Abstract:

A new plane sensing membrane was developed in the study, and then a system was established to monitor the spatial and temporal distribution of dissolved oxygen (DO) in a simulated freshwater/sediment microcosm. Sensing foils were fabricated by physical entrapping fluorescent indicator tris(4,7
-diphenyl-1,10-phenanthroline)ruthenium dichloride in ethyl cellulose film, and the emission fluorescence intensity was decreased with the increase of the concentration of dissolved oxygen, which conforms to the SternVolmer equation of the fluorescence quenching mechanism. The sensor is precise, stable, with fast response time (<60 s) and good reversibility, and has a wide DOsensitive range (0—20 mg/L). According to the monitoring results by the system, although the temporal and spatial variation in the sediment was minor under bioturbation, the sediment has significant effects on the DO of overlying water. Complex changes of DO in the system were the result of combined effects of a variety of mechanisms such as physical mixing and redox. And these effects were all affected by bioturbation.

Key words: bioturbation, planar optode, DO sensor, sediment, biogeochemistry