The Development Of Measuring Instrument Of Total Phosphorus And Total Nitrogen For Marine Station Ecological Environment Long-term Comprehensive Observation System

This paper aims at the study of total phosphorus and total nitrogen automatic monitoring in Marine station.Research in 863 plans to ship ocean ecological environment monitoring technology system subtasks seawater of total phosphorus and total nitrogen detector,total phosphorus,total nitrogen in the development of sea water of shipborne on-site monitoring apparatus as the foundation,hardware and structure of the instrument were reassembled and assembled on the basis of the original shipborne automatic monitor.Redesign of the total phosphorus total nitrogen determination apparatus,such as,microwave-ultraviolet joint digestion system replaced by microwave digestion,sample flow part increasing the evaporator cooling device,cadmium column repositioned,software control system increasing the"question and answer"program,using quartz flow cuvette.The volume of the instrument was reduced,so that it eventually reached the size of 500 mm×500 mm×600 mm.The total nitrogen and total phosphorus in seawater was determined by using microwave and ultraviolet spectrophotometry.Total phosphorus and total nitrogen were determined continuously by controlling program in the coastal area.Effects of experimental conditions have been optimized.Eventually,study chooses comprehensive digestion temperature 135℃,digestion time for 27 minutes.Total phosphorus and total nitrogen were determined when the peristaltic pump speed at 20r·min^-1 and 50 r·min^-1 respectively.Cadmium column packing length is 7 cm.Study chooses 25 g·L^-1 ammonium molybdate concentration and sulfuric acid volume 300 m L（1+6）as P_A chromogenic agent,chooses 20 g·L^-1anhydrous sodium sulfate、0.4 g·L^-1antimony potassium tartrate and 30 g·L^-1 ascorbic acid concentration as P_B chromogenic agent.The concentration of N_A colorant was made up of 300 m L（1+5）hydrochloric acid and 6.00 g·L^-1 p-aminobenzenesulfonic acid.The concentration of N_B colorant was 4.00g·L^-1 N-1-naphthene hydrochloride.Under the optimal conditions,TP concentration displays linear relationship in the range of 0.003～5 mg·L^-1,y=0.038x+0.003,correlation coefficient r=0.997;TN concentration displays linear relationship in the range of 0.007～10 mg·L^-1,y=0.185x+0.043,correlation coefficient r=0.999.Linear relationship is good.Total phosphorus and total nitrogen standard sample inspection,the relative standard deviation（RSD）within±3%and±4%respectively;The rate of recovery of total phosphorus and total nitrogen of seawater samples is between 98%～100%and 97%～100%respectively.The zero drift and range drift rate are less than±1%and±5%.The determination results agree well with those obtained by the Specification for automated water quality moniting in coastal area（HJ731-2014）.the actual water samples with national standard method of measurement resultsthere was no significant difference.The determination results agree with those obtained by the National standard method.The monitoring and installation of Marine monitoring stations in Wheat Island can realize automatic on-line monitoring of the instrument.