| Mineral magnetic measurements allow the quick and non-destructive characterization of environmental materials in order to act as a proxy for heavy metal concentrations in solid deposits。Recently, magnetic measurements have been used to outline areas with increased loading of toxic metals, which are easily detectable, can carry toxic metals of anthropic origin. However, physical background of this relationship is not comprehended yet. Ninety-seven street dust samples were collected in a sampling period about one week around Donghu Lake, Wuhan city. The aims of our study are to get the distribution and concentration of contaminants in street dust and trace the sources of contamination in dusts along roads by using magnetic proxies. In order to compare the variations of the magnetic properties of the street dust samples, road around Donghu was divided to four segments. From the Donghu hospital of Wuhan city to Moshan is eastern segment (DHE), and Moshan to Liyuan square is northern segment (DHN), and Liyuan square to Zhongnan hospital is western segment (DHW), and Zhongnan hospital to Donghu hospital of Wuhan is the southern segment (DHS). Magnetic measurements and chemical studies were carried out on the samples. Among the magnetic parameters, low frequency magnetic susceptibilityχLF, high frequency magnetic susceptibilityχHF, frequency-dependent susceptibility χFD, natural remanent magnetization NRM, anhysteretic remanent magnetization ARM, isothermal remanent magnetization IRM, saturation isothermal remanent magnetization SIRM, temperature dependence of magnetic susceptibility(χ-T Curves)；hysteretic loops (include hysteretic parameters coercivity of remanence Hcr, coercivity Hc, saturation remanent magnetization Mrs, saturation magnetization Ms) and some ratios of them ARM/χLF, SIRM/χLF, SIRM /ARM, Soft, Hard, Soft％, Hard％, F300％ were studied. The chemical elements mainly are the concentration of 11 kinds of heavy metals (Fe, Zn, V, Ti, Pb, Ni, Mn, Cr, Cu, Co, Ba), and the Tomlinson pollution load index PLI was calculated。The magnetic measurements indicate that the dominant magnetic components are stable single domain and pseudo single domain ferrimagnetic minerals and that superparamagnetic and antiferrimagnetic mineral are present in small magnetic concentrations. A magnetite-like phase was found to be responsible for the enhancement of the magnetic signal in street dust. In addition, there is a second magnetic phase (may be sulphite of iron) in most sample except some samples of western segment which has not been identified. The distribution of the χLF, SIRM and ARM values represents the highest magnetic minerals concentration of the northern segment and the differences between site to site.The chemical analysis results show that except Zn, Cu and Ba the concentration of all other heavy metals is highest of dust samples in the northern segment. However the concentration of Bais highest in the samples of the western segment. The Zn and Cu have little difference in every segment. So the northern segment is the heavist polluted area. Correlation analysis, factor analysis and cluster analysis were applied to investigate associations between element concentrations. The results suggest mixed contributions of heavy metals from the fly-ash of coal combustion and soil and vehicle pollution, probably mainly fly-ash of coal combustion. Among the 11 elements Fe, Cu, V, Ni, Cr, Mn, Co mainly are from fly-ash; Zn and Ti in fly-ash and soil; Ba in soil and vehicle pollution.The correlation analysis between magnetic parameters and element contents show that the parameters which mainly reflect the concentration of the magnetic minerals (χLF, SIRM and ARM) have close association with Fe, Cu, V, Ni, Cr, Mn, Co and PLI but have no correlation with Zn and Ti, and have negative correlation with Ba. So we can infer that the magnetic minerals in street dusts mainly came from fly-ash. These results suggest a possible approach for source identification of magnetic material in pollution studies and th...
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