Study on development of an ocean nutrient monitoring instrument

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Monitoring of nutrients concentrations such as nitrate and reactive phosphate is crucial to understand biogeochemical processes and their coupling with biological activities in marine environments. This project is to develop and improve a reliable nutrient monitoring instrument deployed in the ocean surface layrs. We applied photo-metric determination of nitrate after Cd-Cu column treatment and assembled in one unit frame with 100 m depth pressure tolerant, whith composed of reagents, syringe pump, Cd-Cu column, detector, battery and automatic controller. One syringe pump has multiple function, i.e., both transfer of sample water and reagents, and mixing procedure. We used 1 cm light pass for the detector, which can detect ca.0.1uM of nitrate concentration. The reagents for nitrate were chosen to be stable for 2-3 weeks continuous measurements. The sample measurement was scheduled at every 5 minutes, and obtained data is stored in a data logger. After recovery of the instrument, the data is transferred to PC.The instrument worked well in simulated field conditions and also coastal water for a week.