Magnetic properties and heavy metal pollution in sediments of Yiwu River, Jinhua, China

In order to explore the feasibility of using magnetic properties as indicators for heavy metal pollution, magnetic, granulometric and geochemical analyses were conducted on a floodplain short core from Yiwu River in Jinhua City, Zhejiang Province, China. The results indicate that ferrimagnetic mineral dominates magnetic properties of the core. Particle size and early diagenesis influence the down-core changes in magnetic properties. Except the bottom layer, contents and enrichment factors of Cr, Ni, Cu, Zn, Cd and Pb show upward increasing trend due to anthropogenic input in the upper part of the core. It is found that variations of magnetic properties show similar patterns as those of heavy metals and their enrichment factors. In particular, magnetic susceptibility (χ), frequency magnetic susceptibility (χ_fd%) and hard remanent magnetization (HIRM) show significant positive correlations with Cr, Cu, Zn, Cd and Pb contents. It is suggested that magnetic minerals may share a common source with heavy metals, or fine-grained magnetic minerals can absorb heavy metals. Therefore, magnetic parameters can be used as qualitative proxies of heavy metal pollution in sediments of the Yiwu River. However, due to the location of Yiwu River in an open river system, magnetic properties of sediments are influenced by a number of factors in addition to pollution input, which complicates the use of magnetic properties as quantitative indicators of heavy metal pollution.