Anthropogenic contribution of magnetic particulates in urban roadside dust

Environmental magnetism parameters have been optimized as qualitative proxy indicators of the distribution of anthropogenic particulates, heavy metals and/or organic materials. In the present study, we propose a quantitative magnetic proxy which is suitable for the monitoring of spatial and temporal pollution patterns in urban areas. A total of 1353 roadside dust samples were collected from Seoul, Korea for 13 months. Thermomagnetic data and intensive electron microscopy identified a predominance of carbon-bearing iron-oxides, indicating that anthropogenic particulates mostly originated from fossil fuel combustions. To quantify anthropogenic particulates, an apparent magnetic concentration [AMCFe3O4=observed saturation magnetization(Ms)/MsofFe3O4(=92.36Am2kg−1)] was calculated. AMCFe3O4AMCFe3O4 showed distinctive spatial and seasonal dependences: highest in industrial areas and lowest in park areas; and maximum in winter and minimum in summer. Seasonal mapping using AMCFe3O4AMCFe3O4 illustrated that industries in southwestern Seoul were the major pollution source. In addition, dominant westerly winds possibly transported pollutants along topographically lower areas in Seoul.