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 [ AMC Fe 3 O 4 = observed saturation magnetization ( M s ) / M s of Fe 3 O 4 ( = 92.36 Am 2 kg − 1 ) ] was calculated. AMC Fe 3 O 4 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 AMC Fe 3 O 4 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.