Selective and simultaneous high resolution 2-D imaging of AsIII, CrIII and SbIII and dissolved oxygen by developing a new DGT technique comprising a hybrid sensor.

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 AsIII, CrIII and SbIII 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 AsIII, SbIII and CrIII (> 97%), yet negligible accumulation of AsV, SbV and CrVI (< 2%). Accumulation of AsIII, CrIII and SbIII 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 AsIII, CrIII and SbIII was provided with favorable analytical precision (relative standard deviation <10%). With the purpose of evaluating the dynamics of AsIII, CrIII, SbIII 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 AsIII and SbIII 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.