Identification of Anthropogenic Materials in Topsoil From the Urban Area of Banjarmasin, Indonesia Using Geochemical and Rock Magnetic Properties

The city of Banjarmasin is located in a peatland and has a tropical climate. Peat areas have their own uniqueness, plus this city is traversed by many tributaries and is very rarely researched, especially in relation to the use of rock magnetism. This research is important because it investigates the feasibility of using magnetic techniques to identify anthropogenic materials produced by human activities, using rock magnetism, geochemical analysis, and pollution index calculations. When compared with the background, the magnetic signal of the urban topsoil is greatly enhanced with a magnetic susceptibility (χLF) of (0.22–13.60) × 10-6 m3/kg. However, the urban topsoil contains only a small number of pedogenic superparamagnetic (SP) grains, as indicated by the low average value of χFD% (< 2%). The geochemical properties of the magnetic fraction in urban topsoil differ significantly from those of topsoil found in peatland generally. This further demonstrates that the magnetic minerals accumulating in the urban topsoil not only originate from pedogenic processes but also from parent soil materials from the surrounding area of the research. In this instance, the research area's surface soil serves as embankment land for the construction of settlements, roads, and other infrastructures. Significant correlational magnetic techniques can screen topsoil pollution in this area, as evidenced by the significant correlation between χLF with V, Mn, Fe, and Ni, as well as χHF with Fe. The Igeo pollution index indicates a slight-to-high level of pollution in Cr, Ni, Cu, and Zn.