60 research outputs found
Specific molecular markers in lake sediment cores for biomass burning reconstruction during the Holocene
Get PDFIl fuoco gioca un ruolo importante nel sistema terrestre influenzando gli ecosistemi e il clima, ma anche il clima influenza il fuoco. Il sistema (discorso) diviene più complesso quando gli umani hanno iniziato ad usare il fuoco come uno strumento (in modo routinario). Scopo principale della ricerca paleoincendiaria è lo studio delle interazioni fra l’uomo, il fuoco e il clima. Comprendere come questi tre aspetti sono cambiati nel passato aiuterà a prevedere le interazioni fra clima, fuoco e l’uomo nel futuro. L’uso di carote di sedimento lacustre come archivi naturali per la ricostruzione della passata attività incendiaria attraverso il conteggio delle particelle di charcoal è un metodo ben consolidato. Il presente lavoro di tesi è dedicato alla valutazione e applicazione di indicatori molecolari organici per l’individuazione di eventi di biomass burning: levoglucosan, mannosan e galactosan sono usati come proxies per la ricostruzione della passata attività incendiaria in sedimenti di lago nel corso dell’Olocene. Inizialmente ho sviluppato un nuovo metodo analitico basato su tecniche di cromatografia a scambio ionico ad alte prestazioni interfacciate alla spettrometria di massa per la separazione e quantificazione di questi tre monosaccaridi anidri in sedimenti lacustri. L’applicabilità di questo metodo analitico è stata dimostrata confrontando i risultati relativi alla presenza di levoglucosan, mannosan e galactosan in alcuni campioni di sedimento provenienti dal Lago Kirkpatrick (New Zealand) con quelli relativi alle analisi di macroscopic charcoal. Successivamente ho applicato, con esito positivo, il suddetto metodo a sedimenti lacustri provenienti dal Lago Petén Itzá (Guatemala) per la ricostruzione dell’attività incendiaria su scala regionale durante l’Olocene. Abbiamo impiegato sia analisi di levoglucosan che di steroli fecali in carote provenienti dal Lago Transimeno (Italia) per ricostruire le interazioni fra il fuoco e la presenza umana durante l’Olocene, osservando bassa attività incendiaria durante il periodo Romano. Tale combinazione di tecniche dimostra che marker molecolari sono validi fire proxies quando analizzati in campioni di sedimento in diverse località Il confronto fra trend descritto dalle concentrazioni di levoglucosan, mannosan e galactosan e quello relativo al macroscopic charcoal nel Lago Kirkpatrick e nel Lago Petén Itzá suggerisce che i marker molecolari descrivono la storia dell’attività del fuoco su scala regionale e relativa ad incendi a basse temperature, a differenza del macroscopic charcoal che risulta essere un proxy su scala geografica piú locale. Sono inoltre stati confrontati i cambiamenti nella vegetazione (Lago Kirkpatrick e Lago Petén Itzá) e nel charcoal morphotypes (Lago Petén Itzá) con i rapporti fra levoglucosan/mannosan e levoglucosan/(mannosan+galactosan), suggerendo che tali rapporti potrebbero risultare utili strumenti per l’individuazione della biomassa combusta. Test di biodegradazione dimostrano una potenziale degradazione di levoglucosan, mannosan e galctosan quando si trovano dissolti in soluzione acquosa, ma la loro presenza in “antichi” campioni di sedimento suggeriscono che levoglucosan, mannosan and galactosan possono conservati per millenni quando questi si trovano legati a particelle nel sedimento. Sebbene esistano ancora incertezze, i risultati di questa ricerca suggeriscono che marker molecolari organici sono validi fire proxies su scala regionale e che il rapporto fra i loro isomeri può aiutare ad individuare cambiamenti nella vegetazione combusta
Perfluorinated compounds in marine surface waters: data from the Baltic Sea and methodological challenges for future studies
No full text
Environmental context.Perfluorinated compounds are man-made chemicals of emerging environmental concern because of their global distribution in water, air and biota. We investigate the distribution of these chemicals in surface water of the Baltic Sea, a unique ecosystem and the world’s largest body of brackish water. The observed contamination was of the same order of magnitude as classical persistent organic pollutants in the world’s oceans, and decreased with lower population density in the Baltic Sea catchments.
Abstract.Poly- and perfluorinated compounds (PFCs) are chemicals of emerging environmental concern. Except for very few coastal sites, PFC contamination of the Baltic Sea has not been investigated. In order to assess the PFC contamination of Baltic Sea water and evaluate the spatial distribution of PFCs, 74 surface water samples from the entire Baltic Sea were taken during two sampling campaigns in the summer of 2008 and analysed for PFCs. Of 40 analysed PFCs, 13 were detected at concentrations below 1 ng L–1, which indicates a rather low PFC contamination of Baltic Sea surface water. Usually, PFOA was the analyte observed in highest concentrations followed by PFNA, PFBS, and PFOS. PFC concentrations decreased from the Kattegat to the Bothnian Bay and the Gulf of Finland, reflecting the decreasing population density and thus the potential contamination in corresponding catchments or the decreasing influence of potentially contaminated North Sea water.
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Ombrotrophic Peat Bogs Are Not Suited as Natural Archives To Investigate the Historical Atmospheric Deposition of Perfluoroalkyl Substances
No full textAs ombrotrophic peat bogs receive only atmospheric input of contaminants, they have been identified as suitable natural archives for investigating historical depositions of airborne pollutants. To elucidate their suitability for determining the historical atmospheric contamination with perfluoroalkyl substances (PFAS), two peat cores were sampled at Mer Bleue, a bog located close to Ottawa, Canada. Peat cores were segmented, dried, and analyzed in duplicate for 25 PFASs (5 perfluororalkyl sulfonates (PFSAs), 13 perfluoroalkyl carboxylates (PFCAs), 7 perfluororalkyl sulfonamido substances). Peat samples were extracted by ultrasonication, cleaned up using a QuEChERS method, and PFASs were measured by HPLC-MS/MS. Twelve PFCAs and PFSAs were detected regularly in peat samples with perfluorooctane sulfonate (85-655 ng kg-1), perfluorooctanoate (150-390 ng kg-1), and perfluorononanoate (45-320 ng kg-1) at highest concentrations. Because of post depositional relocation processes within the peat cores, true or unbiased deposition fluxes (i.e., not affected by post depositional changes) could not be calculated. Apparent or biased deposition rates (i.e., affected by post depositional changes) were lower than measured/calculated deposition rates for similar urban or near-urban sites. Compared to PFAS production, PFAS concentration and deposition maxima were shifted about 30 years toward the past and some analytes were detected even in the oldest segments from the beginning of the 20th century. This was attributed to PFAS mobility in the peat profile. Considerable differences were observed between both peat cores and different PFASs. Overall, this study demonstrates that ombrotrophic bogs are not suited natural archives to provide authentic and reliable temporal trend data of historical atmospheric PFAS deposition. © 2012 American Chemical Society
Method for the determination of specific molecular markers of biomass burning in lake sediments
Get PDFFire has an influence on regional to global atmospheric chemistry and climate. Molecular markers of biomass burning archived in lake sediments are becoming increasingly important in paleoenvironmental reconstruction and may help determine the interaction between climate and fire activity. Here, we present a high performance anion exchange chromatography–mass spectrometry method to allow separation and analysis of levoglucosan, mannosan and galactosan in lake sediments, with implications for reconstructing past biomass burning events. Determining mannosan and galactosan in Lake Kirkpatrick, New Zealand (45.03°S, 168.57°E) sediment cores and comparing these isomers with the more abundant biomass burning markers levoglucosan and charcoal represents a significant advancement in our ability to analyze past fire activity. Levoglucosan, mannosan and galactosan concentrations correlated significantly with macroscopic charcoal concentration. Levoglucosan/mannosan and levoglucosan/(mannosan + galactosan) ratios may help determine not only when fires occurred, but also if changes in the primary burned vegetation occurred
Holocene fire history reconstruction using Tibetan lacustrine sediments
No full textThe important role that biomass burning plays in influencing the Holocene’s climate is still under discussion. The present work gives information about past biomass burning events in the Tibetan Plateau and helps to increase the understanding of the interaction between climate, humans and fire activity during Holocene. Asiatic area is one of the centers of the advent of agriculture and pastoralism, and it is a strategic area for understanding the interaction between human and fire during the Holocene. We reconstructed past biomass burning events and vegetation from sediments collected from lake Paru Co, a small moraine dammed lake located in the Tibetan Plateau at 4845 m above sea level. We extracted lake sediment samples by accelerate solvent extraction and analysed different organic molecular proxies by GC-MS and IC-MS. We used monosaccharide anhydrides, levoglucosan and its isomers, as proxies for biomass burning. These are specific molecular markers originated from the pyrolysis of cellulose showing significant fire events and indicate changes in burned fuel. Furthermore we analysed polycyclic aromatic hydrocarbons (PAH) as additional combustion proxies. For a better understanding of changes in vegetation and of human habitation at the lake shore we analysed n-alkanes and sterols. Comparing the data of this multi-proxy approach used in the studied area with climatic and meteorological literature data, reconstruction and contextualization of past fire events are possible: we can see the agreement between dry climate period and presence of more intense fire events, especially in the Early Holocene
Particle-size distribution of airborne poly- and perfluorinated alkyl substances
No full textEleven particle-size-segregated samples were taken to investigate the particle-size distribution of perfluoroalkyl substances (PFASs) using two five stage impactors in parallel. Samples were extracted with methanol and detected by HPLC/MS-MS. Investigation yielded reproducible results for the parallel samples over the entire sampling period. Particle-size distribution varied between perfluorooctane sulfonate (PFOS) and other perfluoroalkyl sulfonates (PFSAs), perfluorooctane carboxylate (PFOA) and other perfluoroalkyl carboxylates (PFCAs) and n-methyl-perfluorooctanesulfonamido ethanol (MeFOSE). Whereas PFOA and MeFOSE were predominantly observed in smallest size fraction (<0.14. μm), maximum PFOS mass fractions were observed in the coarser size fractions between 1.38 and 3.81. μm. The reason for this different behaviour remained unclear and indicated a complex atmospheric PFAS processing and sampling which should be further investigated and optimized, respectively.Eleven particle-size-segregated samples were taken to investigate the particle-size distribution of perfluoroalkyl substances (PFASs) using two five stage impactors in parallel. Samples were extracted with methanol and detected by HPLC/MS–MS. Investigation yielded reproducible results for the parallel samples over the entire sampling period. Particle-size distribution varied between perfluorooctane sulfonate (PFOS) and other perfluoroalkyl sulfonates (PFSAs), perfluorooctane carboxylate (PFOA) and other perfluoroalkyl carboxylates (PFCAs) and n-methyl-perfluorooctanesulfonamido ethanol (MeFOSE). Whereas PFOA and MeFOSE were predominantly observed in smallest size fraction (<0.14 μm), maximum PFOS mass fractions were observed in the coarser size fractions between 1.38 and 3.81 μm. The reason for this different behaviour remained unclear and indicated a complex atmospheric PFAS processing and sampling which should be further investigated and optimized, respectively
Two thousand years of boreal biomass burning recorded in the NEEM ice cores
Get PDFNew data from Greenland ice cores reveal a major peak in boreal biomass burning during the 1600s AD, presumably related to major regional droughts in Central Asia. This climate-related peak in fire activity is greater even than postindustrial biomass burning
Combining charcoal sediment and molecular markers to infer a Holocene fire history in the Maya Lowlands of Petén, Guatemala
Get PDFVegetation changes in the Maya Lowlands during the Holocene are a result of changing climate conditions, solely anthropogenic activities, or interactions of both factors. As a consequence, it is difficult to assess how tropical ecosystems will cope with projected changes in precipitation and land-use intensification over the next decades. We investigated the role offire during the Holocene by combining macroscopic charcoal and the molecular fire proxies levoglucosan, mannosan and galactosan. Combining these two different fire proxies allows a more robust understanding of the complex history of fire re-
gimes at different spatial scales during the Holocene. In order to infer changes in past biomass burning, we analysed a lake sediment core from Lake Peten Itza, Guatemala, and compared our results with millennial-scale vegetation and climate change available in the area. We detected three periods of high fire activity during the Holocene: 9500 e 6000 cal yr BP, 3700 cal yr BP and 2700 cal yr BP. We attribute the first maximum mostly to climate conditions and the last maximum to human activities. The rapid change between burned vegetation types at the 3700 cal yr BP fire maximum may result from human activity
Composti organici idrosolubili come indicatori nello studio dei processi di scambio atmosfera-neve in Antartide
Get PDFLa frazione organica è un’importante componente dell’aerosol atmosferico e i composti organici idrosolubili costituiscono un 40-60% del carbonio organico presente in atmosfera. Tali composti hanno una grande importanza ambientale in quanto possono influenzare l’igroscopicità delle particelle di aerosol e conseguentemente l’abilità di agire come nuclei di condensazione delle nubi.
I composti organici idrosolubili possono essere utilizzati come indicatori di specifiche sorgenti di emissione. Processi di trasporto a lunga distanza sono stati studiati utilizzando il levoglucosan, specifico indicatore di combustione di biomassa, [1], mentre la determinazione di amminoacidi e zuccheri nell’aerosol antartico ha permesso di investigare i processi di formazione e di trasformazione del bioaerosol [2,3]. L’Antartide rappresenta un ottimo laboratorio naturale perché risulta lontano da fonti antropogeniche ed emissioni continentali.
In questo studio sono state analizzate diverse classi di composti idrosolubili quali amminoacidi, metossifenoli, mono- e disaccaridi, alcol zuccheri, anidrozuccheri, specie anioniche e cationiche e acidi carbossibili in campioni di aerosol atmosferico e neve superficiale raccolti presso il sito costiero di Campo Faraglione vicino alla Stazione Mario Zucchelli (Antartide) durante la XXX spedizione italiana antartica (estate australe 2014-2015).
Il principale obiettivo di questo lavoro consiste nello studio dei processi di scambio atmosfera-neve al fine di individuare nuovi indicatori per lo studio delle carote di ghiaccio. La conoscenza dei processi di deposizione e di possibile degradazione delle specie chimiche nel manto nevoso è fondamentale per capire l’applicabilità di tali composti a studi paleoclimatici.
Questo lavoro è stato finanziato dal Programma Nazionale di Ricerche in Antartide (PNRA) mediante il progetto “Scambi e relazioni aria-neve per elementi in tracce e composti organici di interesse climatico” (2013/AZ3.04).
Bibliografia
[1] R. Zangrando et al., (2016), Science of the Total Environment 544, 606–616.
[2] E. Barbaro et al., (2015) Atmospheric Environment, 118, 134-144.
[3] E. Barbaro et al., (2015) Atmospheric Chemistry and Physics, 15, 5457–5469
Particle size distribution of inorganic and organic ions in coastal and inland Antarctic aerosol
Get PDFThe concentration and particle-size distribution of ionic species in Antarctic aerosol samples were determined to investigate their potential sources, chemical evolution, and transport. We analyzed aerosol samples collected at two different Antarctic sites: a coastal site near Victoria Land close to the Italian Research Base “Mario Zucchelli”, and another site located on the Antarctic plateau, close to Italian-French Concordia Research Station. We investigated anionic compounds using ion-chromatography coupled to mass spectrometry, and cationic species through capillary ion chromatography with conductometry. Aerosol collected close to the coast was mainly characterized by sea salt species such as Na+, Mg2+, and SO42−. These species represented a percentage of 88% of the total sum of all detected ionic species in the aerosol samples from the coastal site. These species were mainly distributed in the coarse fraction, confirming the presence of primary aerosol near the ocean source. Aerosol collected over the Antarctic plateau was characterized by high acidity, with nss-SO42−, NO3−, and methanesulfonic acid as the most abundant species. These species were mainly distributed in the <0.49 μm fraction, and they had a behavior of a typical secondary aerosol, where several chemical and physical processes occurred
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