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Magnetic properties of the urban soils in Lanzhou and their environmental implications. |
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Abstract Magnetic characteristics in 117 surface soil samples collected from Lanzhou City, China were systematically analyzed. Low-coercivity magnetite dominated the magnetic properties in the samples. Values of magnetic mineral concentration parameters were high in the following four areas: (1) the industrial area centered by Lanzhou aluminum plant power and Xigu thermal power plant. (2) Yanerwan, LanDong building materials market enterprise and leather factory. (3) The long and narrow stripe region along the materials market - West Station - Xiaoxihu Park - Chengguan Bridge. (4) The area surrounding Shuishang Park. And low values presented in Anning District (especially Jiuzhou Development Zone) and the south of Qilihe District. In addition, the result from soil profiles showed high values of clf and SIRM in the upper 20cm near the surface and then significantly decreasing, which indicated that contamination was confined in a depth of the upper 20cm. Contrasting with nature samples, magnetic characteristics of polluted materials, such as topsoil, street dust, dust fall, and river sediment, was simplex and dominated by magnetite. Moreover, differences were also observed in the correlation between magnetic susceptibility and percentage frequency magnetic susceptibility, which was positive in nature samples but was negative in anthropogenic materials. Therefore environmental magnetism can be used as a tool for large-scale and high resolution pollution monitoring.
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Received: 23 October 2012
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