Abstract:

To determine the distribution and variation of pH in micro-environment of fresh water/sediment systems with the presence of bioturbation, a real-time two-dimensional pH monitoring system based on planar optode was developed, using a modified sensor foil preparation method and a modified isograms acquisition and quantification method. The system was applied to monitor the spatial and temporal distribution of pH in a simulated freshwater/sediment microcosm with the presence of bioturbation. Compared to similar existing monitoring method, there were many advantages as wide pH-sensitive range (6.2-8.6), rapid response (<30 s), high precision, and good reversibility and stability, and it could be applied in the freshwater/sediment microcosm to show the spatial and temporal distribution of pH visually. According to the system monitoring, the spatial and temporal variation of pH in the sediment was minor, but the sediment has significant effects on the pH of overlying water. Significant and dynamic changes of pH distribution pattern in overlying water were observed, which was the combined effects of several actions, and these actions were all affected by the presence of bioturbation.

Key words: planar optode, pH sensor, bioturbation, sediments, biogeochemistry