ABSTRACT
In this study, we combined diffusive gradients in thin films (DGT) with planar optode (PO), a two-dimensional (2D) in situ chemical techniques for investigating the geochemical behaviors of arsenic in rice rhizosphere soil and bulk soil at high spatial resolution (sub-mm). We had observed three distinctive regions in rice rhizosphere: soil-water interfaces (SWI, O+), rhizosphere aerobic soils (O+) and bulk anaerobic soils (O-). The mobility of arsenic and other elements is greater in rhizosphere than bulk zone, flux maxima for As, Fe, P, Pb had also been observed around root tips. Our results indicate rice rhizosphere is a special unit to gather oxygen and affect metals mobility, both flux maxima for metals and radial oxygen loss from root tips are common existed in rice rhizosphere. We have provided new evidence for the importance of rhizosphere oxidation and coupled diffusion in modulating arsenic mobilization and dispersion, showing microniches are important geochemical phenomena exploited by rice plants to acquire metals or nutrients.
