Composti organici idrosolubili come indicatori nello studio dei processi di scambio atmosfera-neve in Antartide

La 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

Aerosol and snow transfer processes: An investigation on the behavior of water-soluble organic compounds and ionic species

The concentrations of water-soluble compounds (ions, carboxylic acids, amino acids, sugars, phenolic compounds) in aerosol and snow have been determined at the coastal Italian base "Mario Zucchelli" (Antarctica) during the 2014-2015 austral summer. The main aim of this research was to investigate the air-snow transfer processes of a number of classes of chemical compounds and investigate their potential as tracers for specific sources.The composition and particle size distribution of Antarctic aerosol was measured, and water-soluble compounds accounted for 66% of the PM10 total mass concentration. The major ions Na+, Mg2+, Cl- and SO42- made up 99% of the total water soluble compound concentration indicating that sea spray input was the main source of aerosol. These ionic species were found mainly in the coarse fraction of the aerosol resulting in enhanced deposition, as reflected by the snow composition.Biogenic sources were identified using chemical markers such as carboxylic acids, amino acids, sugars and phenolic compounds. This study describes the first characterization of amino acids and sugar concentrations in surface snow. High concentrations of amino acids were found after a snowfall event, their presence is probably due to the degradation of biological material scavenged during the snow event. Alcohol sugars increased in concentration after the snow event, suggesting a deposition of primary biological particles, such as airborne fungal spores. (C) 2017 Elsevier Ltd. All rights reserved

Methoxyphenols in Arctic seawater

METHOXYPHENOLS IN ARCTIC SEAWATER S. Padoan 1, E. Barbaro 1,2, R. Zangrando2, O. Karroca1, C. Barbante2, A. Gambaro1,2 1 Department of Environmental Sciences, Informatics and Statistics, University of Venice, Ca' Foscari, Via Torino 155, 30170 Venezia, Mestre, Italy 2 Institute for the Dynamics of Environmental Processes CNR, Via Torino 155, 30170 Venezia, Mestre, Italy Methoxyphenols are organic and semi-volatile compounds that are used as specific biomarkers of combustion events. These compounds are able to provide information about the type of combusted biomass [1]. Recently, several studies [2] have highlighted that the presence of methoxyphenols in polar areas are attributable not only to biomass burning but also to local marine sources. The purpose of the present work was to determine free phenolic compounds in both dissolved and particulate fractions in Arctic seawater samples. We analyzed 67 samples of coastal seawater collected near the coast line of Kongsfjord during the Arctic sampling campaign 2015. The quantitative determination has been performed using a HPLC-MS/MS method developed by Zangrando et al. [3]. Vanillic acid, vanillin, p-coumaric acid, syringic acid, isovanillic acid, homovanillic acid, syringaldehyde, acetosyringone and acetovanillone were determined. In dissolved phase there was a higher concentration of methoxyphenols than in the particulate fraction. The most abundant compounds in our samples were vanillic acid, vanillin, acetovanillone and p-coumaric acid. [1] Zennaro, P., et al., Fire in ice: two millennia of boreal forest fire history from the Greenland NEEM ice core. Climate of the Past, 2014. 10(5): p. 1905-1924. [2] Zangrando, R., et al., Levoglucosan and phenols in Antarctic marine, coastal and plateau aerosols. Science of The Total Environment, 2016. 544: p. 606-616. [3] Zangrando, R., et al., Molecular markers of biomass burning in arctic aerosols. Environ Sci Technol, 2013. 47(15): p. 8565-74

A new method for the determination of primary and secondary terrestrial and marine biomarkers in ice cores using liquid chromatography high-resolution mass spectrometry.

The majority of atmospheric compounds measured in ice cores are inorganic, while analysis of their organic counterparts is a less well developed field. In recent years, understanding of formation, transport pathways and preservation of these compounds in ice and snow has improved, showing great potential for their use as biomarkers in ice cores. This study presents an optimised analytical technique for quantification of terrestrial and marine biosphere emissions of secondary organic aerosol (SOA) components and fatty acids in ice using HPLC-MS analysis. Concentrations of organic compounds in snow and ice are extremely low (typically ppb or ppt levels) and thus pre-concentration is required prior to analysis. Stir bar sorptive extraction (SBSE) showed potential for fatty acid compounds, but failed to recover SOA compounds. Solid phase extraction (SPE) recovered compounds across both organic groups but methods improving some recoveries came at the expense of others, and background contamination of fatty acids was high. Rotary evaporation was by far the best performing method across both SOA and fatty acid compounds, with average recoveries of 80%. The optimised preconcentration - HPLC-MS method achieved repeatability of 9% averaged for all compounds. In environmental samples, both concentrations and seasonal trends were observed to be reproducible when analysed in two different laboratories using the same method.Work by Amy King was jointly supported by Selwyn College, Cambridge, and the NERC Doctoral Training Programme [grant number NE/L002507/1]. Work by Chiara Giorio was supported by the ‘BAS-UCAM Innovation Centre Feasibility Studies’ programme 2013-2015 [project ‘Organics in Ice’] and by the ERC Consolidator Grant 279405 “COrANE”. Eric Wolff was supported by a Royal Society Professorship

Free amino acids in the Arctic snow and ice core samples: Potential markers for paleoclimatic studies

The role of oceanic primary production on climate variability has long been debated. Defining changes in past oceanic primary production can help understanding of the important role that marine algae have in climate variability. In ice core research methanesulfonic acid is the chemical marker commonly used for assessing changes in past primary production. However, other organic compounds such as amino acids, can be produced and emitted into the atmosphere during a phytoplankton bloom. These species can be transported and deposited onto the ice cap in polar regions. Here we investigate the correlation between the concentration of chlorophyll-a, marker of marine primary production, and amino acids present in an ice core. For the first time, free l- and d-amino acids in Arctic snow and firn samples were determined by a sensitive and selective analytical method based on liquid chromatography coupled with tandem mass spectrometry. The new method for the determination of free amino acids concentrations was applied to firn core samples collected on April 2015 from the summit of the Holtedahlfonna glacier, Svalbard (N 79'08.424, E 13'23.639, 1120m a.s.l.). The main results of this work are summarized as follows: (1) glycine, alanine and proline, were detected and quantified in the firn core samples; (2) their concentration profiles, compared with that of the stable isotope δ(18)O ratio, show a seasonal cycling with the highest concentrations during the spring and summer time; (3) back-trajectories and Greenland Sea chlorophyll-a concentrations obtained by satellite measurements were compared with the amino acids profile obtained from ice core samples, this provided further insights into the present results. This study suggests that the amino acid concentrations in the ice samples collected from the Holtedahlfonna glaciers could reflect changes in oceanic phytoplankton abundance