366
R. Cecchi· G. Ghermandi
(Cini et al.1994) from Tyrrhenian Sea water. The approach involves the use of a multistage impactor, with size separation of the aerosol drops at the collection, and a measurement campaign performed in coastal areas near Livorno. In each experiment of
artificial aerosol production, both the sea water before aerosolization and the produced
aerosol and the sea water depleted after aerosolization were sampled. The samples were
filtered through 0.45 IJm pore size Nuclepore membranes. These filters are analysed
by PIXE (using the described set-up of INFN Lab. of Legnaro), without any further
treatement, and the element concentrations in the suspended particles have been
measured. The soluted elements have been determined in targets obtained from liquid sample pre concentration, both by metal precipitation as carbamates, and also by
a procedure of not boiling evaporation (Ghermandi et a1.1996). The preliminary results are satisfactory: Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Hg, Pb have been detected both in
sea water and in aerosol samples, with enrichment factors of 10 3 in the aerosols. The
elements detected are mainly associated to the suspended particles. It clearly demonstrates the efficiency of the aerosolization process in the concentration of pollutants,
scavenged by the surfactant organic compounds in the subsurface marine layer.
19.7
The Study of the Venice Lagoon Ecosystem by Means of the
PIXE Technique
The Venice Lagoon acts as a "reservoir" for municipal, industrial and agricultural wastes;
the quality of its water has progressively deteriorated, with resultant damage to the
ecosystem (decline in fish population, increase of eutrophication). The complicated
water dynamics into the lagoon, whose effects are pronounced in the marginal areas
of the northern basin, involve very long residence times of the pollutants.
For what concerns the inorganic pollutants, a constant monitoring and a study of
their distribution processes within the Venice Lagoon has been performed by the authors for several years by means of the PIXE technique. About one thousand environmental specimens (water, sediment, pore water) were processed for this study, with
the experimental setup performed at the INFN Laboratory of Legnaro (Padova, Italy).
19.7.1
The Fate of Pollutants Discharged into the Lagoon
The first objective was to describe and estimate the yearly discharge of fresh water
and pollutants into the Lagoon, from the drainage basin (Bernardi et al.1983; Bernardi
et a1.1985).
Among the twentyfour identified streams from which water flows out from the
drainage basin into the Lagoon, the eight most important natural and agricultural
inputs were selected. Field measurement of hydrological and physicochemical parameters (in relation with tidal forcing) and water sample collection have been performed
for some years at each of the eight channel outlets.
The investigation was limited to a group of more representative pollutant metals
(Fe, Ni, Cu, Hg, Pb), and to some nutrients (ammonia, nitrite, nitrate and total orthophosphate). The heavy metal concentrations were measured by PIXE (Cecchi et al.1983)
in not prefiltered water specimens (soluted and suspended matter); the obtained total
R. Cecchi· G. Ghermandi
(Cini et al.1994) from Tyrrhenian Sea water. The approach involves the use of a multistage impactor, with size separation of the aerosol drops at the collection, and a measurement campaign performed in coastal areas near Livorno. In each experiment of
artificial aerosol production, both the sea water before aerosolization and the produced
aerosol and the sea water depleted after aerosolization were sampled. The samples were
filtered through 0.45 IJm pore size Nuclepore membranes. These filters are analysed
by PIXE (using the described set-up of INFN Lab. of Legnaro), without any further
treatement, and the element concentrations in the suspended particles have been
measured. The soluted elements have been determined in targets obtained from liquid sample pre concentration, both by metal precipitation as carbamates, and also by
a procedure of not boiling evaporation (Ghermandi et a1.1996). The preliminary results are satisfactory: Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Hg, Pb have been detected both in
sea water and in aerosol samples, with enrichment factors of 10 3 in the aerosols. The
elements detected are mainly associated to the suspended particles. It clearly demonstrates the efficiency of the aerosolization process in the concentration of pollutants,
scavenged by the surfactant organic compounds in the subsurface marine layer.
19.7
The Study of the Venice Lagoon Ecosystem by Means of the
PIXE Technique
The Venice Lagoon acts as a "reservoir" for municipal, industrial and agricultural wastes;
the quality of its water has progressively deteriorated, with resultant damage to the
ecosystem (decline in fish population, increase of eutrophication). The complicated
water dynamics into the lagoon, whose effects are pronounced in the marginal areas
of the northern basin, involve very long residence times of the pollutants.
For what concerns the inorganic pollutants, a constant monitoring and a study of
their distribution processes within the Venice Lagoon has been performed by the authors for several years by means of the PIXE technique. About one thousand environmental specimens (water, sediment, pore water) were processed for this study, with
the experimental setup performed at the INFN Laboratory of Legnaro (Padova, Italy).
19.7.1
The Fate of Pollutants Discharged into the Lagoon
The first objective was to describe and estimate the yearly discharge of fresh water
and pollutants into the Lagoon, from the drainage basin (Bernardi et al.1983; Bernardi
et a1.1985).
Among the twentyfour identified streams from which water flows out from the
drainage basin into the Lagoon, the eight most important natural and agricultural
inputs were selected. Field measurement of hydrological and physicochemical parameters (in relation with tidal forcing) and water sample collection have been performed
for some years at each of the eight channel outlets.
The investigation was limited to a group of more representative pollutant metals
(Fe, Ni, Cu, Hg, Pb), and to some nutrients (ammonia, nitrite, nitrate and total orthophosphate). The heavy metal concentrations were measured by PIXE (Cecchi et al.1983)
in not prefiltered water specimens (soluted and suspended matter); the obtained total