Magnetic characteristics of dustfall in urban area of north China and its environmental significance  

作　　者：XIA DunSheng1,2, YANG LiPing2, MA JianYing1, YU Ye1, WANG Guan2 & CHEN FaHu2 1 Key Laboratory of Desert and Desertification, Institute of Cold and Arid Regions Environmental and Engineering, Chinese Academy of Sciences, Lanzhou 730000, China 2 CAEP, Key Laboratory of West China’s Environmental System (Ministry of Education), Lanzhou University, Lanzhou 730000, China 

出　　处：《Science China Earth Sciences》2007年第11期1724-1732,共9页中国科学（地球科学英文版）

基　　金：Supported by the National Natural Science Foundation of China (Grant Nos. 40571147, 40401064, 90502008 and 40421101);the International Collaboration Project of Chinese Ministry of Science and Technology (Grant No. 2002CB714004)

摘　　要：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 (χ_(1f),χ_(fd)%, χ_(ARM), 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 of M_(rs)/M_s vs. B_(cr)/B_c and χ_(fd)% vs. χ_(ARM)/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.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 of Mrs/Ms vs. Bcr/Bc and χfd% vs. χARM/SIRM indicate that the main magnetic grain sizes are pseudo-single-domain (PSD). The high concentration of magnetic min-erals in the dustfall indicates that Lanzhou is seriously polluted. The main pollution sources are an-thropogenic 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.

关 键 词：environmental magnetism dustfall air pollution Lanzhou 

分 类 号：X16[环境科学与工程—环境科学]