The thermal deactivation of diesel soot particles exerts a significant influence on the control strategy for the regeneration of diesel particulate filters (DPFs). This work focused on the changes in the surface functional groups, carbon chemical state, and graphitization degree during thermal treatment in an inert gas environment at intermediate temperatures of 600°C, 800°C, and 1000°C and explore the chemical species that were desorbed from the diesel soot surface during thermal treatment using a thermogravimetric analyser coupled with a gas-chromatograph mass spectrometer (TGA-GC/MS). The surface functional groups and carbon chemical state were characterized using Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The graphitization degree was evaluated by means of Raman spectroscopy (RS). The concentrations of aliphatic C–H, C–OH, C=O, and O–C=O groups are reduced for diesel soot and carbon black when increasing the thermal treatment temperature, while the sp2/sp3 hybridized ratio and graphitization degree enhance. These results provide comprehensive evidence of the decreased reactivity of soot samples. Among oxygenated functional groups, the percentage reduction during thermal treatment is the largest for the O–C=O groups owing to its worst thermodynamic stability. TGA-GC/MS results show that the aliphatic and aromatic chains and oxygenated species would be desorbed from the soot surface during 1000°C thermal treatment of diesel soot. 相似文献
Time series of nanoparticle number concentration during new particle formation (NPF) events in the urban environment of Brisbane, Australia, showed that the formation of charged particles often occurred before that of neutral particles. We monitored 241 days during the calendar year 2012 over which NPF events were observed on 108 days. We studied the times at which the charged and neutral particle concentrations in the size range 1.8–3.2 nm reached their peak values and found that they were clearly different in 50 events with the peak neutral particle concentration lagging behind the charged particle concentration during 42 of these events with a mean time lag of 24±12 min. While the charged particles were more likely to form before the neutral particles, once formed, the growth rate of the particles did not depend on their charge. While ion-induced nucleation is not the dominant mechanism of NPF in the atmosphere, our observations suggest that the presence of ions in the atmosphere plays a role that cannot be ignored.
Excessive air pollution may adversely affect plant growth and development. The overall objective of this research was to elucidate some microscopic effects of diesel exhaust particles (DEP) on the formation, development, and structure of pollen grains and its proteins in Phaseolus vulgaris L. Bean plants were grown in experimental pots and treated with different concentrations of the water-soluble fraction of DEP. Flowers and young buds were removed, fixed in FAA70 (formalin?:?acetic acid?:?ethanol, 2?:?1?:?17), and subjected to developmental studies. Our results show that DEP cause some abnormalities during pollen development. Pollen grains in normal plants are spherical in equatorial view and triangular in polar view; in DEP-treated plants, they were changed into irregular shapes in equatorial view and asteroidal in polar view. Delay in degeneration of the tapetum layer of the anther, and formation of giant, irregular, and non-fertile pollen grains are other results of DEP treatment. Gel electrophoretic studies revealed that a new protein with a molecular mass of 80?kD was formed in the DEP-treated group. Some pollen proteins may act as allergens, considering the fact that pollen allergy frequency is increased in polluted areas; the possibility arises that DEP could be an effective agent entail formation of detoxifying proteins which, on the other hand, can also act as allergens. 相似文献
