Quantifying the structure of very small (<25 nm) natural aquatic colloids

天然水生胶体被定义为尺寸在1纳米到1微米（10^-9 / 10^-6米）之间的固相材料，因此非常小，并且具有非常大的表面积。它们在水生（和陆生）环境中无处不在，由不同类型的物质组成，如有机（腐殖质和多糖）、无机（金属氧化物）和生物（病毒和细菌），这些相以复杂的方式混合在一起。我们知道胶体在化学上和物理上结合微量污染物，如金属，而这些金属，如汞、镉、镍等，可能是有毒的。此外，我们知道这些胶体影响微量金属的命运和行为，并控制金属的运输和生物利用度。此外，已知非常小的部分（小于约25 nm）在许多环境条件下对金属结合非常重要，并在生物利用度中起决定性作用。尽管这些知识主要是定性的，而不是定量的，但在这个领域还有很多未知的地方。特别是，我们对“纳米胶体”（< 25nm）结构的认识很差，提高我们在这方面的知识基础对于进一步了解微量元素的化学、运输和生物利用度至关重要。该项目旨在通过验证流场-流分馏法（FlFFF）和原子力显微镜（AFM）相结合的方法来量化纳米胶体的形状及其渗透率（对溶质和溶剂分子），从而解决其中的一些不确定性。关于这些结构测量的信息可以包含在一个简单的比例中，可用于进一步的物种形成和生物利用度建模研究，这对于更好地理解纳米胶体在微量元素行为中的环境“功能”至关重要。这一领域的研究类似于上个世纪对生物大分子（如蛋白质和遗传物质）的结构-功能关系的研究。

Natural aquatic colloids are defined as solid phase material between the sizes of 1 nm and 1 um (10^-9 / 10^-6 m) in size and are thus extremely small and finely divided with very large surface areas. They are ubiquitous in the aquatic (and terrestrial) environment and composed of different types of material such as organic (humic substances and polysaccharides), inorganic (metal oxides) and biological (viruses and bacteria) and these phases are mixed together in complex ways. We know that colloids chemically and physically bind trace pollutants such as metals and that these metals such as mercury, cadmium, nickel etc., may be toxic. In addition, we know that these colloids affect trace metal fate and behaviour and control metal transport and bioavailability. Further, it is known that the very small fraction (less than approximately 25 nm) is very important in metal binding under many environmental conditions and plays a defining role in bioavailability. Despite this knowledge which is primarily qualitative rather quantitative, there is a great deal that remains unknown in this area. In particular, our knowledge of 'nano-colloidal' (< ca 25 nm) structure is poor and improving our knowledge base here is essential to further understanding trace element chemistry, transport and bioavailability. This project aims to address some of these uncertainties by validating a methodology coupling flow field-flow fractionation (FlFFF) and atomic force microscopy (AFM) to quantify the shape of nanocolloids and their permeability (to solute and solvent molecules). Information about these structural measures can be contained within a simple ratio, usable in further modelling studies on speciation and bioavailability are essential to better fundamental understanding of the environmental 'function' of nanocolloids in trace element behaviour. The area of investigation is analogous to research over the last century into the structure-function relationships of biological macromolecules such as proteins and genetic material.