Applications of microelectrodes and scanning electrochemical microscopy (SECM) to complex environmental interfaces

During this research, microelectrodes were employed as sensors and scanning electrochemical microscopy (SECM) probes to further understand two complex environmental interfaces: the sea surface microlayer (SML), and the iron-groundwater interface at permeable reactive barriers (PRBs). The water-air and water-SML interfaces were investigated through the oxidation current of a model redox pair at a Pt submarine microdisc. Chronoamperometry and cyclic voltammetry allowed us to determine the concentration and diffusion coefficients of the redox species at different tip-substrate distances with respect to each interface. The approach curves recorded revealed information regarding the stability of the water-air interface over time and its susceptibility to the acquisition mode, size of the meniscus and the ratio of glass/microwire of the tip (RG). The iron-groundwater interface was investigated in terms of the corrosion activity and ReO₄^- uptake from groundwater of iron from different sources and particle sizes. The relationship between the corrosion of iron and the uptake of ReO₄^- was investigated using supplementary techniques like laser ablation inductively coupled plasma mass spectrometry (ICP-MS), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). The results obtained represented a basis to understand the TcO₄^- uptake from groundwater at PRBs.