Magnetic susceptibility of the dust of street in Xi’an and the implication on pollution

With the aim at investigating the distribution of pollution in Xi′an city, a systematical sampling of street dust was carried out. Rock magnetic measurement showed the street dust had a high magnetic susceptibility and low frequency dependent susceptibility. Their obviously negative correlation indicatd that the magnetic enhancement mainly attribute to the human activity. Thermomagnetic analysis indicated that the samples affected by electricity generation station were dominated by magnetite, while samples influenced by several sources had maghemite, hematite and little amount of pure iron as their dominant magnetic minerals. Statistical analysis exhibited a great positive correlation between the magnetic susceptibility and elements like Pb and Ba which attribute to the traffic, pollution and elements like Cu and Cr which were resulted by metallurgic industry. Pollution in Xi′an city mainly attribute to the traffic pollution and metallurgic industry, and magnetic susceptibility could be used to reflect the intensity of pollution. Besides, magnetic susceptibility displayed a different correlation with different element in different districts. And this may indicate that the human activity that caused magnetic enhancement was different in each district in the city.