Laura Ferroni

PCDD/Fs atmospheric deposition fluxes and soil contamination close to a municipal solid waste incinerator

Bulk depositions and surface soil were collected in a suburban area, near the Adriatic Sea, in order to assess the contribution of a municipal solid waste incinerator to the areas total contamination with polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs and PCDFs). Samples were collected at two sites, situated in the area most affected by plant emissions (according to the results of the Calpuff air dispersion model), and at an external site, considered as a reference. Results show that the studied area is subject to low contamination, as far as these compounds are concerned. Deposition fluxes range from 14.3 pg m(-2)d(-1) to 89.9 pg m(-2)d(-1) (0.75 pg-TEQ m(-2)d(-1) to 3.73 pg-TEQ m(-2)d(-1)) and no significant flow differences are observed among the three monitored sites. Total soil concentration amounts to 93.8 ng kg(-1) d.w. and 1.35 ng-TEQ kg(-1)d.w, on average, and confirms a strong homogeneity in the studied area. Furthermore, from 2006 to 2009, no PCDD/Fs enrichment in the soil was noticed. Comparing the relative congener distributions in environmental samples with those found in stack emissions from the incineration plant, significant differences are observed in the PCDD:PCDF ratio and in the contribution of the most chlorinated congeners. From this study we can conclude that the incineration plant is not the main source of PCDD/Fs in the studied area, which is apparently characterized by a homogeneous and widespread contamination situation, typical of an urban area.

Bulk deposition close to a Municipal Solid Waste incinerator: One source among many

In order to assess the contribution of a Municipal Solid Waste incinerator to the areas total contamination, metals and soluble ions have been determined in bulk deposition collected at sites affected by different levels of plant emissions, according to the results of the Calpuff air dispersion model. Results show that in general fluxes monitored at the different sites during the same period are quite similar for each analyte. Deposition fluxes of nitrite and ammonium are significantly lower at the more distant site, while copper is significantly higher at this site, possibly because of copper fungicide used on the nearby agriculture land. The presence of sea spray and resuspended soil dust can be inferred from Pearson correlation coefficients, while enrichment factors indicate that Cu, Pb and Zn have a probable anthropogenic origin. A more complete evaluation of the sources affecting the area was obtained with PMF analysis. The sources associated with each factor were identified from the source profile and temporal trends. Six factors were identified, three sources associate with natural matrices, while three factors represent anthropogenic sources. The greatest contribution of heavy metals, the most toxic and persistent components determined, is associated with resuspended soil dust, especially when weighted according to their toxicity. The anthropogenic source contribution is similar at all sites, and therefore the incinerators relative contribution to the total pollutant load appears to be negligible compared to other sources affecting the area.

Source apportionment and location by selective wind sampling and Positive Matrix Factorization

In order to determine the pollution sources in a suburban area and identify the main direction of their origin, PM2.5 was collected with samplers coupled with a wind select sensor and then subjected to Positive Matrix Factorization (PMF) analysis. In each sample, soluble ions, organic carbon, elemental carbon, levoglucosan, metals, and Polycyclic Aromatic Hydrocarbons (PAHs) were determined. PMF results identified six main sources affecting the area: natural gas home appliances, motor vehicles, regional transport, biomass combustion, manufacturing activities, and secondary aerosol. The connection of factor temporal trends with other parameters (i.e., temperature, PM2.5 concentration, and photochemical processes) confirms factor attributions. PMF analysis indicated that the main source of PM2.5 in the area is secondary aerosol. This should be mainly due to regional contributions, owing to both the secondary nature of the source itself and the higher concentration registered in inland air masses. The motor vehicle emission source contribution is also important. This source likely has a prevalent local origin. The most toxic determined components, i.e., PAHs, Cd, Pb, and Ni, are mainly due to vehicular traffic. Even if this is not the main source in the study area, it is the one of greatest concern. The application of PMF analysis to PM2.5 collected with this new sampling technique made it possible to obtain more detailed results on the sources affecting the area compared to a classical PMF analysis.