Contamination of polycyclic aromatic hydrocarbons (PAHs) in microlayer and subsurface waters along Alexandria coast,Egypt

The residues of seven polycyclic aromatic hydrocarbons (PAHs) pollutants in microlayer and subsurface seawater samples collected from Alexandria coast, Egypt, were analyzed by gas chromatography–electron-impact mass spectrometry-selected ion monitoring mode (GC–MS-SIM). The pollutants studied were, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene and benzo[a]pyrene. Total PAH levels in microlayer ranged from 103 to 523 ng/l, while it ranged in subsurface samples from 13 to 120 ng/l. The Western Harbor location recorded the highest level of PAHs pollutant over all the other location for both subsurface and microlayer waters. The two major PAHs in microlayer water at the Western Harbor were fluorene and phenanthrene, making up 27% and 20% of the total PAHs, while the two major PAHs in subsurface water at the Eastern Harbor were phenanthrene and fluoranthene recording up 21% each of the total PAHs. The total PAH levels were generally in the nano-gram per liter for microlayer and subsurface seawater samples. The dominant PAHs in both subsurface and microlayer samples were fluoranthene, pyrene and benzo[a]pyrene. The microlayer enrichment factor at Alexandria’s Mediterranean coast was ranged from 29 for fluorene to 3 for phenanthrene and benzo[a]pyrene which showed PAHs concentration in the microlayer with an average of five times more than the total PAH in the subsurface samples.     

采油废水中多环芳烃的生态风险评价

先利用C-18固相萃取小柱富集大港油田港东联合处理站污水处理站的采油废水中16种多环芳烃(PAHs,即萘、苊烯、苊、芴、菲、蒽、荧蒽、芘、、苯并[a]蒽、苯并[b]荧蒽、苯并[k]荧蒽、苯并[a]芘、茚并[1,2,3-cd]芘、二苯并[a,h]蒽和苯并[g,h,i]苝),再用气相色谱/质谱(GC/MS)分析测定其浓度,以评价PAHs的去除率和生态风险。结果表明:(1)采油废水经处理后,COD、石油类去除率分别达到82.27%、91.06%;外排水COD、石油类达到《污水综合排放标准》(GB 8978—1996)一级标准要求,优于中国采油废水处理的一般水平。(2)采油废水主要以2、3环的PAHs为主,约占总量的93%以上。(3)苯并[a]芘超过《地表水环境质量标准》(GB 3838—2002)中限值。(4)处理前的采油废水中蒽、菲和苯并[a]芘具有一定的生态风险;处理后的外排水中萘、蒽、菲、荧蒽、苯并[a]芘的暴露浓度(PEC)/预测无效应浓度(PNEC)均小于1,目前尚未对环境造成威胁。但是8种PAHs(苊烯和苯并类PAHs除外)总和表现出较大的毒性,需要引起重视。     

Combined UV-biological degradation of PAHs

The UV-photolysis of PAHs was tested in silicone oil and tetradecane. In most cases, the degradation of a pollutant provided within a mixture was lower than when provided alone due to competitive effects. With the exception of anthracene, the larger pollutants (4- and 5-rings) were always degraded first, proving that UV-treatment preferentially acts on large PAHs and thereby provides a good complement to microbial degradation. UV-photolysis was also found to be suitable for treatment of soil extract from contaminated soils. The feasibility of UV-biological treatment was demonstrated for the removal of a mixture of phenanthrene and pyrene in silicone oil. UV-irradiation of the silicone oil led to 83% pyrene removal but no phenanthrene photodegradation. Subsequent treatment of the oil in a two-phases partitioning bioreactor (TPPB) system inoculated with Pseudomonas sp. was followed by complete phenanthrene biodegradation but no further pyrene removal. Totally, the combined process allowed 92% removal of the PAH mixture. Further work should focus on characterizing the photoproducts formed and studying the influence of the solvent on the photodegradation process.     

Eisenia fetida increased removal of polycyclic aromatic hydrocarbons from soil

The removal of phenanthrene, anthracene and benzo(a)pyrene added at three different concentrations was investigated with or without earthworms (Eisenia fetida) within 11 weeks. Average anthracene removal by the autochthonous micro-organisms was 23%, 77% for phenanthrene and 13% for benzo(a)pyrene, while it was 51% for anthracene, 47% for benzo(a)pyrene and 100% for phenanthrene in soil with earthworms. At 50 and 100mg phenanthrene kg(-1)E. fetida survival was 91% and 83%, but at 150 mg kg(-1) all died within 15 days. Survival of E. fetida in soil amended with anthracene < or = 1000 mg kg(-1) and benzo(a)pyrene < or = 150 mg kg(-1) was higher than 80% and without weight loss compared to the untreated soil. Only small amounts of PAHs were detected in the earthworms. It was concluded that E. fetida has the potential to remove large amounts of PAHs from soil, but more work is necessary to elucidate the mechanisms involved.     

Treatment of PAHs in contaminated soil by extraction with aqueous DNA followed by biodegradation with a pure culture of Sphingomonas sp

The biodegradation of polycyclic aromatic hydrocarbons (PAHs) in aqueous deoxyribonucleic acid (DNA) solution from contaminated soil washing was investigated. Initial data with a model effluent consisting of anthracene, phenanthrene, pyrene and benzo[a]pyrene that were individually dissolved in 1% aqueous DNA solution confirmed their positive degradation by Sphingomonas sp. at around 10(8)CFU mL(-1) initial cell loading. For anthracene and phenanthrene, complete removal was achieved within 1h treatment. Degradation of pyrene and benzo[a]pyrene took a relatively longer time of a few days and weeks, respectively. DNA-dissolved PAHs were also degraded relatively faster than PAH crystals in aqueous medium to suggest that the binding of the PAHs in the polymer does not pose serious constraint to bacterial uptake. The DNA was stable against the PAH-degrading bacteria. Parallel experiments with actual DNA solutions obtained during pyrene extraction from an artificially spiked soil also showed similar results. Close to 100% pyrene degradation was achieved after 1d treatment. With its chemical stability, the cell-treated DNA was re-used up to four cycles without a considerable decline in extraction performance.     

Dissipation of polycyclic aromatic hydrocarbons from soil added with manure or vermicompost

The dissipation of three PAHs, i.e., 500 mg phenanthrene kg(-1) soil, 350 mg anthracene kg(-1) soil and 150 mg benzo(a)pyrene kg(-1) soil, was investigated in soil from Acolman (México) added with cow manure or vermicompost while production of CO(2) and inorganic N was monitored. At day 0, recovery of added phenanthrene was 95%, anthracene 96% and benzo(a)pyrene 100% in sterilized soil and concentrations did not change significantly in sterilized soil over time. Application of organic material did not affect the concentration of phenanthrene and anthracene, which decreased sharply in the unsterilized soil in the first weeks of the incubation. Less than 3% of the added phenanthrene was detected after 100 days and less than 8.5% of the added anthracene (mean of the two experiments). The decrease in concentration of benzo(a)pyrene (BaP) was not fast as that of phenathrene and anthracene, and 22% was extractable from soil still after 100days. It was concluded that addition of farm yard manure (FYM) and vermicompost only had an effect on the initial dissipation of phenanthrene, anthracene and benzo(a)pyrene in soil of Acolman.     

Quantification and characterization of vehicle-based polycyclic aromatic hydrocarbons (PAHs) in street dust from the Tamale metropolis,Ghana

Objective

Concentrations of polycyclic aromatic hydrocarbons (PAHs) in street dust in the Tamale metropolis, Ghana, have been measured in this study.

Results

The concentrations of the various types of PAHs identified in street dust samples from high vehicular traffic density in the metropolis are as follows: naphthalene, 10,000 μg/kg; acenaphthylene, 13,000 μg/kg; acenaphthene, 76,000 μg/kg; fluorene, 18,900 μg/kg; phenanthrene, 40,000 μg/kg; anthracene, 21,000 μg/kg; fluoranthene, 35,200 μg/kg; pyrene, 119,000 μg/kg; benzo[a]anthracene, 17,700 μg/kg; chrysene, 10,600 μg/kg; benzo[k]fluoranthene, 18,700 μg/kg; benzo[a]pyrene, 10,900 μg/kg and benzo[g, h, i]perylene, 21,000 μg/kg. Calculation of the phenanthrene/anthracene ratio indicated that the PAHs identified in this study were from vehicular fallout as the ratio was less than 10.

Conclusion

It is clear from the results of the study that road users in the Tamale metropolis, especially hawkers, are exposed to the harmful effects of PAHs, and this suggests the need for the establishment of mitigation measures by the regulatory agencies.

     

Biodegradation of polycyclic aromatic hydrocarbons by a mixed culture

We investigated the potential biodegradation of polycyclic aromatic hydrocarbons (PAHs) by an aerobic mixed culture utilizing phenanthrene as its carbon source. Following a 3-5 h post-treatment lag phase, complete degradation of 5 mg/l phenanthrene occurred within 28 h (optimal conditions determined as 30 degrees C and pH 7.0). Phenanthrene degradation was enhanced by the individual addition of yeast extract, acetate, glucose or pyruvate. Results show that the higher the phenanthrene concentration, the slower the degradation rate. While the mixed culture was also capable of efficiently degrading pyrene and acenaphthene, it failed to degrade anthracene and fluorene. In samples containing a mixture of the five PAHs, treatment with the aerobic culture increased degradation rates for fluorene and anthracene and decreased degradation rates for acenaphthene, phenanthrene and pyrene. Finally, it was observed that when nonionic surfactants were present at levels above critical micelle concentrations (CMCs), phenanthrene degradation was completely inhibited by the addition of Brij 30 and Brij 35, and delayed by the addition of Triton X100 and Triton N101.     

Successful Treatment of Low PAH-Contaminated Sewage Sludge in Aerobic Bioreactors (7 pp) *

Background, Aims and Scope Polycyclic Aromatic Hydrocarbons (PAHs) are known for their adverse and cumulative effects at low concentration. In particular, the PAHs accumulate in sewage sludge during wastewater treatment, and may thereafter contaminate agricultural soils by spreading sludge on land. Therefore, sludge treatment processes constitute the unique opportunity of PAH removal before their release in the environment. In this study, the ability of aerobic microorganisms to degrade light and heavy PAHs was investigated in continuous bioreactors treating trace-level PAH-contaminated sludge. Methods Several aerobic reactors were operated under continuous and perfectly mixed conditions to simulate actual aerobic sludge digesters. Three sterile control reactors were performed at 35°C, 45°C or 55°C to assess PAH abiotic losses under mesophilic and thermophilic conditions. Three biological reactors were also operated at 35°C, 45°C or 55°C. Furthermore, 250 mM methanol were added in an additional mesophilic reactor (35°C). All reactors were fed with long-term PAH-contaminated sewage sludge, and PAH removal was assessed by inlet/outlet mass balance. In this study, PAH compounds ranged from 2 to 5-unsubstituted aromatic rings, i.e. respectively from Fluorene to Indeno(123cd)pyrene. Results and Discussion Significant abiotic losses were observed for the lightest PAHs (fluorene, phenanthrene and anthracene), while biodegradation occurred for all PAHs. More than 80% of the lightest PAHs were removed. Biodegradation rates inversely correlated with the increasing molecular weight, and seemed limited by the low bioavailability of the heaviest PAHs (only 50% of removal). The enhancement of PAH bioavailability by increasing the process temperature or adding methanol was tested. A temperature increase from 35°C to 45°C and then to 55°C significantly enhanced the biodegradation of the heaviest PAHs from 50% to 80%. However, high abiotic losses were observed for all PAHs at 55°C, which was attributed to volatilization. Optimal conditions were found at 45°C considering the low abiotic losses and the high PAH biodegradation rates. Similar performances were achieved by addition of methanol in the sludge. It was concluded that increasing temperatures or addition of methanol favored PAH diffusion from solids to an aqueous compartment, and enhanced their bioavailability to PAH-degrading microorganisms. Conclusion In this study, the use of long-term acclimated aerobic ecosystems showed the high potential of aerobic microorganisms to degrade a wide range of PAHs at trace levels. However, PAH biodegradation was likely controlled by their low bioavailability. Two aerobic processes have been finally proposed to achieve efficient decontamination of sewage sludge, at 45°C or in the presence of methanol. The PAH concentrations in reactor outlet were lower than the French requirements, and allow the treated sludge to be spread on agricultural land. Recommendations and Outlook The two proposed aerobic processes used physical or chemical diffusing agents. The global ecological impact of using the latter agents for treating trace level contamination must be considered. Since methanol was completely removed during the process, no additional harm is expected after treatment. However, an increase of temperature to 45°C could drastically increase the energy demand in full-scale plants, and therefore the ecological impact of the process. Moreover, since bioavailability controls PAH biodegradation, efficiency of the processes could also be influenced by the hydraulic parameters, such as mixing and aeration rates. Further experimentations in a pilot scale are therefore recommended, as well as a final assessment of the global environmental benefit of using such aerobic processes in the bioremediation of trace level compounds. - Abbreviations (PAHs): Ant – anthracene; B(a)A – benzo(a)anthracene ; B(b)F – benzo(b)fluoranthene; B(k)F – benzo(k)fluoranthene; B(ghi)P – benzo(g,h,i)perylene; B(a)P – benzo(a)pyrene; Chrys – chrysene; DB – dibenzo(a,h)anthracene; Fluor – fluoranthene; Fluo - fluorene; Ind – indeno(1,2,3-c,d)pyrene; Phe - phenanthrene; Pyr – pyrene - * The basis of this peer-reviewed paper is a presentation at the 9th FECS Conference on 'Chemistry and Environment', 29 August to 1 September 2004, Bordeaux, France.     

Removal of PAHs from water using an immature coal (leonardite)

It has been studied an immature coal (leonardite) as an adsorbent for removing PAHs [fluorene, pyrene, benzo(k)fluoranthene, benzo(a)pyrene and benzo(g,h,i)perylene] from water. To determine the efficiency of leonardite as an adsorbent of PAHs, factors such as pH, contact time and equilibrium sorption were evaluated in a series of batch experiments. There were no significant differences in the removal percentages for the various pH values studied, except for fluorene. The adsorption of fluorene was higher at lower pH values. The equilibrium time was reached at 24h. At this time, more than 82% of the pyrene, benzo(k)fluoranthene, benzo(a)pyrene and benzo(g,h,i)perylene had been removed. During the first 2h, the adsorption rate increased rapidly. After that time, however, there was a minor decrease. Equilibrium data were fitted to Freundlich models to determine the water-leonardite partitioning coefficient. Physical adsorption caused by the aromatic nature of the compounds was the main mechanism that governed the removal process. The polarity of the humic substances in leonardite may also have influenced the adsorption capacity.     

GC/MS analysis of polynuclear aromatic hydrocarbons in sediment samples from the Niger Delta region

Thirteen sediment samples from different locations in the Niger Delta region of Nigeria were analyzed for the presence of 16 polynuclear aromatic hydrocarbons (PAHs) via gas chromatography/mass spectrometry. The specific target compounds for this study included naphthalene, acenaphthylene, acenaphthene, flourene, phenanthrene, anthracene, flouranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]flouranthene, benzo[a]pyrene, benzo[ghi]perylene, dibenz[a,h]anthracene, and indeno[1,2,3-cd]pyrene. Four isotopically labeled polynuclear aromatic hydrocarbons (acanaphthene-d10, phenanthrene-d10, chrysene-d12 and perylene-d12) were used for internal standardization. All 16 PAHs were found in most of the thirteen samples with concentration ranging from 0.1 microg/kg to 28 microg/kg. It was also found that the 5 and 6-ring PAHs were present in higher concentrations than all the other compounds, indicating their high resistance to microbial degradation.     

Polycyclic aromatic hydrocarbon distribution in serum of Saudi children using HPLC-FLD: marker elevations in children with asthma

Diesel exhaust consists of a complex mixture of chemicals which contain known genotoxicants, one of which is polycyclic aromatic hydrocarbons (PAHs) which may be associated with adverse respiratory health outcomes. This study aimed to evaluate the distribution patterns of PAHs (anthracene, naphthalene, fluorene, phenanthrene, cyclopentaphenanthrene, pyrene, fluoranthene, benzanthracene, chrysene, benzo(e)pyrene, benzoacephenanthrylene, and benzo(a)pyrene) in serum collected from asthmatic and healthy control children. PAH serum levels were measured in samples collected from children who lived in 11 different locations in/round Riyadh, Saudi Arabia (Al-yarmouk, Usaibi, Sultana Al-kadema, Omrrojam, Kof, Janoob Dawdmi, Guberah, Arabbuah, Al-mozahemyah, Iskan Al-mazzer, and Al-gharabi) during the period 2010–2011. Our results showed that the highest total mean concentrations of PAH were found in serum samples collected from people who lived in Sultana Aljadhida, Almozahemyah, Guberah, and Omrrojam and were 663.9, 486.17, 412.18, and 258.6 ng ml^?1, respectively. The most prevalent PAHs in serum samples were naphthalene, bezanthracene, benzoacephenanthrylene, phenanthrene, chrysene, and benzo(a)pyrene with a frequency that ranged from 54.5 to 90.9 % positive samples. A close monitoring of PAH pollution is strongly recommended, especially in food and plant samples, because of their high bioaccumulation capacity.     

Influence of fuel composition on polycyclic aromatic hydrocarbon emissions from a fleet of in-service passenger cars

The composition of exhaust emissions from eight in-service passenger cars powered by liquefied petroleum gas (LPG) and unleaded petrol (ULP) were measured on a chassis dynamometer at two driving speeds (60 and 80 km h⁻¹) with the aims of evaluating their polycyclic aromatic hydrocarbon (PAH) contents and investigating the effects of the type of fuel on vehicle performance, ambient air quality and associated health risks. Naphthalene, fluorene, phenanthrene, anthracene, pyrene, chrysene, benzo(a)anthracene and benzo(b)fluoranthene were the most prominent PAHs emitted by both ULP and LPG powered cars. The total emission factors of PAHs from LPG cars were generally lower than (but statistically comparable with) those of ULP cars. Similarly, the total BAP_eq of the PAHs emitted by LPG cars were lower than those from ULP cars. Multi-criteria decision making (MCDM) methods showed that cars powered by LPG fuel performed better than those powered by ULP fuel in term of PAH levels. The implications of these observations on the advantages and disadvantages of using ULP and LPG fuels are discussed.     

A column method for determination of leaching of polycyclic aromatic hydrocarbons from aged contaminated soil

In this study a column leaching method for investigation of hydrophobic organic contaminants (HOCs) leaching from soil was developed. The method set-up is based on a recycled flow of sterile water through a soil column with a sedimentation chamber mounted on top of the column, in connection with on-line filtration. The combination of a sedimentation chamber and an on-line filtration enables the measurement of leaching concentrations from contaminated materials consisting of very fine particle fractions. In addition, by using on-line solid phase extraction, minute amounts of leaching HOCs may be captured and quantified with high accuracy and reproducibility. The method was applied successfully on a contaminated aged soil sample and the leaching behavior of seven PAHs, with three to six aromatic rings, was monitored for more than 1600 h under saturated conditions. The tested PAHs were fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)pyrene and benzo(ghi)perylene. The method proved to be reliable and capable of providing data on leachable amounts of the PAHs under field-like conditions and over a longer period of time. The results indicated low availability of the studied contaminants since only a minor fraction (0.3%) of the initial amount of PAHs in the soil was removed during the experiment (liquid/solid-ratio of 700 l/kg). Thus PAHs in aged contaminated soil are not to be expected to be released to any great extent only by leaching with water.     

Occurrence and assessment of polycyclic aromatic hydrocarbons in soils from vegetable fields of the Pearl River Delta, South China

Surface soil (0-20 cm) samples from nine representative vegetable fields located in Guangzhou, Shenzhen, Zengcheng and Huadu within the Pearl River Delta, South China were collected and analyzed for 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs) using gas chromatography coupled to mass spectrometry (GC-MS). Total concentrations of 16 PAHs (Sigma(PAHs)) ranged from 160 to 3700 microg kg(-1). Large variations were observed also between concentrations of individual PAHs from different vegetable fields and within the site as well. Acenapthylene, benzo[b]fluoranthene, fluoranthene, benzo[a]pyrene and benzo[k]fluoranthene were consistently the most prevalent individual PAHs. The values of PAH isomer ratios [anthracene/(anthracene+phenanthrene) and fluoranthene/(fluoranthene+pyrene)] indicate that combustion processes are the major sources of PAHs. Concentrations of PAHs were poorly correlated with organic carbon concentrations of soils, suggesting different sources and also indicating that the PAH pollution of this area is recent. The same outcome is confirmed by the predominance of PAHs with fewer rings (相似文献   

Hydrocarbon deposition and soil microflora as affected by highway traffic.

The proximity of a busy highway (90,000 vehicles/day) increased the amount of polycyclic aromatic hydrocarbons (PAHs) in soil at the depth of 5-15 cm from 106 ng/g as a grassland background to 3095 ng/g dry soil at the highway verge (a sum of 10 PAH species). The PAH concentration was related to the distance from the source and exhibited a biphasic character, which is interpreted in terms of bimodal distribution of the exhaust microparticles with different rates of deposition. Similarly, the tendency of benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, and indeno(1,2,3-cd)pyrene to decrease their proportion with distance from the highway, in contrast to phenanthrene, fluoranthene, pyrene, benzo(a)pyrene, and benzo(g,h,i)perylene, was attributed to their prevalent localisation on the heavier particle fraction. The abundance of bacteria (8.33 x background) and fungi (3.17 x background) close to the highway is thought to be a consequence of hydrocarbon deposition from the traffic that serves as a significant energetic input into the soil. The elevated concentrations of hydrocarbon substrates, as indicated by PAHs, increased both the absolute and relative numbers of the microbial degraders of diesel fuel, biphenyl, naphthalene, and pyrene. Their maximum numbers at 0.5-1.5 m from the pavement reached 1.3 x 10(4), 1.2 x 10(5), 1.1 x 10(4), and 6.6 x 10(3) colony-forming units (CFU) or infection units per gramme dry soil, respectively. On the other hand, the number of anthracene degraders (1.1 x 10(3) CFU per g dry soil) remained close to the detection limit of the enumeration technique used (0.1-0.2 x 10(3) per g dry soil), consistently with the absence of anthracene and higher linear PAHs in the investigated soil samples. The amounts of persisting PAHs justify artificial inoculation with effective degrader strains in the vicinity of motorways.     

Polycyclic aromatic hydrocarbons in marine organisms from the Adriatic Sea, Italy

Polycyclic aromatic hydrocarbons (PAHs) were analyzed in bivalves (Mitylus galloprovincialis), cephalopods (Todarodes sagittatus), crustaceans (Nephrops norvegicus) and fish (Mullus barbatus, Scomber scombrus, Micromesistius poutassou, Merluccius merluccius) in several pools coming from the Central Adriatic Sea. These marine organisms were selected because of their multitude, wide distribution and common use in the Italian diet, they were sampled and analyzed during the year 2004. Acenaphthene, benzo(a)pyrene, dibenz(a,h)anthracene, benzo(ghi)perylene and indeno(1,2,3-cd)pyrene showed levels below the instrumental detection limit in all samples. Fluorene, phenanthrene, anthracene, fluoranthene, benz(a)anthracene, benzo(b)fluoranthene and benzo(k)fluoranthene were detected at different concentrations in analyzed samples. Chrysene was detected only in mussels with very low values (average 0.74ngg(-1) wet weight). PAHs composition pattern was dominated by the presence of PAHs with 3-rings (62%) followed from those with 4-rings (37%) and 5-rings (1%). Atlantic mackerel, European hake and blue whiting showed the highest PAH concentrations, ranging from 44.1 to 63.3ngg(-1) wet weight, the group of invertebrate organisms showed a level of contamination about three times lower than those of the vertebrate groups. Mediterranean mussels that did not present very high levels of contamination expressed as sum of PAHs showed one of the highest values of benzo(a)pyrene equivalents (BaPEs). Conversely the latter value was very low in Atlantic mackerel even if this species reported the highest total PAH concentrations. No significant correlation was observed between weight, length and trophic levels and total PAHs.     

Mass balance model of source apportionment, transport and fate of PAHs in Lac Saint Louis, Quebec

A mass balance model has been developed and calibrated to describe the sources, transport and fate of seven polycyclic aromatic hydrocarbons (PAHs; anthracene, benzo(a)pyrene, benzo(b)fluoranthene, chrysene, fluoranthene, phenanthrene, and pyrene) in the water and sediments of, and atmosphere over Lac Saint Louis, Quebec. The model uses specified input rates from background advective flows and emissions from the Alcan aluminum smelting facility at Beauharnois to deduce atmospheric concentrations and rates of wet and dry deposition to the three segment lake. Concentrations in water and sediment as well as relevant mass fluxes and residence times are computed and compared satisfactorily with monitoring data for five of the seven PAHs. Underestimation of concentrations for anthracene and phenanthrene is attributed to unquantified additional sources. The sources of the PAH burden in the lake are apportioned, and the implications of these results are discussed including likely response times to changes in loadings. It is suggested that this mass balance approach is more widely applicable to situations in which water bodies are impacted by a variety of contaminant sources.     

Effect of fuel composition and engine operating conditions on polycyclic aromatic hydrocarbon emissions from a fleet of heavy-duty diesel buses

Emissions from 12 in-service heavy-duty buses powered by low- (LSD) and ultra low-sulfur (ULSD) diesel fuels were measured with the aim to characterize the profile of polycyclic aromatic hydrocarbons (PAHs) in the exhaust and to identify the effect of different types of fuels on the emissions. To mimic on-road conditions as much as possible, sampling was conducted on a chassis dynamometer at four driving modes, namely: mode 7 or idle (0% power), mode 11 (25% power), mode 10 (50% power) and mode 8 (100% power). Irrespective of the type of fuel used, naphthalene, acenaphthene, acenaphthylene, anthracene, phenanthrene, fluorene, fluoranthene and pyrene were found to be the dominant PAHs in the exhaust emissions of the buses. However, the PAH composition in the exhausts of ULSD buses were up to 91±6% less than those in the LSD buses. In particular, three- and four-ringed PAHs were more abundant in the later than in the former. Lowering of fuel sulfur content not only reduced PAH emission, but also decreased the benzo(a)pyrene equivalent (BAP_eq) and hence the toxicity of the exhaust. Result from multicriteria decision-making and multivariate data analysis techniques showed that the use of ULSD afforded cleaner exhaust compositions and emissions with characteristics that are distinct from those obtained by the use of LSD.     

Enhanced degradation of polycyclic aromatic hydrocarbons by biodegradation combined with a modified Fenton reaction

A study has been conducted to enhance degradation of a mixture of polycyclic aromatic hydrocarbons (PAHs) by combining biodegradation with hydrogen peroxide oxidation in a former manufactured gas plant (MGP) soil. An active bacterial consortium enriched from the MGP surface soil (0-2 m) biodegraded more than 90% of PAHs including 2-, 3-, and 4-ring hydrocarbons in a model soil. The consortium was also able to transform about 50% of 4- and 5-ring hydrocarbons in the MGP soil. As a chemical oxidant, Fenton's reagent (H2O2 + Fe2+) was very efficient in the destruction of a mixture of PAHs (i.e., naphthalene (NAP), fluorene (FLU), phenanthrene (PHE), anthracene (ANT), pyrene (PYR), chrysene (CHR), and benzo(a)pyrene (BaP)) in the model soil; noticeably, 84.5% and 96.7% of initial PYR and BaP were degraded, respectively. In the MGP soil, the same treatment destroyed more than 80% of 2- and 3-ring hydrocarbons and 20-40% of 4- and 5-ring compounds. However, the low pH requirement (pH 2-3) for optimum Fenton reaction made the process incompatible with biological treatment and posed potential hazards to the soil ecosystem where the reagent was used. In order to overcome such limitation, a modified Fenton-type reaction was performed at near neutral pH by using ferric ions and chelating agents such as catechol and gallic acid. By the combined treatment of the modified Fenton reaction and biodegradation, more than 98% of 2- or 3-ring hydrocarbons and between 70% and 85% of 4- or 5-ring compounds were degraded in the MGP soil, while maintaining its pH about 6-6.5.