微尺度重金属土壤化学研究进展与展望

土壤重金属污染是我国面临的重要生态环境问题,有效管控与修复重金属污染土壤有必要弄清重金属与土壤固相组分的作用机制。土壤组成多样、结构复杂、空间异质,加之土壤团聚体粒径大小不一,形成微观结构和表面性质各异的土壤微域,控制着重金属的形态转化及生物有效性。因此,深入认识微尺度的重金属土壤化学对于预测和管控土壤重金属环境化学行为至关重要。同步辐射X射线微探针(Microprobe)、X射线扫描透射显微术(STXM)及纳米二次离子质谱技术(Nano SIMS)等技术具有微纳米级空间分辨率,为在环境意义尺度上探究微尺度重金属土壤化学提供了独特的支撑平台。本文从环境土壤化学发展历程及当前发展瓶颈、现代微尺度分析技术及其在微尺度重金属土壤化学中的应用进展等方面综述,并对该领域未来的发展进行了展望。

Microscale Soil Chemistry of Heavy Metals: Research Process and Perspective

Soil contamination by heavy metals (HMs) is an important eco-environmental problem in China. It is essential to understand the mechanisms of HMs interacting with solid-phased fractions of soil for effective control and remediation of HMs polluted soils. Due to the complexity and heterogeneity of soil as well as the varied sizes of soil particles ranging from millimeter to nanometer, microsites with different micro-structures and surface properties control the speciation, transformation and bioavailability of HMs. Therefore, it is of great importance to deeply understand the microscale interaction mechanisms of HMs within soil microsites in order to effectively predict and control environmental behaviors of HMs in soils. Synchrotron-based microprobe and scanning transmission X-ray microscopy (STXM), and nano-scale secondary ion mass spectrometry (NanoSIMS), with micro- and nano- scale spatial resolutions, provide a unique platform to investigate the microscale interaction mechanisms of HMs within soil microsites at environmental meaningful spatial scales. This review first gives a brief overview of the birth and development of environmental soil chemistry (ESC) of HMs, points out the bottleneck of the current development of ESC due to inherent complexity and heterogeneity of the soil, and summarizes the aforementioned three advanced techniques and their application in the investigation of microscale soil chemistry of HMs, and finally gives a perspective on future development in this field.