High Molecular Weight Polycyclic Aromatic Hydrocarbons Research Articles

Wintering loons in South Korea face an ongoing threat from polycyclic aromatic hydrocarbons: Shifting sources and potential DNA damage.

Diving birds, particularly those sharing coastal habitats with fishing grounds, are at risk from oil pollution. Despite documented cases of bird mortality, the specific role of oil pollution in these death remains unclear. To address this knowledge gap, this study examined polycyclic aromatic hydrocarbon (PAH) contamination, its sources, and its impact on loon health. An analysis of 86 carcasses from three species of loons revealed drowning as the leading cause of death, followed by oil pollution and unknown debilitation. While liver concentrations of 16 PAHs (∑PAHs) showed no significant variation by sex, location, species, or cause of death, it was evident that wintering loons were exposed to PAH pollution along South Korea's eastern coast. The ratio of low (di- and tri-cyclic) to high (tetra-, penta-, and hexa-cyclic) molecular weight PAHs was approximately 3-5 across all three loon species. From 2010 to 2017, the composition of PAHs shifted, with a decline in low molecular weight PAHs (indicative of petrogenic sources) and a concerning increase in high molecular weight PAHs (associated with pyrogenic sources). This trend coincided with a tenfold increase in the toxic equivalency quotient of benzo[a]pyrene (TEQBaP), despite a decrease in overall ∑PAH concentrations. The detection of benzo[a]pyrene diol epoxide (BPDE)-DNA adducts in some loons further suggests potential genotoxic effects from PAH exposure. These findings underscore the persistent PAH contamination affecting wintering loons. Continued research is crucial to understand the evolving threats posed by PAHs and to support the conservation of these migratory birds along the North America-Asia flyway.

Variations of microbiota and metabolites in rhizosphere soil of Carmona microphylla at the co-contaminated site with polycyclic aromatic hydrocarbons and heavy metals.

Co-contamination with organic/inorganic compounds is common in industrial area and poses a great risk to local soil ecological environment. In this study, an operating ink factory site co-contaminated with polycyclic aromatic hydrocarbons (PAHs, mild to moderate pollution level) and heavy metals (HMs, heavy pollution level) was selected and screened for native vegetation, Carmona microphylla. High-throughput sequencing and metabolomics were mainly used to investigate the responses of soil bacteria and metabolites to the composite pollution and rhizosphere effect. As the results showed, among three pollution levels, a medium level of pollution was favorable to increase the richness and diversity of soil bacterial community, while high level of pollution greatly decreased special OTUs number. In addition, HMs were the most significant factors driving bacterial community structure, especially for Cd. The influence of medium molecular weight PAHs with 4 rings (MMW-PAHs) on dominant bacteria was greater than low molecular weight PAHs with 2-3 rings (LMW-PAHs) and high molecular weight PAHs with 5-6 rings (HMW-PAHs). Soil bacterial function was affected mainly by pollution level, but not rhizosphere effect, in which high pollution level changed α diversity and structure and composition of C- and N-cycling bacteria. Rhizosphere promoted network complexity by increasing the connection densities among bacterial communities, metabolites, soil properties and the involved number of metabolites. Compared to HMs, PAHs played a more important role in shaping bacterial community through affecting metabolites in non-rhizosphere soil, which was different from rhizosphere soil with a more significant effect of HMs than PAHs. Some key bacterial taxa have established resistance to HMs in rhizosphere soils, whereas they were sensitive to compound contamination in non-rhizosphere soils. Some key bacterial taxa are resistant to HMs in rhizosphere soils, whereas they are susceptible to complex contamination in non-rhizosphere soils, which could be a consequence of the rhizosphere by regulating soil metabolism. It also provides a valuable reference for how co-contaminants and rhizosphere effect shape together soil bacterial community through the changes of soil metabolites.

Enhancing Biodegradation of Insoluble High Molecular Weight Polycyclic Aromatic Hydrocarbons in Macroemulsion (ME) Bioreactors with a Liquid-Liquid Interface.

Due to the low bioavailability and insolubility of high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) in aqueous solutions, their degradation efficiency is significantly limited in wastewater treatment and environmental remediation. To address this challenge, we designed oil-in-water (O/W) macroemulsion (ME) bioreactors with mixed surfactants (Tween-80 and Triton X-100), n-butanol, corn oil, and Burkholderia vietnamiensis (BVs) to enhance the degradation efficiency of pyrene. Owing to the higher solubility of pyrene in MEs, it could be easily adsorbed onto hydrophobic groups on the cell surface. Furthermore, the fluorescence images showed that the BVs were adsorbed on the surface of the MEs, increasing the contact frequency and interactions between pyrene and BVs. Meanwhile, the degradation efficiency of the prepared ME bioreactor was improved by up to 198% compared to that of the conventional surfactant. Therefore, the constructed ME bioreactors can provide green guidance for HMW-PAH biodegradation in industrial wastewater and environmental remediation.

Removal of benzo[a]pyrene by a highly degradable microbial community immobilized by modified wheat straw biochar.

Benzo[a]pyrene (BaP), a high-molecular-weight polycyclic aromatic hydrocarbon (HMW-PAHs), is a prevalent organic pollutant. Due to various environmental factors, the viability and degradation capacity of PAHs-degrading bacteria in contaminated soil are significantly reduced. Therefore, it is imperative to maintain microbial activity and enhance degradation efficiency. This study aims to optimize BaP removal by utilizing biochar-immobilized BaP for the enhancement of microbial communities' degradative potential. The immobilization of modified wheat straw biochar (MWBC) significantly enhanced the removal efficiency of BaP by a highly efficient microbial community enriched from oil-contaminated soil, achieving a large removal efficiency of 75.18% for BaP (5-20mg/L) in a mineral salts medium in 12 d. The study also involved a detection of the species richness and intermediate metabolites of microbial community, as well as an assessment of the challenges and difficulties associated with managing real contaminated sites.

Polycyclic aromatic hydrocarbons in surface sediments of the western Bay of Bengal: Distribution, sources, and ecological risk assessment

This study investigated the distribution, sources, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of the Western Bay of Bengal (WBoB). Coastal, shelf and slope sediments from the WBoB, collected from different research cruises, were analysed for 16 priority PAH pollutants. Total PAHs (TPAHs) were in the range of 1.87–918.79 ng/g and exhibited a significant association with organic matter and silt content with a predominance of high molecular weight (HMW) PAHs congeners. The preferential degradation of the labile low-molecular-weight (LMW) PAHs resulted in the sedimentary accumulation of HMW congeners. A comparison with reported values from other oceanic areas revealed a relatively low concentration of PAHs in WBoB. The isomeric ratios of PAHs could suggest a pyrogenic or petrogenic (crude oil) origin of PAHs. Principal component analysis indicated the dominance of HMW PAHs (petrogenic or combustion) over the LMW fraction. Based on sediment quality guidelines, four congeners [Pyrene (Py), Benzo[a]anthracene (BaA), Chrysene (Ch), and Dibenzo[a,h]anthracene (DbA)] exceeded the threshold effect levels, indicating an adverse impact of these PAHs on the benthic fauna occasionally. The corresponding risk quotients further indicated a moderate risk caused by Py, BaA, and Benzo[b]fluoranthene (BbF) to the biota. This study underscores the importance of proactive management and mitigation strategies to safeguard these vital oceanic ecosystems from the adverse effects of PAHs and other hazardous materials.

Non-Genotoxic and Environmentally Relevant Lower Molecular Weight Polycyclic Aromatic Hydrocarbons Significantly Increase Tumorigenicity of Benzo[a]pyrene in a Lung Two-Stage Mouse Model.

The World Health Organization has classified air pollution as a carcinogen, and polycyclic aromatic hydrocarbons (PAHs) are major components of air particulates of carcinogenic concern. Thus far, most studies focused on genotoxic high molecular weight PAHs; however, recent studies indicate potential carcinogenicity of the non-genotoxic lower molecular weight PAHs (LMW PAHs) that are found in indoor and outdoor air pollution as well as secondhand cigarette smoke. We hypothesize that LMW PAHs contribute to the promotion stage of cancer when combined with benzo[a]pyrene (B[a]P), a legacy PAH. We specifically determined the effects of an LMW PAH mixture containing 1-methylanthracene (1MeA), fluoranthene (Flthn), and phenanthrene (Phe) combined with B[a]P on lung tumor promotion. To test this hypothesis, we used a two-stage, initiation/promotion BALB/ByJ female lung tumor mouse model. The mice were initiated with 3-methylcholanthrene followed by exposures to B[a]P, the LMW PAH mixture, and the combination of the LMW PAH mixture plus B[a]P, all at 10 mg/kg. The LMW PAHs combined with B[a]P significantly increased the promotion and incidence of lung tumors over that of B[a]P alone. The LMW PAHs in the absence of B[a]P did not significantly promote tumors, indicating strong co-promotional activities. We further assessed the effects of these PAHs on other hallmarks of cancer, namely, bronchoalveolar lavage fluid inflammatory infiltrates, pro-inflammatory transcripts, KC protein content, and mRNA expression of the gap junction (Gja1) and epiregulin (Ereg) genes. The LMW PAHs increased the biomarkers of inflammation, decreased Gja1 expression, and increased Ereg expression, all consistent with tumor promotion. This study indicates that non-genotoxic LMW PAHs can contribute to the cancer process and warrants further studies to assess the carcinogenic risks of other LMW PAHs.

High molecular weight polycyclic aromatic hydrocarbon (HMW-PAH) isomers: unveiling distinct toxic effects from cytotoxicity to oxidative stress-induced DNA damage.

Polycyclic aromatic hydrocarbons (PAHs) represent one of the most extensive classes of known carcinogenic and genotoxic compounds widely distributed across the globe. Particularly relevant to ecotoxicological studies is the possible presence of PAHs with molecular weight (MW) 302Da. Since the toxicity of 302Da PAHs differs significantly from isomer to isomer, understanding their relative toxicity is essential for assessing their potential risks to human health. This study investigates the toxic effects of micromolar concentrations of four HMW-PAHs isomers of MW = 302Da, namely dibenzo(b,l)fluoranthene (DB(b,l)F), dibenzo(a,j)fluoranthene (DB(a,j)F), dibenzo(a,l)fluoranthene (DB(a,l)F) and naphtho(1-2j)fluoranthene (N(1-2j)F), upon exposure and metabolic activation in HepG2 cells. Appropriate assays were selected to investigate their potential to disrupt cellular viability and to induce cytotoxicity, apoptosis/necrosis, genotoxicity, and oxidative stress with DNA damage. After 48h of exposure time, DB(a,l)F was the only isomer to reduce cellular viability in a concentration-dependent manner. In all cases, apoptosis was the main mechanism of HepG2 cell death, which could be induced by the significant DNA damage and an increase in 8-hydroxy-2'-deoxyguanosine (8-OHdG) adduct level formation. The highest concentrations of DB(a,l)F tested exhibited the greatest potential to induce HepG2 DNA damage and 8-OHdG formation. Altogether, these facts demonstrate that the distinct arrangements of the atoms in HMW-PAHs isomers can impact on their toxic potential and that DB(a,l)F was the most toxic isomer evaluated in this study. These results shed light on the importance to thoroughly characterize MW302 PAHs to substantiate their human and environmental risk assessments.

Distribution of Polycyclic Aromatic Hydrocarbons and Pesticides in Danjiangkou Reservoir and Evaluation of Ecological Risk.

The Danjiangkou Reservoir is the largest artificial freshwater lake in Asia. This study investigated the spatiotemporal distribution of pesticides and polycyclic aromatic hydrocarbons (PAHs) in the Danjiangkou Reservoir to assess the ecological and human health risks associated with these pollutants. Twenty-three sampling sites in the Danjiangkou Reservoir each collected 23 surface water samples and 23 sediment samples. These samples were analyzed using gas chromatography-mass spectrometry (GC-MS), combined with risk quotient methods and health risk assessment models. The results indicated that the total concentration of PAHs (ΣPAHs) in the surface water ranged from 64.64 to 868.23 ng/L (average 217.97 ± 184.97 ng/L), and they primarily consisted of low molecular weight PAHs, with the compounds with the highest concentrations being naphthalene (10.43-116.97 ng/L), fluorene (22.74-87.61 ng/L), and phenanthrene (26.54-162.86 ng/L). The total concentration of pesticides in the surface water varied between 2.62 and 72.89 ng/L (average 22.99 ± 18.27 ng/L). In the sediment samples, the ΣPAH concentration ranged from 0.01 to 2.93 ng/g (average 0.69 ± 0.94 ng/g), and these predominantly consisted of high molecular weight PAHs, while pesticide concentrations ranged from non-detectable (nd) to 28.46 ng/g (average 7.99 ± 8.53 ng/g), with higher concentrations of malathion (0.62-9.16 ng/g) and chlorpyrifos (10.01-21.38 ng/g). Through risk assessment, it was found that although the risks posed by PAHs and pesticides to human health are very low, the ecological risk assessment indicated that certain PAHs (such as phenanthrene) and organophosphate pesticides (such as malathion and chlorpyrifos) may pose potential threats to aquatic organisms.

PAH contamination in coastal surface sediments and associated bacterial communities

Polycyclic aromatic hydrocarbons (PAH) are semi-volatile, lipophilic, and harmful compounds that can persist for decades in a range of marine environments. There are several marine and soil microorganisms that possess enzymes involved in arene degradation. Here, we analyzed the structure (16S rRNA amplicons) and metabolic potential (inferred using phylogenetic placement) of the bacterial community in surface marine sediments from coastal waters off Concepción, Chile, and describe how microbial community patterns are shaped and altered by PAH contamination. Two depositional zones were identified, a “High PAH” area containing a mix of high and low molecular weight PAH of up to 10,350 ng∑PAH gdw−1 and with high organic matter content; and a “Low PAH” zone mostly characterized by low molecular weight PAH of up to 1810 ng∑PAH gdw−1 and lower levels of organic matter. We identified 53 hydrocarbonoclastic bacteria genera, with eight showing relatively high abundances at High PAH sites, although known PAH degrader clades were also present at Low PAH sites. With potential enzymes inferred in almost all samples, we suggest that breakdown of PAH is widespread in this area, likely resulting from the long history of local PAH emissions that may have promoted a stored microbial capacity for these degradation processes.

Polycyclic aromatic hydrocarbons within the vicinity of a scrap-iron smelting plant: indoor-outdoor and seasonal pattern, source, and exposure risk assessment

ABSTRACT The growing demand for ferrous metals and abundant scrap materials has fueled Nigeria’s scrap-iron smelting industry, leading to hazardous pollutant emissions. This study investigated the concentrations, seasonal and indoor-outdoor variations, origins, and health impacts of polycyclic aromatic hydrocarbons (PAHs) in dust samples around a scrap-iron smelting facility. Analyses of dust samples revealed that high molecular weight PAHs (HMWPAHs) dominated during both seasons, with 5-ring PAHs (34%) contributing most during the rainy season and 3-ring PAHs (36%) during the dry season. Carcinogenic PAHs were more prevalent in the rainy season compared to the dry season. Seven PAH sources were identified, with gasoline combustion being the dominant source during the rainy season and iron and steel production during the dry season. Incremental lifetime cancer risk (ILCR) assessments showed PAH concentrations within safe limits, with dermal contact identified as the primary exposure pathway for both children and adults in the study area.

Combustion Temperature and Soil Organic Horizons Composition Influence on the PAHs Content (Laboratory Experiment Results)

Fire induced changes in the content and composition of polycyclic aromatic hydrocarbons (PAHs) in organic horizons of the boreal zone soils are considered. Experiment of combustion under oxygen deficient conditions were conducted. The organic horizons of soils as peat (sphagnum oligotrophic) and two types of forests (lichen pine and green-moss spruce) were selected. The PAHs content was determined by high-performance liquid chromatography. It was found that combustion conditions, composition of organic horizons and combustibility significantly affect the content and composition of PAHs. The formation of PAHs occurs to a greater extent at 300°C. Compared with the original samples, the content increases from 2.7 to 9.7 times. Compared with the peak PAHs content (in 300°C) samples, a decrease from 5.8 to 33.0 times is found at 500°C. It is likely that the significant decrease in the content of polycyclic aromatic hydrocarbons is due to the decomposition of substances to simpler ones. The ratio of low molecular to high molecular weight PAHs is indicated. The obtained ratio greater than 1.0 can serve as an indicator of pyrogenic origin of polyarenes.

Characterization, source profiles and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in urban dust of 14 Chinese cities

ABSTRACT Data for 16 USEPA priority PAHs were collected in urban dust from 14 cities in China between 2008 and 2022, and concentration, profile composition, and human health risk were investigated. The mean concentration of PAHs was 6.60 mg kg−1, ranging from 2.88 mg kg−1 to 13.88 mg kg−1, and it was higher than other important cities in neighboring countries of China. Among different individual PAHs, mean fluoranthene (Flr) was dominant, accounting for 15.04%, and low molecular weight PAH (LMW) was almost a third of high molecular weight PAH (HMW). The results of PAH composition profiles suggested that the proportion of different rings of PAHs increased in order: 2-ring PAHs (4.40%)< 6-ring PAHs (15.73%)< 3-ring PAHs (17.77%)< 5-ring PAHs (22.54%)< 4-ring PAHs (39.56%). The results of the source appointment suggested that pyrogenic sources and mixed sources, particularly wood, grass, coal, and diesel combustion, were the main sources of PAHs in urban dust. The results of the health risk assessment illustrated that children were more vulnerable to PAHs, and ingestion was the dominant exposure pathway to PAHs (78.152%, 67.519%, 73.206%, and 72.957% of children, adolescents, adults, and the total lifetime cancer risk (TLCR)). PAH pollution in urban dust from different cities in China was a commonly existing phenomenon, but the mean and maximum of TLCR were acceptable according to the standard established by USEPA (10−4). Based on Monte Carlo simulations, body weight (BW) was the most important uncertain input in three age groups (60.75%-91.22% contribution).

Enhanced analysis of PAHs in tea using GC–MS/MS with hydrogen carrier gas

A green multiresidue method for PAH analysis was developed using hydrogen as the carrier gas, avoiding harmful solvents and integrating waste-reducing strategies such as µSPE. The use of hydrogen carrier gas in gas chromatography coupled with tandem mass spectrometry (GC–MS/MS) was explored for the enhanced detection of polycyclic aromatic hydrocarbons (PAHs) in black tea. The study demonstrated that hydrogen, as a carrier gas, offers better chromatographic properties than helium or nitrogen. This leads to improved separation of critical pairs using a short run time method. A fast extraction method using micro solid-phase extraction (µSPE) as a clean-up step was developed to analyze 24 PAHs. The extraction method was optimized using a 4 mL 1:1 mixture of ethyl acetate and acetone. The method was validated and demonstrated good recoveries, ranging from 73 % to 113 % for most PAHs, with lower recoveries (50–63 %) observed for high molecular weight PAHs. Reproducibility was also high, with relative standard deviation (RSD) values below 15 %. Linearity and matrix effects were also evaluated, yielding excellent results, with no PAH exhibiting strong matrix effects. Real sample analysis of black tea from various brands and origins revealed the presence of multiple PAHs with concentrations ranging 9.5–39.2 µg/Kg, some exceeding the maximum residue levels set by the European Union. These findings highlight the need for efficient methodologies to monitor PAHs in food products.

Effects of carbon dioxide addition on soot dynamics in ethylene/air inverse diffusion flames: An experimental and computational analysis

The effects of carbon dioxide (CO2) addition to ethylene (C2H4)/air inverse diffusion flames (IDFs) to the air stream on soot formation characteristics are investigated with the addition ratio of 0–13.64 %. The planar laser-induced fluorescence (PLIF) and planar laser-induced incandescence (PLII) techniques, in conjunction with CoFlame and Chemkin code simulations were utilized to assess the distributions of Polycyclic Aromatic Hydrocarbons (PAHs) and Soot Volume Fraction (SVF). The findings indicate that increasing CO2 addition results in a gradual decrease in the mole fraction of hydroxyl (OH) radicals and flame temperature, accompanied by a reduction of approximately 15 % in the reaction zone height in experimental observations and 19 % in simulations. The inhibition of soot formation is evident through a consistent decline in the normalized total SVF, a decrease in the peak volume fraction of radial soot distribution, and reduced total SVFs observed across different flame sections at varying heights. In the meanwhile, increasing the CO2 doping ratio significantly reduces the peak signal intensity of PAHs, particularly affecting high molecular weight PAHs (A3-A4, A2-A3) with reductions of up to 75.5 %. Furthermore, reductions are noted in the rates of soot inception and subsequent surface growth, accompanied by an upward displacement of the initial inception and growth location. The condensation of PAHs controls the soot surface growth. The thermal and chemical effects of CO2 were differentiated by employing the virtual substance FCO2. The results suggest that the thermal effect of CO2 lowers flame temperature, reduces combustion intensity, and consequently inhibits soot nucleation. The chemical effect of CO2 competes for H radicals through the reverse reaction of CO + OH ≤> CO2+H. This process suppresses the formation and growth of PAHs, consequently leading to a reduction in soot production.

Characterization and health risk assessment of n-alkanes and PAHs in sediments from Shalateen (Halayeb Triangle), Egyptian Red Sea Coast

In this paper, the concentrations, origins, and carcinogenic potential of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) collected from Shalateen sediments (Sh), Red Sea, Egypt were discussed. Individual n-alkanes has fluctuated from a minimum of 17.7 μg/g dw recorded for C-9 at Sh-54 to a maximum of 2.02 × 104 μg/g dw recorded for C-12 at Sh-B1. Total n-alkanes have fluctuated from 252–1.41 × 104 μg/g with a mean of 4.84 × 104 μg/g dw. C-12 had the highest average value, and C-19 had the lowest. The total ΣPAH concentrations in sediments from Shalateen as determined by gas chromatography-mass spectrometry/mass spectrometry (GC-MS/MS) ranged from 43.2 to 270 ng/g dw (averaging 95.2 ng/g dw). Carbon preference index (CPI) values were <1, consistent with the prevalence of even-C alkanes vs. the odd-C homologues. High molecular weight (HMW) PAHs were the most abundant substances affecting the collected samples. The cancer risk ranged from 2.25 × 10−5 to 4.78 × 10−2, indicating a moderate cancer risk associated with PAHs. The primary sources of PAHs in sediments included emissions from burning gasoline and diesel, biomass, and natural gas. The current study is considered one of the most important and unique with regard to the amounts and distributions of n-alkanes and PAHs in sediments along the coasts of Shalateen. It is the first baseline data documentation (GC MS/MS approach) of n-alkanes and PAHs in the Shalateen region.

Diagnostic Ratios and Ecological Risk of Non-carcinogenic Polycyclic Aromatic Hydrocarcarbons (ncPAHs) in Egi Crude Oil Communities, Nigeria

The loadings of PAHs, its diagnostic ratios and ncPAHs at three cluster communities in Egi sub district of Niger-Delta with geographic coordinates of latitude 150 32ʹ 50ʺ N and longitude 60 34ʹ 42ʺ E were ascertained using Gas Chromatography (GC-FID, HP 5890 Series). The diagnostic ratios showed that Obagi had an LMW/HMW ratio of 0.2340, Ibewa's was 0.2222, and Obite's was 0.2549. In Obagi, the proportion of Low Molecular Weight (LMW) PAHs compared to High Molecular Weight (HMW) PAHs was 19%, while in Obite it was 18%, and in the Ibewa cluster it was 20%. The sediments of the Obagi, Obite, and Ibewa cluster sites exhibited a significant abundance of PAHs derived from pyrogenic sources, as evidenced by the presence of LMW/HWM ratios below 1. The identified ncPAHs include: Naphthalene, Acenaphthene, Acenaphthylene, Fluorene, Anthracene, Phenanthrene, Fluoranthene, Pyrene and Benzo(ghi)perylene. According to the results obtained the Obite cluster area exhibited the lowest concentrations (1.503mg/Kg) amongst the ncPAHs, while the Obagi study zone demonstrated the highest concentrations (1.5733mg/Kg). Among the nc(PAHs) examined, benzo (g,h,i) perylene exhibited the highest concentrations (2.086mg/Kg) across all locations, whereas acenaphthylene displayed the lowest concentration (0.123mg/kg) across the three cluster areas. However, none of the three study locations had any ncPAHs that are above the maximum permissible limit. Results from the application of risk quotient models (RQNCs and RQMPCs) to assess the ecological risk of ncPAHs as presented indicated that all the sites where these rivers' sediments were tested had RQNCs values for specific ncPAHs below 1, implying that these ncPAHs pose little or no danger to ecosystems. Also, the RQMPC score is less than 1, it means that the contamination from individual ncPAHs chemicals do not necessitate immediate remediation. Because the RQNCs and RQMPCs for a single PAH molecule are both less than 1, the contamination it generates might be considered low risk. Thus, few measures of control or correction would be required. The ecological risk of non-carcinogenic PAHs using RQMPCs and RQNCs indicated a very negligible risk which could be due to factors like heavy flooding that washed away soil surfaces. Application of Detoxification by chemical reaction technology should be used as future remediation method if there is need.

Passive sampling of polycyclic aromatic hydrocarbons with low-density polyethylene: Equilibration limitations in aqueous suspensions

Polyethylene (PE) and other polymers are widely and successfully used as passive samplers for organic pollutants in the environment. This study provides high-resolution experimental data from batch shaking tests on the uptake, reversibility, and linear equilibrium partitioning of polycyclic aromatic hydrocarbons (PAHs) using two different PE sheets of 30 µm and 80 µm thickness. Kinetics for phenanthrene are well described by a mechanistic first-order model with mass transfer limited by an aqueous boundary layer (with a mean thickness of 170 µm). Equilibration in laboratory batch systems during uptake and desorption is very rapid with characteristic times of 1–2 h but this depends on the boundary condition, e.g., the ratio of PE mass to water volume. Therefore, equilibration of PE in other setups, e.g., in soil slurries or sediment suspensions, may take orders of magnitude longer because the boundary condition for PE changes from finite to infinite bath conditions (soil or sediment particles may keep the concentration in water almost constant). Solid precipitates for high molecular weight PAHs explain partition coefficients below expected values because of kinetic limitations in such a system. Nevertheless, passive sampling can be employed safely if such limitations are considered; furthermore, partition coefficients can be estimated accurately by empirical relationships (e.g., within 0.1 log unit) based on molecular weight, octanol/water partition coefficients, or subcooled liquid solubilities.

Chemical speciation and oxidative potential of PM10 in different residential microenvironments: Bedroom, living room and kitchen

Exposure to particulate matter (PM) and its chemical constituents in residential microenvironments has become a major health concern worldwide. The oxidative potential (OP) has been proposed as a metric for estimating the PM capacity to induce oxidative stress and, consequently, health effects. In the present study, PM10 was daily monitored simultaneously in the bedroom, living room and kitchen of three dwellings for one week in a small town of Portugal, to perform a detailed characterisation of its organic and inorganic constituents and the determination of the OP. Bedrooms (B) were found to be a hotspot of PM10 concentrations (B1 = 22.7 μg m−3; B2 = 19.5 μg m−3; B3 = 68.1 μg m−3). PM10-bound elements varied significantly between microenvironments in all dwellings. Lower molecular weight polycyclic aromatic hydrocarbons (PAHs) were found to be between 14 and 72 times higher than high molecular weight PAHs in bedrooms. The mean volume-normalised OP determined by the dithiothreitol and ascorbic acid assays varied within the 0.01–0.38 nmol min−1 m−3 and 0.03–0.53 nmol min−1 m−3 ranges, respectively. Quinones, oxy-aromatic, aromatic and alkyl-aromatic compounds stood out in bedrooms. Strong and significantly positive relationship between OP and black carbon, Cu and Br were observed, indicating common redox active species mainly associated with traffic emissions. Sr, Fe, Zn and Zr presented higher concentrations in dwelling 3, exhibiting excellent positive correlation with OP, indicating that the Sahara dust intrusion recorded in that house may have contributed to the formation of more redox active species thought to drive antioxidant depletion responses.

Eco-friendly electrospun nanofibers for air filtration enhanced by TiO2 nanoparticles reactive phases for superior capturing the emitted polycyclic aromatic hydrocarbons (PAHs)

The electrospinning nanofibrous filters have attracted much attention owing to their distinctive physicochemical properties. This work focused on designing a novel, straightforward prototype model and fabricating eco-friendly electrospun nanofiber filters as promising air filtration. The synthesized electrospun nanofiber is composed of cellulose acetate (CA) and thermoplastic polyurethane (TPU), which was enhanced by TiO2 nanoparticles to improve the capturing of low, medium, and high molecular weight PAHs. The fabricated CA:TPU/TiO2 and their derivatives were analyzed using FT-IR, XRD, TEM, SEM, TGA, and mechanical characteristics. Different concentrations of TiO2 (2 %, 4 %, 6 %, 8 %) were evaluated. The determinations of PAHs were achieved using gas chromatography-mass spectrometry (GC–MS) with a TG-5MS column. The newly designed prototype has two air pathways with identical specifications; therefore, it could simultaneously evaluate the efficiency of two filters. In Motobas dumpsite (agricultural sources), the results indicated that the highest efficiency of electrospun nanofiber filters was CA:TPU/TiO2 6 %, captured 3041 µg/m3 of total PAHs, and also in the incinerator stack (industrial sources) was CA:TPU/TiO2 6 % captured 9401 µg/m3 of total PAHs. The concentrations of low molecular weight PAHs were greater than the high molecular weight in all sites, and the electrospun CA:TPU/TiO2 was the most effective catalyst for air purification.

Chemical Fingerprinting, PAHs Characterization and Ecological Risks of Carcinogenic PAHs in Surficial Sediments of Egi Crude Oil Producing Communities, Niger-Delta, Nigeria

In order to do PAHs rings analysis, its source identification, extent to which cPAHs present and what kind of ecological risk they pose, the surface sediments from various freshwaters in the Egi crude oil producing cities in the Niger Delta, Nigeria were analyzed. Sediments collected from the research areas for PAHs loadings (in mg/kg dry weight) ranged from 0.020 to 1.790, 0.050 to 1.880, and 0.020 to 1.640, respectively for Obite, Obagi, and Ibewa cluster areas, as measured by gas chromatography-mass spectrometer. In these clusters, the respective average concentration of the three dominant carcinogenic PAHs were Indeno(1,2,3-cd)pyrene (1.170.0mg/kg), Dibenz[a,h]anthrancene (0.870.0 mg/kg), and Dibenz[a,h]anthrancene (1.3670 mg/kg) for Ibewa, Obagi and Obite cluster areas. The findings showed that dominant PAHs rings are of high molecular weight (HMW) PAHs in these sediments are, 5 member rings, which are benzo(b)fluoranthene, Benzo(k)fluoranthene, and Benzo(a)pyrène, and 6-member ring which are, Indeno(1,2,3-cd)pyrene, Dibenz[a,h]anthrancene, and Benzo[ghi] perylene, respectively. Their fingerprints points majorly to pyrogenic sources, combustion of coal, biomass, petroleum, and other related anthropogenic petroleum activities as the primary source of PAHs in the environment. Notably, the RQNCs and RQMPCs for single PAHs molecule are both less than 1, it means the contamination it generates is considered of low ecological risk. Again, the research area experiences frequent flooding, it is believed that this contributes to the low ecological risk of PAHs chemical pollution. Consequently, the area is deemed to be quite safe.