Magnetic analysis of heavy metal pollution in Rengang River sediments, Nantong, China

To explore the feasibility of using magnetic properties as indicators for heavy metal pollution, magnetic properties, particle size, heavy metal concentrations and total organic carbon contents were investigated for a sediment core from the Rengang River in Nantong City, Jiangsu Province. The results indicate that Pb, Zn, Cu and Ni contents are enriched in the top 12 cm layer, which are higher than the soil background values of Jiangsu Province. After normalizing the effect of particle size, heavy metal contents are still higher in the upper part than the background values. It is found that ferrimagnetic mineral dominates the magnetic properties in the sediment core. Magnetic mineral contents are higher in the upper 12 cm of the sediments than those below due to anthropogenic input. Magnetic susceptibility (χ), saturation isothermal remanent magnetization (SIRM) and susceptibility of anhysteretic remanent magnetization (χ _ARM) display significant positive correlations with Pb, Zn, Cu and Ni concentrations(r≥0.74, p<0.01, n=54), suggesting that magnetic parameters can be potentially used as qualitative proxies of heavy metal pollution in the river sediments. However, the changes in magnetic mineral contents are not consistently synchronous with heavy metal concentrations in the upper 12 cm of the sediments, due to the effects of their sources and diagenesis. Therefore, it should be cautious to examine heavy mental contents quantitatively using these magnetic parameters.