Fe and Mn Oxidation States by TEM-EELS in Fine-Particle Emissions

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Fe and Mn Oxidation States by TEM-EELS in Fine-Particle Emissions from a Fe−Mn Alloy Making Plant Hélène Marris,† Karine Deboudt,*,† Pascal Flament,† Bernard Grobéty,‡ and Reto Gieré§ †

Université du Littoral Côte d’Opale, Laboratoire de Physico-Chimie de l’Atmosphère (LPCA), Bâtiment MREI2, 189A avenue Maurice Schumann, 59140 Dunkerque, France ‡ Department of Geosciences, University of Fribourg, Ch. du Musée 6, CH-1700 Fribourg, Switzerland § Institut für Geo- und Umweltnaturwissenschaften, Albert-Ludwigs-Universität, Albertrasse 23b, D-79104 Freiburg, Germany S Supporting Information *

ABSTRACT: Fine particles were sampled both inside the chimneys and in the near-field of an Fe−Mn-alloy manufacturing plant. The transfer from one point to another point in the environment, as well as the bioavailability and toxicity of these two metals, depend above all on their speciation. The oxidation states of iron and manganese in the collected particles were determined by using transmission electron microscopy coupled with electron energy-loss spectroscopy (TEM-EELS). The mineralogical identity of these metal-rich particles was determined by selected area electron diffraction (SAED) coupled with energy-dispersive X-ray spectroscopy (EDX). This study shows that both iron and manganese in metallic particles are prone to oxidation reactions via gas/particle conversion mechanisms, which take place in the flue gases within the smoke stacks. This phenomenon is more pronounced for the smallest Fe-rich particles. However, no further change of oxidation state of the two elements was observed in the near-field of the plant, after emission into the atmosphere (within 3.0 can be attributed to these phases. The SAED patterns of small (50−200 nm) euhedral particles, frequently with hexagonal outlines (Figure 7), can be indexed for the spinel phase hausmannite, also identified by XRD. The well-crystallized core of the composite particles can also be indexed for hausmannite (Figure 8). This phase is the

Near-Field Evolution of Oxidation States. Consistent with the observations made for particles collected inside the chimneys, the distribution of the oxidation states of Fe and Mn is homogeneous in all studied particles collected at station S1, i.e. from the near-field plume in proximity of the emission points. This observation holds irrespective of the sampling day. However, at station S2, which is located further away from the emission points, some particles show a heterogeneous distribution of the oxidation states of Fe and Mn (Figure 9). This heterogeneity probably results from the agglomeration of metallic particles with other types of particles.35 This conclusion is supported by direct observations in bright-field TEM images, where metallic particles (dark contrast) are seen to be associated with particles that display a lighter contrast and a distinct shape, which suggests they are sheet silicates, consistent with the EDX spectra (Figure 9A). Metallic particles collected in the near-field of the plant contain manganese and iron with an oxidation state that is mainly between +II and +III (Figure 10), with average values of 2.6 ± 0.5 and 2.7 ± 0.2, respectively. No systematic difference can be recognized between different sampling days. These average values are identical to those determined for particles collected inside the chimneys, which indicates that the particles, once emitted into the atmosphere, do not undergo a significant change in the global oxidation states of iron and manganese within the spatial, and thus temporal, framework of our study. It appears that, in a general manner, the iron in the smallest particles is more oxidized than in the coarser ones (Figure 10). This correlation between size and oxidation state of Fe, although not statistically strong (r2 = 0.14), has also been observed for particles collected inside the chimneys (r2 = 0.40, see Figure 4) and must be related to the higher reactivity of the smallest particles.38 Moreover, we notice the presence of Mn-bearing particles with an oxidation state between 3.6 and 4.2 at the individualparticle scale (Figure 10). The same kind of particles has also been observed among the source particles collected in the CA chimney. The elongated shape of these more strongly oxidized particles (Figure 11) is typical of pyrolusite, a tetragonal Mnoxide phase (β-MnO2). This high oxidation state, therefore, probably existed already when the particles were emitted at the source (see, e.g., the lath-shaped crystals identified as cryptomelane/birnessite), and is not the result of oxidation in

Figure 8. Hausmannite crystal surrounded by cryptomelane laths.

most frequently observed particle type. Mixtures of hausmannite and cryptomelane will give average valence values between 2.6 and 4.0, depending on their relative abundances. All these observations are in good agreement with the Mn oxidation states observed for source particles by TEM-EELS.

Figure 9. TEM data and images of two representative metal-bearing particles collected in the near-field on June 17 (at station 2, 1550 m from the main emission points). EDX spectra show composition of the entire particle; EEL spectra and mean oxidation states of (A) manganese and (B) iron valid for areas indicated in the respective bright-field images. 10837

dx.doi.org/10.1021/es400368s | Environ. Sci. Technol. 2013, 47, 10832−10840

Environmental Science & Technology

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Figure 10. Mean oxidation states of manganese (top; empirical plot method) and iron (bottom, fitting method) in industrial particles for samples collected at the near-field stations S1 (500 m from chimneys) and S2 (about 1500 m from chimneys) on different days.

Figure 11. TEM data and images of two typical Mn-oxide particles, tentatively identified as pyrolusite (β-MnO2). Particles were collected (A) inside the CA chimney and (B) in the near-field plume (S2, June 17). EDX spectra show composition of the entire particle; EEL spectra and mean oxidation states of manganese valid for areas indicated in the respective bright-field images.

Far-Field Evolution of Oxidation States. During longrange transport, particles evolve, and oxidation−reduction reactions can occur. These mechanisms are well-known for iron,8,9,39 but not for manganese. They include the following processes: (1) particles can evolve by photo-oxidation, e.g., with ozone. Nico et al. 38 simulated atmospheric aging of Fe- and Mn-bearing ultrafine particles and showed long reaction times for photo-oxidation (10 to 20 h);38 (2) particles can evolve in the aqueous environment within clouds and fog. These humid conditions lead to partial dissolution of particles with water

the atmosphere, as the atmospheric residence times in the sampled near-field plume were only a few minutes, which is probably not sufficiently long for conversion mechanisms. This conclusion is consistent with the variable oxidation states observed in all studied near-field plume samples (Figure 10). The temporal variability of the relative proportion of particles coming from the three main chimneys, due to variability of the industrial activities, should explain the presence of these oxidized Mn-rich particles in only two (S2, May 21; S2, June 17) of the five samples collected in the near-field plume. 10838



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(7) Buseck, P. R.; Adachi, K. Nanoparticles in the atmosphere. Elements 2008, 4 (6), 389−394. (8) Erel, Y.; Pehkonen, S. O.; Hoffmann, M. R. Redox Chemistry of Iron in Fog and Stratus Clouds. J. Geophys. Res.-Atmos. 1993, 98 (D10), 18423−18434. (9) Zhuang, G.; Yi, Z.; Duce, R. A.; Brown, P. R. Chemistry of iron in marine aerosols. Global Biogeochem. Cycles 1992, 6, 161−173. (10) de Baar, H. J. W.; de Jong, J. T. M.; Bakker, D. C. E.; Löscher, B. M.; Veth, C.; Bathmann, U.; Smetacek, V. Importance of iron for plankton blooms and carbon dioxide drawdown in the Southern Ocean. Nature 1995, 373, 412−415. (11) Jickells, T.; An, Z. S.; Andersen, K. K.; Baker, A. R.; Bergametti, G.; Brooks, N.; Cao, J. J.; Boyd, P. W.; Duce, R. A.; Hunter, K. A.; Kawahata, H.; Kubilay, N.; La Roche, J.; Liss, P. S.; Mahowald, N.; Prospero, J. M.; Ridgwell, A. J.; Tegen, I.; Torres, R. J. Global iron connections between desert dust, ocean biogeochemistry and climate. Science 2005, 308, 67−71. (12) Mahowald, N. M.; Baker, A. R.; Bergametti, G.; Brooks, N.; Duce, R. A.; Jickells, T. D.; Kubilay, N.; Prospero, J. M.; Tegen, I. Atmospheric global dust cycle and iron inputs to the ocean. Global Biogeochem. Cycles 2005, 19, 4. (13) Donaldson, K.; Brown, D. M.; Mitchell, C.; Dineva, M.; Beswick, P. H.; Gilmour, P.; MacNee, W. Free radical activity of PM10: Iron-mediated generation of hydroxyl radicals. Environ. Health Perspect. 1997, 105, 1285−1289. (14) Clarke, A. G.; Radojevic, M. Oxidation Rates of SO2 in SeaWater and Sea-Salt Aerosols. Atmos. Environ. 1984, 18 (12), 2761− 2767. (15) Grgic, I.; Dovzan, A.; Hudnik, V. The role of atmospheric aerosols in SO2 oxidation: catalytic effect of iron in the presence of organic ligands. J. Aerosol Sci. 1996, 27 (1), S657−S658. (16) Chu, B.; Hao, J.; Takekawa, H.; Li, J.; Wang, K.; Jiang, J. The remarkable effect of FeSO4 seed aerosols on secondary organic aerosol formation from photooxidation of pinene/NOx and Toluene/NOx. Atmos. Environ. 2012, 55, 26−34. (17) Könczöl, M.; Ebeling, S.; Goldenberg, E.; Treude, F.; Gminski, R.; Gieré, R.; Grobéty, B.; Rothen-Rutishauser, B.; Merfort, I.; MerschSundermann, V. Cytotoxicity and genotoxicity of size-fractionated iron oxide (magnetite) in A549 human lung epithelial cells: Role of ROS, JNK and NF-kB. Chem. Res. Toxicol. 2011, 24, 1460−1475. (18) Valavanidis, A.; Salika, A.; Theodoropoulou, A. Generation of hydroxyl radicals by urban suspended particulate air matter. The role of iron ions. Atmos. Environ. 2000, 34 (15), 2379−2386. (19) Dedik, A. N.; Hoffmann, P.; Ensling, J. Chemical characterization of iron in atmospheric aerosols. Atmos. Environ. Part A-Gen. Topics 1992, 26 (14), 2545−2548. (20) Kopcewicz, B.; Kopcewicz, M. Long-term measurements of iron-containing aerosols by Mössbauer spectroscopy in Poland. Atmos. Environ. 2001, 35 (21), 3739−3747. (21) Kopcewicz, B.; Kopcewicz, M. Mössbauer study of ironcontaining atmospheric aerosol in relation to the air pollution. Geophys. Res. Abstr. 2003, 5, 03729. (22) Oberg, T.; Bergblack, B.; Filipsson, M. Catalytic effects by metal oxides on the formation and degradation of chlorinated aromatic compounds in fly ash. Chemosphere 2008, 71, 1135−1143. (23) Santamaria, A. B.; Sulsky, S. I. Risk assessment of an essential element: Manganese. J. Toxicol. Environ. Health, Part A 2010, 73 (2− 3), 128−155. (24) Antonini, J.; Santamaria, A.; Jenkins, N.; Albini, E.; Lucchini, R. Fate manganese associated with the inhalation of welding fumes: Potential neurological effects. Neurotoxicology 2006, 27, 304−310. (25) Loomer, D.; Al, T.; Weaver, L.; Cogswell, S. Manganese valence imaging in Mn minerals at the nanoscale using STEM-EELS. Am. Mineral. 2007, 92, 72−79. (26) Ledoux, F.; Laversin, H.; Courcot, D.; Courcot, L.; Zhilinskaya, E. A.; Puskaric, E.; Aboukaïs, A. Characterization of iron and manganese species in atmospheric aerosols from anthropogenic sources. Atmos. Res. 2006, 82, 622−632.

vapor condensation on their surfaces, which is the reason why, in polluted atmospheric environments, Mn and Fe are usually found as Mn(IV) and Fe(III).40 After emission by metallurgical plants, Fe- and Mn-particles are due to evolve during their longrange atmospheric transport, primarily by oxidation mechanisms, which will mostly depend on pH conditions and time scales.27 The evolution of oxidation states of Fe and Mn will most likely also affect (bio)availability and toxicity of the metals in the environment.

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ASSOCIATED CONTENT

S Supporting Information *

Supporting Information associated with this article can be found in the supplementary data section. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +33/328237631; fax.: +33/328658244; e-mail: karine. [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors thank Christoph Maschowski for the Rietveld analysis of XRD spectra. The Laboratoire de Physico-Chimie de l′Atmosphère participates in the Institut de Recherche en ENvironnement Industriel (IRENI), which is financed by the Communauté Urbaine de Dunkerque, the Région Nord Pas-deCalais, the Ministère de l′Enseignement Supérieur et de la Recherche, the CNRS, and European Regional Development Fund (ERDF). Financial support from ADEME is gratefully acknowledged. We also thank Vale Manganese France (VMF) for their collaboration in this study and LECES for sampling inside the chimneys. TEM measurements were performed at the TEM national Facility in Lille (France), supported by the “Conseil Régional du Nord-Pas de Calais”, the European Regional Development Fund (ERDF), and the “Institut National des Sciences de l′Univers (INSU, CNRS)”. The five reviewers are fully acknowledged for their helpful comments.

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REFERENCES

(1) Martley, E.; Gulson, B.; Pfeifer, H. Metal concentrations in soils around the copper smelter and surrounding industrial complex of Port Kembla, NSW, Australia. Sci. Total Environ. 2004, 325 (1−3), 113− 127. (2) Prati, P.; Zucchiatti, A.; Lucarelli, F.; Mando, P. Source apportionment near a steel plant in Genoa (Italy) by continuous aerosol sampling and PIXE analysis. Atmos. Environ. 2000, 34, 3149− 3157. (3) Flynn, M. R.; Susi, P. Neurological risks associated with manganese exposure from welding operations–a literature review. Int J. Hyg. Environ. Health 2009, 212, 5. (4) Gieré, R.; Blackford, M.; Smith, K. TEM study of PM2.5 emitted from coal and tire combustion in a thermal power station. Environ. Sci. Technol. 2006, 40, 6235−6240. (5) Majestic, B. J.; Schauer, J. J.; Shafer, M. M. Develment of a manganese speciation method for atmospheric aerosols in biologically and environmentally relevant fluids. Aerosol Sci. Technol. 2007, 41 (10), 925−933. (6) Pope, C.; Burnett, R.; Thun, M.; Calle, E.; Krewski, D.; Ito, K.; Thurston, G. Lung cancer, cardiopulmonary mortality and long-term exposure to fine particulate air pollution. J. Am. Med. Assoc. 2002, 287 (9), 1132−1141. 10839



Article

(27) Ure, A. M.; Davidson, C. M. Chemical Speciation in the Environment; Blackie Academic & Prof.: London, 1995. (28) Cavé, L.; Al, T.; Loomer, D.; Cogswell, S.; Weaver, L. A STEM/ EELS method for mapping iron valence ratios in oxide minerals. Micron 2006, 37 (4), 301−309. (29) Chen, Y. Z.; Shah, N.; Huggins, F. E.; Huffman, G. P. Characterization of ambient airborne particles by energy-filtered transmission electron microscopy. Aerosol Sci. Technol. 2005, 39 (6), 509−518. (30) Calvert, C. C.; Brown, A.; Brydson, R. Determination of the local chemistry of iron in inorganic and organic materials. J. Electron Spectrosc. Relat. Phenom. 2005, 143 (2−3), 173−187. (31) Chen, Y.; Shah, N.; Huggins, F. E.; Huffman, G. P.; Linak, W. P.; Andrew Miller, C. Investigation of primary fine particulate matter from coal combustion by computer-controlled scanning electron microscopy. Fuel Process. Technol. 2004, 86, 743−761. (32) Deboudt, K.; Flament, P.; Choel, M.; Gloter, A.; Sobanska, S.; Colliex, C. Mixing state of aerosols and direct observation of carbonaceous and marine coatings on African dust by individual particle analysis. J. Geophys. Res.-Atmos. 2010, 115 (D24), 2156−2202. (33) European-Commission Integrated Pollution Prevention and Control (IPPC) - Reference document on best available techniques in the non ferrous metals industries; 2001. (34) Malan, J.; Barthel, W.; Dippenaar, B. A. Optimizing manganese ore sinter plants: process parameters and design implications. Proceedings: Tenth International Ferroalloys Congress; 2004, 09584663-5-1. (35) Marris, H.; Deboudt, K.; Augustin, P.; Flament, P.; Blond, F.; Fiani, E.; Fourmentin, M.; Delbarre, H. Fast changes in chemical composition and size distribution of fine particles during the near-field transport of industrial plumes. Sci. Total Environ. 2012, 427, 126−138. (36) Stadelmann, P. EMS - a software package for electron diffraction analysis and HREM image simulation in materials science. Ultramicroscopy 1987, 21, 131−145. (37) Ahn, Y. C.; Lee, J. K. Physical, chemical, and electrical analysis of aerosol particles generated from industrial plants. Aerosol Sci. 2006, 37, 187−202. (38) Nico, P.; Kumfer, B.; Kennedy, I.; Anastasio, C. Redox dynamics of mixed metal (Mn, Cr, and Fe) ultrafine particles. Aerosol Sci. Technol. 2009, 43, 30−70. (39) Meskhidze, N.; Chameides, W. L.; Nenes, A. Dust and pollution: A recipe for enhanced ocean fertilization? J. Geophys. Res.Atmos. 2005, 110 (D3), D03301. (40) Skinner, C.; Fitzpatrick, R. Biomineralization: processes of iron and manganese: modern and ancient environments; Catena-Verlag: Verlag, 1992; p 432.

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Fe and Mn Oxidation States by TEM-EELS in Fine-Particle Emissions

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