The Design And Development Of A Nitrate Automatic Analysis System In Deep Sea

Nitrate is one of the most important nutrients in ocean; the analysis of nitrate is not only better to marine ecosystem research, but also conducive to understand the marine water quality assessment. There are several methods to measure the nitrate in the ocean, but the results were not very well because some problems always existing. Such as, testing is very complex to operate and with high cost. Low stability and low precision are also the problems. Therefore, a machine to test the nitrate in the ocean without people operating and low cost, high stability and high precision is needed.The thesis synthetically used optical fiber probe technology to realize the high precision in situ UV spectrophotometric analysis in the ocean. The design work included UV light, ultraviolet spectrophotometer, data acquisition and storage control. The MSP430control panel was used in this system to automatic control the spectrophotometer, illuminant and date collection-panel. The designed prototype is complete and has the characteristics of low power consumption, miniaturization, suitable for sea in situ detection.Based on UV spectrophotometry, to make the nitrate absorb the wave length from200nm to240nm, the Gaussian filtering is used to make the photometric value curve smooth. At the same time, Minimum area model was used to absorbed wave-length’s photometric value integral processing, then get the integral characteristic value liner curve about concentration, which make the system be the high precision and linearity.Our Group and the second Marine research institute of the state oceanic administration for the prototype testing, the experimental results show that integral area of absorbance in proportion to the concentration of solution, the correlation coefficient is0.999.The system can test the low nitrate concentration of0.5μmol/L. The system is under water one month, the standard error is0.00895.When the concentration of nitrate is from0.5μmol/L to100μmol/l, the deviation between the measured value and the actual density are around1%.The above results show that the developed prototype is a complete ocean in situ nitrate automatic analysis system and has the characteristics, such as high accuracy, high stability and high accuracy, which meet the demand of nitrate detection system in deep sea.