Source emission studies and biomass burning assessments in Venice Lagoon area

Venice is located at the northern end of the Adriatic sea at the north-eastern most part of the Po river plain, and from the climatic point of view it is characterised by atmospheric stability and thermal inversion inducing cold masses at the ground level during the winter time. Humidity is high causing foggy events in winter and intermediate seasons, with low pollutants dispersion. Temperature increase is coupled with an increase of the Planetary Boundary Layer, consequently both pollutants mixing and dispersion increase in summer time. From the chemical point of view, sources of particulate matter (PM) in Venice have been identified by different studies (Stortini et al, 2009; Rossini et al., 2010; Masiol et al., 2010). For heavy metals in PM10 the thermoelectric power plant and the glass factories are considered the most important emission sources. Data from the national environmental agency (ARPAV, 2006) for ships in the two principal berthing areas of Venice has shown that 69% of the emissions come from the petrochemical industry deliveries, while the 31% from the tourism and local activities. Venice area and its hinterland are characterised by industrial and agricultural activities, and urban agglomerates together with rural background areas are widely represented there. This scenario lets account a number of different sources and the use of further chemical methods is necessary for their identification. A preliminary study was performed on particulate matter samples (PM10 and PM2.5) randomly collected in 2007 and 2008, and trace elements, ions and Levoglucosan have been measured. The aim of this study is to verify how biomass burning is recognizable, and how well could be identifiable in emission sources studies, taking into account the complexity above described for the area here considered. Trace elements were measured by Inductively Coupled Plasma-Quadrupole Mass Spectrometry (ICPQMS Agilent 7500I). Elements concentrations in samples have been obtained after subtraction of their field blank values. Details about sample treatment and accuracy are reported elsewhere (Stortini et al., 2009). Ions where measure by an ionic cromatograph Metrohm 761 Compact IC, with a Metrosep A Supp 4 - 250 column for the anionic analysis, and nitrates, nitrites, chlorides, sulphates and oxalates were measured (Bonetto, 2009). Their measurement represent an useful tools for the assessment of secondary aerosol. Levoglucosan (1,6-anhydro-?-D-glucopyranose) was measured for aerosol samples (Zangrando, 2007), and this is a product of cellulose combustion, that take place when cellulose is heated to over 300°C causing by various pyrolytic processes that cause the Levoglucosan production in large quantities. This chemical marker is useful as molecular tracer for biomass burning in the atmosphere because Levoglucosan it cannot be generated by noncombustive processes or by nonwood combustion. Sample analysis was performed by using liquid chromatography/negative ion electrospray ionization tandem mass spectrometry (HPLC/(-)ESI-MS/MS). An Agilent 1100 series HPLC system (Agilent, Waldbronn, Germany) coupled to an API 4000 triple quadrupole mass spectrometer (Applied Biosystems/MDS SCIEX, Toronto, Ontario, Canada) were used to determine Levoglucosan. First results evidenced a seasonal trend in terms of PM concentration and in terms of measured analytics. PCA and PMF statistic tools are applied on all the parameters considered in this preliminary study evidenced the complexity of the studied area.