In this study, three kinds of alkaline reagents like NaHCO3 , Na2CO3 and NaOH, were added in three ways respectively to adjust pH of water samples in circulating marine aquaculture systems. Results showed that pH-jumping points of NaHCO3 , Na2CO3 and NaOH were 7. 25 ±0. 04, 7. 22 ± 0. 01 and 7. 11 ±0. 01 , respectively, according to their titration curves. The pH of water sample could be effectively improved and stabilized when NaHC03was added at the concentration of 714 mg/L. It also had better regulation effect than the other two. Among the three ways, "one-off" "four-times" "continuous" , the pH of water sample rised most gently when alkali was add in the way of continuity. To maintain pH of circulating seawater between 7. 20 to 8. 00, NaHC03 should be added in continuous way before the jumping point of (pH7. 22) , with a cycle of about 15 to 19 days.%分别采用NaHCO3、Na2CO3和NaOH 3种碱性试剂,3种添加方式调节循环海水养殖系统中水样的pH值.结果表明:从NaHCO3、Na2CO3和NaOH相应的滴定曲线确定突跃点pH值分别为7.25±0.04,7.22±0.01,7.11±0.01;发现添加714mg/L的NaHCO3可以有效提高并稳定水体的pH值,调节效果优于另两种碱试剂;"一次性"、"分四次"和"连续性"3种添加方式中,以"连续性"添加的水体pH值上升最平缓.要使循环海水的pH值维持在7.20~8.00 之间,应在突跃点pH值7.22前夕,用连续添加的方式加入NaHCO3试剂,周期约为15~19 d.
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