We investigated smoke emissions from fires in savanna, forest, and agricultural ecosystems by airborne sampling of plumes close to prescribed burns and incidental fires in southern Africa. Aerosol ...samples were collected on glass fiber filters and on stacked filter units, consisting of a Nuclepore prefilter for particles larger than ∼1–2 μm and a Teflon second filter stage for the submicron fraction. The samples were analyzed for soluble ionic components, organic carbon, and black carbon. Onboard the research aircraft, particle number and volume distributions as a function of size were determined with a laser‐optical particle counter and the black carbon content of the aerosol with an aethalometer. We determined the emission ratios (relative to CO2 and CO) and emission factors (relative to the amount of biomass burnt) for the various aerosol constituents. The smoke aerosols were rich in organic and black carbon, the latter representing 10–30% of the aerosol mass. K+ and NH4+ were the dominant cationic species in the smoke of most fires, while Cl− and SO42− were the most important anions. The aerosols were unusually rich in Cl−, probably due to the high Cl content of the semiarid vegetation. Comparison of the element budget of the fuel before and after the fires shows that the fraction of the elements released during combustion is highly variable between elements. In the case of the halogen elements, almost the entire amount released during the fire is present in the aerosol phase, while in the case of C, N, and S, only a small proportion ends up as particulate matter. This suggests that the latter elements are present predominantly as gaseous species in the fresh fire plumes studied here.
We investigated smoke emissions from fires in savanna, forest, and agricultural ecosystems by airborne sampling of plumes close to prescribed burns and incidental fires in southern Africa. Aerosol ...samples were collected on glass fiber filters and on stacked filter units, consisting of a Nuclepore prefilter for particles larger than approximately 1-2 microns and a Teflon second-filter stage for the submicron fraction. The samples were analyzed for soluble ionic components, organic carbon, and black carbon. Onboard the research aircraft, particle number and volume distributions as a function of size were determined with a laser-optical particle counter and the black carbon content of the aerosol with an aethalometer. We determined the emission ratios (relative to CO2 and CO) and emission factors (relative to the amount of biomass burnt) for the various aerosol constituents. The smoke aerosols were rich in organic and black carbon, the latter representing 10-30 percent of the aerosol mass. K(+) and NH4(+) were the dominant cationic species in the smoke of most fires, while Cl(-) and SO4(2-) were the most important anions. The aerosols were unusually rich in Cl(-), probably due to the high Cl content of the semiarid vegetation. (Author)
We investigated smoke emissions from fires in savanna, forest, and agricultural ecosystems by airborne sampling of plumes close to prescribed burns and incidental fires in southern Africa. Aerosol ...samples were collected on glass fiber filters and on stacked filter units, consisting of a Nuclepore prefilter for particles larger than similar to 1-2 mu m and a Teflon second filter stage for the submicron fraction. The samples were analyzed for soluble ionic components, organic carbon, and black carbon. Onboard the research aircraft, particle number and volume distributions as a function of size were determined with a laser-optical particle counter and the black carbon content of the aerosol with an aethalometer. We determined the emission ratios (relative to CO sub(2) and CO) and emission factors (relative to the amount of biomass burnt) for the various aerosol constituents. The smoke aerosols were rich in organic and black carbon, the latter representing 10-30% of the aerosol mass. K super(+) and NH sub(4) super(+) were the dominant cationic species in the smoke of most fires, while Cl super(-) and SO sub(4) super(2-) were the most important anions. The aerosols were unusually rich in Cl super(-), probably due to the high Cl content of the semiarid vegetation. Comparison of the element budget of the fuel before and after the fires shows that the fraction of the elements released during combustion is highly variable between elements. In the case of the halogen elements, almost the entire amount released during the fire is present in the aerosol phase, while in the case of C, N, and S, only a small proportion ends up as particulate matter. This suggests that the latter elements are present predominantly as gaseous species in the fresh fire plumes studied here.
We investigated smoke emissions from fires in savanna, forest, and agricultural ecosystems by airborne sampling of plumes close to prescribed burns and incidental fires in southern Africa. Aerosol ...samples were collected on glass fiber filters and on stacked filter units, consisting of a Nuclepore prefilter for particles larger than similar to 1-2 mu m and a Teflon second filter stage for the submicron fraction. The samples were analyzed for soluble ionic components, organic carbon, and black carbon. Onboard the research aircraft, particle number and volume distributions as a function of size were determined with a laser-optical particle counter and the black carbon content of the aerosol with an aethalometer. We determined the emission ratios (relative to CO sub(2) and CO) and emission factors (relative to the amount of biomass burnt) for the various aerosol constituents. The smoke aerosols were rich in organic and black carbon, the latter representing 10-30% of the aerosol mass. K super(+) and NH sub(4) super(+) were the dominant cationic species in the smoke of most fires, while Cl super(-) and SO sub(4) super(2) super(-) were the most important anions. The aerosols were unusually rich in Cl super(-) , probably due to the high Cl content of the semiarid vegetation. Comparison of the element budget of the fuel before and after the fires shows that the fraction of the elements released during combustion is highly variable between elements. In the case of the halogen elements, almost the entire amount released during the fire is present in the aerosol phase, while in the case of C, N, and S, only a small proportion ends up as particulate matter. This suggests that the latter elements are present predominantly as gaseous species in the fresh fire plumes studied here.
Anodic oxidation of a copper rotating disk in hydrochloric acid is studied under steady-state conditions. At low current densities, a pseudo-Tafel behaviour varying with the speed of the rotating ...disk is observed. At potentials higher than −0.15
V/SCE, the value of the high frequency resistance, obtained from EIS measurements, increases and does not correspond to the sole resistance of the electrolytic solution. This behaviour is explained by the occurrence of the electroadsorption process. A two step mechanism for copper oxidation is studied with the only assumption of a constant chloride concentration at the interface. Kinetic zone diagrams are plotted and all the possible limiting kinetic behaviours of the model are pointed out. Interpretation of the experimental results reveals the limiting form taken by the current density vs potential curves.
This work focuses on the properties of 10–15
μm thick barium M-type hexaferrite (BaFe
12O
19 or BaM) films deposited by non-reactive RF magnetron sputtering on alumina substrates. High deposition ...rates were achieved through deposition at room temperature and operation at an RF power of 100
W. By varying sputtering gas pressure, the dc magnetic properties were correlated with structural, morphological and compositional properties obtained by X-ray diffraction (XRD), atomic force microscopy (AFM) and Rutherford backscattering spectrometry (RBS), respectively. A deposition pressure of
P=3
Pa enables one to reach the best compromise between high deposition rate (0.75
μm/h) and adequate crystallographic, stoichiometric and magnetostatic properties. Finally the gyromagnetic properties at high frequency were assessed through the characterization of coplanar isolator up to 60
GHz. As such, hexaferrite films prepared using this technique may offer opportunities for the next generation of self-biased planar microwave devices.
Anodic oxidation of a copper rotating disk in 1
M HCl is studied by electrochemical impedance spectroscopy (EIS). Experimental impedance diagrams show two capacitive loops separated in frequency. ...These diagrams validated with Kramers–Kronig relationships reveal a change in the frequency
f
c, at the apex of the low frequency loop, with the electrode potential. The theoretical expression for the impedance is derived and the possible limiting shapes of the impedance diagrams are discussed. The low frequency loop can take different forms as a convective-diffusion loop, a first order semi-circle or a mixed graph. An increase in
f
c with the electrode potential should be observed. Fitting of the impedance diagrams by the kinetic model gives good agreement with the experimental frequency distribution. A discussion is presented between the theoretical and experimental results.
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