Magnetic monitoring of topsoil and street dust in Xinyang (China) and their environmental implications.

The magnetic measurement is an effective tool to identify the source of pollutants and diagnose the urban pollution. In this study, 132 group samples (that topsoil and street dust were sampled at the same location is regarded as a group) were collected from Xinyang, central eastern China. In addition, the background samples (19 topsoils under woodland around the outskirts) were also sampled. Herein, the aim was to investigate and compare the magnetic characteristics of both topsoil and street dust, and further to discuss the source and environmental implications using magnetic and diffuse reflection spectrum methods. The following points are highlighted: (1) the primary magnetic carrier of both materials was magnetite and that of the background sample were magnetite and maghemite. Furthermore, the ferrimagnetic mineral concentration and magnetic domain follow the order: street dust > topsoil > background sample. (2) The source of both materials was mainly from anthropogenic activities (e.g. industrial and traffic vehicles). The difference between them was the contribution related to natural sources (e.g. parent materials), which was negligible in street dust, and played a secondary role in topsoil. (3) Both materials showed that areas with a higher intensity of anthropogenic activities had higher pollution level, whereas areas with a lower anthropogenic intensity had lower pollution level.