A novel hybrid sensor for combined imaging of dissolved oxygen and labile phosphorus flux in sediment and water

Abstract

A novel sensor assembled by a hybrid film was developed for 2D combined measurements of DO dynamic and labile P flux in sediment and water at sub-millimeter resolution based on PO and DGT techniques. The hybrid film is comprised of a transparent polyester membrane supporting two ultrathin sensing layers, i.e., a P binding layer (PBL) overlying a DO sensing layer (DSL). A robust, straightforward measuring strategy based on the referenced RGB and coloration-computer imaging densitometry (CID) methods was developed. Sensing properties for DO show a considerable homogeneity (RSD < 5%) and rapid response (<24 s) in fluorescent response. Calibration experiments reveal the sensitivity values for the DSL without/with PBL are 2.12/1.95, with an acceptable bias of less than 8%. The optimized PBL possesses a uniform distribution of zirconium-oxide microparticles at a relatively high DGT capacity (10.8 μg P cm^-2), in which the distribution of adsorbed-P can be imaged by the coloration-CID method. The performance of the sensor is compared to two conventional PO and DGT sensors. The hybrid sensor was successfully deployed in three types of benthic micro-interface and showed significant small-scale heterogeneity, providing new opportunities for advancing investigations into relevant biogeochemical processes.

Keywords: Combined imaging; DGT; DO; Hybrid sensor; Labile P flux; PO.