Toxicity Of Polycyclic Aromatic Hydrocarbons Research Articles

Polystyrene microplastics alleviate adverse effects of benzo[a]pyrene on tissues and cells of the marine mussel, Mytilus galloprovincialis

As two major ubiquitous pollutants, microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) coexist in the marine environment. However, the role of MPs in altering the toxicity of PAHs to marine organisms is poorly understood. We therefore investigated the accumulation and toxicity of benzo[a]pyrene (B[a]P, 0.4 nM), in the marine mussel Mytilus galloprovincialis over a 4-day of exposure with or without the presence of 10 μm polystyrene microplastics (PS MPs) (10 particles/mL). The presence of PS MPs significantly decreased B[a]P accumulation in soft tissues of M. galloprovincialis by approximately 6.7%. Single exposure of PS MPs or B[a]P decreased the mean epithelial thickness (MET) of digestive tubules and enhanced reactive oxygen species (ROS) levels in haemolymph, while upon co-exposure the adverse impacts were alleviated. Real-time q-PCR results showed that most selected genes involved in stress response (FKBP, HSP90), immune (MyD88a, NF-κB) and detoxification (CYP4Y1) were induced for both single exposure and co-exposure. The co-presence of PS MPs down-regulated the mRNA expression of NF-κB in gills compared with of B[a]P alone. The uptake and toxicity reductions of B[a]P might result from the decrease of its bioavailable concentrations caused by the adsorption of B[a]P by PS MPs and the strong affinity of B[a]P to PS MPs. Adverse outcomes for the co-existence of marine emerging pollutants under long-term conditions remain to be further validated.

Health Risk Assessment of PAHs from Estuarine Sediments in the South of Italy

Increased concerns about the toxicities of Polycyclic Aromatic Hydrocarbons (PAHs), ubiquitous and persistent compounds, as well as the associated ecotoxicology issue in estuarine sediments, have drawn attention worldwide in the last few years. The levels of PAHs in the Sele, Sarno, and Volturno Rivers sediments were evaluated. Moreover, the cancerogenic risk resulting from dermal and ingestion exposure to PAHs was estimated using the incremental lifetime cancer risk (ILCR) assessment and the toxic equivalent concentration (TEQBaP). For Sele River, the results showed that the total PAH concentration ranged from 632.42 to 844.93 ng g-1 dw, with an average value of 738.68 ng g-1 dw. ∑PAHs were in the range of 5.2-678.6 ng g-1 dw and 434.8-872.1 ng g-1 dw for the Sarno and Volturno River sediments, respectively. The cancerogenic risk from the accidental ingestion of PAHs in estuarine sediments was low at all sampling sites. However, based on the ILCRdermal values obtained, the risk of cancer associated with exposure by dermal contact with the PAHs present in the sediments was moderate, with a mean ILCRdermal value of 2.77 × 10-6. This study revealed the pollution levels of PAHs across the South of Italy and provided a scientific basis for PAH pollution control and environmental protection.

Emission factors for polycyclic aromatic hydrocarbons from laboratory biomass-burning and their chemical transformations during aging in an oxidation flow reactor

Atmospheric polycyclic aromatic hydrocarbons (PAHs) can be emitted from different combustion sources including domestic biomass burning, internal combustion engines, and biomass burning (BB) in wild, prescribed, and agricultural fires. With climate warming and consequent global increases in frequency and severity of wildfires, BB is a dominant source of PAHs emitted into the atmosphere.In this study, six globally and regionally important and representative fuels (Alaskan peat, Moscow peat, Pskov peat, eucalyptus, Malaysian peat, and Malaysian agricultural peat) were burned under controlled conditions in the combustion chamber facility at the Desert Research Institute (DRI, Reno, NV, USA). Gas- and particle-phase BB emissions were aged in an oxidation flow reactor (OFR) to mimic five to sevendays of atmospheric aging. To sample gas- and particle-phase BB emissions, fresh and OFR-aged biomass-burning aerosols were collected on Teflon-impregnated glass fiber filters (TIGF) in tandem with XAD resin media for organic carbon speciation. The objectives of this study were to i) quantify the emission factors for 113 PAHs emitted from the combustion of the six selected fuels, ii) characterize the distribution of PAH compounds between gas and particle phases for these fuels, iii) identify the changes in PAHs during OFR-aging, and iv) evaluate toxicity potential with characterized compounds.We found that combustion emissions of gas-phase PAHs were more abundant (>80 % by mass) than particle-phase PAHs, for emissions from all combusted fuels. The mass fraction of substituted napthalenes in Moscow peat and Malaysian peat emissions were ∼70 % & 84 %, respectively, whereas in Eucalyptus the same fraction was <50 %, which indicates that these substituted compounds can be used as tracers for peat emissions. Mass concentrations of gas- and particle-phase PAHs were reduced by ∼70 % after OFR oxidation. However, the understanding of the fate of PAHs during OFR oxidation requires further investigations. Our results also indicate that the PAH toxicity of BB samples would be underestimated by 10–100 times if only the BaPeq for the 16 US EPA priority PAHs in the particle phase are included.

The recalcitrance and potential toxicity of polycyclic aromatic hydrocarbons within crude oil residues in beach sediments at the BIOS site, nearly forty years later

The Arctic is a unique environment characterized by extreme conditions, including daylight patterns, sea ice cover, and some of the lowest temperatures on Earth. Such characteristics in tandem present challenges when extrapolating information from oil spill research within warmer, more temperate regions. Consequently, oil spill studies must be conducted within the Arctic to yield accurate and reliable results. Sites of the Baffin Island Oil Spill (BIOS) project (Cape Hatt, Baffin Island, Canadian Arctic) were revisited nearly 40 years after the original oil application to provide long-term monitoring data for Arctic oil spill research. Surface and subsurface sediment samples were collected from the intertidal zone of the 1981 nearshore oil spill experiment (Bay 11), from 1980 supratidal control plots (Crude Oil Point) and 1982 supratidal treatment plots (Bay 106). Samples were analyzed for Polycyclic Aromatic Hydrocarbons (PAHs) and alkylated homologues via Gas Chromatography – Mass Spectrometry (GC-MS). Our results suggest that total mean concentrations of all measured PAHs range from 0.049 to 14 mg/kg, whereas total mean concentrations of the 16 US EPA priority PAHs range from 0.02 to 2.1 mg/kg. The relative proportions of individual PAHs were compared between sampling sites and with the original technical mixture. Where available, percent loss of individual PAHs was compared with data from samples collected at the BIOS site, in 2001. All three sites featured samples where concentrations of various priority PAHs exceeded the established Interim Marine Sediment Quality Guidelines. All supratidal samples contained potentially toxic levels of PAHs. Even after nearly four decades of weathering, the recalcitrant crude oil residues remain a potential hazard for the native organisms. Continued monitoring of this unique study site is crucial for establishing a timeline for oil degradation, and to observe a reduction in toxicity over time.

Gas Particle Partitioning of PAHs Emissions from Typical Solid Fuel Combustions as Well as Their Health Risk Assessment in Rural Guanzhong Plain, China.

Air pollutants from the incomplete combustion of rural solid fuels are seriously harmful to both air quality and human health. To quantify the health effects of different fuel-stove combinations, gas and particle partitioning of twenty-nine species of polycyclic aromatic hydrocarbons (PAHs) emitted from seven fuel-stove combinations were examined in this study, and the benzo (a) pyrene toxicity equivalent (BaPeq) and cancer risks were estimated accordingly. The results showed that the gas phase PAHs (accounting for 68-78% of the total PAHs) had higher emission factors (EFs) than particulate ones. For all combustion combinations, pPAHs accounted for the highest proportion (84.5% to 99.3%) in both the gas and particulate phases, followed by aPAHs (0.63-14.7%), while the proportions of nPAHs and oPAHs were much lower (2-4 orders of magnitude) than pPAHs. For BaPeq, particulate phase PAHs dominated the BaPeq rather than gas ones, which may be due to the greater abundance of 5-ring particle PAHs. Gas and particle pPAHs were both predominant in the BaPeq, with proportions of 95.2-98.6% for all combustion combinations. Cancer risk results showed a descending order of bituminous coal combustion (0.003-0.05), biomass burning (0.002-0.01), and clean briquette coal combustion (10-5-0.001), indicating that local residents caused a severe health threat by solid fuel combustion (the threshold: 10-4). The results also highlighted that clean briquette coal could reduce cancer risks by 1-2 orders of magnitude compared to bulk coal and biomass. For oPAH, BcdPQ (6H-benzo(c,d)pyrene-6-one) had the highest cancer risk, ranging from 4.83 × 10-5 to 2.45 × 10-4, which were even higher than the total of aPAHs and nPAHs. The dramatically high toxicity and cancer risk of PAHs from solid fuel combustion strengthened the necessity and urgency of clean heating innovation in Guanzhong Plain and in similar places.

V-Cu bimetallic oxide supported catalysts for synergistic removal of toluene and NOx from coal-fired flue gas: The crucial role of support

It is a major challenge to achieve effective synergistic reduction of NOx and VOCs in coal-fired flue gas under complex working conditions. In this work, V-Cu bimetallic oxide catalysts with different supports were designed. V1-Cu5 bimetallic oxide supported on TiO2 showed significantly higher activity for simultaneous toluene oxidation and NOx reduction than that supported on ZSM-5, SiO2 and γ-Al2O3. Meanwhile, it exhibited excellent stability and anti-poisoning performance, and could block the formation of toxic polycyclic aromatic hydrocarbons in by-products. Compared with ZSM-5, SiO2 and γ-Al2O3, TiO2 as support was conducive to the formation of abundant acidic sites and oxygen vacancies. In addition, the strong interaction between the metal active sites and TiO2 accelerated the electron transfer from Cu to adsorbed O2, thus promoting the formation of active O2−. This work can provide guidance for the development of catalysts designed for the simultaneous catalytic removal of NOx and VOCs.

A new approach to neutralize the toxic effect of polycyclic aromatic hydrocarbons on the example of 9,10-dimethylanthracene: A kinetic aspect

The rate constants of the Diels-Alder reaction of 9,10-dimethylanthracene with tetracyanoethylene, 4-phenyl-1,2,4-triazoline-3,5-dione, maleic anhydride, and N-phenylmaleimide in solution have been determined. It was found that tetracyanoethylene and 4-phenyl-1,2,4-triazoline-3,5-dione can react instantly with 9,10-dimethylanthracene, which is a representative of toxic polycyclic aromatic hydrocarbons. The kinetics of the reactions of 9,10-dimethylanthracene with tetracyanoethylene and N-phenylmaleimide in the solid phase without solvent has been studied. The rate of these reactions in the solid phase appeared to be significantly lower than that of the same reactions in the solution, since the rate of reactions in the solid phase strongly depends on the rate of renewal of contacts between the reagent molecules. The data obtained can be useful for the purification of water bodies and soil from polycyclic aromatic hydrocarbons.

Polycyclic Aromatic Hydrocarbons (PAHS) Levels and Toxicity in Herbal Teas Marketed in Malaysia using Quechers and GC-FID

In line with the growing health trend in Malaysia, more consumers drink herbal tea for medicinal benefits. However, herbal tea products could be contaminated with polycyclic aromatic hydrocarbons (PAHs) from various production sources. There is a little study focused on the detection of PAHs in herbal tea species distributed in Malaysia. This study was performed to investigate PAHs content and toxicity in selected commercial herbal teas in Malaysia. A total of seven different Malaysian herbal tea samples were extracted using QuEChERS extraction method and the contamination level of PAHs were evaluated using gas chromatography (GC) with a flame ionization detector (FID). The total content of 10 PAHs (∑10PAHs) in the herbal tea samples ranged from 2.53 to 9.39 µg/kg. Acenaphthene, fluorene, phenanthrene and anthracene were the most abundant compounds with 53% contribution of all PAHs content. All tested herbal teas species showed low toxic equivalency (TEQ) values ranging from 0.0027 to 0.1148. The least contaminated samples were Strobilanthes crispus, Senna alata, Orthosiphon aristatus, Clinacanthus nutans, and Stevia rebaudiana.

The utilization of hydrophobic wax beads for the absorption of gas particles: A one health approach to address fuel spills in lake Muskoka

The prevalence of recreational, motorized boating on freshwater lakes has significantly increased in the last decades. Consequently, there has been an increase in fuel spills and an accumulation of toxic polycyclic aromatic hydrocarbons (PAHs), which can have significant adverse health impacts on humans, non-human animals, and the environment. As previous initiatives to clean up spills have often been invasive, tough to follow, and environmentally intolerant, a One Health approach is necessary to address this issue. This article proposes a cost-effective and environmentally friendly solution to remove PAHs from Lake Muskoka in Ontario, Canada. The solution, based on principles of hydrophobic interactions, employs Carnauba wax beads in mesh cages to absorb PAHs from the water. This natural absorbent technology could lead to improvements in the overall quality of life and health of humans, non-human animals, and the environment. If deemed successful, this technology may be adapted to other bodies of water to mitigate the damage of PAHs on freshwater ecosystems.

Assessment of environmental risk related to the polycyclic aromatic hydrocarbons (PAH) in the sediments along the eastern Adriatic coast

Polycyclic aromatic hydrocarbons (PAH) were investigated in the sediments at 24 locations in the coastal area of Adriatic Sea. Total PAH concentrations ranged from 14,98 to 26145,62 µg kg-1, with the highest levels determined in the sediments of Šibenik Bay and the lowest in the sediment near Island of Pag. Unsubstituted PAH were prevailing PAH group in the sediments from the Šibenik Bay and in the Coastal area, while methyl-substituted PAH were dominant group in the sediments of the Kaštela Bay. In order to estimate the possible toxicological significance of PAH concentrations, Sediment Quality Assessment was done according to three different sets of sediment quality guidelines. A high environmental risk was calculated for each station in Šibenik Bay; for the station in vicinity of the Industrial port of Split and for the two stations in Coastal zone. Low environmental risk was determined in less urbanised areas such as Island of Pag. Sediment extracts were further analysed for acute toxicity by measurements of decrease in bioluminescence upon exposure to sediment extracts. Obtained results show disagreement between sediment toxicity predicted upon PAH levels in sediment and experimentally obtained sediment toxicity. Sediment extracts in which low PAH levels were measured showed high acute toxicity indicating that concentrations of PAH alone are a poor indicator of sediment toxicity. Correlation analysis between concentrations of specific PAH compounds and toxicity revealed the strongest association between acute sediment toxicity and sulphur-containing PAH suggesting the S-PAH should be considered in sediment toxicity assessment.

Comparative Toxicity of 3-5 Ringed Polycyclic Aromatic Hydrocarbons to Skeletal Development in Zebrafish Embryos and the Possible Reason.

Polycyclic aromatic hydrocarbons (PAHs) are pervasive pollutants in the environment. To compare the developmental toxicity of PAHs with different ring numbers to fish embryos, benzo(a)pyrene (BaP), pyrene (Pyr) and phenanthrene (Phe) were selected as the representatives of 3, 4 and 5-ringed PAHs, and fertilized embryos of zebrafish (Danio rerio) were exposed to 5 nM PAHs for 72h. The PAH-treated embryos showed defects in craniofacial cartilage. The order of toxicity to the development of craniofacial cartilage was Phe > Pyr > BaP. The transcription of genes related to the development of craniofacial cartilage was downregulated. The GC-MS/MS detection showed that bioaccumulation of BaP in the exposed embryos was two orders of magnitude lower than that of Phe and Pyr. It is suggested that the more uptake and accumulation of Phe and Pyr could be one of the reasons for their greater toxicity to development in early stage embryos.

Effect of n-Butanol Addition to Diesel Fuel on Reduction of PAH Formation and Regulated Pollutants

The primary motivation of this paper is to report the effects of n-butanol addition (5, 20 and 35% by volume) to diesel fuel on regulated and polycyclic aromatic hydrocarbon (PAH) emissions of a diesel engine. PAH samples were quantified using rigorous analytical chemistry procedures to determine total PAHs, PAH dispersion and PAH toxicity. In comparison with diesel fuel, all n-butanol blends (DBu5, DBu20, and DBu35) reduced nitrogen oxides (NOx) emissions by 6.77%, 9.59%, and 20.08% and total PAH emissions by 66.86%, 75.33%, and 80.98%. In terms of the relative distribution of PAHs, a significant decrease was recorded in higher cyclic PAHs such as Pyrene, Benzo[a]anthracene, Chrysene, Benzo[k]floranthene, Benzo[a]pyrene for all blends. Similarly, the amount of the toxicity of the PAH emissions also decreased by 11.66%, 87.53%, and 67.28% with DBu5, DBu20 and DBu35 blends, respectively. With the addition of n-butanol to the diesel fuel, total PAH emissions were detected below the Occupational Safety and Health Administration’s (OSHA)-Permissible Exposure Level. Overall, it was demonstrated that n-butanol addition to diesel fuel significantly reduced PAH formation which is helpful to prevent wet stacking, and prolong the operating time of the diesel engine especially at low loads or cold operating conditions.

Sedimentary PAH and oxidative stress biomarkers responses on Namalycastis abiuma (Polychaeta: Nereididae) from an urbanized Amazon estuary

Contamination by polycyclic aromatic hydrocarbons (PAH) in sediments and oxidative stress biomarkers responses (glutathione-S-transferase activity—GST and lipoperoxidation—LPO) on the polychaetes Namalycastis abiuma were screened along the urbanized margin of the Guajará Estuary, Brazilian Amazon coast, during dry and rainy seasons. Total 16 priority PAH concentrations ranged from 17 to 386 ng g−1 dry sediment, with higher values during the dry season. High molecular weight PAHs predominated during dry season and were probably originated from fossil fuel burning. Increased naphthalene and anthracene concentrations were noted when the maximum river flow was recorded and suggest diffuse sources from drainage of contaminated surfaces. Ecotoxicological PAH risks were low according to international sediment quality indices. Nevertheless, PAH toxicity equivalency was around 10-fold higher nearer the oil terminal than alongside the estuary. Highest GST activities at the oil terminal and industrial sites coincided with the rainy season, and combined with hydrochemical and sedimentary conditions thought to promote PAH bioavailability and a prolonged toxicant exposure. LPO approached similar levels in both seasons, suggesting that enzymatic activities were sufficient to uphold the prooxidants exposure. This result indicates that the overall estuarine condition exerts subtle oxidative stress on a keystone species and matches the low PAH ecotoxicological risks. Depositional margins within the mangrove areas and port operation are susceptible to an enhanced PAH accumulation and need special surveillance.

Upgrading and PAHs formation during used lubricant oil pyrolysis at different heating modes

Recycling used lubricant oil (ULO) to produce valuable products through pyrolysis is a flexible and efficient method. Presently, the mechanisms of oil conversion and polycyclic aromatic hydrocarbons (PAHs) formation during ULO pyrolysis at different thermal conditions were poorly explored. In this study, ULO pyrolysis at different heating modes (slow: 10 °C min−1, medium: ∼10,00 °C min−1, fast: >10000 °C min−1) were conducted at the temperature range of 400–700 °C. Extensive analyses on the chemical compositions and carbon number distributions of pyrolytic products were conducted to illustrate the mechanisms of ULO evolution and the formation of PAHs. Increasing temperature or heating rate can lead to more gas but less liquid production. The high temperature at fast heating mode can greatly promote the aromatization of pyrolytic oil. Various types of valuable products, such as base oil, fuel, and chemical feedstock, can be obtained at different heating rate conditions. More than 98% of PAHs produced from ULO pyrolysis were gathered in the liquid phase. Naphthalene, phenanthrene, and pyrene were the primary PAH species in both the liquid and gaseous products. Elevating the heating rate can lead to more PAH production and the enrichment of more toxic (5-/6-ring) PAHs in pyrolytic oil. Comparatively, distillation dominated in the slow pyrolysis, and chemical reactions of cracking and recombination occurred markedly at the medium and fast heating modes for both the ULO evolution and PAHs formation.

Effect of diesel and propanol blends on regulated pollutants and polycyclic aromatic hydrocarbons under lean combustion conditions

AbstractAlcohols such as n‐propanol and diesel fuel can be mixed to increase the rate of bioalcohol utilization while reducing harmful pollutants. Examination of exhaust emissions from diesel engines, in terms of both regulated pollutants and unregulated polycyclic aromatic hydrocarbons (PAHs), is very important to the environment, public health, and engine durability. For this purpose, in this study, diesel blends with various n‐propanol concentrations (5%, 20%, and 35% by volume) were evaluated in a diesel engine. Regulated emissions were measured using a standard 5‐gas analyzer and polycyclic aromatic hydrocarbons were detected and quantified using gas chromatography–mass spectrometry (GC–MS). The effect of blended fuels on PAH formation (total PAHs, PAH distribution, and PAH toxicity) was examined in detail and compared with baseline diesel. Nitrogen oxide (NOx) emissions were reduced by 18.30% with higher n‐propanol concentrations. The addition of n‐propanol to diesel decreased total PAHs by as much as 71.20%. The fuel blend with a 20% n‐propanol concentration stood out with a maximum reduction of 91.23% in the toxicity of PAHs. In addition, n‐propanol led to a substantial decrease in the distribution of high ring aromatic compounds. Overall, it was demonstrated that n‐propanol is an effective additive to not only reduce the total PAH emissions and toxicity but also heavier PAHs which are more carcinogenic and cause a greater risk of the wetstacking issues for engines under cold operating or low load conditions.

Reduction of polycyclic aromatic hydrocarbons concentrations in smoked guinea fowl (Numida meleagris) meat using gamma irradiation

ABSTRACT This study investigated the effect of gamma irradiation on polycyclic aromatic hydrocarbons (PAHs) contents in smoked guinea fowl meat. Guinea fowls were processed, smoked and irradiated at 0, 2.5, 5.0 and 7.5 kGy. PAHs were extracted and their concentrations determined using Gas Chromatography-Mass Spectrometer. Health risk of the PAHs to humans was also estimated. Sixteen PAHs were detected in the smoked meat with concentrations ranging from 0.002 to 9.221 μg/kg. B[a]P recorded the highest value of 9.221 μg/kg (0 kGy) and the least value of 0.057 μg/kg for the meat samples. Irradiation significantly reduced the PAHs concentrations and their carcinogenic derivatives. Health risk estimation suggested that the levels of PAHs in the treated smoked meats pose no dietary intake risks. Gamma irradiation has the potential to minimize the toxicity of carcinogenic PAHs in smoked guinea fowl meat, thereby increasing export and enhancing the future economical marketing of this food product.

Combined effects of engine characteristics and fuel aromatic content on polycyclic aromatic hydrocarbons and toxicity

ABSTRACT Polycyclic aromatic hydrocarbons (PAHs) are harmful compounds because of their toxicity, adverse effects on human health, and threats to engine components (i.e. wetstacking). With the increased use of renewable fuels, it is imperative that the formation of PAHs be examined, in detail, with respect to the combustion characteristics and aromatic content of biofuels used in diesel engines. Since biodiesel is free of aromatic content in its chemical structure, this study provides comparative assessments of the PAHs, toxicity and regulated emissions of biodiesel (B100) and diesel fuel (D100), based on the fuel aromaticity and engine characteristics when used in two diverse engines. Results indicate that the use of B100 in both engines reduced total PAH emissions by 48.02% − 49.36% and PAH toxicity by 83.49% − 84.8% as compared to diesel fuel, which is a clear indication of the importance of the aromatic content of the base fuel on PAH formation and toxicity (i.e. aromatic-free fuel produces less PAH than diesel with high aromaticity). The aromatic ring distribution associated with B100 exhaust consisted of 50% two, 34% three and 16% four aromatic rings for the Onan engine, and 53% two, 32% three and 15% four aromatic rings for the Kubota engine. Benzo[a]pyrene, a five-ring PAH with great carcinogenic threat, was eliminated in both engines as a result of using B100. To demonstrate the significance of combustion processes on PAH formation, performances of the engines were compared and it was determined that the Kubota engine performed better for both fuels in reducing PAH emissions, due to such features as its injection system and combustion chamber design as compared to the Onan engine. Therefore, it has been concluded that PAH emissions and toxicity strongly depend on both the aromatic content and the combustion processes, as aromatic-free biodiesel significantly decreased PAHs along with additional reduction in PAHs and toxicity depending on the structural specifications of the diesel engine. Based on this study, aromaticity has been determined to be more effective than the type of engine in use for PAH reduction.

Pahs emission characteristics and the mitigation in the valuable products from used mineral oil thermolysis recycling

Pyrolysis of used mineral oil (UMO) to produce various valuable products is a flexible and efficient way for UMO recycling. Along with the preferred pyrolytic products, toxic polycyclic aromatic hydrocarbons (PAHs) may also be generated. To mitigate the PAHs emission during UMO pyrolysis, an understanding of emission characteristics and formation mechanism of PAHs is needed. In this work, four used minerals (engine, hydraulic, turbine, transformer) oil and three base oil were pyrolyzed at 600 °C at different heating modes (slow: 10 °C min−1, medium: ∼1000 °C min−1, fast: greater than10000 °C min−1) under N2/CO2 atmosphere. The results show that a higher heating rate can lead to more gas but less oil production. At different heating modes, PAHs emission factors change markedly and are in the range of 34.63–1492.85 ug g−1, among which more than 92 % of PAHs are enriched into pyrolytic oil. Naphthalene, phenanthrene and pyrene are the first three PAHs species in the gaseous product. The mechanism of evaporation and chemical evolution control PAHs formation for the SP process and FP process, respectively. PAHs formation is related to both the naphthene and aromatic contents of UMO, and the contribution of aromatics is about fourfold of the naphthenes. In the CO2 atmosphere, more liquid product and ∼ 33 % less PAHs formation can be realised due to the depressed dehydrogenation reaction.

Source Identification, Toxicity, and Persistence of PAHs in Sediment Core from a Natural Protected Area in Mexico

Sediment cores maintain a historical record of the various sources of polycyclic aromatic hydrocarbons (PAHs). In 2020, one sediment core was collected within the oyster farming area of the Pom–Atasta lagoon system and the Terminos lagoon. A total of 16 PAH compounds were analyzed to identify the historical patterns of PAH inputs and the relationship with sediment materials. The core was classified into three strata at depths of 0.0–0.2 m, 0.2–0.6 m, and 0.6–1.1 m, in which the high content of silt–sand, organic matter, and carbonates indicates a system of high energy and productivity. The hydrology and characteristics of the sediment suggest a free access of adsorbed PAHs to the study area, mainly of pyrolytic origin. The concentration of ∑PAHs decreases from the surface (527.0 ng g−1 dw) to a greater depth (75.7 ng g−1 dw), which corresponds to 60% of the HMW (high molecular weight) of the total PAHs as combustion products at low temperatures, while LWM-PAH (low molecular weight) inputs are from discharges of petroleum products. The core sediments showed a low probability of toxicity quotient of 9%. The analysis of the carcinogenic toxic equivalent (TEQcarc) in each section of the core was variable, decreasing with the depth from 107.91 ng TEQ g−1 dw to 57.65 ng TEQ g−1 dw, with the compounds benzo(a)pyrene (53.55 ng TEQ g−1 dw) and dibenzo(a,h) anthracene (29.2 ng TEQcarc g−1 dw) having the highest TEQcarc. The anthropogenic activities around the study area may increase the carcinogenic and mutagenic risk to human health. However, in the present study, the low toxic carcinogenic equivalents (TEQBaP) and mutagenic equivalents (MEQBaP) indicate a low probability of sediment toxicity. The ecosystem could be under constant threat from increasing anthropogenic activity; therefore, monitoring programs for the conservation of these ecosystems and oyster farms should be considered.

Concentration and Bioaccumulation of Toxic Metals and Polycyclic Aromatic Hydrocarbons in Soil and Lumbricus Terrestris in Kolo Creek, Niger Delta, Nigeria

The concentration of toxic metals and polycyclic aromatic hydrocarbons (PAHs) in soil, and their bioaccumulation in Lumbricus terrestris in areas around Kolo Creek, Niger Delta, Nigeria were evaluated in this study. 12 soil samples were collected from 4 sites, while Lumbricus terrestris were also collected from areas where soil samples were obtained. Toxic metals were extracted using aqua regia and quantified with a flame atomic absorption spectrophotometer. Extraction of PAHs was achieved by liquid-liquid soxhlet extraction, and quantified with a gas chromatograph-mass spectrometer. The bioaccumulation factor (BAF) for both toxic metals and PAHs were calculated. The results obtained in this study showed that the concentration of all studied toxic metals were within their respective regulatory limits in soil. The BAF for all toxic metals were less than 1 in all sites, indicating minimal bioaccumulation in Lumbricus terrestris. The Ʃ16 PAHs ranged from 7.30 to 77.7 mg kg-1 and 1.10 to 4.75 mg kg-1 in soil and Lumbricus terrestris across the 4 sites, respectively. The BAF values for individual PAHs were less than 1 in all sites, which indicated that PAH congeners were either not bioaccumulated or accumulated PAH congeners were metabolized. Hence, analysis of PAHs metabolites in Lumbricus terrestris is recommended.