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Introduction

The study of atmospheric depositions in the surroundings of Porto Marghera industrial area is an air quality monitoring project that involves the City of Venice, the Province of Venice, the National Research Council, the Regional Agency for the Protection of the Environment (ARPAV) and two energy production companies (ENEL Production and EDISON Thermoelectric) that manage some thermoelectric plants in this site.

The aim is to evaluate the level of pollution due to atmospheric transport of some polluting substances, to add information to the bio-monitoring network controlled by ENEL and EDISON and to integrate data produced by ARPAV via the conventional monitoring stations for atmospheric pollution.

Relevance of depositions studies

Atmospheric deposition of aerosol and gas happens in two ways: wet and dry. Dry deposition of particles happens for their direct impact and gravitational sedimentation on ground or water, while wet deposition comprises water, its dissolved gas, and any other insoluble particle material. In order to calculate the total atmospheric loading it is necessary to measure wet and dry depositions.

The importance of depositions changes from zone to zone and from element to element. In general wet deposition is more important than dry for the elements associated to smaller particles. Trace elements like heavy metals, at least the ones related to high temperature combustion particles, present themselves in the shape of fine particles. The sum of wet and dry depositions is called bulk deposition.

Characteristics and results of the study in Venetian area

For the project’s aims a network of 6 devices for bulk depositions sampling has been located inside and outside Porto Marghera industrial area, trying to couple them with automatic analyzers, with the availability of previous monitoring data or biomonitoring first year results.

Figure 1 - Devices for bulk depositions sampling.

Figure 2 – Air quality monitoring networks in the Venetian territory. Green spots: biomonitoring stations; red spots: systems for bulk sampling; yellow spots: conventional monitoring stations (managed by the Porto Marghera Industrial Corporation, Ente Zona Industriale - EZI); light blue spots: conventional monitoring stations (managed by ARPAV).

Meteorological conditions have been studied through the data (on rain, wind speed and direction) collected at Porto Marghera Industrial Corporation monitoring stations. The amount of rain fallen during the bulk deposition sampling gives information on pollutants quantity that have been washed out by the atmosphere, while wind speed and direction can help finding air pollution sources and following pollutants dispersion. The prevalent wind direction is North - North East, in accordance with the typical local wind rose.

Resulting information are the average daily amounts of atmospheric deposition for each pollutant. Also different trends for every sampling site can be seen, even though a huge variability between different samples has been observed.

The most important elevated depositions have been registered in correspondence of EZI (inside the industrial area) and Malcontenta (downwind the industrial emissions) stations, for almost all the inorganic pollutants. Elevated depositions also of some elements at the Ca’ Emiliani station.

It can be said , in general, that stations have deposition amounts in the following order: Malcontenta > Ente Zona Industriale > Dogaletto > Ca’ Emiliani > Antonio Da Mestre = Chirignago (see Figure 2).

Malcontenta and Dogaletto stations (they are downwind the industrial zone and Mestre urban area) show more problematical air quality conditions than the urban ones. Urban stations like Antonio Da Mestre and Chirignago show similar atmospheric depositions, even though they represent different exposure conditions within Mestre urban area. This is a further evidence of urban ubiquitous distribution of pollution derived from road traffic emissions.

Organic pollutants average values showed, for the first period, higher atmospheric flows at EZI station (in terms of PAH, PCB and PCDD/PCDF) and at Dogaletto station (in terms of HCB).

Last Updated

13th January 2005