Using diagnostic ratios to characterize sources of polycyclic aromatic hydrocarbons in the Great Lakes atmosphere

Development of diffusive gradients in thin-films technique for monitoring polycyclic aromatic hydrocarbons in coastal waters

Addressing the challenge of accurately monitoring polycyclic aromatic hydrocarbons (PAHs) in aquatic systems, this study employed diffusive gradients in thin-films (DGT) technique to achieve methods detection limits as low as 0.02 ng L-1 to 0.05 ng L-1 through in situ preconcentration and determination of time-integrated concentrations. The efficacy of the developed DGT samplers was validated under diverse environmental conditions, demonstrating independence from factors such as pH (5.03-9.01), dissolved organic matter (0-20 mg L-1), and ionic strength (0.0001-0.6 M). Notably, the introduction of a novel theoretical approach to calculate diffusion coefficients based on solvent-accessible volume tailored for PAHs significantly enhanced the method's applicability, particularly for organic pollutants with low solubility. Field deployments in coastal zones validated the DGT method against traditional grab sampling, with findings advocating a 4 to 7-day optimal deployment duration for balancing sensitivity and mitigating lag time effects. These results provide a sophisticated, efficient solution to the persistent challenge of monitoring hydrophobic organic pollutants in aquatic environments, broadening the scope and applicability of DGT in environmental science and providing a robust tool for researchers.

Polycyclic aromatic hydrocarbon (PAH) source identification and a maternal transfer case study in threatened killer whales (Orcinus orca) of British Columbia, Canada

The northeastern Pacific (NEP) Ocean spans the coast of British Columbia (Canada) and is impacted by anthropogenic activities including oil pipeline developments, maritime fossil fuel tanker traffic, industrial chemical effluents, agricultural and urban emissions in tandem with stormwater and wastewater discharges, and forest wildfires. Such events may expose surrounding marine environments to toxic polycyclic aromatic hydrocarbons (PAHs) and impact critical habitats of threatened killer whales (Orcinus orca). We analyzed skeletal muscle and liver samples from stranded Bigg's killer whales and endangered Southern Resident killer whales (SRKWs) for PAH contamination using LRMS. C3-phenanthrenes/anthracenes (mean: 632 ng/g lw), C4-dibenzothiophenes (mean: 334 ng/g lw), and C4-phenanthrenes/anthracenes (mean: 248 ng/g lw) presented the highest concentrations across all tissue samples. Diagnostic ratios indicated petrogenic-sourced contamination for SRKWs and pyrogenic-sourced burdens for Bigg's killer whales; differences between ecotypes may be attributed to habitat range, prey selection, and metabolism. A mother-fetus skeletal muscle pair provided evidence of PAH maternal transfer; low molecular weight compounds C3-fluorenes, dibenzothiophene, and naphthalene showed efficient and preferential exposure to the fetus. This indicates in-utero exposure of PAH-contamination to the fetus. Our results show that hydrocarbon-related anthropogenic activities are negatively impacting these top predators; preliminary data found here can be used to improve oil spill and other PAH pollution management and regulation efforts, and inform policy to conserve killer whale habitats in the NEP.

Aged polycyclic aromatic hydrocarbons as stratigraphic marker in the Anthropocene: Evidence from Tibetan Lake sediments

Polycyclic aromatic hydrocarbons (PAHs) were supposed to serve as combustion marker reflecting the past energy use, but it was unclear whether their sediment records in the Anthropocene were "weathered" due to aging-induced formation of bound residues. In this study, the total concentration of PAHs (the sum of rapid desorption, slow desorption, and bound residue fractions) were determined in four dated sediment cores from eastern to central Tibet using multi-step sequential extraction method. The total 16 PAH concentrations were 11.8, 13.5, 18.9, and 29.4 ng/g dw (in average) in the Co Ngoin, Pung Co, Ahung Co, and Putok lakes, respectively. The stratigraphic records and estimated source contributions of PAHs in different areas of Tibet exhibited a coherent change in the mid-20th century in response to the Holocene-Anthropocene transition. The sediment PAHs also displayed a comparable pattern when the bound residue fraction was not accounted for, suggesting their effective retainability under natural aging conditions. This may be elucidated by the enduring forward and back conversions between slow desorption and bound residue fractions, which manifested similar time-dependent variations across PAH congeners. The distinct conversion tendencies of different congeners were predicted by the binding affinity of congeners to surface/inner regions of organic matter using molecular docking simulations. Our findings demonstrate the persistence of sediment PAH records under natural aging and validate the use of PAH documentary evidence for investigating the Anthropocene.

Biomonitoring of polycyclic aromatic hydrocarbons in Brazilian pregnant women: Urinary levels and health risk assessment

Over the years, humans have been continuously exposed to several compounds directly generated by industrial processes and/or present in consumed products. Polycyclic aromatic hydrocarbons (PAHs) are legacy pollutants ubiquitous in the environment and represent the main chemical pollutants in urban areas. Worldwide, studies that aim to understand the impacts of exposure to these chemicals have gained increasing prominence due to their potential toxicity profile, mainly concerning genotoxicity and carcinogenicity. Human biomonitoring (HB) is an analytical approach to monitoring population exposure to chemicals; however, these studies are still limited in Brazil. Thus, this work aimed to evaluate the exposure of Brazilian pregnant women to PAHs through HB studies. Besides, the risk characterization of this exposure was performed. For this purpose, urine samples from 358 Brazilian pregnant women were used to evaluate 11 hydroxylated metabolites of PAHs employing gas chromatography coupled to mass spectrometry. The 1OH-naphthol and 2OH-naphthol were detected in 100% of the samples and showed high levels, corresponding to 16.99 and 3.62 μg/g of creatinine, respectively. 2OH-fluorene (8.12 μg/g of creatinine) and 9OH-fluorene (1.26 μg/g of creatinine) were detected in 91% and 66% of the samples, respectively. Benzo(a)pyrene (BaP) metabolites were detected in more than 50% of the samples (0.58-1.26 μg/g of creatinine). A hazard index of 1.4 and a carcinogenic risk above 10-4 were found for BaP metabolites in the risk characterization. Therefore, our findings may indicate that exposure to PAHs poses a potential risk to pregnant women's health and a high probability of carcinogenic risk due to their exposure to BaP. Finally, this work shows the need for more in-depth studies to determine the sources of exposure and the implementation of health protection measures regarding the exposure of the Brazilian population to PAHs.

Emission profiles, source identifications, and health risk of polycyclic aromatic hydrocarbons (PAHs) in a road tunnel located in Xi'an, China

Understanding the sources and characteristics of PM2.5-bound PAHs from traffic-related pollution can provide valuable data for mitigating air contamination from traffic in local urban regions. However, little information on PAHs is available regarding the typical arterial highway-Qinling Mountains No.1 tunnel in Xi'an. We estimated the profiles, sources, and emission factors of PM2.5-bound PAHs in this tunnel. The total PAH concentrations were 22.78 ng·m-3 and 52.80 ng·m-3 at the tunnel middle and exit, which were 1.09 and 3.84 times higher than that at the tunnel entrance. Pyr, Flt, Phe, Chr, BaP, and BbF were the dominant PAH species (representing approximately 78.01% of total PAHs). The four rings PAHs were dominant (58%) among the total PAH concentrations in PM2.5. The results demonstrated that diesel and gasoline vehicles exhaust emissions contributed 56.81% and 22.60% to the PAHs, respectively, while the corresponding value for together brakes, tyre wear, and road dust was 20.59%. The emission factors of total PAHs were 29.35 μg·veh-1·km-1, and emission factors of 4 rings PAHs were significantly higher than those of the other PAHs. The sum of ILCR was estimated to be 1.41×10-4, which accorded with acceptable level of cancer risk (10-6-10-4), PAHs should not ignored as they still affect the public health of inhabitants. This study shed light on PAH profiles and traffic-related sources in the tunnel, thereby facilitating the assessment of control measures targeting PAHs in local areas.

A novel biomass pyrogenic index and its application coupled with black carbon for improving polycyclic aromatic hydrocarbon source identification

To accurately subdivide the sources of polycyclic aromatic hydrocarbons (PAHs), the composition characteristics of 36 total polycyclic hydrocarbons (T-PAHs; 16 parent PAHs and 20 alkylated PAHs [A-PAHs]) in biomass-residue samples were analyzed. A novel biomass pyrogenic index (BPI) was defined based on A-PAH-fingerprinting differences between biomass-combustion and petroleum sources of PAHs and the sum of the concentrations of pyrene, fluoranthene, benzo[a]anthracene, and alkylated homologs) divided by the ∑value of EPA PAHs with 2-3 rings. BPIs of < 0.5 and > 0.5 indicated that the PAHs originated mainly from biomass combustion and petroleum, respectively. And the ∑targeted A-PAH pairs influencing the BPI/black carbon (BC) ratio was used to identify PAH sources in surface-sediment samples, using 0.5 as the threshold to distinguish between different sources across the strait. The columnar sediments were used to verify the accuracy of two source-identification methods. The results revealed that the main PAH sources changed since 2005, which is highly consistent with those obtained using positive matrix factors and a changing trend in the main types of local energy use. These results highlight the significance of A-PAHs in accurately identifying PAH sources and suggest that applying compositional differences in BC from different sources for PAH-source identification merits further study.

The presence of polycyclic aromatic hydrocarbons (PAHs) in air particles and estimation of the respiratory deposition flux

Polycyclic aromatic hydrocarbons (PAHs) in the atmospheric particles constitute a topic of growing health concern. This study aims to calculate PAH concentrations, identify the source, assess the health risk from exposure to carcinogenic PAHs, and the respiratory deposition flux. PM₁₀ and PM_2.5 were collected in September 2019 in the urban, semi-urban, and semi-urban-industrial areas of Kuala Lumpur, Batu Pahat, and Bukit Rambai, respectively. A total of 18 PAHs from PM₁₀ and 17 PAHs from PM_2.5 were extracted using dichloromethane and determined using gas chromatography coupled with a flame ionization detector (GC-FID). The health risk assessment (HRA) calculated included B[a]P equivalent (B[a]P_eq), lifetime lung cancer risk (LLCR), incremental lifetime cancer risk (ILCR), and respiratory deposition dose (RDD). The results show PAHs in PM₁₀ recorded in Kuala Lumpur (DBKL), Batu Pahat (UTHM), and Bukit Rambai are 9.91, 8.45, and 9.57 ng/m³, respectively. The average PAHs in PM_2.5 at the three sampling sites are 11.65, 9.68, and 9.37 ng/m³, respectively. The major source of PAHs obtained from the DRs indicates pyrogenic activities for both particle sizes. For PM₁₀, the total B[a]P_eq in DBKL, UTHM, and Bukit Rambai were 1.97, 1.82, and 2.32 ng/m^3, respectively. For PM_2.5 samples, the total B[a]P_eq in DBKL, UTHM, and Bukit Rambai were 2.80, 2.33, and 2.57 ng/m³_, respectively. The LLCR and ILCR show low to moderate risk for all age groups. The RDD of adults and adolescents is highest in both PM₁₀ and PM_2.5, followed by children, toddlers, and infants. Overall, we perceive that adults and adolescents living in the urban area of Kuala Lumpur are at the highest risk for respiratory health problems because of prolonged exposure to PAHs in PM₁₀ and PM_2.5, followed by children, toddlers, and infants.

Insights into seasonal-variability of SVOCs, morpho-elemental and spectral characteristics of PM2.5 collected at a dense industrial site: Faridabad, Haryana, India

The development-oriented anthropogenic activities have led to intensive increase in emission of various organic pollutants, which contribute considerably to human health risk. In the present study, chemical, physical and spectral characterisation of fine particulate matter (PM_2.5), collected at Faridabad city, in northern India, were examined. Seasonal variation of organic compounds [n-alkanes, polyaromatic hydrocarbons (PAHs) and phthalic acid esters (PAEs)], and potential health risk of Polyaromatic hydrocarbons (PAHs) exposure using toxic equivalency potential (TEQ) approach had been assessed. These showed seasonal average values ranging from 156.4 ± 57.0 ng/m³ to 217.6 ± 72.9 ng/m³, 98.0 ± 21.4 ng/m³ to 177.8 ± 72.8 ng/m³, and 30.9 ± 11.9 ng/m³ to 82.5 ± 29.2 ng/m³, respectively, with the highest value for winter. It is noteworthy that unlike, n-alkanes and PAEs, PAHs were least during spring. The high molecular weight PAHs (BaP, BkF, DahA and IcdP) were found to exhibit higher TEQ values (ranging from 0.7 to 9.7) despite of their lower concentrations. The PAH diagnostic ratio, carbon preference index and total index revealed the enhanced impact of biogenic sources of emissions in comparison to diesel emission sources during winter.

Investigation of the origin and concentration of polycyclic aromatic hydrocarbon with improved accuracy by the use of a multi-component integrated calibration method in the Katowice region, Poland

The basic variant of the integrated calibration method (ICM), based on a combination of external calibration (EC) and standard addition method (SAM), was applied to multi-component (MC) analysis to obtain a new methodological approach to improve the quality of analytical results. The analytical performance of the proposed method was evaluated on indicated by EPA polycyclic aromatic hydrocarbons (PAHs) determination in various environmental samples (air, house dust, tap water, river water, river sediment, and snow) from the Katowice region (Poland). HPLC-FLD was used during all analyses. The main aim was to show the origin of PAHs in different places in the urban and industrialized region of Poland. MC-ICM allowed for the elimination of interference from the coelution of other substances. Several diagnostic coefficients were calculated for the results free from systematic errors and interferences. The obtained results were consistent with the chemometric analysis (PCA). The method was assessed regarding analytical usefulness using the RGB model (the color method is White) and environmental friendliness using the AGREE approach.

Spatio-temporal distribution and sources of polycyclic aromatic hydrocarbons in Tunis Lagoon: Concentrations in sediments and Marphysa sanguinea body and excrement

Despite international recognition as an important coastal wetland, Tunis Lagoon is still subjected to anthropogenic pressures. This article provides valuable data on the spatio-temporal distribution, toxicity, and origins of polycyclic aromatic hydrocarbons (PAHs) in the Tunis Lagoon complex. PAHs' concentrations were measured in Marphysa sanguinea body and excrements, as well as in surface sediments. Total mean PAHs' concentrations reached a maximum of 2398 ng/g dry weight (DW) in sediments, 1007.19 ng/g DW in M. sanguinea, and 2602.05 ng/g DW in excrements. Diagnostic PAHs' ratios were used to determine whether PAHs' origins were pyrogenic or petrogenic. Our data showed a predominance of PAHs with a pyrogenic source. Principal component analysis showed PAHs isolated from polychaetes clearly separated from those measured in sediment and excrement. We believe that sediments are not the main source of bioaccumulation by M. sanguinea. Moreover, the toxicity of PAHs in sediments is moderate to high for benthic organisms.

Spatial distribution, driving factors and health risks of fine particle-bound polycyclic aromatic hydrocarbons (PAHs) from indoors and outdoors in Hefei, China

Atmospheric particulate matter, especially in urban and industrial environments, can act as a source of different organic pollutants that can pose significant health impacts to residents. However, the pollution status and transport mechanisms of fine particle-bound polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor environments are uncertain. This study aimed to determine the spatial distribution and morphological characteristics of fine particle-bound PAHs and analyze the factors (source contributions and backward trajectories) that influence their concentrations. The results showed that mean concentrations of 16 PAHs were higher in indoor dust as compared to outdoor dust. In addition, the lowest concentrations of the 16 PAHs were found on the 11-20th floor, with smoking households > nonsmoking households (except Nap, Acy, and Ace). The 2-3 ring PAHs were more prominent in households with cooking activities. The particle size distribution showed that most of the particles were <62 μm in diameter, indicating that the indoor particles were smaller in size. Furthermore, the range of δ13C values in the outdoor dust (-30.17 ~ -28.63 ‰) samples was significantly lower than in indoor dust (-28.29 ~ -22.53 ‰). The results based on diagnostic ratios, positive matrix factorization (PMF) analysis and backward trajectory model analysis suggested that the sources of PAHs in indoor and outdoor dust were mixed, originated both locally and from neighboring provinces transported over long distances, especially concentrated in the Yangtze River Delta area. Finally, carcinogenic risk values for indoor dust were greater than those for outdoor dust. Therefore, it is recommended that local governments and industries with high PAH emissions should implement proper protocols to monitor and minimize the pollution levels of PAHs in the urban industrial environment in order to mitigate their health risks.

Bioaccessibility and Toxicity Assessment of Polycyclic Aromatic Hydrocarbons in Two Contaminated Sites

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous soil contaminants, and their bioaccessibility determines their environmental risks in contaminated land. In the present study, the residual concentrations of PAHs in the soils of two industrial sites were determined, and their bioaccessibility was estimated by the hydroxypropyl-β-cyclodextrin extraction (HPCD) extraction method. The results showed heavy PAH contamination at both site S1 (0.38-3342.5 mg kg^-1) and site S2 (0.2-138.18 mg kg^-1), of which high molecular weight (HMW) PAHs (4-, 5-, and 6-ring compounds) accounted for approximately 80%. The average bioaccessibility of PAHs at sites S1 and S2 was 52.02% and 29.28%, respectively. The bioaccessibility of certain PAH compounds decreased with increasing ring number of the molecule. Lower PAH bioaccessibility was detected in loamy and silty soil textures than in sandy soil. Moreover, among the soil properties, the dissolved organic matter, total organic carbon, total potassium, and total manganese concentrations had significant effects on the bioaccessibility of PAHs. The toxicity analysis showed that the composition and bioaccessibility of PAHs could affect their potential toxicity in soil. We suggest that bioaccessibility should be taken into consideration when assessing the toxicity of PAHs in soil, and more attention should be given to low-ring PAHs with high bioaccessibility.

Semi-volatile organic compounds in fine particulate matter on a tropical island in the South China Sea

Measurements of hazardous semi-volatile organic compounds (SVOCs) in remote tropical regions are rare. In this study, polycyclic aromatic compounds (PACs) [including polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (NPAHs), and oxygenated PAHs (OPAHs)], organophosphate esters (OPEs), and phthalic acid esters (PAEs) were measured in fine particulate matter (PM_2.5) at Yongxing Island in the South China Sea (SCS). The concentrations of PACs (median = 53.5 pg/m³) were substantially low compared with previous measurements. The concentration weighted trajectory (CWT) model showed that the eastern and southern China was the main source region of PAC, occurring largely during the northeast (NE) monsoon. The PM_2.5 showed remarkably high concentrations of OPEs (median = 3231 pg/m³) and moderate concentrations of PAEs (13,013 pg/m³). Some Southeast Asian countries were largely responsible for their higher concentrations, driven by the tropical SCS monsoons. We found significant atmospheric loss of the SVOCs, which is an explanation for the low concentrations of PACs. Enhanced formation of N/OPAHs originated from tropical regions was also observed. The positive matrix factorization model was applied to apportion the SVOC sources. The results, as well as correlation analyses of the SVOC concentrations, further indicate insignificant local sources and enhanced atmospheric reactions on this island.

Assessment of Alkylated and Unsubstituted Polycyclic Aromatic Hydrocarbons in Air in Urban and Semi-Urban Areas in Toronto, Canada

22 alkylated polycyclic aromatic hydrocarbons (alk-PAHs) were characterized in ambient air individually for the first time in urban and semi-urban locations in Toronto, Canada. Five unsubstituted PAHs were included for comparison. Results from the measurements were used to estimate benzo[a]pyrene equivalent toxicity (BaPeq) of individual compounds in order to investigate the significance of a single compound in contributing to the overall toxic equivalency (TEQ) of air mixtures. To determine which compounds merit further investigation, BaPeq values of individual compounds were compared to the measured BaP toxicity. Our results showed that both unsubstituted and alkylated PAHs were more abundant in the urban area (38 and 30%, respectively). Benzo[a]pyrene levels at the urban location exceeded Ontario's 24 h guideline (40% of the events), and on average, it was 5 times higher than that at the semi-urban area. Gas-phase two- and three-ring compounds contributed up to 39% (urban) and 76% (semi-urban) of the TEQ of all compounds analyzed. Some alk-PAHs such as 7,12-dimethylbenzo[a]anthracene had a huge impact on the toxicity of urban air, and its BaPeq was on average 8 times higher than that of BaP. We emphasize that the toxic impact of alkylated and gaseous PAHs, which is not routinely included in many air monitoring programs, is significant and should not be neglected.

Polycyclic aromatic hydrocarbon occurrence in forest soils in response to fires: a summary across sites

Forest fires are important sources of polycyclic aromatic hydrocarbons (PAHs) in soils. However, factors controlling PAH production in soils subjected to fires in different sites are poorly understood. Here, we analyzed 143 sets of previously published data to evaluate the concentrations and composition profiles of PAHs in ash and soils associated with forest fires and to assess the impacts of soil depth, fire intensity, post-fire duration, and vegetation type on their occurrence. Compared to unburned soils, the total PAH concentrations increased by 205% (95% confidential interval of 152-269%; n = 136) in soils associated with fires. This increase surpassed that of PAH toxic equivalents (73%) because fires produce dominantly low-ring PAHs with relatively low toxicity. PAH concentrations in fire-impacted sites increased by 684%, 258%, and 155% in the ash, 0-5 cm soil depth interval, and >5 cm soil depth interval, respectively. The increases in PAH concentrations associated with mild-intensity fires (412%) exceeded those associated with moderate-intensity (163%) and high-intensity (168%) fires, which is possibly due to pyromineralization or volatilization of organic matters at high burning temperatures. These increases were highest within a month after the fire (280%), gradually decreasing over time, and showed no significant difference compared to the reference sites after 24 months. The concentration increases exhibit no major difference between various vegetation types (broad-leaved forest vs. coniferous forest vs. shrub). Assessments reveal that exposure to post-fire soil PAHs involves no serious human health risk. However, potential adverse effects of soil PAHs on other organisms (e.g., microbes and plants) and ecosystems should be further examined. The present study highlights the strong impacts of soil depth, fire intensity, and post-fire duration, and the relatively weak impact of the vegetation type on PAH concentrations in soils associated with fires in different areas.

Emission factors and chemical characterization of particulate emissions from garden green waste burning

This work provides an evaluation of the emission factors (EFs) of typical garden waste burning (fallen leaves and hedge trimming) in terms of particulate matter (PM), elemental and organic carbon (EC-OC) together with a detailed chemical characterization of 88 particle-bound organic species including polycyclic aromatic hydrocarbons (PAHs), levoglucosan and its isomers, lignin breakdown products (methoxyphenols), cholesterol, alkanes, polyols and sugars. Furthermore, wood-log based burning experiments have been performed to highlight key indicators or chemical patterns of both, green waste and wood burning (residential heating) sources, that may be used for PM source apportionment purposes. Two residential log wood combustion appliances, wood stove (RWS) and fireplace, under different output conditions (nominal and reduced) and wood log moisture content (mix of beech, oak and hornbeam), have been tested. Open wood burning experiments using wood logs were also performed. Green waste burning EFs obtained were comparable to the available literature data for open-air biomass burning. For PM and for most of the organic species studied, they were about 2 to 30 times higher than those observed for wood log combustion experiments. Though, poor performance wood combustions (open-air wood log burning, fireplace and RWS in reduced output) showed comparable EFs for levoglucosan and its isomers, methoxyphenols, polyols, PAHs and sugars. Toxic PAH equivalent benzo[a]pyrene EFs were even 3-10 times higher for the fireplace and open-air wood log burning. These results highlighted the impact of the nature of the fuel burnt and the combustion performances on the emissions. Different chemical fingerprints between both biomass burning sources were highlighted with notably a predominance of odd high-molecular weight n-alkanes (higher carbon preference index, CPI), lower levoglucosan/mannosan ratio and lower sinapylaldehyde abundance for green waste burning. However, the use of such indicators seems limited, especially if applied alone, for a clear discrimination of both sources in ambient air.