关键词: 磁性参数, 空间变化, 土壤污染, 乌鲁木齐市

Abstract: With population overpressure and rapid urbanization，various pollutants are continual emitted to the environment system and cause a potential threat to the system of the urban environment. Urban soils are the “recipients” of large amounts of pollutants from a variety of sources, such as iron and steel works，cement works.  Public boilers and road traffic also contribute to contamination by anthropogenic ferromagnetic minerals. The great number of industrial and human activities which originate polluting waste containing heavy metals makes necessary to develop an alternative methodology that allows us to monitor the pollution and identify the sources and extent of contaminants，in a simple and economical way. Due to the presence of magnetic particles in pollutants，during last decade，the magnetic method has been proposed as an alternative method for monitoring of anthropogenic pollution. A growing number of studies using the techniques of magnetism of rocks have been applied to environmental problems，thus creating a new branch of research commonly called “environmental magnetism”. This methodology is fast，economic and can be applied in various research fields. Recent studies have demonstrated the advantages and the potential of the environmental magnetism methods as valuable aids in the detection and delimitation of areas affected by pollution. These methods are based on the assumption that industrial and traffic processes，which use fossil fuel combustion，release into the atmosphere particulate matter （fly ash） containing a significant proportion of magnetic minerals. The aim of this study was to analyze the properties of magnetic parameters of concentration，composition and particle size for the urban topsoils，the spatial distribution under different circumstances of land use and to document initially the environmental implications of magnetic properties. In this paper，the 45 topsoil samples （0-10 cm） were collected from the different land use types in built-up areas and suburbs of Urumqi City，Xinjiang，China. This study concludes that the value of magnetic concentration parameters is average level and the mass magnetic susceptibility in built-up area is generally greater than that in the suburban. From the spatial distribution of magnetic concentration parameters，they are divided into high，medium and low areas. The high value area is located in the territory of heavy industry area. The medium value area is situated in area around high value area and the values of unused land and agricultural land in the north and the other three directions are the lowest. Magnetic mineralogy parameters suggest that samples are dominated by ferrimagnetic minerals corresponding to magnetite-like minerals，but contain a small amount of anti-ferromagnetic material. Magnetic grain parameter like percentage of frequency dependent magnetic susceptibility showed that the soils in built-up area dominated with coarser MD ferromagnetic grain. The suburban is composited by coarser grain and super-paramagnetic magnetic minerals. It is possibly produced by anthropogenic activity. Finally，the above results reflect that the values of magnetic properties in build-up area are relative higher than that in suburban less influenced by human factors．The phenomenon can come from the industrial and mining enterprises emissions dust，vehicle exhaust and commercial activities and other human activities. In addition，it is worth noting that the magnetic parameters value of arable land and unused land soil surrounding industrial area are higher. These may be caused by the fly ash from northwest steel works and eastern thermal power plant.

Key words: magnetic parameters, spatial variability, soil pollution, Urumqi City