关键词: 大气降尘； , 环境磁学； , 空气污染指数； , 乌鲁木齐

Abstract: Magnetic susceptibility has been ascertained to be a valid method in identifying pollution source and sedimentary process of fine-grained PMs (＜10 μm) in the air. Thereafter，magnetism has been collectively used to monitor air pollution. In this paper a set of environmental magnetic parameters was measured on the monthly collected dustfall samples，which were collected from 2012 to 2013 at campus of Xinjiang Normal University，Urumqi，Xinjiang，China，and compared air quality index changes since the city implemented “coal to gas” from 2011-2012. All the samples were subjected to measurement of low-field magnetic susceptibility using a Bartington MS2, such as magnetic susceptibility (χ)，frequency dependent susceptibility (χ_fd%). Samples were also subjected to magnetic measurement of isothermal remanent magnetization （IRM），IRM acquired in a field of 1 T was regarded as saturation IRM （SIRM）. Magnetic parameters have repeatedly been used to identify magnetic composition，grain size and concentration of ferrimagnetism in atmospheric air particulate matter（PM） samples. The results from the study were summarized as follows：the magnetic susceptibility (χ) and frequency dependent susceptibility （χ_fd%） reveal that the dominant magnetic minerals are ferromagnetic mineral and the lower content of super-paramagnetic （SP），which were characterized by high (average 508.77×10^-8 m³/kg)，frequency dependent susceptibility （average 2.17%）. χ，SIRM and SOFT changed obviously in season，and whose values in summer is lower than that in winter. Magnetic susceptibility values of dustfall have significantly positive correlation with Soft [IRM] and saturation isothermal remanent magnetization （SIRM），suggesting that the ferromagnetic minerals are the main magnetic carriers. Correlations between magnetic susceptibility and temporal variations of concentration of air pollutants indicate that the level of air pollution degree was reduced from 2011 to 2012. the coal burning for heating is a prominent contribution to the high magnetic mineral concentrations in winter. Comparing to traditional chemical methods，such as AAS，ICP-MS and so on，magnetic method is a simple，rapid，exact，low-cost and non-destructive method of monitoring pollution and has been widely applying in domestic and international studies. It has been shown that air pollution of cities comes mainly from the behavior of human beings，such as motor vehicles，industries exhaust gases，water and fly-ashes and living rubbishes. Obviously，systemic magnetic studies on atmospheric various pollution sources are helpful to better tracing the source and distribution characteristics of atmospheric pollution and then improving environmental qualities of cities. So it is believed that a synthetic rock magnetic study is an effective method for determining concentration and then it should be a rapid and feasible technique for monitoring atmospheric pollution.

Key words: atmospheric dust, environmental magnetism, air pollution index, Urumqi City