The Simultaneous Measurement of Phosphorus, Sulfide, and Trace Metals by Ferrihydrite/AgI/Chelex-100 DGT (Diffusive Gradients in Thin Films) Probe at Sediment/Water Interface (SWI) and Remobilization Assessment

A new type of ferrihydrite/AgI/Chelex-100 DGT (diffusive gradients in thin films) probe was developed for simultaneous determination of three kinds of pollutants with a high resolution at exactly the same location of the SWI (sediment/water interface) of Dianchi Lake. Sediment porewater profiles (DGT concentration/flux) of eight metals and labile P at the SWI were measured by DGT and an HR-ICP-MS (high-resolution inductively coupled plasma mass spectrometry) instrument with a spatial resolution of 2 mm. Based on the DGT-CID (computer imaging densitometry) technique, the S(−II) (sulfide) profile and grayscale image with a spatial resolution of 0.0423 mm were obtained. By the investigation of sediment porewater profiles of labile metals, P, and S(−II), the remobilization feature (Fe/Mn reduction and co-release of pollutants) and “internal P loading” character were identified and assessed. The assessment of the scanned AgI gel indicated microniche peak fluxes and the distribution character of sulfide microniches in sediment.