Trace elements, existing as various forms at different dimensional levels, play an important role in the functioning of life on earth. These element forms, from small to large in size, include free ions, ionic compounds, nanoparticles, macromolecular complexes and bulk materials (i.e., minerals). They exhibit different chemical activities and hence profoundly determine their different transport, transformation, biological function and fate in environmental and biological systems. Recently, it is realized that nanoparticles and macromolecular complexes are the central of element forms, playing the dual roles of sources and sinks for ionic metals and bulk metals in various systems. In this paper, we revisited the notion of element forms from a more integrated perspective instead of any specific forms, reviewed the recent development of speciation methods and discussed the potential trends in technique improvement for analysis of various element forms at different dimensional levels in the future.

痕量元素以不同形式存在于不同维度级别，在地球生命的功能中起着重要作用。这些元素形式，从小到大，包括自由离子，离子化合物，纳米颗粒，高分子复合物和块状材料（即矿物质）。它们表现出不同的化学活性，因此深刻地决定了它们在环境和生物系统中的运输，转化，生物学功能和命运。最近，人们认识到纳米粒子和大分子复合物是元素形式的中心，在各种系统中扮演着离子金属和块状金属的源和汇的双重角色。在本文中，我们从更综合的角度重新审视了元素形式的概念，而不是任何特定形式，