对西安市电子二路(XZ)和长安区郭杜镇(XCA)两个样点2012年1月至2013年12月连续两年的大气降尘进行详细系统环境磁学实验分析。结果表明:西安市大气降尘中磁性矿物含量相对较高,主要的磁性矿物为多畴和假单畴的低矫顽力亚铁磁性矿物,并伴有少量的赤铁矿等高矫顽力的硬磁性矿物,磁畴主要由粗颗粒的MD(多畴)和PSD(准单畴)组成。XZ样点大气降尘的磁性浓度和磁性矿物的粒径大于XCA样点,表明城市不同功能区污染源类型存在差异。西安市大气降尘磁性矿物含量表现出明显的季节变化的特征,5-8月(夏季)磁性矿物的浓度明显较低,10月到次年的1月(冬季)是磁性矿物浓度最大的时期,这主要与采暖期排放源的变化有关,另外,西安市特殊的地形和气象因素对大气粉尘的扩散产生重要的影响,导致冬季粉尘的富集。
Environmental magnetic measurements were carried out on the dustfall samples from Xi'an. These samples were collected in every month from January 2012 to December 2013 at XZ and XCA sites. The magnetic parameters (χlf, χARM, SIRM, FORC diagram and magnetic hysteresis parameters) indicate a relatively high concentration of ferrimagnetic minerals in Xi'an, dominated by multiple domain (MD) and pseudo-single domain (PSD) ferrimagnetic minerals. The concentration of magnetic minerals in XZ site is higher than those in XCA site, suggesting the different pollution sources in different functional district of Xi'an. The concentration of magnetic minerals has significant changes according to the seasons in each year, and the values rise from October to January of next year, and decrease in summer, which mainly not only come from the pollution of coal-burning, but also are influenced by the special topography and meteorological conditions.
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