Chemical compositions and XANES speciations of Fe, Mn and Zn from aerosols collected in China and Japan during dust events

Abstract

Variations of the chemical composition and elemental speciation of aeolian dust transported from China to Japan were investigated in this study. During 6-12 April 2002, a large-scale dust event was observed in China, Korea, and Japan. Aerosol samples collected in Beijing, Fukuoka, Nagoya, and Tsukuba at that time were used for this study. Variations of most elemental concentrations against the particle size showed similar trends to that of Al concentration. The particle size distributions indicate that myriad elements in the aerosols originated mainly from mineral aerosols. The metal/Al concentration ratios showed little difference in chemical compositions for aerosols sampled at Beijing and Japanese stations: the chemical composition of aeolian dust is conserved during transportation. Examination by X-ray absorption near-edge structure (XANES) spectroscopy revealed that the Fe(III)/Total Fe (T-Fe) ratios of the aerosols collected in Beijing and Fukuoka were mutually resemblant, indicating that the oxidation-reduction reaction of Fe in aeolian dust during its transportation is negligible. However, their ratios were much higher than those of China loess and simulated Asian mineral dust (Chinese geo-reference materials: CJ-1 and CJ-2). Because the aerosol grain size is much smaller than those of CJ-1 and CJ-2, the fine mineral was transported selectively by wind from top soils. It was easily oxidized and had a high Fe(III)/TFe ratio. The XANES spectra of Mn in the aerosol indicated that the Mn(III)/Total Mn (T-Mn) ratios of the aerosol collected in Fukuoka were smaller than those of the dust collected in Beijing. The ratios of the aerosols in Beijing resembled those of CJ-1 and CJ-2. Moreover, only medium grains of the aerosol in Fukuoka had high Mn(III). The other grains had an almost identical Mn(III)/T-Mn ratio as the aerosol collected in Fukuoka in the no event. Thereby, most medium grain aerosols collected in Fukuoka comprised aeolian dust coming from China with high Mn(III)/T-Mn ratios like those of CJ-1 and CJ-2, but the other grain aerosols mixed greatly with local aerosols having low Mn(III)/T-Mn ratios. On the other hand, some elements such as Zn and Pb had different Al concentration ratios from Mn and Fe. The Zn/Al and Pb/Al concentration ratios of fine grains increased tenfold to a hundredfold with the decrease of particle size. Therefore, the increasing trend for these elements indicates that the fraction of anthropogenic materials was greatly increased in fine grains. The XANES spectra of Zn suggested that the contribution of mineral aerosols decreased gradually with decreasing particle size and that the residual components were explained by Zn(NO 3 ) 2 in coarse-medium grains and ZnSO 4 in fine grains. However, Zn in aeolian dust, which is a main component of mineral aerosols, only rarely originated from anthropogenic materials when a large-scale dust event was observed.

Structure and Magnetic Properties of Monodisperse Fe3+-doped CeO2 Nanospheres

“…Thus, this result indicates that most of the Fe ions in our samples are in the Fe 3+ valence state. These spectra at the Fe K edge are very similar to those of the Fe from aerosols samples reported by Ohta et al [34] showing a pre-edge feature approximately 7114 eV due to an electron excited from the Fe 1s to the Fe 3D final states. Figure 6 shows the field dependence of the specific magnetization (M -H curve) of undoped CeO 2 and Fedoped CeO 2 samples, obtained from VSM measurements at RT.…”

Mapping the physico-chemical properties of mineral dust in western Africa: mineralogical composition

“…Finally, our results on the iron oxide speciation are consistent with findings of different authors using XANES speciation (Wilke et al, 2001;Ohta et al, 2006;Prietzel et al, 2007;Majestic et al, 2007) and visible spectroscopy (Arimoto et al, 2002), indicating that Fe(III) is the dominant redox form of iron oxides and that goethite is the predominant form of iron oxide over hematite.…”

Ship impacts on the marine atmosphere: insights into the contribution of shipping emissions to the properties of marine aerosol and clouds

“…Manganese is primarily attributed to crustal minerals (Statham and Chester, 1988;Guieu et al, 1994;Ohta et al, 2006;Duvall et al, 2008). Iron and manganese concentrations were not strongly correlated to cloud water sulfate (R 2 = 0.27 and 0.29 for iron and manganese, respectively); therefore, the elevation of iron and manganese in cloud water during perturbed flights is likely indicative of air transported from continental sources.…”