EPR investigation of iron in size segregated atmospheric aerosols collected at Dunkerque, Northern France

Electron paramagnetic resonance (EPR) spectroscopy was used to study atmospheric aerosols at Dunkerque, a French sea-side city located on the southern coast of the North Sea. Particles were collected in June–July 2001 and January–February 2002 periods using global filtration and cascade impaction. EPR spectra obtained for these particles were attributed to Fe3+ ions, mainly in the form of hematite (α-Fe2O3) in interaction with other paramagnetic species (Fe3+, Mn2+, Cu2+, etc.). From the EPR spectra intensities measured at 77 and 293 K, Fe3+ ions were evidenced in the form of clusters and agglomerated species. Fe3+ agglomerated species were observed mainly for winds blowing from the industrial park. Cascade impactor samples study evidenced that clusters are rather detected in the small size particles whereas agglomerated Fe3+ ions species are rather present in the large ones. The small size particles are richer in iron than the large ones, thus such particles play an important role in the value of EPR parameters.