DGT/DET与CID技术联用获取环境微界面元素异质性分布特征：进展与展望

环境中广泛存在的微界面是物质循环和能量交换的门户，显著影响元素(如S、Fe和P)的迁移转化过程与生态效应。而微界面元素分布具有高度的时空异质性，因此开发和应用原位且高分辨率的表征技术手段显得尤为必要。薄膜扩散梯度(DGT)和薄膜扩散平衡(DET)技术是研究微界面元素和化合物分布及其生化过程的利器。近30年的大量实验证据表明，DGT/DET通过扩散-吸附/平衡作用原位被动采样结合后续高分辨化学分析手段，比如一维/二维膜物理切割-化学仪器分析、激光剥蚀-电感耦合等离子体质谱(LA-ICP-MS)以及计算机/比色密度成像计量法(CID),可以获取元素的高分辨浓度分布和生物有效性信息以及多元素间耦合作用的动态过程。在上述3种后续分析方法中，CID手段是最为便捷、快速和廉价的，空间分辨率与LA-ICP-MS分析相当，纵横方向均可达几十至几百微米，推广应用潜力巨大。本文在对DGT/DET和CID技术概述的基础上，总结了技术联用的思路，并依据获取二维高分辨图像的步骤差异对技术联用的进展进行了分类介绍，一类是原位即时显色成像，比如以AgI为吸附膜的DGT与CID方法联用测定硫化物，另一类是预处理后显色...

The combination of DGT/DET and CID methods to capture heterogeneous distribution characteristics of elements across environmental micro-interfaces: Progresses and prospects

The widespread micro-interfaces in the environment are the gateways of matter cycling and energy exchange, significantly affecting the transfer processes and ecological effects of elements(such as S, Fe, and P). The distribution of elements at the micro-interfaces is highly heterogeneous both spatially and temporally. It is therefore necessary to develop and apply in-situ and high-resolution characterization techniques. Diffusive gradient in thin-films(DGT) and diffusive equilibrium in thin-films(DET) techniques are reliable tools for revealing the distribution patterns and biochemical processes of elements and chemicals at the micro-interfaces. Increasing experimental evidences in the last three decades show that the high-resolution concentration profiles and bioavailability information of elements and the dynamic process of coupling among multiple elements can be obtained through combination of DGT/DET passive sampling due to diffusion and binding/equilibrium with subsequent high-resolution chemical analysis methods, such as conventional chemical analysis after one-dimensional/two-dimensional gel cutting, laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS), and computer/colorimetric density imaging metrology(CID). Among the above three subsequent analysis methods, CID is the most convenient, rapid and cheap one. The spatial resolution of CID is comparable to that of LA-ICP-MS analysis, reaching tens to hundreds of microns at vertical and horizontal directions. Therefore, there is great potential for popularization and application of CID as a tool for quantification of chemical’s mass captured by DGT/DET. Based on an overview of DGT/DET and CID techniques, we summarized the general guidelines of technology combination, and introduced research and development progresses by category in accordance with the guidelines. In category one, color develops on the functionalized gel of DGT/DET instantaneously as in-situ sampling proceeds, where a typical case is sulfide determination by DGT passive sampling with a pale AgI binding gel and CID quantification of the black Ag;S products on the resulting gel. In category two, staining is needed after in-situ sampling to initiate colorimetric reaction on the resulting gel, such as determination of phosphate and chromate by DGT sampling with a zirconium oxide binding gel and CID analysis, and determination of ferrous and alkalinity by combining DET and CID methods. Finally, the development and application trends of technology combination of DGT/DET and CID are prospected.