北京地区表土磁性特征及其环境意义  

Magnetic properties of surface soils in Beijing area and their environmental implications

作　　者：朱艳明[1] 郭小蕾[1] 周力平[1] 

机构地区：[1]北京大学地理系,地表过程分析与模拟教育部重点实验室,北京100871

出　　处：《科学通报》2010年第17期1717-1725,共9页Chinese Science Bulletin

基　　金：教育部科学研究重大项目(306019);国家自然科学基金(49925307)资助项目

摘　　要：发展便捷快速的污染检测技术是当今环境研究的需要.能够有效地区分环境背景值与人为造成的污染是新的检测技术所必需的.近年来,磁学技术因其测量快速、简便的特点,正在逐步应用于城市环境污染监测中.城市或郊区的表土中磁性矿物来源复杂,能否通过磁学测量识别自然和人类活动的来源是土壤磁监测技术成为环境污染监测有效手段的关键所在.通过对北京城郊各区县地表0～10cm的表土层环境磁学性质的测量,初步获得了北京地区大尺度的表土磁性分布特征,对各区县表土的磁学性质与土壤母质、人类活动、地形地貌的相互关系进行了探讨.实验结果表明,在北京西北部和西南部的山地地区,表土的磁学性质主要受自然环境(地形地貌和母岩)的控制,磁性较强,大部分表土的磁化率(χlf)大于4×10-6m3/kg,为较粗颗粒的单畴(SD)或多畴(MD)亚铁磁性矿物;在北京中部和东部的山间谷地以及平原地区,表土的磁性较弱;而在一些工厂和交通要道附近,受到人类活动的影响,χARM/SIRM和χARM/χlf值明显增高,为较细颗粒的单畴-假单畴(SD-PSD)亚铁磁性矿物.在应用环境磁学参数对表土污染进行检测时,尤其是区分强磁性的土壤母质发育的表土和严重污染的表土时,χARM/SIRM和χARM/χlf比χlf,χARM和SIRM更为敏感.Convenient and fast techniques for detecting pollution are urgently needed in modern environmental studies.The ability to identify effectively environmental baseline is required for any of such new techniques.In recent years,the magnetic technique has been gradually applied to monitoring the urban environmental pollution.As the compositional origin of surface soil（0—10 cm,topsoils） from urban and suburb areas is complex,the key point for the magnetic technique to be used as an effective way of urban environmental monitoring is whether it can distinguish the natural processes from the human-induced effects.In this study,environmental magnetic measurements on the topsoils of all administrative districts and counties in the Beijing area were carried out.The characteristics of topsoils＇ magnetic properties in Beijing are present,along with their relationship to the location,parent material,type of human activity.The results indicate that the magnetic properties of the topsoils in the northwestern and southwestern mountainous regions are controlled mainly by the natural environmental（including the topography and parent material）.The magnetic susceptibility values of most topsoils here are larger than 4×10^-6 m^3/kg^-1 and the coarser（larger pseudo-single domain or multi-domain） ferrimagnetic minerals dominate,which are determined by the parent material.The magnetic properties of the topsoils in the central and eastern intermountain valleys and plains are relatively weak.Yet the values of χARM/SIRM and χARM/χlf of the topsoils near the industry sites and roads with heavy traffic in those regions are sharply increased due to the impact of human activities.The main magnetic minerals are finer（single domain-smaller pseudo-single domain） ferrimagnetic minerals.The results also show that the χARM/SIRM and χARM/χlf are more effective for discriminating the heavily polluted topsoils from those developed on the strong magnetic parent material.

关 键 词：北京地区 表土 磁学性质 环境背景 

分 类 号：X833[环境科学与工程—环境工程]