Abstract:

A p_CO2 plane sensing membrane based on TOA⁺PTS^4- was  developed by physical entrapping fluorescent indicator in the inner side and coverring with a permeable silicone  layer in the out side. With the aid  of camera, the sensor can directly show the variability in the distribution of p_CO2 vertical profile in water/sediment system. The planar fluorosensor was applied to a simulated water/sediment microcosm with the presence of bioturbation. The monitoring results indicate that in the presence of bioturbation, the p_CO2 in the interface of overlying water changed significantly. It goes upward and then becomes stable  gradually. Meanwhile, the diffusive boundary layer of surface sediment disappears gradually, the p_CO2 of sediment in middle layer hardly changes, and p_CO2 of sediment at depth increases to a stable level gradually. The changes of p_CO2 in this system is a complex, multidimensional change, and also a dynamic process which is producing and consuming CO₂. It is the result of the  synthetic actions including physical mixing, life activity of tubificid, organic matter mineralization and other mechanism.

Key words:  biogeochemistry, bioturbation； sediment； p_CO2 2dimensional distributions； p_CO2 planar fluorosensor