Spatiotemporal Variation Of Magnetic Properties Of Dustfall In And Around The Industrial Cities Of Northwest China And Their Environmental Significance

The Northwest China is located in the inland hinterland,with a dry climate and frequent dust activities,its climate and environmental changes are highly unstable.As the industrial activities and urban development,environmental issues of industrial cities are increasingly prominent,seriously affecting the eco-environmental protection of the and the coordinated development of economy,society and environment in arid and semi-arid areas.In the context of long-term natural climate change,clarifying the sources of atmospheric environmental pollution are prerequisite for the regional sustainable development of ecology and economy in the Northwest China.Atmospheric particulate matter provides a potential carrier for us to explore these important scientific issues,as it contains key information about regional environmental changes and urban pollution.Based on the close relationship between the magnetic particles and heavy metal elements,environmental magnetism provides an important approach for us to explore the environmental pollution information contained in atmospheric particulate matter and to quality and semi quantify the level of environmental pollution.Analyze the spatiotemporal variation of the magnetic properties of dustfall in and around the industrial city of Northwest China,is not only beneficial for in-depth understanding of the level and spatiotemporal difference of urban pollution in the Northwest China,as well as the response of magnetic parameters to the regional environment,but also conducive to provides an important scientific reference for pollution prevention and control in the Northwest China.We monthly collected 462 dustfall samples from 8 sites in the three industrial cities,Lanzhou,Baiyin and Yulin of the Northwest China.In this study,using environmental magnetic methods,the magnetic properties and spatiotemporal differences of dustfall in the study area were analyzed,and the influence factor,potential sources and environmental significance of dustfall were further discussed.The preliminary conclusions are as follows:（1）The grain-size of magnetic minerals in the dustfall samples of the study area is relatively coarse,and is mainly composed of PSD and MD particles,with a small amount of SP particles;the type of magnetic minerals is mainly magnetite,containing a small amount of hematite;the concentration of magnetic minerals in the dustfall samples is higher than that of nearby surface soil,loess,or clean soil at different levels.（2）The concentration and grain-size of magnetic minerals of dustfall have significant spatiotemporal differences.The concentration of magnetic minerals is the highest in winter and the lowest in summer.The concentration and grain-size of magnetic minerals in different cities are as follows:Lanzhou>Baiyin>Yulin;and in different regions are as follows:urban area>urban new district>rural area.（3）The dustfall in the study area is greatly affected by nearby source pollution,and the pollutants in urban areas are mainly from industrial production and fuel combustion,especially coal-fired;the pollutants in urban new district are mainly from vehicle exhaust emissions,dust,and biomass combustion in road traffic;the pollutants in rural areas are mainly from construction/renovation and biomass burning.（4）During the"13th Five Year Plan of China"period,the concentration of magnetic minerals in dustfall samples from Baiyin and Yulin urban area had decreased at different levels,which indicates that the achievement of the environment and air improvement are remarkable after conducting a series of control measurements including closed coal mining,closure of polluting enterprises,and so on,which is worthy of learning from the other industrial cities.Environmental pollution in urban new district has shown an increased trend,and has also increased for a short-term in rural areas due to the impact of construction/renovation during the new rural construction period.The research results suggest that environmental pollution issues cannot be ignored in the development and utilization of urban roads and rural construction/renovation processes.（5）Magnetic parameters such asX_lf（11）X_ARM and SIRM,which mainly reflect the concentration of magnetic minerals,can be used as environmental indicators in the study area and can effectively indicate the atmospheric particle pollution.Environmental magnetism can provide valuable information for urban particulate pollution monitoring and environmental governance,and quickly assessing the level of urban particulate pollution.