whether it was possible to determine the negative influence of PAHs in the sewage sludges on H. incongruens mortality and growth inhibition using the Tenax-TA method. H. inconguens showed increased growth inhibition and mortality when exposed to all sewage sludges. Significant relationships were noted between the content of some Tenax-TA PAH fractions and the total organic carbon content, cation exchange capacity and concentration of Ca(2+) ions. The toxicity was proportional to Tenax-TA concentrations and was not governed by the total concentration found in the sewage sludge.

Changes of solid phase toxicity during sewage sludge composting in relation to bioavailability of polycyclic aromatic hydrocarbons

The aim of the present study was to determine the content of the bioaccessible fraction of polycyclic aromatic hydrocarbons (PAHs) in sewage sludges and composts by means of three techniques (solid phase extraction with Tenax-TA and non-exhaustive extraction with hydroxypropyl[beta]cyclodextrin and n-butanol) and at the same time to establish their influence on toxicity for Heterocypris incongruens (Ostracodtoxkit test) and Lepidium sativum (Phytotoxkit test). In the majority of cases sewage sludges negatively influenced on organisms. Generally, sewage sludge composting exerted a positive influence on phytotoxicity, whereas in the case of ecotoxicity a negative effect was noted. The content of the potentially bioaccessible PAHs fraction varied depending on the method applied. Composting usually lowered the content of the potentially bioaccessible fraction. Significant positive relationships were observed mainly between Tenax-TA extracted fraction of individual PAHs and growth inhibition of H. incongruens. Only negative correlations were noted in the case of phytotoxicity.

Sorption of phenanthrene by sewage sludge during composting in relation to potentially bioavailable contaminant content

The aim of the present study was to determine to what degree the sewage sludge sorption capacity to phenanthrene influences on bioavailability of this compound during composting. Sewage sludges were composted for 76 days. The content of the potentially bioavailable phenanthrene fraction was determined by: mild-solvent extraction with n-butanol (BTL) and non-exhaustive extraction technique with hydroxypropyl[beta] cyclodextrin (HPCD). Batch experiments were used to construct phenanthrene sorption isotherms. The contribution of the potentially bioavailable phenanthrene fraction in individual sewage sludges ranged from 32 to 48% (BTL) and from 5.1 to 80.3% (HPCD). The direction of changes in the potentially bioavailable fraction resulting from composting also depended on the sewage sludge and the extraction method applied. Isotherms demonstrated a good fit to the Freundlich isotherm model. Sorption coefficients (logK(F)) and organic carbon-normalized distribution coefficients (logK(oc)) of phenanthrene by sewage sludges ranged from 3.42 to 3.98 and from 4.14 to 4.70, respectively. Sewage sludges exhibited relatively strong affinity for sorption large amounts of phenanthrene. In the case of two sludges, a strong relationship between phenanthrene sorption capacity (logK(F) and logK(oc)) and the content of the bioavailable fraction of this compound was observed.

Application of three methods used for the evaluation of polycyclic aromatic hydrocarbons (PAHs) bioaccessibility for sewage sludge composting

Three chemical approaches were compared to assess the bioaccessibility of PAHs during four sewage sludge composting. In the present study solid phase extraction with Tenax-TA and two non-exhaustive/mild-solvent extraction techniques with n-butanol (BtOH) and hydroxypropyl[beta]cyclodextrin (HPCD) have been applied. The content of the PAHs sum in individual sludges ranged from 2.83 to 9.95 mg/kg. Mainly 4-ring PAHs predominated in all sludges. The content of the bioaccessible fraction of PAHs determined using the BtOH and HPCD methods was usually twice higher than with the use of Tenax-TA adsorbent. The share of the bioaccessible fraction depended on the method applied and sewage sludge type. In the case of the PAH sums it ranged from 28.1% to 54.5% (Tenax-TA), from 25.7% to 80.9% (BtOH) and from 60.2% to 83.5% (HPCD). As a result of composting, the share of the bioaccessible fraction decreased by about 50% in most of the sludges examined. The reliable prediction of individual PAHs losses was observed for many of the PAHs; however, for a number of them, this was confirmed in more than two of the sludges examined.

Forms of polycyclic aromatic hydrocarbon in the formation of sewage sludge toxicity to Heterocypris incongruens

The aim of the present study was to evaluate to what degree polycyclic aromatic hydrocarbon (PAH) determines sewage sludge toxicity in relation to Heterocypris incongruens. Six differing sewage sludges with increasing contents of polycyclic aromatic hydrocarbons were selected for the present study. As well as total PAH content, the content of the potentially bioavailable fraction was also determined in the sewage sludges using a method of mild-solvent extraction (with n-butanol). The PAH content was also calculated in the sewage sludge pore water by the equilibrium partitioning method. The total PAH content in the sewage sludges studied were in the range 3.60 to 27.95 mg kg(-1). The contribution of the n-butanol extracted fraction was in the range 38.7 to 75.4%. In the group of individual PAHs, 4- and 5-ring compounds had the highest content in the potentially bioavailable group. H. incongruens mortality in the range 6.7 to 100%, depending both on the sewage sludge and the dose applied. An increase of the sewage sludge dose usually resulted in an increase in toxicity. At the highest dose, a 100% mortality of H. incongruens was found in half of the sludges. The lowest dose, irrespective of the sludge type, caused over 40% growth inhibition. However, the results obtained did not allow for the establishing of an unambiguous relationship between various sludge toxicity levels and the content of potentially bio-available PAHs. In some cases only, the extraction using n-butanol explained the high difference in toxicity despite a slight differentiation in the PAH content.

Phytotoxicity of municipal sewage sludge composts related to physico-chemical properties, PAHs and heavy metals

The aim of the study was to determine the influence of the composting on the phytotoxicity of sewage sludge in relation to their physical-chemical properties, heavy metals and polycyclic aromatic hydrocarbons content. Four municipal sewage sludges were composted for 76 days. A Phytotoxkit Test and pot experiment with Lepidium sativum were used for bioassay. The total PAH content in sludges ranged from 3674.1 to 11236.3 microg kg(-1). Heavy metals content was in the range Cd (1.9-76 mg kg(-1)), Cr (27.6-120 mg kg(-1)), Cu (156-335 mg kg(-1)), Pb (37.5-59.5 mg kg(-1)), Ni (21.7-155 mg kg(-1)) and Zn (1015-1385 mg kg(-1)). The results showed a varied toxicity of sewage sludge in relation to the plant tested. In the case of two sludges a 100% inhibition of seed germination were noted. Sludge composting limited their negative influence on most of the phytotoxicity parameters. Only chlorophyll concentration was often lower than in the plant bred on compost obtained from sludge.

Application of hydroxypropyl[beta]cyclodextrin to evaluation of polycyclic aromatic hydrocarbon losses during sewage sludges composting

The aims of the present study were to test the application of the non-exhaustive extraction technique (NEET) with hydroxypropyl[beta]cyclodextrin (HPCD) for the evaluation of the content of potentially bioavailable polycyclic aromatic hydrocarbon (PAH) fraction as well as the evaluation of changes in the content of this fraction during composting of municipal sewage sludges. A possibility to apply this method for the forecasting of PAH losses during composting was also studied. Four sludges (from different sewage treatment plants) with varied properties have been selected for the present experiment. The sludges were composted for 76 days. PAH content was determined as extracted with dichloromethane (exhaustive extraction technique) and potentially bioavailable PAH content by means of HPCD (non-exhaustive extraction technique) in both sewage sludges and composts obtained from them. The content of fraction extracted with HPCD ranged from 63.5 to 83.1% depending on the sludge. After composting, a significant lowering of this fraction contribution was noted for 3 sludges. However, in the composts obtained, the fraction extracted with HPCD still constituted 54.7-62.1% of the total PAH content. The composting process clearly influenced a decrease in the bioavailable fraction in the case of 3- and 5-ring PAHs. However, the 4-ring PAHs content of bioavailable fraction did not undergo any significant changes. No satisfactory results were obtained when HPCD was used as a tool to forecast PAH losses. In a number of cases only, PAH remaining after HPCD extraction achieved a value similar to that of PAH after the composting process. In the case of a number of PAH, the method with HPCD application changed the values of the bioavailable fraction.

Investigation of potentially bioavailable and sequestrated forms of polycyclic aromatic hydrocarbons during sewage sludge composting

The present study focuses on the influence of the composting process on the formation of potentially bioavailable and sequestrated PAH fractions. The potentially bioavailable fraction was determined by means of a mild-solvent extraction (with n-butanol). The total and potentially bioavailable PAH content was evaluated in the consecutive composting stages, i.e. at the onset of the experiment, after the stabilization phase (on the 35th day), and after the maturation phase (on the 76th day). Four municipal sewage sludges with differentiated PAH content were selected for the present experiment. Eleven PAHs from the US EPA list (with exception of naphthalene, acenaphthylene, acenaphtene, fluorene and benz[ah]anthracene) were determined for the purpose of this experiment. The content of the total PAHs ranged from 3052 to 10352microg kg(-1). The share of the potentially bioavailable fraction was at a similar level in the sludge samples tested and ranged from 75% to 81%. Greater differences were noted in the share of the bioavailable fraction in the case of individual PAH groups. The influence of the composting process on the contribution of the potentially bioavailable fraction of the PAH clearly depended on the stage of the experiment and sewage sludge type. However, in the case of all sludges, a lowering of the bioavailable fraction by 19-52% as compared to the level at the outset of the experiment was observed. During the first phase (stabilization) of the sewage sludge composting process, a reduction of the PAH content took place mainly at the expense of potentially bioavailable fraction, whereas in the second phase (maturation), sequestration processes predominated. The above phenomenon was most clearly visible for the 6-rings PAHs.

The evaluation of sewage sludge and compost toxicity to Heterocypris incongruens in relation to inorganic and organic contaminants content

Sewage sludges and the composts were evaluated chemically and ecotoxicologically to determine their suitability as fertilizers for land application. Four municipal sewage sludges with various properties and pollutant contents were composted in aerobic conditions for 76 days. The content of heavy metals (Cd, Cu, Cr, Pb, Ni, Zn) and polycyclic aromatic hydrocarbons (14 from US EPA List) was analyzed in the sewage sludges and composts as well as together with their physico-chemical properties (total organic carbon, total nitrogen, pH, available forms of magnesium, phosphorus and potassium, cations content, cation exchange capacity, total of exchangeable bases). To evaluate the toxicity of the materials, bioassays with crustacean Heterocypris incongruens (Ostracodtoxkit test) were performed. Neither physical-chemical properties nor heavy metal content underwent any significant changes during the composting process. However, composting significantly influenced the range of losses of polycyclic aromatic hydrocarbons. The magnitude and the ranges of changes in the toxicity H. incongruens were found to be dependent on the tested parameter as well as on sewage sludge type and its dose. It was noted that composting could even increase the toxicity of sewage sludges. Sewage sludge toxicity was mainly determined by the presence of heavy metals, although for some sludges the contribution of organic pollutants as well as the synergistic activity of several factors could not be excluded. According to proposed classification (on the basis of Ostracodtoxkit test) only one sewage sludge/compost was suitable for land application. The studies conducted provide interesting information pointing to the necessity to supplement chemical studies with biological assays.

Changes of polycyclic aromatic hydrocarbons during composting of sewage sludges with chosen physico-chemical properties and PAHs content

The aim of the experiment was to determine changes in the PAH content during sewage sludge composting. The extent was evaluated to which sewage sludge properties influences on PAHs losses during composting. Five municipal sewage sludges were studied from sewage treatment plants located in the south-east of Poland, i.e. in Stalowa Wola, Kraśnik, Lublin, Zamość and Biłgoraj. The treatment plants selected were characterised by their differentiation with catchments area as well as the industrial character of the areas. Sludge composting was carried out in aerobic conditions in plastic containers for a period of 76 days. The content of 14 polycyclic aromatic hydrocarbons (PAHs) and some physical-chemical (TOC, Nt, TOC/Nt, CEC, BS, TEB, pH, available potassium and phosphorus, total forms of cations) sewage sludge properties were monitored. In the present study correlations between PAHs losses (during various phases of composting) and physical-chemical properties of sewage sludges and composts were also evaluated. The sewage sludges were characterised both by differentiated properties and by PAH content. The total PAH content (the sum of 14 PAHs from the EPA List with exception of naphthalene and acenaphthene) in the sludges ranged from 3674 to 11236 microg kg(-1). Four- and three-ring compounds were predominant in the sewage sludges. Almost all of the sludges were characterised by differentiated content levels of both individual PAHs groups and PAHs sum. After 76 days of composting, a significant lowering of the PAH content was observed in all sludges as compared to the beginning of the experiment. The range of total observed PAH losses was from 15.8% to 48.6%, depending on the sewage sludge. The largest lowering of the PAH content was observed in the sludge with the lowest concentration of the xenobiotics studied. The largest losses in individual PAHs were observed in the case of five- and six-rings compounds, and were probably related to strong pollutant binding by other components of the sewage sludge. The few significant relationships showed that PAH losses during composting were only slightly determined by the analysed physical-chemical properties.

Sample preparation of sewage sludge and soil samples for the determination of polycyclic aromatic hydrocarbons based on one-pot microwave-assisted saponification and extraction

A microwave-assisted sample preparation (MASP) procedure was developed for the analysis of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge and soil samples. The procedure involved the simultaneous microwave-assisted extraction of PAHs with n-hexane and the hydrolysis of samples with methanolic potassium hydroxide. Because of the complex nature of the samples, the extracts were submitted to further cleaning with silica and Florisil solid-phase extraction cartridges connected in series. Naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[e]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene, benzo[g,h,i]perylene, and indeno[1,2,3-cd]pyrene, were considered in the study. Quantification limits obtained for all of these compounds (between 0.4 and 14.8 microg kg(-1) dry mass) were well below of the limits recommended in the USA and EU. Overall recovery values ranged from 60 to 100%, with most losses being due to evaporation in the solvent exchange stages of the procedure, although excellent extraction recoveries were obtained. Validation of the accuracy was carried out with BCR-088 (sewage sludge) and BCR-524 (contaminated industrial soil) reference materials.

Persistence of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge-amended soil

The application of sewage sludge as a fertilizer is a common method used to improve soil properties. However, sewage sludge may contain various organic pollutants including polycyclic aromatic hydrocarbons. In the present study, the persistence of PAHs in soils fertilized with different sewage sludge doses was compared in relation to the sewage sludge dose applied (30, 75, 150, 300 and 600 Mgha(-1)) and the content of the polycyclic aromatic hydrocarbons in them. The experiment was carried out in two blocks of experimental plots divided according to the type of plants grown: field plants and perennial-willow. Sewage sludge addition to soils resulted in an increase in the content of polycyclic aromatic hydrocarbons in these soils. This increase was proportional to the quantity of sewage sludge applied. The results obtained showed that during a 42/54-month period, more than half of the individual PAHs introduced into the soil with sewage sludge were degraded. The scope of dissipation depended on the sewage sludge dose and the use to which the area was put. In the experiment with the willow only in the case of the highest sludge dose was a decrease in the PAH content above 50% noted; whereas in the case of the experiment with the field plants, it was higher by 50% for all sewage sludge doses. In experiment with field plants the highest scope of individual PAH disappearance was observed in the soil with the sewage sludge dose amounting to 300 Mgha(-1). In experiment with willow a relatively high dissipation of individual PAHs (>50%) was found in the treatment with the highest sludge dose (600 Mgha(-1)). A wider PAH dissipation range in the experiment with field plants was conditioned by the more favourable conditions created as a result of the breeding treatments applied. Agrotechnical treatments clearly increased the disappearance of the PAHs in those soils fertilized with the lowest sewage sludge doses (30 and 75 Mgha(-1)). The results obtained showed that the preferred method of treating a light soil fertilised with sewage sludges should be a one-year system, with a sludge application of 75 Mgha(-1).

Characterization of Polish sewage sludges with respect to fertility and suitability for land application

Twenty-one varieties of sewage sludge from municipal, municipal-industrial and industrial areas were analysed for their suitability for agricultural purposes. The samples were taken from an agricultural area of Poland characterised by a low level of industrialisation. The sewage sludges were characterised for total organic carbon and nitrogen, pH, available phosphorous and potassium, cation exchange capacity, total exchangeable bases, the degree of base saturation, the total trace metals (such as Cd, Co, Ni, Pb, Cu, Mn, Zn, Sr, V, Cr) and the content of polycyclic aromatic hydrocarbons (16 PAHs from EPA list). The results showed that the studied sludges can potentially enhance soil's agronomic properties. However in a few cases, the pH, ratio of total organic carbon to total nitrogen (TOC/Nt) and electrical conductivity were the exceptions. Trace metal contents in the sewage sludge studied varied widely (statistical significant) as a result of the size of the sewage producing unit, and especially, the content of industrial sludge. The results obtained for PAHs in sewage sludge showed a clear differentiation in the content of PAHs, which ranged from 2,039 to 36,439 microg/kg. The predominant contribution of 3- and 4-ring PAHs was observed. In the case of 6 sewage sludges the PAH content twice exceeded the allowable value.