西安市道路灰尘磁学特征及其对环境的响应

西安市道路表面灰尘样品的环境磁学研究显示磁化率(χ)、非磁滞磁化率（χ_ARM）以及饱和等温剩磁（SIRM）均比较高，表明样品中磁性矿物含量较高.其中磁化率（χ）主要受人类活动强度影响，而非磁滞磁化率（χ_ARM）及饱和等温剩磁（SIRM）则由人为活动强度和磁性矿物种类共同决定.κ-T曲线以及等温剩磁（IRM）获得曲线显示样品中磁铁矿和磁赤铁矿等亚铁磁性矿物占主导，并可能含有少量的单质铁，其相对含量与人类活动种类有关：与单纯的交通排放及冶金活动相比，密集的人群流动可带来更多的单质铁矿物.磁畴图谱显示磁性矿物粒径变化不大，以准单畴及多畴颗粒等粗颗粒为主，明显大于成土作用形成的磁性颗粒.综合磁性矿物含量种类以及粒径可辨别污染及污染来源，提供污染监测的磁学手段，并初步进行污染来源划分.

Magnetic properties of street dust: a case in Xi'an city, Shaanxi province, China

The systematic analysis on the magnetic characteristics of street dust from Xi'an city indicates high concentration of magnetic minerals corresponding to the high value of the magnetic susceptibility(χ), the anhysteretic susceptibility (χ_(ARM)) and the saturation isothermal remnant magnetization(SIRM). The value of χ is positively correlated to the intensity of human activity and the value of the χ_(ARM) and the SIRM is determined by the intensity and the magnetic mineralogy. The κ-T curve and the IRM acquisition curve indicated that the sample is dominated by ferromagnetic minerals, such as magnetite and maghemite, as well as some iron, the relative concentration of the iron might be related to the variety of the human activity: there are more iron minerals from the human flow pollution than the pure traffic pollution and the industry. From the King-plot and the Dearing-plot we can conclude that most magnetic domains of the magnetic minerals are pseudo-single domain and multidomain. Our results suggested that magnetic measurements could be used to identify the varieties and sources of pollutants in street dust, and as the potential tools for monitoring and classifying the pollution.