Use of environmental magnetism to monitor pollution in the river sediment of an urban area

With the advantages of fast,sensitive,inexpensive and nondestructive measurement,environmental magnetism analysis has been used as a preliminary method to study pollution effects before starting time-consuming and expensive chemical methods.In this study,sediments from a representative river,the Sier River,were selected for measurement of particle size,elemental composition and magnetic properties with the purpose of exploring the sediment magnetism response to different nearby landuses.The results indicate that river sediments collected in the Green district and residential areas are characterised by low concentrations of magnetic minerals and a small amount of maghaemite,while those collected in the commercial district and industrial areas are characterised by high magnetic mineral content and low maghaemite.The origin of maghaemite can be used to indicate the river pollution level,but mineral grain sizes are not an effective indicator of pollution intensity in an urban area.Comparison of the sediment magnetic properties with the degree of pollution reveals that,although the degree of pollution is the highest in the commercial district,the highest magnetic susceptibility was measured in sediments from the industrial area,which implies that although the magnetic susceptibility increased significantly when the degree of element enrichment was high,the increase is nonlinear in different types of sediments.The study indicates that various magnetic parameters should be used and the influence of source should be minimized when monitoring the pollution using environmental magnetism analysis.