Study On The Determination Technology Of Nitrate In Seawater

The offshore area is now suffering more and more pollution from land thousands of kilometers of coastline in our country,red tide and other eutrophications happen frequently,and situation of typical Marine ecosystem is not optimistic.As one of the nutrients,nitrate in seawater is an essential component for the growth and reproduction of Marine plankton,the basis of Marine primary productivity and food chain,and an important parameter for Marine ecological environment monitoring.Therefore,the monitoring of nitrate in seawater is a necessary project for Marine environmental monitoring,and the analysis method of nitrate is also an important research of chemical oceanography.Nitrate is the main nutrient in seawater,the determination of nitrate content is not only the routine content of water environmental investigation and monitoring,but also of great significance to the analysis and study of the state of water ecosystem and material circulation.This paper introduces the detection method of nitrate,discusses the the container material,save reagent and hold time which influence the storage life of sample,optimizes the preservation condition and hold time,finds out the optimal storage material and temperature.On the basis of guaranting the accuracy and operability of the method through experiment to explore a complete set of nitrate field collection and preservation methods,to improve the quality of monitoring.Due to limited each batch number of lab nitrate sample analysed,and changing of nitrate content in collected water after hydrolysis,adsorption,sedimentation,microbial utilization and algae absorption effect,the actual field site investigation environment cannot meet the immediate analysis even water after filtration,biological activities in the water still consume and change the nitrate content.Therefore,it is particularly important to choose an appropriate preservation method for keeping the nitrate concentration and chemical form stable in water samples for a long time.The result of sample container material experiment shows that glass bottle is more effective than plastic bottle.But in view of the field work requirements to carry as light as possible and not easy to damage,plastic bottle is more practical than glass bottle.The results of experimental of physical and chemical parameters of the water which influence the hold time and cryopreservation time under the condition of in-20 ℃ showed that nitrate concentration changes over time in samples which stored for 20 days.Because of the complex composition of seawater,different parameters may have different influences on the concentration of nitrate samples in different directions and to different degrees.The experimental results of adding preservation reagent to seawater showed that there is no effect on the preservation of nitrate throgh adding HgCl,but adding acid or chloroform could extend the preservation period of nitrate from 3 days to 5 days.The whole process of nitrate detection is under quality control,Including the quality control of the vessels used in the sampling process and the sampling operation method;quality control of sample storage condition,storage method and transportation process;quality control of sample treatment;quality control and announcements in the sample testing process,to ensure the authenticity,effectiveness,controllability and traceability of the sample detection results,and apply the experimental conclusions to the actual monitoring of seawater nutrients.The significance to test the water nitrate in the sample of sea area in the Yangtze river estuary is comparing different nitrate detection methods which include zinc cadmium reduction and the continuous flow injection analysis through counting the experimental results,testing the technical indexes of method,from the precision,linear range,detection limit and the significant differences to analyze the advantages and disadvantages of the monitoring method,verifing that flow injection analysis can completely satisfy the seawater nitrate analysis promoting the application of automatic analysis technology.