Neutron activation analysis for trace elements characterization in the atmospheric pollution studies
The monitoring of trace elements (TE) content in the atmospheric particulate furnishes additional information for assessing the air quality of our cities. Many TE of anthropogenic origin may constitute a potential risk for the population not only at level of threshold concentrations but also in terms of prolonged exposure to low levels.
At the CNR Unit of Radiochemistry and Spectroscopy of the IMGC, the atmospheric particulate has been investigated to obtain the TE concentrations in the PM10 (particles with aerodynamic diameter less than 10 micron) as well in the finest "respirable" fractions involved in the different tracts of the respiratory system (alveolar 0.1- 1 micron), bronchial (1.1- 4.6 micron) and tracheo-pharynx (4.6-9 micron). The results obtained in this study illustrate the actual air quality situation for the TE content in urban (Milan), industrial, rural-residential and high altitude remote areas. The results obtained can help in characterizing the air quality of the locations investigated and provide data for a more comprehensive understanding of the extent air pollution by particulate matter. At the present (April-May, 2002) studies have been initiated to characterize the Himalayan airborne particulate collected at the CNR Pyramid Laboratory (5,050 m s.l., Khumbu Valley - Nepal, see attached photos).
The CNR Unit is also involved in studies related to the use of lichens as biomonitors of trace elements atmospheric pollution in high altitude remote areas. The project forecasts the analysis of different species of lichens collected in the regions of Himalaya, Alps and Mount Kenia. The results will be useful in assessing a data bank of the baseline values referred to areas that may be considered unpolluted and in evaluating long transport phenomena. More than 25 elements in 200 lichens were determined. A specific study for the identification of trace elements of non local origin was carried out by the calculation of their Enrichment Factors (EF). To this purpose, samples of soils, collected in the same areas of the lichens, were also analyzed. The EF have been calculated normalizing the values versus the concentration of the scandium taken as reference natural element.
The EF trends of Pb, As, Zn, Sb, Cd, and Br present the highest values in all lichens. These elements may derive not only from the local soils but also, by long distance transport phenomena, from other natural and/or anthropogenic sources. To obtain a complete data bank on the baseline values of remote areas of the world the project plans to extend the research to other high altitude sites such as Patagonia, Greenland and New Zealand.
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