Human activity and climate change are altering natural rates and intensities of wildfire, but the scale and extent of burning prior to the modern era are poorly understood. Paleofire activity may be reconstructed using a variety of records (e.g., charcoal in lake sediments, burn scars on tree rings), but these are not available in all environmental settings. Here we investigate the utility of a novel paleofire proxy: trace pyrogenic organic compounds in stalagmites. Polycyclic aromatic hydrocarbons (PAHs) are linked to burning of biomass and are transported downward through soil and bedrock by infiltrating rainwater and incorporated into stalagmites in underlying caves where they are preserved. In order to test links between the stalagmite PAHs and fire above the cave, we performed a series of experiments using PAH distributions at KNI-51, a shallow cave located in tropical Western Australia, where bushfire is a regular occurrence. First, the possibility of surface contamination was evaluated by measuring PAH abundances and distributions in sequential digestions and by considering other possible additional sources, such as regional oil and gas fields or proximal combustion of fossil fuels. Second, PAHs were measured in soils above the cave and in sediments from the stalagmite chamber floor as possible sources of these organic compounds, and at near annual resolution in three aragonite stalagmites to evaluate the degree of deposition and conservation. Third, possible non-pyrogenic sources of organic compounds were evaluated through alkane distribution and specific m/z ratios. Fourth, signal replication of PAHs was tested in two coeval stalagmites. Fifth, satellite-mapped fire scars were used to examine the relationship between stalagmite PAH abundances and proximity of burning to the cave. The results support the hypothesis that PAHs in KNI-51 stalagmite carbonate reflect paleofire activity within 3 km of the cave, and thus that stalagmites can serve as an important new high resolution proxy for landscape-scale fire activity. Given that karst is present in many fire-prone environments, and that stalagmites can be precisely dated and may grow continuously for millennia, the potential utility of a stalagmite-based paleofire proxy is high.

The history of human management of bushfire in Australia dates to at least 50 kyr BP but at the end of the 18th century, the arrival of European settlers disrupted indigenous management, leading to changes in patterns of fire regimes, which likely contributed to the decline of land mammals and fire-sensitive plants. Lake sediments and tree scars record these shifts across many parts of the continent. However, the fire-prone tropical savannas of north­western Australia lack such long-term, high-resolution paleofire archives. As a result, our understanding of fire prior to the arrival of European pastoralists in this area in the late 19th century are sparse, heterogeneous, and often poorly resolved. The region does contain karst areas, and stalagmites are being investigated as paleofire proxies. Paleofire reconstruction from stalagmites is in its infancy, but several recent studies investigated Holocene fire activity through various geochemi­cal proxies. Here, we present the first high-resolution paleofire record obtained from polycyclic aromatic hydrocarbons (PAHs) in stalagmites, encompassing most of the last millennium (CE ~1100-2009). Using this method, we can define the timing and intensity of fires proximal to the cave. Cave KNI-51, located in the Kimberley region of north-central Australia, is the ideal site for this pilot study. Previous U-Th dating of KNI-51 stalagmites has yielded high-precision age models and revealed fast growth (1-2 mm/yr), that together offer the possibility of near annual resolution. The cave is shallow, formed in permeable and fractured limestone and overlain by thin and poorly developed soils. From our data we infer short residence times for PAHs in soil over the cave and long time preservation in stalagmites. A strong positive correlation exists between PAH abundance and satellite data of burn scars in the CE 2000-2009 period using a 3 km buffer around KNI-51. Our results suggest an increase in the frequency of low intensity fire beginning around CE 1880, coincident with the arrival of European pastoralists to the Kimberley. In contrast, our data suggest few high intensity fires since CE 1550 relative to the first half of the millennium. Comparison with oxygen isotope data from the same stalagmites also allows an examination of (multi)decadal shifts in rainfall and fire activity.

Polycyclic aromatic hydrocarbons have widely been conjectured to be ubiquitous in space, as supported by the recent discovery of two isomers of cyanonaphthalene, indene, and 2-cyanoindene in the Taurus molecular cloud-1 using radioastronomy. Here, the photoionization dynamics of 1-cyanonaphthalene (1-CNN) are investigated using synchrotron radiation over the h = 9.0-19.5 eV range, revealing that prompt autoionization from the plasmon resonance dominates the photophysics for h? = 11.5-16.0 eV. Minimal photo-induced dissociation, whether originating from an excited state impulsive bond rupture or through internal conversion followed by a statistical bond cleavage process, occurs over the microsecond timescale (as limited by the experimental setup). The direct photoionization cross section and photoelectron angular distributions are simulated using an ezDyson model combining Dyson orbitals with Coulomb wave photoejection. When considering these data in conjunction with recent radiative cooling measurements on 1-CNN, which showed that cations formed with up to 5 eV of internal energy efficiently stabilize through recurrent fluorescence, we conclude that the organic backbone of 1-CNN is resilient to photodestruction by VUV and soft XUV radiation. These dynamics may prove to be a common feature for the survival of small polycyclic aromatic hydrocarbons in space, provided that the cations have a suitable electronic structure to support recurrent fluorescence.

We investigate the possibility to use polycyclic aromatic hydrocarbons in stalagmites as proxies for paleofires at KNI-51, a shallow cave located in tropical Western Australia, where bushfire is a regular occurrence. In order to test links between the stalagmite PAHs and fire above the cave, we performed a series of experiments using PAH distributions in stalagmite aragonite, sediment from the cave and overlying soil. In addition, the possibility of surface contamination was evaluated by measuring PAH abundances and distributions in sequential digestions. PAHs were measured in soils above the cave, in sediments from the stalagmite chamber floor as possible sources of these organic compounds, and at near annual resolution in three aragonite stalagmites to evaluate the degree of deposition and conservation. Signal replication of PAHs was also tested in two coeval stalagmites. The results support the hypothesis that PAHs in KNI-51 stalagmite carbonate reflect paleofire activity within 3 km of the cave, and thus that stalagmites can serve as an important new high resolution proxy for landscape-scale fire activity. Given that karst is present in many fire-prone environments, and that stalagmites can be precisely dated and may grow continuously for millennia, the potential utility of a stalagmite-based paleofire proxy is high.

This research study aims to investigate the causes of the particles emitted by a spark ignition engine fueled with hydrogen. The experiments were carried out on a single cylinder 250 cm3 direct injection spark ignition engine. Two operating conditions at 2000 rpm both full and low load, representative of typical urban conditions, were investigated. A physical characterization of the particles, size and number, was performed through an Engine Exhaust Particle Sizer coupled to a single diluter. Chemical characterization was carried out on the condensed exhaust. The simultaneous analysis of the physical properties and their chemical characterization allows to point out not only the role of the oil on the particle emissions but also to give an important information on its state/composition, if it was unburned and oxidized. Particles were detected with conventional spectrometer at low load while at high load the noise signal ratio is too high to distinguish the presence of particles. More detailed chemical techniques highlighted the presence of PAH, alkyl-PAHs, oxy-PAHs and unburned hydrocarbon in the exhaust due to the mineral oil.

Recent developments in speleothem science are showing their potential for paleofire reconstruction through a variety of inorganic and organic proxies including trace metals (1) and the pyrogenic organic compound levoglucosan (2). Previous work by Argiriadis et al. (2019) presented a method for the analysis of trace polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in stalagmites (3). These compounds reflect biogeochemical processes occurring at the land surface, in the soil, and in the cave. PAHs are primarily related to combustion of biomass while n-alkanes, with their potential for vegetation reconstruction (4), provide information on fuel availability and composition, as well as fire activity. These organic molecules are carried downward by infiltrating water and incorporated into speleothems (5), thereby creating the potential to serve as novel paleofire archives. Using this approach, we developed a high-resolution stalagmite record of paleofire activity from cave KNI-51 in tropical northwestern Australia. This site is well suited for high resolution paleofire reconstruction as bushfire activity in this tropical savanna is some of the highest on the continent, the cave is shallow and overlain by extremely thin soils, and the stalagmites are fast-growing (1-2 mm yr-1) and precisely dated. We analyzed three stalagmites which grew continuously in different time intervals through the last millennium - KNI-51-F (CE ~1100-1620), KNI-51-G (CE ~1320-1640), and KNI-51-11 (CE ~1750-2009). Samples were drilled continuously at 1-3 mm resolution from stalagmite slabs, processed in a stainless-steel cleanroom to prevent contamination. Despite a difference in resolution between stalagmites KNI-51-F and -G, peaks in the target compounds show good replication in the overlapping time interval of the two stalagmites, and PAH abundances in a portion of stalagmite KNI-51-11 that grew from CE 2000-2009 are well correlated with satellite-mapped fires occurring proximally to the cave. Our results suggest an increase in the frequency of low intensity fire in the 20th century relative to much of the previous millennium. The timing of this shift is broadly coincident with the arrival of European pastoralists in the late 19th century and the subsequent displacement of Aboriginal peoples from the land. Aboriginal peoples had previously utilized "fire stick farming", a method of prescribed, low intensity burning, that was an important influence of ecology, biomass, and fire. Prior to the late 1800s, the period with the most frequent low intensity fire activity was the 13th century, the wettest interval of the entire record. Peak high intensity fire activity occurred during the 12th century. Controlled burn and irrigation experiments capable of examining the transmission of pyrogenic compounds from the land surface to cave dripwater represent the next step in this analysis. Given that karst is present in many fire-prone environments, and that stalagmites can be precisely dated and grow continuously for millennia, the potential utility of a stalagmite-based paleofire proxy is high.

metodologia CLASSIFICA: G01N DATA DEPOSITO: 08/02/2021

Assessing the sources and accumulation patterns of polycyclic aromatic hydrocarbons (PAHs) in corals is critical, as they threaten coral ecosystem resilience in addition to other anthropogenic pressures. We determined acenaphthene, fluorene, fluoranthene, and pyrene concentration in the skeleton and soft tissue of 7 adult and 29 old specimens of the non-zooxanthellate coral Leptopsammia pruvoti from the Mediterranean Sea. Leptopsammia pruvoti accumulated 2-72 times higher PAH concentrations than the previously investigated zooxanthellate Balanophyllia europaea living at the same site at shallower depth, likely in relation to the different trophic strategy. Low molecular weight PAHs were preferentially accumulated compared to high molecular weight PAHs. Detected PAHs were mainly petrogenic, consistently with local pollution sources. Populations of L. pruvoti immobilized PAHs in the skeleton 3-4 orders of magnitude more efficiently than B. europaea. This highlights the need to investigate other non-zooxanthellate species, which represent the majority of Mediterranean scleractinians, but are widely overlooked with respect to the few zooxanthellate species.

Superhydrogenated polycyclic aromatic hydrocarbons (PAHs) have been suggested to catalyze the formation of H-2 in certain regions of space, but it remains unclear under which circumstances this mechanism is viable given the reduced carbon backbone stability of superhydrogenated PAHs. We report a laboratory study on the stability of the smallest pericondensed PAH, pyrene (C16H10+N, with N = 4, 6, and 16 additional H atoms), against photodestruction by single vacuum ultraviolet photons using the photoelectron-photoion coincidence technique. For N = 4, we observe a protective effect of hydrogenation against the loss of native hydrogens, in the form of an increase in the appearance energies of the C16H9+ and C16H8+ daughter ions compared to those reported for pristine pyrene (C16H10). No such effect is seen for N = 6 or 16, where the weakening effect of replacing aromatic bonds with aliphatic ones outweighs the buffering effect of the additional hydrogen atoms. The onset of fragmentation occurs at similar internal energies for N = 4 and 6, but is significantly lower for N = 16. In all three cases, H-loss and CmHn-loss (m >= 1, carbon backbone fragmentation) channels open at approximately the same energy. The branching fractions of the primary channels favor H-loss for N = 4, CmHn-loss for N = 16, and are roughly equal for the intermediate N = 6. We conclude that superhydrogenated pyrene is probably too small to support catalytic H-2-formation, while trends in the current and previously reported data suggest that larger PAHs may serve as catalysts up to a certain level of hydrogenation.

Il report descrive alcune valutazioni effettuate su dati relativi a filtri per la rimozione di particolato in aria ambiente, installati dalla società AGT S.r.l. su autobus Conerobus circolanti nelle città di Ancona e Jesi nel periodo febbraio-maggio 2021.

The mechanism of soot particle formation in combustion can be depicted as the early formation of Polycyclic Aromatic Hydrocarbons (PAHs), their self-assembly into large aromatic structures and clusters and finally the coagulation and rearrangement of such clusters to form soot particles. From PAHs to clusters and finally to soot particles, the mass of the formed entities moves from 128-700 Da of the PAH class, to about 1000 - 3000 Da of the PAH clusters (corresponding to an equivalent spherical size of 1 - 3 nm), and finally to masses larger than 3000 Da (corresponding to 4 - 20 nm spherical particle sizes) for soot. During particle nucleation, particularly in correspondence to the early changes of particle size, the spectral light absorption of carbon nanoparticles changes. Molecular PAHs, the building blocks for solid soot particles, comprise a variety of compounds and moieties. As recently visualized by high-resolution atomic force microscopy (HR-AFM), a large fraction of the PAH molecules contains fused six-ring units organized in almost entirely peri-condensed structures with zigzag and free edges. Many molecules exhibit one or two arm-chair edges while only very few present bay-edges. Some others have archipelago-type/cross-linked structures. Several molecules exhibit aliphatic branches and many molecules contain penta-rings on their periphery while a smaller fraction have penta-rings (partially) embedded into the aromatic structure. Some molecules have odd carbon atom numbers (phenalenyl-like) and contains unpaired ?-electrons within the aromatic structure, as well as those with peripheral penta-rings. The presence of unpaired ?-electrons could have importance at the onset of soot formation, when gas-phase molecules and weak clusters convert to a condensed, solid-phase material. Two types of bonding processes might occur- A ?-stacking mechanism (pancake bonding) that forms multi-electron/multi-center delocalized bonds, which are covalent-like, with shorter intermolecular distances and slightly stronger interactions with respect to van der Waals interactions. A second type of bonding is conventional ?-bond formation, with longer distance and weaker strength than regular C-C bond. In this work, we use density functional theory (DFT) with hybrid functional and localized Gaussian basis set (B3LYP/6-31G**) to calculate binding energies and HOMO-LUMO gaps of some PAH molecules and radicals identified by HR-AFM, and their homogeneous clusters. The cluster structure is found to impact the HOMO-LUMO gap with pancake configurations lowering the gap values. We provide theoretical evidence about the morphology of the PAH clusters that may be responsible for particle nucleation.

Volatile organic compounds (VOC) and polycyclic aromatic hydrocarbons (PAH), emitted in the environment from a wide range of combustion sources, are hazardous to human health and considered important precursors of both primary and secondary particulate pollutants. In the present work, light hydrocarbons up to C9, as main components of combustion-derived VOC, and PAH produced in fuel-rich conditions of premixed ethylene flames were analyzed by implementing a molecular-beam time of flight mass spectrometer (MB-TOFMS), purposely built for on-line fast monitoring of the environmental impact of combustion systems. The reliability of the MB-TOFMS was preliminarily verified on a slightly-sooting flame, comparing the results with those obtained by batch sampling and gas chromatographic techniques. Electron ionization (EI) and multi-photon ionization (MPI) were used as MB-TOFMS sources and tested on combustion gases of a no-sooting premixed ethylene flame where VOC and PAH are present in traces not detectable with batch sampling and conventional analytical techniques. The mass identification accuracy was improved and guaranteed by systematically performing internal mass calibration, exploiting the formation of "in situ" clusters from combustion water in the molecular beam apparatus. Selective and sensitive monitoring of light hydrocarbons and PAH, derived from oxidation and pyrolysis reactions featuring combustion, was shown to be especially effective when using the MB-TOFMS equipped with MPI source. This technique showed to be effective also for the detection of radical species that are important for the risk assessment of aerosol and fundamental understanding of aerosol chemistry at a molecular level.

Heavy metals and PAHs were measured in animal foodstuffs from Augusta-Melilli-Priolo area in order to evaluate the potential human health risk associated to their consumption. All heavy metals were detected in seafood products while most of them were <LOD in beef, pork and milks samples. Particularly, seafood products registered higher values of total arsenic (As), mercury (Hg) and lead (Pb) than other food categories, while beef and pork showed higher content of zinc (Zn). Cadmium (Cd) and Pb were below the tolerable limits reported by the European Union in foodstuffs (1) while mercury exceed the threshold value in seafood products. Among the PAHs, chrysene (Chr) was detected in all the terrestrial foodstuffs with higher concentrations found in raw milks. Small quantity of benz(a)anthracene (BaA) were also found in this food. The health risk for consumers was assessed for five age categories of consumers calculating the estimated weekly intake (EWI), the target hazard quotient (THQ) and the cancer risk (CR) for each contaminant. Moreover, the margin of exposure (MOE) was estimated for PAHs. The EWI(Hg)related to seafood products intake exceeded the Provisional Tolerable Weekly Intake (PTWI) recommended by the European Food Safety Authority. The THQ(Hg)was >1 for baby, children and teenagers, indicating a non-carcinogenic risk for these age categories by seafood ingestion. The CR(As)overcame 1*10(-5)for almost age categories (except "baby") and for elderly, by seafood and beef ingestions respectively. Moreover, the MOE for PAHs showed a certain cancer risk for "baby" related to cow milk ingestion.

The study of the transition from molecular to particle-like species involved in soot inception needs experimental strategies aiming to measure high molecular mass structures that could be important also for their effect on environment and human health. In this work, we have investigated the carbon particulate selectivity involved in the thermophoretic deposition used for the first time as a direct and fast sampling of high molecular weight aromatic species formed at the inception stage in an ethylene heavily sooting flame. Gravimetric analysis along with mass spectrometry, UV-Visible and fluorescence spectroscopy showed that the dichloromethane-extract of carbon particulate matter thermophoretically deposited on the substrate was much less than that sampled by a conventional water-cooled probe as it is composed only of high molecular weight condensed phases (C >= 22-24). Thermophoretic deposition is demonstrated to pre-separate, already at the sampling step, soot precursors of high molecular weight allowing their further analysis without the interference of the more abundant light polycyclic aromatic compounds (C < 22-24). These high molecular weight aromatic species presented interesting optical properties in terms of size and fluorescence emission peaked in the blue-region that could be of interest for carbon dots application. Size exclusion chromatography of particulate coupled with UV-Visible spectroscopy showed the presence of some aggregates already at the beginning of soot formation to be taken into account as ruling the optical properties of the whole carbon particulate matter.

The Great Acceleration of the anthropogenic impact on the Earth system is marked by the ubiquitous distribution of anthropogenic materials throughout the global environment, including technofossils, radionuclides and the exponential increases of methane and carbon dioxide concentrations. However, personal care products as direct tracers of human domestic habits are often overlooked. Here, we present the first research combining fragrances, as novel personal care products, and polycyclic aromatic hydrocarbons (PAHs) as combustion and industrial markers, across the onset of the Great Acceleration in the Elbrus, Caucasus, ice core. This archive extends from the 1930s to 2005, spanning the profound changes in the relationship between humans and the environment during the twentieth century. Concentrations of both fragrances and PAHs rose throughout the considered period, reflecting the development of the Anthropocene. However, within this rising trend, remarkable decreases of the tracers track the major socioeconomic crises that occurred in Eastern Europe during the second half of the twentieth century.

Organic compounds stored in sedimentary archives, such as peat bogs, can provide information on numerous processes related to paleoenvironmental changes. The application of multi-proxy methods permits to overcome the limits imposed by reduced sample size, although complex matrices need particular attention to some analytical aspects. Here, we developed and validated a method for the simultaneous determination of 27 n-alkanes, 18 polycyclic aromatic hydrocarbons and 6 sterols in peat by optimizing the extraction and cleanup procedures. The method was evaluated in terms of accuracy, recovery, detection limits and according to green chemistry assessments. In the view of future application in high-resolution multi-proxy geochemical paleoenvironmental studies, it was applied to a test batch of eight samples from the Coltrondo ombrotrophic peatland, located in northern Italy. The multi-proxy approach allowed extracting less than 1 g of dry sample. The stability of proxies over time was assessed by analyzing samples in a wide time and depth range. Results were in agreement with existing historical records and represent the first peat biomarker data for the area.

In the present work fast pyrolysis of coal in N and CO atmospheres was studied in a drop tube reactor (DTR) and in a heated strip reactor (HSR). In the DTR the volatiles generated by coal pyrolysis were entrained in a hot gas stream and were collected at the reactor outlet by tar traps. In the HSR, the volatiles were ejected from the hot coal particles into a cool environment and the condensable species, including primary tar, deposited and/or condensed on a glass bridge located above the heated strip. The composition of tars produced in the two reactors was compared to study the role of gas tar reactions in soot inception, and reference compounds for each class of tar species produced were identified. In the DTR the formation and growth of polycyclic aromatic hydrocarbons (PAH) were found higher than in the HSR. Soot formation occurred only in the DTR, being negligible in the HSR. It was concluded that the hot gas environment of the DTR favours secondary tar reactions, formation of PAH and eventually soot, while in the HSR this path was prevented due to prompt cooling down of volatiles. The presence of large concentration of CO in the pyrolysis atmospheres further promoted formation of heavy PAH and soot in the DTR, but not in the HSR, where the cooler environment limits soot-CO reactions in the gas phase.

Polycyclic aromatic hydrocarbons (PAHs) are widespread and harmful environmental pollutants that threaten marine ecosystems. Assessing their level and source is crucial to estimate the potential risks for marine organisms, as PAHs represent an additional threat to organism resilience under ongoing climatic change. Here we applied the QuEChERS extraction method to quantify four PAHs (i.e. acenaphthene, fluorene, fluoranthene, and pyrene) in three biological compartments (i.e. skeleton, tissue, and zooxanthellae symbiotic algae) of adult and old specimens of a scleractinian coral species (Balanophyllia europaea) that is widespread throughout the Mediterranean Sea. A higher concentration of all four investigated PAHs was observed in the zooxanthellae, followed by the coral tissue, with lowest concentration in the skeleton, consistently with previous studies on tropical species. In all the three biological compartments, the concentration of low molecular weight PAHs was higher with respect to high-molecular weight PAHs, in agreement with their bioaccumulation capabilities. PAH concentration was unrelated to skeletal age. Observed PAHs were of petrogenic origin, reflecting the pollution sources of the sampling area. By coupling PAH data with population age structure data measured in the field, the amount of PAHs stored in the long term (i.e. up to 20 years) in coral skeletons was quantified and resulted in 53.6 ng m of acenaphthene, 69.4 ng m of fluorene, 2.7 ng m of fluoranthene, and 11.7 ng m of pyrene. This estimate provides the basis for further assessments of long-term sequestration of PAHs from the marine environment in the whole Mediterranean, given the widespread distribution of the investigated coral species.

Diesel engine exhausts from a common rail 3.0 L F1C diesel engine were analyzed at two different load conditions of the WLTC testing cycle downstream of both the diesel particulate filter (DPF) and selective catalytic reactor (SCR) to verify their effect on the characteristics of carbon particulate matter. An array of chemical, physical and spectroscopic techniques (gas chromatography coupled with mass spectrometry (GC-MS), mobility analyzer, UV-Visible absorption and fluorescence spectroscopy) was applied for characterizing polycyclic aromatic hydrocarbons (PAH), heavy aromatic compounds and soot, constituting the particulate matter (PM) sampled from the exhaust. The engine was operated in half load (HL) (188 Nm, representing the more common condition for engine in urban traffic) and full load (FL) (452 Nm, representing the best performance of the engine operation) conditions, at the same engine speed (2000 rpm). Soot formation was enhanced in HL condition, with respect to FL, but, just because of the much lower soot amount, the after-treatment systems in this last condition resulted to be less efficient in the soot abatement. Indeed, the abatement through DPF was about 40% lower in the FL condition with respect to HL condition, and any significant further concentration decrease was found after SCR, in both conditions. By contrast, PAH concentration after DPF abatement was found to be higher in the HL with respect to FL condition. A further PAH concentration decrease of about 30% was found after the SCR in the HL condition whereas in FL the reduction was only about 5-6%. Also the heavy aromatic compounds having molecular weight above the GC-MS detection limit (300 u), were mitigated by SCR. Therefore, SCR did not cause a further soot reduction, whereas it was effective in largely reducing PAH and heavy aromatics emissions, especially in the lower temperature condition featuring the half-load condition, when combustion efficiency is worse. Moreover, SCR system reduced the emission of small particles probably due to an enhanced agglomeration of particles, with beneficial effect on the harmfulness to human health.