Acta Geographica Sinica ›› 2012, Vol. 67 ›› Issue (1): 36-44.doi: 10.11821/xb201201004

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Magnetic Properties of Dustfall in Lanzhou City and Its Environmental Significance

FENG Hua1, LIU Xiuming2,3, LV Bin1, MA Mingming1, LI Pingyuan1, LIU Zhi1, ZHAO Guoyong1, MAO Xuegang1   

  1. 1. Key Laboratory of Western China's Environmental System Ministry of Education, Lanzhou University, Lanzhou 730000, China;
    2. College of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China;
    3. Department of Environment and Geography, Macquarie University, Sydney NSW 2109, Australia
  • Received:2011-09-08 Revised:2011-10-18 Online:2012-01-20 Published:2012-01-20
  • Supported by:
    National Natural Science Foundation of China, No.41072124; No.40830105; No.40721061

Abstract: Environmental magnetic measurements were carried out on the samples of Lanzhou dustfall. These samples were collected monthly during April 2007 to June 2011 at Lanzhou University. The magnetic parameters (χlf, SIRM, χARM, k-T curves and magnetic hysteresis parameters) indicate a high concentration of magnetic minerals in Lanzhou, dominated by pseudo-single domain (PSD) magnetite, but also contain maghemite, lepidocrocite and hematite. They mainly come from pollution of human activities. The parameter χlf can effectively denote the concentration variations of magnetic mineralogy of polluted dustfall. Previous studies have shown that χlf value in Lanzhou dustfall has significant variations during the year. The value of χlf is distinctly high in the heating months, while low in other months. Although March is also in the heating period, its χlf value is obviously lower than other that of heating months, which might be due to the unique inversion phenomenon of Lanzhou basin: low intensity of ground inversion being conducive to the diffusion of pollutants. April and May have the lowest values throughout the year, and the reasons could be 1) low intensity of ground inversion, and 2) dilution effect of frequent occurrence of dust storms (with low χlf) in these months. The air quality of Lanzhou has been greatly improved in winter for the last four years. In 2010, the χlf value is 38% lower than that in 2007, indicating that environmental magnetism can effectively monitor urban pollution.

Key words: environmental magnetism, dustfall, intensity of ground inversion, pollution monitoring, Lanzhou