Browsing by Author "Bertolini, Roberto"

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<> modelling study of atmospheric cycle of mercury and its exchange processes at environmental interfaces
(2015-12-18) De Simone, Francesco; Bertolini, Roberto; Carbone, Vincenzo; Pirrone, Nicola; HedgecocK, Ian M.
Since ancient times human activities have significantly altered the natural global Mercury (Hg) cycle through emissions to the environment. Hg is a global pollutant since its predominant atmospheric form, elemental Hg, reacts relatively slowly with the more abundant atmospheric oxidants and is therefore transported long distances from its emission source. Once oxidised however Hg is readily deposited, an can then be converted to the toxic monomethylmercury (MeHg) in soils and natural waters. MeHg is able to bioaccumulate and biomagnify, up to levels at which it is harmful to human health. Mercury pollution is therefore a threat to ecosystem health on a global scale, and is now being addressed by an international agreement, the Minamata Convention. Comprehensive knowledge of the details of the atmospheric Hg cycle is still lacking, and in particular there is some uncertainty regarding the atmospherically relevant reduction-oxidation reactions of mercury and its compounds. The exchange of Hg and its compounds between the atmosphere and the oceans also plays an important role in the cycling of mercury in the environment: understanding and quantifying mercury deposition patterns and fluxes is critically important for the assessment of the present, and future, environmental impact of mercury contamination. ECHMERIT is a global on-line chemical transport model, based on the ECHAM5 global circulation model, with a highly customisable chemistry mechanism designed to facilitate the investigation of both aqueous and gas phase atmospheric mercury chemistry. An improved version of the model which includes a new set of emissions routines, both on-line and off-line, has been developed and used for this thesis to investigate and assess a number of the uncertainties related to the Hg atmospheric cycle. Outputs of multi-year model simulations have been used to validate the model and to estimate emissions from oceans. Various redox mechanisms have been included to assess how chemical reactions influence the models ability to reproduce measured Hg concentrations and deposition flux patterns. To characterize the Hg emissions which result from Biomass Burning , three recent biomass burning inventories (FINNv1.0, GFEDv3.1 and GFASv1.0) were included in the model and used to investigate the annual variation of Hg. The differences in the geographical distribution and magnitude of the resulting Hg deposition fluxes, hence the uncertainty associated with this Hg source, were quantified. The roles of the Hg/CO enhancement ratio, the emission plume injection height, the Hg0 (g) oxidation mechanism and lifetime, and the inventory chosen, as well as their uncertainty were considered. The greatest uncertainties in the total deposition of Hg due to fires were found to be associated with the Hg/CO enhancement ratio and the emission inventory employed. Deposition flux distributions proved to be more sensitive to the emission inventory and the oxidation mechanism chosen, than all the other model parameters. Over 75% of Hg emitted from biomass burning is deposited to the world’s oceans, with the highest fluxes predicted in the North Atlantic and the highest total deposition in the North Pacific. The net effect of biomass burning is to liberate Hg from lower latitudes and disperse it towards higher latitudes where it is eventually deposited. Finally, the model was used to evaluate the fate of the Hg released into the atmosphere by human activities. Anthropogenic emissions are estimated to amount to roughly 2000Mg/y (1000-4000 Mg/y). Hg speciation (elemental, oxidised or associated with particulate matter) is subject to many uncertainties: the extremely variable lifetimes among Hg species, as well as the Hg emission heights, in combination with the complex physical and chemical mechanisms that drive its final fall-out lead to considerable uncertainties. To address this specific issue three anthropogenic Hg emission inventories, namely AMAP-UNEP, EDGAR and Streets, were included in the Model. Different model parametrisations were adopted to trace the fate of Hg to its final receptors and to thoroughly test the model performance against the measurements. Primary anthropogenic Hg contributes up to 40% of the present day Hg deposition. The oxidation mechanism has a significant impact on the geographical distribution of the deposition of Hg emitted from human activities globally, : 63% is deposited to the world’s oceans. The results presented in this thesis provide a new and unique picture of the global cycle of mercury, evaluating and assessing the uncertainties related to many aspects with an on-line Global Circulation Model developed specifically to investigate the global atmospheric Hg cycle.
Air quality and pollutant modelling in the mediterranean regionDocumenti elettronici
(2013-11-11) Gengarelli, Christian Natale; Bertolini, Roberto; Pirrone, Nicola; Carbone, Vincenzo; Hedgecock, Michael
L'inquinamento atmosferico viene de nito come la presenza di sostanze che possono avere e etti dannosi sulla salute umana o sull'intero sistema ambientale (EC, 2008), causando e etti misurabili sugli animali, sulla vegetazione e sui diversi materiali. Queste sostanze, dette inquinanti, usualmente non sono presenti nella normale composizione atmosferica o lo sono ma a concentrazioni estremamente basse. Tra i pi u pericolosi inquinanti presenti in atmosfera c' e il mercurio (Hg), un inquinante globale sotto controllo soprattutto negli ultimi anni (UNEP, 2013b; Mason et al., 2012; Driscoll et al., 2013) in quanto provoca gravi e etti nocivi sulla salute umana. Elevate concentrazioni di mercurio negli ecosistemi sono causate dalle emissioni dirette, ma anche da reazioni chimiche che avvengono in atmosfera e dalle condizioni meteorologiche che, governate dalla sica dell'atmosfera, regolano la distribuzione, il trasporto e la deposizione del mercurio. Per individuare le cause delle elevate concentrazioni di inquinanti in atmosfera e necessaria un adeguata rete di monitoraggio, ma e molto complicato coprire vaste aree geogra che con stazioni di misura. Diviene dunque necessario ricorrere a modelli matematici che simulano le condizioni atmosferiche dal punto di vista sia meteorologico che chimico, in modo da ottenere i fattori sui quali e possibile intervenire per migliorare la qualit a dell'aria. Questo lavoro di tesi mostra lo sviluppo di un modello regionale online che simula il ciclo atmosferico del mercurio, in modo da valutare ed identi care le relazioni tra sorgenti e recettori a scala regionale e gli andamenti temporali degli scenari di emissione di mercurio attuali e futuri. Il risultato e una versione ampliata del modello numerico per la chimica ed il trasporto atmosferico WRF/Chem (modello Weather Research and Forecasting per la meteorologia integrato con la chimica atmosferica, Grell et al. (2005)), che pu o simulare il ciclo atmosferico del mercurio online. Questa versione del modello e in grado di riprodurre i campi di concentrazione ed i ussi di deposizione del mercurio a scala regionale, includendo le emissioni da sorgenti sia antropogeniche che naturali e simulando le interazioni e le reazioni chimiche che avvengono in atmosfera, nonch e i processi di deposizione. Per lo sviluppo di questo modello e stato necessario indagare i diversi aspetti della chimica del mercurio, analizzando ed implementando le interazioni con gli altri gas presenti in atmosfera, con la radiazione solare, con il vapore acqueo e con la pioggia; queste interazioni regolano i processi di ossidazione, riduzione e deposizione del mercurio. Inoltre sono stati implementati nel modello i processi di emissione da parte di sorgenti antropiche e naturali, parametrizzando le emissioni di mercurio dovute agli incendi boschivi e l'evasione di mercurio nell'interfaccia atmosfera - super ce del mare. Oltre alle deposizioni di mercurio da parte delle piogge (deposizione wet) sono stati implementati i meccanismi per deposizione al suolo dovuta alla forza gravitazionale ed ai moti atmosferici (deposizione dry). Il modello e in grado di riprodurre la variazione stagionale delle concentrazioni di mercurio, rappresentando adeguatamente anche gli andamenti di HgII e HgP nello strato atmosferico al limite con la super ce del Mar Mediterraneo (Mediterranean MBL). La medie annuali delle deposizioni di mercurio wet e dry modellate sono simili, ma con di erente distribuzione spaziale: la deposizione wet domina nelle zone umide mentre la deposizione dry e maggiore vicino alle sorgenti di emissione. Comparando le deposizioni con l'evasione di mercurio dalla super ce del mare risulta che il Mar Mediterraneo e una sorgente di mercurio per tutta l'area, con circa 70Mg di mercurio emessi in un anno. I risultati suggeriscono inoltre che nel MBL Mediterraneo il Bromo e un importante ossidante del mercurio. Il modello WRF/Chem e stato inizialmente usato per investigare la produzione fotochimica di un importante costituente atmosferico che in uenza il ciclo del mercurio nell'area del Mar Mediterraneo, l'ozono troposferico (O3). Oltre ad in uenzare il ciclo del mercurio, l'ozono e anche un pericoloso inquinante: elevate concentrazioni di ozono in prossimit a del suolo sono infatti dannose sia per la salute umana che per la produzione agricola. L'analisi modellistica dell'inquinamento da ozono troposferico mostra una forte in- uenza delle emissioni prodotte dalle navi che transitano nel Mar Mediterraneo, stimando il loro contributo in circa il 10{20% delle concentrazioni di ozono nelle aree continentali.
Dielectric characterization of different mesogenic substances and a mixture with non-conventional gold nanoparticles
(2012-11-28) Marino, Lucia; Versace, Carlo; Bertolini, Roberto; Scaramuzza, Nicola
The study of liquid-crystalline matter and nano-structured materials is an important and vast field of research with potential implications in the development of new technologies, like sensors and displays. In this work we have analyzed and characterized different systems by dielectric spectroscopy. The first part of this thesis is devoted to the characterization of an orthoconic liquid-crystalline mixture, W-129, with ferroelectric properties. The analysis of the dielectric response of this material has revealed a plurality of ferroelectric smectic C* subphases; they represent smectic intermediate variants situated between the ferroelectric phase and the antiferroelettric one, known like antiferrielectric phases (SmCFI*, SmCFII*, ... ), whose study is still open and is collecting a lot of interest in academic environments. The same liquid crystalline mixture was then doped with unconventional gold nanoparticles. These nanoparticles are functionalized with a hydrophilic polymer which becomes hydrophobic exceeded 40°C. The nano-composite material obtained by the dispersion of the gold nanoparticles presents interesting characteristics, such as an enhancement of dielectric increments (or strengths) probably due to the molecular interactions between the ferroelectric liquid crystal and the gold nanoparticles, which translates into an increase of the order of the liquid crystal host, in a stabilization of the smectic subphases and in an enhanced memory effect already seen in the pure liquid-crystalline mixture. The third and last part is devoted to the characterization of a new "banana-shaped" liquid crystal, which exhibits some unusual physical properties during the nematic phase, in particular, the presence of regions of more ordered molecules, organized in a smectic C phase inside a nematic one. The dielectric spectra acquired during the nematic phase show the presence of a relaxation response between 10 and 20 Hz which, with the addition of relatively large values of permittivity, may suggest the presence of a ferroelectric response due to the existence of cybotactic clusters.
Dynamics and evolution of solar corona: STEREO observations of jets, CMEs and numerical modeling
(2011-11-03) Nisticò, Giuseppe; Carbone, Vincenzo; Bertolini, Roberto; Zimbardo, Gaetano
A Lévy Walk approach to the propagation of solar energetic particles
(2013-11-26) Trotta, Enrico Maria; Bertolini, Roberto; Zimbardo, Gaetano
This thesis is dedicated to the problem of energetic particle propagation in the solar wind, with special emphasis on the propagation of solar energetic particles (SEPs). Those particles are accelerated either in the low corona by flares, usually giving rise to so-called impulsive SEP events, or in the higher corona by the shock driven by coronal mass ejections, giving rise to the so-called gradual SEP events. In either case, energetic particles propagate in the solar wind along the spiral magnetic field, and then reach the Earth’s environment, where they can intensify the auroral emission and downgrade or even damage spacecraft operations. Indeed, SEPs represent one of the major hazards of the research programme known as space weather, which aims at reducing the risks associated with the solar and space activities. The fluxes of energetic particles measured in the Earth’s environment depend both on the source strength and on the propagation properties. Traditionally, two limiting transport regimes are considered, that is, di usive transport and scatter-free, i.e., ballistic, transport. However, in the last two decades, anomalous transport regimes in which the mean square displacement grows nonlinearly with time have become more and more common. An anomalous transport regime, either subdi usive or superdi usive, would influence in a fundamental way the flux of solar energetic particles reaching the Earth. To study this problem we have developed two approaches, one based on the analysis of SEP fluxes measured by spacecraft in the solar wind, and the other on the numerical simulation of SEPs in the case of superdi usive transport. In the first approach, we considered SEPs measurements by ACE, Wind and other spacecraft for the case o mpulsive SEP events, and compared the time profile of the energetic particles with that corresponding to the di erent forms which the propagator assumes in the case of superdi usive transport. The comparison gives direct information on the transport regime, showing that electrons propagate in a superdi usive way with anomalous di usion exponent alpha running from 1.2 to 1.75. For protons, quasi-ballistic transport regimes are also found. In the second approach, the statistical mechanism giving rise to superdi usion, namely the Lévy random walk, is investigated numerically. We developed a new numerical code which simulates the Lévy walk while changing the parameters which determine the pace of transport, that is the exponent of the power law tails of the jump probability distribution. This code reproduces well the anomalous transport predictions for the mean square displacement and for the propagator of Lévy walks, while allowing a clear and simple identification of the parameters determining the transport regime. Therefore this code represents a powerful tool to compare the simulation results to spacecraft data. Comparison with the data has been considered both for impulsive and gradual SEP events. In this thesis, we show that the numerical code reproduces well the observations o mpulsive events for the various transport regimes. Additional work is required to apply the code to the propagation of gradual SEP events, as modeling of the shock source is required. While this will be implemented in the near future, the e ectivitiy of the numerical code will allow an important improvement in the understanding of SEP propagation and in the prediction of space weather perturbations
Micro raman spectroscopic investigations on soft matter systems
(2012-12-04) Fasanella, Angela; Versace, Carlo; Bertolini, Roberto; Cazzanelli, Enzo
University of Calabria