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S U M M A R YThis paper deals with the magnetic properties [magnetic susceptibility, saturation isothermal remanent magnetization (SIRM), magnetomineralogicl parameters], the contents of heavy metals (Fe, Mn, Cd, Cr, Cu, Pb and Zn) and their mutual relationship in the urban topsoils of Luoyang, China. Magnetic susceptibility measured on 215 urban topsoil samples ranged from 31 × 10 −8 to 1128 × 10 −8 m 3 kg −1 (average 215 × 10 −8 m 3 kg −1 ) and showed that high magnetic susceptibility values were obtained on topsoil samples from industrial areas (average 313 × 10 −8 m 3 kg −1 ) and roadside (236 × 10 −8 m 3 kg −1 ), whereas lower susceptibility values were observed in parks and green areas (123 × 10 −8 m 3 kg −1 ). The urban topsoils were enriched with Cd, Cr, Cu, Pb and Zn, with average contents of 1.71, 30.51, 85.40, 65.92 and 215.75 mg kg −1 , respectively. The heavy metals Cr, Cu, Pb and Zn show a statistically significant correlation with magnetic susceptibility and SIRM. The Tomlinson Pollution Load Index (PLI) also shows significant correlation with magnetic susceptibility and SIRM, indicating that the magnetic parameters can provide a proxy method for identifying the heavy metal pollution in urban topsoils. Rock magnetism and X-ray diffraction analyses revealed that the dominant magnetic mineral in the urban topsoils is anthropogenic pseudo-single domain (PSD)-multidomain (MD) magnetite. These magnetic particles are associated with the industrial activities, traffic exhaust and deposition of atmospheric particulate.

Concentration and distribution of heavy metals (Cd, Cu, Pb and Zn) in urban soils of Hangzhou, China, were measured based on different land uses. The contamination degree of heavy metals was assessed on the basis of pollution index (PI), integrated pollution index (IPI) and geoaccumulation index (I geo ). The 0.1 mol l -1 HCl extraction procedure and gastric juice simulation test (GJST) were used to evaluate the potential mobility and environmental risk of heavy metals in urban soils. The average concentration of Cd, Cu, Pb and Zn in urban soils was measured at 1.2 (with a range of 0.7-4.6), 52.0 (7.4-177.3), 88.2 (15.0-492.1) and 206.9 (19.3-1,249.2) mg kg -1 , respectively. The degree of contamination increased in the order of industrial area (IA) [ roadside (RS) [ residential and commercial areas (RC) [ public park and green areas (PG). The PIs for heavy metals indicated that there is a considerable Cd, Cu, Pb and Zn pollution, which originate from traffic and industrial activities. The IPI of these four metals ranged from 1.6 to 11.8 with a mean of 3.5, with the highest IPI in the industrial area. The assessment results of I geo also supported that urban soil were moderately contaminated with Cd and to a lesser extent also with Cu, Pb and Zn. The IP and I geo values reveal the pollution degree of heavy metal was the order of Cd [ Pb [ Zn & Cu. It was shown that mobility and bioavailability of the heavy metals in urban soils increased in the order of Cd [ Cu [ Zn & Pb. Owing to high mobility of Cd and Cu in the urban soils, further investigations are needed to understand their effect on the urban environment and human health. It is concluded that industrial activities and emissions from vehicles may be the major source of heavy metals in urban contamination. Results of this study present a rough guide about the distribution and potential environmental and health risk of heavy metals in the urban soils.

Abstract:Measurements of the magnetic properties and total contents of Cu, Cd, Pb and Fe in 30 automobile emission particulate samples indicated the presence of magnetic particles in them. The values of frequency dependent susceptibility (χ fd ) showed the absence of superparamagnetic (SP) grains in the samples. The IRM 20 mT (isothermal remanent magnetization at 20 mT) being linearly proportional to SIRM (saturation isothermal remanent magnetization) (R 2 =0.901), suggested that ferrimagnetic minerals were responsible for the magnetic properties of automobile emission particulates. The average contents of Cu, Cd, Pb and Fe in automobile emission particulates were 95.83, 22.14, 30.58 and 34727.31 mg/kg, respectively. Significant positive correlations exist between the magnetic parameters and the contents of Pb, Cu and Fe. The magnetic parameters of automobile emission particulates reflecting concentration of magnetic particles increased linearly with increase of Pb and Cu content, showed that the magnetic measurement could be used as a preliminary index for detection of Pb and Cu pollution.