中文摘要：

湿地植物根表铁膜对包括重金属在内的物质迁移转化具有重要作用,其氧化铁组成研究备受重视,但利用环境磁学方法进行表征的研究还未见报道.本文对长江口潮滩植物芦苇根系及周边沉积物进行了磁学分析,并结合沉积物粒度、漫反射光谱等测试,对芦苇根表铁膜的磁性矿物组成进行了系统研究.结果表明,芦苇根表铁膜磁性矿物主要包括磁铁矿和赤铁矿.由于沉积物不同深度氧化还原环境的不同,铁膜磁性矿物组成存在垂向差异.研究柱样24 cm深度以上,由于相对氧化的环境,铁膜磁性矿物除磁铁矿外,还有较多的赤铁矿贡献;24 cm深度以下,因根系处于相对还原的环境,磁性矿物以磁铁矿为主.与沉积物相比,24 cm以上深度铁膜中亚铁磁性矿物含量较低,24 cm深度以下则相反,反映铁膜和沉积物磁性矿物来源不同.本项研究表明,磁性测量方法有助于认识湿地植物根表铁膜的矿物组成,对湿地生物地球化学过程研究具有重要价值.

英文摘要：

Iron plaque on the wetland plant roots plays an important role in the elemental cycle（ e. g.,heavy metals）,and has therefore received wide attention regarding its iron oxide composition. However,characterization of iron plaque composition using the method of environmental magnetism,as far as we know,has not been reported. In the present study,analyses of magnetic properties,particle size and diffuse reflectance spectrophotometry were carried out on a core from the tidal flat of Chongming Island,Yangtze Estuary. The purpose was to investigate the magnetic mineralogy of iron plaque on roots of Phragmites australis as well as the surrounding sediments. It is indicated that both magnetite and hematite are present in the iron plaque. The magnetic mineralogy shows vertical variations due to change in redox conditions. Hematite is more abundant in iron plaque in the upper 24 cm of the core due to relatively oxidizing environment,whereas magnetite dominates magnetic properties in the layer below 24 cm due to relatively reducing environment. In comparison to the surrounding sediments,ferrimagnetic mineral content is lower in the layer above 24 cm depth while higher below 24 cm depth. It is indicated that magnetic minerals in iron plaque have different source from those in the sediments. Our results demonstrate that magnetic measurement can be used to characterize the mineral composition of the iron plaque on the roots of wetland plants,which will contribute to the study of biogeochemical process in the wetland system.