Lithological and anthropogenic factors affecting magnetic properties of calcareous soils in Zanjan

Soils magnetic properties reflect different effects of soil mineralogy. Soil minerals originate from natural (lithogenic and pedogenic) or anthropogenic (secondary ferromagnetic minerals) origins or both sources. The present study was carried out to evaluate the effect of anthropogenic activities and parent materials on magnetic behaviours in cancerous soils of Zanjan. A total number of 241 soil samples (0-10 cm depth) were taken from an area of 2000 km2 having different land uses and parent materials and analysed in the lab. Mean magnetic susceptibility (MS) of the soil samples was 377.9 10-8m3kg-1. The highest MS was obtained for urban soils (mean of 467.13 10-8m3kg-1). Industrial activities particularly the Pb and Zn melting factories and traffic and fossil fuels appear to be among the important sources of anthropogenic ferromagnetic particles. The contribution of lithogenic sources (parent materials) to MS in soils derived from igneous rocks is very high. The MS in such soils is not positively correlated with pedogenic development. Soils developed on sedimentary rocks have relatively low MS (42 to 158 10-8m3kg-1). Higher MS in soils with sedimentary parent materials seems to be mainly due to pedogenic and in situ formation of ferromagnetic materials.