Nitrate sensor based on ultraviolet absorption spectrometry for seawater: design, comparison and application

Nitrate sensor based on ultraviolet absorption spectrometry has been developed for measurement of nitrate in seawater. Compared with the chemical laboratory analyses, no chemical regents are required when ultraviolet absorption spectrometry is applied. It is quicker, simpler and easier to perform in on-line measurement. In response to marine environment, the sensor has been designed with an electrical scraper which is used to automatically clean the optical windows before measurement and effectively reduce the influence of biofouling. The results of the comparison experiment for standard solution show that the nitrate sensor has a good performance in accuracy which the average relative error is lower than 10%, and the correlation of the nitrate sensor with laboratory method for seawater samples is higher than 0.9. The nitrate sensor has now been deployed in Bohai sea floor for long-term on-line monitoring, running stably and acquiring large quantities of nitrate data.