Selective and simultaneous high resolution 2-D imaging of As^III, Cr^III and Sb^III and dissolved oxygen by developing a...

A new diffusive gradients in thin films technique (HR-MPTS DGT) with mercapto-functionalized attapulgite in a binding gel was developed for simultaneous two-dimensional (2-D) chemical imaging of As^III, Cr^III and Sb^III selectively at the submillimeter scale, combined with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis. The HR-MPTS DGT exhibited selective accumulation of As^III, Sb^III and Cr^III (> 97%), yet negligible accumulation of As^V, Sb^V and Cr^VI (< 2%). Accumulation of As^III, Cr^III and Sb^III on the binding gel had a linear relationship (R² > 0.99) with the corresponding standardized laser ablation signals, proving the feasibility of LA-ICP-MS analysis. Analysis for As^III, Cr^III and Sb^III was provided with favorable analytical precision (relative standard deviation <10%). With the purpose of evaluating the dynamics of As^III, Cr^III, Sb^III and O₂ in the rooting zone, a hybrid sensor, which comprises the HR-MPTS gel overlying an O₂ planar optode, was deployed in rhizosphere sediments. Results showed that the consumption of both As^III and Sb^III due to the oxidation extended ~4.48 mm into the sediments, which was consistent with the extension length of the oxidized sediment layers around the roots created by O₂ leakage.