Frequency Dependent Magnetic Susceptibility in Topsoil of Bandung City, Indonesia

Soil contains lithogenic components as well as anthropogenic components including combustion residues from traffic activities. The high traffic activities in major cities such as Bandung have caused the air pollution level to increase significantly. These activities might also produce significant combustion residues that accumulate, among others, in the topsoils. Compared with lithogenic components in topsoil, the anthropogenic combustion residues might have different magnetic signatures that could be detected by magnetic measurements. In this study, 38 topsoil samples from 19 roadside sampling points in Bandung City were collected and magnetically analysed to map the magnetic signatures due to traffic activities. The samples were measured for magnetic susceptibility using Bartington MS2B Susceptibility Meter and hysteresis parameter analysed from Vibrating Sample Magnetometer (VSM). The results show that the values of mass-specific magnetic susceptibility (χLF) vary from 391.20 to 1835.20×10-8 m3/kg with the average value of 1012.16 × 10-8 m3/kg while the values of frequency dependent susceptibility (χFD%) vary from 0.54% to 4.48% with the average value of 1.9%. The relatively high value of magnetic susceptibility indicates higher concentration of magnetic minerals compared to that of pristine topsoil around Bandung. This is in agreement with similar studies on roadside topsoil elsewhere. The poor correlation between mass-specific magnetic susceptibility and frequency dependent magnetic susceptibility infers that the magnetic minerals are predominantly non superparamagnetic. This finding is supported by magnetic hysteresis parameters showing that the predominant grains are likely to be pseudo-single domain (PSD) if magnetite is assumed to be the predominant magnetic mineral. Similar studies in German and China reported that the predominant magnetic mineral is mixture of single domain to multi domain magnetite.

The Potential Utilizing of Critical Element from Coal and Combustion Residues

Strategically critical elements are becoming significant for the rising demand of emerging energy-efficient technologies and high-tech applications. These critical elements are mostly geologically dispersed, and mainly recovered from recycled materials. Coal with high concentrations of critical elements is supposed to stable alternative sources. The abundances of critical elements in coal varies widely among different deposits and regions. The high concentrations of critical elements are found in many Chinese and Russian coal ores. The global mining potential ratio (MPR) is applied and suggests scandium, hafnium, cesium, yttrium, germanium, gallium, thallium, strontium and rare-earth elements could be potential recovery from coal. A number of benefits are expected with the extraction of critical elements during coal utilization.