Quantitative analysis of fuel-related hydrocarbons in surface water and wastewater samples by solid-phase microextraction

Solid-phase microextraction (SPME) parameters were examined on water contaminated with hydrocarbons including benzene and alkylbenzenes, n-alkanes, and polycyclic aromatic hydrocarbons (PAHs). Absorption equilibration times ranged from several minutes for low molecular weight compounds such as benzene to 5 h for high molecular weight compounds such as benzo[a]pyrene. Under equilibrium conditions, SPME analysis with GC/FID was linear over 3-6 orders of magnitude, with linear correlation coefficients (r(2)) greater than 0.96. Experimentally determined FID detection limits ranged from ～30 ppt (w/w hydrocarbon/sample water) for high molecular weight PAHs (e.g., MW > 202) to ～1 ppb for low molecular weight aromatic hydrocarbons. Experimental distribution constants (K) were different with 100- and 7-μm poly(dimethylsiloxane) fibers, and poor correlations with previously published values suggest that K depends on the fiber coating thickness and the sorbent preparation method. The sensitivity of SPME analysis is not significantly enhanced by larger sample volumes, since increasing the water volume (e.g., from 1 to 100 mL) has little effect on the number of analyte molecules absorbed by the fiber, especially for compounds with K < 500. Water sample storage should utilize silanized glassware, since hydrocarbon losses up to 70% could be attributed to unsilanized glassware walls when samples were stored for 48 h. Hydrocarbon losses at part-per-billion concentrations also occurred with surface waters due to partitioning onto part-per-thousand concentrations of suspended solids. Quantitative determinations of aromatic and aliphatic hydrocarbons (e.g., in gasoline-contaminated water) can be performed using GC/MS with deuterated internal standard or standard addition calibration as long as the target components or standards had unique ions for quantitation or sufficient chromatographic resolution from interferences. SPME analysis gave good quantitative performance with surface waters having high suspended sediment contents, as well as with coal gasification wastewater which contained matrix organics at 10(6)-fold higher concentrations than the target aromatic hydrocarbons. Good agreement was obtained between a 45-min SPME and methylene chloride extraction for the determination of PAH concentrations in creosote-contaminated water, demonstrating that SPME is a useful technique for the rapid determination of hydrocarbons in complex water matrices.     

Reusable Cavitand-Based Electrospun Membranes for the Removal of Polycyclic Aromatic Hydrocarbons from Water

The removal of toxic and carcinogenic polycyclic aromatic hydrocarbons (PAHs) from water is one of the most intractable environmental problems nowadays, because of their resistance to remediation. This work introduces a highly efficient, regenerable membrane for the removal of PAHs from water, featuring excellent filter performance and pH-driven release, thanks to the integration of a cavitand receptor in electrospun polyacrylonitrile (PAN) fibers. The role of the cavitand receptor is to act as molecular gripper for the uptake/release of PAHs. To this purpose, the deep cavity cavitand BenzoQxCav is designed and synthetized and its molecular structure is elucidated via X-Ray diffraction. The removal efficiency of the new adsorbent material toward the 16 priority PAHs is demonstrated via GC-MS analyses at ng L^?1 concentration. A removal efficiency in the 32%, to 99% range is obtained. The regeneration of the membrane is performed by exploiting the pH-driven conformational switching of the cavitand between the vase form, where the PAHs uptake takes place, to the kite one, where the PAHs release occurs. The absorbance and regeneration capability of the membrane are successfully tested in four uptake/release cycles and the morphological stability.     

Development of a room-temperature phosphorescence fiber-optic sensor

The design of a new fiber-optic sensor based on solid-surface room-temperature phosphorimetry is presented for the analyses of polycyclic aromatic hydrocarbons in water samples. Analytical figures of merit are given for several compounds of environmental importance. Limits of detection at the nanograms per milliliter level were estimated for pyrene, benzo[e]pyrene, benzo[ghi]perylene, 1,2:3,4-dibenzanthracene, coronene, and 2,3-benzofluorene. The linearity of response of the phosphorescence sensor was evaluated, showing a fairly linear behavior for quantitative analysis. Finally, the feasibility of monitoring polycyclic aromatic hydrocarbons in aqueous media was illustrated by identifying pyrene in a contaminated groundwater sample.     

Treatment of creosote-contaminated groundwater in a peat/sand permeable barrier--a column study

A column study was conducted to determine if a permeable barrier can be used to treat creosote-contaminated groundwater based on sorption and biodegradation, and to determine which processes remove the various creosote compounds. Creosote-contaminated water (sterile and non-sterile) was applied to sterile and non-sterile saturated columns with peat (20 vol.%) and sand (80 vol.%) for 2 months. Temperature was 9 degrees C, inlet oxygen concentration 9-10mg/l and average residence time was two days. The peat/sand barrier material removed 94-100% polycyclic aromatic hydrocarbons (PAHs), 93-98% nitrogen/sulfur/oxygen (NSO)-containing heterocyclic aromatic compounds, and 44-97% total phenols. The peat/sand material efficiently sorbed PAHs (>2 rings) and three-ring NSO-compounds, and also sorbed significant amounts of two-ring NSO-compounds and naphthalene. Naphthalene and NSO-compounds not sorbed were biological degraded. Phenol and cresols were efficiently removed by microbial degradation. The barrier material was somewhat less efficient removing dimethylphenols (DMPs) and trimethylphenols (TMPs), where DMPs were hardly sorbed and TMPs were hardly degraded. The results imply that a peat/sand barrier can treat creosote-contaminated groundwater. Modifications might be needed for enhanced removal of DMPs and TMPs, and oxygen supply might be necessary in aquifers with low oxygen content.     

A pilot study for the selection of a bioreactor for remediation of groundwater from a coal tar contaminated site.

Coal tars in soil at a gasworks site in South Eastern Australia led to groundwater contamination with polycyclic aromatic hydrocarbons (PAHs), mono-aromatic compounds (BTEX) and phenols. The scope of the study included testwork in laboratory scale bioreactors and evaluation of available commercial groundwater treatment units. Two bioreactor configurations, a submerged fixed film reactor (SFFR) and a fluidized bed bioreactor (FBR) were effective, with high efficiencies of contaminant removal (typically >90%) over a range of hydraulic retention times (HRT) (3-29 h). Specifically, concentrations of total PAH, naphthalene, pyrene and total phenols in the feedstock and effluent of the SFFR were 123, 60, 51, 1.38 and 0.004, 0.001, 0.004, 0.1mg/l, respectively. The FBR was only marginally less effective than the SFFR for the same groundwater contaminants. Discharge to sewer was the most appropriate end use for the effluent. SFFRs are regarded as being simpler in design and operation, and a commercially available unit has been identified which would be suitable for treating small volumes (<10 m(3) per day) of contaminated water collected at an interception trench at the site.     

气相色谱-质谱法测定电子电气产品材料中多环芳烃

本文建立了采用气相色谱-质谱联用检测电子电气产品材料中多环芳烃的方法。以丙酮-正己烷(1+1)为提取溶剂,利用自动索氏提取仪提取电子电气产品材料中多环芳烃,正己烷-二氯甲烷(3+2)混合液淋洗硅胶小柱净化,气相色谱-质谱联用仪检测,该方法检测限在0.2mg/kg,加标回收率在59%～99%之间,相对标准偏差(RSD)小于5%,线性范围在0.1mg/L～100mg/L,相关系数(r)大于0.999。实验结果表明,该方法简便、可靠,能满足电子电气产品材料中多环芳烃的检测要求。     

Reaction efficiencies and rate constants for the goethite-catalyzed Fenton-like reaction of NAPL-form aromatic hydrocarbons and chloroethylenes

The contaminants present as nonaqueous phase liquids (NAPLs) in the subsurface are long-term sources for groundwater pollution. Fenton-like reaction catalyzed by natural iron oxides such as goethite in soils is one of the feasible in situ chemical reactions used to remediate contaminated sites. This research evaluated the Fenton-like reaction of five chlorinated ethylenes and three aromatic hydrocarbons using goethite as the catalyst. The reaction efficiencies and rate constants of these compounds in NAPL and dissolved forms were compared. The content of goethite used in batch experiments was in the range similar to those found in subsurfaces. Low H2O2 concentrations (0.05 and 0.1%) were tested in order to represent the low oxidant concentration in the outer region of treatment zone. The results showed that at the tested goethite and H2O2 ranges, the majority of contaminants were removed in the first 120 s. When aromatics and chloroethylenes were present as NAPLs, their removal efficiencies and reaction constants decreased. The removal efficiencies of 0.02 mmol NAPL contaminants were 26-70% less than those of the dissolved. The measured rate constants were in the order of 10(9) M(-1) s(-1) for dissolved chlorinated ethylenes and aromatic hydrocarbons, but were 25-60% less for their NAPL forms. The initial dosage of H2O2 and NAPL surface areas (18.4-38.2 mm2) did not significantly affect reaction efficiencies and rate constants of chlorinated NAPLs. Instead, they were related to the octanol-water partition coefficient of compounds. For both dissolved and NAPL forms, aromatic hydrocarbons were more reactive than chlorinated ethylenes in Fenton-like reaction. These results indicated that the decrease in reaction efficiencies and rate constants of NAPL-form contaminants would pose more negative impacts on the less reactive compounds such as benzene and cis 1,2-DCE during goethite-catalyzed Fenton-like reaction.     

Layer-by-layer fabrication of chemical-bonded graphene coating for solid-phase microextraction

A new fabrication strategy of the graphene-coated solid-phase microextraction (SPME) fiber is developed. Graphite oxide was first used as starting coating material that covalently bonded to the fused-silica substrate using 3-aminopropyltriethoxysilane (APTES) as cross-linking agent and subsequently deoxidized by hydrazine to give the graphene coating in situ. The chemical bonding between graphene and the silica fiber improve its chemical stability, and the obtained fiber was stable enough for more than 150 replicate extraction cycles. The graphene coating was wrinkled and folded, like the morphology of the rough tree bark. Its performance is tested by headspace (HS) SPME of polycyclic aromatic hydrocarbons (PAHs) followed by GC/MS analysis. The results showed that the graphene-coated fiber exhibited higher enrichment factors (EFs) from 2-fold for naphthalene to 17-fold for B(b)FL as compared to the commercial polydimethylsioxane (PDMS) fiber, and the EFs increased with the number of condensed rings of PAHs. The strong adsorption affinity was believed to be mostly due to the dominant role of π-π stacking interaction and hydrophobic effect, according to the results of selectivity study for a variety of organic compounds including PAHs, the aromatic compounds with different substituent groups, and some aliphatic hydrocarbons. For PAHs analysis, the graphene-coated fiber showed good precision (<11%), low detection limits (1.52-2.72 ng/L), and wide linearity (5-500 ng/L) under the optimized conditions. The repeatability of fiber-to-fiber was 4.0-10.8%. The method was applied to simultaneous analysis of eight PAHs with satisfactory recoveries, which were 84-102% for water samples and 72-95% for soil samples, respectively.     

Particulate polycyclic aromatic hydrocarbons and n-alkanes in recycled paper processing operations

The aliphatic and polycyclic aromatic fractions of dust collected in the vicinity of recycled paper processing operations were analyzed using gas chromatography/mass spectrometry. Total measured dust concentration (up to 8.73+/-2.02 mg/m3) fluctuated substantially in the different steps of paper manufacture. This was attributed to the type of the operation such as, the release of fibers and particles during paper cutting and the use of reactive chemicals and excessive water under high temperature and pressure during the bleaching and the water rinsing/drying step. Particulate polycyclic aromatic hydrocarbons (PAHs) (from fluorene to benzo[ghi]perylene with mean concentrations from 3.8+/-0.5 to 41.4+/-0.4 ng/m3) and the unresolved mixture of branched, cyclic and unsaturated hydrocarbons (UCM) were measured in all samples while, n-alkanes from n-C20 to n-C27, were only observed in cutting and packaging areas (from 180.6+/-18.9 to 4297.9+/-794.9 ng/m3). The profile of occupational PAHs in bleaching and treatment of contaminated recycled raw paper was comparable to that observed for anthropogenic activities. The values of molecular diagnostic ratios indicated the contribution of oil residues and emissions from worklifts and other equipment used for pulp and paper handling. Total benzo[a]pyrene-equivalent (BaP) concentrations of particulate PAHs (varied from 323 up to 1104 pg/m3), provided evidence that workers were exposed to high quantities of PAHs as compared with exposures to urban air and other indoor settings, posing long-term threat to their health.     

Biodegradation of aged polycyclic aromatic hydrocarbons (PAHs) by microbial consortia in soil and slurry phases

Microbial consortia isolated from aged oil-contaminated soil were used to degrade 16 polycyclic aromatic hydrocarbons (15.72 mgkg(-1)) in soil and slurry phases. The three microbial consortia (bacteria, fungi and bacteria-fungi complex) could degrade polycyclic aromatic hydrocarbons (PAHs), and the highest PAH removals were found in soil and slurry inoculated with fungi (50.1% and 55.4%, respectively). PAHs biodegradation in slurry was lower than in soil for bacteria and bacteria-fungi complex inoculation treatments. Degradation of three- to five-ring PAHs treated by consortia was observed in soil and slurry, and the highest degradation of individual PAHs (anthracene, fluoranthene, and benz(a)anthracene) appeared in soil (45.9-75.5%, 62-83.7% and 64.5-84.5%, respectively) and slurry (46.0-75.8%, 50.2-86.1% and 54.3-85.7%, respectively). Therefore, inoculation of microbial consortia (bacteria, fungi and bacteria-fungi complex) isolated from in situ contaminated soil to degrade PAHs could be considered as a successful method.     

UV Raman spectroscopy of hydrocarbons

In this paper, the UV Raman spectra of a large number of saturated and alkyl-substituted monocyclic, bicyclic and polycyclic aromatic hydrocarbons are obtained at 220 and 233 nm excitation wavelengths. Also included are nitrogen- and sulphur-containing hydrocarbons. The spectra obtained are fluorescence free, even for such highly fluorescent compounds as perylene, consistent with earlier reports of UV Raman spectra of hydrocarbons. The hydrocarbon UV Raman spectra exhibit greatly improved signal-to-noise ratio when in the neat liquid or solution state compared with the neat solid state, suggesting that some surface degradation occurs under the conditions used here. Assignments are given for most of the bands and clear marker bands for the different classes of hydrocarbons are readily observable, although their relative intensities vary greatly. These results are discussed in the context of structure and symmetry to develop a consistent, molecular-based model of vibrational group frequencies.     

Comparison of ASE and SFE with Soxhlet, Sonication, and Methanolic Saponification Extractions for the Determination of Organic Micropollutants in Marine Particulate Matter

The methods of accelerated solvent extraction (ASE) and supercritical fluid extraction (SFE) of polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons, and chlorinated hydrocarbons from marine samples were investigated. The results of extractions of a certified sediment and four samples of suspended particulate matter (SPM) were compared to classical Soxhlet (SOX), ultrasonication (USE), and methanolic saponification extraction (MSE) methods. The recovery data, including precision and systematic deviations of each method, were evaluated statistically. It was found that recoveries and precision of ASE and SFE compared well with the other methods investigated. Using SFE, the average recoveries of PAHs in three different samples ranged from 96 to 105%, for ASE the recoveries were in the range of 97-108% compared to the reference methods. Compared to the certified values of sediment HS-6, the average recoveries of SFE and ASE were 87 and 88%, most compounds being within the limits of confidence. Also, for alkanes the average recoveries by SFE and ASE were equal to the results obtained by SOX, USE, and MSE. In the case of SFE, the recoveries were in the range 93-115%, and ASE achieved recoveries of 94-107% as compared to the other methods. For ASE and SFE, the influence of water on the extraction efficiency was examined. While the natural water content of the SPM sample (56 wt %) led to insufficient recoveries in ASE and SFE, quantitative extractions were achieved in SFE after addition of anhydrous sodium sulfate to the sample. Finally, ASE was applied to SPM-loaded filter candles whereby a mixture of n-hexane/acetone as extraction solvent allowed the simultaneous determination of PAHs, alkanes, and chlorinated hydrocarbons.     

Sequencing batch reactor performance treating PAH contaminated lagoon sediments

The applicability of sediment slurry sequencing batch reactors (SBR) to treat Venice lagoon sediments contaminated by polycyclic aromatic hydrocarbons (PAHs) was investigated, carrying out experimental tests. The slurry, obtained mixing tap water and contaminated sediments with 17.1 mg kg(-1) TS total PAHs content, was loaded to a 8l lab-scale completely stirred reactor, operated as a sequencing batch reactor. Oxygen uptake rate exerted by the slurry, measured by means of a DO-stat titrator, was used to monitor the in-reactor biological activity and to select the optimal operating conditions for the sediment slurry SBR. The PAHs removal efficiency was evaluated in different operating conditions, obtained changing the hydraulic retention time (HRT) of the lab-scale reactor and adding an external carbon source to the slurry. HRT values used during the experiments are 98, 70 and 35 days, whereas the carbon source was added in order to evaluate its effect on the biological activity. The results have shown a stable degradation of PAHs, with a removal efficiency close to 55%, not dependent on the addition of carbon source and the tested HRTs.     

Distribution of polycyclic aromatic hydrocarbons in water, sediment and soil in drinking water resource of Zhejiang Province, China

The spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was investigated in Qiantang River, the most important drinking water resource in Zhejiang Province, China. A total of 270 water samples, 64 sediment samples and 21 soil samples near riverbank were collected during January 2005-July 2006. The total concentrations of PAHs in water, sediments and soils ranged from 70.3 to 1844.4 ng/L, from 91.3 to 1835.2 ng/g and from 85.2 to 676.2 ng/g, respectively. The concentrations of PAHs in rural areas were lower than those in city zones. The concentrations of PAHs in July were the lowest while those in January were the highest during four seasons. The concentrations of PAHs in 2006 were compared with those in 2003 and 2005. The result showed PAHs pollution in this drinking water resource was increasing with time. The relationship between log K(oc) and log K(ow) of PAHs for field data on sediments and predicted values indicated that Qiantang River was mainly contaminated by petrogenic PAHs. The same result was obtained by the ratios of AN/(AN + Phen) and Flur/(Flur + Pye). Ratios of K(oc) for PAHs on sediments to that on corresponding soils indicated that PAHs in Qiantang River were mainly obtained from soil runoff.     

Three-way multivariate calibration procedures applied to high-performance liquid chromatography coupled with fast-scanning fluorescence spectrometry detection. Determination of polycyclic aromatic hydrocarbons in water samples

Three-way partial least-squares and n factor parallel factor analysis have been compared for the analysis of polycyclic aromatic hydrocarbons in water samples. Data were obtained with a chromatographic system set to record short-time chromatograms containing several unresolved peaks. The detection system consisted of a fast-scanning fluorescence spectra detector, which allows one to obtain three-dimensional data, where retention time, emission wavelengths, and fluorescence intensity are represented. The combined use of a multivariate calibration method and the three-dimensional data obtained from the HPLC-FSFS system allows resolution of closely eluting compounds, thus making a complete separation unnecessary. The procedure has been applied to tap water samples (spiked at 0.10 and 0.20 μg L(-)(1) levels) with good results, similar to those obtained with a HPLC system with a conventional fluorescence detector.     

Accelerated solvent extraction (ASE) of environmental organic compounds in soils using a modified supercritical fluid extractor

Accelerated solvent extraction (ASE) has been applied to the quantitative extraction of a selected list of semi-volatiles, which include polycyclic aromatic hydrocarbons (PAHs), phenols, polychlorinated biphenyls (PCBs) and total petroleum hydrocarbons. Two conventional supercritical fluid extraction (SFE) systems, the Suprex Prep Master and SFE/50 systems have been modified to function as ASE systems. Using solvent instead of supercritical fluid, extraction in an enclosed system proceeded under high pressure and temperature. Parameters such as extraction temperature and effect of modifiers were investigated. Although limited by a 150 degrees C maximum oven temperature, effective extraction could be carried out in less than 25 min for all the compounds studied. The technique was applied to a variety of real matrices contaminated with hydrocarbons, PAHs and phenols. Validations of the technique were performed using standard reference materials. Recoveries for these matrices were good (>75%) and precision (R.S.D.) was generally less than 10%. Primarily a rapid field extraction technique, comparison with other rapid extraction such as sonication and microwave assisted extraction (MAP) were made. Recoveries were found to be comparable to MAP and superior to sonication. On the present ASE system, only sequential extraction can be carried out but given the rapid nature of the process, about 15 samples can be carried out in a working day.     

Application of a fiber-optic NIR-EFA sensor system for in situ monitoring of aromatic hydrocarbons in contaminated groundwater

Interaction of analyte molecules with the evanescent wave of light guided in optical fibers is among the most promising novel sensing schemes that can be applied for environmental monitoring and on-line process analysis. By combining this measuring principle with the solid-phase extraction of analyte molecules into the polymer cladding of a fiber, it is possible to perform direct absorption measurements in the cladding, if the fiber is adapted to a conventional spectrometer/photometer. A big advantage of this arrangement is that the measurement is scarcely disturbed by matrix effects (background absorption of water in IR measurements, stray light due to turbidity in the sample). By using near-infrared (NIR) evanescent field absorption (EFA) measurements in quartz glass fibers coated with a hydrophobic silicone membrane it is possible to design and construct sensors for monitoring apolar hydrocarbons (HCs) in aqueous matrices.The paper presents a fiber-optic sensor system for the determination of aromatic HCs in groundwater or industrial wastewater. Generally, this instrument is suitable for quantitative in situ monitoring of pollutants such as aromatic solvents, fuels, mineral oils or chlorinated HCs with relatively low water saturation solubility (typically between 0.01 and 10 g l(-1)). The sensor probe is connected via all-silica fibers to a filter photometer developed at the IFIA, thus, allowing even remote analysis in a monitoring well. This portable instrument provides a total concentration signal of the organic compounds extracted into the fiber cladding by measuring the integral absorption at the 1st C--H overtone bands in the NIR spectral range.In situ measurements with the sensor system were performed in a groundwater circulation well at the VEGAS research facility of the University of Stuttgart (Germany). The NIR-EFA sensor system was tested within the frame of an experiment that was carried through in a tank containing sandy gravel with a groundwater-saturated aquifer, where soil and groundwater were contaminated with technical grade xylene. The goal of this experiment was to model and optimize the groundwater circulation well used for the remediation of the aquifer and soil surrounding the well. The sensor proved to trace reliably the total hydrocarbon concentration in the process water pumped from the well to a stripper column. Measurements were performed continuously over 4 months with C8 HC sum concentrations in the process water between 80 mg l(-1) down to the limit of detection, which is around 200 microg l(-1). It could be demonstrated that the fiber-optic sensor system is a valuable tool for near-real-time control of a remedial action technique and verification and documentation of its success.     

Distribution, partitioning and sources of polycyclic aromatic hydrocarbons in Daliao River water system in dry season, China

Eighteen polycyclic aromatic hydrocarbons (PAHs) were analyzed in 29 surface water, 29 suspended particulate matter (SPM), 28 sediment, and 10 pore water samples from Daliao River water system in dry season. The total PAH concentration ranged from 570.2 to 2318.6 ng L(-1) in surface water, from 151.0 to 28483.8 ng L(-1) in SPM, from 102.9 to 3419.2 ng g(-1) in sediment and from 6.3 to 46.4 microg l(-1) in pore water. The concentration of dissolved PAHs was higher than that of particulate PAHs at many sites, but the opposite results were generally observed at the sites of wastewater discharge. The soluble level of PAHs was much higher in the pore water than in the water column. Generally, the water column of the polluted branch streams contained higher content of PAHs than their mainstream. The environmental behaviors and fates of PAHs were examined according to some physicochemical parameters such as pH, organic carbon, SPM content, water content and grain size in sediments. Results showed that organic carbon was the primary factor controlling the distribution of the PAHs in the Daliao River water system. Partitioning of PAHs between sediment solid phase and pore water phase was studied, and the relationship between logK(oc) and logK(ow) of PAHs on some sediments and the predicted values was compared. PAHs other than naphthalene and acenaphthylene would be accumulated largely in the sediment of the Dalaio River water system. The sources of PAHs were evaluated employing ratios of specific PAHs compounds and different wastewater discharge sources, indicating that combustion was the main source of PAHs input.