1,721,092 research outputs found
Profili di emissione “real world” per la valutazione del contributo della combustione della legna al PM
No full textStudi di letteratura hanno mostrato come la combustione della legna per il riscaldamento domestico sia un’importante sorgente di particolato atmosferico durante l’inverno. La stima del contributo della combustione di legna al PM è spesso effettuata mediante metodi di source apportionment che, in alcuni casi, richiedono la conoscenza dei profili di emissione della sorgente come dato di input al modello. Allo stato dell’arte, la stima dei profili di emissione alla sorgente è un problema ancora molto dibattuto. Per quanto riguarda le emissioni dagli impianti di combustione della legna fattori quali la tipologia di legno, la pezzatura (ciocchi, pellets, cippato), l’efficienza di combustione e le condizioni di utilizzo sono tra i fattori che causano le maggiori incertezze. In questo lavoro viene presentata una metodologia che permette di ricavare fattori di emissione rappresentativi della sorgente “combustione della legna” a partire dai risultati dell’analisi Positive Matrix Factorization (PMF) piuttosto che dalle misure alla sorgente. In particolare, i profili chimici dei fattori identificati con l’analisi PMF sono stati la base di partenza per la stima di rapporti real world fra le componenti chimiche caratteristiche della sorgente [1, 2].
I profili real world così ottenuti sono stati confrontati con i profili di letteratura generalmente utilizzati per la stima del contributo della combustione della legna al PM [1]. I risultati dello studio hanno mostrato come i fattori di emissione ottenuti con PMF possono meglio rappresentare la situazione reale poiché tengono in conto eventuali effetti dovuti a riprocessamento della massa
d’aria nel suo percorso dalla sorgente al recettore.
L’utilizzo di fattori di emissione real world - ottenuti in un dato sito grazie a studi pregressi - presenta forti potenzialità applicative nello sviluppo di approcci modellistici attualmente basati su fattori di emissione affetti da forti incertezze e grande variabilità.
Bibliografia
[1] A. Piazzalunga et al., Atmos. Environ.. 6642-6649, 45 (2011).
[2] V. Bernardoni et al., Sci. Total Environ., 4788–4795, 409 (2011)
Caratterizzazione del particolato urbano milanese: risultati preliminari relativi alla frazione carboniosa ed alla distribuzione dimensionale di alcuni metalli
No full textDevelopment of analytical techniques for the characterization of natural and anthropogenic compounds in fine particulate matter
No full textDevelopment of analytical techniques for the characterization of natural and anthropogenic compounds in fine particulate matter. In particular analysis of the carbonaceous fraction for the emission sources identification. Employment of TOT analysis and set-up and validation of new analytica procedures
DAMAGE EVALUATION ON STONE MATERIALS OF THE RICHINI COURTYARD (MILAN, ITALY)
No full textIt has been recognized that air pollutants interact with carbonate surfaces and cause major damage to architectural heritage. The focus of the present study is to evaluate the damage on the stone materials that have been used for the realization of Richini courtyard. The courtyard was designed in the seventeenth century by Francesco Maria Richini in the complex of Ca 'Granda Hospital, currently home to the University of Milan. Since 1990 has been the subject of an important conservative intervention. At a distance of twenty years after the restoration, "Richini Project" aims to make an assessment of the effectiveness and durability of the solutions used. This study lies in the framework of this project.
At this purpose the quantification of soluble salts within the stone samples, collected on the four sides of the courtyard, has been performed by ion chromatography. A widespread sulfatation phenomenon has been put in evidence with differences in intensity among the sides because of different exposition to the atmospheric agents. Atmospheric particulate matter (PM) present on the stone surfaces has been examined. In fact PM is involved in the formation of the black crusts that sometimes cover the surfaces. A new methodology has been set up for the quantification of organic carbon (OC) and elemental carbon (EC), which are mainly responsible of the blackening of those areas. PM major inorganic constituents (cations and anions) have been also quantified and observations by SEM-EDX have allowed the identification of metals that may act as catalysts in the reactions of degradation
Methodology to determine carbonate carbon from Thermal Optical Transmittance measurements
No full textCarbonate carbon (CC) is often not considered in atmospheric aerosol chemistry studies which comprise the measurement of elemental carbon (EC) and organic carbon (OC). The reason for this may be its low contribution to fine particle mass in most area along with the difficulties in its analytical determination in atmospheric aerosol collected on filter matrices. Carbonate particles are expected to significantly contribute to the Mediterranean PM mainly during the intrusion of air masses from North Africa. However, the CC fraction in particulate matter may not be negligible if high concentrations of mineral dust, either natural (natural erosion, sand storms) or originating from street abrasion or construction sites are present. Some thermal–optical methods have recently been used to determine carbonate carbon, along with different organic fractions and EC and it has been shown that the interference of CC with the signal of EC or OC may lead to overestimations of either of these two carbon fractions during thermal-optical analysis (Karanasiou et al., 2010). The use of a sample pretreatment with HCl fumes to eliminate CC prior to the thermal analysis is suggested to avoid the interference by carbonate particles. We have used the sample pretreatment to identify the CC contribution to the flame ionization detector (FID) signal from TOT measurements and implement a numerical procedure to determine CC, EC, and OC levels. The time evolution analysis of the FID signal before and after the treatment with HCl fumes of TSP and PM2.5 samples, has revealed that the CC peak may occurs within the 220-250 s time interval and that it is characterized by a full-with-at-half-maximum (FWHM) deltat* = 25±3 s, in accordance with previous studies. We have assumed that the CC volatilization contributes to the FID signal with a pulse which can be fitted by a Gaussian function with the peak at the time ti (within the 220-250 s time interval) and the FWHM width deltati = 25±3 s, to determine CC levels. In particular, we have calculated the Gaussian function area ascribed to the CC volatilization and the area of the calibration signal, to quantify CC levels in the analyzed PM samples. This calculation has been carried out through a fitting procedure, in which the FID signal is represented as a weighted sum of Gaussian functions, S(t), through an algorithm implemented by ourselves in Matlab®. In fact, we have assumed that S(t) can be represented by a linear combination of Gaussia functions, where ai, ti and sigmai represent amplitude, peak-time and standard deviation of the Gaussian function i and N represents the total number of Gaussian functions. The FID signal has at first been interpolated with cubic splines to obtain a straightforward calculation of its first and second derivatives. Then, through the analysis of the second derivative minima we have automatically identified the number N of Gaussian functions composing S(t). A FWHM deltati = 25±3 s has been imposed to the Gaussian function ascribed to CC, in accordance with experimental results. We have assumed that CC level uncertainties are mainly due to the uncertainties of the parameters defining the Gaussian function fitting the CC volatilization signal. The implemented technique has been tested by determining CC, OC, and EC levels in 26 TSP and PM2.5 samples which have simultaneously collected over south-eastern Italy, in the Central Mediterranean. We have found that uncertainties on CC levels vary from 0.1% up to 9% and from 0.2% up to 20% in TSP and PM2.5 samples, respectively. It has also been shown that OC levels may be quite overestimated mainly in the coarse fraction, if the CC contribution is not accounted for. Figure 1 shows as an example Ca2+ and CO32- levels (calculated from CC concentrations) in the 26 analyzed TSP samples. The good correlation between Ca2+ and CO32- levels support the reliability of the implemented technique: carbonate-containing mineral dust is often associated with calcium. The anion deficit defined as an excess of positive charge, which is often found in Mediterranean PM samples, has been used in some Mediterranean studies to infer and estimate carbonate mass concentrations
Valutazione del degrado delle superfici lapidee attraverso l’analisi dei sali solubili e la caratterizzazione chimica delle polveri depositate
No full textDeterminazione di BC su filtri in PTFE e fibra di quarzo : risultati di 2 esperimenti a Milano
No full textIl Black Carbon (BC) può essere misurato attraverso metodi basati sull’assorbimento della luce, ma al momento non esistono metodologie di riferimento o chiare definizioni di BC [1]. In questa presentazione mostreremo risultati ottenuti mediante un fotometro polare appositamente realizzato e messo a punto per la misura dell’assorbimento di una luce laser da parte di particelle di BC raccolte su filtri in PTFE e fibra di quarzo. Sono stati eseguiti due esperimenti a Milano nel 2009/2010 e 2011. In entrambi i casi i campionamenti svolti sono stati eseguiti in parallelo su filtri in PTFE e fibra di quarzo in un periodo estivo e in uno invernale. Tutti i filtri sono stati analizzati mediante fotometro polare. I filtri in fibra di quarzo sono stati anche analizzati con metodo termo-ottico a trasmissione (TOT) utilizzando diversi protocolli (NIOSH, EUSAAR_2, IMPROVE-like). Durante i campionamenti era inoltre operativo un Multi Angle Absorption Photometer (MAAP).
Il primo esperimento ha avuto lo scopo di validare il set-up. Si è verificato che i valori di coefficiente di assorbimento dell’aerosol (babs in Mm-1) ottenuti con un MAAP erano perfettamente confrontabili (entro il 5%) con quelli ottenuti dal set-up messo a punto utilizzando filtri in fibra di quarzo. Al contrario, i valori di babs ottenuti utilizzando il medesimo set-up e schema di trasferimento radiativo con filtri in PTFE sono risultati molto inferiori (circa un fattore 2). Un comportamento simile è stato verificato su filtri in fibra di quarzo dopo rimozione dei composti solubili in acqua. Il secondo esperimento aveva l’obiettivo di studiare il potenziale ruolo di composti organici volatili nelle differenze osservate tra i campioni raccolti su filtri in PTFE e in
fibra di quarzo. In questo caso, il campionatore utilizzato per i filtri in quarzo era dotato di un denuder a carbone attivo per la rimozione dei gas organici. I risultati ottenuti con il fotometro polare hanno mostrato un buon accordo tra i babs misurati utilizzando i due supporti, dimostrando che l’utilizzo di un denuder su un sistema di raccolta su filtri in fibra di quarzo può dare un valore di babs più accurato e, perciò, una miglior stima del BC. Un parametro cruciale per la determinazione del BC mediante assorbimento della luce è la valutazione del coefficiente di assorbimento (sabs,BC in m2 g-1) che può variare nel range 2-25 m2/g in funzione della distribuzione dimensionale e dell’indice di rifrazione [1] e può essere influenzato dallo stato di mixing delle particelle [2]. sabs,BC è solitamente determinato da misure di EC mediante tecniche TOT/TOR, che non sono ancora standardizzate. Nei nostri campioni, sono stati trovati valori di sabs,BC nel range 6.3-16 m2/g in funzione di diversi trattamenti del filtro in quarzo non trattato, lavato, denuded) e del protocollo utilizzato .
Bibliografia
[1] T.C. Bond and R.W. Bergstrom, Aerosol Sci. Technol. 27-67, 40 (2006)
[2] H. Naoe, et al., Atmos. Environ. 1296-1301, 43 (2009
Set-up of extraction procedures for ions quantification in aerosol samples
No full textIons quantification in aerosol samples is commonly achieved by means of Ion Chromatography (IC) after extraction of the analytes from the filter generally using MQ water and operating in an ultra-sound bath. Although this sample preparation system is widely employed in the literature, some important aspects such as ions recovery percentages after the extraction are often not taken into consideration.
The aim of this work was to focus on the optimization of the extraction method for different types of filter supports (i.e. PTFE and quartz-fibre filters), which are commonly used for aerosol sampling.
For SO4=, NO3- and NH4+ the best recoveries, after a single extraction step, were achieved with PTFE while chlorides recovery was quite low and not reproducible. When quartz is employed and a single extraction step used, in order to give a correct quantification of ions concentration it is generally necessary to apply a correction factor but for chloride quantification three subsequent steps are mandatory.
Both techniques and extraction procedure uncertainties have been evaluated and resulted to be within 10%. Limit of detection (LOD) for all the analysed species were determined and it was found that they were within the ranges reported in the literature
Wood combustion contribution to PM: results of five years campaign (2005-2009) in Lombardy (Italy)
No full textIn this work, a methodology based on the macro-tracer approach was improved to obtain a more reliable estimate of the wood burning impact on PM and OC concentrations. Indeed, emission factors taken from the literature but tailored to the wood consumption data available for the investigated region were used for the calculation.
Moreover, an alternative approach was introduced using the Positive Matrix Factorization (PMF) source profile to derive real-world emission ratios in ambient air. In this work – at our knowledge for the first time - these data have been used in the macro-tracer approach to obtain more reliable estimates of the wood burning impact on atmospheric aerosol.
A critical comparison of these methods with average wood smoke emission factors reported in the literature was carried out. These results indicate that PMF-derived emission ratios can be a feasible alternative to the most traditional approach with wood smoke emission factors measured at the source, which show a high variability.
The proposed methodology was applied to a trial dataset of wintertime PM10 samples - characterised for anhydrosugars, organic, and elemental carbon contents – collected in the frame of a regional project. The results gave a preliminary estimate of the wood smoke contribution to PM10 and the organic fraction in different sites in Lombardy (Northern Italy)
A multi-analytical approach for the study of the pigments used in the wall paintings from a building complex on the Caelian Hill (Rome)
No full textIn the present study, shards from Roman wall paintings (from the end of the first century to the fourth century A.D.) decorating the domus below the Basilica of SS. John and Paul on the Caelian Hill (Rome), were analyzed in order to identify the pigments used. The analytical techniques employed for the characterization of the pigments were the scanning electron microscope coupled with an energy dispersive spectrometer (SEM-EDS) and infrared spectroscopy (ATR and micro ATR). While SEM-EDS allowed to perform a qualitative analysis of the material, by FT-IR chemical species have been identified. The pigments identified were those mentioned in the literature for the Imperial Roman fresco painting: different types of ochre (yellow and red), mixtures containing lead, green earths and precious pigments such as cinnabar and Egyptian blue. They were often used as mixtures and the use of the most valuable
pigments (cinnabar and Egyptian blue) were found in the most ancient rooms
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