The present study was designed to characterize the magnetic proxy for sewage-related pollution from river sediments. A suite of mineral magnetic analyses including low-field magnetic susceptibility, isothermal remanent magnetization (IRM) acquisition and demagnetization, back-field IRM treatment, and thermal demagnetization of composite IRMs are carried out for topsoil samples collected from river sediments in Daejeon, South Korea. A 350-m long in situ profile of magnetic susceptibility shows a background mean magnetic susceptibility of 22.4 ± 5.6 × 10⁻⁵ SI. The coercivity spectra display dual peaks of lower- and higher-coercivity fractions. The predominance of magnetic signal with maximum unblocking temperatures of 580 °C points to magnetite as the sole magnetic mineral. Hence the lower- and higher-coercivity fractions correspond to coarse-grained and fine-grained magnetite, respectively. Extraordinarily high magnetic susceptibility was observed from BTC02, near to the sewage discharge point. However, its mineral magnetic properties and particle morphologies are not different to those of other soil samples. Then, it is apparent that a high magnetic susceptibility simply reflects the high concentration of magnetites in BTC02. It is likely that a continuous discharge of heavy metal enriched water at the discharging point concentrated significant amount of magnetic particles. It is fortunate that anomalously high magnetic susceptibility (by implication heavy metal concentrations) diminished only several meters away from the discharge point. Perhaps, influences of anthropogenic magnetite were diluted as the high magnetic phases were washed away from the water cycles along the river. In practice, it can be proposed that a periodic replacement of soils near the sewage discharge point is efficient to reduce the heavy metal concentrations.

本研究旨在表征磁沉积物对河流沉积物与污水相关的污染的特征。对从韩国大田河道沉积物中收集的表层土壤样品进行了一系列矿物磁分析，包括低场磁化率，等温剩余磁化（IRM）采集和消磁，后场IRM处理以及复合IRM的热消磁。 。磁化率350 m长的原位剖面显示背景平均磁化率为22.4±5.6×10 ^-5SI。矫顽力谱显示较低和较高矫顽力分数的双峰。最高无阻塞温度为580°C的磁信号占主导地位，这表明磁铁矿是唯一的磁性矿物。因此，较低和较高矫顽力的分数分别对应于粗粒和细粒磁铁矿。从BTC02观察到污水排放点附近的磁化率异常高。但是，它的矿物磁性和颗粒形态与其他土壤样品没有什么不同。然后，很明显，高磁化率仅反映了BTC02中磁铁矿的高浓度。在排放点连续排放富含重金属的水可能会浓缩大量的磁性颗粒。幸运的是，异常高的磁化率（通过暗示重金属浓度）使离放电点只有几米的距离减小了。也许，随着高磁性相从沿河水循环中冲走，人为磁铁矿的影响被稀释了。实际上，可以提出在污水排放点附近定期更换土壤对于降低重金属浓度是有效的。