Photochemical degradation of polycyclic aromatic hydrocarbons in oil films

Photochemical processes affect the fate of spilled oil in the environment, but the relative contribution and kinetics of these degradation pathways are not fully constrained. To address this problem, we followed the weathering of No. 6 fuel oil by periodically sampling rocks covered with a film of oil from Buzzards Bay, MA after the April 2003 Bouchard 120 oil spill. Two sets of polycyclic aromatic hydrocarbon (PAH) isomers, benzo[a]pyrene (BAP) and benzo[e]pyrene (BEP), and benz[a]anthracene (BAA) and chrysene (CHR), were found to have very different disappearance rates in spite of their close structural similarity (kBAA/kCHR approximately 2.0, kBAP/kBEP approximately 2.2). This well-documented phenomenon is suspected to arise from differing capacity for direct photoreaction in the oil film. To investigate the validity of this assumption, we developed a model to estimate the contribution of direct photolysis to the loss of these PAHs from the oil. Newly determined PAH quantum yields demonstrate that the efficiency of phototransformation in hydrophobic media are 2 orders of magnitude lower (Phi' approximately 10(-5)) than in aqueous systems, and the thickness and light-attenuating properties of the oil film reduce the potential for photoreaction by up to 2 orders of magnitude. Given these limiting factors, direct photolysis cannot account for the complete removal of these PAHs (except BAP). Additional results suggest that singlet oxygen photodegradation pathways are not favored in hydrophobic media, as they are in some mineral-associated and aqueous systems. Our results indicate that photomediated reactions with other compounds in the oil mixture were responsible for PAH photodegradation in the oil film.     

食品中多环芳烃及卤代多环芳烃的研究进展

综述了多环芳烃及卤代多环芳烃的性质、毒性及国内外食品中的污染情况和研究现状,并对目前的分析测定方法进行了介绍,希望为我国开展食品领域内多环芳烃和卤代多环芳烃的研究提供参考。     

Aqueous photodegradation of polycyclic aromatic hydrocarbons

Photodegradation of 12 polycyclic aromatic hydrocarbons was studied in aerated pure water, solutions of Suwannee River fulvic acid, and natural waters using polychromatic light (>290 nm). Quantum yields in pure water varied from 3.2 x 10(-5) to 9.2 x 10(-3). No obvious relationships were evident among the quantum yields and molecular properties. Photodegradation rate constants in solutions of Suwannee River fulvic acid or natural waters were largely unchanged compared to rate constants in pure water. Estimates of PAH photodegradation rates in natural waters can thus be obtained employing the quantum yields in pure water, PAH absorption, and solar irradiance. Calculated rate constants for photodegradation in surface waters during the summertime at mid-latitude varied from 3.2 x 10(-3) to 7.6 h(-1).     

Emission of polycyclic aromatic hydrocarbons in China

Emission of 16 polycyclic aromatic hydrocarbons (PAHs) listed as U.S. Environmental Protection Agency (U.S. EPA) priority pollutants from major sources in China were compiled. Geographical distribution and temporal change of the PAH emission, as well as emission profiles, are discussed. It was estimated that the total PAH emission in China was 25,300 tons in 2003. The emission profile featured a relatively higher portion of high molecular weight (HMW) species with carcinogenic potential due to large contributions of domestic coal and coking industry. Among various sources, biomass burning, domestic coal combustion, and coking industry contributed 60%, 20%, and 16% of the total emission, respectively. Total emission, emission density, emission intensity, and emission per capita showed geographical variations. In general, the southeastern provinces were characterized by higher emission density, while those in western and northern China featured higher emission intensity and population-normalized emission. Although energy consumption in China went up continuously during the past two decades, annual emission of PAHs fluctuated depending on the amount of domestic coal consumption, coke production, and the efficiency of energy utilization.     

Relationship between total polar components and polycyclic aromatic hydrocarbons in fried edible oil

ABSTRACT

Deep-fried dough sticks (a Chinese traditional breakfast) were fried individually in peanut, sunflower, rapeseed, rice bran, soybean and palm oil without any time lag for 32 h (64 batches fried, each for 30 min) and fried oil samples were obtained every 2 h. The frying-induced changes in the levels of total polar compounds (TPC) and polycyclic aromatic hydrocarbons (PAHs) were investigated by edible oil polar compounds (EOPC) fast separation chromatographic system and gas chromatography-mass spectrometry (GC-MS), respectively. The correlations were analysed of TPC with benzo[a]pyrene (BaP), TPC and PAH4 (benzo[a]anthracene, chrysene, benzo[b]fluoranthene and benzo[a]pyrene) as well as TPC with PAH16 (USEPA 16 PAHs). The results revealed that the levels of TPC and PAHs in fried oil considerably increased with frying time, and the type of oil affected their formation, which could inform the choice of oil for frying. The total BaP equivalents (∑BaPeq) concentrations in fresh oil and in oil whose TPC exceeded 27% were 2.14–13.48 and 5.78–10.80 μg kg^–1, respectively, which means that the carcinogenic potency of frying oil was more pronounced than that of fresh oil. In addition, the TPC concentration was significantly correlated with the concentrations of the sum of the 16 PAHs, PAH4 and BaP, so that the levels of PAHs could be predicted according to the levels of TPC in fried oil. In European standards, the rejection point for TPC in frying oil should be recalculated when considered PAHs. In all, the concentration of PAHs is a vital factor for ensuring the safety of frying oil.     

食用植物油中多环芳烃的污染情况及健康风险评价

针对食用植物油中存在多环芳烃污染和危害,采用高效液相色谱法对随机采集的75份食用植物油样本进行了16种优控多环芳烃(PAHs)含量的检测,以终生致癌风险作为评价指标,进行健康风险评价.结果表明:75份食用植物油样本中普遍存在PAHs污染,萘的污染程度最高,检出率为89.3％,平均含量为13.67 μg/kg;苊烯污染程度最小,未检出;食用植物油中轻质PAHs污染程度远高于重质PAHs;4类食用植物油中总轻质PAHs与16种优控PAHs总污染水平顺序均为:花生油＞大豆油＞玉米油＞调和油;总重质PAHs的污染水平顺序为:花生油＞玉米油＞大豆油＞调和油;食用植物油中PAHs污染具有潜在的致癌风险,其风险顺序为:花生油＞大豆油＞调和油＞玉米油.建议强化食用植物油中PAHs的控制和监管,修订相关标准,规定PAHs的最高限量值,确保食用植物油PAHs污染处在较低水平及其潜在危害处在可忽略水平.     

Occurrence of polycyclic aromatic hydrocarbons in smoked cheese

The presence of polycyclic aromatic hydrocarbons (PAH) in smoked cheeses of different origin was studied. The samples were subjected to an initial extraction of fat and an alkaline treatment, extracted with cyclohexane, cleaned up by means of solid-phase extraction tubes, and analyzed by gas chromatography/mass spectrometry (GC/MS) operating in selective ion-monitoring mode (SIM). The results revealed the presence of numerous polycyclic aromatic hydrocarbons in the exterior zone of the samples, some of them with methyl groups. In all cases, the concentrations of compounds of low molecular weight were much higher than those of high molecular weight. Polycyclic aromatic hydrocarbons with varying degrees of carcinogenicity were identified, including benzo(a)pyrene in concentrations, which, although they did not exceed the limit established for this compound in the rind of ripened cheeses, do exceed the limit of 0.03 microg/kg fixed for other foods smoked with smoke flavorings. Significant differences in the number and concentration of PAH in smoked cheese also were observed from rind to interior, the rind being the most contaminated zone.     

食用油中多环芳烃的研究进展

多环芳烃(PAHs)是指2个或2个以上苯环以稠环形式相连的一类化合物,具有基因毒性和致癌性.对食用油中PAHs的来源、检测方法及控制和脱除方法进行了详尽的阐述,并指出PAHs前处理方法和控制、脱除方法是未来的研究方向.     

浊点萃取法预浓缩食用油中多环芳烃的研究

随着食品安全意识的提高,食用油中多环芳烃的检测与分离越来越引起人们的重视,而传统液液萃取法较为繁琐,重复率也较低,因此高效的分离,富集方法研究受到关注.近年来,一种新型的基于表面活性剂相分离现象的分离方法--浊点萃取(Cloud Point Extraction,CPE),逐渐成为研究热点.与液液萃取相比,CPE具有操作简单、过程短、萃取率高等优点;此外,由于CPE过程中不使用有机溶剂,在降低成本的同时,它又是一种环境友好的萃取分离方法.通过实验各操作参数对萃取性能的影响.获得最佳操作条件,指出采用CPE方法对食用油中多环芳烃进行预浓缩的可能性.     

高脂食品中多环芳烃研究

多环芳烃具有非极性强特点,易在脂质含量丰富食品中造成污染。该文对富脂肉类等高脂肪食品中多环芳烃来源、形成及污染现状、检测方法等进行概述,并对控制其中多环芳烃污染方法进行总结和讨论。     

HPLC determination of polycyclic aromatic hydrocarbons in olive oils

 In this paper, HPLC with spectrofluorimetric detection was applied to the determination of polycyclic aromatic hydrocarbons (PAHs) in olive oils. These compounds may sometimes contaminate vegetable oils because of their specific lipophilic characteristics, which are a significant problem for their extraction and purification from lipid matrices. Some improvements to previously published methods are introduced and satisfactory results for repeatability and recovery were obtained. Data on 51 authentic olive oil samples are reported and it was found that there is usually a limited presence of PAHs in extra virgin olive oils; furthermore, the analysis of some blends of refined and virgin oils shows that the distributions of light and heavy PAHs are different with the content of the former being lower in refined samples. As an example of this fact, two samples of lampante oil were followed throughout the refining step. Received: 23 September 1996 / Revised version: 17 December 1996     

天然生育酚中痕量多环芳烃脱除工艺的研究

采用活性炭吸附法脱除天然生育酚中的多环芳烃（PAHs）,考察了脱除溶剂、活性炭种类、搅拌时间、温度、活性炭用量、脱除次数对多环芳烃脱除率的影响。结果表明,用乙醇（分析纯）溶剂溶解生育酚（液固比为5：1）,加入10％的HC-2型活性炭,在20℃下搅拌45min,对PAHs可以达到较好的脱除效果（对轻PAHs的脱除率达到48％以上,对重PAHs的脱除率达到98％以上,对总PAHs的脱除率达到88％以上）,重PAHs的残留量为5．22ng／g,轻PAHs的残留量为86．22ng／g。     

Reducing polycyclic aromatic hydrocarbons (PAHs) in olive pomace oil using short-path molecular distillation

ABSTRACT

Bleached olive pomace oil (BOPO) was distilled using a short-path molecular distillation unit to determine the impacts of distillation conditions on the removal of 15 PAHs from the list of 16 EPA-priority pollutant PAHs. The removal of PAHs was achieved at elevated temperatures (110–230°C) and pressures (0.05, 0.5, 5 mbar). The oil was also deodorised at 230°C under 0.5, 1 and 5 mbar pressures to determine the effect of pressure during deodorisation on the removal of PAHs. High-performance liquid chromatography (HPLC) with fluorescence detector (HPLC-FLD) was used for quantifying PAH concentrations in oil samples. PAH concentrations in BOPO were considerably reduced after molecular distillation and both temperature increment and pressure decrease were effective for the removal of PAHs from olive pomace oil. When above 190°C, BaP could be reduced to <2 µg/kg at all pressures. Distillation at 230°C under 0.05 mbar absolute pressure reduced the sum of four PAHs (BaP, Chr, BaA, BbF) to 7 µg/kg, which meets the acceptable levels established by the European Union (10 µg/kg). Deodorisation effectiveness was increased by decreasing absolute pressure, particularly for light PAHs.     

Emission of polycyclic aromatic hydrocarbons in China by county

Quantitative relationships among social, economic, and climate parameters, and energy consumption for Chinese provinces, provide data for regression models' estimated rates of energy consumption and emission of polycyclic aromatic hydrocarbons (PAHs) by county. A nonlinear model was used for domestic coal combustion with total population and annual mean temperature as independent variables. Linear regression models were utilized for all other types of fuel consumption. Monte Carlo simulation demonstrated that emission factors, rather than the regression modeling, constitute the main source of uncertainty in prediction. Models were validated using available energy data of several northern and southern counties of China from the literature. The total PAHs produced by each county is approximately equivalent to the sum of the total emission from energy, coke, and aluminum production.     

Modeling photoinduced algal toxicity of polycyclic aromatic hydrocarbons

The influence of light conditions on the toxicity of polycyclic aromatic hydrocarbons (PAHs) to different organisms has long been recognized. The aim of this study was to investigate whether previously proposed models can be used to qualitatively and quantitatively predict photoinduced toxicity to the green algae Scenedesmus vacuolatus. For this purpose 14 different PAH compounds were tested under three different light conditions for their effects on the algae reproduction. Illumination conditions comprised standard algae growth light, simulated sunlight aiming to mimic environmental light conditions, and UV-filtered light in order to minimize light influence on PAH toxicity. Models proposed for the prediction of photoinduced toxicity were modified in order to account for different exposure conditions and toxic endpoints used in the bioassay. The results of this study show that the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) proposed as an indication for photoinduced toxicity to Daphnia magna can be used as a qualitative indication of a potential photoinduced toxicity to the green algae Scenedesmus vacuolatus. The impact of light conditions on PAH toxicity can be quantified by a linear model which allows the estimation of the ED50 of each compound from the amount of absorbed photons and an empirically determined relative phototoxic efficacy value of the compound.