Magnetic characteristics of dustfall in urban area of north China and its environmental significance
Magnetic characteristics of dustfall in urban area of north China and its environmental significance
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DOI：
10.1007/s11430-007-0094-9
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
D. Xia;Li-ping Yang;Jian-ying Ma;Ye Yu;Guan Wang;Fahu Chen
中科院分区：
文献类型：
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作者：
D. Xia;Li-ping Yang;Jian-ying Ma;Ye Yu;Guan Wang;Fahu Chen
城市颗粒物污染物不仅影响城市空气质量，而且直接威胁公众健康。由于特殊的地球物理位置和气候条件，兰州一直是世界上污染最严重的城市之一，这使得它成为研究城市颗粒物污染的理想场所。对兰州大学1997.4-2000.5和2004.11-2005.10两个月的降尘样品进行了环境磁学参数(χlf、χFd%、χARM、SIRM、HIRM、软场和背场IRM)的测量和分析。结果表明，降尘中的磁性矿物主要为磁铁矿，并含有少量磁铁矿和赤铁矿。MRS/Msvs.Bcr/Bcr和χFd%与χARM/SIRM的交叉图表明，主要的磁晶尺寸为伪单畴(Psd)。降尘中磁性矿物含量较高，表明兰州市污染严重。主要污染源是人类活动和自然扬尘，前者全年威胁较大，不同于一般认为夏季自然扬尘是主要污染源的观点。在过去几十年里，在政府和地方当局的大力努力下，兰州的空气质量在冬季有所改善，但在夏季并不明显。这项研究还表明，环境磁学作为一种简单、快速、准确的技术，可以成为城市污染研究的一种有价值的工具。
Urban particulate pollutants not only affect urban air quality but also directly threaten public health. Lanzhou has been one of the most seriously polluted cities in the world due to its special geophysical location and weather conditions, which makes it an ideal place for urban particulate pollution study. In this study a set of environmental magnetic parameters (χlf,χfd%,χARM, SIRM, HIRM, SOFT and back field IRM) were measured and analyzed for the dustfall samples collected monthly during 1997.4–2000.5 and 2004.11–2005.10 at Lanzhou University campus (KLD and CCS) and at a clear site of Gaolanxian (GLX). Results demonstrate that the main magnetic minerals in the dustfall are magnetite, with some maghaemite and haematite. Cross plots ofMrs/Msvs.Bcr/Bcandχfd% vs.χARM/SIRM indicate that the main magnetic grain sizes are pseudo-single-domain (PSD). The high concentration of magnetic minerals in the dustfall indicates that Lanzhou is seriously polluted. The main pollution sources are anthropogenic activities and nature dust, with the former posing a great threat during the whole year, which is different from the general view that the natural dust is the main contributor in summer. With great efforts of the government and local authority in the past decades, the air quality in Lanzhou has been improved in winter, but it is not so obvious in summer. This study also reveals that as a simple, rapid and accurate technology, environmental magnetism could be a valuable tool for urban pollution study.