Pyrolytic Polycyclic Aromatic Hydrocarbons Research Articles

Concentration of polycyclic aromatic hydrocarbons (PAHs) in sediments from the Tampamachoco lagoon, Tuxpan River mouth, Gulf of Mexico

Polycyclic aromatic hydrocarbons (PAHs) are organic chemicals that consist of carcinogenic and mutagenic properties, which are considered as high-priority persistent organic pollutants (POPs). Their source is due to an incomplete burning of fossil fuels and organic materials. In the present study, the distribution and concentrations of 16 priority PAHs in sediments of the Tampamachoco lagoon and Tuxpan River estuary at the Gulf of Mexico were analyzed. The surface sediment samples were collected during the dry (March–June) and rainy (August–November) seasons. PAHs were analyzed by means of a gas capillary chromatography-FID. In dry season, the average concentration of PAHs in sediments was 860 ± 390 ng/g, and in rainy season, it was 1140 ± 450 ng/g. During both seasons, the total concentration of chrysene was high and a domain of the compounds with 4 benzene rings was observed. The source of PAHs was investigated in 78.6% of the lagoon sites. 45.5% revealed indicators of a mixed origin between pyrolytic and petrogenic sources, and 36.4% was petrogenic, and the remaining 18.2% was pyrolytic PAHs.

Simulation Experiment Study on Impacting the δD Value of Aromatic Compounds

Little is known about the effects of sedimentary environment and maturity on δD values of aromatic compounds deposited in geological bodies. Our simulation experiments showed that the δD value of pyrolytic polycyclic aromatic hydrocarbons (PAHs) was significantly different between the studied samples from high and low latitude regions. Comparative studies showed that the δD values of PAHs produced by pyrolysis were related to those of water in the two regions. With increasing maturity, the δD value of the PAHs becomes higher. Additionally, it was observed that some PAHs exhibited a propensity to increase the δD value upon demethylation. The thermodynamic fractionation of hydrogen isotopes between the PAHs produced by pyrolysis and both the n-alkanes and methane produced by pyrolysis indicated that the hydrogen isotopic value of the PAHs was higher than that of the n-alkanes or methane. The long-chain alkylbenzene produced by pyrolysis has a higher mean δD value compared with the n-alkanes produced by pyrolysis, but it is lower than that of the PAHs in the same sample. The lowest δD value among the aromatics was found in the ring A monoaromatic steroids produced by pyrolysis. The low δD values of these steroids should originate from isotopic fractionation during isoprenoid lipid biosynthesis.

Sorption of benzo(a)pyrene and of a complex mixture of petrogenic polycyclic aromatic hydrocarbons onto polystyrene microplastics

Microplastics (MPs) largely occur in aquatic ecosystems due to degradation of larger plastics or release from MP-containing products. Due to the hydrophobic nature and large specific surface of MPs, other contaminants, such as polycyclic aromatic hydrocarbons (PAHs), can potentially sorb onto MPs. Several studies have addressed the potential impact of MPs as vectors of PAHs for aquatic organisms. Therefore the role of MPs as sorbents of these compounds should be carefully investigated. The present study aimed to determine the sorption capacity of benzo(a)pyrene (B(a)P), as a model pyrolytic PAH, to polystyrene (PS) MPs of different sizes (4.5 and 0.5 μm). In addition, the sorption of PAHs present in the water accommodated fraction (WAF) of a naphthenic North Sea crude oil to 4.5 μm MPs was also studied as a model of a complex mixture of petrogenic PAHs that could appear in oil-polluted environments. The results indicated that 0.5 μm MPs showed higher maximum sorption capacity (Qmax) for B(a)P (145–242.89 μg/g) than 4.5 μm MPs (30.50–67.65 μg/g). From the WAF mixture, naphthalene was sorbed at a higher extent than the other PAHs to 4.5 μm MPs but with weak binding interactions (Kf = 69.25 L/g; 1/n = 0.46) according to the analysis of the aqueous phase, whereas phenanthrene showed stronger binding interactions (Kf = 0.24 L/g; 1/n = 0.98) based on the analysis of the solid phase. Sorption of PAHs of the complex WAF mixture to 4.5 μm MPs was relatively limited and driven by the hydrophobicity and initial concentration of each PAH. Overall, the results indicate that sorption estimations based solely on the analysis of the aqueous phase could overestimate the capacity of MPs to carry PAHs. Therefore, controlled laboratory assays assessing the “Trojan Horse effect” of MPs for aquatic organisms should consider these findings in order to design accurate and relevant experimental procedures.

Wildfire response to rapid climate change during the Permian-Triassic biotic crisis

Char and polycyclic aromatic hydrocarbons (PAHs), which can serve as proxies for wildfire frequency and/or intensity, are widely present in Permian-Triassic boundary (PTB) strata, providing information on volcanism or on climatic control of fuel availability (linked to vegetation type and density) or combustibility (linked to aridity). Here, we present evidence to separate temporal from geographic signals of climate impact on wildfire during the Permian-Triassic (P-Tr) transition. Geographically, char and pyrolytic PAHs for wildfire are concentrated in temperate and tropical regions and show a connection with forest distribution as reflected by occurrences of Upper Permian coals. Temporally, the subtropical terrestrial Dalongkou section of northwestern China provides evidence of two intervals of increased pyrolytic PAHs of combustion origin. The first interval was linked to climatic hyperwarming during the latest Permian, whereas the second interval was associated with rapid climatic drying, as recorded by spore-to-pollen ratios (S/P), during the P-Tr transition. This record suggests that rapid climate change during the P-Tr transition increased wildfire frequency. A climate link is also shown by turnovers of ostracods, conchostracans, and charophytes in conjunction with greater wildfire frequency. The trigger for enhanced wildfires and biotic changes is inferred to have been volcanically induced climatic warming and aridification. Our data thus document important links between wildfires, climate change, volcanism, and mass extinction during the P-Tr transition.

Intensive peatland wildfires during the Aptian–Albian oceanic anoxic event 1b: Evidence from borehole SK-2 in the Songliao Basin, NE China

The Cretaceous has been considered a “high-fire” world accompanied by widespread by-products of combustion in the rock record. The mid-Cretaceous oceanic anoxic event 1b (OAE1b) is marked by one of the major perturbations in the global carbon cycle characterized by deposition of organic-rich sediments in both marine and terrestrial settings. However, our understanding is still limited on changes in wildfire activity during OAE1b period. Here, we carried out a comprehensive analysis, including organic carbon isotope (δ13Corg), total organic carbon (TOC), coal petrology, trace elements, and pyrolytic polycyclic aromatic hydrocarbons (pyroPAHs), of coal seams of the middle Aptian to early Albian Shahezi Formation from borehole SK-2 in Songliao Basin, Northeast China. Two negative δ13Corg excursions in the Shahezi Formation can be corresponded with the 113/Jacob and Kilian sub-events of OAE1b. Moreover, the intensive peatland wildfires have been identified during the sub-event periods of OAE1b based on the co-occurrence of high abundance of charcoal and pyroPAHs at that time. In addition, Sr/Ba, Sr/Cu and Sr/Rb ratios demonstrate that enhanced peatland wildfires were controlled by dryer climate conditions owing to episodic northward migration of arid zones in East Asia related with rising global temperature during the sub-events of OAE1b. The climate-driven extensive wildfire activity in the mid-latitude terrestrial ecosystems can be a contributing factor for OAE1b through the increased flux of nutrients fuelling primary producers in the lake and marine environments and leading to more speculative anoxia to allow the deposition of organic-rich sediments. Our results provide essential understanding of the importance of wildfires in driving mechanism of oceanic anoxic events (OAEs) in Earth's history.

Seasonal distribution pattern and bioaccumulation of Polycyclic aromatic hydrocarbons (PAHs) in four bioindicator coastal fishes of Argentina

Polycyclic aromatic hydrocarbons (PAHs) are pollutants of global concern in coastal environments. They have a wide range of biological toxicity and due to their inherent properties, can easily bioaccumulate in organisms and concentrate in the environment. This work evaluated, in an integrated way, the seasonal PAH distribution patterns in sediments and four bioindicators fish species in a highly impacted estuary of Argentina; besides, their bioaccumulation patterns were assessed for the first time as indicator of ecological risk. The highest PAH levels in fish were found for Ramnogaster arcuata with an average of 64 ng g−1 w.w., followed by Micropogonias furnieri (45 ng g−1 w.w.), Cynoscion guatucupa (28 ng g−1 w.w.), and Mustelus schmitti (16 ng g−1 w.w.). Fish presented the highest PAH levels in fall with a predominance of petrogenic PAHs in colder seasons and pyrolytic PAHs in warmer seasons. Sediments presented an average of 233 ng g−1 d.w. with the same seasonal composition pattern of the fish tissues. Additionally, the data suggested that the main source of PAHs are wastewater discharges. The bioaccumulation factor (BAF) of PAHs in the tested fishes were found to range from 0.3 to 8. The highest values were observed during fall and winter, while bioaccumulation did not occur in moist spring and summer samples, which would suggest a high biotransformation process during these seasons. Results suggested that class III of juvenile C. guatucupa and M. furnieri, and adults R. arcuata are more sensitive bioindicators of chronic PAH contamination and that their bioaccumulation is independent of the compound hydrophobicity; this could have a positively influence on the criteria used for biological monitoring programs along the Atlantic coast. In addition, the presented BAF data on the target species will serve as a useful pollution indicator for South Atlantic coastal fish.

Precession-scale climate forcing of peatland wildfires during the early middle Jurassic greenhouse period

Abstract As an important terrestrial carbon reservoir, peatland has the potential to influence the global carbon cycle and global climate. In recent decades, the frequency and extent of peatland wildfires in boreal and tropical regions are increasing owing to climate change and human activity. However, the processes that govern changes in peatland wildfire are poorly understood over long timescales, particularly on the orbital scales. We analyzed coal petrology and geochemistry in coal seams of the Aalenian Yan'an Formation in Ordos Basin to identify peatland wildfire records based on the co-occurrence of charcoal and pyrolytic polycyclic aromatic hydrocarbons (PAHs). In addition, the presence of widespread peatland wildfires has suggested that atmospheric oxygen concentration at the time should be substantially higher than the minimum needed for sustained combustion. Spectral analysis of vitrinite/inertinite (V/I) and inertinite reflectance data demonstrate that peatland wildfires were controlled by precession cycles owing to a shift in the seasonal contrast and amount of rainfall. Our results provide essential context for understanding the importance of peatland wildfires carbon emissions in a coupling of orbital forcing, climate, and the carbon cycle.

Preliminary assessment of Miramar Petrochemical Harbor as PAH source to Guajará bay (Belém-PA-Brazil) surface sediments

Abstract A preliminary study on a petrochemical harbor as a potential source of polycyclic aromatic hydrocarbons (PAH) to surface sediments of Guajara bay, located in Belem City, Para State, Brazil, over the last 10 years is presented here. The 16 priority USEPA PAH were identified and quantified. Surface sediment samples, collected at 5 sites in the bay, near Miramar Petrochemical Harbor (TEMIR), were extracted and analyzed by high performance liquid chromatography with a diode array detector. Total PAH concentration ranged from 533.0 to 3123.3 ng g-1 dry weight with a mean concentration of 1091.9 ng g-1. The most contaminated places were those where muddy sediments were found with highest concentrations of organic matter. The priority PAH with low molecular weight represented 54.4% of the total abundance and indicate that the main source of contamination of the sediments was petrogenic, indicative of the relevant contribution of the petrochemical harbor activity to the input of PAH to Guajara bay. However, pyrolytic PAH coming from fuel combustion, household waste combustion and untreated sewage discharge are also potential contamination sources to this environment.

Characterization and source apportionment of polycyclic aromatic hydrocarbons (pahs) in the sediments of gulf of Pozzuoli (Campania, Italy)

Most of the literature reports on the impact of the former Bagnoli brownfield on the pollution of Bagnoli Bay, embedded in the Gulf of Pozzuoli (GoP). Thus, we studied concentrations, types and sources of sixteen PAHs (EPA) in sediments at 22 sites along 5 transects covering the entire area of GoP. Outstanding levels of PAHs were found, varying from 7.1μgg−1 to 2.5 E+3μgg−1. Sediments collected at sites far away from Bagnoli were found to be polluted to a similar extent than those facing the brownfield site, with values>100μgg−1. Total PAHs levels in the sediments of GoP were higher by thirty-eleven thousand fold than those reported by other studies from various marine sites in the world. Transit axes of fine and very fine sands and diagnostic indexes revealed a common pyrolytic PAHs pollution spreading from the Bagnoli plant to all GoP.

Effects of pyrolytic and petrogenic polycyclic aromatic hydrocarbons on swimming and metabolic performance of zebrafish contaminated by ingestion

Depending on their origins, polycyclic aromatic hydrocarbons (PAH) are characterized by different chemical properties. Petrogenic PAH (e.g. from fossil fuels) and pyrolytic PAH (e.g. those produced by incineration processes) are therefore expected to affect organisms differently. The impact of trophic exposure to these PAH was investigated on swimming and metabolic performance of zebrafish Danio rerio. Two-month-old juveniles and six-month-old adults were individually challenged following a swimming step protocol. While pyrolytic exposure did not affect fish whatever the duration of exposure, it appeared that petrogenic PAH impaired adults' performance. Indeed, the active metabolic rate in petrogenic PAH-contaminated adults was significantly reduced by 35%, and critical swimming speed by 26.5%. This was associated with cardiac abnormalities, which are expected to contribute to the reduction of oxygen transport, particularly during intensive effort. These results may be due to the different composition and toxicity of PAH mixtures.

Distribution, Seasonal Variations, and Ecological Risk Assessment of Polycyclic Aromatic Hydrocarbons in the East Lake, China

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants and their presence in urban lakes is of great concern for human and ecological health. One hundred twenty‐six surface water samples and 126 surface sediment samples were collected in winter 2012 and summer 2013, respectively, to investigate distribution patterns, seasonal variations, possible pollution sources, and potential ecological risks of 16 priority PAHs in the largest urban lake, East Lake in China. The total concentrations of 16 PAHs in water and sediment ranged from 10.2 to 525.1 ng L−1 and 10.9 to 2478.1 ng g−1 dry weight, respectively. The concentrations of ∑PAHs in sediment samples in summer were almost two times greater than those in winter, but the seasonal variations did not differ significantly in the water samples. Diagnostic ratios of indicator PAHs reflected a possibility of pyrolytic PAH input in sediment and a mixture of petroleum and combustion sources in water from the East Lake. The potential ecological risk assessment based on the risk quotient indicated relatively moderate ecological risks of PAHs in the East Lake.

Occurrence and distribution of polycyclic aromatic hydrocarbons in mussels from the gulf of Naples, Tyrrhenian Sea, Italy

To assess the potential impact of the industrial activity on food safety and risk for consumers, the aim of the study was to evaluate the levels of 14 polycyclic aromatic hydrocarbons (PAH) in 69 samples of wild and farm Mytilus galloprovincialis, collected in sites of coast of Gulf of Naples, Tyrrhenian Sea.All hydrocarbons were found in samples. Higher levels of pyrolytic PAHs were in wild than in farm mussels. Benzo(a)pyrene exceeded the Regulation (EC) n.835/11 levels of 1μg/kg in 15 samples (71.42%) of wild and 25 samples (65.79%) of farm mussels. System of sum of 4 hydrocarbons exceeded the law level in 15 samples (71.42%) of wild and 21 samples (55.26%) of farm mussels. Wild mussel levels showed a potential impact of pyrolytic sources of PAH on food safety. Occurrence of carcinogenic PAHs should be a cause for concern, in areas where the mussels are being farmed for human consumption.

Trophic contamination by pyrolytic polycyclic aromatic hydrocarbons does not affect aerobic metabolic scope in zebrafish Danio rerio.

The effect of trophic exposure to pyrolitic polycyclic aromatic hydrocarbons (PAH) on aerobic metabolism of zebrafish Danio rerio was investigated. There were no significant differences in standard metabolic rate (SMR), active metabolic rate (AMR) or aerobic metabolic scope (AS) at any sublethal concentration of PAH in the diet of adult or juvenile fish. This suggests that under these experimental conditions, exposure to PAH in food did not influence aerobic metabolism of this species.

Pyrolytically Derived Polycyclic Aromatic Hydrocarbons in Marine Oils from the Tarim Basin, NW China

Polycyclic aromatic hydrocarbons (PAHs) in oils from the cratonic region of the Tarim Basin have been characterized by gas chromatography–mass spectroscopy to investigate their origins and geochemical applications. PAHs dominated by unsubstituted components together with pyrolytically derived components such as anthracene, fluoranthene, benzoanthracene, benzofluoranthenes and benzopyrenes occur in some oils represented by those from well TD2. The widespread spatial and temporal occurrence of igneous activity within the Palaeozoic succession in the Tarim Basin makes the derivation of the latter PAHs from pyrolytic sources probable. Exposure to high temperatures results in the pyrolysis of the oil reservoir, adding high-temperature aromatic artifacts to the oil. Geochemical measurements show the wide occurrence of mixing processes between pyrolytically derived PAHs and diagenetically derived hydrocarbons. Good preservation of pyrolytic PAHs in oils from well TD2 and a few other wells is because they are less affected by late charge and dilution processes. However, these pyrolytically derived PAHs in conjunction with the bulk carbon isotopic compositions have been commonly misinterpreted in oil-source correlations. Only oils from well TD2 and a few other wells have been correlated to the Cambrian source rocks because of the wrong selection of end members. When the effects from the rapid heating of organic material by magmatic intrusions and/or hydrothermal fluid activity are properly accounted for, confusion in oil-source correlations may potentially be resolved and the contribution from the Cambrian strata can appropriately be assessed.

Aerobic metabolism and cardiac activity in the descendants of zebrafish exposed to pyrolytic polycyclic aromatic hydrocarbons.

The increase of anthropogenic activities on coastal areas induces discharges of polycyclic aromatic hydrocarbons (PAHs) in aquatic ecosystem. PAH effects depend not only on their concentration and the way of contamination but also on the different developmental stages of the organism. Zebrafish were exposed to relevant concentration of pyrolytic PAHs from the first meal (i.e., 5-day post fertilization, dpf) to mature adults. Parental effect of this type of exposure was evaluated through the assessment of aerobic metabolic scope, cardiac frequency, and cardiac mRNA expression on larval and/or embryo progeny of contaminated fish. Our results suggest that cardiac frequency increased in larval descendants of fish exposed to the environmental concentration of pyrolytic PAHs (i.e., 5 ng.g(-1) of food), while a lack of effect on aerobic metabolism in 5 dpf larvae was highlighted. A surexpression of mRNA related to the cardiac calcium transporting ATPase atp2a2a, a protein essential for contraction, is in accordance with this increasing cardiac frequency. Even if cardiac development genes cmlc1 and tnnt2a were not affected at early life stages tested, complementary work on cardiac structure could be interesting to better understand PAHs action.

Levels and distributions of polycyclic aromatic hydrocarbons (PAHs) in middle reach of Huaihe River, China: anthropogenic influences and ecological risks

Polycyclic aromatic hydrocarbons (PAHs) are a group of aromatic hydrocarbons with high toxicity to human health. PAH emissions from industrial activities have become the primary sources of PAH contamination in Chinese watersheds. Here, we analyzed 10 individual priority PAHs in 120 water samples taken from middle reach of Huaihe River, China. The results show that the PAH levels in studied watershed are significantly lower as compared to other Chinese watersheds, approaching or slightly exceeding the PAH levels in watersheds from selected European and North American countries. We observe rather large variation in spatial and vertical PAH distributions, pointing to PAH inputs from local industrial emissions, and PAH cycle among atmosphere, water and sediment. Individual PAH ratios (i.e., phenanthrene/anthracene and fluorene/pyrene) and principal components analysis suggest a primarily pyrolytic PAH sources (combustion of coal and coke) in water column. Other accompanying PAH sources include emissions from steel industry and gasoline. Total toxic benzo[a]pyrene equivalent of PAHs in studied water column indicates that PAHs in watershed of middle reach of Huaihe River pose limited toxicity to the environment.

Trace organic pollutants in sediments from Huaihe River, China: Evaluation of sources and ecological risk

Summary In the present study, a combination of multiple molecular markers was used to improve the identification of pollution sources in sediment samples collected from Huaihe River, China. No significant spatial variation of aliphatic hydrocarbons (normal alkanes, n-alkanes) was observed, whereas, relatively high concentrations of 28 polycyclic aromatic hydrocarbons (Σ28PAH) and 20 linear alkylbenzenes (Σ20LAB) in urban sediments and low concentrations of Σ28PAH and Σ20LAB in farm areas were determined. Overall, sediment samples collected from urban areas contained high concentration of Σ20LAB with low concentration of Σ28PAH which mostly originated from pyrolysis, while rural sediments had opposite trends, reflecting the significant input of domestic sewage in urban areas. Residual n-alkanes were mostly from natural sources with relatively low proportion of petrogenic input. For PAHs, the concentrations of diagentic perylene and pyrolytic PAHs from farm areas to urban areas tend to decrease and increase, respectively. Likely origins of pyrolytic PAHs were considered combustion of coal and petroleum related. In the village areas, pyrolytic PAHs were mostly contributed from coal and diesel combustion. Poor domestic wastewater treatment in rural areas caused low ratio of I/E. On the other hand, the results of total toxic benzo[a]pyrene (BaP) equivalent reveal the ecological risk by PAHs was negligible in Huaihe River.

Remembering Roger F. C. Brown: A Personal Note on the Development of Pyrolysis as a Synthetic and Mechanistic Technique in Organic Chemistry

Remembering Roger F. C. Brown: A Personal Note on the Development of Pyrolysis as a Synthetic and Mechanistic Technique in Organic Chemistry

DISTRIBUTION OF POLYCYCLIC AROMATIC HYDROCARBONS IN SURFACE SEDIMENTS OF KOH SICHANG ANCHORAGE AREA, THAILAND

The levels and distribution of polycyclic aromatic hydrocarbons (PAHs) were investigated in surface sediments of Koh Sichang anchorage area, Thailand using gas chromatography with flame-ionization detection (GC/FID). The total concentrations of 16 PAHs US EPA priority pollutants varied from 65.2 to 18,970 ng/g dw, with a median concentration of 282±3,660 ng/g dw. The sediment samples were classified as moderately contaminated compared to those observed in other regions. PAH compositional signatures of surface sediments of the study area were dominated by higher molecular weight PAHs (4-6 rings) comprising about 87 per cent of total PAHs concentrations. Dibenzo[a,h]anthracene, benzo[b]fluoranthene, benzo[g,h,i]perylene, benzo[a]pyrene, fluoranthene, indeno[1,2,3-cd]pyrene, and pyrene represented the highest fractions in most surface sediment samples. Source apportionment using diagnostic PAH ratios indicated that composition of PAHs in most sediment samples originated mainly from incomplete combustion of organic matter (pyrolytic origin), with a mixture of pyrolytic and petrogenic PAHs were observed in some of the study sites. The presence of almost all human carcinogenic PAHs in the study area indicated that these sediments can be considered contaminated sites, suggesting that future monitoring programs together with an effective coastal management program must be implemented to ensure health and safety for all.

Human impact on a small barrier reef meadow of Posidonia oceanica (L.) Delile on the north Tyrrhenian coast (Italy)

The health status of an emerging Posidonia oceanica meadow, subject to high human impact, was studied. Biometric variables, heavy metals, PAHs and C, N, P contents were determined in sediment and seagrass samples. The meadow was found to grow under oligotrophic conditions and an increase in nutrient content was only recorded in autumn. In sediment, Hg exceeded its ERL (effects range low) and sometimes also its ERM (effects range medium), and Cu was close to its ERL. In leaves, Hg and Cu were relatively high but below their respective ERLs. Sediments close to the meadow were heavily contaminated with pyrolytic PAHs, some of which exceeded their ERLs. P. oceanica did not show major accumulation of PAHs, lighter molecules predominating. Despite 40years of intense human activity, meadow growth dynamics and contaminant accumulation did not suggest that the meadow was regressing.