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As the largest industrial city locating in the Northwestern China, Lanzhou has become one of the most seriously polluted cities in the world. In this study, investigations were performed on the magnetic properties, heavy metals and organic matter contents of a total of 23 sediment samples collected from eight selected rivers in the Lanzhou urban area. The results of the study indicate that the magnetic properties of the sediment samples are predominated by low-coercivity magnetite. The river sediments are classified into three types, i.e., downstream polluted, upstream polluted, and less affected, based on the contribution from anthropogenic activities in different segments of the river as indicated by the variation of magnetic mineral concentration parameters. Moreover, a strong linear positive correlation exists among some of the magnetic parameters and organic matter content, heavy metals (Cr, Ni, Pb, Zn, Fe) and total enrichment factor ( R) of the bulk deposit samples, which indicates that environmental magnetic technology may be an effective method for distinguishing source apportionment and monitoring river sediment pollution in urban areas. [ABSTRACT FROM AUTHOR]

In this study, samples of dustfall collected monthly or semi-monthly, during 1997-1999, at two representative sites (Kexueguan: KLD and Gaolanxan: GLX) in Lanzhou, a typical industrial city in northwestern China, have been examined using environmental magnetic measurements. A set of magnetic parameters of 50 dustfall samples were analysed. Results demonstrate that Lanzhou City is heavily polluted, with the main pollution sources being anthropogenic activities and natural dust. The former poses a threat to human health all the year, which is different from the general opinion that natural dust is the main source of pollution in summer. This study extended the application of environmental magnetic techniques and can be regarded as a progressive step in exploring urban pollution problems using environmental magnetic techniques. The results from the present study have an important implication on the design of future urban pollution control strategies in Lanzhou, and the method could be applied to other urban cities in the world. [ABSTRACT FROM AUTHOR]