Shi Zongbo, Zhang Daizhou, Ji Hezhe, Hasegawa Shuichi, Hayashi Masahiro
Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Kumamoto 862-8502, Japan.
Sci Total Environ. 2008 Jan 15;389(1):195-201. doi: 10.1016/j.scitotenv.2007.08.016. Epub 2007 Sep 25.
Aerosol samples in the urban atmosphere of Kumamoto (32 degrees 48'N, 134 degrees 45'E) in southwestern Japan were collected onto aluminum foil strips. Parts of the samples were heated to 550 degrees C in pure helium gas, and oxygen (2%)-helium (98%) mixture gas. Particles in unheated and heated parts were characterized individually by their morphology and elemental composition using a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. There were mainly two types of soot-containing particles according to the morphology: chain-like and sub-round. Chain-like particles were likely young soot particles because such particles in heated specimens showed similar morphology to those in unheated specimen. In contrast, the sub-round particles were composed of volatile species encapsulated with soot. The heating caused partial evaporation of such particles, and the soot inclusions could be identified only after the heating. The volatile species frequently contained sulfur compounds, but sulfur was not detected in the residues, suggesting that the volatile species were mainly produced on soot particles in the atmosphere. The sub-round soot-containing particles were approximately 3 times larger in diameter than the inclusions. These results suggest that soot particles could be substantially modified in size and composition by volatile species in the urban atmosphere.
在日本西南部熊本（北纬32度48分，东经134度45分）的城市大气中，气溶胶样本被收集到铝箔条上。部分样本在纯氦气以及氧气（2%）-氦气（98%）混合气体中加热至550摄氏度。使用配备能量色散X射线光谱仪的扫描电子显微镜，分别根据未加热和加热部分颗粒的形态和元素组成对其进行表征。根据形态，主要有两种含碳烟颗粒：链状和次圆形。链状颗粒可能是年轻的碳烟颗粒，因为加热样本中的此类颗粒与未加热样本中的颗粒形态相似。相比之下，次圆形颗粒由包裹着碳烟的挥发性物质组成。加热导致此类颗粒部分蒸发，只有在加热后才能识别出其中的碳烟夹杂物。挥发性物质中经常含有硫化合物，但在残留物中未检测到硫，这表明挥发性物质主要是在大气中的碳烟颗粒上产生的。含次圆形碳烟的颗粒直径大约是夹杂物的3倍。这些结果表明，城市大气中的挥发性物质可能会使碳烟颗粒在尺寸和组成上发生显著改变。
