SUITMA 2005 Cairo - Magnetic properties as indicator of heavy metals pollution in urban soils
SUITMA 2005 Cairo
| This abstract is about one of the papers of the Methodology and classification theme of the SUITMA 2005 symposium. |
| S. G. Lu,i | S. Q. Bai,i |
| H. D. Shan.i |
- i - College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China.
Magnetic measurement has been increasingly used as a tool for detection of heavy metal contamination in soils, atmospheric dusts and lake sediments. In this study, 124 topsoil samples were collected from representative urban areas of Hangzhou city, Eastern China. Total content of Cr, Mn, Zn, Cu, Cd and Pb and magnetic parameters, including magnetic susceptibility (), anhysterestic remnant magnetization (ARM), isothermal remnant magnetization (IRM) were measured. The relationship of magnetic parameters and heavy metals content in soils was assessed on the basis of the correlation coefficients and the associated level of significance (p).
Magnetic susceptibility () of urban topsoil samples is 320.8x10-8 for industrial area, 178.8x10-8 for roadside, 100.5x10-8 for residential area, 83.9x10-8 for campus, 61.1x10-8m3kg-1 for public parks soil, respectively. ARM and SIRM are also found to increase in an order of industrial area>roadside>residentialcampus>public parks, indicating that magnetic components are associated with industrial activities, automobile exhaust, deposition of atmospheric particulate. The fd value of urban soils is in a range from 0.7 to 5.0%, which is lower than those found in the natural soils collected in the similar area. The fd values soils increased in the order of industrial (average 2.3%)>roadside (2.5%)>residential (3.3%)>campus (3.8%)>public parks (4.5%). Low value of fd suggests that magnetic property of the samples be contributed predominately by the coarse multidomain (MD) grains, instead of by the superparamagnetic (SP) particles. Total contents of Mn, Cu, Zn, Cd, and Pb in urban soils are significantly higher than the background level of this region. The averaged concentrations of Cu, Zn, Cd, and Pb were one to three folds of the mean values of China soils. The enrichment of magnetic particles and heavy metals in the topsoil is considerably obvious in industrial and roadside soils. Correlation coefficients (r) between total contents of Cu, Zn, Cd and Pb and magnetic concentration parameter show that significant correlation exists between the heavy metals content and , ARM, and SIRM. The coefficients of correlation were found to be high for Zn and Cd, medium for Pb and Cu, and low for Cr and Mn. The observed positive correlation suggests that the magnetic susceptibility increase with the toxic elements.
Coexistence of heavy metals and magnetic particles can explain the enrichment of heavy metals and magnetic particles in topsoil samples. This relationship could be due to that toxic elements are incorporated into lattice structure of the ferrimagnetics or are adsorbed onto surface of pre-present ferrimagnetics in the environments. Good linear correlation of the magnetic mineral concentration-related parameters with the concentration of Cu, Zn, Cd and Pb makes it possible to use magnetic technique as a simple, rapid, and non-destructive tool for the assessment of heavy metals contamination in urban soils.
