Fine aerosol particles are recognized to have a strong impact on the environment and to be of concern in health-related effects. Large urban areas are strongly impacted by pollution emissions from anthropogenic sources. The proximity of harbors to dense urban populations can exacerbate the pollution level because emissions from ships and related activities in ports could be of special importance. It has been recently shown that ship emissions lead to an increase in ambient air concentrations of fine particles directly generated by the ship engines (primary particulates) or formed in the atmosphere as secondary particulates due to the combined presence of NOx, sulphur-containing species and unburned hydrocarbons. To reduce particulate formation in the atmosphere, low sulphur fuels are currently prescribed to run engines in the proximity of the harbor or during port activities in order to enhance air quality and possibly prevent large health impacts due to ship emissions.
The Naples metropolitan area represents a case study for the analysis of the different sources of pollutants, i.e., the natural marine particulate matter (PM) and that deriving from anthropogenic activities specific of the port (ships and earth activities) and from urban activities (vehicle traffic and domestic heating).
This study focuses on the measurement and characterization, in terms of size distribution and chemical composition, of the atmospheric particles sampled by a Low Pressure Electrostatic Impactor (ELPI). The particulate concentration was compared with that measured by monitoring stations of the local environmental protection agency. The aim of the study is to find out the possible sources of particles in the atmosphere of a costal urban area and to correlate the particle concentration levels with meteorological conditions, vehicle emissions and port activities.
The main results of the study are:
- The analysis of the size distributions and the chemical characteristics of the collected particles show that PM of natural origin (marine aerosol) contributes significantly to the concentration of PM detected in the harbor;
- There is a contribution of PM of anthropogenic origin in situations of high vehicular and naval traffic and under certain environmental conditions;
- PM concentrations are not significantly higher than those recorded in other areas of the city with high traffic density;
- PM concentration changes during the daytime: decreasing at nighttime and rising at peak hours of morning and evening traffic (both maritime and vehicular);
- Sulfur is present in the collected particles indicating that although a limitation to the use of sulphur-containing fuels for the ships is prescribed by the Port Authority, other terrestrial activities in the harbor area make use of sulphur-containing fuels thus contributing to the increase of the PM concentration.