Pyrogenic Polycyclic Aromatic Hydrocarbons Research Articles

Geochemical implications of uranium-bearing thucholite aggregates in the Upper Permian Kupferschiefer shale, Lubin district, Poland

AbstractNew inorganic and organic geochemical data from thucholite in the Upper Permian (Wuchiapingian) Kupferschiefer (T1) shale collected at the Polkowice-Sieroszowice Cu-Ag mine in Poland are presented. Thucholite, which forms spherical or granular clusters, appears scattered in the T1 dolomitic shale at the oxic-anoxic boundary occurring within the same shale member. The composition of thucholite concretions and the T1 shale differs by a higher content of U- and REE-enriched mineral phases within the thucholite concretions compared to the T1 shale, suggesting a different mineralising history. The differences also comprise higher Ntot, Ctot, Htot, Stot contents and higher C/N, C/S ratios in thucholite than in the T1 shale. The hydrocarbon composition of the thucholite and the surrounding T1 shale also varies. Both are dominated by polycyclic aromatic compounds and their phenyl derivatives. However, higher abundances of unsubstituted polycyclic aromatic hydrocarbons in the thucholite are indicative of its pyrogenic origin. Pyrolytic compounds such as benz[a]anthracene or benzo[a]pyrene are more typical of the thucholite than the T1 shale. Microscopic observations of the thucholite and its molecular composition suggest that it represents well-rounded small charcoal fragments. These charcoals were formed during low-temperature combustion, as confirmed by semifusinite reflectance values, indicating surface fire temperatures of about 400 °C, and the absence of the high-temperature pyrogenic polycyclic aromatic hydrocarbons. Charred detrital particles, likely the main source of insoluble organic matter in the thucholite, migrated to the sedimentary basin in the form of spherical carbonaceous particulates, which adsorbed uranium and REE in particular, which would further explain their different contents and sorption properties in the depositional environment. Finally, the difference in mineral content between thucholite and the T1 shale could also have been caused by microbes, which might have formed biofilms on mineral particles, and caused a change in the original mineral composition.

A Holocene history of climate, fire, landscape evolution, and human activity in northeastern Iceland

Abstract. Paleoclimate reconstructions across Iceland provide a template for past changes in climate across the northern North Atlantic, a crucial region due to its position relative to the global northward heat transport system and its vulnerability to climate change. The roles of orbitally driven summer cooling, volcanism, and human impact as triggers of local environmental changes in the Holocene of Iceland remain debated. While there are indications that human impact may have reduced environmental resilience during late Holocene summer cooling, it is still difficult to resolve to what extent human and natural factors affected Iceland's late Holocene landscape instability. Here, we present a continuous Holocene fire record of northeastern Iceland from proxies archived in Stóra Viðarvatn sediment. We use pyrogenic polycyclic aromatic hydrocarbons (pyroPAHs) to trace shifts in fire regimes, paired with continuous biomarker and bulk geochemical records of soil erosion, lake productivity, and human presence. The molecular composition of pyroPAHs and a wind pattern reconstruction indicate a naturally driven fire signal that is mostly regional. Generally low fire frequency during most of the Holocene significantly increased at 3 ka and again after 1.5 ka BP before known human settlement in Iceland. We propose that shifts in vegetation type caused by cooling summers over the past 3 kyr, in addition to changes in atmospheric circulation, such as shifts in North Atlantic Oscillation (NAO) regime, led to increased aridity and biomass flammability. Our results show no evidence of faecal biomarkers associated with human activity during or after human colonisation in the 9th century CE. Instead, faecal biomarkers follow the pattern described by erosional proxies, pointing toward a negligible human presence and/or a diluted signal in the lake's catchment. However, low post-colonisation levels of pyroPAHs, in contrast to an increasing flux of erosional bulk proxies, suggest that farming and animal husbandry may have suppressed fire frequency by reducing the spread and flammability of fire-prone vegetation (e.g. heathlands). Overall, our results describe a fire frequency heavily influenced by long-term changes in climate through the Holocene. They also suggest that human colonisation had contrasting effects on the local environment by lowering its resilience to soil erosion while increasing its resilience to fire.

Fire activities and their impacts on local ecosystems in the southern Ordos Basin during the Middle Jurassic: Evidence from pyrogenic PAHs and petrography of inertinite-rich coal

The high frequency of fires during the formation of some mire systems in the Jurassic is thought to have influenced how terrestrial ecosystems evolved. Ancient mires, now present as coal seams, contain high-resolution paleoenvironmental and paleoclimatic records. Thus, the analysis of coal beds provides valuable, insightful, and practical knowledge on the changes in paleoclimate and, in this case, fire prevalence. Using petrographic, carbon isotopic, mercury content, and polycyclic aromatic hydrocarbon (PAH) determinations, the Middle Jurassic No. 4 coal from the Binchang region in the Ordos Basin was examined in order to understand the nature of fire during the formation of the mires. The results show that the No. 4 coal exhibits a high content of inertinite (average content 70%). Notably, the correlation coefficient (r = 0.79) between the concentration of PAHs (with >3 rings) and the proportion of inertinite indicates that the high content of inertinite was predominantly the result of fire. The presence of natural char and coke in the coals further indicates the frequent incidence of fires during the Middle Jurassic in the southern Ordos Basin. High frequency of fires can be attributed to the availability of fuel (i.e., the buildup of organic material), high atmospheric oxygen levels, and intermittent dry climatic conditions. The random reflectance of inertinite (specifically, fusinite and semifusinite) in the No. 4 coal bed ranges from 1.25% to 2.45%, which, with the presence of pyrogenic PAHs, suggests that their formation may have been predominantly affected by low- and moderate-temperature fires. The high frequency of fires is thought to have significant impacts on terrestrial and hydrological ecosystems. These effects may have included the circulation of atmospheric mercury, as well as the possible occurrence of anoxic events in the lakes.

PAHs in high Arctic copepods Calanus hyperboreus following exposure of residues from in situ burning of oil spill

In situ burning of marine oil spills reduces the total amount of oil in the environment, but a negative side effect may be the generation of environmentally hazardous polycyclic aromatic hydrocarbons (PAHs) that may pose a risk for bioaccumulation, particularly in organisms having a high lipid content. In this study uptake of PAHs from oil and burn residue were examined in the high arctic copepod Calanus hyperboreus. A major part of the low ring number petrogenic PAHs in the oil was removed during burning and relative higher concentrations of pyrogenic high ring number PAHs was found in the burn residue. This suggests that burning markedly reduces the general PAH exposure load. Furthermore, the pyrogenic PAHs generated during the burn were not bioconcentrated to quantifiable levels in the copepods. We conclude that in situ burning can mitigate the potential risk of PAH uptake for copepods and other pelagic organisms in the marine environment as the pyrogenic PAHs only pose low risk for uptake from the water by the copepods and other pelagic organisms.

Unravelling mixed sources of polycyclic aromatic hydrocarbons (PAH) in urban soils by visual characterization of anthropogenic substrates and coal particles, 71 PAH and alkylated PAH patterns

The identification of polycyclic aromatic hydrocarbon (PAH) sources in heterogeneous urban soils containing pyrogenic and/or petrogenic anthropogenic substrates is a common task for risk assessment. Here, for the first time, the results of source identification using analysis of 71 PAH, alkylated PAH patterns and PAH Alkylation Index were related to visually identified and quantified anthropogenic substrates in 50 soil samples. Only the combination of chemical methods with visual characterization enabled the deeper understanding of varying alkylated PAH patterns used for source apportionment and their superimposition if multiple sources occur. Pyrogenic substrates show homogenic slope-shape PAH patterns despite large visual variety. Petrogenic substrates (bituminous coals), show prevailingly bell-shape patterns but pyrogenic patterns also occur, probably due to residues from industrial processes and/or sorption of other pyrogenic PAH. Superimposition of both PAH patterns within a sample results in intermediate patterns, which are determined by the abundance of substrates and their individual PAH contents. A discrepancy between the share of petrogenic substrates and petrogenic PAH was observed due to low-medium PAH contents from coals/tailings. This may lead to misinterpretations if only chemical source identification methods are applied. With increasing proportion of petrogenic PAH in the mixture, the intermediate V-shape pattern (later bell-shape) appears in lower molecular weight PAH and moves progressively to higher molecular weight PAH. ∑71 PAH contents vary from 1.77 to 326.5 mg/kg (median 26.5 mg/kg). Non-EPA PAH measured include highly toxic ∑4 dibenzopyrene isomers (0.045–6.23 mg/kg, median 0.79 mg/kg) and 7H-benzo[c]fluorene (0.008–1.57 mg/kg, median 0.12 mg/kg). Most common anthropogenic substrates are bottom ashes, slags, bituminous coals/tailings and coke/coke ash. The PAH Alkylation Index identifies reliably samples dominated by either petrogenic (<0.4) or pyrogenic (>0.9) PAH, independently of the PAH content. Mixed or primarily pyrogenic PAH sources (0.4–0.9) need further investigations, like the presented combination of methods, which enables a reliable source apportionment.

Evidence of transboundary movement of chemicals from Mexico to the U.S. in Tijuana River Estuary sediments

The Tijuana River Estuary (TRE) has been a public health hazard and point of contention between the United States and Mexico for decades, with sources of pollution on both sides of the border. The goal of our study is to determine the presence and dynamics of chemical contamination in the TRE. We sampled sediment from four TRE locations in the U.S. during stable dry conditions and immediately after a wet weather period. Organic chemicals were initially screened with non-targeted analysis using gas chromatography high-resolution mass spectrometry (GC/HRMS) that tentatively identified 6978 chemicals in the NIST 20 database. These tentative identifications were filtered using the USEPA CompTox database to guide quantitative targeted analysis at detection limits below 1 ng/g dry weight sediment. Quantitative targeted analysis of 152 organic pollutants and 18 inorganic elements via GC/HRMS revealed generally higher concentrations of contaminants in dry weather sediments compared to wet weather sediments. The highest concentrations of all chemical classes were detected at the site closest to the U.S.-Mexico border, followed by an urban area near Imperial Beach, California, U.S. All sites exhibited a mixture of petrogenic and pyrogenic polycyclic aromatic hydrocarbons (PAHs). Current-use pesticides were dominated by pyrethroid insecticides and the thiocarbamate herbicide s-Ethyl dipropylthiocarbamate (EPTC), while the U.S.-banned organochlorine pesticides were dominated by chlordanes, dieldrin, and dichlorodiphenyltrichloroethane (DDT) and its degradation byproducts. Polychlorinated biphenyl (PCB) concentrations were greatest at the site closest to the U.S.-Mexico border but in the low nanogram-per-gram range. Phthalates were only found at the same site, with relatively high concentrations of bis(2-ethylhexyl) phthalate. This study provides positive identification and quantitative concentrations for organic pollutants in TRE sediments. Our data suggest that there are multiple sources of chemical contamination in the estuary, including possible transboundary movement of pollutants from Mexico.

A synthesis of the Cretaceous wildfire record related to atmospheric oxygen levels?

The Cretaceous was a significant greenhouse period in Earth's history with higher atmospheric CO2 levels and temperatures than today. Although evidence of combustion has been widely described from the Cretaceous deposits, our understanding of the spatiotemporal diversification pattern and process of the Cretaceous wildfires is still limited. In this study, we comprehensively synthesize a total of 271 published Cretaceous wildfire occurrences based on the by-products of burning, including fossil charcoal, pyrogenic inertinite (fossil charcoal in coal), and pyrogenic polycyclic aromatic hydrocarbons (PAHs). Spatially, the dataset shows a distinctive distribution of reported wildfire evidence characterized by high concentration in the middle latitudinal areas of the Northern Hemisphere (30°N–60°N) over the Cretaceous. Temporally, an overall increasing trend of the reported wildfire data from the Early Cretaceous to the Late Cretaceous is coincident with higher atmospheric O2 levels. However, the spatial and temporal patterns may result from many types of factors, such as taphonomy, preservation, and researcher biases, instead of a real picture of the Cretaceous wildfire evolution. To better understand the spatiotemporal diversification of the Cretaceous wildfire, more investigations on the record of wildfire occurrences during this period would be necessary in the future.

Sedimentary records of contaminant inputs in Frobisher Bay, Nunavut

Contaminants, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), heavy metals, and per and polyfluoroalkyl substances (PFASs), primarily reach the Arctic through long-range atmospheric and oceanic transport. However, local sources within the Arctic also contribute to the levels observed in the environment, including legacy sources and new sources that arise from activities associated with increasing commercial and industrial development. The City of Iqaluit in Frobisher Bay, Nunavut (Canada), has seen rapid population growth and associated development during recent decades yet remains a site of interest for ocean protection, where Inuit continue to harvest country food. In the present study, seven dated marine sediment cores collected in Koojesse Inlet near Iqaluit, and from sites in inner and outer Frobisher Bay, respectively, were analyzed for total mercury (THg), major and trace elements, PAHs, PCBs, and PFASs. The sedimentary record in Koojesse Inlet shows a period of Aroclor 1260-like PCB input concurrent with military site presence in the 1950–60s, followed by decades of input of pyrogenic PAHs, averaging about ten times background levels. Near-surface sediments in Koojesse Inlet also show evidence of transient local-source inputs of THg and PFASs, and recycling or continued slow release of PCBs from legacy land-based sources. Differences in PFAS congener composition clearly distinguish the local sources from long-range transport. Outside Koojesse Inlet but still in inner Frobisher Bay, 9.2 km from Iqaluit, sediments showed evidence of both local source (PCB) and long-range transport. In outer Frobisher Bay, an up-core increase in THg and PFASs in sediments may be explained by ongoing inputs of these contaminants from long-range transport. The context for ocean protection and country food harvesting in this region of the Arctic clearly involves both local sources and long-range transport, with past human activities leaving a long legacy insofar as levels of persistent organic pollutants are concerned.

Paleoclimate-induced wildfires in a paleomire in the Ordos Basin, Northern China during the Middle Jurassic greenhouse period

Paleo-wildfires are of great significance in the study of paleomire ecosystems. The products of such fires preserved in paleomires can provide detailed information for the reconstruction of wildfire regimes. This study analyzed the distribution of charcoal and aromatic biomarkers in a coal seam from the Middle Jurassic Yan'an Formation in the Ordos Basin, China. The results showed very high content of pyrogenic inertinite (38%–62%) and common occurrence of pyrogenic polycyclic aromatic hydrocarbons (PAHs) in the studied coal seam, suggesting that wildfires occurred frequently during the period of peat accumulation. The mean reflectance of pyrogenic inertinite (1.50%) in all samples indicates a dominance of low-temperature wildfires in the paleomire, which is also supported by the high abundance of 2- to 3-ring PAHs. Furthermore, the common observations of high-reflectance pyrogenic inertinite (∼ 4.47%RIo) and 4- to 6-ring PAHs suggest the repeated occurrence of high-temperature wildfires. Various parameters of 3- to 4-ring PAHs indicate a relatively high proportion of charred material contributing to the organic matter in the paleomire. The dimethylphenanthrene ratios of the studied samples were inconsistent with those of modern experimental results, which can be probably attributed to the non-analogous vegetation composition in the Jurassic paleomire, and caution should thus be exercised when applying dimethylphenanthrene ratios to ancient sediments. The ratio of retene to 3-ring PAHs implies the contribution of conifers to the fires in the paleomire. The pyrogenic PAHs originated from both, combustion residues and smokes produced by in situ and local wildfires. The high O2 level during the Middle Jurassic promoted the frequent occurrence of wildfires in the studied paleomire. In addition, the occurrence of wildfires was collectively affected by the wet/humid climates, seasonality, and depositional environment.

Fire activity across Cretaceous/Paleogene transition: Evidence from pyrogenic biomarkers preserved in the Mahadeo-Cherrapunji section, Meghalaya, India.

Previous studies on high concentrations of polycyclic aromatic hydrocarbon (PAHs) present in the shallow-marine Um-Sohryngkew River (USR) Cretaceous/Paleogene Boundary (KPB) section suggested regional fire incidences and biotic stress on life. However, such observations at the USR site have not been confirmed so far anywhere else in the region, we, therefore, do not know whether the signal was local or regional. Thus, to find out charred organic markers associated with the shelf facies KPB outcrop (at a distance of over 5 km) of the Mahadeo-Cherrapunji road (MCR) section, PAHs were analyzed using gas chromatography-mass spectroscopy. Data show a notable rise in the PAHs and exhibit maximum abundance in the shaly KPB transition layer (in biozone P0) and the immediately underlying layer. The PAH excursions match well with the major incidences of the Deccan volcanic episodes and convergence of the Indian plate with the Eurasian and Burmese plates. These events were responsible for seawater disturbances and eustatic and depositional changes, including the retreat of the Tethys. The incidence of high amount of pyogenic PAHs unrelated to the total organic carbon content is suggestive of wind-blown or aquatic system transportation. A down-thrown shallow-marine facies of the Therriaghat block was responsible for an early accumulation of PAHs. However, the spike of perylene in the immediately underlying KPB transition layer is plausibly linked to the Chicxulub impact crater core. Anomalous concentrations of combustion-derived PAHs together with the high fragmentation and dissolution of the planktonic foraminifer shells show marine biodiversity and biotic distress. Significantly, the pyrogenic PAH excursions are restricted to either the KPB layer itself or strictly below or above it, indicating regional fire incidences and attendant KPB transition (66.016 ± 0.050 Ma).

Insights about levels and sources of organic pollution in an urbanized Amazon estuary (Belém, PA, Northern Brazil)

Amazon aquatic systems have been affected by organic pollution from urbanized regions. This study was conducted to determine the levels, sources, and distribution patterns of 16 polycyclic aromatic hydrocarbons (PAHs) and 6 steroid markers in surficial sediments from an important urbanized Amazon estuarine system (Belém, PA, Northern Brazil). Total PAH concentration (∑PAH) ranged from 878.2 to 9905.7ngg-1, 3295.2ngg-1 on average, suggesting a highly contaminated environment. PAH molecular ratios and statistical analysis indicated that PAH originated from a mixture of local sources emissions, mainly related to the combustion of fossil fuels and biomass. Coprostanol levels (maximum concentration = 292.52ngg-1) could be compared to the mid-range reported in the literature. Studied stations, except for one, presented sterol ratio data indicating organic matter related to untreated sewage. Sterols indicative of sewage contamination showed a correlation with pyrogenic PAH amounts which are transported by the same channels where sewage is discharged.

Wildfire activity driven by the 405-kyr orbital climate cycles in the Middle Jurassic

Global changes in the frequency and extent of wildfires are thought related to human-induced climate warming influencing fire weather and ignition probability. However, our understanding is still limited on whether and how pre-anthropogenic natural periodic changes in climate control variations in wildfire behavior over orbital timescales. Here we present a ∼ 2.2-Myr-long record of wildfire activity based on evidence of charcoal and pyrogenic polycyclic aromatic hydrocarbons (PAHs) abundances from the mid-latitude terrestrial sediments of the Middle Jurassic, along with multiproxy climate data including organic carbon isotopes, chemical weathering indices, and clay minerals from the same sediments. Our results show that peaks of wildfire frequency well correspond to seasonal dry climate with cyclicity of ∼405 kyr, suggesting long eccentricity-induced climate cycles forcing of wildfire activity by impact on the fuel load and state. The periods of enhanced wildfire activity were consistent with the phases of orbital-driven increased seasonality in Earth's past, implying that current human-induced climatic change has already led to an increasing in the risk of wildfires despite decreasing Earth's eccentricity.

Anthropogenic and natural hydrocarbons in water and sediments of the Kara Sea.

The results on the content and composition of aliphatic (AHСs) and polycyclic aromatic hydrocarbons (PAHs) at the geochemical barrier between the Kara Sea and the Ob and Yenisei Rivers are discussed in comparison with those in the mouth areas of the Lena, Khatanga, Indigirka and Kolyma. It has been established that hydrocarbon concentrations sharply decrease in the river-sea mixing zones, and their composition, and the ratio of their dissolved and suspended forms change. Besides, the research season plays a great role, as the highest content of hydrocarbons and particulate matter was found in the Ob Gulf during the flood, when the concentrations of AHCs in surface waters reached 325μg/L, PAHs -15ng/L, particulate matter-15.5mg/L. In the Kara Sea itself, AHC concentrations increased on average from 20 to 59μg/L, that is most likely associated with the melting of seasonal ice and floods. Anthropogenic influence was found in river waters, where the proportion of naphthalenes, which marks oil products, and pyrene, which marks pyrogenic PAHs, is increased. In the Ob Gulf is linked to an increase in navigation along the Northern Sea Route and the functioning of the port of Sabetta. In the mouth area of the Yenisei, the concentrations of both AHC and PAH in surface waters and sediments varied in a smaller range than in the mouth area of the Ob, which is due to the nature of the rocks that make up the catchment areas of these rivers, as well as the regulation of the Yenisei runoff. The hydrological features of the estuarine areas can lead to increased AHC concentrations (the mouth of the Khatanga, up to 189μg/L, 2.6μg/mg SPM). The minimum AHC content in SPM and sediments in the river transects was established in the East Siberian rivers (Indigirka, Kolyma), associated with the decreasing productivity in waters from the Western Arctic seas to the Eastern.

Decadal Variation of Polycyclic Aromatic Hydrocarbons (PAHs) in an Area Contaminated by Coal Gangue Dump: Emphasis on Concentration, Profile, Source and Carcinogenic Risk

Polycyclic aromatic hydrocarbons (PAHs) are recognized as carcinogens that pose a severe threat to human health. Research on the temporal variation of PAHs was confined to monthly and seasonal investigations, and a longer timescale study remained inadequate until recently. Therefore, this study focuses on the decadal variation of PAHs in environmental media contaminated by a coal gangue dump in the Jiulong Coal Mine, Fengfeng, China. The results show that the total concentrations of PAHs have sharply declined compared to the past. The result of the paired-sample t-test indicates that several individual PAHs have obviously changed in concentration with statistical significance (p &lt; 0.05). Moreover, proportions of medium-molecule weight PAHs increase with statistical significance (p &lt; 0.01) when compared to the past. Various diagnostic ratios suggest that PAHs in previous samples are mainly derived from weathering products of coal gangue and vehicle exhaust, while PAHs in the present samples are dominated by those originating from pyrogenic sources. Calculation of incremental lifetime cancer risks (ILCRs) indicates high carcinogenic risk despite a considerable decrease in ILCR values by 2 to 3 orders of magnitude. It shows that recent measurements conducted by the local government do weaken the contamination of coal gangue dumps, but more attention to pyrogenic PAHs is necessary.

Origin and sources of polycyclic aromatic hydrocarbons (PAHs) in sediments core from Tigris, Euphrates and Shatt Al-Arab rivers

Due to the important area of the Tigris, Euphrates and Shatt Al-Arab rivers in Iraq, and the effect of pollutant to theses rivers, the object of study is the origin and sources of PAHs compounds in sediment core samples which collected in 2021 from six important stations that are (Tigris1, Tigris2, Euphrates1, Euphrates2, Shatt Al-Arab1, and Shatt Al-Arab2). Polycyclic aromatic hydrocarbons (PAHs) were analyzes by using capillary gas chromatography. The results of PAHs shown in two pattern low and high molecular weight. The total PAHs ranged between 79.141 ng/g at station No. 6 to 3.830 ng/g at station No. 3. The rush to develop industries across the globe accelerates environmental damage brought on by many contaminants, including PAHs. Organic compounds in the PAHs class have two or more aromatic rings. PAHs can be pyrogenic, petrogenic, or biogenic depending on how they develop. Pyrogenic PAHs are produced when various fuels, oil and gas, waste, or other organic materials like fume from oil industries in the area. The investigation showed two patterns of sources petrogenic and pyrogenic with the petrogenic source predominating according to the ratios (low molecular weight/high molecular weight), anthracene/(anthracene+phenanthrene) and fluoranthene/(fluoranthene+pyrene). Additionally, findings indicated that sediment pollution is of a moderate pollution. By adhering to sedimentary particles, PAHs get into the sediments. Based on the physicochemical characteristics of each fraction and the surrounding environment, sediments also serve as a source for some contaminants that re-enter the water column. Lighter PAHs predominated in water samples, while heavier compounds predominated in sediment samples, according to several studies. In addition, it is difficult to remove the high concentrations of PAHs in riverine sediments brought on by industrial activity. While other research indicated significant PAHs pollution in a variety of global environments. Due to the fact that such research helps to lessen the obvious shortage of information regarding such pollutants in Iraqi rivers, this study gives as the baselines for coming research.

Polycyclic aromatic hydrocarbons in the Upper Cretaceous lacustrine deposits from the Songliao Basin (NE China): Implications for wildfires and paleoclimate

Changes in wildfires and paleoclimate during the Late Cretaceous have been widely discussed in the literature, yet terrestrial evidence for these changes is temporally limited. This study presents biomarker evidence for wildfires and paleoclimate using polycyclic aromatic hydrocarbons (PAHs) from drill core J79 of the Nenjiang Formation (K2n1+2, boundary at about 83.3 Ma) deposited during the Late Santonian in the Songliao Basin, NE China. A variety of di-ring to hepta-ring aromatic hydrocarbons, including pyrogenic-derived, petrogenic-derived and mixed PAHs, was identified in the lacustrine deposits using gas-chromatography mass-spectrometry. According to fluorene and its derivates, the PAHs in the K2n1 were dominantly preserved under an anoxic water column, with a shift to preservation under a weakly oxidizing water column (around 83.3 Ma) in the lower part of K2n2. The occurrence of higher-plant-derived PAHs (e.g., retene, simonellite, cadalene, perylene and 6-isopropy-1-isohexyl-2-methylnaphthalene) is as probable plant fingerprint, representing a relatively humid condition and a semi-humid to arid paleoclimate condition during the lower part of K2n1 and lower part of K2n2 and during the upper part of K2n1, respectively. Sharp increases in the abundance of pyrogenic PAHs compounds (e.g., benzo[h]fluoranthenes, benzo[e]pyrene, and coronene) are interpreted as indicators of intense wildfires in the K2n. The scale of fire events in the lower part of K2n1 and lower part of K2n2 was larger than that in the upper part of K2n1. This change in wildfire extent may have been caused by the wetter climate stimulating the growth of sufficient biomass to fuel large wildfires. Therefore, the availability of fuel likely played an important role in controlling fire frequency during the Late Cretaceous.

Spatially calibrating polycyclic aromatic hydrocarbons (PAHs) as proxies of area burned by vegetation fires: Insights from comparisons of historical data and sedimentary PAH fluxes

Many regions worldwide have experienced increasing wildfire activity in recent years and climate changes are predicted to result in more frequent and severe fires. Reconstruction of past fire activity offers paleoenvironmental context for modern and future burning. Pyrogenic polycyclic aromatic hydrocarbons (PAHs) have been increasingly used as a molecular biomarker for fire occurrence in the paleorecord and offer opportunity for nuanced reconstructions of fire characteristics. A suite of PAHs is produced during combustion, and the emission amount and assemblage is influenced by many variables including fuel type, fire temperature, and oxygen availability. Despite recent advances in understanding the controls and taphonomy of these biomass burning markers, the spatial scale of this proxy is unknown. In this paper, measurements of PAH fluxes preserved in a lake sediment archive from the Sierra Nevada, California were compared with a historical geographic information system (GIS) dataset of area burned up to 150 km distance from the lake to determine the spatial scales for which these biomarkers are reliable proxies of biomass burning. The PAH fluxes in the Swamp Lake sediments record a change in the relative anthropogenic and pyrogenic sourcing of PAHs. Anthropogenic pollution sources could explain why some PAHs (fluoranthene (Fl), pyrene (Py), benz[a]anthracene (BaA), retene (Ret), benzo[a]pyrene (BaP), dibenzo[a,h]anthracene (DA) and ideno[1,2,3-cd]pyrene (IP)) did not correlate with area burned within 150 km. This indicates that individual PAHs may have different efficacies in recording area burned and be more susceptible to masking of fire signals by pollution sources. Despite these complications, we find that the PAHs naphthalene (Na), acenaphthene (Ace), fluorene (F), and anthracene (An) are reliable local proxies of area burned (within 40 km), whereas the PAHs phenanthrene (Phe), chrysene (Ch), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), and benzo[g,h,i]perylene (Bghi) are both reliable local (within 36 km) as well as more regional (as much as 75 km for phenanthrene (Phe), chrysene (Ch), and benzo[g,h,i]perylene (Bghi) or 150 km for benzo[b]fluoranthene (BbF) and benzo[k]fluoranthene (BkF)) area burned proxies. Comparisons of PAH fluxes with charcoal accumulation rates in the same sediments suggest that pyrogenic particulate transport modulates low to mid-molecular weight PAHs via adsorption. Overall, the results show that PAH records integrate a combination of spatial signals of area burned and measurement of individual PAHs may enable cross-scale paleofire reconstructions.

Quantitative analysis and contamination profiles of PCBs, OCPs, and PAHs in black-tailed gull eggs in the Republic of Korea.

The simultaneous determination of 8 polychlorinated biphenyls (PCBs), 23 organic chlorine pesticides (OCPs), and 35 polycyclic aromatic hydrocarbons (PAHs) in black-tailed gull eggs was described using ultrasound-assisted extraction and gas chromatography-tandem mass spectrometry (GC-MS/MS). The ranges of the lower limits of detection for PCBs, OCPs, and PAHs were 0.006-0.029, 0.01-0.10, and 0.01-0.20μgkg-1, respectively. The intraday precision was in the range of 0.650-12.9% and the intraday accuracy was in the range of 86.6-113%. When the proposed method was used to analyze the target compounds in gull eggs collected from six sites in the Republic of Korea, the analytical results demonstrated concentration ranges of 113.32-394.07µgkg-1 for total PCBs, 422.92-1082.09µgkg-1 for total OCPs, and 134.50-231.27µgkg-1 for total PAHs in the samples. The PCA results for PAHs and OCPs were well differentiated by sampling site, whereas those for PCBs differed little by sampling site. There were more pyrogenic PAHs in the West Sea and the South Sea with many industrial areas than in the East Sea with few industrial areas. Differences in the OCP patterns of samples from the West Sea close to China were considered to be related to the use of DDT in China until recently. PCBs were accumulated in the samples regardless of region, so there was no significant difference in the PCB patterns between the samples obtained from the three Seas.

Urbanizing with or without nature: pollution effects of human activities on water quality of major rivers that drain the Kumasi Metropolis of Ghana.

The effects of urbanization such as population upsurge, increased industrialization, urban agriculture, and rural-urban migration of persons exert pressure on the limited water resources in most cities. This study investigated the impact of human activities on the water and sediment quality of the three main rivers (Wiwi, Subin, and Suntre) in Kumasi, the second-largest city in Ghana. The physicochemical parameters and the concentrations of contaminants, including heavy metals, polycyclic aromatic hydrocarbons, pesticide residues, and microbial loads in the rivers, were linked to the specific human activities at the riverbanks. While all the 37 pesticide residues investigated in river sediments had concentrations below the detection limits (0.005mg/kg for organochlorines, 0.010mg/kg for organophosphates, and 0.010mg/kg for synthetic pyrethroids), the study showed that the sediments are polluted with petrogenic and pyrogenic polycyclic aromatic hydrocarbons. River Subin, the most polluted among the three rivers, recorded benzo[e]pyrene concentrations up to 47,169µg/kg. The geoaccumulation index and concentration factors show that the rivers are highly contaminated with metals such as cadmium, chromium, mercury, and arsenic and are related to human activities. The microbial quality of the rivers was poor, recording specific microbial loads of 6.8, 4.1, and 1.5 × 107 counts/100mL respectively for Wiwi, Subin, and the Suntre Rivers. The three water bodies are therefore not suitable for recreational and irrigational purposes.

The significance of pyrogenic polycyclic aromatic hydrocarbons in Borneo peat core for the reconstruction of fire history.

The reconstruction of fire history is essential to understand the palaeoclimate and human history. Polycyclic aromatic hydrocarbons (PAHs) have been extensively used as a fire marker. In this work, the distribution of PAHs in Borneo peat archives was investigated to understand how PAHs reflect the palaeo-fire activity. In total, 52 peat samples were analysed from a Borneo peat core for the PAH analysis. Pyrogenic PAHs consist of 2–7 aromatic rings, some of which have methyl and ethyl groups. The results reveal that the concentration of pyrogenic PAHs fluctuated with the core depth. Compared to low-molecular-weight (LMW) PAHs, the high-molecular-weight (HMW) PAHs had a more similar depth variation to the charcoal abundance. This finding also suggests that the HMW PAHs were mainly formed at a local fire near the study area, while the LMW PAHs could be transported from remote locations.