A comparative study of solvent extraction of total petroleum hydrocarbons in soil

Three non-specific methods for the extraction of total petroleum hydrocarbons (TPH) from soil into organic solvent were compared. The techniques used for sample preparation were Soxhlet extraction, closed-vessel microwave-assisted extraction, and CEN shake extraction. The total concentrations of extracted compounds in the boiling point range of C10–C40 were determined by gas chromatography with flame ionization detection. The best recovery (99%) and repeatability (±3%) from standard oil mixtures were obtained with microwave-assisted extraction. However, the different extraction methods exhibited different behaviour when spiked soil samples were extracted. The best repeatability was obtained with CEN shake extraction (±6%) but the repeatability values for Soxhlet and microwave-assisted methods were quite high (>20%). However, the larger uncertainties of the latter extraction methods does not necessarily limit the applicability of these methods to the determination of petroleum hydrocarbons in soil, as in the assessment of soil contamination the expanded uncertainty of the result is usually not limited by analytical uncertainty, but rather by the uncertainty of the primary sampling stage. However, distinctive variation found in the chromatographic profiles illustrates that discretion should be obeyed when chromatograms obtained after application of different extraction methods on petroleum contaminated samples are to be used in the fingerprinting or age dating studies. Otherwise, misleading conclusions concerning the age of spillage could be drawn.     

In situ Remediation of Petroleum Contaminated Groundwater by Permeable Reactive Barrier with Hydrothermal Palygorskite as Medium

The permeable reactive barrier(PRB) has proven to be a cost-effective technique to remediate the petroleum contaminated groundwater at a northeast field site in China. In this study, the geology, hydrogeology and contamination characterization of the field site were investigated and the natural hydrothermal palygorskite was chosen as a reactive medium. Furthermore, the adsorption of the total petroleum hydrocarbons(TPH) in the groundwater onto hydrothermal palygorskite and the adsorption kinetics were investigated. The results indicate that the removal rates of TPH, benzene, naphthalene and phenantharene could all reach up to 90% by hydrothermal palygorskite with a diameter of 0.25―2.00 mm that had been thermally pretreated at 140 ℃. The adsorption of TPH onto hydrothermal palygorskite after pretreatment followed a pseudo-second-order kinetic model and a Langmuir adsorption isotherm, suggesting that the theoretic adsorption capacity of hydrothermal palygorskite for adsorbate could be 4.2 g/g. Scanning electron microscopy(SEM), infrared spectroscopy(IR), X-ray diffraction(XRD) and X-ray fluorescence spectroscopy(XRF) were carried out to analyze the adsorption mechanism. The results reveal that hydrothermal palygorskite is a fibrous silicate mineral enriched in Mg and Al with large surface area and porosity. The dense cluster acicular and fibrous crystal of hydrothermal palygorskite, and its effect polar group ―OH played an important role in the physical and chemical adsorption processes of it for contaminants. This study has demonstrated hydrothermal palygorskite is a reliable reactive medium for in situ remediation of petroleum contaminated groundwater at field sites.     

程序升温技术考察镍在钼基催化剂中的作用

利用程序升温技术考察了Ni促进的和未促进的钼基催化剂上进行噻吩加氢脱硫（HDS）,苯、环己烯的程序升温加氢反应（TPH）,通过对硫化态催化剂的程序升温还原（TPR）、程序升温脱附（TPD）以及程序升温氧化（TPO）等表征,发现添加№之后调变了Mo—S键合行为,使得催化剂在反应过程中易于形成或者维持更多的S配位空位数目,...     

Determination of marker pteridins and biopterin reduced forms, tetrahydrobiopterin and dihydrobiopterin, in human urine, using a post-column photoinduced fluorescence liquid chromatographic derivatization method

A liquid chromatographic method for the simultaneous analysis of marker pteridins and biopterin reduced forms, in urine samples is proposed. A Zorbax Eclipse XDB-C18 column was used for the chromatographic separation, using a 98/2 (v/v), citrate buffer (pH 5.5)-acetonitrile mobile phase, in isocratic mode. A post-column photoderivatization was carried out with an on-line photoreactor, located between a diode array detector (DAD) and a fast scanning fluorescence detector (FSFD). Neopterin (NEO), biopterin (BIO), pterin (PT) and dihydrobiopterin (BH2) were determined by measuring native fluorescence, using the photoreactor in OFF-mode, and tetrahydrobiopterin (BH4) was determined by measuring of the induced fluorescence of the generated photoproducts, using the photoreactor in ON-mode. In addition, Creatinine (CREA), as a reference of metabolites excrection in urine, was simultaneously determined using the DAD detector. Detection limits were 0.2, 13.0, 0.3, 0.3 and 3.5 ng mL⁻¹, for NEO, BH2, BIO, PT and BH4, respectively, and 0.4 μg mL⁻¹ for CREA. Ratio values for NEO/CREA, PT/CREA, BH4/CREA, BH2/CREA, NEO/BIO and BIO_total/CREA, in urine samples, of healthy children and adults, phenylketonuric children and infected mononucleosis children, are reported. A comparative study, about the mean values obtained for each of the compounds, by the present procedure and by the classical iodine oxidation method (Fukushimás method), has been performed, in urine samples belonging to healthy volunteers. The values obtained were BH4/CREA: 0.41, BH2/CREA: 0.31 and BIO_total/CREA: 0.73, by the proposed method, and BH4/CREA: 0.35, BH2/CREA: 0.20 and BIO_total/CREA: 0.48, by iodine oxidation method.     

Evaluating the impact of GC operating settings on GC-FID performance for total petroleum hydrocarbon (TPH) determination

Interlaboratory comparisons for the analysis of mineral oil have indicated that many laboratories have problems in producing data of acceptable quality, mainly because of variations in the gas chromatographic settings used in the determination. A D-optimal design was therefore utilized to study the effects of six different GC operating settings on the GC performance criterion proposed by ISO and CEN draft standards ISO/FDIS 16703:2004 and CEN prEN 14039:2004:E for total petroleum hydrocarbon (TPH) determination. Both qualitative and quantitative factors were investigated. The results indicate that the performance criterion can only be achieved if the splitless injection settings are carefully optimized. Otherwise mass discrimination readily affects the validity of the results. The most critical factors affecting GC performance were the inlet liner design, inlet temperature and injection volume. The methods, however, were robust with respect to small changes in split vent time, GC column flow and FID temperature. The results show that non-discriminating splitless injection can only be obtained by optimizing the injector settings with respect to the significant factors. The main conclusion that can be drawn is that, if no further standardization is to be given for TPH determination by GC-FID, then a proper estimate of the expanded uncertainty should be appended to the TPH results. Only then can the reliability of the TPH results be guaranteed and further justification thus gained to support the end-use of the data.     

Microbial dynamics in oil-impacted prairie soil

A remote site in the Tallgrass Prairie Preserve (Osage County, OK) was contaminated with crude oil by a pipeline break in 1992. In 1996, the contaminated soil was bioremediated by blending with uncontaminated soil, prairie hay, buffalo manure, and commercial fertilizers, and spreading in a shallow layer over uncontaminated soil to create a landfarm. The landfarm was monitored for two years for aerobic and anaerobic bacteria, soil gases indicative of microbial activity, and for changes in the concentration of total petroleum hydrocarbons (TPH). Levels of hydrocarbon degraders and soil gas indicators of aerobic degradation were stimulated in the landfarm during the first warm season relative to uncontaminated prairie soil. However, these same indicators were less conclusive during the second warm season, indicating depletion of the more easily degradable hydrocarbons, although the landfarm still contained 6,800 mg/kg TPH on the average at the beginning of the second warm season. Methane formation and methanogen counts were clearly stimulated in the first warm season relative to uncontaminated prairie soil, in dicating that methanogenesis plays an important role in the mineralization of hydrocarbons even in these shallow soils.     

Stability and Reactivity of the Active Assemblies in Modified Graphites Characterized by TPD and TPH

Synthetic graphites, as prepared and modified by sulphonation or acetylation, were doped by Fe-, Co-, Ni- and Ca-nitrates. Temperature Programmed Desorption (TPD) and Temperature Programmed Hydrogenation (TPH) were applied to characterize thermal stability and reactivity of the active assemblies formed on the matrix surface. The functional groups lowered the reactivity of the graphites. Thermally less stabile carboxylic groups decomposed with formation of secondary groups giving more reactive material. Fe containing as well as sulphonated graphites showed a much lower reactivity than the others. Synergistic effects of Co/Ca and Ni/Ca were confirmed in the graphite materials. This revised version was published online in July 2006 with corrections to the Cover Date.     

Managed bioremediation of soil contaminated with crude oil soil chemistry and microbial ecology three years later

Analysis of samples taken from three experimental soil lysimeters demonstrated marked long-term effects of managed bioremediation on soil chemistry and on bacterial and fungal communities 3 yr after the application of crude oil or crude oil and fertilizer. The lysimeters were originally used to evaluate the short-term effectiveness of managed (application of fertilizer and water, one lysimeter) vs unmanaged bioremediation (one lysimeter) of Michigan Silurian crude oil compared to one uncontaminated control lysimeter. Three years following the original experiment, five 2-ft-long soil cores were extracted from each lysimeter, each divided into three sections, and the like sections mixed together to form composited soil samples. All subsequent chemical and microbiological analyses were performed on these nine composited samples. Substantial variation was found among the lysimeters for certain soil chemical characteristics (% moisture, pH, total Kjeldahl nitrogen [TKN], ammonia nitrogen [NH₄-N], phosphate phosphorous [PO₄-P], and sulfate [SO₄ ⁻²]). The managed lysimeter had 10% the level of total petroleum hydrocarbons (TPH-IR) found in the unmanaged lysimeter. Assessment of the microbial community was performed for heterotropic bacteria, fungi, and aromatic hydrocarbon-degrading bacteria (toluene, naphthalene, and phenanthrene) by dilution onto solid media. There was little difference in the number of heterotrophic bacteria, in contrast to counts of fungi, which were markedly higher in the contaminated lysimeters. Hydrocarbon-degrading bacteria were elevated in both oil-contaminated lysimeters. In terms of particular hydrocarbons as substrates, phenanthrene degraders were greater in number than naphthalene degraders, which outnumbered toluene degraders. Levels of sulfate-reducing bacteria seem to have been stimulated by hydrocarbon degradation.     

A multi-process phytoremediation system for decontamination of persistent total petroleum hydrocarbons (TPHs) from soils

Multiple techniques that affect different aspects of contaminant removal can improve remediation of persistent hydrocarbons from soils. We have developed a multi-process phytoremediation system (MPPS) that is composed of land-farming (aeration and light exposure), contaminant degrading bacteria, plant-growth-promoting rhizobacteria (PGPR), and growth of the contaminant-tolerant plant, Tall Fescue (Festuca arundinacea). In this study, the MPPS was applied to a contaminated soil acquired from the Imperial Oil land farm site in Sarnia, Ontario, Canada. This soil was contaminated with oil refinery sludge to a level of approximately 5% (w/w) total petroleum hydrocarbons (TPHs). Over an initial 4-month period, the average efficiency of removal of persistent TPHs by the MPPS was twice that of land-farming alone, 50% more than bioremediation alone, and 45% more than phytoremediation alone. Importantly, the MPPS removed oil fractions 2, 3 and 4 with equal efficiency. Therefore, the highly hydrophobic, recalcitrant TPH fractions were remediated from the soil with the MPPS. After a second 4-month period, the MPPS removed 90% of all fractions of TPHs from the soil. Phytoremediation alone was able to remove only about 50% of TPHs in the same time period. The key elements for successful phytoremediation were the use of a plant species that can proliferate in the presence of high levels of contaminants, and strains of PGPR that increase plant tolerance and accelerate plant growth in heavily contaminated soils.