Analytical chemical study on the dissolved organic nitrogen and dissolved organic phophorus in sea water Yuzuru NAKAGUCHI,* Shoko ARAKI, Yoshitaka YAMAGUCHI and Takashi NISHIMURA Research Institute for Science and Technology, Kinki University, Kowakae, Higashi-Osaka 577-8502, Japan (Received, December 6, 2004) Abstract To elucidate detail distribution of dissolved organic nitrogen (DON) and dissolved organic phosphorus (DOP) in the ocean, simultaneous decomposition method of DON and DOP was investgated. Sodium tetraborate decahydrate (Na2B407) and potassium peroxodisulfate (K2S208) were used as a oxidizing regent for the decomposition of DON and DOP. The concentration of K2S208, the removal of chlorine gas, decomposition temperature and time, the ratio of Na2B407/K2S208 to sample solution were investigated. The recommended decomposition procedure was established. The recommended procedure was applied to the determination of DON and DOP in seawater samples which were collected from the eastern North Pacific. Key words: Dissolved organic nitrogen, dissolved organic phosphorus, decomposition, nutrients, North Pacific
'; 35.0 ml.)7q;_tzfc-`1000 mlb't41.l ) 100 m1b:1-l-7 )'^: 0.55 g ua_.t%l, 15%SLS7h2ml i)7paat,1`.o Alkt:iVfli../LN*(d, --4---f A- >3"-dAv=i-ti), ---0-)iMfEFILLtD0) H*'J t 7 VA 7h3 c N. Milli- Q-SP-TOC Water Reagent System r'k.. ti O )=11 L 10 1D Fig. 1. Sampling Locations
Table 1 Recovery of nitrogen and phosphorus with the Raimbault's decomnosition nrocedure. DON and DOP standard solution Cocarboxylase as DON100.4 Recovery (%) Purified water LNSW* 101.0 Cocarboxylase as DOP19.0 -D-Glucose-l-phosphate salt hydrate as DOP95.6 *LNSW:Low nutrient sea water disodium 15.6 80.3 Fig.2 Concentration of potassium peroxdisulfate (M) Effect of of potassium peroxdisulfate concentration on the recovery of nitrogen and phosphorus in purifed water. U Cocarboxylase a -D-Glucose-I-phosphate disodium salt hydrate
Fig.3 U.U4 V.UO U. 1 L U.1U Concentration as potassium peroxdisulfate (M) Effect of addition volume of oxydation reagent on the recovery of nitrogen and phophorus in low nutrientsea water. T Cocarboxylase a -D-Glucose-1-phosphate disodium salt hydrate Table 2 Effect of bubbling time of high purity air on the recovery of nitrogen and phosphorus in low nutrient sea water. DON and DOP standard solutionbubbking time (min.) 0 5 10 15 Cocarboxylase Cocarboxvlase as DON as DOP 83.6 82.7 94.9 79.0 97.0 81.0 98.0 79.8 unit:%
Time (hour) Fig. 4 Effeect of heating temperature and time on the recovery of nitrogen and phosphorus in low nutrientsea water. Concentration ofna2b4o7 (M) Fig. 5 Effect of Na2B407/K2S208 ratio on the recovery of nitrogen and phosphorus in low nutrient sea water _ K2S208:0.167M ^ K2S208: 0.130M 1111 150 C 180 C 0 120 C K2S208: 0.093M K2 S208 : 0.056M
c -; a.) E 0 Concentration of Na2B407(M) Fig. 6 Effect of Na2B407/K2S208 ratio on the ph value after decompsition. CL) b cd 0 U K 2S20g: 0.167M K 2S20g: 0.130M --^ K 2S208: 0.093M r-. ---* K2S20g: 0.056M Fig.7 Effect of ph on the colar development of nitrogen and phophorus Nitrogen I, Phosphorus
Table 3 Components of oxdizing reagent Added(g/100m1) Solution Na2B4O7 10H2O K2S2O8 a b c d 6.00 6.74 7.99 10.50 5.00 5.63 6.67 8.75 Fig. 2 3 4 5 Addition volume of oxdizing reagent (ml) 8 Effect of addition volume of oxidizing reagent on the recovery of nitrogen and phophorus -- Nitrogen Phosphorus Table 4 Recovery of nitrogen and phosphorus of some DON and DOP reagents decomposed by the recommended Procedure. ReagentRecovery(%) DON DOP Urea EDTA ATP Cocalboxvlase ATP Cocalboxylase a -D-Glucose-1-phosphate disodium salt hydrate as DOP 106.1 111.4 108.2 102.2 111.8 103.9 103.1 S.D.(n=5) 2.8 1.4 2.3 3 1.3 1.8 2.1 Fig. 9 Vertical profiles of DOC, DON and DOP vat pies c fleeted from the North Pacific Ocean on the KH00-3 cruise ^ BO-I B0-5
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