The Mössbauer study of atmospheric iron-containing aerosol in the coarse and PM2.5 fractions measured in rural site.

The size-resolved iron-containing atmospheric aerosol was measured by Mössbauer spectroscopy. The particulate matter (PM) was size-segregated into aerosol<2.5μm in diameter (fine fraction, PM2.5) and aerosol>2.5 μm (coarse fraction). The Mössbauer spectra at room temperature show components assigned to mono- and polymeric species which are products related to hydrolysis of ferric solutions in the atmosphere. In order to extract reliable information regarding the quadrupole splittings necessary for identification of iron-containing compounds, the histogram method was used for evaluation of the Mössbauer spectra. The value and distribution of quadrupole splitting (QS) parameters obtained by this method suggests that the ultra fine particles (<10 nm) identified as a ferrihydrite, hematite and goethite were observed in the spectra both in fine and coarse fraction of the collected aerosol. However, the content of the individual chemical components was different for each fraction. The least crystalline form of ferrihydrite (QS≅0.85 mm) was observed in PM2.5 fraction more frequently than in the coarse fraction. The content of the ultra fine hematite particles which presence was confirmed in low temperature measurements was also larger in PM2.5 fraction than in the coarse fraction. Superparamagnetic behavior of iron-containing atmospheric aerosol was observed in low temperature Mössbauer spectra.