天然有机质存在条件下的纳米颗粒与重金属协同行为研究

纳米颗粒与重金属元素相结合发生反应,可能产生一系列相互作用关系。这些作用过程是取决于多个环境条件共同作用的复杂过程,尤其是在土壤这种复杂的典型非均质环境介质中。这些作用关系可分为协同促进和拮抗抑制两大类关系。对于土壤中的重金属元素离子而言,纳米态粒子对其环境有效性究竟是协同促进还是拮抗抑制作用,关键取决于纳米粒子的表面修饰特性、二者间的界面反应以及反应后重金属元素的最终赋存状态这三个方面。协同促进或拮抗抑制作用与否则最终决定了这些污染重金属离子的生物可利用性和生态毒性响应。本文对近年来纳米颗粒-重金属共环境行为国内外研究现状进行综述讨论。纳米-重金属界面吸附解吸和土壤中迁移持留过程研究涉及多个热力学、动力学解析方法,科学家结合静态批实验和动态迁移实验等实验室模拟手段,对纳米颗粒、重金属离子、有机质三因子在土壤介质中的相互作用影响和共行为方式展开深入探讨。在重金属离子-纳米颗粒表面吸附机制、赋存形态以及重金属纳米吸附态土壤迁移固定机制研究中,多种定性表征方法的综合应用,如透射电镜(TEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FTIR)、X射线吸收近边结构光谱/扩展X射线吸收精细结构光谱(XANES/EXAFS)等方法相结合,被公认是揭示这一系列过程机制的重要技术手段。针对不同土壤环境中有机质存在条件,正确评价纳米态物质对重金属的迁移性及生物可利用性的影响作用,将为纳米环境效应评估和纳米修复技术等相关应用提供重要的数据支持和机理依据。

Review on the Co-behavior of Nanoparticles and Heavy Metals in the Presence of Natural Organic Matter in the Natural Environment

Due to the wide presence of nanoparticles (NPs) and heavy metals (HMs) in the environment, especially in porous media like soil, their fate and transport behaviors and hence the environmental impacts will greatly depend on their speciation, the impacts of natural organic matter (NOM) and how they interact with each other. Most correlative studies select typical NPs, HMs and NOM as the model subjects and conduct a series of adsorption-desorption batch experiments and NPs-HMs co-transport experiments in porous media to systematically study the NPs-HMs co-behaviors. Both thermodynamic and kinetics models have been applied to describe the interfacial reaction and transport/retention data obtained from experiments. The parameters were well compared, simulated and interpreted in order to achieve a complete picture of the effects of NOM on the fate of NPs-HMs. To reveal the mechanisms of NPs surface adsorption and the metal ions immobilization by NPs between soil grains, a big series of characterization analysis methods can be employed, such as Transmission Electron Microscopy (TEM), X-ray Diffractomer (XRD), X-ray Photoelectron Spectrometer (XPS), Fourier Transform Infrared Spectrometry (FTIR) and X-ray Absorption Near Edge Structure Spectrometry/Extended X-ray Absorption Fine Structure Spectrometry(XANES/EXAFS). Some of these methods working together are believed as a very effective and efficient approach in modern study. Understanding how the NPs impact on the leachability and bioavailability of heavy metals in subsurface porous media is of fundamental importance to the accurate assessment of environmental and ecological impacts of NPs. The results also have great significance to well comprehend the mechanisms of nano soil remediation.