武昌地区街道尘埃磁学特征及其对环境污染的指示意义

摘要

In order to explore the relationships between magnetic properties and environmental pollutions, street dust samples from four functional districts (Qingshan, Hongshan, scenic spot of East Lake, development zone of East Lake) of Wuchang region were collected, and their magnetic parameters including magnetic susceptibility, frequency dependent susceptibility, isothermal remanent magnetization, demagnetization coefficient and magnetic hysteresis were determined. The results demonstrate that magnetic remanence carriers are dominantly soft magnetic minerals which belong to ferrimagnetic minerals and magnetite particles in the samples present characteristic of low values of coercivity. Distribution patterns of saturation isothermal remanent magnetization (SIRM) are influenced by industrial activities, vehicle flow, and road conditions. SIRM data are good indicators for environmental pollutions in the chosen four districts; heavy contamination in the Qingshan industrial district and moderate contamination in the other three districts. In addition, distribution patterns of hard isothermal remanent magnetization (HIRM) indicate the special source of antiferromagnetic minerals originating from road traffic. Due to the excessive flow of freight cars and heavy vehicles, development zone of East Lake and Qingshan industrial districts posses higher HIRM values than Hongshan and scenic spot of East Lake. In total, street dust samples from Wuchang region show a higher concentration of magnetic minerals compared with other domestic metropolis such as Lanzhou, Xi'an, Nanjing and Xuzhou, indicating the urban environment need to be further protected and improved.%对在武昌地区4个功能区域(青山、洪山、东湖风景区、东湖开发区)主要交通街道收集的尘埃样品进行详细的环境磁学测量,包括质量磁化率、频率磁化率、等温剩磁退磁系数以及典型样品的磁滞回线参数等.研究结果表明:尘埃样品中剩磁载体均以亚铁磁性矿物为主,样品中的磁性颗粒呈现低矫顽力的磁铁矿特征,软磁性的磁性矿物是样品剩余磁性的主要载体.尘埃样品x、SIRM的区域分布特征受区域周围工业、车流量及道路状况等多种环境因素的影响,在4个功能区域中存在明显的磁性差异:青山工业区污染较重,东湖开发区、洪山、东湖风景区次之；硬剩磁(H IRM)的分布可能指示了道路交通来源的磁颗粒特征,东湖开发区和青山工业区由于行驶的货车和重型车辆较多,表现出硬剩磁量值较高.与其他城市(兰州、西安、南京、徐州等)相比,整个武昌地区街道尘埃样品的磁性含量仍较高,说明在城市环境方面还有待于进一步改善和保护.