Time to Say Goodbye to the 16 EPA PAHs? Toward an Up-to-Date Use of PACs for Environmental Purposes

The 16 EPA PAHs have played an exceptionally large role above all in environmental and analytical sciences in the last 40 years, but now there are good reasons to question their utility in many circumstances even though their use is so established and comfortable. Here we review the reasons why the list has been so successful and why sometimes it is seen as less relevant. Three groups of polycyclic aromatic compounds (PAC) are missing: larger and highly relevant PAHs, alkylated PACs, and compounds containing heteroatoms. Attempts to improve the situation for certain matrixes are known and here: (1) an updated list of PAHs (including the 16 EPA PAHs) for the evaluation of the toxicity in the environment (40 EnvPAHs); (2) a list of 23 NSO-heterocyclic compounds and 6 heterocyclic metabolites; and (3) lists of 10 oxy-PAHs and 10 nitro-PAHs are proposed for practical use in the future. A discussion in the scientific community about these lists is invited. Although the state of knowledge has improved dramatically since the introduction of the 16 EPA PAHs in the 1970s, this summary also shows that more research is needed about the toxicity, occurrence in the environment and chemical analysis, particularly of alkylated PAHs, higher molecular weight PAHs and substituted PACs such as amino-PAHs, cyano-PAHs, etc.. We also suggest that a long overdue discussion of an update of regulatory environmental PAH analysis is initiated.     

CHARACTERIZATION OF SELECTED SPECIATED ORGANIC COMPOUNDS ASSOCIATED WITH PARTICULATE MATTER IN AMBIENT AIR OF THE OUTSKIRTS OF ROME

The organic fraction of airborne particulate matter includes a wide variety of organic compounds, but the present research focus is on Polycyclic Aromatic Hydrocarbons (PAHs) and their nitrated derivatives (nitro-PAHs) because of the well-known health risk associated with these organics. In order to identify and assess the sources of hydrocarbon inputs into the environment n-alkanes content and the relative carbon preference index were utilized.

Special consideration was given to nitro-PAHs. The aim of this work was to demonstrate the presence in atmosphere of nitro-PAHs not usually studied, which may be responsible for part of the high direct-acting mutagenic activity of unknown origin observed for the airborne particulate material.

Of the 38 particulate-associated nitro-PAH compounds measured, 21 were described for the first time and 17 were detected in real samples, although those 21 nitro-PAHs were reported as positional isomers of corresponding PAHs, with the position of the NO₂ group not determined.     

Volatilization Loss of 6 PAHs with 2–4 Rings Related to Coal Extracts

ABSTRACT

With 3 different bottles, the volatilities of 6 polycyclic aromatic hydrocarbons (PAHs), namely, acenaphthylene, acenaphthene, fluorene, phenanthrene, fluoranthene and pyrene, which were used as model compounds of coal here, had been measured by using gas chromatography/mass spectrometer (GC/MS). The results indicate that although these PAHs have a high boiling point (BP), some PAHs such as acenaphthylene and acenaphthene can be lost rapidly through volatilizing. Even pyrene, having a BP as high as 404°C, can also be lost by volatilizing for a longer period, such as 4 days or more. The volatilization loss of the PAHs is also related to the container. PAHs in wide-mouthed bottles will volatilize faster than in narrow-mouthed bottles. The volatilization loss of the PAHs and other compounds may lead to incorrect results in quantitatively analyzing them in coal extraction, if coal extracts are dried. So, the coal extracts by organic solvents should not be dried before measuring by GC/MS.     

Bioactive compounds and advanced processing technology: Phaleria macrocarpa (sheff.) Boerl,a review

Recent technological advances and the development of new methods has provided an opportunity to obtain highly purified natural bioactive compound extracts with potential for the treatment and prevention of human diseases. The use of hazardous and toxic solvents for the extraction and processing of bioactive compounds from plant materials is considered a problem for health, safety and environmental pollution. Advanced technology aims to increase production of the desired compounds and find an alternative to using toxic solvents in the extraction of bioactive compounds from plant materials. The ever growing interest in plant bioactive compounds and today's concerns about environment issues have led to an increased need for an efficient and green extraction method. This review is focused on the extraction of bioactive compounds from plants using advanced and environment‐friendly methods such as supercritical fluid extraction, microwave‐assisted extraction, ultrasound‐assisted extraction and similar techniques that can extract rapidly and free from organic residues. An updated overview of the bioactive compounds present in the plant Phaleria macrocarpa and its extraction, fractionation, purification and isolation is provided. The advantages and disadvantages of both conventional and non‐conventional extraction methods are also discussed in this review. © 2014 Society of Chemical Industry     

高效液相色谱法测定水源中苯并芘的方法研究

多环芳烃(PAHs)是煤,石油,木材,烟草,有机高分子化合物等有机物不完全燃烧时产生的挥发性碳氢化合物,是重要的环境和食品污染物。本方法是通过对高效液相色谱仪的开发应用,完成生活饮用水/水源水中苯并芘的方法研究,初步建立地下水污染地质调查评价阶段有机污染物测定方法的技术体系。     

SEMIPERMEABLE MEMBRANE DEVICE-AVAILABILITY OF POLYCYCLIC AROMATIC HYDROCARBONS IN RIVER WATERS AND WASTEWATER TREATMENT PLANT EFFLUENTS

River waters and wastewater treatment plant effluents contain hydrophobic organic compounds (HOCs) such as polycyclic aromatic hydrocarbons (PAHs) which are persistent, bioaccumulative, and dangerous for the environment. The biological risk assessment of HOCs requires the estimation of their bioavailable fraction in addition to the total contamination of the media. The bioavailability of HOCs depends on the characteristics of the aquatic environments. In particular, the presence of organic matter (OM) usually reduces the bioavailability of HOCs by trapping them and preventing them from crossing biological membranes. The semipermeable membrane device (SPMD) technique is used to evaluate bioavailable fractions of HOCs. We tested the influence of aquatic and more particularly OM characteristics on the SPMD-availability of PAHs, in several river waters (up and downstream a large town) and in wastewater treatment plant effluents. Thirteen priority PAHs were analyzed in total water and in SPMDs. Aquatic environments were characterized for their pH, ionic strength, temperature, chlorophyll A, and suspended solids contents. Total and dissolved OMs were characterized for aromaticity, biodegradability, molecular weight, and hydrophobicity. The total PAH contamination increased downstream the river; wastewater effluents were proven to be a source of SPMD-available PAHs. We attempted to establish relationships between the characteristics of organic matter and the SPMD-availability in order to initiate an aquatic environment typology: The SPMD-availability was negatively related to dissolved OM molecular weight and aromaticity, and positively related to biodegradability.     

Natural Organohalogens in Sediments

Recent fluvial, lacustrine and marine sediments were found to contain significant concentrations of organohalogens which cannot be explained by known anthropogenic halogen compounds. The assumption of a natural source for the major part of these organohalogens is strongly supported by the fact that in lacustrine sediments deposited some hundred years ago – where no industrial chlorinated organic compounds should be expected – concentrations between 30 and 100 mg/kg of adsorbable organic halogens (AOX, expressed as equivalent chlorine) were detected. In anoxic sapropels of the Black Sea, several thousand years old and having a high organic content (mainly derived from marine phytoplankton), organic bromine and iodine occur at levels up to 313 and 465 mg/kg, respectively. AOX concentrations in biogenic sediments from various epochs and representing different stages of coalification (peat – lignite – bituminous coal – anthracite) are clear evidence for naturally occurring organohalogens. Plant material has therefore to be considered as the most important primary source of high molecular weight organohalogens in sediments. In addition, natural low molecular organohalogens produced by bacteria, fungi, algae (such as haloalkanes, terpenes, amino acids and peptides, chlorophenols etc.) will also accumulate in the sediment and become part of its primary organohalogen content. As a secondary source of organohalogens in sediments their formation in the sediment itself has to be considered. Biotic halogenation of organic substrates by haloperoxidases (to occur in algae and other marine organisms but also in terrestrial lichens and fungi) leading to volatile organohalogens has been observed already. Only little knowledge exists on abiotic halogenation. In preliminary investigations in the system trichloroacetic acid – water – humic substances, chlorinated compounds could be identified. A transfer of (low molecular) organohalogens from the sediment into the interstitial water is obvious: If compared with the supernatant lake water, AOX concentrations in interstitial water of Lake Constance sediments are enriched by a factor of 20–70. Under anaerobic conditions bacterial decomposition of organohalogens leads to the release of halide ions into the interstitial water of the sediment. The results presented here fully confirm our previous conclusion [1], that the AOX value cannot be used exclusively as a sum parameter for anthropogenic organic halogen compounds.     

PAHs在天然水体沉积物中的迁移转化及生态效应

水体沉积物是水体生态系统的重要组成部分,是水体多种营养物、污染物的汇(Sink)和源(Source),是众多污染物在环境中迁移转化的载体、归宿和蓄积库.多环芳烃(PAHs)是一大类广泛存在于环境中的有机污染物,在水体中其主要归宿是沉积物.文中详细论述了多环芳烃在天然水体中迁移、转化规律,并浅述了多环芳烃在沉积物中的生态...     

Emission characteristics of PAHs, benzene and phenol group hydrocarbons in O2/RFG waste incineration processes

This study applies the oxygen/recycled flue gas (O₂/RFG) combustion technology for waste incineration in a laboratory-scale fluidized bed incinerator to investigate the effects of different RFG percentages and O₂ concentrations on the emission characteristics of organic pollutants (PAHs, phenol and benzene hydrocarbons). Experimental results show that most PAHs with high-ring structures were present in solid-phase and most low-ring PAHs were present in gas-phase. The major compounds of benzene and phenol hydrocarbons were benzene, toluene, trichlorobenzene and 2,4-dinitrophenol, phenol, dichlorophenol, respectively. As the O₂ concentration in feed gas was increased from 21% to 40%, the emissions of solid- and gas-phase PAHs and phenol compounds were decreased but not for benzene compounds. Increasing RFG percentages would decrease the emissions of gas-phase PAHs, benzene and phenol compounds, but increased those of solid-phase pollutants. The best operating conditions of such O₂/RFG combustion system to reduce the emissions of PAHs and phenol compounds were 40% O₂, 35% RFG, and that for benzene compounds was 21% O₂, 75% RFG. Comparing with conventional air combustion system, the best diminution efficiencies of PAHs, benzene and phenol compounds at such O₂/RFG conditions were 59.54%, 70.97% and 52.60%, respectively. With proper feed gas compositions and RFG percentages, the combustion efficiency and destruction efficiency of organic pollutants can be improved by this O₂/RFG combustion technology.     

Does the odor from sponges of the genus Ircinia protect them from fish predators?

Caribbean sponges of the genus Ircinia contain high concentrations of linear furanosesterterpene tetronic acids (FTAs) and produce and exude low-molecular-weight volatile compounds (e.g., dimethyl sulfide, methyl isocyanide, methyl isothiocyanate) that give these sponges their characteristic unpleasant garlic odor. It has recently been suggested that FTAs are unlikely to function as antipredatory chemical defenses, and this function may instead be attributed to bioactive volatiles. We tested crude organic extracts and purified fractions isolated from Ircinia campana, I. felix, and I. strobilina at naturally occurring concentrations in laboratory and field feeding assays to determine their palatability to generalist fish predators. We also used a qualitative technique to test the crude volatile fraction from I. felix and I. strobilina and dimethylsulfide in laboratory feeding assays. Crude organic extracts of all three species deterred feeding of fishes in both aquarium and field experiments. Bioassay-directed fractionation resulted in the isolation of the FTA fraction as the sole active fraction of the nonvolatile crude extract for each species, and further assays of subfractions suggested that feeding deterrent activity is shared by the FTAs. FTAs deterred fish feeding in aquarium assays at concentrations as low as 0.5 mg/ml (fraction B, variabilin), while the natural concentrations of combined FTA fractions were >5.0 mg/ml for all three species. In contrast, natural mixtures of volatiles transferred from sponge tissue to food pellets and pure dimethylsulfide incorporated into food pellets were readily eaten by fish in aquarium assays. Although FTAs may play other ecological roles in Ircinia spp., these compounds are effective as defenses against potential predatory fishes. Volatile compounds may serve other defensive functions (e.g., antimicrobial, antifouling) but do not appear to provide a defense against fish predators.     

A comparative study of lupeol extraction from a by-product of lupin processing by hydrophobic natural deep eutectic solvents and their precursor components

A series of hydrophobic natural deep eutectic solvents (HNADESs) have been employed to extract lupeol from lupin seed coat at 30 and 70°C. The extraction yields have been compared with those obtained with conventional organic solvents. In general, lupeol extraction yields (LEYs) obtained when using HNADES are somewhat smaller than those obtained if organic solvents are used. However, the nature of the HNADES mixtures as green solvents represents a superior performance in terms of sustainability of the extraction process. Additionally, an investigation has been carried out in order to compare the LEYs obtained when using the HNADES mixtures with those obtained if the isolated precursor compounds are employed at a temperature (70°C) where both HNADES and the corresponding precursor compounds are liquids. Surprisingly, LEYs for lupeol at 70°C were found to be, in some cases, slightly higher if the precursor compounds are used in comparison with the proper HNADES mixtures. It seems that the unique properties of the HNADES mixtures are not enough to perform better as extractants in comparison with the isolated precursor compounds at moderate temperatures, at least for the case of lupeol from lupin seed coat. Some hints are presented to explain these results. Practical Applications: The demand to use by-products, such as raw materials, to obtain potential bioactive compounds is gaining strong attention in the last years. The use of green solvents to extract these compounds is also envisaged to obtain substances in an environment-friendly way and with high sustainability for the economy and end-consumers. The main aim of this work is the extraction of lupeol from lupin seed coat by using on one side different hydrophobic natural deep eutectic solvent (HNADES) mixtures, and on the other side by using the precursor compounds of the mixtures, in order to evaluate the efficiency of these green extraction solvents in the recovery of bioactive compounds with health benefits from waste material. Our results show that lupeol can be extracted both with the HNADES mixtures and with their precursor components at moderate temperatures with similar efficiency. This work questions the need of using HNADES as clean extraction solvents as the precursor compounds have themselves interesting extracting capacities.     

Beyond 16 Priority Pollutant PAHs: A Review of PACs used in Environmental Forensic Chemistry

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in soils and sediments, particularly in urbanized environments in which the concentrations of 16 (or so) PAHs are regulated. Distinguishing among the numerous PAH sources is of practical and legal concern and thereby is often an objective of environmental forensic chemistry studies. Studies of prospective sources and impacted soils and sediments that rely upon the 16 U.S. EPA Priority Pollutant PAHs are disadvantaged, as these few compounds generally lack the specificity to distinguish among different PAH sources in the environment. Advances in analytical and interpretive methods over several decades have shown that different PAH sources can be more defensibly distinguished using modified EPA Method 8270 that, among other improvements, measure many other polycyclic aromatic compounds (PACs) that co-occur with the Priority Pollutant PAHs in different sources and in the environment. The PACs include variously-alkylated PAHs and polycyclic aromatic sulfur heterocyclics (PASHs) homologs and individual isomers, which are herein reviewed. Collectively, these PACs provide a higher degree of specificity among PAC sources and can be used to understand the effects of weathering on PAH assemblages. Despite their diagnostic capacity, PACs should not be relied upon at the exclusion of other compound groups (e.g., petroleum biomarkers) in most environmental forensic chemistry studies. In light of these advances, source characterization studies that rely only upon the 16 (or so) Priority Pollutant PAHs warrant considerable caution.     

Environmental pollution and emission factors of electronic cigarettes,heat-not-burn tobacco products,and conventional cigarettes

The increasing popularity of electronic cigarettes (e-cigarettes) and, more recently, the new “heat-not-burn” tobacco products (iQOS) as alternatives to traditional tobacco cigarettes has necessitated further documentation of and research into the composition and potential health risks/benefits of these devices. In a recent study, we compared second-hand exposure to particulate metals and organic compounds from e-cigarettes and traditional cigarettes, by conducting continuous and time-integrated measurements in an indoor environment, followed by computing the emission rates of these species using a single-compartment mass balance model. In this study, we have used a similar approach to further expand our previous analyses by characterizing black carbon, metal particles, organic compounds, and size-segregated particle mass and number concentrations emitted from these devices in addition to the newly marketed iQOS. Analysis of the iQOS side-stream smoke indicated that the particulate emission of organic matter from these devices is significantly different depending on the organic compound. While polycyclic aromatic hydrocarbons (PAHs) were mostly non-detectable in the iQOS smoke, certain n-alkanes, organic acids (such as suberic acid, azelaic acid, and n-alkanoic acids with carbon numbers between 10 and 19) as well as levoglucosan were still emitted in substantial levels from iQOS (up to 2–6 mg/h during a regular smoking regimen). Metal emissions were reduced in iQOS smoke compared to both electronic cigarettes and conventional cigarettes and were mostly similar to the background levels. Another important finding is the presence of carcinogenic aldehyde compounds, including formaldehyde, acetaldehyde, and acrolein, in iQOS smoke, although the levels were substantially lower compared to conventional cigarettes.

Copyright © 2017 American Association for Aerosol Research     

Differential effects of diesel exhaust particles on T cell differentiation and autoimmune disease

Background

Exposure to particulate matter (PM) has been associated with increased incidence and severity of autoimmune disease. Diesel PM is primarily composed of an elemental carbon core and adsorbed organic compounds such as polycyclic aromatic hydrocarbons (PAHs) and contributes up to 40% of atmospheric PM. The organic fraction (OF) of PM excludes all metals and inorganics and retains most organic compounds, such as PAHs. Both PM and OF increase inflammation in vitro and aggravate autoimmune disease in humans. PAHs are known aryl hydrocarbon receptor (AHR) ligands. The AHR modulates T cell differentiation and effector function in vitro and in experimental autoimmune encephalomyelitis (EAE), a murine model of autoimmune disease. This study aims to identify whether the total mass or active components of PM are responsible for activating pathways associated with exposure to PM and autoimmune disease. This study tests the hypothesis that active components present in diesel PM and their OF enhance effector T cell differentiation and aggravate autoimmune disease.

Results

Two different diesel samples, each characterized for their components, were tested for their effects on autoimmunity. Both diesel PM enhanced effector T cell differentiation in an AHR-dose-dependent manner and suppressed regulatory T cell differentiation in vitro. Both diesel PM aggravated EAE in vivo. Fractionated diesel OFs exhibited the same effects as PM in vitro, but unlike PM, only one diesel OF aggravated EAE. Additionally, both synthetic PAH mixtures that represent specific PAHs found in the two diesel PM samples enhanced Th17 differentiation, however one lost this effect after metabolism and only one required the AHR.

Conclusions

These findings suggest that active components of PM and not total mass are driving T cell responses in vitro, but in vivo the PM matrix and complex mixtures adsorbed to the particles, not just the OF, are contributing to the observed EAE effects. This implies that examining OF alone may not be sufficient in vivo. These data further suggest that bioavailability and metabolism of organics, especially PAHs, may have an important role in vivo.

     

Mangrove Oyster (Crassostrea belcheri) as a Biomonitor Species for Bioavailability of Polycyclic Aromatic Hydrocarbons (PAHs) from Sediment of the West Coast of Peninsular Malaysia

ABSTRACT

Rapid industrialization and urbanization in the west coast of Peninsular Malaysia has caused increasing pollution particularly of petroleum and petroleum by-products. Surface sediment and mangrove oyster (Crassostrea belcheri) were collected from five mangrove ecosystems in the west coast of Peninsular Malaysia and investigated for bioavailability of polycyclic aromatic hydrocarbons (PAHs). Sampling locations were selected from both remote areas with few or no previous records of petroleum pollution such as Pulau Merambong and polluted areas that are under international attention such as Klang mangrove ecosystem. PAH fractions were obtained through soxhlet extraction and two-step column chromatography and the fractions were injected to gas chromatography-mass spectrometry (GC-MS) for analysis. The concentrations of PAHs ranged from 151 to 4973 ng g^?1 dw in the sediments, while from 309 to 2225 ng g^?1 dw in the oysters. When tested for diagnostic ratios, a predominance of pyrogenic source PAHs was detected in the sediments, whereas PAHs in the oysters had mixed petrogenic and pyrogenic sources. A significant correlation (p < 0.05) was found between high molecular weight (HMW) PAHs in the sediments and oysters and biota accumulation factors (BAFs) of PAHs were approaching or exceeding unity indicating the ability of mangrove oyster in bioaccumulation of PAHs. Overall, this study indicates that mangrove oyster (C. belcheri) can be used as a biomonitor species for PAHs in an aquatic environment.     

Polycyclic Aromatic Hydrocarbons in Sediments of Marine Coastal Lagoons in Messina,Italy: Extraction and GC/MS Analysis,Distribution and Sources

The content of 21 polycyclic aromatic hydrocarbons (PAHs) were determined in 16 samples of sediments collected from Ganzirri and Faro marine coastal lagoons in Messina, Italy. Analysis was performed by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring (SIM) mode. The total concentration of polycyclic aromatic hydrocarbons (ΣPAHs) ranged from 74 to 5755 μg/kg of dry matrix. The resulting distributions and molecular ratios of specific compounds are discussed in terms of sampling location and origin of organic matter. The results obtained show that levels of contamination are not homogeneous throughout the stations, while the relative distributions of PAHs are homogeneous in most of the sampling stations. The organic matter content and PAH concentration were found to be correlated (r = 0.90). It is also shown that the pyrolytic origin is the main source of these compounds in Ganzirri and Faro Lakes sediments.     

Isolation,Screening, and Characterization of Naphthalene-Degrading Bacteria from Zarand Mine,Iran

ABSTRACT

PAHs are aromatic hydrocarbons with two or more fused benzene rings. They are formed during the thermal breakdown of organic molecules and their succeeding recombination. Naphthalene is the simplest (PAHs) that is carcinogenic. Bioremediation method is considered as an economical and safe approach for the elimination of aromatic compounds from environment. The bacteria were capable to grow on various hydrocarbons like naphthalene. The aim of this research is to isolate and identify naphthalene-degrading bacteria from the coal mine of Zarand. Four samples of water and sludge from various sites of the mine were collected. These sites include the following: Main coal vacate site (MC), Inoculum Sump site (IB), Sludge aggregate site (SA), and Near sludge aggregate site (NF). In this study, 12 bacterial strains that utilize naphthalene at initial concentration 200 mg/L (ppm) as carbon and energy sources for growth were isolated from the Zarand mine in Iran. In addition, bacterial cell density was assayed by measuring the OD₆₀₀. In addition, total naphthalene-degrading bacteria were quantified with the most probable number (MPN) procedure using microtiter plates and the colony-forming unit (CFU) method. The results had shown that most of the naphthalene degrader bacteria aggregated in (SA) site. Six bacteria, isolated from wastewater and oil-contaminated soil showed great potential as naphthalene degraders up to 400 (ppm) and selected for biochemical characteristics. Naphthalene tolerance of the strains in various concentrations of naphthalene indicates that the strain 38 N can grow best at 600 (ppm) naphthalene. This strain was identified based on 16S rRNA gene analysis that showed belonging to Sphingobacterium multivorum AHB38N.     

Separation of polyaromatic hydrocarbons from contaminated soils using microwave heating

The microwave treatment of soils contaminated with heavy- and light-hydrocarbons was investigated. The soils were characterised to determine the total organic liquid content and PAH contents, and the dielectric properties of the soils were measured across a range of temperatures. The heavy- and light-contaminated soils behaved very differently in a microwave environment, with bulk soil temperatures limited to 100 °C for the light-contaminated soil. Microwave treatment is shown to remove PAHs from both the heavy- and light-contaminated soils, and it is demonstrated that 95%+ PAH removal can be achieved under moderate processing conditions. Complete remediation of the soils is possible at high microwave powers or long residence times. It is shown that PAH removal can take place at bulk temperatures well below the boiling point of those compounds and a number of explanations are proposed for this behaviour. The mechanisms of PAH removal are investigated for both the heavy- and light-contaminated soils and thermal desorption, selective heating and entrainment mechanisms can all be exploited.This is the first step in the development of a continuous microwave treatment process for the removal of PAHs from contaminated soil on an industrial scale.     

Catalytic oxidation of naphthalene using a Pt/Al2O3 catalyst

Polycylic aromatic hydrocarbons (PAHs) are listed as carcinogenic and mutagenic priority pollutants, belonging to the environmental endocrine disrupters. Most PAHs in the environment stem from the atmospheric deposition and diesel emission. Consequently, the elimination of PAHs in the off-gases is one of the priority and emerging challenges. Catalytic oxidation has been widely used in the destruction of organic compounds due to its high efficiency (or conversion of reactants), its economic benefits and good applicability.

This study investigates the application of the catalytic oxidation using Pt/γ-Al₂O₃ catalysts to decompose PAHs and taking naphthalene (the simplest and least toxic PAH) as a target compound. It studies the relationships between conversion, operating parameters and relevant factors such as treatment temperatures, catalyst sizes and space velocities. Also, a related reaction kinetic expression is proposed to provide a simplified expression of the relevant kinetic parameters.

The results indicate that the Pt/γ-Al₂O₃ catalyst used accelerates the reaction rate of the decomposition of naphthalene and decreases the reaction temperature. A high conversion (over 95%) can be achieved at a moderate reaction temperature of 480 K and space velocity below 35,000 h⁻¹. Non-catalytic (thermal) oxidation achieves the same conversion at a temperature beyond 1000 K. The results also indicate that Rideal–Eley mechanism and Arrhenius equation can be reasonably applied to describe the data by using the pseudo-first-order reaction kinetic equation with activation energy of 149.97 kJ/mol and frequency factor equal to 3.26 × 10¹⁷ s⁻¹.     

Characterization of Culturable PAH and BTEX Degrading Bacteria from Heavy Oil of the Rancho La Brea Tarpits

Novel petroleum degrading bacteria have been identified in heavy oil from natural asphalt seeps using DNA-based methods, but there is little knowledge of the extent to which these bacteria can be cultured by selective enrichments on different aromatic hydrocarbons. Here we report the species composition of bacterial communities from a 40,000 yr-old asphalt deposit that could be grown on selected petroleum compounds. Species compositions of the degrader communities determined by PCR-DGGE and 16S rDNA sequencing showed that selective enrichment using (PAHs) and BTEX (benzene, toluene, ethyl benzene, and xylene) as growth substrates produced relatively simple degrader communities, and included a predominant species, Pseudomonas stutzeri, which grew on multiple compounds. PCR-based techniques further identified genes encoding naphthalene dioxygenase and catechol 2,3-dioxygenase from P. stutzeri in the enrichment cultures. The results suggest that only a small portion of the asphalt-inhabiting community can be cultured under aerobic conditions on individual substrates. Within these communities were several new species that merit further characterization as consortia, as well as new isolates of the cosmopolitan degrader, P. stutzeri.