Abstract
The presence of fine and ultrafine metal particles has been evidenced in size segregated airborne carbonaceous aerosols collected at one industrial and two background (urban and rural) sites during an extended field campaign in Central Italy. Analysis of the backscattered electrons (BSE) by SEM - EDX demonstrated an effective potential in evidencing main structural features of the metal content in identified carbon aerosols. Many observed ultrafine metal particles appear embedded in the skeleton of carbonaceous individual particles and aggregates in the coarse fraction, while the same is not evident in the case of mixed carbon-sulphates aerosol that has been detected in the submicron size. These carbon-sulphates formations include indeed nano-sized metal particles that appear physically combined but not embedded. Also, larger metal particles (ranging around 1 µm physical size) were observed close to carbon materials, but not included in their structure. Main compositional differences of metal particles with size segregation could be evidenced by energy - dispersive X ray spectrometry (EDX). Larger particles are mainly rich in Fe, frequently in presence of Mn, Cu, Cr and Zn in variable proportions; either oxidized or elemental metals were detected. On the other hand, ultrafine particles associated with carbon-sulphates aerosol are enriched in Pb and Zn, although the presence of other trace elements not detectable by SEM - EDX technique cannot be excluded. Moreover, Ce-enriched ultrafine particles were clearly determined in cenospheres. Conversely, inclusion of fine and ultrafine metal particles was rarely or not observed in soot aggregates.
Highlights
Understanding trace metal levels in the atmosphere is critical in gaining knowledge of their global geochemical cycling and of their environmental and health impacts (Witt et al 2010)
The use of backscatter analysis evidences the presence of metal particles included in each type of carbonaceous aerosol; these particles are not evidenced by the respective secondary electron (SE) acquisition
Cenospheres and Si-rich carbonate particles are mostly observed in the >1μm (a.d.) fraction, while mixed carbon-sulphates aerosol are mainly distributed in the finer fractions and are hardly distinguishable as single particles or aggregates, suggesting that they could be likely contributed by organics
Summary
Understanding trace metal levels in the atmosphere is critical in gaining knowledge of their global geochemical cycling and of their environmental and health impacts (Witt et al 2010). Metal-containing particles are strongly implicated in noxious health effects of airborne PM (Moffet et al 2008), depending on metal solubility and changing of oxidation state in biological fluids. Their physiological availability relies on the chances of these particles of entering lungs as individual entities or as carried by other particles. The latter electron microscopy technique has been adopted to put on evidence main structural features of the linkage between metal particles and different types of carbonaceous particles collected at receptor sites
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
