The present study was designed to explore the possibility of roadside pollution screening using magnetic properties of topsoil samples in Daejeon, South Korea. Low-field magnetic susceptibility, frequency dependence of magnetic susceptibility, susceptibility of anhysteretic remanent magnetization, isothermal remanent magnetization (IRM) acquisition and demagnetization, back-field IRM treatment, and thermal demagnetization of composite IRM were determined for roadside topsoil samples. Magnetic susceptibility measured on 238 samples from the upper 5 cm of the topsoils ranged from 8.6 to 82.5 × 10^–5 SI with a mean of 28.3 ± 10.8 × 10^–5 SI. The proximal zone, 55 m wide area situated on either side of the main street, exhibited an enhancement of magnetic susceptibility. In areas distant from the main street, low magnetic susceptibility (< 50 × 10^–5 SI) was observed. The topsoil samples exhibited significant susceptibility contrasts, suggesting that two dimensional magnetic mapping was effective in identifying traffic-related pollution. A few magnetic hotspots with intensities of magnetic susceptibility near or over 50 × 10^–5 SI might reflect the difference in topographic elevation and surface morphology. Among various IRM-related parameters, remanence of coercivity was most significant statistically. In most samples, IRM component analysis provided dual coercivity components. Thermal demagnetization of composite IRM and morphological observation of magnetic separates suggest angular magnetite produced by vehicle non-exhaust emissions spherical magnetite derived from exhaust emission to be the dominant contributors to the magnetic signal. It is likely that lower- and higher-coercivity components represent the presence of coarse-grained angular magnetite and fine-grained spherical magnetite, respectively.

本研究旨在探索利用韩国大田表土样品的磁性来进行路边污染筛查的可能性。确定了路边表土样品的低场磁化率，磁化率的频率依赖性，迟滞剩磁的磁化率，等温剩磁（IRM）采集和消磁，后场IRM处理以及复合IRM的热退磁。在表土上部5 cm的238个样品上测得的磁化率范围为8.6至82.5×10 ^–5 SI，平均值为28.3±10.8×10 ^–5SI。位于主要街道两边的55 m宽的近端区域显示出磁化率的增强。在远离主要街道的区域，观察到磁化率低（<50×10 ^–5 SI）。表土样品显示出明显的磁化率对比，表明二维磁测图可有效识别与交通有关的污染。几个磁化强度接近或超过50×10 ^–5的磁热点SI可能反映了地形高程和表面形态的差异。在与IRM相关的各种参数中，矫顽力的剩留率在统计学上最为显着。在大多数样本中，IRM分量分析提供了双重矫顽力分量。复合材料IRM的热去磁和磁分离物的形态学观察表明，由车辆废气排放产生的角状磁铁矿是由废气排放产生的球形磁铁矿，是磁信号的主要贡献者。较低和较高矫顽力的成分可能分别表示存在粗粒角铁矿和细粒球形磁铁矿。