Preparation Of Oxygen Planar Optical Sensor And Its Application In The Sediment-water Interface Of Lake

The sediment-water interface is the most active area in the water environment,and is also an essential boundary layer for material exchanges between the overlying water and the sediment.Dissolved oxygen as the vital one of physical-chemical indicators of the sediment-water interface plays an important role in controlling the geochemical cycle of elements,sediment diagenesis processes,and evaluating the health of aquatic ecology and water environment.In this paper,we optimized the preparation method of the oxygen plane optical sensor,constructed the monitoring equipment used in laboratory and filed.Moreover,we mapped the two-dimensional spatial distribution of dissolved oxygen concentration at the sediment-water interface in the laboratory and lake by using the monitoring equipment,which can provide the date support for the management and improvement of basin water resources and water environment.The main results are as following:（1）The oxygen planar optical sensor was prepared by ultrasonic spraying had better uniformity and repeatability than the traditional knife-coating method.Good uniformity of oxygen planar optical sensor can obviously improve the accuracy.In addition,the sensor had rapid reaction time,which was approximately 6s,and the sensor had excellent reversibility,optical stability,and long-term stability.（2）We designed and constructed a monitoring equipment used in laboratory,which not only saved laboratory space and reduced interference from external light,but also improved operability through the integration of power supply,control system,excitation light source and imaging system.We studied the distributions of dissolved oxygen at the sediment-water interface disturbed by the Gammarus pulex and Limnodrilus hoffmeisteri using this equipment.Gammarus pulex as the gallery diffusors can excavate the sediment and formed the curved gallery outline burrows.The aerobic overlying water can be irrigated into borrows,which obviously increasing the heterogeneity of the spatial distribution of dissolved oxygen and changing the penetration depth and diffusion flow rate of dissolved oxygen in the sediment-water interface.Limnodrilus hoffmeisteri as upward conveyor can transport anaerobic sediments from the bottom up to the sediment surface,which leading to the formation of smog-shaped liquid and changing the oxygen penetration depth and diffusion flow at the sediment-water interface.These results unraveled that different benthic organisms could cause different effects on the distribution and dynamics of dissolved oxygen,and induced further various migration and transformation patterns of pollutants in the sediment.（3）We designed and constructed a portable monitoring equipment used in filed,and reduced volume（0.60 m×0.25 m×0.08 m）and weight（～10 kg）of the equipment by combining the area-array excitation light source and the line scan imaging system.The portable in-situ monitoring equipment had good sealing performance and pressure resistance,can be used in water with the depth is less than 30 m.The imaging performance of equipment was exanimated by aerobic-anaerobic conversion experiments in laboratory.The spatial distribution and dynamic of dissolved oxygen at the sediment-water interface can be continuously monitored using this portable equipment.Furthermore,the in-situ monitoring equipment was used to obtain the two-dimensional spatial distribution of dissolved oxygen at the sediment-water interface in the Taihu Lake.Results shown that benthic animals and aquatic plants can introduce or release dissolved oxygen into the sediment through biological irrigation and radial O₂ loss,resulting in the high heterogeneity of dissolved oxygen in sediments.