宝鸡市大气降尘的磁学特征与环境意义  

Magnetic properties of dustfall in Baoji City and its implications of environment

作　　者：张俊辉[1] 张健[2,3] 王瑾[1] 靳美娟[1] 夏敦胜[4] 

机构地区：[1]宝鸡文理学院陕西省灾害监测与机理模拟重点实验室,陕西宝鸡721006 [2]西北大学城市与环境学院,陕西西安710127 [3]西北大学丝绸之路研究院,陕西西安710069 [4]兰州大学西部环境与气候变化研究院,甘肃兰州730000

出　　处：《干旱区地理》2015年第3期539-548,共10页Arid Land Geography

基　　金：陕西省教育厅科研计划项目资助(12JK0476)

摘　　要：对宝鸡市2011年1月~2013年12月连续3 a按月收集的大气降尘样品进行详细系统环境磁学实验分析。结果表明：宝鸡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。大气降尘的磁性矿物种类和粒径大小随季节并没有明显的变化,但是磁性矿物含量表现出明显的随年际和季节变化的特征。磁性矿物浓度呈现逐年降低的趋势,指示宝鸡市空气污染程度在逐年减轻,这可能与宝鸡市各种污染措施的实施有关,大气环境质量得到很好的控制和稳定。宝鸡市每年从10月份到次年3月份为磁性矿物浓度最大时期,这与冬季采暖期燃煤释放的污染物有关,另外宝鸡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。因此,依据污染来源、地形等因素进行合理的交通和产业布局则是宝鸡市大气污染防治的重要措施之一。The dustfall of the city is attached more and more importance because of its serious pollution. Environmental magnetism has been applied into many fields such as atmosphere contamination in monitoring urban environment pollution because it is capable of providing important information for studying the past regional or global environmental changes and the impact of human activity on environment. These samples were collected monthly from January 2011 to December 2013 at Baoji University of Arts and Sciences at Baoji City,Shaanxi Province,China. The magnetic parameters[Xlf,XARM,SIRM（Saturation Isothermal Remanent Magnetization）,FORC（First-Order Reversal Curve）diagrams and magnetic hysteresis parameters]were carried out on the samples of Baoji City dustfall. The Xlfof samples varies from 218.5 to 823.33 × 10-8m3·kg-1,with an average of388.51×10-8m3·kg-1,which is relative higher values. The IRM values of all the samples in a 100 m T field reached60% of the SIRM value,and those in a 300 m T field exceeded 90%. This indicates that the residual magnetism characteristics of the samples may be controlled by ferrimagnetic minerals,such as magnetite. SIRM and XARM values varies from 3 604.77 to 13 377.69×10-5Am2·kg-1and from 400.77 to 1 387.47×10-8m3·kg-1,with an average of 6 305.31×10-5Am2·kg-1and 734.18×10-8m3·kg-1,indicating the concentration of magnetic minerals is high. Almost all the hysteresis loops for the samples exhibit a relatively thin open wasp and are closed at 300 m T,indicating the presence of a ferrimagnetic phase. In addition,the coercive forces of residual magnetism were all less than 35 m T. The representative samples,which have no distinct peak and the centre Bc is about 10 m T,display this type of contour pattern as characteristic of multiple domain（MD）grains. The results show that a relative highly concentration of magnetic minerals in Baoji City,dominated by MD and pseudo-single domain（PSD）ferrimagnetic minerals. The magnetic minerals and grain size have no significant chan

关 键 词：大气降尘 磁学特性 污染 宝鸡市 

分 类 号：X513[环境科学与工程—环境工程]