pH及无机氮化合物对小浮萍生长的影响

利用浮萍科植物吸收转化污水中的无机氮磷正在成为水处理研究的热点.本研究以我国常见的小浮萍(Lemna minor L.)为研究对象,在完全培养液的基础上模拟生活污水的NH₄⁺-N、NO₃^--N浓度和pH范围,研究了培养条件对小浮萍生长的影响.结果表明,低pH对小浮萍的生长具有抑制作用,小浮萍对pH耐受的低限在5～6之间,在6～9的pH范围内,能够正常生长.水中非离子态的NH3和NH+4都会对小浮萍的生长产生抑制作用,前者的抑制作用更明显.在NN₄⁺-N为唯一氮源的条件下,非离子态的NH₃浓度大于0.2mg/L时就会对小浮萍的生长产生明显的抑制作用,大于2mg/L时,小浮萍基本上不能生长.NO₃^-在本研究的浓度范围内对小浮萍的生长没有影响,NH₄⁺-N和NO₃^--N浓度的增加可使小浮萍的鲜叶片的叶绿素含量增加,另外在相同氮的浓度下,由于生长受抑制,NH₄⁺-N中生长的小浮萍过氧化物酶活性高于NO₃^--N中的活性.

Effect of Inorganic Nitrogen Compounds and pH on the Growth of Duckweed

The use of duckweed in domestic wastewater treatment was paied increasing attention recently. But inorganic nitrogen compounds and pH of wastewater possibly affect the growth of duckweed. The effect of ammonia, nitrate and pH on the growth of Lemna minor L., a common spiece in China, was assessed with laboratory scale experiments. The experiments used artificial culture with different levels of pH, ammonia and nitrate concentrations. The experimental results indicated that the lowest value of pH Lemna minor can tolerate was between 5-6, and it can grow well in pH from 6 to 9. The growth rate of Lemna minor was inhibited gradually with increasing concentration of ammonia. The toxicity of ammonia was a result of both forms, NH3 and NH4+. Compared to NH4+, the effect of NH3 was much stronger. Nitrate had few inhibitory on the growth of Lemna minor. The increase in ammonia and nitrate concentrations can increase the chloropyll content of Lemna minor. Activity of peroxidase of Lemna minor in ammonia culture was higher than that in nitrate culture because of the toxicity of ammonia.