Parent Polycyclic Aromatic Hydrocarbons Research Articles

Sedimentary spatial variation, source identification and ecological risk assessment of parent, nitrated and oxygenated polycyclic aromatic hydrocarbons in a large shallow lake in China

Because polycyclic aromatic compounds (PACs) are persistent, universal, and toxic pollutants, understanding the potential source and ecological risk thereof in lakes is critical to the safety of the aquatic environment. Here, a total of 25 sedimentary samples were collected from Lake Taihu, China, in 2018. The total concentrations of 16 parent polycyclic aromatic hydrocarbons (PAHs), 15 nitrated PAHs (NPAHs), nine oxygenated PAHs (OPAHs), and five hydroxy-PAHs (OH-PAHs) ranged from 294 to 1243, 3.0 to 54.5, 188 to 1897, and 8.3 to 51.7 ng/g dw, with the most abundant compounds being fluoranthene, 1,8-dinitropyrene, 6H-Benzo[cd]pyren-6-one, and 2-phenylphenol, respectively. The spatial distribution of PACs in sediments of Lake Taihu showed elevated concentrations from east to west due to economic development and transportation. The positive correlations between most paired PAHs indicate that these compounds likely originated from similar sources. The total organic carbon and organic matter contents affected the distribution characteristics of PACs in sediments. Diagnostic ratios, principal component analysis-multiple linear regression (PCA-MLR), and positive matrix factorization (PMF) were integrated to identify the sources. PACs had various sources including combustion, petroleum leakage, traffic emissions, hydroxyl metabolism, and other oxidation pathways in sediments of Lake Taihu. The PMF (R2 > 0.9824), which showed better optimal performance compared with PCA-MLR (R2 > 0.9564) for PAHs and derivatives, is recommended as the preferred model for quantitative source analysis. Ecological risk assessment showed that the risk quotient values of OPAHs in sediments were much higher than those of other PACs and should be given special attention.

Rapid Determination of Oxygenated and Parent Polycyclic Aromatic Hydrocarbons in Milk Using Supercritical Fluid Chromatography-Mass Spectrometry.

Liquid milks are consumed worldwide in large amounts, especially by adolescents and infants. Thus, their health quality linked with polycyclic aromatic hydrocarbon (PAH) contamination has attracted great concern. This study developed a rapid and sensitive supercritical fluid chromatography (SFC)-MS method to determine two typical oxygenated PAHs (OPAHs) and EU 15+1PAHs except for benzo[k]fluoranthene (BkF) in three types of liquid milks: 10 ultra heat treated (UHT) milks, 8 pasteurized milks, and 4 extended-shelf-life pasteurized milks. The instrumental analysis was 15 min with a recovery of 67.66-118.46%, a precision of 1.45-14.68%, detection limits of 0.04-0.24 μg/kg, and quantification limits of 0.13-0.78 μg/kg. We found 9-fluorenone, anthraquinone, 15 EU priority PAHs, and benzo[a]pyrene toxic equivalent quantity (BaPeq) in the 22 milk samples, which were 0.32-1.56 μg/kg, 0.40-1.74 μg/kg, 0.57-8.48 μg/kg, and 0.01-17.42 μg/kg, respectively. The UHT milks and whole fat milks showed higher PAH concentrations than other investigated samples, where the maximum levels of BaP and PAH4 were 0.77 and 3.61 μg/kg, respectively. PAH4 dominantly contributed to the PAH8 concentration and was detected in 73% and 32% of samples at more than 1.0 and 2.0 μg/kg, respectively. The results suggest that raw milks should be strictly monitored and extensively investigated for PAH4 and BaP concentrations for future risk assessment, limitations, and dietary guidance.

Important But Overlooked Potential Risks of Substituted Polycyclic Aromatic Hydrocarbon: Looking Below the Tip of the Iceberg

Substituted polycyclic aromatic hydrocarbons (PAHs) are PAH derivatives in which substituents replace hydrogen atoms on the aromatic benzene ring, or N/S/O atoms replace carbon atoms in aromatic rings. Compared to unsubstituted PAHs, some substituted PAHs have higher pollution levels and more significant toxicity than their parent PAHs (p-PAHs), and the International Agency for Research on Cancer (IARC) lists them as possible human carcinogens, which harm human health but lack sufficient examination. This paper summarizes and discusses the environmental occurrence and distribution, toxicity, and impacts of substituted PAHs on human health and compares with the 16 representative priority-controlled PAHs (PAHs16). According to occurrence of PAHs in various environmental media, it is shown that the mean concentration of individual substituted PAH in the air is higher than that of individual PAH16. The mean concentration of individual substituted PAH in the soil varies widely among different countries, with a difference of 100,000 times between the lowest level (Italy) and the highest level (USA). The mean individual alkylated PAH (APAHs) and oxygenated PAH (OPAHs) are the most abundant in surface water and sediments. In the aspect of toxicity effects, some substituted PAHs have been proved to have similar or identical toxicity as PAHs16. We summarize existing problems and propose future priority research areas through the analysis of the occurrence and toxicity of substituted PAHs in the environment, which is important for further research and regulation of substituted PAHs.Graphical Abstract

Nitrated-, oxygenated- and parent polycyclic aromatic hydrocarbons in organic film on ferries in huangpu river (Shanghai) and source indications of ship-stack emission

Contamination information are desired to fill the gap in the understanding of environmental effects by parent-, nitrated- and oxygenated PAHs (p, n, o-PAHs) from ship stacks. In this study, the organic films on ferries along Huangpu River, one of the busiest inland rivers around the world, were measured seasonally and the compartmental concentrations were rebuilt through a fugacity model to this end. Results revealed that considerable levels of p, n, o-PAHs could be detected in the ferry films. Few seasonal or spatial variations were observed, which indicated a dominant emitter existing in the environments along the river. The compositions of p, n, o-PAHs could be associated with internal combustion engine emissions, however, the composition was different to contamination patterns of on-road traffics. Accordingly, the ship-stack exhausts were suggested to be the primary contributor of p, n, o-PAHs in ferry films. The results of PCA and PMF showed that InP and BghiP could represent the ship-stack PAHs along Huangpu River. Our study highlights a dramatic contribution of ship activities to the contaminations along Huangpu River and provides supports for the usage of organic films on ships as a representative ‘sampler’ of ship-stack emissions.

Deposition effect of inhaled particles in the human: Accurate health risks of personal exposure to PAHs and their derivatives from residential solid fuel combustion

The drastic household clean heating renovation has been undertaken in rural northern China since 2017. A method incorporating the deposition efficiency of particulate matters (PMs) in the human respiratory tract is firstly introduced into the personal exposure (PE) study which is more accurately assess the health risks of homemakers inhaling PM-bound four subclasses polycyclic aromatic hydrocarbons (PAHs) emitted from different solid fuels (i.e., biomass, raw coal chunk, and clean coal). Homemakers using clean coal show the lowest exposure levels of all PAH subclasses (parent, alkylated, oxygenated, and nitro PAHs) and total quantified PAHs (ΣPAHs). Remarkable reductions of 93.9% and 89.0% on ΣPAHs in PE PM2.5 are observed with the substitutions of the raw coal chunk and biomass fuel by the clean coal, respectively. 86.8–96.8% of ΣPAHs are inhaled by the human body, while approximately 22.4–44.8% are deposited in the respiratory tract. The deposition concentrations (DC) of ΣPAHs in the biomass and raw coal chunk groups are 12 and 5 times the clean coal group, respectively. PAHs in coarse mode PE particles with an aerodynamic size between 2.5 and 100 μm mostly deposit in the head airway (HA) (98%). Moreover, the PAHs in fine particles (i.e., with aerodynamic size less than 2.5 μm) mainly deposit in the alveolar region (AR), accounting for 20–70% of ΣPAHs. Replacing biomass and raw coal chunk with clean coal reduced incremental lifetime cancer risks (ILCR) by 91% and 92%, respectively. This study improves the understanding of the PM-bound PAHs deposition in the human respiratory system and contributes to the promotion of domestic energy transition in rural northern China.

Health Risk Assessment of Inhalation Exposure to Airborne Particle-Bound Nitrated Polycyclic Aromatic Hydrocarbons in Urban and Suburban Areas of South China.

Airborne particulates (PM2.5 and TSP) were collected from outdoor and indoor areas at urban (Haizhu District) and suburban (Huadu District) sites from 2019 to 2020 in Guangzhou. Three nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) in the airborne particulates were identified by a gas chromatograph equipped with a triple-quadrupole mass spectrometer. In the Haizhu District and Huadu District, the nitro-PAH concentrations in PM2.5 and TSP did not show a significant decrease from winter to summer. From 2019 to 2020, the difference in the average concentration of nitro-PAHs in PM2.5 and TSP in Guangzhou was relatively low and had no statistical significance. The diagnostic ratios of 2-nitrofluorene (2-NF)/1-nitropyrene (1-NP) in TSP are less than five, while for 2-NF/1-NP in outdoor PM2.5 in the summer of 2019 and 2020 are more than five, which indicates that nitro-PAHs in the atmospheric PM2.5 in Guangzhou during summer mainly originated from the secondary formation of atmospheric photochemical reactions between parent PAHs and oxidants (·OH, NO3, and O3). 9-Nitroanthracene (9-NT) made the most significant contribution to the total nitro-PAH concentration. The incremental lifetime cancer risks (ILCRs) of nitro-PAHs in PM2.5 and TSP by inhalation exposure indicated low potential health risks in the urban-suburban of Guangzhou.

Study of vibrational spectra of polycyclic aromatic hydrocarbons with phenyl side group

Computational study of polycyclic aromatic hydrocarbons (PAHs) with phenyl side group substituted at different positions is reported. The infrared spectral variations due to the position of phenyl substitution, ionization state and the size of the molecules are discussed and possible contribution of phenyl-PAHs to the mid-infrared emission features from astrophysical objects is analysed. Structurally phenyl group substitution at 2nd position gives more stable species compared to substitution at other positions. Phenyl-PAHs exhibit new aromatic bands near 695 and 741 cm−1 (14.4 and 13.5μm), due to contribution from quintet CH wag, that compare well with minor features at 14.2 and 13.5μm observed in several astrophysical objects. Just as in plain PAHs, the C–C stretch vibrational modes (∼1600 cm−1) have negligible intensity in neutrals, but the cations of all phenyl-PAHs exhibit significantly strong phenyl group C–C stretch peak close to class B type 6.2μm astrophysical band. In 2-phenylpyrene, it is the neutral molecule that exhibits this strong feature in the 6.2μm range along with other features that match with sub-features at 6.66 and 6.9μm, observed in astronomical spectra of some late type objects. The substitution of phenyl side group at solo position shifts the C–C stretch mode of parent PAH close to the region of 6.2μm astrophysical band. The results indicate possibility of phenyl-PAHs in space and the bottom-up formation of medium sized compact PAHs with phenyl side group in carbon rich cool circumstellar shells. Phenyl-PAHs need to be considered in modelling mid-infrared emission spectra of various astrophysical objects.

Recent Research Progress on Nitropolycyclic Aromatic Hydrocarbons in Outdoor and Indoor Environments

Nitropolycyclic aromatic hydrocarbons (NPAHs) are derivatives of PAHs and contain one or more nitro functional groups (-NO2). Some NPAHs are classified as possible or probable human carcinogens and are more mutagenic than PAHs. Although the atmospheric cancer risk is estimated as 11% from PAHs but 17% from NPAHs, many of the atmospheric behaviors of NPAHs are unknown. There are two major NPAH formation processes. Primary formation of NPAHs occurs directly during the combustion of organic materials. The secondary formation of NPAHs occurs through the transformation of PAHs after they have been released into the environment. The fate, transport, and health effects of NPAHs are considerably different from their parent PAHs because of these differing formation processes. However, the amount of research conducted on NPAHs is comparatively low relative to PAHs. This is primarily due to a lack of effective analytical method for NPAHs, which generally exist in the environment at concentrations one to three orders of magnitude lower than PAHs. However, with the development of more sensitive analytical methods, the number of research papers published on NPAHs has recently increased. The Western Pacific region, one of the post polluted areas in the world, is the most frequently studied area for NPAHs. Many of them reported that atmospheric concentrations of NPAHs were much lower than parent PAHs and oxygenated derivatives (OPAHs). In this article, recent research on sample treatment and analysis, as well as the sources and environmental fate of NPAHs, are discussed with PAHs and OPAHs. A notable achievement using NPAHs is the development of a new emission source analysis method, the NP method, whose features are also discussed in this review.

Source identification and ecological risks of parent and substituted polycyclic aromatic hydrocarbons in river surface sediment-pore water systems: Effects of multiple factors

Substituted polycyclic aromatic hydrocarbons (SPAHs) have shown higher health and ecological risks than the corresponding parent PAHs (PPAHs) from laboratory studies, their variations in freshwater system, especially in surface sediment and pore water, remain inadequate understanding. In this study, we revealed the coexistence, ecological risk, and multiple factors affecting variations and sources of PPAHs and SPAHs (nitrated PAHs (NPAHs), oxygenated PAHs (OPAHs)) in the surface sediment-pore water system from a typical urban river in Northern China. The concentration ranges of Σ26PPAHs, Σ10NPAHs, and Σ4OPAHs in the surface sediments were 153.0–5367.4, not detected (N.D.)–105.4, and 42.2–1177.0 ng·g−1 dry weight, and fell within 0.6–38.8, N.D.–297.9, and N.D.–212.6 ng·mL−1 in the pore waters. The t-distributed stochastic neighbor embedding (SNE) coupled with the partitioning around medoids (PAM) elucidated spatiotemporal the variations in PAHs, emphasizing the impacts of industrial activities and sewage discharges. Besides the geochemical and hydrochemical conditions, SPAHs were affected by the potential secondary formation, especially during the wet season. The method comparisons indicated the advantages of principal component analysis-multivariate linear regression (PCA-MLR) and n-alkanes model on source identification. PAHs mainly originated from fossil fuel combustion and vehicular exhaust. The top risk quotient (RQ) values for PAHs occurred in the urban and industrial sections. A majority of the surface sediment samples emerged with low to moderate exposure risks, while all the pore water samples showed high exposure risks. The RQs of OPAHs were significantly higher (p < 0.01) than those of PPAHs. The results suggested the secondary formation of SPAHs as an important role in ecological risks of PAHs in the urban river system.

Chemical signatures of polycyclic aromatic hydrocarbons in the emissions from in situ oil burns.

This study characterized the parent and alkylated polycyclic aromatic hydrocarbons (PAHs) in gaseous and particulate emissions from the in situ burning (ISB) of oils. The experimental results indicate that the burning of the heavy oil produced the most PAH emissions because of its longest burning time. In addition, the parent PAHs mainly exist in the particulate phase, while alkylated PAHs mostly accumulate in the gaseous phase. In particular, the diagnostic-ratios of PAHs with great stability in both gaseous and particulate emissions from ISB are identified by comparing the laboratory and field data. The presences of bell-, slope- and V-shaped distribution patterns of alkylated PAHs in the emissions precisely indicate their sources to be petrogenic and pyrogenic processes occurring during ISB. The formation of 2-methylanthracene during ISB is confirmed. The overall findings are expected to provide a prospective protocol to characterize PAH pollution from ISB emissions in case of oil spills.

Chlorinated Polycyclic Aromatic Hydrocarbons Induce Immunosuppression in THP-1 Macrophages Characterized by Disrupted Amino Acid Metabolism.

Frequent chlorinated polycyclic aromatic hydrocarbon (Cl-PAH) occurrence in environmental samples and emerging detection in human serum have warned of their underestimated risks. Studies showed that some Cl-PAHs exhibit dioxin-like properties, implying immunotoxic potential but lacking direct evidence and specific mechanisms. Here, we integrated a high-content screening (HCS) system and high-resolution mass spectrometry to investigate the immune dysfunction and metabolic disruption induced by Cl-PAHs and their parent PAHs (PPAHs) in THP-1 macrophages. Both 9-chloroanthracene and 2,7-dichlorofluorene exerted clear immunosuppression on THP-1 mφs, while their PPAHs exhibited different immune disturbances. Interestingly, Cl-PAH/PPAHs induced complex alterations in the multicytokine/chemokine network, including biphasic alterations with initial inhibition and later enhancement. Furthermore, the protein-protein interaction results revealed that inflammatory cytokines are the core of this complicated network regulation. Connecting immune phenotypes and metabolomics, amino acid metabolism reprogramming was identified as a potential cause of Cl-PAH/PAH-induced immunotoxicity. Phytosphingosine and l-kynurenine were proposed as candidate immunosuppression biomarkers upon Cl-PAH exposure. This article provides direct immunotoxicity evidence of Cl-PAHs without activating AhR for the first time and discusses the contribution of metabolites to Cl-PAH/PPAH-induced immune responses in macrophages, highlighting the potential of developing new methods based on immunometabolism mechanisms for toxic risk evaluation of environmental chemicals.

Presence of Halogenated Polycyclic Aromatic Hydrocarbons in Milk Powder and the Consequence to Human Health.

Recent reports of the presence of halogenated derivatives of polycyclic aromatic hydrocarbons (PAHs) in human foods of animal origin, such as chlorinated (ClPAHs) and brominated (BrPAHs) PAHs, suggest that their contamination in dairy products may also pose a human health risk. This study used GC/Orbitrap-MS to analyze 75 congeners of halogenated PAHs and parent PAHs in milk and creaming powder samples commonly found in grocery stores in Sri Lanka and Japan. Our investigation revealed a total of 31 halogenated PAHs (HPAHs) in the samples. The concentrations of total parent PAHs in the samples from Sri Lanka and Japan ranged from not detected (n.d.)–0.13 and <0.001–16 ng/g dry weight (d.w.). Total ClPAHs and BrPAHs in the samples ranged from 0.01–3.35 and 1.20–5.15 ng/g (d.w.) for Sri Lanka, and 0.04–2.54 and n.d.–2.03 ng/g d.w. for Japan, respectively. The ClPAHs were dominated by chlorinated-pyrene, -fluoranthene, and -benzo[a]pyrene congeners, whereas the BrPAHs were dominated by brominated-naphthalene and -pyrene congeners. The toxic assessment estimated based on the intake of toxic equivalency quotients (TEQs) for target compounds in milk powders revealed that HPAHs might contribute additively to the PAHs-associated health risk to humans, indicating that more research is needed.

Prediction study on the distribution of polycyclic aromatic hydrocarbons and their halogenated derivatives in the atmospheric particulate phase

Polycyclic aromatic hydrocarbons (PAHs) and their halogenated derivatives (X-PAHs), which generally produced from photochemical and thermal reactions of parent PAHs, widely exist in the environment. They are semi-volatile organic chemicals (SVOCs) and the partitioning between gas/particulate phases affects their environmental migration, transformation and fate, which further impacts their toxicity and health risk to human. However, there is a large data missing of the experimental distribution ratio in the atmospheric particulate phase (f), especially for X-PAHs. In this study, we first checked the correlation between experimental f values of 53 PAH derivatives and their octanol-air partitioning coefficients (log KOA), which is frequently used to characterize the distribution of chemicals in organic phase, and yielded R2 = 0.803. Then, quantum chemical descriptors derived from molecular structural optimization by M06–2X/6–311 +G (d,p) method were further employed to develop Quantitative Structure-Property Relationship (QSPR) model. The model contains two descriptors, the average molecular polarizability (α) and the equilibrium parameter of molecular electrostatic potential (τ), and yields better performance with R2 = 0.846 and RMSE = 0.122. The mechanism analysis and validation results by different strategies prove that the model can reveal the molecular properties that dominate the distribution between gas and particulate phases and it can be used to predict f values of other PAHs/X-PAHs, providing basic data for their environmental ecological risk assessment.

Nitrated and oxygenated polycyclic aromatic hydrocarbons emissions from solid fuel combustion in rural China: Database of 12 real-world scenarios for residential cooking and heating activities

Polycyclic aromatic hydrocarbons (PAHs) derivatives such as oxygenated PAHs (oPAHs) and nitrated PAHs (nPAHs), are receiving raising concerns due to their high toxic potential. Incomplete solid fuel combustion can release large quantities of PAHs derivatives, especially in low-efficiency domestic stoves. In this study, field measurements were conducted in rural Chinese homes to determine emissions of nPAHs and oPAHs from solid fuel combustion. A total of 12 fuel-stove combinations including cooking and space heating activities were investigated. Emission factors (EFs) of total nPAHs and oPAHs were in the range of 1.0–682.1 μg/kg and 0.01–131.7 mg/kg, respectively, with arithmetic means and stand deviations of 53.5 ± 72.5 μg/kg and 13.9 ± 24.4 mg/kg, respectively. The EFs of nPAHs and oPAHs for coal combustion (including honeycomb briquette, coal chunk, and peat tested in this study) were 30.2 ± 28.1 μg/kg and 1.5 ± 2.9 mg/kg, respectively, much lower than that for biomass burning (p < 0.05). The combustion phase could significantly affect the PAHs derivative emissions with higher emissions at initial phase than that at stable phase. Fuel type was found to affect the EFs, composition profiles, and ratios of PAHs derivatives to parent PAHs. This study tries to have an insight of PAHs derivative emissions from various solid fuel combustion, which would be useful in understanding the atmospheric PAHs derivative pollutions in China.

Study on the variations of extractable polycyclic aromatic hydrocarbons in lignite and semi-coke

Low-temperature pyrolysis is one of the most important technologies for the clean and efficient utilization of lignite. Semi-coke, the solid product of this process, has been widely used as both an industrial and household clean fuel. In this study, three lignites from China (EE), Indonesia (YN), and Mongolia (WM) and their semi-cokes obtained through pyrolysis at 550 °C were treated with dichloromethane, and the extracted polycyclic aromatic hydrocarbons (PAHs) were analyzed using a gas chromatograph/mass spectrometer. The results showed that the total concentrations of PAHs in EE, YN, and WM were 125000, 4400, and 5800 ng/g, respectively, and those in their semi-cokes were 4700, 10000, and 5500 ng/g, respectively. The concentrations of alkylated PAHs (aPAHs) were higher than those of parent 16 US EPA priority PAHs (16 PAHs) in lignites, while parent 16 PAHs were more abundant in semi-cokes. Both lignites and semi-cokes were dominated by 2-ring PAHs (naphthalene and alkylated naphthalenes), followed by 3- and 4-ring PAHs. The proportion of 2-ring PAHs in the semi-cokes increased with respect to that in the lignites, and the degree of alkylation of the PAHs decreased. This suggested that the extractable PAHs changed to smaller parent PAHs during the low-temperature pyrolysis. The concentration and composition of PAHs in the mobile phase of the semi-coke are an important part of its structural characteristics and are closely related to the macromolecular structure of raw coal. Thus, this study on PAHs in semi-coke provides relevant information on the structural evolution of coal during pyrolysis and further improves our understanding of clean fuel.

Parent and Halogenated Polycyclic Aromatic Hydrocarbons in the Serum of Coal-Fired Power Plant Workers: Levels, Sex Differences, Accumulation Trends, and Risks.

Workers in coal-fired power plants are at a high risk of exposure to polycyclic aromatic hydrocarbons (PAHs) and their halogenated derivatives (HPAHs), yet no studies have investigated such exposure of HPAHs. In this study, 12 PAHs and 8 chlorinated PAHs, but no brominated PAHs, were detected in >80% of serum samples from workers of a coal-fired power plant in eastern China. Serum HPAH concentrations were higher in plant workers (16-273 ng/g lipid) than in people without occupational exposure (12-51 ng/g lipid), and serum PAH and HPAH concentrations both in male and female workers were positively correlated with the occupational exposure duration, with an estimated doubling time of 11-17 years. Correlations were found between concentrations of ∑8HPAHs and ∑12PAHs but not between 7-chlorobenz[a]anthracene (7-ClBaA) and 1-chloropyrene (1-ClPyr) and their respective parent PAHs. In males, total concentrations of PAHs and HPAHs were positively correlated with pulmonary hypofunction and hypertension but not with abnormal electrocardiogram. The benzo[a]pyrene equivalents ratio of ∑8HPAHs/∑12PAHs was 0.3 ± 0.1. Among the HPAHs in the serum, 9-chlorophenanthrene, 7-ClBaA, and 1-ClPyr showed high health risks. This study is the first report on HPAH exposure in coal-fired power plant workers and provides new evidence on the health risks of PAHs and HPAHs in humans.

PAH depletion in weathered oil slicks estimated from modeled age-at-sea during the Deepwater Horizon oil spill

During time-periods oil slicks are in the marine environment (age-at-sea), weathering causes significant changes in composition and mass loss (depletion) of oil spill chemicals including the more toxic polycyclic aromatic hydrocarbons (PAHs). The goal of this study was to estimate the age-at-sea of weathered oil slicks using the oil spill module of the Connectivity Modeling System and to use this age to interpret PAH concentration measurements. Percent depletion (PD) for each measurement was computed as the percentage difference between the original and measured PAH concentration in the crude oil and weathered oil slicks, normalized upon the mass losses relative to hopane. Mean PD increased with estimated age-at-sea for all PAHs. Less PD was observed for alkylated than for parent PAHs, likely due to decreasing vapor pressure with increasing degree of alkylation. We conclude that estimated age-at-sea can be used to explain PAH depletion in weathered oil slicks. We propose PAH vapor pressure can be coupled with the model to expand capacity for predicting concentration distributions of individual parent and alkylated PAHs in weathered oil along the coastline. This new module will advance the science supporting oil spill response by providing more certain estimates of health risks from oil spills.

Levels, profiles and potential human health risks of brominated and parent polycyclic aromatic hydrocarbons in soils around three different types of industrial areas in China

Brominated polycyclic aromatic hydrocarbons (Br-PAHs) are an emerging class of persistent organic pollutants with toxicity similar to dioxins. Industrial thermal processes have been identified as major sources of Br-PAHs in the current environment. However, studies on soil contaminations with Br-PAHs around industrial areas were scarce. In this study, 18 Br-PAHs and 16 PAHs were analyzed in soils around an electronic waste dismantling area (EDA), an industrial area that mainly performed steel smelting (SSP), and an industrial area mainly performed secondary copper smelting (SCS). The mean concentrations of Br-PAHs and PAHs were 1362 pg/g and 1034 ng/g, 582 pg/g and 13,938 ng/g, and 307 pg/g and 2211 ng/g in the soil around EDA, SSP, and SCS, respectively. The order of Br-PAH concentrations among three industrial areas was inconsistent with that of PAHs, suggesting that there may be some differences in contamination characteristics of Br-PAHs in three types of industrial areas. The significant correlation between Br-PAHs and parent PAHs indicated that direct bromination may be the main formation pathway of Br-PAHs in soils in EDA. The result of principal component analysis further revealed that the congener pattern of Br-PAHs in soils around EDA is different from that of SSP and SCS. It was found that the ratio of 1-BrPyr and 3-BrFlu can be applied to identify environmental contamination with Br-PAHs from e-waste dismantling. The health risk assessment results showed that there were some soil samples with carcinogenic risks above the risk threshold in each industrial area, and deserve our concern.

Prediction of •OH-Initiated and •NO3-Initiated Transformation Products of Polycyclic Aromatic Hydrocarbons by Electronic Structure Approaches.

The abiotic reaction products of polycyclic aromatic hydrocarbons (PAHs) with hydroxyl radicals (•OH) and nitrate radicals (•NO3) are nitro-, oxygen-, and hydroxyl-containing PAHs (NPAHs, OPAHs, and OHPAHs). Four methods of the highest occupied molecular orbital (HOMO), Fukui function (FF), dual descriptor (DD), and population of π electrons (PP-π) are selected to predict the chemical reactivity of PAHs attacked by •OH and •NO3 in this study. The predicted •OH-initiated and •NO3-initiated transformation products are compared with the main PAH transformation products (PAH-TPs) observed in the laboratory. The results indicate that PP-π and DD approaches fail to predict the transformation products of fused PAHs containing five-membered rings. By predicting the PAH-TPs of 13–14 out of the 15 parent PAHs accurately, HOMO and FF methods were shown to be suitable for predicting the transformation products formed from the abiotic reactions of fused PAHs with •OH and •NO3.

Particle size-resolved emission characteristics of complex polycyclic aromatic hydrocarbon (PAH) mixtures from various combustion sources

Combustion of domestic solid fuels is a significant source of polycyclic aromatic hydrocarbons (PAHs). Some oxygenated PAHs (o-PAHs) and PAHs with molecular weight of 302 (MW302 PAHs) are more toxic than the traditional 16 priority PAHs, whereas their emissions were much less elucidated. This study characterized the size-dependent emissions of parent PAHs (p-PAHs), o-PAHs, and MW302 PAHs from various combustion sources. The estimated emission factors (eEFs) from biomass burning sources were highest for most of the PAHs (391–8928 μg/kg), much higher than that of anthracite coal combustion (43.0–145 μg/kg), both which were operated in an indoor stove. Cigarette smoking had a high eEF of o-PAHs (240 ng/g). MW302 PAHs were not found in the emissions of smoking, cooking, and vehicular exhausts. Particle-size distributions of PAHs were compound- and source-dependent, and the tendency to associate with smaller particles was observed especially in biomass burning and cigarette smoking sources. Furthermore, the inter-source differences in PAH eEFs were associated with their dominance in fine particles. PAH composition profiles also varied with the particle size, showing increasing contributions of large-molecule PAHs with decreasing sizes in most cases. The size distributions of p-PAHs are much more significantly dependent on their n-octanol/air partition coefficients and vapor pressures than those of o-PAHs, suggesting differences in mechanisms governing their distributions. Several molecular diagnostic ratios (MDRs), including two based on MW302 PAHs, specific to these combustion scenarios were identified. However, the MDRs within some sources are also strongly size-dependent, providing a new explanation for the uncertainty in their application for source identification of PAHs. This work also highlights the necessity for understanding the size-resolved atmospheric behaviors and fate of PAHs after their emission.